President Bush and Mars - Sample return too expensive

nirgal · 2002-10-03 07:31:04

I think the problem with in situ propellant production is power; it would take a few kilowatts to do, and they can't figure out how to stuff it into a small vehicle and still be reliable enough. Dust storms will not only cut off the power, but coat the panels with dust and permanently block them.

The 2009 MGE (Mars Geobiology Explorer) will use a nuclear power source. Since the first sample return mission will take place in 2014 at the earliest, using RTGs should be common place by then.

nirgal · 2002-10-03 07:34:52

...windshield wipers. If ruber wiper blades don't work with dust then replace them with brushes. The solar panels could last years before scratches accumulate sufficiently to cut-off sunlight.

I had the exact same idea. :0 There must be some technical issues though, otherwise NASA would have figured it out by now, too.

Mark S · 2002-10-03 09:25:20

Some thoughts on Sample Return...

In-situ propellant production was on the drawing boards for the 2005 MSR mission. This was back in the days before the infamous "English to Metric" conversion that turned the Mars Climate Orbiter into an artificial meteorite. Under the plans before MCO and Mars Polar Lander were lost, a small Sabatier reactor would be tested on Mars by the 2001 Mars Lander and then incorporated into the 2005 MSR. But Dan Goldin decided to scratch the lander following the loss of the two probes in 1999. It was succeeded by the 2009 "Smart Lander" (now called MGE.) As far as I know, MGE will move via wheels and not by in-situ produced propellant. D'oh.

Solar panels are still the best solution for any kind of ISPP test because an RTG can only produce somewhere around 400W of power. At some point (such as Mars Direct) a nuclear reactor will be needed to generate enough power for the ISPP process, but that decision will be made on whether the reactor is lighter than the corresponding solar array for the required power output.

Sample Return became a two-stage mission because NASA wanted international help to finance the mission, and because ISPP was viewed as too much of a technical risk. Under most of the scenarios, a lander with a rover and a solid rocket would be sent by NASA, retrieve samples, and blast them into Mars orbit. A French orbiter would then make a risky rendezvous with the sample canister and return it to earth. So much for the KISS principle...

Phobos · 2002-10-03 17:50:52

*Wouldn't it just be the absolute height of irony if some pathogen from Mars would halt the aging process? Kind of like a Fountain of Youth in a little microscopic squiggley? And here we'd be, unknowingly trying to protect ourselves from it, trying to "sterilize the field," contain it, eradicate it, etc., etc...all while researchers continue busting their rear-ends trying to stop the aging process -- and we passed over this little bug that'd solve the problem. That'd be our luck.

Oh man, just imagine if someone found out that Martian microbes could halt the aging process! You'd find no shortage of people clamoring for missions to Mars especially if we needed to find the places where the microbes like to hang out. You'd need a staffed Martian research base to find out things like that. And yes I know you could grow them but you'd still need to go back since we know nothing of Martian biology and thus could end up damaging our stock of microbes.

Thanks Phobos for encouraging me in my soapbox lecturing! I'm not sure whether you agree with me or just enjoy seeing my blood pressure rise and my face turn purple!!

Yes to both.

RobertDyck · 2002-10-04 02:18:38

Mars Sample Return has to be treated as a technology demonstrator for the manned mission. The question is mission architecture for the manned mission. NASA Design Reference Mission calls for Mars orbit rendezvous and the ERV carrying return fuel from Earth. This expensive version of MSR will give you an idea of the cost of NASA's idea of a manned mission.

nebob2 · 2002-10-06 16:08:45

Is it that bad of an idea to test the technology before we send in people? NASA orbited the moon many times before landing. Plus an orbital rendezous means you can mininize the astronauts exposure to radiation by allowing more rapid returns powed by nuclear or plasma engines. <60 day Earth-Mars tranists will improve eventual colinization anyways.

RobertDyck · 2002-10-06 21:17:59

Is it that bad of an idea to test the technology before we send in people?

Testing is a good idea. My concern is with keeping the mission affordable. In-situ propellant production reduces the mission cost greatly. I advocate a Mars-orbit rendezvous mission architecture, but I am suggesting just leaving in Mars orbit the habitat for return to Earth. The Mars ascent vehicle could be used as the trans-Earth injection stage. This would permit ISPP for the entire return to Earth. A sample-return mission does not require a habitat, so I suggest a direct return. This could demonstrate technology for ISPP.

Gas-core nuclear thermal rockets may have a specific impulse and thrust high enough to permit an extremely rapid trip to Mars. I consider any nuclear technology very high risk because the political climate prevent its use.

nebob2 · 2002-10-06 22:50:27

I agree, testing ISPP during the sample return is a good idea, and one of NASA's reasons for the sample return in the old DRM. In this case it would probably be best to just straight to earth.

