[X] My Assistant

[Guest_BruceMoomaw_*]

The Titan Organics Explorer design team is now trending toward two alternatives (I think I've mentioned this before):

(1) The more expensive one is a hydrogen-filled blimp with a complex celestial navigation system (apprently usable even on Titan if you use near-IR cameras to observe the Sun and Saturn itself), with two big motors that can be swivelled to drive it temporarily downward vertically for sampling.

(2) The less expensive is a big (and round) wind-driven balloon filled with hot air from the RTG, which would ordinarily hover at higher altitude (about 3 km, versus 1-2 km for the blimp) so that its ground controllers could see in advance if it was being blown toward a region worthy of sampling, after which they'd lower it in classic hot-air balloon fashion by opening a vent. Obviously far less control over landing spots; but the team concluded that it may be acceptable anyway, given Cassini's growing conclusion that Titan's surface composition varies more over long distances than over short ones. (The balloon would also have those navigation cameras, simply to tell the ground precisely where it was at any given time.)

Both these things would descend to within about 100 meters of the surface for 5-10 times over their lifetimes (that number has been downscaled from the previous 20 times), and drop a tiny tripod down to the surface on a line. The tripod would then instantly fire a core tube into the surface, which would then be detached from the tripod and reeled back up into the gondola on the cable. Thus ground contact is required for only a second or two, and there's considerable slack in the cable during the contact.

The point of this mission is that they want to make multiple sampling landings, primarily to look for local spots where liquid water/ammonia lava has been mixed with the deposited organic smog prticles to produce interesting prebiotic compounds that actually contain oxygen. Which mission will be chosen would depend both on cost and on the need for precision landings (the blimp would actually spend about a week quartering each of its 20-km wide landing regions in detail before deciding precisely which spot to land on in it). But if you want to make repeated landings, an airplane or glider is simply out of the question.

Alternatively, if you just want to do aerial reconnaissance (which is another real possibility for the first Titan mission, perhaps accompanied by a stationary lander at one good spot picked out by Cassini), an airplane would be usable, but wouldn't be any more scientifically productive than a balloon with a long lifetime. The trouble -- as with Europa missions -- is that the time gap between Titan missions is so long that you don't want to make any mistakes in designing each mission for maximum scientific output.

[The Messenger]

Thanks Bruce,

Any word on instrumentation? Are they planning on including a Mossbauer?

[Guest_BruceMoomaw_*]

Well, the payload is strictly strawman at this point -- and it's also pretty barebones:

(1) Cameras and air temperature and pressure sensors (naturally).

(2) The main GCMS package to analyze the core samples taken, along with atmospheric samples (also naturally). They definitely want an ability to look for chirality.

(3) A microscope to inspect the retrieved cores of surface ice before they thaw (looking for physical structure, not microbes).

(4) A Raman spectrometer to analyze inorganic materials in the ice cores. This intrigued me; it turns out that they're looking for rocks from Titan's interior that might be ejected onto the surface along with the ammonia-water lava flows that they're looking for.

One can easily envision other things that could be added to this: other types of weather sensors; a near-IR spectrometer for remote surface composition mapping (even given the limited spectral winds through which near-IR sunlight hits Titan's surface); a subsurface radar sounder; a magnetometer to look for induced magnetic fields and thus a subsurface ocean.

[mchan]

Why did you resign?

Bob Shaw

That would be telling.

(since no one else replied)

[Bob Shaw]

That would be telling.

(since no one else replied)

Before anyone objects, this topic is entirely, er, on-topic, being on the subject of a Rover which travels across a beach-like landscape, and has some form of AI!

Be seeing you!

Bob Shaw

[ljk4-1]

Before anyone objects, this topic is entirely, er, on-topic, being on the subject of a Rover which travels across a beach-like landscape, and has some form of AI!

Be seeing you!

Bob Shaw

Using the beachball rover may not be the best approach for finding life on Titan.

The poor things have probably been monitoring Earth television for years, with The Prisoner being their favorite program. Then here comes along a Rover approaching them - they'll all run away or burrow under the methane slush and then we'll never find them.

The blimp may not work any better, as they also have seen Black Sunday.

I am not a number, I am a free Titanian!

[lyford]

DOH - I am sorry Bob - I was too slow. It was even called Rover, ferchrissakes. Well played.
Though apparently I am mistaken, I thought there were measurable winds at the surface of Titan that would aid our little wanderer on its large scale feature hunt.

[The Messenger]

Well, the payload is strictly strawman at this point -- and it's also pretty barebones:

(1)  Cameras and air temperature and pressure sensors (naturally).

(2)  The main GCMS package to analyze the core samples taken, along with atmospheric samples (also naturally).  They definitely want an ability to look for chirality.

(3)  A microscope to inspect the retrieved cores of surface ice before they thaw (looking for physical structure, not microbes).

(4)  A Raman spectrometer to analyze inorganic materials in the ice cores.  This intrigued me; it turns out that they're looking for rocks from Titan's interior that might be ejected onto the surface along with the ammonia-water lava flows that they're looking for.

This is great news! A Raman can evaluate atomic spectra through very fine optical fibers. There is a (slight) possibility I will be able to work on the GCMS package - that is, if they decide they must address the possibility of analyzing tar residues.

[ngunn]

Has anyone suggested a balloon (or a number of balloons) with surface-dragging ballast tail? Small buoyancy changes only would be required to alternate beween 3 modes of operation: 1/ free floating for reconnaissance from altitude, 2/ small part of ballast tail grounded keeping balloon a constant few metres above any undulating surface but able to drift with the wind - photography of the drag trail would yield data on surface consistency over large distances, and 3/ more of tail grounded, sufficient to anchor balloon temporarily at one spot for static surface experiments. No sohisticated navigation or flight control system required.

