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Posted by: Waspie_Dwarf Nov 7 2005, 07:19 PM

The press secretary of the Russian Federal Space Agency, Vyacheslav Davidenko, has said that Russia will design and launch a long-living probe to Venus by 2015. The probe is known as Venera-D.

Davidenko told a news briefing that within the federal Space budget for 2006-2015 was envisaged, “work to develop a principally new spacecraft, Venera D, intended for detailed studies of the atmosphere and surface of Venus”.

“It is expected that the craft with a long, more than one month period of active existence will land on the surface of the planet that is the nearest to the earth. Nobody has done such thing on Venus so far.”

Source: http://www.itar-tass.com/eng/level2.html?NewsID=2599096&PageNum=2

Posted by: Toma B Nov 7 2005, 07:27 PM

Should be good...
Maybe little wheels on that lander...

Posted by: ElkGroveDan Nov 7 2005, 08:08 PM

The Russian space program really needs some PR and marketing people.

Posted by: Waspie_Dwarf Nov 7 2005, 08:15 PM

And NASA and ESA don't? Mars Reconnaissance Orbiter and Venus Express are hardly inspiring names for spacecraft.

Posted by: JRehling Nov 7 2005, 08:24 PM

No word on the thermal strategy: Build a spacecraft that can withstand the heat. Or, use refrigeration to keep the probe cool. Or some combination of both. A probe that was built to withstand the heat might well last indefinitely, much longer than a month.

Would this be the first Soviet/Russian spacecraft to use an RTG? I think they have been able to rely upon batteries and solar panels thus far.

The next question is what a long-lived probe's long life would be for. Data on wind/temperature/pressure variations would be interesting, but may turn out to be boringly constant. It's possible that wind would blow some dust around, but that's no guarantee. Skyward looking cameras could show variation in cloud structure blowing overhead. One baseline instrument that seems to me to provide a clear need for life beyond an hour would be a seismograph, which is of diminished value without a long life span. Additionally, if there is a sampling/instrument arm, then arbitrarily long mission durations could yield the benefit of more sampling, especially with irradiative spectrometers that require long integration times. Maybe a long, double-jointed arm could scan a grid around the lander, moving a small suite of MER-like instruments carefully around the base. It would then be essential to keep the arm's movements from interfering with the seismometer.

Posted by: Waspie_Dwarf Nov 7 2005, 08:35 PM

Russian spy satellites have employed minature nuclear reactors (although not RTGs I beleive). They have lead to problems. In 1978 Cosmos 954 crashed in Northern Canada spreading radioactive material over a large area.

Posted by: tty Nov 7 2005, 08:57 PM

The Soviet Union certainly developed RTG's which were used for powering e. g. lighthouses in remote locations. Incidentally at least some were insufficiently shielded and so could be dangerous to approach for the unwary.

tty

Posted by: ljk4-1 Nov 7 2005, 08:59 PM

Of course anyone on the surface of Venus will have bigger things to concern themselves with than encountering an RTG or two.

Posted by: tedstryk Nov 7 2005, 10:25 PM

I know there were some RTG's that were sent to Peru or thereabouts on Mars'96.

Posted by: Stephen Nov 8 2005, 01:17 AM

They could always hold a competition. Then they might get to select such inspiring names as "Spirit" and "Opportunity".

=====
Stephen

Posted by: BruceMoomaw Nov 8 2005, 01:54 AM

On the way back from the COMPLEX meeting, I attended the afternoon half of the day-long first meeting of VEXAG -- the Venus Exploration Analysis Group, which is the new equivalent of MEPAG and OPAG. There was very little news -- except for the revelation that one of VEXAG's subgroups is currently engaged in a detailed prioritization of the goals of Venusian surface science and the technical difficulty of achieving them, which I hope to get hold of in two weeks or so. But one thing that the Group made clear is that building a long-lived Venusian lander is still going to be bloody hard. You need either a VERY high-powered cooling unit (probably mechanically powered by the waste heat from an RTG), or electronics capable of enduring Venusian temperatures -- or both. (Right now we have experimental electronics capable of enduring 250 deg C. We need 200 degrees above that.) So I think this new Russian news is just more empty whoosh from a nation desperately trying to put up any kind of fake front that it can to say that it's still capable of large-scale space exploration.

What we DON'T need -- as I had suspected earlier -- is wheels (contrary to what the Solar System Strategic Roadmap group had said). As Doug Mackwell said, by precision control of the buoyancy of a Venus lander -- which is more like controlling the buoyancy of a submarine than that of a balloon -- "you can glide along two meters, or 20 meters, above the surface."

Posted by: Waspie_Dwarf Nov 8 2005, 02:03 AM

Whilst you are no doubt correct about how difficult this long-lived goal will be to achieve the Russians have given themselves a decade to achieve this.

"Empty whoosh" possibly, but I hope not. Russia has surprised the west many times by achieving things that seemed improbable with the resources they have to hand. I would never rule them out.

Posted by: Tom Ames Nov 8 2005, 03:10 AM

"Venera-D" does sound a lot like it belongs up the isle from Preparation-H.

Posted by: mchan Nov 8 2005, 03:59 AM

Er, it may be an American thing, but Venera-D sounds like an abbreviated form of an old term for STD's. ElkGroveDan was polite to not put it so bluntly.

Posted by: ilbasso Nov 8 2005, 04:14 AM

Have the Russians attempted any interplanetary probes since 1996? Do they have any other ones already in development now? I know they are strapped for cash but it's hard to believe it will have been 20 years between their last and next interplanetary attempts.

Posted by: Myran Nov 8 2005, 05:28 AM

The name (that really should need to be something different than 'V.D') suggest its one upgrade of one kind of other of he Venera series of landers.
If so the Russians might have decided to do something they feel they have confidence in pulling off.
ilbasso: You might be right, im not aware of any other since Mars96.

Posted by: dvandorn Nov 8 2005, 07:15 AM

Reminds me of the big marketing disaster Chevrolet faced when they tried to sell the Nova in Spanish-speaking countries. In Spanish, of course, "va" is a form of the verb of action, roughly translated as "go." And "no" is a rather universal form of negation. So, "no-va" in Spanish is pidgin for "doesn't go."

And, of course, then there's the marketing of Coca-Cola in China, where the sound-alike ideographs first used to represent the brand name translated literally to "bite the wax tadpole."

-the other Doug

Posted by: Bill Harris Nov 8 2005, 09:55 AM

Whew, how would refrigeration (or RTGs) be workable? Those work on temperature differentials, and how would one transfer heat into an 800 degree environment? And under enormous pressure. I'm thinking that some form of evaporative cooling might be the only feasible process.

Don't undersell the Russians. For years, they've been very successful with achieving miracles with old "soviet" technology, in many ways more so that the USA's "space winnebago" misdirection.

--Bill


PS: let's see how this transliterates: Венера-Д is Cyrillic for Venera-D and looks less-threatening.

The Russians can really be a hoot sometimes. I googled this:

Russian marriage agency "Venera" is an international introduction service located in Ufa, Bashkiria.

Posted by: tedstryk Nov 8 2005, 10:40 AM

They do have Phobos-Grunt under development for a 2009 Phobos sample return, and also a large Mars lander, although the latter has few specifics released. I doubt Venera-D will actually be its name. I think its a reference to Venera 1-3 (Venera 8) Venera 4-8 (V- Venera 9-16 and the Vegas (Venera -C). That sequence may be a little off, in terms of what number goes where, but I do know that it is where the "D" comes from.

Posted by: Waspie_Dwarf Nov 8 2005, 01:30 PM

Surely an evaporative system would contaminate the local environment, rather negating the point of operating on the surface for a month.

If the name Venera (which is Russian for Venus) is going to cause so much hilarity, heaven help us if NASA anounce they are going to send a probe to Uranus.

Posted by: Adam Nov 8 2005, 02:34 PM

I have already seen this, at the ESA site i believe. I'm serious. I promise.

Posted by: ljk4-1 Nov 8 2005, 02:41 PM

Carl Sagan tried to get references to Venus renamed Cytherian, but his Harvard colleagues in the 1960s felt otherwise on the matter. I think Cytheria has a definite romantic sound to it.

For those who recall the Voyager 2 mission to Uranus in 1986, the planet's name kept getting pronounced differently (with a lower case a) by the media as the probe got closer.

One hopes that a world will not be ignored by science just because its name may sound funny to the public.

Posted by: BruceMoomaw Nov 8 2005, 02:53 PM

Originally Gordon Chin's Discovery proposal for a "VESPER" Venus orbiter -- which made the finalist list once, and which he's proposing again this time) was named "Venus 2000". I tried to look it up on Google under that name once and was deluged with ads for sex toys. It is probably not coincidence that shortly thereafter it was renamed "VESPER".

As for "Uranus" -- that unfortunate planet whose name sounds obscene no matter how you pronounce it -- Kingsley Amis notes that back in 1961 there was a Swedish movie called "Voyage to the Seventh Planet", in which the actors kept referring to it as "U-rah-nus".

Posted by: BruceMoomaw Nov 8 2005, 02:56 PM

Meanwhile, Uranus don't seem to get no respect at the moment from the planetary science community itself, apparently because they think of it as a Grade-B Neptune, which is unfair. A few years ago, at a meeting of the Decadal Science discussion group, one guy was about to present a talk on Uranus exploration when Reta Beebe (who, by the way, has a spectacularly foul mouth) snapped, "You mean you're actually going to make a case for exploring that boring planet and its scrawny little moons?"

Posted by: um3k Nov 8 2005, 03:44 PM

I've seen it there, too. It was quite a while ago.

Posted by: elakdawalla Nov 8 2005, 03:52 PM

When I had to teach a fifth grade classroom about Uranus I let them all have a good laugh at me (and them) pronouncing it "Your Anus" and "Urine Us" and then I wrote the following on the board: "You're a Nuss!" and had them all turn to each other and accuse each other of being Nusses. After a brief bit of speculation on what a Nuss could possibly be we moved on and the fifth graders were able to handle talking about Uranus. Unfortunately my husband still can't handle it. Every time I tell him about a new mission to some place he asks "But when are they going to send a mission to Uranus?" and then cracks up. Sigh. I get no respect. Anyway, in the spirit of "any publicity is good publicity" I expect that if a mission ever gets on the books for Uranus its unfortunate name can only help; it will be the best-known space mission among people who listen to shock jocks, watch Jon Stewart for their primary source of news, etc. Howard Stern won't be able to stop talking about it.

--Emily

Posted by: Adam Nov 8 2005, 04:18 PM

I remember seeing other missions as well. What were they?

Posted by: ljk4-1 Nov 8 2005, 04:19 PM

You can also blame the 1982 film E.T. for the unfortunate name association.

Speilberg threw in one of the minor characters making jokes on the planet name in order to get a PG rating; that act seemed to have created an unfortunate awareness among the public.

Perhaps we should have stayed with Herschel's original suggestion of naming it after King George III.

Posted by: tedstryk Nov 8 2005, 04:22 PM

Yes, NASA announcing that it wants to probe Uranus would be great fodder for Leno and Letterman.

Posted by: ljk4-1 Nov 8 2005, 04:22 PM

While I have no illusions regarding the complexity this would add to such a mission, perhaps the lander could be attached to a balloon that would periodically rise into the cooler heights, then settle down somewhere else for a while. Perhaps a lack of longevity can be made up for in visiting more places on Venus.

Posted by: TheChemist Nov 8 2005, 04:34 PM

Well, that's the price we pay for using a greek word in its latinized version. The original greek word for this god is pronounced <Uranos> (U like in "put", A like in "cat").
Nothing obscene about that and in modern greek it is translated as <the sky>.

Posted by: elakdawalla Nov 8 2005, 04:40 PM

I've always been curious, what domestic uses could there be for the technologies needed to explore Venus's surface -- high temperature and pressure? I don't think scientific needs (like exploring deep-sea volcanoes) count. Is there a need in, say, manufacturing or something for robotics, electronics, and sensors that can operate at Venusian temperatures and pressures? I think that support of the development of the rovers was probably aided by the obvious military uses that you could put smart, autonomous rovers to -- it always helps to be able to demonstrate down-to-earth uses for expensive NASA technologies.

By the way you don't necessarily need to get to the high temperatures that the Venera landers encountered. David Crisp kept pointing out at the VEXAG meeting that you could land in the crater Cleopatra (which is at quite high altitude) and find significantly lower ambient temperature and potentially learn a lot about Venus, namely how the heck a planet that hot can support a topographic feature as high as Maxwell Montes.

--Emily

Posted by: JRehling Nov 8 2005, 04:54 PM

That is a reasonable mission, although a very different one, and it wouldn't help out the seismological goals.

