Mars Sample Return Options

[Rakhir]

Next phase reached in definition of Mars Sample Return mission

http://www.esa.int/esaCP/SEMJAGNFGLE_index_0.html

[RNeuhaus]

A very good article :Returning To Sample Mars, At the recent Viking thirtieth anniversary celebration, Noel Hinners championed what could be the next great challenge for planetary science: a Mars Sample Return mission. Hinners pointed out that, like Viking, Mars Sample Return will prove to be extremely difficult but immeasurably rewarding.

In resume: This mission must be of international cooperation.

Rodolfo

[ljk4-1]

Sample return has been highlighted as a key priority for future planetary missions in discussion meetings held at the first European Planetary Science Congress in Berlin.

http://www.europlanet-eu.org/index.php?opt...6&Itemid=32

Prof. Bernard Foing, Project Scientist for the SMART-1 mission, said, “Europe has now looked at the Moon, Mars and Venus and we have put our finger on Titan. These are great achievements. But for the future, it is not enough to briefly ‘kiss’ the surface of other solar system objects. We must bring them back to Earth for analysis.”

[climber]

Isn't it a coïncidence! Mark Adler is talking about his own experience on the subject on TPS blog today and tomorrow here : http://www.planetary.org/blog/article/00000701/

[spdf]

Funding a Mars sample return mission is not a good idea. This is a very expensive and complex mission. However since the ways to test space technologies on Earth are limited the possibilities are quite high that a Mars sample return cannot be achieved on the first try. Thats the way it is. But I don t think because of the high cost the public and many "space enthusiast" will have tolerance for a failure on the first try. The political climate is simply not right for high risk missions. So imagine the bashing after ... .

[climber]

Funding a Mars sample return mission is not a good idea. This is a very expensive and complex mission. However since the ways to test space technologies on Earth are limited the possibilities are quite high that a Mars sample return cannot be achieved on the first try. Thats the way it is. But I don t think because of the high cost the public and many "space enthusiast" will have tolerance for a failure on the first try. The political climate is simply not right for high risk missions. So imagine the bashing after ... .

If you read what Mark Adler says, he doesn't foresee a MSR before well, 20-30 more years. World will be different then...

[RNeuhaus]

First watch how the russians will be doing by returning the Mars' moon samples with the Phobuss-Grunt spacecraft. Phobus-Grunt is scheduled for launch in 2009. This is indeed cheaper than landing on Mars.

In order to go on on the MRS project be feasible that the man feel highly confident for the success of the project. I think, up to know, we are still close and need about 5-10 years more in order to improve the technology and also to collect money and support from many nations. Up to now, not only russians are doing it but also along with ESA and China.

More details, visit on Phobus-Grunt a Reality? topic

Rodolfo

[Guest_Zvezdichko_*]

First watch how the russians will be doing by returning the Mars' moon samples with the Phobuss-Grunt spacecraft. Phobus-Grunt is scheduled for launch in 2009. This is indeed cheaper than landing on Mars.

In order to go on on the MRS project be feasible that the man feel highly confident for the success of the project. I think, up to know, we are still close and need about 5-10 years more in order to improve the technology and also to collect money and support from many nations. Up to now, not only russians are doing it but also along with ESA and China.

More details, visit on Phobus-Grunt a Reality? topic

Rodolfo

I'm actually quite pessimistic about the Russian Phobos-grunt sampling attempt. Of course, a lot of things have changed since the previous failures, but ... the mission is very ambitious for the current financial state of Roscosmos. Russia hasn't returned samples for more than 30 years ( the Moon ), and the last partially successful mission to Mars was 20 years ago. A Phobos sampling mission requires still untested technologies - Phobos lander, Phobos ascend vehicle. The return capsule will be quite different than these used in the 70s.
And yet, this attempt is worth trying.

[PhilHorzempa]

Recent written comments by Alan Stern indicate that he wants to initiate MSR, Mars
Sample Return, in the near future, perhaps in FY2008.

Also, the National Academy of Sciences now recommends a new approach to MSR.
Instead of one Grand mission, it should be spread out over several years. It suggests
that all future Mars rovers be equipped with a sample caching system. After several
missions, NASA/ESA would decide whcih site held the best samples, and a retrieval system
would be sent. Once the samples were launched into Martian orbit, they could linger there
until an orbital rendezvous vehicle was sent. This would spread the risk and cost over
several years, instead of gambling everything in one Battlestar Galactica mission.

The recent Orbital Express mission has been a pathfinder for an unmanned rendezvous
and docking craft that would be an important part of MSR. However, it's mission is ending
before NASA has a chance to fully utilize it. See the article on this link -

http://www.space.com/missionlaunches/07063...al_express.html




Another Phil


Here is a view from Orbital Express. Imagine that someday, someday this will
be the view from Martian orbit as the Mars Ascent Vehicle closes in for docking with
the Earth Return Vehicle. The background view will be slightly different. We will see
the Martian deserts below, but only empty river channels and rift valleys.






Go to

http://www.darpa.mil/orbitalexpress/mission_updates.html


for more photos.

[hendric]

On the surface that sounds like a good idea, only sending the "retrieval system" to the interesting caches, but I think that would end up being just as complicated as the BSG style missions. The retrieval system would end up requiring rover-like mobility, since it has to reach the cache in the previous mission. It could probably forgo most instruments, but it would still be a large, precision landed rover. It makes more sense to develop a sample return canister/rocket to be taken on each Mars mission, with the rendevous occuring in space instead of on the ground. The space retrieval bus could even collect multiple canisters before returning home.

[Guest_Analyst_*]

It makes more sense to develop a sample return canister/rocket to be taken on each Mars mission, with the rendevous occuring in space instead of on the ground. The space retrieval bus could even collect multiple canisters before returning home.

The return capsule/rocket and "launch pad" is very massive. There is no chance to have every rover carry one. We are talking about several hundreds of kilogramms minimum.

The missions can be spread as described above: (1) landers/rovers to select samples, (2) extra lander to carry sample into orbit and (3) orbiter to escape Mars and return to earth. I strongly doubt this will be more efficient than one single MSR mission. Its hard to integrate, several launches, even more things can fail etc. In the end you need all the same elements. I doubt this will be more cost effective. MSR is a classic flagship mission like Viking or Cassini. I don't see a clever way to change this.

Analyst

[dvandorn]

It all comes down to what you really want out of an MSR mission. Remember, Mars is a fairly big planet as far as rocky planets go. It has a significant gravity well which requires a lot more energy to escape than, say, Luna requires. It also has an atmosphere that gets annoyingly in the way as you try and leave, requiring more energy to achieve orbit from the surface than an airless body would.

So, sending a sample off the surface and back into Mars orbit is not an insignificant operation; it takes more fuel than you'd think. If you include the fuel needed to inject the sample into a trans-Earth trajectory, as well as the heat shielding needed to get it back to Earth intact, you're landing an awful lot of mass on Mars that is dedicated to the return-to-Earth systems. (I'm trying to get y'all used to the idea that an MSR return-to-earth stage on a lander is going to need to be a *lot* bigger, beefier and energetic than, say, the upper stage used by the Russian Luna sample return landers. It's not the "model rocket on a Viking" setup some artists have imagined, it's more like landing a Thor or a Delta on Mars and having it ready to launch with no ground support equipment beyond that you bring with you.)

It would take an Ares V to get such a lander onto Mars with the ability to return more than a few grams of soil and rocks. Such a lander would be so heavy with just the fuel and other things needed to get your sample back to Earth that you'd have no mass left for roving to look for and pick up good samples, much less for a comprehensive survey sensor package.

