Author Topic: Mars To Go  (Read 82900 times)

Offline Robotbeat

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Re: Mars To Go
« Reply #20 on: 10/30/2010 11:58 pm »
  I don't like putting technology development programs on the critical path to a mission, but atmospheric ISRU, in spite of it low TRL, is still comparatively simple and will be required for any sane Mars mission anyway.

There is no need to have the initial missions rely on ISRU as part of their critical path.

Also, why sniff for methane when there is water in the soil practically everywhere that could be converted to high Isp LH2/LO2?
Because CO2 is available literally everywhere on the surface and can be very easily processed with no scoops or shovels or rovers.

CO2 is far, far easier to process into oxidizer and fuel than damp soil.
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Offline savuporo

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Re: Mars To Go
« Reply #21 on: 10/31/2010 01:45 am »
Because CO2 is available literally everywhere on the surface and can be very easily processed with no scoops or shovels or rovers.
*sigh*

I loove how space cadets armwave engineering challenges away.

Did you bother to take a quick look at the presentations i linked to in the thread?
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Offline Robotbeat

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Re: Mars To Go
« Reply #22 on: 10/31/2010 04:38 am »
Because CO2 is available literally everywhere on the surface and can be very easily processed with no scoops or shovels or rovers.
*sigh*

I loove how space cadets armwave engineering challenges away.

Did you bother to take a quick look at the presentations i linked to in the thread?

I agree it's not mature to be used on a manned mission or even a flagship unmanned mission like MSR. The context was that I was comparing it to relying on martian ice. Context is everthing.

I actually think carbon monoxide may be a superior ISRU fuel on Mars because of its ubiquity and simplicity, but the engine technology needs more development.

(BTW, Bloombox fuel cell technology is based on research for Martian ISRU but reversed.)
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline madscientist197

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Re: Mars To Go
« Reply #23 on: 10/31/2010 10:06 am »
I actually think carbon monoxide may be a superior ISRU fuel on Mars because of its ubiquity and simplicity, but the engine technology needs more development.

Yeah, CO/LOX is greatly undervalued vs. CH4/LOX. Even if the engines burn a little hot (and the exhaust products are a little on the heavy side), you at least don't have to bring any of your reaction mass from earth (and it's not exactly difficult to find CO2 on Mars).
John

Offline guru

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Re: Mars To Go
« Reply #24 on: 10/31/2010 01:24 pm »
I actually think carbon monoxide may be a superior ISRU fuel on Mars because of its ubiquity and simplicity, but the engine technology needs more development.

Yeah, CO/LOX is greatly undervalued vs. CH4/LOX. Even if the engines burn a little hot (and the exhaust products are a little on the heavy side), you at least don't have to bring any of your reaction mass from earth (and it's not exactly difficult to find CO2 on Mars).

I also agree.  Back in the late 90's, NASA Lewis did a little research on carbon monoxide/oxygen engines.  They found that ignition characteristics weren't great by itself, but that if a little bit of hydrogen is used in the igniter, that they could get ignition on 8 out of 8 tries.  They designed a 500 lb thrust engine suitably sized for a sample return mission.

http://www.grc.nasa.gov/WWW/RT/RT1996/5000/5310l.htm


I recall them also giving a contract to Ultramet for material development or selection for a carbon monoxide engine.  (This company has done a lot with high temperature materials for multiple rocket applications, including solar thermal.)

www.ultramet.com

Offline kkattula

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Re: Mars To Go
« Reply #25 on: 10/31/2010 04:32 pm »
If ISRU is a non-starter:

1)  It would only take 2 extra D-IVH launches, each with a rover/tanker carrying < 650kg of propellant to top up the half MAVs which wouldn't need the ISRU or H2 feedstock and could carry some of their own propellant.

2)  Possibly both stages could then use LOX / CH4 or maybe even hypergolics.

 

Offline kkattula

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Re: Mars To Go
« Reply #26 on: 10/31/2010 04:50 pm »
Instead of one 90kg astronaut, why not 2 x 45 kg astronauts? (e.g. small women)

Instead of launching the surface habitat capsule back to Mars orbit, why not have the crew ride in the open in EVA suits? 