Actually, if a seismometer were the *only* instrument that one cared to preserve, I think it could simplify things a great deal. A seismometer actually involves no parts that aren't easy to make withstand 900F. The trouble would be preserving the electronics that collect and transmit the data, but that has the prospect of being a much smaller unit to refrigerate. One approach could be to drop a lander that has many instruments, with refrigeration available for the central electronics only. Then let all of the instruments but the hardy one die after they've taken initial measurements. The bulk of the science of a surface imager on a static lander comes from the first 360 panorama.

I wonder if another instrument that might be easy to design for thermo-durability would be an alpha-particle spectrometer, if the durable radioactive sources and detectors could be placed in the head, and the sensitive electronics stashed far away inside the safe cooled space within the lander. If so, an arm that swung one of those around, holding it over various loci in the vicinity of the lander could take a few days intregrating data at the slow pace it needs and generating a coarse elemental composition "map" that could be registered with the visual panorama.

I think one approach to the difficulties of Venus is going to be to begin from basics and use "analog" approaches when it turns out that our fancy microelectronics won't work. Of course, that ends up being a lot of R&D, running up mission cost. But R&D in Russia ought to be cheaper than basic R&D in US/W. Europe.

Posted by: mcaplinger Nov 8 2005, 05:01 PM

The pressure isn't as much a problem as the temperature. There are probably a lot of industrial uses for high-temp electronics -- jet-engine controllers, for example. When we were writing our Venus probe proposal (which I like to call "Tom Swift and His Nuclear Refrigerator" -- see http://www.msss.com/venus/vgnp/vgnp.txt.html ) there was a lot of work being done on silicon carbide (SiC) electronics for engine control. Haven't looked lately; it wasn't really viable in the mid-90s.

Posted by: The Messenger Nov 8 2005, 05:20 PM

Once smart sensor technology is well developed and robust enough for exploring Venus, there will be (there already is) a hungry market. Start with oil exploration: If cheap, reliable, lightweight, small, integrated sensors tracked tooling and shaft temperatures, shear, loads, spectrographic profiles and strain, engineers could develop more profitable and safer drilling profiles. Now look at mining, automobile and diesel engines, HVAC systems and smart, integrate home energy management systems.

Chemical industrial environments, petroleum cracking columns, jet engine fatigue sensors. Pottery, metal fabrication, waste reclaimation - the list of hostile manufacturing environments is extensive.

The real question is not what, but why haven't these advanced technologies already emerged? I guess the best answer is that they are emerging, but a better-funded space technology research program could have, and still should accelerate advances in energy and resource mangement.

Posted by: elakdawalla Nov 8 2005, 05:43 PM

Another problem with a seismometer that they discussed a lot at VEXAG was that it needs to be "intimately connected" with the surface -- essentially it needs to be bolted to bedrock. It's not quite as simple as landing the device on the surface. Also, nobody really knows how long you would need one seismometer to operate in order to pick up anything useful -- a day? a week? a month? a year? -- there were also discussions at VEXAG that it may be possible to get a handle on that question by doing seismometry of the atmosphere.

I sure hope I see a seismic network on both Mars and Venus in my lifetime. We are so blind to what is going on underneath the skins of those two planets.

--Emily

Posted by: BruceMoomaw Nov 8 2005, 05:59 PM

I remember Malin's "nuclear refrigerator" very well -- fully 97% of its RTG's electrical power would have been utilized just to keep itself cool! As one guy at COMPLEX pointed out, though, seismometry is likely to be one of the hardest things to do at Venus even with a long-lived lander -- because of the racket from the cooling unit that such a lander will need.

As for John Rehling's suggestion for an alpha-scatter spectrometer, even the sensors for it can't stand up to such temperatures -- and in any case the air density at Venus is so high that it interferes disastrously with the ability of alpha particles to reach the sample, so it's always been considered hopelessly impractical unless you take the sample inside. There was a suggestion back in 1978 that it might be possible to develop in-situ sensors for a Venusian X-ray spectrometer, but I haven't heard anything about it since. But I think the element analysis problem has been solved in any case -- you just use a LIBS (Laser-Induced Breakdown Spectrometer), which is scheduled to fly on MSL and which has enormous advantages even on an airless world. It can analyze a sample in a fraction of a second, at a range of a dozen meters or more, with even more sensitivity than an hours-long measurement by an alpha-scatter or X-ray spectrometer -- and a test reported at the 2004 LPSC has already shown that it will work perfectly well on Venus, eliminating the need to take the sample inside the craft through an airlock.

The big problem is how you do mineralogy. An X-ray diffractometer or a Mossbauer spectrometer require ingesting the sample, and the latter at least also requires hours-long measurements. But -- besides near-IR spectroscopy -- a Raman spectrometer may solve a lot of the problem; it too can make a long-distance analysis in a fraction of a second using a laser, and in fact an instrument has already been tested that can combine it with the LIBS. Since a Raman must detect a very faint scattered-light signal, it's possible that Venus' thick air might interfere with it at long range, but you could still do it on the immediate surface using a fiber-optics head on an arm.

However, the one thing a Raman can't do well is iron mineralogy -- that requires a Mossbauer, unless near-IR spectrometry can do it well enough (which might be the case).

As for that balloon that repeatedly lands briefly and then takes off for the clouds again to cool off, JPL has been working on the design for just such a mission for years (the "Venus Geoscience Aerobot"), and Martha Gilmore has a long article on it in an issue of "Acta Astronautica" early this year. It would use a so-called "variable-buoyancy aerobot" -- using a mixture of helium and some substance like water that condenses from vapor into liquid at high altitudes -- to carry out such repeated dives without using up either gas or power, kind of like those "drinking ducks". (Such dives can be done in a controlled way if the plumbing on the liquid tank has controlled valves.) The main problem seems to be finding a plastic for the thin balloon envelope that can stand up properly to Venus' savage surface heat; polybenzoxasole is the one usually mentioned, but Victor Kerzhanovich expressed doubts in an LPSC abstract this year that it can be properly seamed. However, he's recently told me in an E-mail that he thinks this may be possible after all.

Posted by: Richard Trigaux Nov 8 2005, 06:45 PM

THE TECHNOLOGICAL CHALLENGE OF A LONG LIVED VENUSIAN LANDER

First of all, as many already pointed in this thread, a baloon is much better than an lander on Venus: with much higher pressure, the air is very dense and the same baloon can wear maybe 20 times more weight. The overal thing may look something between a submarine and a zeppelin, with a rigid skin and balast compartments. The easiest way to inflate it is with water steam, it is one of the lightest gaz (except helium or hydrogen) and it would be relatively easy to get in Venus air. Neon would work too, while being less corrosive.

Refrigeration or heat withstanding? I think refrigeration would be feasible for only a very small volume, or for a short time, thus offering little possibilities (or frustrating results like with Huygens). The reason is that the efficiency of refrigeration decreases very fast with the difference of tempereature. In a home regrigerator, the difference is 20-30K over 300K (10%) on Venus it would be 450K over 750K (60%) thus requiring much more energy. So I think that WE MUST THINK FROM HE BEGINNING TO 100% 450°C withstanding probe. This is the problem.

Corrosive air. Venus air is not only very hot, but it contains gasses which, at this temperature, react very vigorously to produce oxygen, sulphur and sulphuric acid, perhaps other acids. This is a problem, and every sensitive parts of a probe (electronic boxes, instruments, motors) will need tight seals.

Structural Materials They will have to withstand heat, but also corrosive air (acid, oxydizing, sulphurizing). Common materials like steel and aluminium alloys are ruled out at once, and even titanium (a steel sructure would burn in only several hours). We must from the very start think at precious metals, special alloys used in aeronautics turbines or nuclear plants, or even ceramics, composite ceramics, etc. Possible but need some development (including a "venusian test chamber").

semiconductors for computers, power control and radio emitters are perhaps the domain where a solution seems the less possible. But there are perhaps hundreds of couples of semiconductor materials, and many common materials become semiconductor at higher temperature, so it would be a really bad luck if we do not find one working at 460°C (perhaps diamond do this). This is a matter of research and development, which can go astray with bad solution for years, or we can be lucky to find a good material quickly. Few researches were done in this domain, as, on Earth, there is alway a mean to offset the electronic in a protected environment. But we do not need the highest performances in a venusian lander.
If really we find no semiconductors living at 460°C, we could go back to... vacuum tubes. Micro-sized, simplified technology with flat electrodes triodes, built with the technologies used for integrated circuits, may have electrical properties undiscernible from a N channel MOSFET transistor, which with we could make computers, power "transistors", etc. And, at 460°, it would need no heater... Here, the question is not to find some elusive material, but to test once if it works or not. The only serious problem I see with those triodes would be that, the anode being as hot as the cathode, it should be made from a much less electropositive metal than the cathode.
Another alternative would be static-electricity actuated micro-relays, which, at sub-micronic size, would be fast enough to build computers. And work with a very wide range of temperature... We could probe lava lakes with this electronics.


Electricity conducting materials pose a problem, as their quality much lowers with temperature. Of the three best metals, aluminium is ruled out, remain silver and copper. Silver is better on Earth, on Venus I do not know, but it may be used exclusivelly for wiring. This arises special problems with power transformers.

For insulators plastics are widely used, as they have two magical properties: when we bend an electrical wire, plastic does not break, and it does not change thickness as a soft material would do. On Venus kapton and even Teflon are out. Remains things such as fiber glass guipures impregnated with some soft mixt. (In ancient times silk guipures were used as insulator in power transformers and turbomachines, while paper ribbons were the rule in telephone cables).

Magnetic materials used in power transformers and motors arise a special cconcern, as at 460° most magnetic materials have degraded quality, if they do not have reached their Curie point (where magnetic properties disappear completelly). Things are still worsened if we consider that all these machines work at at temperature which can be 100°C more than their environment, and this is worsened by degraded electrical and magnetic properties. May be some special alloys or rare earths may still have some interesting efficiency, I do not know. Anyway transformers windings and motor windings would need special techniques, working at higher frequency, or at resonnance (which would require a very precise winding of thin ribbons), and cooling from inside (at least a circulation of fluid to bring it back at ambient temperature).
The alternatives to electromachines are piezoelectric crystals or pneumatic actuators. Piezo crystals can work at high temperature, and a design with a U-shaped crystal oscillating around a shaft may replace an electrical motor.

Lubricants also are a problem. When we think at a lubricant, it is nearby alway to oil, understand an hydrocarbon. No hope for anything such on Venus, the only stable hydrocarbon is methane, and it is not really oily... But basically a lubricant is a liquid which 1) sticks on the parts to lubricate 2) has relatively low fluidity 3)is stable enough (not an emulsion, not solidificate or evaporate) so that it forms a layer between the parts, preventing them from the devastative metal-to-metal contact. Many fluids can do, liquid metals or minerals, eventually mixtures to ensure the right properties. Solid lubricants like graphite or molybdene sulphide can also do, but I do not believe very much o such solution for a long lived mechanism. Once the solid lubricant is gone, it is gone, while a liquid lubricant is alway pumped back to the right place.

Etancheity must be achieved thoroughly, not only from dust, but also from corrosive gasses. Tightness around rotating shafts or parts is usually achieved with elastic materials, but nothing such may exist at 460°. Tight tolerance and wetting the joint with a liquid metal would do the trick, together with a chemical control of the inner atmosphere of the probe.



Energy is perhaps the biggest problem. There is little solar energy on Venus, and no wind, rivers etc. (perhaps some thermics could be used for navigation). A RTG would not be at ease: the thermocouple semiconductors are limited to 300°C. Only thermoionic generators could work.
It exist on Earth generators made of a source of heat (fire) and infrared-sensitive photovoltaic cells. Could some photovoltaic cells be able to harness the abundant infrared emitted by venusian rocks, while being themselves at the same temperature? Why not, you will say. Except that this would violate the second principe of thermodynamics: a one source thermal engine... I wait for explanations of this... or for experiment.



Where to go??? Once visited the basic lava flows of Venus, we shall have many overal explanations of the hystory, structure and compsition of Venus. But after?
My idea is as follows: Venus may have experienced a stage with an Earth-like climate, with water, ocean and plate techtonics. Until the greenhouse effect increases itself and trips out to reach the today conditions. If this is true, the mountain ranges of Venus would be in fact continents (which would maintain their alitude by isostasis, floating on the unerlying basalt mantle, this explaining why they do not collapse witht he high temperature softening the rocks). Maybe the oceans and continents of Venus evolved for two billion years (infered from the increase of Earth continents).
But if so, LIFE HAD GOOD CONDITIONS AND PLENTY OF TIME TO APPEAR ON VENUS. Of course it hopelessly disappeared since, witht the increase of temperature. This increase also destroyed limestone rocks and any trace of coal or oil near the surface. So only very few would remain today.
So the idea is of an aerobot exploring the mountains (cooler places) for years, hovering along the many cliffs and examinating them closely mith a microscopic imager in search of... fossils. Microscopic fossils, but fossils anyway. Large animals? civilization? I don't hope so much, but who knows. At least with what we know of Mars now, we have more chances on Venus.