So, even though it requires three separate launches and spacecraft busses, the concept of splitting the mission into three major pieces -- the survey spacecraft, the surface launch spacecraft and the return-to-Earth spacecraft -- lets you distribute the weight required into pieces that don't all have to be landed and don't all have to support Earth return. Remember, the same booster can get kilograms into Mars orbit that can only get grams onto the surface.

So -- if you want a single scoop of Martian soil, a sample that weighs no more than two or three kilograms, then a single spacercaft architecture is usable. If you want to return tens of kilograms of samples, and not just whatever a scoop can pick up from off the side of the lander deck, you're actually better off with the three-spacecraft architecture. Until and unless we make some propulsion system breakthroughs, it's just not energy-economical to do it with the single spacecraft concept -- not to get enough of a sample back to make the mission worthwhile, anyway.

-the other Doug

[helvick]

I don't think it can be done easily but I don't think the mass penalty is quite that bad. My back of the envelope scratchings based on some Delta-V and typical Isp's from here.

Martian Surface to LMO ~ 4.1 km/sec
Mars LMO to Earth C3 orbit ~ 2.9 km/sec
Total ~7km/sec Delta-V.

To get a 1 kg sample of mars dirt to Earth C3 orbit.
Assume we have motors with an Isp of about 280 (like ammonium perchlorate solids)
Two stages:
(1) LMO Stage - Motor, shell and supports for the mars launch first stage weigh ~ 5kg
First stage then needs ~ 37kg of fuel to get 11kg to LMO ( its own 5kg dry weight plus 6kg for the initial mass of the Earth Transfer Stage)
(2) Earth Transfer stage weighing 2kg dry (container+2nd stage motor+1kg payload+beacon)
Requires 4kg of fuel to produce +-3.1 km/sec Delta-V
Total initial mass = 48kg.

Alternatively.
Single Stage to LMO
Mars Surface to a Mars orbit stable over a couple of years. Say we need 4.4km/sec Delta-V (LMO + some margin) and the dry weight including payload we are working with is ~ 6kg.
Total initial mass = 29kg.

There's lots of holes in these of course (launch stage drag, no earth capture component ... ) but I reckon you can get 0.5-1kg of sample back for <100kg of landed mass. That's not possible today of course but it isn't warp drive level science fiction either.

That said we are limited today to landing something less than a ton or so onto the Martian surface even with the biggest launch vehicles so without something comparable to the Ares V no-one is ever going to return more than a kilo or two.

[antipode]

Drifting a bit OT here, but its obvious to all that MSR will be:

1) VERY expensive
2) Technically risky
3) Possibly providing limited 'bang for the buck' even if it succeeds

Might sample return better be conducted as part of a MANNED precursor mission - one that simply orbits Mars Apollo 8 style (plus visits to Phobos etc). Small surface probes/rovers could then be dispatched from orbit, controlled in near real time etc etc. I know such missions have been proposed, and I'm aware of the objections to them, but MSR is one of those missions that, like controlled fusion, is so hard and so expensive that its always 20-30 years in the future.

P

[Phil Stooke]

Antipode, funny you should mention that, as I am now writing up a description of a mission which includes some elements of what you describe. More on this later.

Phil

[nprev]

Sounds like one of the old Soviet manned Mars mission proposals, IIRC.

[dvandorn]

Such a mission has a lot to be said for it. For one thing, it's easier to send a lot of lab equipment to, say, Phobos than to the surface of Mars, and it's likely cheaper (in terms of energy) to get the mass of the equipment you want to use to study Mars rocks to Phobos than it is to bring the rocks all the way back to Earth.

So, you set up a manned microgravity habitat on/in Phobos, outfit it with the best analysis tools you can easily get out there, and send down small sample return probes that bring you up a few kg of carefully selected rocks and soils every few months. Your PIs live on Phobos and send the detailed data back to colleagues on Earth.

What would be the minimum lab requirements for a Phobos geological analysis base? You'd want to have fine-scale composition and isotope analysis, as well as the best rock dating equipment you can afford to transport. You'd also want equipment for examining micro-fossils (just in case) and for examining ices and such for possible biological activity or remnants.

What suite of instruments would best serve your purposes in such a set-up? What are their power requirements? And how much of it can be feasibly transported via rocket from Earth to Phobos? Those are the questions I'd be asking right now...

-the other Doug

[helvick]

One fairly big problem that I see with the idea though is that the stuff that you loft up from the Martian surface would also have to land on Phobos and do so incredibly precisely and without damaging your lab. That's pretty hard if you ask me - It seems to me that it would be a lot easier to send stuff all the way back to Earth. The Delta-V difference between "Mars-Surface to landed on Phobos" and "Mars-Surface to Earth C3=0 orbit" is only 1.5km/sec.

[tty]

So, you set up a manned microgravity habitat on/in Phobos, outfit it with the best analysis tools you can easily get out there, and send down small sample return probes that bring you up a few kg of carefully selected rocks and soils every few months. Your PIs live on Phobos and send the detailed data back to colleagues on Earth.

It seems to me that the most efficient way to use a manned outpost on Phobos would be to search for bits and pieces of Martian rock on Phobos itself. Nearly every large impact on Mars must have caused some debris to end up on Phobos. You could do the preliminary selection and analysis on Phobos and send the most interesting bits back to Earth for detailed study. In this way it should be possible to get at least a rough outline of Martian historical geology and also "ground truth" data to interpret orbital imagery.

Another fairly simple and cheap, though very limited form of sample return would be to expose a Stardust-type collector during aerobraking and returning it using a small Earth-return stage.

[gpurcell]

Another fairly simple and cheap, though very limited form of sample return would be to expose a Stardust-type collector during aerobraking and returning it using a small Earth-return stage.

SCIM has been proposed in the last two Scout competitions and would follow that mission profile.

[mchan]

Such a mission has a lot to be said for it. For one thing, it's easier to send a lot of lab equipment to, say, Phobos than to the surface of Mars, and it's likely cheaper (in terms of energy) to get the mass of the equipment you want to use to study Mars rocks to Phobos than it is to bring the rocks all the way back to Earth.

So, you set up a manned microgravity habitat on/in Phobos, outfit it with the best analysis tools you can easily get out there, and send down small sample return probes that bring you up a few kg of carefully selected rocks and soils every few months. Your PIs live on Phobos and send the detailed data back to colleagues on Earth.

Would it be cheaper to bring the rocks or the PIs back to Earth? The PIs are coming back, right?

[dvandorn]

Well, it depends... the PIs have to get their results published before they can come home, after all...

-the other Doug

[centsworth_II]

Publish or perish?

[dvandorn]

Literally!

-the other Doug

[lyford]

[Guest_AlexBlackwell_*]

Mars Mission May Be Moved Up
By Frank Morring, Jr.
Aerospace Daily & Defense Report
July 6, 2007

[ustrax]

Didn't know where to put this...

"Let's get this done ... make some history," Stern concluded.

This is how I like to hear them talking!

[gndonald]

Antipode, funny you should mention that, as I am now writing up a description of a mission which includes some elements of what you describe. More on this later.

Phil

Was this by any chance the 'Mars Twilight Flyby' that NASA was planning in 1966?

As I remember the documents I looked through the plan was to fly past Mars, drop off six probes (1 orbiters, 3 hard landers & 2 soft landers), one of which would rocket into orbit a capsule containing a Mars rock/atmosphere sample and film from a high resolution camera for pickup by the manned flyby craft.

On the way back the astronauts would analyze the surface samples and beam the results back to Earth.

[Phil Stooke]

gndonald:

"Was this by any chance the 'Mars Twilight Flyby' that NASA was planning in 1966? "

No. It's about Phobos, and has evolved into my abstract for the Phobos conference.

Phil

[JRehling]

[...]

