Phobos-Grunt Options

[tedstryk]

In Astronomy's February issue, they report that Russia has approved funding for the Phobos-Grunt mission. Design work has gone on since 1997, and the new design is scaled down to fly an a Soyuz rocket instead of the larger Proton. The main purpose is similar to Phobos-2, with the addition of a sample return. Also being discussed is the possibility of it carrying a few "meteorological stations" fof Mars itself. Generally, I have written this mission off as "never going to happen," but with the new Russian alliance with ESA, I wonder if they might be able to actually fly this thing. Also, with Putin's increasingly Soviet-style leadership, and with the likelyhood of lunar missions from China and India, Russian pride might drive this mission. If so, I have a concern. This mission sounds really, really ambitious. And the Russians have never even sent a fully successful Mars orbiter, and that is when they launched them in pairs or triplets. Still, if the mission flies, even if it doesn't bring back Phobos soil it might obtain some interesting results. Here is ESA's Phobos-Grunt page:
http://www.esa.int/SPECIALS/ESA_Permanent_...IJFW4QWD_0.html

Also, ESA has another page on potential Russian programs, although this seem to be nothing but pipe dreams at the moment. Would be a cool mission though.

http://www.esa.int/SPECIALS/ESA_Permanent_...0LFW4QWD_0.html

And also a page on the only partially realized current Russian project, its program to put instruments on other's spacecraft, such as HEND on Odyssey.

http://www.esa.int/SPECIALS/ESA_Permanent_...HMFW4QWD_0.html

[Guest_BruceMoomaw_*]

Exactly the same problem applies for a human-sized lander (30-100 metric tons) ANYWHERE on Mars -- because a lander 64 times more massive than another of generally similar design will have only 16 times as much forward aeroshell area to brake it during entry.

This was the subject of Rob Manning's COMPLEX talk, which didn't make it into my final "Astronomy" article. No practical parachute design can be big enough to solve the problem; nor can high lift/drag aeroshells (like the "Ellipsled" proposed to aerocapture Neptune Orbiter, or even a winged vehicle) solve it.

The only possible solutions are (1) rocket engines capable of firing out the lander's bottom at supersonic speeds BEFORE it deploys its chute (as Ed suggests), or (2) a huge, 20-30 meter diameter decelerator capable of working at hypersonic speeds -- either rigid (in which case it must survive the heat of entry), or inflatable and deployed after the heating is over. Any of these three possible solutions, as you can imagine, will require a hell of a lot of new engineering work. Indeed, Manning says grimly: "These technologies are at very low TRL and have very uncertain outcomes on their success...We do not have high-likelihood Mars EDL systems to choose from." An advance test flight of any such general design will be necessary, with a lander weighing 10% as much as the actual manned lander. Yet another serious problem for those more eager than I am to see Footprints On Mars. Even the sample-return lander (about 1200 kg) will require a radically new parachute design.

[ljk4-1]

Exactly the same problem applies for a human-sized lander (30-100 metric tons) ANYWHERE on Mars -- because a lander 64 times more massive than another of generally similar design will have only 16 times as much forward aeroshell area to brake it during entry. 

This was the subject of Rob Manning's COMPLEX talk, which didn't make it into my final "Astronomy" article.  No practical parachute design can be big enough to solve the problem; nor can high lift/drag aeroshells (like the "Ellipsled" proposed to aerocapture Neptune Orbiter, or even a winged vehicle) solve it.

The only possible solutions are (1) rocket engines capable of firing out the lander's bottom at supersonic speeds BEFORE it deploys its chute (as Ed suggests), or (2) a huge, 20-30 meter diameter decelerator capable of working at hypersonic speeds -- either rigid (in which case it must survive the heat of entry), or inflatable and deployed after the heating is over.  Any of these three possible solutions, as you can imagine, will require a hell of a lot of new engineering work.  Indeed, Manning says grimly: "These technologies are at very low TRL and have very uncertain outcomes on their success...We do not have high-likelihood Mars EDL systems to choose from."  An advance test flight of any such general design will be necessary, with a lander weighing 10% as much as the actual manned lander.  Yet another serious problem for those more eager than I am to see Footprints On Mars.  Even the sample-return lander (about 1200 kg) will require a radically new parachute design.

Another problem to consider when landing on Mars with retrorockets: The fine powdery surface grains would spread far and wide and sandblast anything nearby. Better have landing pads far from the base, unless they come in on an airplane.

http://www.news.cornell.edu/Chronicle/05/1...e_research.html

How much surface dirt did the Vikings kick out when they landed? Considering how much they wanted to find microbes at the landing site, and they could not move around, I am surprised in some ways that they did not think of another landing method to disturb the ground as little as possible.

[JonClarke]

How much surface dirt did the Vikings kick out when they landed?  Considering how much they wanted to find microbes at the landing site, and they could not move around, I am surprised in some ways that they did not think of another landing method to disturb the ground as little as possible.

Not Much Viking had three landing engines with 18 nozzles fueled by specially purified hydrazine monopropellant. The hydrazine would not contaminate the ground and the 18 nozzles were specifically designed to minimise erosion on the ground. Some effects were noted though not particularly severe.

Jon