In fact with two crew, one could ride on each half MAV.  Without the capsule, each person could be a little heavier and carry more samples.


With SLS, I think you could probably add a Bigelow Sundancer module, with some extra PMs.

Offline guru

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Re: Mars To Go
« Reply #27 on: 11/01/2010 02:18 am »
If ISRU is a non-starter:

1)  It would only take 2 extra D-IVH launches, each with a rover/tanker carrying < 650kg of propellant to top up the half MAVs which wouldn't need the ISRU or H2 feedstock and could carry some of their own propellant.

2)  Possibly both stages could then use LOX / CH4 or maybe even hypergolics.


You're right.  I got so stuck on the fact that I couldn't carry all of the propellant in one aeroshell, and I really wanted to minimize the number of systems that would have to do a surface rendezvous, that I figured it was better to just make the propellant on site.  During the design process, sometimes I get one idea early on, and that idea doesn't really evolve to better relate to developments later in the process.

Some back explanation:

Before I put this plan together, I took a look at several more recent variations on Mars Direct such as Mars for Less (13 EELVs to send a four person crew to Mars but still used a nuclear reactor) and Mars Oz (an Australian proposal that replaced the nuclear reactor with solar panels but still used Saturn V class launch vehicles), and tried to take the best parts of each proposal and remove their weaknesses.  I figured if I'm only going to send one astronaut out, then it should have a comparable rocket/astronaut ratio to that of the Mars for Less proposal (3.25 rockets for an astronaut rounds up to 4 rockets), or it would lose out on grounds of lower return for the upfront investment.

But if ISRU is to be considered a non-starter, then Mars for Less would also require more than thirteen launch vehicles, so I suppose going up to six rockets could still maintain that ratio and remove a mission risk.  Of course this suggestion adds two more rockets that could fail, and four more aeroshells that need to land within a small area.  But if it means that carbon monoxide engines don't need to be built and ISRU doesn't need to included (and note that I don't personally consider either of those to be showstoppers on a six year timeline, especially in light of technology developments over the last twenty years and with how small the specified systems are) then it might just be worth the changes to speed up hardware development.

Additional advantages of your proposal:

1) More copies of systems like the aeroshells and rover platforms can be built, allowing for a shallower learning curve in manufacturing and larger margins for scrap allowance.

2) Switching the first/strap-on stage to methane means the second/core stage can be smaller due to increased efficiency on the first stage.  Maybe the first stage could then be light enough that the fist stage methane oxygen tank could fit in the volume constrictions - I'll have to go back and check on that, though.  Even if not, hypergolics are still more efficient and just as dense as CO/LOX,, so the hypergolic propellant combination would definitely work for the first stage.  The downside for me is that I would have to abandon what I thought was the very clever solution of sending out the feedstock hydrogen in the empty first stage carbon monoxide tank, and then filling the CO tank after all of the hydrogen had been converted to methane for the second stage. C'est la vie.

3)  The 400 kg set aside for the ISRU propellant plants could be used for ground supplies, allowing for surface stays longer than 3-5 days.

4)  Fewer solar panels would be needed so that might save another 150 kg or so, and that mass could be used for some extra batteries.   

So, yeah kkatula, I'm sold.  Consider Mars To Go updated. 


Quote
Instead of one 90kg astronaut, why not 2 x 45 kg astronauts? (e.g. small women)

Instead of launching the surface habitat capsule back to Mars orbit, why not have the crew ride in the open in EVA suits?

In fact with two crew, one could ride on each half MAV.  Without the capsule, each person could be a little heavier and carry more samples.

With SLS, I think you could probably add a Bigelow Sundancer module, with some extra PMs.


Having smaller crew members is certainly not a bad idea, and one that I  did consider, but it's a bit far outside of the mainstream line of thought right now.  It only takes one perceived flaw to cause the remainder of a good idea to be discounted.