[nprev]

I get your point, JR. In all fairness, though, there does seem to be some precedent for the strategy. Ranger/LO/Surveyor were all precursors to Apollo, so since Mars is the espoused future goal for US manned exploration it's getting the lion's share of UMSF attention.

Not necessarily saying it's the right way to go, but merely speculating on the apparent reason for the focus.

[Pavel]

I think you missed the "far into the future" part. Mars sample return is going to be harder than the current missions, and it's likely to take a lot of time. And it can fail like any other mission, for technical or monetary reasons. We can get into the situation when specialists are waiting for additional financing, and there are no working rovers on Mars. The sample return mission is just too big for the pipeline now.
A think we need an "entry" strategy - how to implement ambitious missions efficiently, so that we don't end up with another over-expensive and unsustainable Apollo-like program.

[JRehling]

[...]

[Pavel]

Mars is also special because it the easiest extraterrestrial planet to research. Try getting samples from Mercury or Venus. Now that would be hard!

The Moon and asteroids are easier, but some questions can only be answered by researching planets. Mars is a natural stepping stone for planetary research. We may learn enough about Mars at some point, but the technology developed for Mars will be reused for other celestial bodies.

A massive one-off project would be less useful for further exploration than smaller specialized missions. MER-like robots can be driving on Europa one day.

[Jim from NSF.com]

I don't think we want a sustainable program. Not a sustainable big program. That implies money pit to me.

The people doing research on liver cancer don't want a sustainable liver cancer research program. They want to cure liver cancer. Research is the means, not the end. I personally would like to see research on liver cancer end -- once they cure liver cancer.

excess quoting removed

Nonsense.
Liver cancer will continue after one cure has been found. The cure may be expensive, lengthy etc
We know how to set broken bones yet research continues and better "cures" are the outcome

Has ocean research finished.

Not until there is a human presence on Mars, will the missions end. Strike that, there may be Martian weathersats.

[spdf]

A question here: If you have a ~30-40 kg small satellite and you want to launch it from mars surface into mars leo, how much energy do you need for it? And how big would be the rocket? Is there any more detailed study on this online?

Thanks

[ElkGroveDan]

A question here: If you have a ~30-40 kg small satellite and you want to launch it from mars surface into mars leo,

not sure, but I think you'd first want to launch it in lmo

[helvick]

You can find some of my back of the envelope calculations on that question in an early post in this thread ( here )
The delta-v that you need is 4.1km/sec to from the martian surface to LMO. Assuming you're using an engine with performance similar to an ammonium perchlorate solid motor (ie an Isp of around 280), then you will need at least 135kg of fuel. You will need an actual launch shell to put it all in which would add another 10-20kg + another 30-60kg of fuel to cope with that extra initial mass.
Note I've made no allowances for atmospheric mass here and that will be significant even though the martian atmosphere is not very dense.
Excluding drag you are talking about an initial mass of at least 215kg to get 40kg to LMO.

And finally you need a (martian) ground assembly to hold it all before launch and I've no idea how to estimate how massive that might be.

[nprev]

And finally you need a (martian) ground assembly to hold it all before launch and I've no idea how to estimate how massive that might be.

I would assume that the return stage would be integrally mounted to the descent stage in the proper configuration--pointy end up, propellant loaded-- before Earth departure; physically configuring it for launch on Mars in any significant way seems really risky from a technical standpoint. Still, lots of mechanical complexity needed to put the payload aboard, unless it's a simple scoop...

[JRehling]

[...]

[monitorlizard]

I'm probably going to get my head handed to me for saying this, but can't a case be made for a Mars sample return with a direct Mars to Earth trajectory, bypassing a rendezvous in Mars orbit with an Earth return stage?

The obvious counter to this idea is that the size/weight of the Earth return rocket on Mars would be MUCH larger than that needed to reach low Mars orbit. OK, agreed. But there are a lot of advantages to direct to Earth launchings from Mars. One: A Mars orbiter to receive the sample canister wouldn't be needed. That eliminates an entire launch from earth and an entire spacecraft. Two: No need for a rendezvous in Mars orbit. This is an extremely complex operation to do unmanned, and I think it is the pacing technology for when a sample return could be done. It also raises the cost of the mission enormously.

The alternative is to launch a single massive spacecraft to Mars, have it collect and store samples by whatever means is preferred, wait until the next alignment of earth and Mars, then launch the sample return spacecraft directly to earth (no orbiting Mars first). This would require the use of a much larger launch vehicle from Earth than a standard sample return scenario, but that cost would be offset by requiring no Mars orbiter launch, and the much greater simplicity of the Mars to earth portion of the mission (which should also reduce costs greatly and, more importantly, give a greater chance of success).

I've made my case, let the carnage begin.

[djellison]

Well - yes - carnage indeed. Instead of a 5kg litle satellite to launch from the surface - you have to land, and then launch again - a much larger launch vehicle, to launch not only the small sample cache but also a complete, fueled, spacecraft and entry capsule - able to not only enter the Earth's atmosphere at the other end - but navigate with TCM's between Mars and Earth. A full up proper spacecraft - perhaps 100kg (complete guess). Landing and then launching your return capsule is not easier.

You're making the requirements of the MAV an order of magnitude larger - and thus the landing requirements an order of mag larger (when we don't know how to land >750kg on the surface) and thus the first launch vehicle from Earth being an order of magnitude larger....which doesn't really exist

I think from a biohaz perspective (even if it's just paranoia) - taking a small cache from orbit, putting it into another large entry capsule that is then sealed makes a lot of sense. If you have the entry capsule on the surface, you've exposed it to the Martian environment as well.

I can perhaps see the case for single launch - a viking like split between lander and orbiter, and then then a re-rendezvous on orbit for the return to Earth - but taking EVERYTHING you need to get from Mars back to Earth ( a complete spacecraft) all the way to the surface and back makes the entire problem much more difficult than it needs to be. Also- orbit rendezvous and return offers the option for multiple samples collected and launched from multiple sites to be returned via a single orbiter.

[monitorlizard]

Thanks, Doug. I knew I was going to be defeated on this, but reading the details answered a lot of questions I had.

[djellison]

It's not 'defeated' - I mean, there's merit to making as few manouvers in the system as possible. If you could make a spacecraft with the necessary Delta V and entry ability to do the Mars to Earth flight - but <10kg - perhaps it could be done - but I'd want my return vehicle to be very big, very reliable, and packed full of redundent systems.

Doug

[Cugel]

Of course the points Doug mentions are valid and pretty serious drawbacks for the Direct-to-Earth approach.
However, there is (at least) one point in favor for it: ISRU, aka the Zubrin Fuel Processor.
By far the greatest part of the mass of the return vehicle must be fuel, so if you can somehow land with empty tanks and then do a refill the whole plan makes more sense. You probably can't do DTE without ISRU. But even in a split mission approach ISRU could perhaps be an interesting option.

There is also another issue with the split mission architecture. Is it really possible to automatically rendezvous with a completely passive cannister? Something that doesn't have a radio, position control, an energy source, etc... How do you know its orbit with enough accuracy? But if it can't be a passive cannister, how much hardware must be added before you can find it in orbit? What does that do to that 5 Kg mass number?
Actually, I don't believe in such small numbers, it will probably be more like 100 Kg. At least.

[djellison]

I think a sample cache cannister would have a small battery and a beacon radio.. It'd be interesting to know how much intelligence was required on the 'dumb' part of the recent DARPA orbit rendezvous demos when doing the automated undocking and redocking.

Here's a thought. You could make your sample cache a derivative of a cube sat.

Doug

[Cugel]

A cube-sat? Hmmm, I believe at Delft University (Holland) they actually are developing something like that called a nano-sat. As I recall it was 30 cm. (12 inch) on each side, or something. (And it carried a radio) I will see if I can find some more information on it.