Sorry for the long post, but it was worth writing it I think.

Posted by: David Nov 8 2005, 07:12 PM

Before the word became exclusively associated with STDs (as a euphemism), "venereal" would also have had "romantic" associations. Hopefully we won't hear about "cytherean diseases" any time soon.

It should be Cytherea (sith-uh-REE-uh) and Cytherean (sith-uh-REE-un), not Cytheria (sith-EE-ree-uh).



As a matter of fact, the pronunciation "yoo-RAY-nuss" is erroneous, as in Latin the stress is on the first syllable: "YOO-ruh-nuss". The adjectival form is, however, still Uranian (yoo-RAY-nee-un), which may be in part the source of the confusion.

On the question of how worthwhile it would be to explore the Uranian system -- If I were entitled to have any opinion on the matter at all, I'd think it was remarkably silly to downgrade any of the major planets as "boring". Certainly a planet that's tipped all the way over relative to its orbit is intrinsically interesting. And if Voyager II found nothing particularly fascinating about Uranus' system of icy moons, that is more likely a reflection of the very brief and cursory opportunities it had to examine them. Pretty much every place in the Solar System reveals some strange and unexpected qualities on closer examination. Places as previously dull-seeming as Enceladus and Dione reveal themselves to have remarkable characteristics. I have no doubt but that Miranda, Ariel, Umbriel, Titania and Oberon would be discovered to have be no less wonderful, if we only had a chance to view them over a longer period and up close.

Posted by: RNeuhaus Nov 8 2005, 07:20 PM

As we know that Venus' atmosphere is very heavy, about 90 times of Earth's ones and it is like that we are about 900 meters under the sea.

Then it is true that when "we" or the robot are on the Venus' surface, then we are going to walk very slow and alike as to swiming under the water, isn't ?

If it is true, so the spacecraft won't need a parachute to land on the Venus' surface when it is above, as an example 1000 meters of surface since the spacecraft, without a parachute will go down like a shipwreck?

Rodolfo

Posted by: David Nov 8 2005, 07:44 PM

It seems to me you'd still need a parachute to slow your descent through the upper layers of atmosphere. But according to what Bruce is saying, if your craft has enough buoyancy, you don't ever actually need to land; the craft could float in the atmosphere without ever touching down.

Posted by: RNeuhaus Nov 8 2005, 08:11 PM

Thanks David.

Now it understand perfectly.

It is very funny to think this strange experience: walk in the air like under the water...

Of course, the buoyance depends upon the relative of density of the body-weight of spacecraft versus the Venusian air. So to land to Venus is by far simpler than to Mars since there is no worry of final thrust before landing the surface.

Rodolfo

Posted by: tty Nov 8 2005, 09:14 PM

I don't see why. Normally You use a parachute to do the final braking after a probe has more or less slowed to terminal velocity. In the Cytherean(?) atmosphere terminal velocity would probably be low enough for a "soft" landing (or even zero at some point i. e. floating).

There is another problem though, I seem to remember that more or less all landers have experienced problems or damage in some particular altitude band in the atmosphere, so there may be bad things we know little about there.

tty

Posted by: JRehling Nov 8 2005, 09:29 PM

Venus's air exerts the same pressure as water 900 m under the sea, but it is by no means as HEAVY as that water, or as viscous. It is possible for a craft to land without a parachute -- modest design factors should still maximize surface area: a needle-shaped craft would smash very hard.

But don't mistake pressure with density and viscosity. These are three separate things. Oil can be lighter than water and at the same time more viscous. Water is not much denser at 90 atmospheres than at 2 atmospheres. Perfect gas laws don't apply to gases, and they certainly don't apply to water! The fact that wood is lighter than water doesn't mean you can swim through wood.

Posted by: ljk4-1 Nov 8 2005, 09:37 PM

The later Veneras (9-15) only had to use their aerobreak disk to land safely on Venus once released from the entry shell, the atmosphere is that thick. Imagine something like a coin drifting down to the bottom of a pond, only more stable.

Regarding the protection of the lander from the harsh environment, would it be possible to put some kind of shelter around the lander and its immediate area? I am envisioning a tent made of special materials that would unfold in an area around the lander. Would an inflatable type shelter work? If it could at least reduce the temperature around the lander to make it possible for the machine to last longer and conduct its data gathering, I would consider it worth it.

How about using the surface itself as protection? Could the lander have a way to dig down enough to cover itself with regolith? Would a Deep Space 2 type penetrator work?

These may be seen as "radical" ideas, but for a probe to last on Venus longer than a few hours, the scenario demands radical ideas.

Posted by: helvick Nov 8 2005, 10:17 PM

The problem is that the heat on the venusian surface is just high ambient temperature, diffuse and scorching. Think something like a high pressure kiln that has been burning for millenia so the heat is probably extreme all the way down, or at least down to depths of kilometers so digging in won't help, the heat is constant and everywhere. There is no precipitation to shelter from at low altitudes at any rate so there's no reason to do that.

A high altitude landing on top of Maxwell would be quite a bit cooler with lower temperature and pressure. Still insanely hot and pressurised though.

Posted by: BruceMoomaw Nov 8 2005, 10:48 PM

God, what a flock of questions! Let me answer at least a few of them:

(1) Venus' atmosphere isn't nearly as dense as water -- but it IS dense enough that, as LJK said, the Soviet landers carried out all the final part of their deceleration just using a circular disk (not very wide) fastened to their upper end as a drag brake. (They touched down on a ring fastened to their by a bunch of shock-absorbing struts.)

(2) Venus penetrators are simply not worthwhile -- the surface, after all, is as hot as the atmosphere, and the slim shape of a penetrator makes it much harder to properly thermally insulate its contents.

(3) As for the corrosive atmosphere, there are some worries about that -- but the sulfuric acid in Venus' air is found only in the upper levels at the cloud layer (where its droplet density is actually quite sparse; as with Titan's smog, it's opaque from the outside only because the layer is so spatially thick). There clearly IS something chemically reactive in the trace gases in Venus' hot lower atmosphere, which caused the mysterious set of reactions that caused a large number of the sensors on all four of the Pioneer 13 probes to malfunction at (I believe) 8 km above the surface -- but what that something is we still don't know, despite an entire workshop devoted to the mystery two decades ago. Apparently some substance on the sensors -- probably their insulation -- actually reacted with some trace gas and caught on fire at that height, but we still have no idea just what the reaction actually was, or why the Soviets had no such problem.

(4) The idea of using tiny vacuum tubes on Venus electronics has actually been floated since the late 1970s. But the whole problem of temperature is still huge. On pg. 25-26 of the Solar System Strategic Roadmap report ( http://www.hq.nasa.gov/office/apio/pdf/solar/solar_roadmap.pdf ) -- which was described at the COMPLEX meeting as still mostly valid -- it's noted that we have electronics that can operate at 300 deg C (not 250, as I stated earlier), but we still need 200 degrees higher. Also: "Not all electronic components can or should be implemented in high temperature components. Communications and power electronics have the most payoff. Digital electronics, which have low power dissipation, are best implemented in conventional electronics by using active thermal control." The idea of running the active cooler with a mechanical drive that utilizes the large amount of waste heat from an RTG is mentioned (as a necessity) on pg. 22. For this reason by itself, an RTG seems to be a necessity on any long-lived Venus lander. (A Venus rover that would use just such a system is described at http://www.agu.org/cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm05&database=%2Fdata%2Fepubs%2Fwais%2Findexes%2Ffm05%2Ffm05&maxhits=200&="P54A-06" -- although, once again, wheels seem less practical for Venus exploration than an active buoyancy system, utilizing a small steel bellows balloon as described by Victor Kerzhanovich, which allows the rover to glide along just a few meters above the surface and touch down periodicially for sampling.)

(5) As for electric power, I've seen both RTGs and temperature-resistant solar cells mentioned as possibilities (the latter for the bobbing Venus Geoscience Aerobot). There is actually quite a lot of sunlight on Venus' surface -- even given the blocking of sunlight by the cloud layer, it's about half as bright on the Venusian surface as it is on Earth. But another possibility for the VGA is a simple vertical windmill fastened to the gondola, utilizing the flow of dense air past the gondola during descent and ascent to run a generator recharging onboard batteries.

(6) As for the scientific goals of long-lived Venus landers, the Strategic Roadmap places great emphasis on the search for granite or sedimentary rocks that might indicate the presence of oceans on ancient Venus. It's a bit hard to see where we go from there, though. Just finding any sedimentary deposits on Venus that might be able to preserve fossils will be atrociously hard, let alone examining them for microbial or biochemical fossil evidence using in-situ instruments. (Especially since, I imagine, the heat alone will have been likely to break down complex organics even in the interiors of sedimentary rocks.) A sample-return mission would be mindbogglingly difficult and expensive -- the figure of $10 billion has been mentioned in the past, which means that there's an excellent chance that we won't have seen it by mid-century. And indeed the National Research Council, in its review of the Strategic Roadmaps ( http://www.nap.edu/books/0309099439/html/ ), indicates on pg. 18 that the Roadmap errs in describing such an astrobiological goal as the only important goal for Venus exploration -- which will be especially true if it turns out that the massive crustal recycling processes that seem to have occurred on Venus have totally destroyed any ancient crustal rocks. The only workable way to explore Venus would seem to be very incrementally -- checking cautiously with early missions to see if there's anything geologically interesting enough down there to be worth any near-future follow-ups with more technologically sophisticated and much more expensive later landers.

Posted by: Waspie_Dwarf Nov 9 2005, 12:23 AM

I can see the sense in this system. With these Venera craft having such a short life span it would be imperative to get them onto the surface as quickly as possible. The last thing you would want is for the spacecraft to die whilst it is still dangling from a parachute.

Does anyone know at what altitude the craft seperated from the aero-sheild / parachute?



Does this system actually make sense? For a short lived vehicle the battery life isn't the major consideration. The craft itself is likely to die before the batteries. For a long lived craft then the amount of battery time conserved is negligable compared to the life of the probe.

Even on a short lived lander this system would only make any sense to me if the windmill / battery recharging system were to offer a weight reduction over the additional batteries required for the re-entry landing phase of the mission. Even then the added complexity of the system makes it more likely to fail, actually reducing the lifetime of the lander.

Posted by: Jeff7 Nov 9 2005, 02:05 AM

I'm not quite sure of something here, probably due to my limited knowledge of the subject :
As I understand it, an RTG relies on a difference in temperature to cause a thermocouple to produce current flow. If both the RTG and the environment are hot, how's it going to produce power?

Posted by: Rakhir Nov 9 2005, 04:05 AM

For Venera-9 and -10, main parachutes were jettisoned at the altitude of 50 kilometers above the surface.

http://www.russianspaceweb.com/venera75.html

Rakhir

Posted by: JRehling Nov 9 2005, 04:21 AM

Because the RTG will be hotter. It's that simple.

An RTG produces heat *energy*. If radioactivity produces enough heat to warm an object by 10 K, it will do so whether it is from 1K to 11K or 1000K to 1010K. (Well, barring phase shifts, which are avoidable in the Venus case.) And the temperature differential is what makes power.

Posted by: Waspie_Dwarf Nov 9 2005, 04:29 AM

Thank you Rakhir.

Posted by: abalone Nov 9 2005, 06:15 AM

I assume it will be close to opposition during landing, is that correct? Does that not mean the night side of Venus? Not good for solar panels.

Is there a thermal gradient between day and night side, what temperature is the night side?

Posted by: edstrick Nov 9 2005, 07:08 AM

You can't do solar panels on the surface of Venus. Illumination is about 1% of that at the noon cloud-tops, and I don't know if any solar cells will work at all at the ambient surface temperature.

Posted by: Richard Trigaux Nov 9 2005, 07:57 AM

In thermodynamics, RTGs are thermal machines, just like a steam locomotive. They use a heat source (here a radioactive material) and a heat sink or cold source (usually space, it is why the Cassini RTGs are mounted outside the spaceship, painted in black with a radiator shape). The maximum possible efficiency of any thermal machine increases with the temperature difference between the two heat sources (This is the Carnot theorem) and you must in more account with many losses in heat or mechanical energy.

In a RTG the transformation of heat into electricity is done by thermocouples, which are semiconductor crystals with special properties and arrangement. Their efficiency closely matches the Carnot theorem, except for their electrical resistance and some loss of heat through them (from the hot source to the cold source). The maximum hot temperature and minimum cold temperature are determined by the working range of the semiconductors used, usually 300°C for the hot source and minus something for the cold source.