[EccentricAnomaly]

Nix - a parachute will, after a short while, drift with the wind just like a balloon. If You could invent a parachute that doesn't You would rich, since landing with a parachute in a high wind is difficult and can be dangerous.

Originally I thought a parachute would give you greater range than a balloon, but it's actually the other way around since the balloon stays aloft longer and has longer to drift. I should have said that you have almost zero horizontal velocity wrt the atmosphere.

Also I can't understand where you got the idea that an airplane has less need to predict the atmosphere than a blimp - if anything it is the other way around. Also an aircraft has the same problem as a helicopter - it can never be realistically test flown on Earth.

You can design an aircraft that is inherently stable which will let it survive in worse weather. Also an airplane has greater control authority which means it can tolerate higher winds than a balloon, blimp, or helicopter.

Also it is a much simpler thing to build than a balloon (no inflation, maybe even no deployable parts). And it could be test flown on earth, using what is called the Buckingham Pi Theorem [http://en.wikipedia.org/wiki/Buckingham_Pi_theorem] which lets you build a wind tunnel to approximate Titanian flight just by matching the non-dimensional parameters. You can even account for the lower gravity this way.

[The Messenger]

Also it is a much simpler thing to build than a balloon (no inflation, maybe even no deployable parts).  And it could be test flown on earth, using what is called the  Buckingham Pi Theorem [http://en.wikipedia.org/wiki/Buckingham_Pi_theorem]  which lets you build a wind tunnel to approximate Titanian flight just by matching the non-dimensional parameters.  You can even account for the lower gravity this way.

...Kind of, Sort of. We are still scratching our heads over the the over-performance of the Viking Parachutes; and under-performance of the Pathfinder parachutes; relative to wind tunnel testing of the designs. It will be interesting to see if the modeling [both atmospheric, and structural] has improved to where the Spirit and Pathfinder results are closer to expectations.

[ljk4-1]

...Kind of, Sort of. We are still scratching our heads over the the over-performance of the Viking Parachutes; and under-performance of the Pathfinder parachutes; relative to wind tunnel testing of the designs. It will be interesting to see if the modeling [both atmospheric, and structural] has improved to where the Spirit and Pathfinder results are closer to expectations.

If this helps any:

Viking '75 project: Scale model test results of the Viking parachute system at Mach numbers from 0.1 through 2.6

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1977071083.pdf

VIKING '75 PROJECT: PRE-TEST REPORT FOR FLEXIBLE DECELERATOR WIND TUNNEL TESTS AT AEDC PWT 16S

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._1977071081.pdf

[Guest_BruceMoomaw_*]

This is great news! A Raman can evaluate atomic spectra through very fine optical fibers. There is a (slight) possibility I will be able to work on the GCMS package - that is, if they decide they must address the possibility of analyzing tar residues.

Actually, they intend to use the GCMS to analyze tar residues -- by roasting the hell out of the sample at very high temperatures, since their test runs have shown that a lot of the more complex organics are very refractory and sometimes won't pyrolize until you give them a squirt of oxygen as well to actually burn them. (Which, you'll recall, was what Pillinger's "Beagle 2" GCMS would have done.) They've also found that some of the organics are so sticky that they'll have to use a fresh GC column for every sample, which is another reason why they've cut the total number of surface samples down to only 5 to 10. Indeed, they also chose the Raman for inorganic analyses because it doesn't have to actually touch the possibly sticky sample.

Since these are instrument design strategies, they're likely to be maintained even if the actual Titan mission chosen is nothing like the Organics Explorer -- which is a very good chance. (The design of the Organics Explorer, including its instrument selection, is a strawman exercise to confirm that the idea is workable. Beyond cameras and a GCMS, the actual instrument selection on the next Titan mission is a very wide-open question.)

[RNeuhaus]

You can design an aircraft that is inherently stable which will let it survive in worse weather.  Also an airplane has greater control authority which means it can tolerate higher winds than a balloon, blimp, or helicopter.

If my memory does not fail, the upper skies of Titan has strong storms. Any plane are able to be under a good control during its fly thru any storms. Besides, a plane flying at a distance of 1,500 millions kilometers from Earth, the plane will only fly only for few seconds and hence it will need a very sophisticated Artificial Intelligence to pilot as a good soldier robot obeying any Earth's sent instructions commands. Besides, any plane need to know with advance of any places to land if the emergency arises. We have no good idea what planes is feasible for airplane landing. I won't be thinking an airplane as a feasible for a little known word such as Titan. There is only three good alternatives: Orbiter, Ballon or Blimp or Rover. The Orbiter is a MUST as a communications and spoting support for any motorized on the surface.

Rodolfo

[Guest_BruceMoomaw_*]

Actually, the thinking on a Titan orbiter as a mandatory accompaniment for any suface craft has come under major fire lately -- the redesigns of the Titan Organics Explorer are noteworthy for NOT including one, on the grounds that it would massively increase the mission's cost, and that our technology now allows an aerial vehicle or rover to communicate at acceptably high speed directly with Earth, and to use near-IR cameras observing Saturn and the Sun through the haze layer for navigation accurate to within less than a dozen kilometers. This does raise the problem, however, that such a vehicle can only communicate with Earth when it is on the side of Titan facing the Earth -- which is why the current scenario for the Organics Explorer calls for it to land near the north pole at a time when this will allow it to maintain continuous radio contact with Earth.

I should emphasize that the possible design of the next Titan mission is still extremely flexible -- it may well end up consisting of an orbiter instead of any surface vehicle (or accompanied by only a small nonlanding balloon or stationary lander). But the question is still open.