[djellison]

Cubesats are a well established and popular platform ( you'll even find extensive info about them here )

It's 10 x 10 x 10 cm and no more than 1kg

You can extend the platform into a double or triple cubesat ( 10 x 10 x 20 and 10 x 10 x 30 , 2 and 3kg respectively) for added performance.

Doug

[Cugel]

So I guess the 'cannister' could look something like the Delfi-C3 nano-sat

This one doesn't have active attitude control, but that's basically all it's missing for being a perfect MSR cannister. Work is also being done to develop autonomous rendezvous, where nanosats would catch up with big satellites for maintenance or repair. This cube-sat development could really be extremely useful for MSR architectures!

So, I'm willing to lower my bid to 10 Kg!
2 Kg of samples.
5 Kg for the standard cubesat bus
3 Kg for attitude control, thrusters and a docking mechanism.

[nprev]

This may be WAY off base, but has anyone considered a purely ballistic MSR mission profile?

What I'm thinking of here is a single-stage (or two at the most, if the upper stage has robust thrusters & agile nav capability) DTE reentry vehicle from the surface of Mars...minimal course correction requirements, tight launch window, maybe even solid-fueled at least for the initial boost phase. Advantages: Relatively simple G&C. Disadvantages: (1) very tight launch window, (2) probably high velocity wrt Earth for entry phase. Don't know without a formal risk analysis how these very coarse factors would play out, nor whatever other dragons there may be.

(BTW, thinking of grams, not kilograms, in terms of sample return quantities: even a very little bit of Mars would go a long. long way in terms of answering fundamental/nagging questions such as the presence or absence of superoxides, carbon abundance/source, iridium ratios, etc., etc., ...)

[The Messenger]

Good question. Solid fuels have a great track record in space...I think there has been one possible failure in 300+solid propellant motor ignitions in the vacuum of space.

[tty]

Solid fuels have a great track record in space...I think there has been one possible failure in 300+solid propellant motor ignitions in the vacuum of space.

I gather you aren't including the spin/despin rockets of the early Corona recce satellites which went bang in a disconcerting number of cases.

[djellison]

Or the CONTOUR kick stage

Doug

[Jim from NSF.com]

Or the two HS-376's on PAM's of STS 41-B

Or the IUS on STS-6

[nprev]

Hmm. Doug & Jim, if you had to shoot from the hip, would you favor liquid or solid propellant for an MSR return vehicle? Expanding on that, do you think that a DTE strategy would be better than, say, a Mars orbit rendezvous with a return vehicle? Seems as if there might be some significant risk analyses needed to make the best possible decision, but interested in your thoughts.

[John Whitehead]

Here are some comments about "how to get off of Mars" for an affordable sample return mission. We really are talking about a miniature launch vehicle. Mars ascent is far more difficult than any rocket maneuver ever done except earth launch, while Mars ascent needs to be done with about one thousandth the mass of earth launch vehicles.

A Mars ascent vehicle needs to be about 75 percent propellant, e.g. 4200 m/s at 310 seconds Isp. If the rocket stage without payload is 80 percent propellant, then the whole vehicle has to weigh 16 times the payload (12 parts propellant, 3 parts stage hardware, and 1 part payload has the 75% and 80% ratios). If the rocket stage can be as good as 90 percent propellant, then the whole vehicle weighs only 6 times the payload (4.5 parts propellant, 0.5 parts stage hardware, 1 part payload). Much better.

For example, a 20 kg Mars ascent payload means that 80-percent rocket stage technology results in 320 kg launching off Mars, while 90-percent technology needs only 120 kg. That's likely the difference between "not possible" and "possible," given forseeable sizes for Mars landers. I believe the latter can actually be done, if the avionics and batteries can be squeezed into the 20-kg payload allocation -- the rocket engineer perspective on what constitutes payload .

So the scale (and therefore cost) of the entire Mars sample return mission depends very strongly on the relative masses of propellant and stage hardware, which in turn is limited by the strength of metal and the difficulty of miniaturization. Whole stages of earth launch vehicles are 90 percent, but there is no precedent for achieving such high numbers in the 1-ton range, let alone on a 100-kg scale. While the above analysis assumes one stage, and multiple stages make it easier in theory, the miniaturization challenge is even more difficult for an upper stage.

Existing flight-qualified solid rocket motors on the scale of interest (~100 kg) are about 90 percent propellant, so it is very tempting to think the problem is solved. However, it is necessary to add directional control. The extra parts could easily over-burden a Mars ascent vehicle. A useful technology development effort might be to build and test-fly a series of small solid rocket stages, all the while working to reduce the auxiliary weight.

For liquid propellants, entirely new custom hardware would have to be developed, because liquid propulsion parts used on satellites and spacecraft are too large and heavy. One possibility for reducing hardware weight is to use a pump-fed engine like launch vehicles do. The principle is to reduce tank weight by making the walls thinner (low pressure), while making the engine more compact (and less massive) by running it at high pressure.

The organizations that build spacecraft propulsion systems have not been asked to design rockets completely from scratch since about 1970 (perhaps a few exceptions), and launch vehicle organizations only build big things. A learning curve should be expected. A bit of good news is that building a Mars ascent vehicle promises to be a very exciting project to inspire the next generation.

John W.

[monitorlizard]

mepag.jpl.nasa.gov/Announcements/Stern_MEPAG_Summary.pdf

The above has a summary of a meeting between MEPAG scientists and Alan Stern on September 24. It sheds a little new light on Stern's thoughts about an MSR, as well as the MSL descopes, and the 2013 Mars Science Orbiter. He actually makes a 2020 MSR mission seem feasible, even affordable, with the sacrifice of one Mars opportunity mission. Both sides brought out new points I hadn't heard officially before. Worth checking out.

[John Whitehead]

Thanks to monitorlizard for pointing out the Sep24 MEPAG meeting notes with Alan Stern. To summarize the key points that I noticed regarding MSR:

1. The notion is that skipping one Mars launch opportunity next decade would save enough money to develop and launch MSR in 2020.

2. Planning for science, mission architecture, and curation (sample handling in Houston) are proceeding.

My analysis:

MSR needs two large spacecraft: a lander that carries the Mars Ascent Vehicle (MAV), and an orbiter that carries the Earth Return Vehicle (ERV). Either of these alone is most likely a heavier and more expensive spacecraft than the one single science spacecraft that would be sacrificed in order to pay for MSR. It doesn't appear to compute financially.

Maybe it will be affordable if the 2009 MSL lander works like a charm, and is just copied without new lander development. Then the challenge is back to building a very small MAV, and likely also a new ERV that is small enough to send to Mars orbit in the first place.

All this says that aggressive innovation in down-sizing propulsion technology is needed. Meanwhile, mission architecture studies (number 2 above) can easily have big errors in the estimates of mission mass (and cost) in the absence of the rocket technology.

We have to hope that the science community will appreciate the need for high-risk rocket technology work. There's essentially nothing out there that can be bought and modified or adtapted in order to successfully launch off of Mars.

John W.

[Jim from NSF.com]

One possibility for reducing hardware weight is to use a pump-fed engine like launch vehicles do.