On Venus, the "cold" source is very hot (460°C) and thus the hot source must be much hotter. This is not a problem for the heat source itself, which is made of high fusion point materials (plutonium ceramics, graphite, irridium...) but the problem is to find a semiconductor able to function between, say, 450°C-1000°C.

A possible alternative is thermoionic electricity: in a vacuum between the two heat sources, the hottest projects thermal electrons, thus producing current. This was used into soviet military satellites, but with a miniaturized fission reactor in place of a plutonium source.

Posted by: Richard Trigaux Nov 9 2005, 08:10 AM

Thank you Bruce for your comments, which are always interesting.

AS a former envirnment activist I have some knowledge about solar cells, at least on Earth. (there are not yet environment activists on Venus):

Even by cloudy weather, solar cells can catch some solar energy, called diffuse radiation. On Venus, the direct solar radiation (not scattered by clouds) may be as low as 1% in visible light, but there may be more infrared radiation (that solar cells catch more easily) and a bunch more of diffuse radiation. So solar pannels are not ruled out so easily, they just need to be large. The only real problem is to get a material able to work at 460°C and resistant to chemicals in Venus air. This is not a simple problem I think. By the way, a solar cell working at 460°C and using the 6000°C solar radiation would not violate any thermodynamics principle.

A possible trick would be to have the lander race the sun, on Venus it may be possible at a low speed, and the lander would work all the time. But it would not be all the time into interesting places.

Posted by: Richard Trigaux Nov 9 2005, 08:18 AM

The worse problem may not come from sulphuric acid, which is not present at ground level. But there is steam, which at 460°C is a powerful oxydizer (it will burn a steel structure in some hours) and sulphur dioxyd, perhaps S and S03 and others, such as fluorine and iodine (which were seen from Earth, in the clouds, in an ultraviolet band). These bodies are even more powerful oxydizers at 460°C, and sulphur, iodine and fluorine may be able to react with bodies which do not react with oxygen. This is why I think a "venus test chamber" would be a mandatory test for any instrument and material on Venus.

Another reply soon, I have a rendez-vous now.

Posted by: BruceMoomaw Nov 9 2005, 09:15 AM

A windmill may make sense for the VGA because that probe is supposed to rise and fall REPEATEDLY over a months-long lifetime. As for solar cells on the surface of Venus, the official design I've seen for the VGA on JPL's website portrays them -- and actually, since Venus' cloud layer reflects back only about 80% of the sunlight hitting it, which is over twice as intense as that on Earth, quite a bit of sunlight reaches Venus' surface. (Of course, the VGA is supposed to spend most of its time floating around in the cloud layer, where the light level is higher than at the surface.)

Posted by: BruceMoomaw Nov 9 2005, 09:22 AM

Aha! Here's a nice detailed article by Geoffrey Landis on these subjects: http://mit.edu/aeroastro/www/people/landis/Venus_Power.pdf .

He thinks that solar cells are a possibility despite the fact that the light level on Venus' surface is only 2% of the sunlight hitting the clouds: "about the same as a rainy day on Earth". Also, we do already have solar cells that can endure Venus' surface temperature -- but so far they work only in the blue part of the spectrum, which is minimized on Venus' surface. However, this does allow you to see how they could be useful on the VGA, drawing most of their power during its time in the cloud layer to recharge its batteries for its occasional descents.

At any rate, Landis describes in detail an RTG power and cooling system. (He also proposes a solar-powered cloud-layer airplane.)

Posted by: Richard Trigaux Nov 9 2005, 09:42 AM

For batteries we have a ready-made solution: sulphur-sodium, which work at 300°C or more, have a good efficiency an high number of cycle. There was developments for car use, but the need to maintain them at high temperature made lithium-ion batteries prefered.

The idea of an aerobot cycling up and down is appealing, it would allow the probe to work at lower temp. The basic defect is that such a probe would work only a small part of the time, and wander without control with high altitude winds.

Posted by: Richard Trigaux Nov 9 2005, 10:16 AM

I think that, besides understanding formation and evolution of Venus, the search for past life (or at least past Earth like conditions) is the most interesting goal. If we find that Venus had granite or water, even a long time ago, that makes of it candidate n°1 for life in the solar system. Even finding a very ancient primitive fossil such as a stromatolith would be a breathtaking evidence, and the actual existence of life elsewhere than on Earth would have inhcredible philosphical/moral implications.


About the mountain ranges on Venus, I stated above that they could be continents like on Earth. But on Earth the surface and altitude of continents are the result of two opposite forces:
-plate tectonics which tends to gather and shrink the continents (small surface-high altitude)
-erosion by rain which tends to spread the continents and arase all what is above the ocean level (which makes flat continents, except where mountains are actually growing).

What happens on Venus could be a bit different, if a plate tectonics played alone and gathered small but high-altitude continents. If this is the case, it implies that there never was a large ocean. On the other hand, most theories of plate techtonics say it is driven by water on the surface, explaining why there is not on Venus. Anyway there could have be some running water on Venus before the today sulphuric acid cloud layer absorbs all the available water.

So, if the Venus mountains are really continents, they are certainly formed of granite and other light rocks, floating on a basaltic mantle (explaining why they keep their altitude despite softened rocks). This is the reason why searching for such rocks in continents is the N°1 geological objective (Some pancake volcanoes may be trachitic, a lava which is roughly molten granite).

To search for fossils at random is certainly hopeless. We need first a detailed geological map of all the mountains, in order to understand their formation and their detailed features.

For all these reason, I think that the geological exploration of Venus must begin with:

-A multi-frequencies high resolution several passes SAR radar mapping (low frequencies may have some penetration into rocks, allowing to better detect layering). This could be done with an orbiter, also using infrared cameras to probe the ground.

-A fleet of many small cheap aerobots, stabilized at an altitude just above the mountains. The main spaceship releases them in a timed sequence, on various trajectories, so that they enter the atmosphere and fly over mountain ranges, caried by high altitude winds. Their unique instrument would be a multispectral infrared imager, allowing to determine the composition of rocks in mountains and some other places of interest. They would be powered by batteries and cooled by a bottle of nitrogen, and last some hours or some days, so that we do not have to bother with new technologies. Some understanding of venusian winds are however required, and this is preciselly the main goal of Venus Express.

These aerobots may give an understanding of the geological structure of the venusian mountains, and give some hints of places to search for fossils, the later requiring to stay for long in the venusian inferno.

If they find that mountains are formed of basalt, we are all false.

About fossils themselves, we cannot expect to find organic materials, certainly decayed for long ago. Even limestone and shells cannot be expected, and sulphur chemistry is controversial. We shall certainly find no surface layer billions years old, even with the weak erosion on Venus. And continents may certainly have a heck of a geography, unpracticable on wheels and even on legs: most are formed of large folds, which reached and went beyong equilibrium slopes, forming cracks boulders and craggs everywhere. But, with a flying bot, this turns to be our chance: large sections of thick geological layers are available everywhere. This is why I suggested an aerobot musing vertically along cliffs, where it could examine closely the whole history of venusian sedimentary rocks (if there are some) in search of fossil traces: stromatholites, diatomites, vugs, worm paths and imprints in shales, etc.

The first instrument of this aerobot would be a radioactive datation system, and after a composition and crystallography lab. This would allow to understand the layer sequences. After, a large field microscopic imager with a shape detection software would allow to search for fossil traces, and send on Earth the most relevant among billions of images.

Eventually, if we find some unclear traces, the aerobot could end with the samples in a given rendez-vous place, holding the sample cannister ready for a further sample return mission. But, I think, if we do not find clear shapes, we shall no more find chemical traces, so that a sample return mission seems not very relevant for now.

A tip for a sample return mission would be to have the sample cannister raised up by a baloon, and sent in low orbit by a small rocket. The problem with a venusian sample return would be that, starting from the ground, we need a Earth-sized rocket, like a Soyouz, and working in a venusian environment, and all this after a several months travel, packing, unpacking, etc. Dreadful.

Posted by: edstrick Nov 9 2005, 10:29 AM

Bruce said: "...Aha! Here's a nice detailed article by Geoffrey Landis on these subjects..."

Much better to have data than my arm waving recollections. I'm somewhat surprised any conventional solar cell material can work at venus surface temps. I was expecting the temp to change semiconductor bandgaps and all too much.

Posted by: Richard Trigaux Nov 9 2005, 10:35 AM

Worse than that, simply the impurities and layer boundaries will migrate, destroying any semiconducting geometry. This is why we need special materials, on which there are very little searches. Think there are already not enough searches for materials working... on earth.

Posted by: Bob Shaw Nov 9 2005, 01:05 PM

Bruce:

Regarding the racket from the nuclear refrigerator and it's effect on any surface seismometer, there's an fairly easy way to insulate one from 'tother - stick the noisy thumping stuff under a balloon, and simply feed power and data cables to the seismometer on the surface...

Bob Shaw

Posted by: Bob Shaw Nov 9 2005, 01:07 PM

Emily:

The trouble with spin-off applications from Venusian surface technology is that there really aren't that many times we're going to find uses for deep-sea fireman's suits on Earth!

Bob Shaw

Posted by: Bricktop Nov 9 2005, 01:21 PM

ESA's page on Venera-D
http://www.esa.int/SPECIALS/ESA_Permanent_Mission_in_Russia/SEM0LFW4QWD_0.html

And for those who can read russian , an interesting article about a long duration soviet Venus probe being developed during the 80s, but never launched.
http://www.novosti-kosmonavtiki.ru/content/numbers/223/45.shtml

Posted by: RNeuhaus Nov 9 2005, 01:36 PM

Good note. I am approaching to the reality. Your note has helped me to recall my physics' class and realized that the gas' law is not perfect. In spite of the fact that the greater pressure on the gas, the density of the gas will increase but it wont' be as dense as the water.

Now I understand clearly that the density is not related to the viscosity. The density is related to the weight by volume space and the viscosity is related to the material property.

Again thanks to JRheling

Rodolfo

Posted by: BruceMoomaw Nov 10 2005, 12:40 AM

Except that you probably have to cool the seismometer itself -- and of course that balloon is going to be tugging at its anchor on the surface, thereby producing a fair amount of noise that way...

Posted by: hendric Nov 10 2005, 04:40 AM

Here's a thought...what about a probe that enters into one of those deep sea thermal vents? How much applicability would Venusian high temp/pressure technology have for Jovian exploration?

<funny>
Or maybe you could put electronics on an aeroshell...
</funny>

Posted by: Jeff7 Nov 10 2005, 05:21 AM

Ok. I just didn't have any idea at all of how hot an RTG gets. The only applications I've seen them used in are places that are potentially VERY cold, like say, space. So I just wasn't sure.

Posted by: edstrick Nov 10 2005, 09:34 AM

Just to throw a curve-ball into the discussion, I recall some comment from maybe 15 or more years ago, but the context entirely escapes me (who said it when and where).

The comment was that we already have an electronics technology that would work quite well at ambient venus surface temperatures: VACCUUM TUBES. You wouldn't even need filaments (so the commenter said) to heat the electron emitting cathode. Supposedly the tubes would be noisy due to the high temperature <electron-shot-noise or one of those statistically defined noise types), but it'd work.

Concievably, you could build really really DUMB seismic/ magnetometer <maybe> /meteorology stations and just let the suckers transmit raw data 100% of the time up to maybe 3 kinda data collection and relay orbiters about 1 1/2 venus radii out.

We have a real overkill problem with some spacecraft and missions. Mars Telecom orbiter was a good idea, but as bells and whistles were added, it blew the budget. I don't know what the cost of a barebones telecom orbiter would have been, and some very lightweight science could be added for almost no cost, but I think we ended up with the Mars Telecom Titanic. (glub glub)

Posted by: BruceMoomaw Nov 10 2005, 12:54 PM

There will be some big news shortly on that subject, which I'll be able to break in my "Astronomy" article if the MEPAG committee doesn't beat me to it.

Posted by: tedstryk Nov 10 2005, 05:01 PM

I wish that Russia would send another Venera lander on the level of the old ones, as it could probably be done provided it was funded relatively quickly. There have been changes noted in the Venusian atmosphere since the late 1970s. It would shed light on possible activity.

Posted by: ljk4-1 Nov 10 2005, 05:11 PM

In an issue of Omni magazine circa 1991, there was an article describing how the Russians had two complete, working Venera landers ready to go and for sale at a mere $2 million US. Apparently no one took them up on the offer.

Anyone know what became of those Veneras? If they are still in good shape, take them out of mothballs and aim them at Venus. I would rather look at full scale replicas in museums, knowing that the real probes were out there exploring strange new worlds.

