How to return samples from Mars

[TimeTheFinalFrontier]

A recent SDC news topic on Mars Science Lab got me thinking about how we could cheaply return samples from Mars, leveraging MSL to select the most interesting and promising samples.

I was thinking something small, cost efficient, a design that could be replicated and sent many times during the lifespan of MSL. Probably each mission would only return 100 grams of material. Some considerations might be:

[*] Should it produce its own fuel for the lift-off from Mars?
[*] What shape is it? If it is rocket-like does it need to lay horizontally for MSL to insert the payload? How does it get back upright?
[*] Does each mission return to Earth or is there a Mars collection point for a carrier to bring all samples back at once?
[*] What are the challenges to returning the samples to Earth? Do we pick them up from LEO or let them plunge through the atmospere?
[*] Does MSL have enought articulation in the arm to place a sample into a return device?
[*] How big would it be to get 100 grams of material off Mars?

 

[JonClarke]

Good idea!

Unfortunately MSL will not be collecting smples and cannot do so anyway (although it was briefly considered).

However the 2018 NASA partner rover to ExoMars (MAX-C) will. See http://en.wikipedia.org/wiki/Mars_Astro ... rer-Cacher

As for the other points:

[*] Should it produce its own fuel for the lift-off from Mars?

If you do this you can return a couple of kg.

[*] What shape is it? If it is rocket-like does it need to lay horizontally for MSL to insert the payload? How does it get back upright?

Probably horiztonally to fit inside an aeroshell. However errection of a small rocket is a simple proceedure that we have extensive experinece on Earth via the military

[*] Does each mission return to Earth or is there a Mars collection point for a carrier to bring all samples back at once?

This depends on mobility, but the assumption would be one recover one return

[*] What are the challenges to returning the samples to Earth? Do we pick them up from LEO or let them plunge through the atmospere?

For worst case planning you have to assume it will enter the atmosphere. In that case you might as well design the mission to do this anyway. It is also simpler.

[*] Does MSL have enought articulation in the arm to place a sample into a return device?

Yes, but budget and mass constraints mean it won't.

[*] How big would it be to get 100 grams of material off Mars?

Depends on the propellant required. Assuming the payload is about 1% of structural mass that means a structural mass of 100 kg. Using methane-lox a direct return requires a mass ratio of about 9. So 800 kg all up, 1000 kg with margin. Double this for the landing stage you have 2000 kg, too big for a MSL type system.

You could offset this by having a Mars orbit nrendezvous, which is the currently preferred approach, or ISPP, which would mean you just have the empy stage to land, but must allow for the ISPP plant. If the ISPP masses 50 kg, than means you have a landed mass of 300 kg, which is about that of the MER landers This shows why ISPP greatly increases the mass of sample you can return.

 

[kpstinga]

[*] Should it produce its own fuel for the lift-off from Mars?

IMO, it shouldn't. It's gonna use solid fuel.

[*] What shape is it? If it is rocket-like does it need to lay horizontally for MSL to insert the payload? How does it get back upright?

A small rocket. which doesn't need to lay horizontally for anything.

[*] Does each mission return to Earth or is there a Mars collection point for a carrier to bring all samples back at once?

One return module - one carrier

[*] What are the challenges to returning the samples to Earth? Do we pick them up from LEO or let them plunge through the atmospere?

plunge through the atmosphere

[*] Does MSL have enought articulation in the arm to place a sample into a return device?

It doesn't matter. MSL won't be a part of sample return mission. Carrier that will be used is gonna have enough articulation.

[*] How big would it be to get 100 grams of material off Mars?[/quote]

About the size of a sounding rocket:
http://en.wikipedia.org/wiki/Improved_Orion

 

[TimeTheFinalFrontier]

JonClarke/kpstinga thanks for the comments! (and I'll read up on ExoMars). I'm no expert in any of this stuff but enjoy thinking about it.

[*] Should it produce its own fuel for the lift-off from Mars?

I tend to believe it must carry it's own fuel, but I read some comment somewhere on SDC discussing how to extract H2/O2 out of the Martian atmosphere (the hydrogen being problematic due to rarity). With kpstinga on this one, until I can understand more on ISPP (see below).

[*] What shape is it? If it is rocket-like does it need to lay horizontally for MSL to insert the payload? How does it get back upright?

Here I was guessing that anything rocket-like might be too tall for a rover to place a payload in the nose, or too unstable to remain upright (unstable soil, dust devil), but given the atmosphere is so thin maybe an aerodynamic shape is less important. I can see both your points though.

[*] Does each mission return to Earth or is there a Mars collection point for a carrier to bring all samples back at once?

Interesting that you both take different points of view on this. I could see that one recover one return would mitigate the risk of something happening to all the samples returned from the surface (if I understand correctly what you mean). On the other hand, returning the samples over a period of time to a common carrier then returning to Earth would make a LEO pickup economical. Having say, fifty samples, come back individually would require a lot of accuracy for re-entry a lot of times.

[*] What are the challenges to returning the samples to Earth? Do we pick them up from LEO or let them plunge through the atmospere?

Agree with JonClarke it seems it would be simpler, especially if all the samples were collected in a carrier that could have a sizeable heat shield and extra fuel for navigation to make an efficient and correct re-entry.

[*] Does MSL have enought articulation in the arm to place a sample into a return device?

JonClarke: Yes, but budget and mass constraints mean it won't.

What I was thinking was that if the MSL found something of interest that we wanted returned to earth, we could drop a return device close to the rover and use the sample acquisition tool on the robot arm to collect it and place it in the return device. Then fire it back into orbit around Mars where it would rendezvous with the carrier for an eventual return to Earth (along with other return devices with samples)

kpstinga: It doesn't matter. MSL won't be a part of sample return mission. Carrier that will be used is gonna have enough articulation.

I'm probably using the wrong word, but I meant the 'carrier' would be in Mars orbit to collect the return devices as they are launched off the surface. Once there are enough return devices with samples the 'carrier' would return to Earth.

[*] How big would it be to get 100 grams of material off Mars?

kpstinga: I'll read up on the Improved Orion. It's a bit larger than I thought would be required.

JonClarke: If the payload is 100 grams, or about 1% of structural mass, wouldn't that mean a structural mass of 10 kg?
"You could offset this by having a Mars orbit nrendezvous" that's what I was thinking. Regarding ISPP, I had to look that up! In-Situ Propellant Production. Also ISRU. Makes a lot of sense to me, although the chemistry to do it seems complex and long duration. Sheesh, more to read up on.... can't wait!