Not viable. Losses from inefficiencies would be too great. Pressurized systems is the way to go

[monitorlizard]

"There's essentially nothing out there that can be bought and modified or adapted in order to successfully launch off Mars"

That may very well be true, but there's one possiblity I can think of that might just barely do the job: the ASM-135 ASAT antisatellite weapon that was successfully tested in 1985. It was a two stage (solid propellant?) rocket, with a third stage that I think was just the kinetic warhead itself. The first stage was taken from the Boeing AGM-69 SRAM cruise missile (specifically the Lockheed SR75-LP-1), and the second stage was the Vought Altair III. The third "stage" featured a hydrazine attitude control system to allow a direct hit on the target. Such a control system seems to fit well with the requirements for a rendezvous in Mars orbit with the Earth-return vehicle. (all facts taken from Wikipedia)

The ASAT missile was launched from an F-15 at around 85,000 feet, which is like having an extra stage for your rocket, but I'm wondering if the lower gravity at Mars might make it possible to launch from the surface without an extra stage. The ASAT was described as being able to reach altitudes greater than 350 km (the satellite it hit in 1985 was at 555 km), which seems more than adequate if used at Mars. The weight of the entire ASAT missile was 1180 kg, which seems within the range of possibility for an MSR mission.

I have no idea if such a rocket could actually be used for an MSR, and it might need to be so highly modified that starting from scratch might be better, but I think this is the only already-built system that could meet the weight and performance specs needed. It would be a great sword-to-plowshare moment if it could be used. If MSR is a joint mission with ESA, it could be an ITAR nightmare, but this is supposedly a retired system.

[monitorlizard]

Rats! I see I'm off by a factor of ten in the weight of the MAV envisioned for an MSR. Pity. I was thinking like a Soviet engineer in the 60s.

[John Whitehead]

"Jim from NSF.com" noted earlier today that a pump-fed minature launch vehicle may not be viable due to inefficiencies. That's probably true if miniaturization is attempted for centrifugal pumps powered by turbines (aka turbopumps).

Tests on a positive displacement miniature pump indicate that only 2% of the total propellant would provide enough power to run fuel and ox pumps, which is efficient enough. See JPL's Mars Technology Program website for a synopsis at (hope it's still there):
http://marstech.jpl.nasa.gov/content/detai...amp;TaskID=2289

It's agreed that pressure-fed propulsion is nice and simple and reliable, but you end up having to make tank walls thicker and heavier than you would like them to be, and also engines larger than you would like them to be. For decades, people have envisioned pressure-fed liquid launch vehicles to get off of earth (Bob Truax, "Big Dumb Booster," Beal Aerospace, Microcosm, etc.), but so far none has succeeded. Even using the strongest materials (carbon fiber), the stages end up being closer to 80 percent propellant than 90 percent, and that makes all the difference (in displacing payload with rocket hardware, or in requiring the whole vehicle to grow huge for the same payload).

Regarding monitorlizard's comment about the 1985 ASAT test rocket, the altitude it reached does not necessarily indicate capability to attain orbit (earth or Mars). Reaching orbit requires velocity in addition to altitude. NASA's goal for Mars sample return is to park the sample package in a circular orbit at 500 km altitude. Given only a quarter of orbital energy (half the velocity), it's possible to launch straight up to 500 km (sort of like the ASAT rocket did), but then you fall straight back down again.

"Soviet engineer in the 1960's," is an especially appropriate comparison since their return vehicles that launched off the moon (Luna 16, Luna 20, and Luna 24) weighed about a metric ton. The Mars ascent vehicle has to be a tenth that mass, and just to get to Mars orbit it needs a much higher velocity (4200 m/s) than going from the moon all the way to earth (2800 m/s, which the Soviets did nicely using only one rocket stage).

Great discussion!

John W.

[nprev]

It seems that for sake of economy and simplicity a solid first stage would be ideal. However, I can't think of anything else but a liquid-fueled (hypogolic?) second stage to achieve orbit; it has to have a throttle & restart capability, esp. if the first stage under- or over-performs, and of course to circularize the orbit. Perhaps pressure-fed tanks controlled by valves alone would overcome the pump problem; pressurize the hell out them with Martian air before launch, then leave the feed pumps on the surface...

Not even touching the autonomous G&C requirements here. This will not be easy.

[monitorlizard]

I concede now that I was way off with the ASAT idea. It just seems a pity that the Air Force has so many missiles of different sizes and ranges but none seem to be usable as the basis for an MAV.

As long as I'm throwing crazy ideas to the crowd... What if instead of thinking in terms of a 1 kg or larger Mars sample , we go much smaller, say ten grams. Someone has already pointed out here that you could extract a huge amount of science from such a sample size. So you get maybe a small pebble and a little soil. Now the MAV can be smaller, though I admit you still need the same guidance systems, attitude control, radio beacon, etc. (maybe some systems could be made slightly smaller in proportion to the smaller capsule needed for the sample).

Using a balloon to raise an MAV to an altitude of several thousand feet would be a way to make the MAV even smaller, acting as a sort of first stage for the rocket. I don't know how the trade-offs would compare, but if everything were of minimal size, it might be doable. I know it probably seems unnecessarily complex and not worth the effort, yet the U.S. Defence Department studied this very same concept before Sputnik as a way to achieve Earth orbit before the Soviets.
Maybe the fact that they never did it should tell me something.

[djellison]

Using a balloon to raise an MAV to an altitude of several thousand feet would be a way to make the MAV even smaller,

And also a way to make the MAV far more complex that it ever need be. Balloon's are not great on Mars. The atmosphere is so thin that you would have to have an ENORMOUS balloon to get something like this aloft - and you still have the far from trivial issue of launching from a balloon, particularly w.r.t. orientation for launching. A comparatively simple solid fueled two stage MAV with a cube-to-nano sat sized payload with a radio beacon of some sort - keep it as simple as possible. If you send a mid-scale rover in advance to get samples - then an MSL-scale lander could house both the MAV, and a contingency sample gathering micro-rover. The hard part is the on-orbit rendezvous - and how to convince people that you've got the samples very very tightly locked up.

Doug

[John Whitehead]

You're right, nprev, that a solid first stage is very attractive. NASA's reference design concept for a MAV has been a 2-stage solid more or less since about 1999. The good news is that solid rocket motors on the scale of interest (100 kg give or take a factor of 2) are existing technology, and they are a whopping 90 percent propellant. However, there's devil is in the details. The thrust of such small solid motors is way more than is needed. It would reach high speeds while still low in the Mars atmosphere, so there's somewhat more aerodynamic drag than for a liquid MAV. Worse, perhaps, is that the high thrust also requires the directional control system to be larger and heavier than would otherwise be needed, and control must be very responsive (quick) to steer correctly for the 20 seconds or so before the first stage motor burns out.

Solid motors and their payloads are usually spinning when used for space maneuvers. Launching a spinning MAV would require the lander to have a spin table rigidly anchored to the ground so it doesn't start wiggling when the MAV is spun up. The landing orientation cannot be guaranteed, so the launch platform would require tilt adjustments on two axes, and then still be rigid when it starts spinning. How to design such a lander or estimate its weight to compare with other options? A spinning MAV was considered at NASA in 1998-1999 and ruled out.

Pressurizing the "heck" out of tanks and leaving the pumps on Mars is not a solution because the high-pressure tanks would be way heavier than pumps.

You hit 2 nails on their heads, monitorlizard.
1. There are so many different kinds of rockets and missiles out there, that it is way too easy for the "collective consciousness" to assume that it is possible to just go and buy something that can launch off of Mars. Therefore there has been no NASA (or ESA) money dedicated to aggressive technology development, most likely necessary.
2. Minimum size for avionics is really what determines the smallest MAV. Who wants to make the agonizing decision about how much telemetry to put on board? If it doesn't reach Mars orbit, how much data is needed to know why the multi-billion dollar mission failed (the painful lesson from Mars Observer 1992).

Rising through the atmosphere with a helium balloon before launching the rocket would be the ideal way to get off of Venus, if only the balloon could be kept from melting.

