Deimos and Phobos Spacecraft

[redliox]

Given this year's surprising number of Martian moon proposals, I thought a new topic thread should be dedicated to new spacecraft visiting the long-overlooked duo.

PADME is the proposed mission with the most details; an update summing it up is here: http://www.hou.usra.edu/meetings/lpsc2015/pdf/2856.pdf

For those posting, I suggest focusing on modern visits to Phobos and Deimos, i.e. Mars Express onwards.  Feel free to discuss human spaceflight to the moons, but this is part of the Space Science thread so think "probes" foremost.

[MATTBLAK]

A fairly big probe, with a combined chemical/ion propulsion. Most of it's chemical impulse would be for Mars orbit insertion in the vicinity of Phobos. Spacecraft fires penetrators into Phobos for combination analysis and anchoring. Then, the probe descends to Phobos surface by reeling in the penetrator's cables, scoops up some regolith. then using SEP, thrusts out to Deimos to repeat the process - the samples are cached in a re-entry capsule. Then, chemical & SEP thrust back to Earth where the capsule enters the atmosphere for touchdown in the Australian outback.

Variations? The probe could perhaps rendezvous with a couple sample return craft fired up from the Martian surface and it could cache their samples, too.

[nadreck]

A fairly big probe, with a combined chemical/ion propulsion. Most of it's chemical impulse would be for Mars orbit insertion in the vicinity of Phobos. Spacecraft fires penetrators into Phobos for combination analysis and anchoring. Then, the probe descends to Phobos surface by reeling in the penetrator's cables, scoops up some regolith. then using SEP, thrusts out to Deimos to repeat the process - the samples are cached in a re-entry capsule. Then, chemical & SEP thrust back to Earth where the capsule enters the atmosphere for touchdown in the Australian outback.

Variations? The probe could perhaps rendezvous with a couple sample return craft fired up from the Martian surface and it could cache their samples, too.

Would like to see something that could extract significant drill core samples say down 100 meters, break it up into segments and send that back, from Mars surface as well in a few locations, but that may have to wait until the experts and labs get there.  Still I think it would be easier for that deep a sample to be drilled from Phobos and Deimos, chopped up and not mixed up to be loaded into a return vehicle robotically than doing the same thing on the surface of Mars (and realistically to give us signficant understanding, in lots of different locations on Mars).

[baldusi]

Well, Philiae has shown that if you don't know the hardness of the underlying strata, firing hooks is a risky experiment on whether or not you can actually get an anchor.

[vjkane]

Would like to see something that could extract significant drill core samples say down 100 meters, break it up into segments and send that back, from Mars surface as well in a few locations, but that may have to wait until the experts and labs get there.  Still I think it would be easier for that deep a sample to be drilled from Phobos and Deimos, chopped up and not mixed up to be loaded into a return vehicle robotically than doing the same thing on the surface of Mars (and realistically to give us signficant understanding, in lots of different locations on Mars).

Deep drilling within the confines of what can be packaged on a spacecraft and done without any humans for a few millions of kilometers is challenging.  Even harder when your spacecraft weighs a few pounds.

As for Philae, I don't think that the harpoons ever fired.

[Blackstar]

[baldusi]

[...]
As for Philae, I don't think that the harpoons ever fired.

I don't know, really. But we know that the drill couldn't penetrate one bit even after forcing it. AIUI, given that hardness, the harpoons would have had quite a chance of not penetrating. And even if they did, they might have just broke a piece and not offering much anchor. Ice anchoring is quite difficult and requires very specific tools and techniques.

[kato]

SD2 (the drill) probably never touched the surface and MUPUS (the self-hammering probe) only found that it's above 2-2.5 MPa (which isn't much). The Harpoons were rated for penetrating and anchoring in about 13 MPa hardness.

[TakeOff]

Well, Philiae has shown that if you don't know the hardness of the underlying strata, firing hooks is a risky experiment on whether or not you can actually get an anchor.

They've figured out that they've wired the harpoon launching mechanism wrong, so the failure was not related to the hooking concept as such. If Philae wakes up again, they want to try them again, now knowing how to do it. The harpoons are not only part of the landing system, they also provide science about the hardness of the surface and temperatures down to a meter or so depth.