In the actual human mission, however, it would be best to link up with a TEI hab already in orbit for the return mission, or even use the TMI hab/propulsion stage, depending on the propulsion system used. Limiting your return vehicle's fuel capacity, with low efficiency chemical fuel, to a landible size limits TEI velocities to 5-6km/s, if I remember Mars Direct's figures correctly. In reality 12-16km/s is perfectly doable with modern technology.

GCNR's have Isp's of about 3000s and can have farly high thrust, VSIMR combines both moderate thrust and high efficiency, an EPPR on the scale of NASA's plans would have an Isp of 4000s and produce 4.0x10^6N of thrust, and MPD, ion, Hall and other lower proformance plasma systems are excellent options for cheaping sending most of the mission hardware, and future cargo. All these sytems could be developed in time for a 2018 mission.

Nuclear power will likely be needed on the surface, so ignoring it for propulsive purposes is kind of like tying your hands.

ps- I forgot about Zubrin's NSWR (nuclear salt water rocket) which also offers high Isp and thrust.

RobS · 2002-10-08 15:43:20

Why salt water?

-- RobS

nebob2 · 2002-10-08 16:30:48

It's not salt water, as in NaCL mixed in with water, it uses urainium tetrabromide in a 20% concentration, about the same as NsCl is in seawater. The fuel tank is designed to absorb neutrons, preventing a reaction. When it is pumped out the fuel will start reacting. The fuel, if ejected at the proper velocity can be made to react just behind the rocket, producing considerable thrust. Zubrin wrote about using it for a mission to Titan, but its high thrust and efficency would be perfect for a manned Mars mission as well. It also lacks the concentrated pile of a NTR, so may encounter less political resistance.

Try this link for a full explaination,

NSWR

Mark S · 2002-10-08 18:29:22

If I remember correctly, a much greater amount of fuel is expended in ascending to Mars orbit than escaping from Mars orbit. If an ISPP ascent vehicle docked with an NTR-powered transfer vehicle in Mars orbit, it would combine most of the benefits of ISPP with the added efficiency of an NTR that both creates thrust and generates electricity.

dickbill · 2002-10-16 14:34:28

Hi all,
I also agree that a Mars sample return mission, under NASA or European Eurora control, is too risky and expensive for the expected scientific return.
I said many critics in another thread in that forum against the Eurora project of Mars sample return. My main critics were:
* Aerocapture then Orbital rendez vous...It seems risky, if it fails then how to justify the huge spend of money, credibility, time and scientific ressources wasted ? Only 2 or 3 twins missions could assure the success, but it's not cost-possible.
* This is a one shot only project, It's not a good example of long term investment for Mars colonisation, better to invest in a Mars Communication Network, or in shuttleC class launcher, for that purpose.
* The cost again, it could become like the equivalent of the ISS in terms of investment, draining all the ressources from the other Mars missions.
* The little mediatic impact: 10 kg of martians soil or stones analyzed year after landings ...well, i suggest to include more fun-sciences or more science-discovery for the public in the next martian missions, like Rovers, Gliders, Penetrators, Balloons, spectacular stuff like that.
* Finally, maybe it's just as good to prepare a human mission with geologists aboard.

nebob2 · 2002-10-16 15:22:17

While it seams like a waste of resources for the retern of 10 kg of samples, one of the main goals of the sample return mission is to test technologies which are to be used in future human missions. Having the craft produce propellant on the surface, and rondezvous in orbit with a return vehicle are likely going to be included in an actual human mission. This way we can make sure our technology will work on the real, not a simulated, Mars before we put lives at risk. Nothing points out flaws in a technology faster then feild use, many ideas work out fine in the lab but fail in the field. I would rather it fail (i.e. what if curent designs for propellant maufacturing don't work on Mars for some reason, that would neccitate a change in plans) before we had lives depending on it succeeding.

Phobos · 2002-10-16 19:04:23

While it seams like a waste of resources for the retern of 10 kg of samples, one of the main goals of the sample return mission is to test technologies which are to be used in future human missions. Having the craft produce propellant on the surface, and rondezvous in orbit with a return vehicle are likely going to be included in an actual human mission.