So for Mars ascent there are several possible solutions, none of which is existing technology. Ideally, some amount of engineering effort (building and testing things) would be affordable for each candidate, to help sort out what makes sense to pursue further.

John W.

[Jim from NSF.com]

Pressurizing the "heck" out of tanks and leaving the pumps on Mars is not a solution because the high-pressure tanks would be way heavier than pumps.

But not too heavy for a MAV

[nprev]

The good news is that solid rocket motors on the scale of interest (100 kg give or take a factor of 2) are existing technology, and they are a whopping 90 percent propellant. However, there's devil is in the details. The thrust of such small solid motors is way more than is needed. It would reach high speeds while still low in the Mars atmosphere, so there's somewhat more aerodynamic drag than for a liquid MAV.

John, I admit my ignorance with respect to propellant chemistry, but would it perhaps be possible to formulate a solid fuel mixture that would provide adequate--well, the correct amount is what I really mean--thrust for Martian conditions? Seems easier than designing the MAV for different (and possibly quite variable) atmospheric conditions with COTS booster thrust as a constant.

[John Whitehead]

John, I admit my ignorance with respect to propellant chemistry, but would it perhaps be possible to formulate a solid fuel mixture that would provide adequate--well, the correct amount is what I really mean--thrust for Martian conditions? Seems easier than designing the MAV for different (and possibly quite variable) atmospheric conditions with COTS booster thrust as a constant.

nprev, I'm happy to admit I'm not a solid rocket expert. But when I've asked solid rocket experts, there is no definitive answer to this question. I fall back on George Sutton's book. Thrust is determined by total mass flow (of burnt stuff), which is proportional to the exposed area of the propellant grain, times the regression rate of a given propellant. Smaller motors have a higher ratio of burn area to propellant mass, hence short burn times. Burn area relative to volume can be reduced by making the solid motor long and skinny, an "end burning" propellant grain. Then how does that package up as a MAV stage (bending modes, more inert wall mass, and it doesn't fit in the spacecraft on the way to Mars).

How do you make a mixture of fuel and oxidizer burn slower? The best of my understanding is that you have to dilute it with something, i.e. lower temperatures, lower Isp, lower exhaust velocity. I wish the rocket companies would publish a paper or advertise their capability to produce low-thrust solid motors. My personal bet is that it's not going to happen.

[nprev]

Thanks, John.

Hmm...sounds like a real challenge in systems engineering...so many interdependencies! I've got some former classmates still looking for thesis research topics; this sounds like a goodie. Will see if anyone's interested.

[tty]

Burn area relative to volume can be reduced by making the solid motor long and skinny, an "end burning" propellant grain. Then how does that package up as a MAV stage (bending modes, more inert wall mass, and it doesn't fit in the spacecraft on the way to Mars).

That ”long and skinny” comment is interesting. About the only existing solid rocket motors in the correct size class are for BVR AAM’s, and these tend to be “l,ong and skinny” both for aerodynamic reasons and because they do have fairly long burn times (=fairly long flight times). Perhaps a derivative AIM120 engine might be suitable for a first stage? As for control thrust-vectoring is used in modern AAM’s, though usually only in agile short-range missiles. So most of the technology does exist, but not in a form that is immediately usable.

[mcaplinger]

even a very little bit of Mars would go a long. long way in terms of answering fundamental/nagging questions such as the presence or absence of superoxides, carbon abundance/source, iridium ratios, etc...

Many of these questions could be far more cost-effectively answered with in situ measurements than by sample return, and some of the others could be answered by a much simpler SCIM-type mission. And some we more or less know already from the SNCs.

Frankly, because of the fundamental energetic difficulties and the valid-or-not "Andromeda Strain" concerns, I'm a little surprised that people are still seriously talking about Mars sample return as a likely mission for the foreseeable future.

[hendric]

There are some hybrid rockets, that have a solid fuel core and a liquid oxidizer. I believe the SpaceshipOne rockets were of this type provided by SpaceDev. They have throttleable and restartable rockets. So only one pump needed:

http://www.spacedev.com/spacedev_hybrid_prop.php

[John Whitehead]

That ”long and skinny” comment is interesting. ...control thrust-vectoring is used in modern AAM’s, though usually only in agile short-range missiles. So most of the technology does exist, but not in a form that is immediately usable.

Yes I suspect an off-the-shelf AAM motor would not have the required propellant fraction, and I agree with the intended meaning of that last line. It raises a key consideration which might sound like semantics, but bear with me. In the world of solid state advances (computer chips etc.), having "the technology" in hand often means something completely unrelated to "how heavy is the final packaged product." We are surrounded by the notion that implementation and technology are separate things. However, in the world of high performance rockets, the question of whether the hardware is lightweight enough is really not a separate issue. The weight is the main problem that needs to be solved. Most flying things that exist have already been evolved to a practical limit of least weight, given material strength versus the stress loads from internal pressure, thrust, flight vibrations, etc. Can we start with an existing solid stage that has directional control, and carve out a third or a half the weight? If we succeed at doing so, did we have to make innovations along the way that could rightly be called "new technology"?

Offered as food for thought.

In all cases of evaluating what might work for a MAV, the most concise answer to the question is a mass budget for the vehicle, initially supported by calculations showing realistic departures from proven capability, and ultimately supported by a complete design and a working vehicle that meets the need for delta V.

John W.

[nprev]

Hate to even bring this up, but it sure seems like we might need to fly a pathfinder technology demonstration mission before committing to the real deal...and the nasty part here is that there's no place to do it & gain any value at all in engineering terms but Mars itself.

Aside from the truly formidible problems of designing a MAV, there are a bunch of other systemic complexities and event dependencies to consider, far more IMHO than in any other UMSF effort to date. I wonder if a high-risk Discovery-class mission could designed to send a few grams back of any random Martian surface material as a bonus; the real value would be assessing the performance of all these subsystems.

[John Whitehead]

But not too heavy for a MAV

If the pressure-fed versus pump-fed question is to be debated, then mass budgets need to be compared. Descending down one layer into what determines the mass budget, one key question is how heavy are the tanks relative to the propellant they contain? Is there stored gas on board to push the propellants out, and how heavy are the extra tanks (or extra tank volume) for storing the gas?

Regarding the earlier suggestion to fill it up with Mars atmosphere then leave pumps on the ground, note that the Mars atmosphere is carbon dioxide, which is 11 times as heavy as helium. A good rule of thumb is that the best aerospace pressure vessels flying today can contain 1/4 of their own weight in helium. Or to put that a different way, the helium needed weighs only 1/4 of the vessel. If carbon dioxide were to be used instead, it would weigh more than the propellant tanks and gas storage vessel(s) combined. What does this look like on the mass budget?

Back in 2001, NASA funded 3 companies to go and design Mars ascent vehicles. The results, made public by AIAA paper number 2002-4318, were:
Lockheed-Martin, 268 kg solid rocket
TRW, 254 kg gel propellant rocket
Boeing, 400 kg pressure-fed liquid bipropellant (hypergolic)
These numbers don't count the mass of essential hardware that remains on Mars, just to support the launch.

The pressure-fed liquid was the heaviest option, and in recent years, all three have been considered too heavy to do the MSR mission within the Mars science budget. All this leads to the conclusion that it's really a nitty-gritty technology problem that is unlikely to be solved in the usual way by engineering design studies.

Before I forget to mention them again, here are two fun-to-read articles that offer an inside view of the people at NASA as they have worked to figure out the MAV. I'm going to mark this spot with a Mars so these refs can be found easily scrolling through here.


Reichhardt, "The One-Pound Problem," Air & Space (the Smithsonian's magazine), October-November 1999, page 50. I have read it online at http://www.AirAndSpaceMagazine.com/ASM/Mag.../1999/topp.html but if you can find the original in a library there are some nice artist concepts too. That article was written just before two Mars-bound spacecraft were lost, and years later the conclusions in that article turned out not to be the final answer.