Source: somewhere in this SETI talk by DLR guy Jens Biele Dec. 6, 2014.:
http://www.seti.org/weeky-lecture/rosetta-lander-philae-mission-landing-comet-67pchuryumov-gerasimenko

[TakeOff]

Since interplanetary drilling seems to be so challenging, what about instead using directed explosives, like armor piercing weapons? No moving parts. Couldn't that dig up materials from quite some depth? Hayabusa 2 will blow up subsurface samples to be collected and returned to Earth. Sure, a drill could give better science, but now to begin with, wouldn't explosives be a good alternative?
Animation:
http://jda.jaxa.jp/result_strm.php?lang=e&id=2e032c23f72832dba634998602294f69

[Jim]

Since interplanetary drilling seems to be so challenging, what about instead using directed explosives, like armor piercing weapons? No moving parts. Couldn't that dig up materials from quite some depth? Hayabusa 2 will blow up subsurface samples to be collected and returned to Earth. Sure, a drill could give better science, but now to begin with, wouldn't explosives be a good alternative?
Animation:
http://jda.jaxa.jp/result_strm.php?lang=e&id=2e032c23f72832dba634998602294f69

No.  They would make it more complex because:

A.  The act of firing them at the target would put a large reactive force on the spacecraft necessitating larger thrusters and such
B.  If the projectile is self propelled, the complexity is self evident.
c. The reaction to the explosives is unquantifiable and thus it is unknown how to protect the spacecraft thus adding complexity.  Even after the explosion, some debris would remain in the area, even orbiting the target
d.  the explosives would contaminate any samples

[ISP]

Well, then why not do what Deep Impact/Hayabusa 2 will/did do? Non-explosive excavation, with a projectile made of a substance that wouldn't be found on the target body (copper, for instances).

It should also be simpler to make the impactor itself a spacecraft, but that will drive up cost and might increase mission complexity...

[TakeOff]

Phobos and Deimos are more massive, but I think that the ever more complex operations at low gravity objects (like Rosetta and Hayabusa 2) look very promising for exploring them too. Their time is coming. NASA and ESA maybe already have their hands full with other Mars missions next decade, but they would be great targets for the Asian space agencies and maybe Russia will finally reach Phobos on the next attempt. If they had made it in 1988 or 2012 this discussion would be different today. I'm disappointed that the Martian orbiters weren't better equipped for exploring the moons, the small Mars Express seems to do the most of its flybys.

Since interplanetary drilling seems to be so challenging, what about instead using directed explosives, like armor piercing weapons? No moving parts. Couldn't that dig up materials from quite some depth? Hayabusa 2 will blow up subsurface samples to be collected and returned to Earth. Sure, a drill could give better science, but now to begin with, wouldn't explosives be a good alternative?
Animation:
http://jda.jaxa.jp/result_strm.php?lang=e&id=2e032c23f72832dba634998602294f69

No.  They would make it more complex because:

A.  The act of firing them at the target would put a large reactive force on the spacecraft necessitating larger thrusters and such
B.  If the projectile is self propelled, the complexity is self evident.
c. The reaction to the explosives is unquantifiable and thus it is unknown how to protect the spacecraft thus adding complexity.  Even after the explosion, some debris would remain in the area, even orbiting the target
d.  the explosives would contaminate any samples

But JAXA is doing it now, while no one has drilled anything in space since Apollo, not counting the tiny drill of MSL which seems to require weeklong stops to just slightly scratch the surface. Hayabusa 2 will release its explosive charge in space while in orbit, and fly to the other side of the asteroid before it detonates, according to the animation I linked to above (about halfway into it). That solves the reaction and debris problems (I hope!) I think it will even leave a separate camera in orbit to film the explosion while the main probe takes cover. Gotta love the Japanese and their robotics!

[TakeOff]

Well, then why not do what Deep Impact/Hayabusa 2 will/did do? Non-explosive excavation, with a projectile made of a substance that wouldn't be found on the target body (copper, for instances).

It should also be simpler to make the impactor itself a spacecraft, but that will drive up cost and might increase mission complexity...

An advantage of using explosives is that the orbiter can drop it at will after having identified the most interesting place to excavate. An impactor has to arrive at much greater speed than the orbiter. The first problem with drilling in space is the unknown properties of the rock being targeted. If the orbiter could characterize the rock before it is excavated, the probability of success should increase.

Maybe an explosives driven "harpoon core sampler" (yes, I'm making this up) could even capture a nice intact unpolluted core sample? I'd be surprised if not huge research and development has been and is being spent on controlled explosives in the budgets for weapons, mining and construction industries. The second problem with drilling is the mechanics. Explosive bolts on the other hand are very reliable. Many successful spacecrafts have used lots of them.