Posted by: tedstryk Nov 10 2005, 05:18 PM

That would be a cheap opportunity to do some excellent science. But it would have to be done soon, while there are still people alive who know how to operate Soviet spacecraft from that era.

Posted by: JRehling Nov 10 2005, 05:43 PM

If the goal is to probe atmospheric changes, I'm sure there's a cheaper way. The Veneras were the size of tanks, and if all we need is a GCMS and a transmitter, and don't even need to worry about surviving the heat (the readings could be done at altitude), designing a simple mini probe from scratch on the smallest possible booster would surely beat the cost of putting a free Venera on a big booster.

I think VISE will be the next surface probe to Venus, and not within ten years. Prepare to wait. :|

Posted by: tedstryk Nov 10 2005, 06:22 PM

Right, but I was meaning that looking for atmospheric changes would be a good justification for a mission that would do a lot more science, such as giving us basic data on another area of the surface.

Posted by: Richard Trigaux Nov 10 2005, 07:31 PM

Bad decision. If we compare two missions such as the MERS and Huygens, there is a tremendous difference, mainly because of the data rate. With huygens we had only some poor quality low bit images, when with the MERS we have a constant flood of high quality images. This is because we have three satellites in orbit around Mars which offer large band communication channels at nearby every time.

So sending a bare communication satellite around Mars, Venus, or any other Planet (I suggested a 50 years lifetime radio relay around Saturn for exploring Titan with large band communication) this is perhaps the very first thing to do.

The problem is that such a satellite would made no discoveries, it would bring no glory to the sender. So it must be associated with science equipment or more complex mission.

To send large band long lived radio relay around the different planets would be a good topic for international missions, kind of basic space UN. The relay would be used by everybody afterward.

Posted by: tedstryk Nov 11 2005, 02:24 AM

Well, I don't know about the space-based U.N. ... the purpose of telcom satellites is to make communications more efficient, not less. Seriously, the comparison between the MERs and Huygens really isn't fair - Huygens had so little time to return its data, and so much to image. The MERs have had years.

Posted by: Richard Trigaux Nov 11 2005, 07:20 AM

Space-based U.N. ... good joke... and a very serious allusion. My stance is that countries must co-operate in space exploration, not do this childish competition. In a way it is what happens, due to the terrible constrains of designing and operating a space mission. But I find appaling that some countries which posses irreplacable technologies refuse to grant the use of them to others, for bad political pretexts.


Yes comparing MERs to Huygens is not completelly fair, but it is understandable. A really fair comparizon would be between Galileo and Cassini, which provided comparable science outputs. But alas Galileo was impaired with her dead large gain antenna, and she produced only scarce images awaited for months, when Cassini yelds a constant flow of tremendous images.

My idea was, like yours, that a telecom satellite around Mars, Venus, etc, is an indispensible condition for sending aerobots and landers, as the later cannot send large flows of data directly to Earth.

I should even say SEVERAL telecom satellites, which would also operate a kind of GPS, which is also indispensible to efficiently locate landers and flyers, especially on cloud-shrouded planets.

Posted by: ljk4-1 May 4 2006, 05:26 PM

VENERA D - future Russian mission (5 to 30 days on planet surface)

O. Korablev, L. Zasova, M. Gerasimov, A. Rodin, A. Basilevsky, V. Linkin

Abstract:

http://www.aero.jussieu.fr/VEP/abstracts/Korablev_abstract.doc

Presentation (940 Kb):

http://www.aero.jussieu.fr/VEP/presentations/Korablev_presentation.pdf

Posted by: DonPMitchell May 8 2006, 04:56 AM

NASA and ESA have deep "not invented here" issues. They would spend a fortune instead of buying a Russian lander. Look at how the Venus/SAGE mission has evolved. It started out as a Venera lander on a Fregat, cheap proven technology, and now its been almost completely redesigned by NASA.

Is Russia still a major partner in SAGE? The list of experiments look like their stuff (rock drill, panoramic camera, x-ray spectroscopy).

I guess its not all bad. If they think that can make progress, do it better. But I sure hope they are talking to the Russians. The Pioneer Venus landers didn't do so well in the lower atmosphere.

Posted by: BruceMoomaw May 8 2006, 05:20 AM

"Is Russia still a partner in SAGE?" No. Two years before this public report came out, Esposito accidentally put the list of SAGE experimenters on the Web (though not the experiments they were associated with), and I stumbled across it. Not a Russian among them.

The main reason for not using a Venera for "SAGE", however, is very simple: they weigh far, far too bloody much for our cheaper boosters -- and the law currently forbids launching any US craft on a Russian booster, lest it interfere with our own launcher industry.

As for the still-mysterious incident that screwed up the Pioneer 13 probes at 14.5 km above the surface: the general feeling is that it was insulation actually catching on fire in a reaction with some of the trace gases in Venus' air at that temperature. And while we still don't know exactly what it was, taking a whole set of corrective measures against various possible causes should nail it (as the swarm of protective changes made in Ranger 7 eliminated the cause of the Ranger 6 failure, although that exact cause wasn't nailed down until later).

Posted by: DonPMitchell May 8 2006, 06:46 AM

Interesting. So SAGE seems to be an all-American version of the Venera-Discovery proposal. The thing about Venera-Discovery that I liked was the neutron-activation experiment.

Are you sure it is still illegal to launch US crafts from Russian rockets? I thought Protons were being used to put up US satellites. There's also the Sea Launch project. Galazy-14 was launched by Soyuz-Fregat last year. I think there was a law, and it was dropped after US companies became heavily invested in Russian space facilities.

It is the case that Europe just made it illegal for them to use foreign launchers. The exceptions seems to be when they need Soyuz/Fregat. I believe Ariane is only capable of excuting pitch control from equatorial launch point -- a cheap way to loft geosynchronous satellites, which skims the cream off the top of that market.





Definately, that was a great post!

The seismographs on Venera-13 and 14 were external, as was an electronics unit associated with it. I think RNIIKP has gotten very good at that game. I haven't been able to get any details about its electronics technology from my friends at IKI. That may be a sensitive subject.

The Russians have supposedly developed both radio-isotope thermopile and windmill generators for the surface of Venus. They did some tests with solar cells on several of the Venera landers, geared toward a study of using solar cells for balloon-born probes, which are up at a much higher light level. I would guess that light levels are too dim at the surface.

Posted by: BruceMoomaw May 8 2006, 07:17 AM

One thing Esposito's SAGE does not carry is any kind of gamma-ray spectrometer, with or without a neutron source. It seems to rely on the combined XRD/XRF (which I believe is a duplicate of the one on MSL, although I'll have dig up and recheck the list of experimenters for that) for all its element measurements.

This brings up a point I've been interested in for some time -- which is that tests have already shown that the LIBS which MSL will also carry for instantaneous and long-range element analyses which should be as good as those from its APX spectrometer (the two instruments will double-check each other) should also work fine on Venus ( http://www.lpi.usra.edu/meetings/lpsc2004/pdf/1338.pdf ). If so, then any Venus lander can use LIBS for a whole multitude of very fast and very accurate element analyses on the surface for meters (maybe even tens of meters) around its landing site -- without the need for any drill, airlock, or port through its pressure hull, except for a fiber-optic lead! LIBS, in short, may be a Godsend for future Venus exploration.

The question is whether we can devise an acceptable instrument with the same characteristics for mineralogy. X-ray diffractometry, which requires that the lander ingest a sample, is universally accepted as by far the best way to analyze minerals -- but work is already under way to combine LIBS with a Raman spectrometer (using the same laser beam) for long-range and instantaneous mineralogy on Mars. (There's been a lot of successful lab work on this, but it couldn't be gotten ready in time for MSL.) No one seems to know yet whether Raman -- which depends on analysis of an extremely tiny component of the reflected laser pulse -- could work at long range in the light-blurring atmosphere of Venus; but even if it can't, one can conceive of a Venus lander using a simple movable instrument arm, with a fiber-optic lead at its end, to touch places on local rocks and soil and do Raman analysis (and microscopic imaging) of them that way.

There are, however, things that Raman cannot do, such as -- if I remember correctly -- analyzing iron minerals. How much of this, however, could be done by near-IR reflectance spectrometry instead --especially with an artificial light source on the lander to provide those wavelengths that Venus' atmosphere filters out of the natural sunlight there? (Add a shadowing shroud to that movable instrument arm, and such an instrument could also do separate thermal-emission IR spectrometry of local patches of the surface without reflected sunlight getting mixed up with the short-wavelength thermal IR from that very hot surface.) A surface lander which used these instruments instead of having to drill up and ingest any samples -- and which didn't carry the atmospheric-composition instruments on SAGE (which could be carried on a single separate entry probe) could be lightweight and cheap enough that several of them could be dropped onto different places on Venus by a single lander, and quickly analyze dozens of different samples in the lander's vicinity.

As for the nature of the current US laws on the use of foreign boosters: you know more than I do.

Posted by: Jim from NSF.com May 8 2006, 01:13 PM

US commercial spacecraft can use foreign LV's. But US Gov't spacecraft are prohibited, except in barter agreements.

Posted by: BruceMoomaw May 12 2006, 08:57 AM

Good description of the original Russian/American "SAGE" can be obtained indirectly at http://adsabs.harvard.edu/abs/1993LPI....24.1381S .

Now for the instruments on the proposed American SAGE. As I mentioned, back yonder in 2003 I stumbled across a list of the experimenters for Larry Esposito's "SAGE" which he had inadvertenly put on the public Web where no-gooders like me could see it. After I sent him a message asking for further information, he reacted with shock and horror and hastily yanked it off the Web -- but not before I'd made a copy, heh heh. And now that JPL's public technical report on SAGE is finally available ( http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/38184/1/03-2520.pdf ) we can match some of them up nicely.

Descent Imager and Spectral Radiometer -- Uwe Keller, Max Planck Institute (a member of the Titan DISR team)

X-Ray Fluorescence and Diffraction -- David Blake, ARC (PI for the "CheMin" instrument on MSL)

Gas Chromatograph/Mass Spectrometer -- Paul Mahaffy, GSFC (PI for the "SAM" instrument on MSL)

UV Imaging Spectrograph -- Bill McClintock, LASP (U. of Colorado)

The others are harder to match firmly. One is "Colaprete", which has to be Anthony Colaprete of ARC -- an atmospheric specialist, which seems to link him with the Atmospheric Structure Experiment. Another is "Boynton", which seems to be John Boynton of LASP -- one of the two people mentioned on the Web as associated with the Camera Hand Lens Microscope (which has already been tested). Finally, we have "Crisp", which is probably either David Crisp or Joy Crisp of JPL (married, I presume). David seems to go in more for meteorology instruments, though, while Joy seems to be a geologist, which links her closer to the PanCam.

Anyway, as I say, not a Russian in the lot, and indeed there seems to be virtually no intersection between the experimenters (and instruments) on the first SAGE and the second, all-American SAGE.

Posted by: DonPMitchell May 12 2006, 04:42 PM

Maybe it was a politcial mistake for Brown University to include the Russians. So they lost the mission to a rival team. But in any case, they would be wise to take a peek at how the Russians built Venus landers.

Posted by: Bob Shaw May 12 2006, 06:20 PM

Bruce:

Some grabs from the .pdf you pointed us at showing the SAGE spacecraft layout - note also the substantial drill assembly.

Bob Shaw

Posted by: DonPMitchell May 12 2006, 08:22 PM

It's a clever mission plan. The Venera spacecrafts were 6 tons, and required a Proton rocket to launch. This proposal is basically the Vega lander stuck on a Fregat. It can be launched by a Soyuz, and the pieces are probably all sitting in a warehouse at NPO Lavochkin.

But it's Not Invented Here. :-)

Posted by: ljk4-1 May 12 2006, 08:29 PM

Those are probably the very landers mentioned in Omni magazine in 1991
that Russia tried to sell for just $2 million.

Posted by: BruceMoomaw May 12 2006, 11:05 PM

Actually, the first and second "SAGEs" never even had the chance to become rival concepts. The first one was an idea for a possible Discovery mission mentioned back in the early 1990s, a couple of years before the first AO for any Discovery mission even went out. It never even became an actual proposal.

Esposito's "SAGE", on the other hand, was a proposal for the first AO for the new New Frontiers program, which was released a decade later. The only thing they have in common is their name.

Really, though, if ever I saw an opportunity for a possible US/Russian collaboration that might actually work, this is it. The Russians just might be able to build a copy of their old Venera spacecraft without screwing it up. (Mars 96 -- based on the Phobos design, which they had never been able to get to work -- was so complex and built on such a shoestring that, even had its launch succeeded, insiders thought the chances that the spacecraft itself would work were virtually nil. They were building the thing by GASLIGHT, for God's sake, because the Russian space agency couldn't pay its electric bills!) Have the Russians build and launch 1 or 2 Venera landers equipped with good American (or European) instruments and you might really have something -- and at this point Russia might actually be able to afford to build them properly.