Are they planning to do in-situ propellant production in the Mars sample return? I don't recall that being a part of the mission but my memory might be hazy. If they are going to do that though there's no sense in having to do orbital gymnastics to get the capsule back to Earth. It'd be easier just to have the thing produce all the fuel it needs to directly return to Earth from the surface of Mars.

nebob2 · 2002-10-16 21:21:33

NASA was origonally planning to use ISPP, but I don't know if they have changed the plan or not. The origonal idea behind the orbital gymnastics was that it would provide a more robust, secure rentry vehicle in case their were biologicals in the sample. It would probably be easier to shoot straight back to Earth, but that would require a larger sample module.

nebob2 · 2002-10-16 21:22:22

NASA was origonally planning to use ISPP, but I don't know if they have changed the plan or not. The origonal idea behind the orbital gymnastics was that it would provide a more robust, secure rentry vehicle in case their were biologicals in the sample. It would probably be easier to shoot straight back to Earth, but that would require a larger sample module.

RobS · 2002-10-17 13:06:40

I see that in *Case for Mars,* page 156, Zubrin says ISPP for a sample return mission, requiring 400 kilograms of fuel, would take 20 kilograms of equipment (sabatier reactor and such) and 300 watts of power. On page 190 he refers to a "standard RTG" putting out 300 watts, so I infer he was thinking that an RTG would power the ISPP. The possible problems NASA has identified are (1) maybe they need a bigger sample return vehicle and thus more than 400 kg of fuel; (2) maybe there are no RTGs available any more. I think the latter is true.

-- RobS

nebob2 · 2002-10-17 13:15:10

They have one RTG left, and it is slated to go to Pluto. We should just buy some Pu from the Russians, or use some of our own, and build a few dozen more. They are not that complicated to build.

Mark S · 2002-10-17 16:04:34

The Department of Energy has announced that more RTGs will be built at the Argonne-West National Laboratory in Idaho. The power of the atom will continue to propel spacecraft through the solar sytem.

nebob2 · 2002-10-18 00:17:05

RTG's can only power electrical systems, they lack the energy to power a decent propulsion system. For that you need a reactor, the next logical step. They use nuclear fuel far more effiecently. I know some of the modern fuels, such as flip fuel, in research reactors can last 50-70 years, a thermal power system using such fuel could power a electric engine for decades. It is not as good for producing power as conventional fuel, but is still better then decay.

Mark S · 2002-10-18 06:13:06

On the contrary, NASA has proposed using an RTG to operate the ion thruster for a future Pluto orbiter, which Sean O'Keefe tried to promote as a better alternative to the current Pluto mission.

nebob2 · 2002-10-18 12:19:42

Sorry, I usually forget about ion thrusters, they're such low thrust. I was thinking along the lines of a MPD. Yes, with lower power requirement engines like hall or ion thrusters, an RTG can provide the power.

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#26 2002-10-03 07:31:04

Re: President Bush and Mars - Sample return too expensive

#27 2002-10-03 07:34:52

Re: President Bush and Mars - Sample return too expensive

#28 2002-10-03 09:25:20

Re: President Bush and Mars - Sample return too expensive

#29 2002-10-03 17:50:52

Re: President Bush and Mars - Sample return too expensive

#30 2002-10-04 02:18:38

Re: President Bush and Mars - Sample return too expensive

#31 2002-10-06 16:08:45

Re: President Bush and Mars - Sample return too expensive

#32 2002-10-06 21:17:59

Re: President Bush and Mars - Sample return too expensive

#33 2002-10-06 22:50:27

Re: President Bush and Mars - Sample return too expensive

#34 2002-10-08 15:43:20

Re: President Bush and Mars - Sample return too expensive

#35 2002-10-08 16:30:48

Re: President Bush and Mars - Sample return too expensive

#36 2002-10-08 18:29:22

Re: President Bush and Mars - Sample return too expensive

#37 2002-10-16 14:34:28

Re: President Bush and Mars - Sample return too expensive

#38 2002-10-16 15:22:17

Re: President Bush and Mars - Sample return too expensive

#39 2002-10-16 19:04:23

Re: President Bush and Mars - Sample return too expensive

#40 2002-10-16 21:21:33

Re: President Bush and Mars - Sample return too expensive

#41 2002-10-16 21:22:22

Re: President Bush and Mars - Sample return too expensive

#42 2002-10-17 13:06:40

Re: President Bush and Mars - Sample return too expensive

#43 2002-10-17 13:15:10

Re: President Bush and Mars - Sample return too expensive

#44 2002-10-17 16:04:34

Re: President Bush and Mars - Sample return too expensive

#45 2002-10-18 00:17:05

Re: President Bush and Mars - Sample return too expensive

#46 2002-10-18 06:13:06

Re: President Bush and Mars - Sample return too expensive

#47 2002-10-18 12:19:42

Re: President Bush and Mars - Sample return too expensive

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