Maybe Phobos is an undrillable rubble pile? The Russians certainly think of it as a pile of rubles by now

[Blackstar]

Maybe an explosives driven "harpoon core sampler" (yes, I'm making this up) could even capture a nice intact unpolluted core sample? I'd be surprised if not huge research and development has been and is being spent on controlled explosives in the budgets for weapons, mining and construction industries. The second problem with drilling is the mechanics. Explosive bolts on the other hand are very reliable. Many successful spacecrafts have used lots of them.

Something like that has been proposed--essentially a tube that gets fired into the surface.

The problem is that it's very unpredictable. What if it hits a rock and bounces off to one side and then loops that cable around the spacecraft? What if it hits a rock and bounces straight back into the spacecraft? What if it digs itself in and then cannot be extracted?

As for explosives, people seem to be forgetting that the reason you want to go beneath the surface is to examine stuff in detail. Blast it with an explosive or even kinetically and you're changing the material. You no longer get an accurate measurement of the material. It's contaminated. For example, if you're looking for volatiles, you may have just vaporized them in the process, and then you won't see them.

This is even a problem with drills because drills get hot. But at least drills are more precise instruments.

[TakeOff]

What would a crewed landing on Phobos or Deimos be like? Considering the very low surface gravity, is it enough to have an Orion hoover very near above it and let out astronaut geologists on an EVA to collect well selected stuff? Or could an Orion even be landed, using some relatively simple and low weight surface interface module attached to the service module? Of course the transfer habitation and many many other things are missing for a human mission to Phobos or Deimos, I realize that. I wonder if at least the cost of developing and bringing along a specialized lander could be saved on such a mission. If a crewed Earth launch and reentry vehicle like Orion could work also as a temporary vehicle for EVA's on Phobos and Deimos (having the mothership waiting in the background).

EDL and ascent is one of the big headaches for sending humans to Mars. This is one of the potential big advantages of going to its moons instead. But how much easier is it really? Is a particular Phobos lander spacecraft required?

[MATTBLAK]

With all the fuss lately about the cost and difficulties of EDL, surface power systems, dust mitigation, possible crew contamination of the Martian surface etc - as I have before, I would like to beat the drum again that rather than go to a free-range asteroid or even the Martian surface for now, that the DRM emphasis should instead be on sending humans to the Martian moons as the next goal.

So much can be done at those fascinating little worlds in partnership with telerobotics and sample return probes. And in an effort to minimize crew microgravity exposure, I would recommend 1 or maybe even 2 short stay missions at Phobos & Deimos: 20-to-30 days at each - staying in Martian orbit for 18 months might be unpalatable. Or if there were no stomach for two missions, a week or more at each moon with the rest of that time transiting from one to the other with SEP and/or chemical thrusters.

[Kaputnik]

What would a crewed landing on Phobos or Deimos be like? Considering the very low surface gravity, is it enough to have an Orion hoover very near above it and let out astronaut geologists on an EVA to collect well selected stuff? Or could an Orion even be landed, using some relatively simple and low weight surface interface module attached to the service module? Of course the transfer habitation and many many other things are missing for a human mission to Phobos or Deimos, I realize that. I wonder if at least the cost of developing and bringing along a specialized lander could be saved on such a mission. If a crewed Earth launch and reentry vehicle like Orion could work also as a temporary vehicle for EVA's on Phobos and Deimos (having the mothership waiting in the background).

EDL and ascent is one of the big headaches for sending humans to Mars. This is one of the potential big advantages of going to its moons instead. But how much easier is it really? Is a particular Phobos lander spacecraft required?

Sounds like a job for SEV:
http://en.m.wikipedia.org/wiki/Space_Exploration_Vehicle

[Blackstar]

So much can be done at those fascinating little worlds in partnership with telerobotics and sample return probes.

There's really no good evidence that this is true. I don't know of any studies that have looked carefully at the value of telerobotics.

[MATTBLAK]

So much can be done at those fascinating little worlds in partnership with telerobotics and sample return probes.

There's really no good evidence that this is true. I don't know of any studies that have looked carefully at the value of telerobotics.

I didn't come by the idea(s) all by myself - exploration papers by various Universities and studies by Lockheed Martin, Boeing and others over the years have often proposed such things. And much smarter minds than me have extolled mixed manned and robotic exploration missions in recent years. I think when I first heard of the idea(s) was during the Augustine commission a few years back. Also; since such a mixed manned/robotic Mars mission has never been done - yet - then talking about 'good evidence' being lacking is premature, I feel.