I have a bit more information coming on Esposito's SAGE later today.

Posted by: BruceMoomaw May 13 2006, 10:58 AM

And here it is. One of the primary investigators on SAGE was Bruce fegley of Washington university (located, oddly, in St. Louis); and in 2003 he put a Powerpoint rpesentation on the Web regarding the desirable goals for such a Venus lander (keeping in mind that his own Venusian specialty is chemical interactions between the surface and atmosphere). That presentation no longer seems to be there -- but, once again, I recorded it at the time. It was nicely detailed, but here are what seem to me to be his most important spefications:

(1) The key atmspheric measurements include temperature and pressure profiles from the surface to the clouds. (Oddly, he says that not only did the Pioneer probes fail to get data below 12 km, but so, for some reason, did Vega 1 -- and since the 1970s Veneras were of questionable accuracy, Vega 2 sems to have provided us with our only good low-altitude T and P profile so far.) They also include composition, using a GCMS -- in order of priority:
Overall abundance of H2O, CO, SO2, N2 and the noble gases
Vertical profiles of the first three
COS, H2S, HCl and HF
Isotopic ratios for H, C, N, O, S and the noble gases
H2, H2SO4
CO2 abundance below the clouds

(2) The top priority surface analysis site should be a big representative region for average Venusian chemistry and mineralogy. Second priority is an anomalous region -- either a tessera ("some propose these are metamorphic"), or one of the high-altitude high radar-reflectivity regions. Both primary rocks and phases that have reacted with the atmosphere are needed -- preferably a depth profile using a drill core, and including if possible an examination of the atmospheric gases at different depths in it (here his own biases show).

The top-priority measurements are element and mineralogical composition together (elements by themselves are not worthwhile). The best mineralogical instrument is an X-ray diffractometer; element analyses should include elements from C through Na, which X-ray and gamma-ray spectrometry can't detect. Then, in order of priority, come:
Color imaging of the surface and the drill core
Fe oxidation state (he recommends Mossbauer for this)
Visible/IR reflection spectra
Oxygen fugacity in the surface (using a ceramic O2 sensor)

SAGE's payload, as indicated by the JPL description, doesn't include all Fegley's desired measurements, but it would include most of them.

Posted by: Myran May 13 2006, 12:14 PM

Oh yes those are really interesting, and might be really wortwhile to investigate. Whatever it is that covers high peaks of Venus, it certainly cant be anything we're used to. Especially interesting if it turns out those areas are covered by semiconducting metal salts as some have proposed as one explanation for the data.

Posted by: DonPMitchell May 13 2006, 12:41 PM

Why does he think Venera-9 - 14 had questionable readings? Their platinum-wire thermometers are not as good as our platinum-wire thermometers?

Posted by: BruceMoomaw May 13 2006, 10:41 PM

Damned if I know, except that his slide says that there was "low accuracy P and T data from the old Veneras". Nor does he say why he has more faith in the results from Vega 2 (or, for that matter, why there apparently were no good measurements from Vega 1), but he wonders whether the Vega 2 data was "representative". I should add that he wants really accurate data: "Measure T and P with ~0.01% accuracy. At the surface, this is +0.1 K and +0.01 bar."

Posted by: edstrick May 14 2006, 07:20 AM

Accurate measurements of stability and convective power of an atmosphere that is marginally stable or unstable against convection, like the sub-cloud Venus atmosphere, require extremely high precision. Unfortunately, the Net Flux radiometers on the Pioneer Venus small probes had a design defect that put poorly calibratable biasses and errors in the science results. Venera 7 and 8 temp data were very crude. Later Venera data were better, but maybe not as accurate as the Pioneer data.

Posted by: Richard Trigaux May 14 2006, 08:03 AM

If there are measurable abundancies of such gasses as HF, H2S, HCl and the like, at a temperature of 450°C, it is expectable that the surface rock are completelly rotten, see metamorphized, as are rocks around earth fumaroles. As sulphates or carbonate could not from at such temperatures, we may find a lot of other salts, sulphides and sulphites, chlorures and fluorures. Many of them could be semi-conducting.

Posted by: DonPMitchell May 14 2006, 02:24 PM

It looks like the accuracy of the Venera-9 to 13 and the Pioneer atmosphere probes were about the same, on the order of 2 to 5 degrees C. The Vega-2 probe had an accuracy of about 0.5 degrees.

The standard atmosphere is still based on a combination of Pioneer and Venera-10 data, fit to a thermodynamic model. Keep in mind that when you fit hundreds of measurements to a model, you get much better statistical accuracy than the error of the individual measurements.

Posted by: JRehling May 15 2006, 12:59 AM

Hopefully, the Venus DISR would return more data than the Titan DISR. The bottleneck seems to be less restrictive, since there is no relay necessary. I think the Huygens DISR did a fine job, even with half the data, of returning a full overhead panorama at reasonable resolution (although it was hell in terms of processing on the ground). But that one x-axis-narrow surface view aside, DISR returned nothing whatsoever from below a certain ceiling.

I think the imaging goals would be:

1) To locate the landing site in context (registering descent images with Magellan data).
2) To provide high-resolution (cm-order resolution) imaging of the immediate landing site.
3) To produce resolved multispectral imaging at a variety of altitudes.
3a) ...for its own scientific value.
3b) ...to benchmark the usefulness of such imaging to evaluate the worthwhileness of including such imaging in future high-mobility (aerobot) missions.

Per 3b, the benchmarking could potentially be performed with a much smaller mission before SAGE. If multispectral imaging has any use in making mineralogical discrimination on Venus, a dream mission would be one or more aerobots that spun around the planet returning imaging noodles that crossed many different types of surface unit, "coloring" in representative terrains that are mapped comprehensively by radar, giving us a pretty good inference of the mineralogy of the whole planet. If an aerobot could return this data while flying a Vega-like trek across Venus (~9000 km), one or two well-chosen entry locations could sample all the major terrain types.

GCMS could also be flown on a smaller mission; unless Venus is being washed in new volcanic eruptions on a colossal scale, this only needs to be flown once, ever.

Posted by: BruceMoomaw May 15 2006, 02:14 AM

The same thing is true of the UVIS, whose main purpose is obviously to identify the cloud UV absorber. In fact, Esposito proposed a "Venus Composition Probe" for the first Discovery AO (I don't know whether he repeated it) that would have been split into two modules: a vented one just for upper-atmospheric analyses carrying mass and UV spectrometers, and an armored module to survive until impact carrying atmospheric structure sensors and an IR spectrometer to proofile reactive trace gases.

As for Rehling's proposed composition-mapping high-altitude balloons: it might well be possible for them to get acceptable near-IR spectra of the local surface (at least through the limited spectral sunlight windows allowed by Venus' atmosphere and clouds); but it's more open to question as to whether they could get useful images. Tjhere have been quite a few studies of that, reaching differing conclusions:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6T-44P6R7R-1&_user=10&_handle=V-WA-A-W-AB-MsSAYWW-UUA-U-AACUWCBDAY-AAVDYBVCAY-YZEACVAAD-AB-U&_fmt=summary&_coverDate=03%2F31%2F2002&_rdoc=6&_orig=browse&_srch=%23toc%235823%232002%23999499996%231!&_cdi=5823&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=fb8cd131bd0ffd776eb2b26976a8d59f (I ahve Moroz's complete 2002 article, but it's no longer available for free on the Web.)

http://www.lpi.usra.edu/meetings/LPSC98/pdf/1646.pdf

http://www.aas.org/publications/baas/v35n4/dps2003/376.htm

The 1998 one was done in connection with the "VEVA" Discovery proposal for droppable imaging probes ( http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/13986/1/00-0365.pdf ), which actually reached quite optimistic conclusions: "Venus’ atmosphere has an opaque cloud deck above ~47-km altitude. Our simulations show that by imaging below the cloud deck in a window in the CO2 absorption at about 1 pm, interpretable images can be obtained even from 47 km altitude (images from this altitude will show primarily surface elevation differences due to the differing optical path lengths to the surface; lower areas will appear brighter). We also simulated the effects of near-isotropic lighting on aerial photographs and found that roughness-induced differences in apparent surface brightness (self-shadowing) provide good contrast between units even under these conditions."

Posted by: DonPMitchell May 17 2006, 06:05 PM

With regard to long-life missions, the Russians developed quite a few techniques, some of which you see copied in the Pioneer Venus probes.

1. Phase-change materials to absorb heat. Venera-8 used Lithium Nitrate Trihydrate, a substance that has almost the latent heat of fusion of ice, but melts at 30 C instead of 0 C. In the Venera-9 to Vega landers, a small internal fan circulated the air through a "heat battery" of this material. Instruments that extended outside the insulated hull were also packed in a layer of LiNO3.3H2O, the cameras and x-ray soil spectrometer, and external instruments like the IR/Visible spectrometer.

2. Insulation. They did a lot of research on this, developing some special high-temperature organic polymer foams and ceramic foams for the landers. Their early long-life lander proposal was to be insulated with aerogel. Alternating sheets of fiber quartz and metal foil was also used in places.

3. High-temperature lubricants. Molybdenum Sulphide mixed with metal flakes was developed for things like the Venusian soil drill. The used MoS2 instead of graphite (used by NASA) in space and on their Lunokhod rovers, based on some automated fiction tests onboard the early Zond probes.

4. Connectors. Russians are fascinated by connector technology for some reason, and special ones were developed for the external electrical systems on Venera landers. Given that the Pioneer probes shorted out, perhaps this is not a problem to be underestimated.

5. Coatings. Polysiloxane was popular, as an enamel paint for some parts. An almost indestructable polymer, semiorganic on a Silicon-Oxygen-Silicon clain.

6. Hardened electronics. I'm amazed by the amount of external instrumentation on the later Veneras, Ksanfomality's seismograph for example. I'm not sure what the technology was, Silicon MOSFET or possibly even miniaturized vacuum tubes.

7. Power sources. The Venera landers were powered by batteries (Silver Zinc are extremely energy dense). But they did some research on radioisotope thermopiles, windmills and solar cells. The surface is too dim for solar cells as it turns out. Small windmills did operate some of the Venera experiments that requried mechanical action during descent. And the Venerokhod rovers were to be wind powered.

Of course, they also took advantage of heat. Many "timed" events were activated by links designed to melt at specific altitudes on Venus. This included things like parachute reefing and covers on instruments to keep cloud goop off.

Posted by: Bob Shaw May 17 2006, 06:50 PM

Don:

Venerokhod?

Do tell!

Bob Shaw

Posted by: DonPMitchell May 17 2006, 06:54 PM

Yep. They developed a couple working models. Was used wind-powered electric motors, and another powered the wheels by direct drive from the mill.

Posted by: Richard Trigaux May 17 2006, 07:47 PM

Is there really some wind on Venus ground? Not sure, it seems a very quiet environment. At least dunes were not detected. If most of the sun heat is absorbed into the clouds, it is expectable that all the convection will happen into these clouds, not on the ground.

External connectors shorted on Venus probes? Possible explanations into this exotic environment:

-droplets of sulphuric acid
-action of other gasses, like HF (which attacks nearby everything)
-oxydation/sulphurization of insulators

eventually a very thin layer of sulphide forming on the surface of an insulator can be enough to turn it conductive, especially on Venus temperature.

Posted by: DonPMitchell May 17 2006, 09:08 PM

There is air movement of 1 or 2 meters per second on the surface, and keep in mind the gas is more than 100 times as dense as air at sea level. It's enough to blow the dust off the landing ring, which you can see in progessive panoramas.

You can also see some metal parts turning white over time, so clearly there is also some chemical action going on.

Personally, I'm not confident that they understand what happened to the Pioneer Venus probes. All four probes experienced serious malfunctions at about 12 km altitude. There's a special report about it, full of interesting speculations -- the parts maybe wet with sulphuric acid, maybe some of the materials eroded or ignited, maybe the probe passed through a zone of unexplained electrical activity. The Russians have reported a zone of strong turbulence at that level, but of course their probes were built like tractors.

Posted by: ljk4-1 May 17 2006, 09:14 PM

What is your estimate as to how much is left of the successful landers on Venus?

Have the older ones essentially corroded away by now?

Posted by: DonPMitchell May 17 2006, 11:20 PM

I believe they are probably still all sitting there, pretty much intact. The chemical betteries and lithium salts inside would boil, but at 100 atm of pressure outside, I don't think they would burst open. Must be a mess inside.

Posted by: Richard Trigaux May 18 2006, 07:29 AM

OK





Where can we see this?