The other is a two-part personal perspective by Dr. Mark Adler of JPL, on the Planetary Society blog in September 2006, http://www.planetary.org/blog/article/00000701/ and Part Two the next day at http://www.planetary.org/blog/article/00000703/

John W.

[John Whitehead]

Hate to even bring this up, but it sure seems like we might need to fly a pathfinder technology demonstration mission before committing to the real deal...and the nasty part here is that there's no place to do it & gain any value at all in engineering terms but Mars itself.

Aside from the truly formidible problems of designing a MAV, there are a bunch of other systemic complexities and event dependencies to consider, far more IMHO than in any other UMSF effort to date. I wonder if a high-risk Discovery-class mission could designed to send a few grams back of any random Martian surface material as a bonus; the real value would be assessing the performance of all these subsystems.

Maybe launch the MAV from a high-altitude balloon above earth, to simulate the atmospheric density on Mars. It wouldn't reach orbit, but the trajectory would tell how well it worked.

NASA has considered a bare-bones "scoop of dirt" mission. It is a tough decision to spend all that money without sending science instruments and/or a rover and/or a rock drill.

[JRehling]

[...]

[djellison]

a high-risk Discovery-class mission could designed to send a few grams back of any random Martian surface material as a bonus;

I can't imagine how you would land on Mars at all for a Discovery budge - let alone with any form of sample return ability. The only thing in that scale you could do is the SCIM proposal that is forever turned down in Mars Scout AO's

Doug

[Mark Adler]

I can't imagine how you would land on Mars at all for a Discovery budget

Apparently what you do is use leftover hardware from a previous, cancelled Mars landed mission. Phoenix plans to land on Mars on essentially a Discovery budget.

But yes, just getting MSR halfway back (e.g. to low Mars orbit) is not even in the ballpark of Discovery/Scout budgets.

[ElkGroveDan]

And wouldn't you know it, I bet there isn't any leftover Martian orbital ascent hardware lying around anywhere, is there?.

[dvandorn]

I dunno, Dan -- the last MSR concept I saw (back in the late '90s) used some leftover, off-the-shelf solid-fuel military missile as its basis for an ascent vehicle. I bet there are at least two or three of them left that haven't been fired in anger yet...

-the other Doug

[djellison]

Phoenix plans to land on Mars on essentially a Discovery budget.

I thought it was planning to land on ice deposits

It's a fair point - but if you take the '01 hardware costs, the scout budget, and the little-bit-extra - Phoenix isn't something you could do from the ground up for a discovery budget. If you got to a genuine 'build to print' state, maybe it'd work?


Doug

[Guest_PhilCo126_*]

Well, don't want to start any debates but remember:

The very first unmanned (Lunar) sample return mission:
http://en.wikipedia.org/wiki/Luna_16

basic MSR JPL-weblink
http://mars.jpl.nasa.gov/missions/samplereturns.html

[ElkGroveDan]

The very first unmanned (Lunar) sample return mission:
http://en.wikipedia.org/wiki/Luna_16

Speaking of left over equipment

That thing looks like it was made from an old oil drum and surplus scuba gear.

[Guest_PhilCo126_*]

Indeed an awkard looking spacecraft and this 'thing' had a weight of almost 2000 kilograms with the ascent stage over 500 kilograms... and the upper 'ball' (in fact the sample re-entry capsule) had a diameter of 30 centimeters... of course the whole thing 'only' had to escape the Moon's gravity
When we compare the 1971 Mars 2 or 3 spacecraft configuration, it looks almost identical to the Luna 9 or 13 surface capsules. So probably a Soviet-Russian MSR craft might have looked like the 'ugly' Luna 16?

[nprev]

Might be worth considering & contrasting US & old Soviet-era (SE) design approaches when thinking about MSR. From what I gather, most SE flight hardware was very rugged, implying that functional modules were optimized for their specific performance, and holistic system interfaces/dependencies were minimized in order to reduce risks. The US approach was almost diametrically opposite, relying instead on a robust C&DH capability to adaptively sequence critical events, which in turn allowed more trade space with respect to subsystem performance margins.

Wonder if there just might be a truly optimal middle ground, here...

[John Whitehead]

Might be worth considering & contrasting US & old Soviet-era (SE) design approaches when thinking about MSR. ...functional modules were optimized for their specific performance....

I was recently fascinated to learn how the Soviet Luna (16, 20, & 24) achieved its ascent and earth return. Yes, it was functionally very simple engineering, tailored to the particular physical situation. The moon's small size (compared to Mars) permitted a direct return. Not going into lunar orbit meant no circularization (orbit insertion) burn, and the fact that the target (earth) was gravitationally large and nearby meant no midcourse corrections either. No need for any engine restarts or staging. A single propulsive burn from the 1-stage ascent vehicle was simply timed (both moment of launch relative to the calendar, and burn duration).

Guidance consisted of flying a vertical trajectory off the moon. The vernier engines were controlled by a local vertical sensor, a pendulum! Site selection was limited to the east side of the moon, where a vertical ascent reduced the geocentric velocity compared to the moon's, so it was effectively just a deorbit burn with respect to the earth. Velocity would have been less than lunar escape velocity, since the earth was sitting there pulling it home. The return stage had a transmitter that could be switched on and off by commands from earth, and the resulting signals received on earth were used to predict the landing point accurately enough to go out and find it.

All this is explained in a paper by Boris Girshovich, presented at the National Space Society's 26th International Space Development Conference, Dallas Texas 2007May25-28. See isdc.nss.org/2007/index.html.

My notes from reading the above paper say that the earth entry capsule was 3 feet in diameter, while the above posting from PhilCo126 a couple days ago says 30 cm. I suspect both numbers are from memory or word of mouth, so does anyone have any solid references to cite here? Has anyone been to Russia where the capsule is presumably in a museum somewhere?

Mars ascent is MUCH harder to do, considering the need for a smaller size, higher delta velocity, double the thrust-to-weight, and more complicated navigation to orbit.

John W.

[nprev]

Fascinating & ingenious; really doing more with less. Thanks, John!

Maybe the way to approach this is to design a mission based on what we know we can do, rather then what we hope to be able to develop. (This is not meant to limit technological advance, but instead to constrain the problem). For example, if we assume direct EDL and payload DTE return, this simplifies the mission requirements considerably in some ways but possibly complicates them in others (one being the ability to meet really tight launch windows from Mars to Earth).

Just throwin' that out there...

[John Whitehead]

...leftover, off-the-shelf solid-fuel military missile as its basis for an ascent vehicle.
-the other Doug

Couldn't resist running a quick & dirty trajectory simulation to compare a MAV with military missiles. First verified the flight of a 100-kg MAV by running the trajectory simulation to reach a 500-km circular Mars orbit using about 4150 m/s delta velocity (results match a previous case in the Journal of Spacecraft & Rockets, Nov 2005 p. 1041). Then simulated flight of the same vehicle starting on earth. Had to increase thrust 50 percent so it exceeds earth weight of the vehicle. To reduce the effect of the thick atmosphere on such a tiny vehicle, moved the launch site to 10 km altitude (32,800 feet). The latter seems fair for comparison to air-to-air missiles, which might launch at such an alitude.

The simulation result indicates that a 100-kg Mars ascent vehicle launched 10 km above earth can go more than 500 km downrange. Now, what military missile in this size class has such a capability?