What special at 12kms? It is far below the cloud top, so there must be something else.
Perhaps it is an altitude where the air is getting ionized (from some minority ion contributor) so there may be electric discharges or something, from the air or from te probe.
Or there is a dust layer. sulphide dust may play tricks with insulators.



What would remain of the probes today? Not intact I think. Everything organic must be burned, even beyond charring: carbon must burn. Everything metallic, save perhaps gold, must be oxydized and sulphurized in depth. Even ceramics are not insensitive to things like fluoridric acid. After, with years, all those oxyds and sulphides would disagregate and turn to a heap of dust.

That left us with a bit of a problem: there are already several earth hardware on Venus, and some of which position is unknown. If one day we find them back, there will be no way to tell if it is of earth origin of alien origin (an alien probe fallen on Venus could remain visible for 100 millions years or more). What I suggest for this is to use material with a known isotopic composition. Otherwise, if we find a remnant of an artificial part, there will be forever discutions about where it came from.

Posted by: DonPMitchell May 18 2006, 09:36 AM

You can see some examples of wind and other changes over a period of an hour or so:

[attachment=5681:attachment]

Hydrofluoric acid is only present in minute traces, and sulphuric acid only in the clouds. At the surface, it is not clear if the atmosphere is even oxydyzing. The atmosphere is primarily carbon dioxide and nitrogen, both relatively inert gases. I believe the Venera and pioneer probes will be laying around fairly intact for thousands of years.

Posted by: Richard Trigaux May 18 2006, 10:06 AM

Thanks for the images, Don.

Changes are not drastic, but they are visible.

Even if there is no oxygen at ground level, there is SO2, which is weakly oxydized sulphur. At 450°C it is not difficult that this molecule breaks in the contact of any metal, to oxydize it. Sulpur too is released, which is an oxydizer too. H2S too can release sulphur. Then it is easy to guess that materials like steel will quickly oxydize in depth. But it is not sure in how many time.



What I strongly suggest would be that any attempt to design something on Venus would be tested in a Venus simulation chamber, containing all the known or suspected gasses there, together with some wind or electric discharges.

Such a Venus test chamber would require special steels or ceramics coating. But it would assess which material can really withstand Venus conditions, and how many time.

Posted by: tty May 18 2006, 10:12 AM

Once the organics have charred to carbon the remains should be extremely stable. Elemental carbon is just about the most stable, heat- and corrosion-resistant substance around. If there is free oxygen/fluorine/chlorine in the atmosphere it might oxidize slowly, otherwise it could last almost for ever.

tty

Posted by: Bob Shaw May 18 2006, 11:00 AM

Don:

Are there enough images of the dust being moved to make an animated .gif? Or just the two you posted?

Bob Shaw

Posted by: Kodiak May 18 2006, 12:38 PM

Do you have any pictures of the Venerokhod's?

Posted by: Bob Shaw May 18 2006, 03:10 PM

Kodiak:

I found one - it seems they used Czarist-era technology, but kept quiet about it for reasons of Political Correctness! It appears that the lower part (the bit with eight legs) was known as a 'Turtle'.

Bob Shaw

Posted by: Bob Shaw May 18 2006, 03:21 PM

Of course, Comrade Turtle had the honour of setting many a long and glorious Soviet space record!

Bob Shaw

Posted by: karolp May 18 2006, 04:38 PM

And why didn't they have the Venerokhods launched if they were cheaper?

Posted by: DonPMitchell May 18 2006, 06:23 PM

Economic problems forced big cutbacks in the Russian scientific space program. The failures of Phobos-1 and 2 and Mars-96 cost those teams credibility. Space stations seem to have had much higher priority than planetary probe missions. They also make good money from commercial launches, they're good at it, and they pretty much stick to that now.

Also, after the death of Keldysh, there was no longer a powerful acdemic champion of interplanetary exploration. The head of IKI, R.Z. Sagdeev, was much more interested in theoretical cosmic astrophysics than in interplanetary probes.

Posted by: DonPMitchell May 19 2006, 03:58 AM

[attachment=5716:attachment]

Posted by: Bob Shaw May 19 2006, 12:00 PM

Don:

Ludicrously close to my joke version!

Ah, if only...

Bob Shaw

Posted by: Kodiak May 19 2006, 02:15 PM

Thanks for the Pics

The turtle looks as if it came straight from a mini-putt course

Posted by: Myran May 19 2006, 03:10 PM

Thank you for the image DonPMitchell.

And even though it looks like a crazy idea, it IS one working solution for a rover on Venus.
With solar cells not that efficient, a nuclear powersource that would risk overheating and melt.
(Unless you design something entirely new with a moderating liquid like lead which would be difficult at best.)

So yes the two windmills might look ludicrous, but with the round time for signals to Earth the Venerokhod would have to crawl rather than run.

And with the dense atmosphere the Venerokhod could have been provided with a larger generator than one might imagine since the rotors would have been pulled with a force more resembling that of running water than just a wind here on Earth.

Posted by: ljk4-1 May 19 2006, 03:11 PM

I wonder if it would work for a Titan rover as well?

Posted by: DonPMitchell May 19 2006, 03:43 PM

The image I posted is the direct-drive version, which used a transmission system to send torque from the mill to the wheels. Probably simpler and more efficient than trying to generate electricity and run motors. It was designed with an expected lifetime of one year on the Venusian surface, performing soil mechanics and temperature/pressure readings.

[attachment=5726:attachment]

VNII TransMASH is an intersting and (by Russian standards) one of the more excellent design bureaus. They build turbine-powered army tanks and industrial robots, and were the designers of the Lunokhod rovers. They also built the little mini rover on Mars-3 and various penetrometer devices on Venera and Phobos missions. TransMASH robots helped clean up the Chernobyl accident.

Interestingly enough, they were involved with NASA in the design of our Mars rovers, and built parts of the ill-fated Beagle lander on Mars Express. They've done a lot of experiments with low-gravity and micro-gravity traction, and materials and lubricants for hostile environments. They have a whole lab in a "vomit-comit" aircraft, to run experiments at Lunar or Martian gravity levels.

[attachment=5724:attachment]

Posted by: Myran May 19 2006, 03:45 PM

It might be one idea to consider as a powersource, especially since any nuclear power source would have so much waste heat that it could cause problems both on the surface and also in the atmosphere around the rover, and in worst case turn it into the first Titanian submarine - providing the hypothetical ocean are there.

Even so im not certain that a rover is the best vehicle for exploring Titan, with a surface which might be a colloid over wide areas a rover might end up being one record breaking expensive machine for making whipped cream while getting nowhere.

Posted by: DonPMitchell May 19 2006, 03:57 PM

Titan's atmosphere is so dense, I would look at some sort of low-altitude balloon probe for mobile exploration.

Posted by: BruceMoomaw May 19 2006, 09:30 PM

OPAG's Titan subgroup has alredy put in a lot of thought on the wheeled versus aerial rover controversy. Rovers have already been designed for Titan and other worlds years ago with inflatable tires so gigantic than they can cheerfully roll across the surface of water: http://www.space.com/scienceastronomy/solarsystem/aerover_for_titan_001020.html . But the steep-walled gullies discovered by Huygens, which are probably very common on Titan, might still present a serious problem for them.

However, the main reason why OPAG prefers an aerial Titan vehicle is simply that the really interesting differences in Titanian surface composition seem to be spread across very long distances rather than short ones. This was mentioned at the November COMPLEX meeting, and is also mentioned at http://www.lpi.usra.edu/opag/oct_05_meeting/titan_work_grp.pdf (pg. 5).

Posted by: DonPMitchell May 19 2006, 11:28 PM

There have been a lot of studies about more balloon missions to Venus. The French proposed a couple concepts in the 1970s, a large complex balloon probe or many small simple ones. Of course the Soviets actually flew a couple balloons (often incorrectly attributed to the French, but it was not their balloon).

There was a joint discussion of imaging the surface with a balloon at a lower altitude. Moroz pointed out that you have to get quite close to the surface to see anything, except at long wavelengths.

The "clear" atmosphere on Venus is not really clear. I remember Grinspoon on a BBC program described how you would see the surface as soon as you got below the cloud layer, but I think that's way off. Look at how opaque the atmosphere of Titan is, and it is quite a bit less dense than Venus. Rayleigh scattering is the problem, not just haze.

Just an idea off the top of my head, but I wonder if you could build a sort of tumble weed probe for the Venus surface, that would just be pushed around by the wind. You couldn't control where it went, but it would sure be a lot simpler than some sort of radio-controlled rover.

Posted by: Bob Shaw May 19 2006, 11:46 PM

Don:

A stainless-steel bellows, able to expand (and thus take off as the density of the whole structure is reduced) and then drift to a new landing site, that's the way. You could even design it to be wholly automatic, with no clever mechanisms employed, just some phase-change chemicals and thermocouples...

Not a rover in one sense, so much as a series of landers...

I still like the windmills, though!

Bob Shaw

Posted by: BruceMoomaw May 20 2006, 02:25 AM

(1) Grinspoon isn't the only one who's lots more optimistic than Moroz about imaging Venus' surface optically from high altitudes. See my May 15, 2:14 AM entry on this thread. (Also note how sharp shadow edges and the horizon seem to be in the Venera 13 and 14 shots.)

(2) That stainless-steel bellows balloon is already being talked about. Viktor Kerzhanovich described it in http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1223.pdf , and at the first VEXAG meeting in December somebody during the final summary talks orally described it as far preferable to a wheeled rover -- especially since, given Venus' high atmospheric density, a craft using it would really be more like a submersible, precisely adjusting its buoyancy to cruise along just a few meters above the surface and periodically touching down for sampling. (We are, once again, assuming a rover capable of surviving Venusian surface temperatures for long periods without cool-off periods.)

One side note: Kerzhanovich says that polybenzoxasole apparently isn't working out as well for Venus surface balloons as hoped. "Prior technology development efforts had concentrated on a single balloon that could operate across the entire 0-60 km altitude range, tolerating both the sulfuric acid aerosols and the extreme temperatures of -10 to +460 deg C. However, this problem was unsolved because no combination of sufficiently lightweight balloon material and manufacturing (seaming) technology was ever found to tolerate the high temperatures at the surface." However, when I E-mailed him to check this, he qualified that previous statement somewhat. I'll need to dig up his E-mail for more details.

(3) Since Don Mitchell has come late to the party: shortly before his arrival we had quite a long exchange here of recent information about Titan exploration techniques -- notably the "Titan Organics Explorer" airship designed in two altenative models by a JPL team (propeller-driven hydrogen blimp vs. wind-blown hot-air balloon): http://www.lpi.usra.edu/opag/oct_05_meeting/jpl_titan.pdf . There was a presentation on this at last December's COMPLEX meeting, which I attended -- in which a scientific appraisal group concluded that the wind-blown version, while obviously far less controllable in its selected touchdown sites for surface sampling, was nevertheless probably scientifically acceptable for this mission, as well as obviously being a lot cheaper.

Posted by: DonPMitchell May 20 2006, 04:56 AM

The sample-return plans are fascinating. That's why I talk about getting out of ISS, because I'd like to see them take on some meaty challenges like that.

Rayleigh scattering is straightforward math, which Moroz did. Rather than be optimistic or pessimistic, I calculated the effect in a special purpose ray tracer.

The Venera surface images don't tell you much. The horizon is only 50 or 100 meters away, and aerial perspective is already evident. Especially in the color images, where you can see the greenishness of the in-scattering of distant areas.

[attachment=5744:attachment] [attachment=5745:attachment]

Here's an example of calculating first-order rayleigh scattering (a more accurate multi-scattering calculation would look more opaque). Unlike the image I posted a few days ago, I've turned the Venusian atmospheric scattering up to 100 percent. You can see a couple kilometers, but you cannot see the surface from the cloud level.

Now this gets better very quickly with longer wavelength. Rayleigh scattering is proportional to the fourth power of the reciprocol wavelength. So the answer is to just design a long-wave IR camera. Note that the nice images of Titan's surface are all infrared. A possible problem with Venus is that as you go into the infrared, the thermal radiation from the surface might wipe out features. Blackbody radiation varies with reflectivity (how black the body is, literally), but it may be a very bad way to see any features of relief. We will see first-hand if the ESA ever shows us some VIRTIS images!

Posted by: Kodiak May 20 2006, 05:16 PM

Was it a "smart" rover, could it be controled, or was it dumb(preprogramed?) like the Prop-M on Mars-3?(go forward, hit something, backup, turn, go forward.....like todays robotic vaccum cleaners)

Posted by: ljk4-1 Jun 11 2006, 02:22 PM

Speaking of Venus rovers, does anyone else remember the Soviet Venus rover
that battled Steve Austin in The Six Million Dollar Man?

http://cgi.ebay.com/KENNER-SIX-MILLION-DOLLAR-MAN-VESUS-SPACE-PROBE-BIONIC_W0QQitemZ6060373157QQihZ009QQcategoryZ43840QQssPageNameZWDVWQQrdZ1QQcmdZVewItem

Someone actually built one (includes episode synopsis and how a Soviet
Venus Rover actually got back to Earth to menace humanity:

http://www.teamdelta.com/venus/venus-a.htm

Posted by: DonPMitchell Jun 11 2006, 03:36 PM

"Exterminate! Exterrrrrminate!"

Posted by: BruceMoomaw Jun 11 2006, 03:43 PM

I do. (My nephew, who was 8, was watching the episode.) I also remember it was a much better actor than Lee Majors.

Posted by: Richard Trigaux Jun 11 2006, 03:58 PM

Indeed Venus surface is nearly red hot, so we may expect that it is bright in very near infrared. That would still allow us to get IR spectrum (not reflexive, but emissive). Perhaps from the blackbody curve of a given spot we could derive its altitude, and thus obtain an altitude map, but still inaccurate.

This makes that a Venus flyer would need a mapping radar altimetre in more of a camera. And the Rayleight opacity makes that the flyer needs to be relatively close to the ground, and thus heat-resistant.

Posted by: DonPMitchell Jun 11 2006, 04:14 PM

I agree that a low-altitude aerostat would be more interesting that a rover. I think it would be very valuble to just get an idea of the diversity of terrain on Venus. The four Venera surface images show at least three completely different terrains (flat lava field, rolling hills with rocks and soil, and a steep hillside covered with boulders). There are lots of technical problems with a Mars or Venus balloon mission, but then again, landing on the surface has not been trivial either.

For surface missions, a network of seismometers would be intersting, because it would answer questions about the deep structure of the planet. The Russians have already done most of the research on that, and such landers could be small and simple if they do not include cameras and other complex experiments.

Posted by: David Jun 11 2006, 04:16 PM

Obviously, what we need is a giant instrumented yo-yo anchored high up in the atmosphere, that would roll down, take readings/images, and roll back up again.

Posted by: DonPMitchell Jun 11 2006, 04:28 PM

Hehe. But maybe an aerostat would be designed to dive down for short times and then rise up to cool off.

Posted by: Richard Trigaux Jun 11 2006, 04:54 PM

Such a network could do its work in a short time, without need to be heat-resistant, provided that a seism is triggered during this time. But the only way to trigger a seism on Venus is to land an explosive (an impactor would lose its speed into the atmosphere). The problem is that a high charge is required, ten tons or more, perhaps 100 tons.

Otherwise, it is prettily difficult to guess how many times Venus has natural quakes, and how powerfull. To wait for one would require heat-resistant landers.


With my opinion the key of studying Venus is a true heat-resistant probe, able to sustain the full brunt of the surface temperature. THis was discussed earlier in this thread.




It would have so much advantages, the main being that it could see or analyze much more places than a rover.

Also it is so easy to fly on Venus that a rover don't make sense. A very small aerodynamical baloon can sustent an heavy vehicule, and this baloon can be filled with a variety of gasses, some available on the place: water vapour, methane, nitrogen, all this fly very well in Venus C02, and the leak rate is much slower than with hydrogen or helium. (Important, as this leak rate will be much higher at 450°C than on Earth.) Even the envelope is not a problem, a sheet of metal could do the job. The only problem is that common metals will be quickly oxydized by the Venus air, even if it contains only little oxydizing gas (oxygen, S02...)

Posted by: tty Jun 11 2006, 05:55 PM

A nuclear charge in the kiloton range weighs only a few hundred pounds, and that is for a ruggedized charge meant to be shot from a gun.
Incidentally such charges are usually U235-based gun-type weapons since it is difficult to make an implosion-type Pu239 bomb narrow enough to fit into an artillery shell. U235 of course means that the possible contamination from a launch accident would be minimal.

tty

Posted by: RNeuhaus Jun 12 2006, 02:42 AM

It might be a fantasy. I think that the aerobot will have more troubles to try to have a good navigation control than a rover. As I have learned that on the surface, there is very low wind speed, at about 1/2 meters per second but it pushes very hard toward one direction and if the aerobot want to stop there, so, it will need good enough propulsion (helix) to maintain in a fixed point during the scientific mission. Now, the other problem, when aerobot want to cool down, at upper atmosphere has stronger winds and probably some thunderstorms or lightings which is still not well known. The Gallileo fly-by mission has ascuted some strange lightings from Venusian's atmosphere.

I think that before to nominate that the aerobot is the most factible than a rover for a scientific mission, first we need to know much better about Venusian atmosphere. Hope VEX will give some understanding lights in spite of the fact of a big loss from unoperative PFS.

Rodolfo

Posted by: Richard Trigaux Jun 12 2006, 05:51 AM

Yes, this is a problem. But the solution could be, simply, to land. the aerobot can land to observe the ground, otherwise it slowly shifts above it, and can go at higher altitude to have faster winds. Anyway an aerobot won't go very fast, unless it has plenty of power. The reason is that Venus air is very dense, it is like into water. So a baloon-sustended aerobot will be slow.

A solution would be to have the aerobot using a kite (with some gas in to keep it high). This would give some differential wind speed and allow some manoeuver. Or a guiderope, which would maintain it at a constant altitude.

Anyway a lander will have to sustain the full temperature of the ground, otherwise it will be limited to some hours, at best some days. An aerobot will not be able to yoyo fast enough to cool, so we have the same requirement. There could be a high altitude baloon letting descend an instrument case with a rope, but there is now the danger of storm, perhaps tornadoes, hail, lighning, etc.

What I see the best would be an aerobot made of a baloon, but a baloon operating like a submarine ballast: pumping in and out the sustentation gas will allow the aerobot to land efficiently (without being drag by wind) and lift-off when required. But this aerobot would also operate a kite (with some gas too in it) with a wind mill. Wind mills will certainly operate like thunder on Venus, even with slow winds at ground level. If the kite is high enough, it could get better winds. This would give the probe plenty of power without the need for a RTG. At a pinch, a baloon alone could operate a wind mill. When flying, it obtains no power, but when landed, it has plenty.

Posted by: BruceMoomaw Jun 12 2006, 09:18 AM

Lightning seems unlikely to be a problem for cloud-level balloons -- Cassini's much more sensitive measurements during its second Venus flyby showed no trace of radio-burst evidence confirming Galileo's extremely ambiguous earlier results. As for winds: JPL has already done a great deal of study on the complex problem of a balloon trying to use Venus' strong upper-level cloud winds for actual navigation across the planet (which will require using suah an aerobot's altitude control to ascend or descend to different atmospheric layers where the winds are flowing in different directions.)

As for the need for controlled variable buoyancy in such an aerobot: the solution that was devised over a decade ago is considerably more ingenious -- and less wasteful of gas -- than Richard's idea. Describing it here would take a bit too long: see:
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/17307/1/99-0750.pdf
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/30077/1/95-0437.pdf
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/29140/1/95-0375.pdf
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/18329/1/99-1802.pdf
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/27373/1/96-1466.pdf

On the navigation question, see:
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/22393/1/97-0880.pdf
http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/26125/1/96-1155.pdf

And for a detailed discussion of the possible design of such a mission, see
http://www.planetary.brown.edu/pdfs/2056.pdf

Posted by: Richard Trigaux Jun 12 2006, 11:45 AM

My idea was to have a baloon working like a submarine ballast. A submatine ballast compresses air into a reservoir to lower buoyancy, and releases it in the ballast to increase buoyancy. This requires energy, but basically don't waste gas. Anyway it may be possible to have a compact instrument able of extracting some lighter gaz from the Venus athmosphere (steam, neon...)

The solution proposed here is a baloon which alternates short excurtions to the ground with longer stays at high "cool" altitude. The gaz is liquefied at high "cool" altitude, and it evaporates with the heat near the ground. So the atmosphere itself is the energy source which "compress" or release the gaz into the ballast. This solution is certainly smarter to work, it eliminates the need to sustain the ground temp for electronics, but it is much less flexible for a detailed ground operation. With my opinion it will be retained for a first attempt, but further missions should not elude the need for a high temperature ship, able to remain near the ground for a long time, and no more elude the energy source, RTG or better a wind mill.

The mission profile studied here is enough to get some samples of the ground, and have for instance isotopic annalysis or datation. But we want to search for ancient sedimentary layers (in mountains), which could even contain fossils, we shall need an aerobot able to change altitude at will and remain for years near the ground.

Posted by: BruceMoomaw Jun 12 2006, 01:31 PM

There can be no doubt about that at all. The variable-buoyancy aerobot was designed from the start on the assumption that we will not yet have a lander capable of operating for long periods at Venus' surface. If we develop the latter, there will be no need to have it lift high above the surface -- except when we want to rise to a high altitude in order to let the faster winds up there send the craft swiftly to another part of the planet.

One footnote: while some versions of this aerobot use solar cells capable of enduring Venusian surface temperatures to power the craft, other models use a windmill which would be powered by the aerobot's own constant vertical motions up and down through the air. Given the fairly fast descent/ascent speed (and the dense air at lower altitudes), such a windmill could generate quite a lot of power.

Posted by: RNeuhaus Jun 12 2006, 04:09 PM

Probably, the windmill would be the best solution. It is simpler and it would have greater probability to work nicely. However, the windmill will only work if the aerobot is fixed on the land. Otherwise, it would drive crazy. Maybe, with Richard's suggestion is that before using the windmill, aerobot must use some kind of anchor and rope to grasp the Venusian's surface.

Rodolfo

Posted by: DonPMitchell Jun 12 2006, 04:57 PM

The Russians found that light on the surface is too dim for solar cells to be practical. There were three experimental solar cell panels on Venera-11 to Vega. They did develop an RTG for Venus, based on silicon and germanium, and that seems like the best bet. Solar Cells are OK if the balloon flies at a high altitude.

I haven't read Moskalenko's papers yet on Balloon navigation. He was the (largely uncredited) brains behind the Vega balloon system, but I am told he designed a more complex system with controllable altitude.

Given an RTG power supply, another possability for a long-term surface mission is to simply refrigerate a small well-insulated compartment, for any components that cannot operate at ambient temperatures.

Posted by: Richard Trigaux Jun 12 2006, 09:31 PM

I think that a wind mill would be even better than a RTG, technically (besides that Greenpeace would not oppose it, and other political problem, like fitting an american , or worse russian RTG to an european mission.).

The wind mill won't look like traditionnal Earth models, it would rather look like some bulbous turbines used into running water. A large bulb containing a sustentating gas (of constant up buoyancy), blades, a rope attached to the rover, and a wing attached to the bulb to give it an appropriate horizontal position despites the oblique pull of the rope. If the rope is long enough, the wind mill could catch better winds than on the ground. For this the rope could be carbon nanotubes, which will at least achieve this role before being used into the space elevator.

The only problem with the windmill is that it works only if the aerobot is fixed to the ground. The only reliable solution to fix it to the ground is to remove all buoyancy, with a ballast-like compartment. We could try to grastp at the ground, but it can be too flat, or loose (sand).

Another solution to create a negative buoyancy without adding mass would be to compress the air until it becomes liquid. But is this is thermodynamically possible at 450°C?

The solution of a very long cable would allow to use the difference between ground wind and altitude wind, whenever the aerobot is fixed or moving.

This was discussed sooner into this thread. I think it is no, because, thermodynamics dixit, such a refrigerator, working with a very large range of temperature, would be very inefficient, consuming much power. At a pinch, a RTG producing large amounts of waste heat, could be used for certain cycles which consume heat rather than mechanical energy ("fuel fridges" used in regions without electricity).

I did a little presentation of possible solutions for electronics working on Venus, sooner in this thread. There was some interesting comments about searches already done.

Posted by: DonPMitchell Jun 12 2006, 10:54 PM

Venera-D is a Russian mission, not European, so I think their RTGs will fit. I also don't think they care much what Greenpeace thinks. In general, it is not important what they think. That has never stopped NASA or Russia from sending an RTG into space.

Who is thinking seriously now about doing a balloon probe to Mars? ESA and NASA separately?

Posted by: RNeuhaus Jun 13 2006, 02:45 AM

I realized that to develop a factible mill force on aerobot is not an easy task. To nail down on the grownd, the aerobot need a good and smart anchor, the other problem is the weight of anchor, the other problem is a resistant and long rope such as nanotube. It adds some weigth to the aerobot, the other problem is that aerobot must have own navigations controls to maintain in a good direction against the wind so that the mills can provide the maximum output of energy with an proper angle against the wind. The other problem is that aerobot's nose will tend below due to the rope force toward the land. At the end, there are many challenges and they must review one by one on how tthey can be solved completely.

Rodolfo