Take a look at www.designation-systems.net, and click Directory of US Military Rockets and Missiles. Note the extensive list available in the selection box. As an example, the latest Sidewinder (AIM-9) is said to have a mass just under 100 kg, but its range is said to be only tens of kilometers. A Navy Standard Missile (RIM-156B or RIM-161) has roughly the same reach as a MAV, but it weighs about 1.5 metric tons. Based on these 2 examples, military missiles appear to offer only a tenth the distance relative to mass, compared to what Mars ascent needs.

While it might be possible to push solid rocket technology toward sufficiently less inert mass to make a solid-propelled MAV, there is no indication that anything off the shelf is capable. If performance details for military missiles and their rocket motors could all be public, there would probably be a more widespread appreciation of just how much harder it is to make a MAV.

John W.

[John Whitehead]

...if we assume direct EDL and payload DTE return, this simplifies the mission requirements considerably in some ways but possibly complicates them in others....

Small-scale rocket engineering would blossom if NASA decided to build a direct-to-earth Mars ascent vehicle. And I'm a rocket technology person, so I should promote that, right? But the MAV would be multiple tons, not just because of the 40 percent higher velocity, but also to lift an interplanetary spacecraft instead of a sample canister. Solar power, pointing a high gain antenna to earth, midcourse corrections, earth entry capsule, etc. would all have to be launched off of Mars. In addition, the gigantic Mars lander needed to put such a beastly MAV down on Mars, is another whole unsolved problem.

Over 10 years ago, JPL had preliminary design efforts for a DTE MAV because autonomous orbital rendezvous was understood to be an unsolved problem. In early 1997 I had a chance to talk with Donna Shirley, a manager on the rover team who later wrote a book, Managing Martians. I remember saying to her that anyone who solves the rendezvous problem would be making a far greater contribution (to MSR) than any rocket engineer ever could. Since then there has been progress on rendezvous, but no real money dedicated to MAV technology. No money for a team of miniature launch vehicle experts means there is no one around to recognize that it actually needs work.

John W.

[dvandorn]

Couldn't resist running a quick & dirty trajectory simulation to compare a MAV with military missiles...

...While it might be possible to push solid rocket technology toward sufficiently less inert mass to make a solid-propelled MAV, there is no indication that anything off the shelf is capable. If performance details for military missiles and their rocket motors could all be public, there would probably be a more widespread appreciation of just how much harder it is to make a MAV.

The only corroboration I can find right now that the 2003-2005 MSR concept was to use military hardware is Steve Squyres' comment, in "Roving Mars," that the mini-MAV being planned for use in conjunction with the Athena rovers was "based on a classified Navy program." He also mentions the program had been in existence since 1958.

Squyres says that the payload this mini-MAV was to have lofted into low Mars orbit would have been about the size of a coconut. I imagine this would have weighed significantly less than 100 kg -- maybe only 20 to 30 kg.

The 2003-2005 MSR concept was that two different MSR landers would be flown, each serviced (i.e., loaded with samples) by one of the Athena rovers. An RTE vehicle would then rendezvous with and "gobble up" each of these coconuts and then burn back out of Mars orbit into an Earth return trajectory. (No matter what else happened, this means the two coconuts would have to have been launched into identical orbital planes, or else the RTE vehicle would never be able to carry enough fuel to rendezvous with them both.)

-the other Doug

[AndyG]

The vernier engines were controlled by a local vertical sensor, a pendulum!

Hi John - I'm rather wondering how that would work. If you're accelerating considerably above the level of local gravity, the pendulum will react to the centre of thrust as the local vertical. I could see a long, lazy arc being described back into the regolith.

Andy

[algorimancer]

There's been discussion elsewhere of the concept of sending a vehicle with a supply of fuel (typically liquid hydrogen), then after landing extracting liquid oxygen from the Martian atmosphere by breaking-down CO2. There was even a plan to fly a test version of the system on one of the recent landers (possibly MPL, doesn't really matter, it was dropped). This seems like a promising direction for MSR. Further, with the more recent establishment of the existence of water ice near the surface over much of Mars, simple electrolysis (via solar power) would allow production of both fuel and oxidizer on site, so this simplifies the MSR problem to that of delivering an empty launcher to the surface, along with associated equipment to generate the oxidizer (and perhaps fuel).

[mcaplinger]

I'm rather wondering how that would work. If you're accelerating considerably above the level of local gravity, the pendulum will react to the centre of thrust as the local vertical.

Regardless of the acceleration, the pendulum will always react to the vector sum of the gravity vector and the acceleration vector, so if you want to fly antiparallel to the gravity vector, this should work fine.

[mcaplinger]

The only corroboration I can find right now that the 2003-2005 MSR concept was to use military hardware is Steve Squyres' comment, in "Roving Mars," that the mini-MAV being planned for use in conjunction with the Athena rovers was "based on a classified Navy program." He also mentions the program had been in existence since 1958.

http://www.lpi.usra.edu/meetings/robomars/pdf/6052.pdf and the AIR&SPACE article referenced earlier in the thread. Basically this was the MiniMAV concept, which was found to have some overly optimistic assumptions.

[John Whitehead]

...Steve Squyres' comment, .... mini-MAV ... was "based on a classified Navy program." ...1958.
Squyres says that the payload .... size of a coconut. I imagine... 20 to 30 kg.
The 2003-2005 MSR concept ... An RTE vehicle would then rendezvous with and "gobble up" each of these coconuts and then burn back out of Mars orbit into an Earth return trajectory...
-the other Doug

The Mini-MAV idea was advanced by Brian Wilcox of JPL, whose father had worked on the noted Navy program circa 1958. The latter was a "hail Mary" attempt at China Lake to put a U.S. object into orbit as a quick response to Sputnik. The main trick was to use several spin-stabilized solid rocket stages, which made the vehicle smaller by deleting guidance & control hardware. Brian explained all this at the AIAA Joint Propulsion Conference in 2001, AIAA paper number 2001-3879.

Later studies of the concept by JPL and contractors resulted in putting the G&C back on. The conceptual design eventually grew from Brian's 20 kg to the latest reference design at 268 kg, too heavy to implement MSR using the MSL 2009 landing system (the largest Mars lander ever developed). The coconut-size sample container has remained the notional payload design for a MAV. Yes, launching a coconut off of Mars with a vehicle smaller than ~200 kg remains THE unsolved problem.

The quote attributed to Steve Squyres is a perfect example of the rampant collective optimism that a Mars ascent vehicle is going to appear from behind a curtain. NASA, JPL, and their contractors have done such a tremendous job of pulling off technological "miracles" for Mars spacecraft, that the implementation of missions is too easily taken for granted.

John W.

[John Whitehead]

...simple electrolysis (via solar power) would allow production of both fuel and oxidizer on site, so this simplifies the MSR problem to that of delivering an empty launcher to the surface, along with associated equipment to generate the oxidizer (and perhaps fuel).

In-situ propellant production is something that fits in with colonizing Mars, but scaling it down for robotic missions is very optimistic. The ground support equipment for a vehicle with cryogenic propellants would be heavy (cryogenic disconnects, chilldown, etc.). The equipment to produce, liquefy, and then store those propellants on Mars with refrigeration would not be simple, and it would all most likely be heavier than the propellants loaded into the MAV. In addition, cryogenic launch vehicles work much better on a large scale, where there is enough propellant volume relative to the surface area (i.e. entering heat) to endure the boiloff.

John W.

[nprev]

Understood. KISS has to be the guiding principle here, which is why I was pushing emulation of the Soviet design philosophy, at least for the Mars-to-Earth return phase. There are some truly formidible risks there that must be mitigated.

[mcaplinger]

KISS has to be the guiding principle here, which is why I was pushing emulation of the Soviet design philosophy, at least for the Mars-to-Earth return phase.

As Einstein said, "as simple as possible but no simpler." The history of MSR design is full of ideas that are simpler than possible.