I like having the Mars ascent capsule , though, because there are still dust particles and the like in the atmosphere, and the capsule offers some additional protection beyond that of the comparatively lightweight spacesuit, though there may be other remedies for that, like the spacecraft equivalent of a motorcycle windshield.  Having something besides your suit surrounding is also just psychologically more comforting.

Using a larger habitat is definitely something I advocate if the larger launch vehicles are available.

« Last Edit: 11/01/2010 02:49 am by guru »

Offline Robotbeat

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Re: Mars To Go
« Reply #28 on: 11/01/2010 03:00 am »
Almost every single combustion engine on Earth is doing atmospheric ISRU. Think about that.

ISRU is feasible if done properly. It may not be "easy," yet nothing is easy off-world. Here is a summary of the process:

Quote
The carbon dioxide (CO2) that makes up 95 percent of the atmosphere of Mars can be a valuable starting material for the manufacture of critical products. Unlike lunar resources, CO2 can be had by merely compressing the atmosphere. Carbon dioxide itself can be used to support plant growth at an advanced outpost. Both carbon and oxygen are important elements which have many possible uses at an outpost. There are several well understood chemical reactions that we can use to produce oxygen, methane, water, and perhaps other materials.

Oxygen can be produced by passing CO2 through a zirconia electrolysis cell at 800 to 1000deg C. Twenty to thirty percent of the CO2 dissociates into oxygen and carbon monoxide. Separation is accomplished by electrochemical transport of oxide ion through a membrane. A prototype reactor using this chemistry has been run for over 1000 hours. Using such a scheme, we could bring a small unit to the surface of Mars which would then continuously make oxygen for life support, propellant use, or further processing. The only additional item we would need to supply is the power to run it: a 12kW unit would produce about one metric ton of oxygen per month.
http://ares.jsc.nasa.gov/HumanExplore/Exploration/EXLibrary/docs/ISRU/08Atmos.htm

I should note that the 12kW example unit would also produce about 2 tons of CO (although not wholly separated) "for free."

And regarding RTGs, it's not very feasible for advanced RTGs to have a specific power greater than about 10W/kg(based on info here), whereas it may be possible to deploy a very lightweight solar array that could approach and even surpass that specific power (especially if they could be kept clean), if it didn't need to use batteries. EDIT:I actually still think we should use advanced "RTGs" of some sort, but they need to be better than they are now, and we need more fuel.
« Last Edit: 11/01/2010 03:11 am by Robotbeat »
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Offline guru

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Re: Mars To Go
« Reply #29 on: 11/01/2010 03:30 am »
One of the advantages of the ISRU plants as I had them arranged was that no propellant transfer was required between vehicles.  The change to landing propellant in separate vehicles does increase the chance that propellant leaks could occur.  I don't think I would want the propellant transfers would be done automatically, as that's just additional development work, but at the same time, having an astronaut hook up the hose increases the personal risk.  Now, maybe the risk is not as big as I'm making it out to be since this is done all the time in orbit, where there is minimal gravitational effect.  On the surface of Mars, the astronaut could hook up the hoses then drive 500 yards away and use a remote control to open the propellant transfer valves.

Offline guru

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Re: Mars To Go
« Reply #30 on: 11/01/2010 03:46 am »
Almost every single combustion engine on Earth is doing atmospheric ISRU. Think about that.

ISRU is feasible if done properly. It may not be "easy," yet nothing is easy off-world.

I don't think ISRU would really be a showstopper if someone actually decided to use it, as I've already stated, but the fact that it has a low TRL really makes it an easy target (as I just discovered), so it might just be best to pull it out of the critical path for an initial mission.  Or maybe one could make ISRU the primary mission mode and use the additional propellant landings as a backup option, but if you're already building the propellant landers, you should probably just use them.  I think ISRU will definitely be used eventually, though, as missions get bigger.  Like the name of the plan says, the purpose of this idea is just "to go" - not necessarily to explore, do scientific research, colonize, or cliff dive, though collecting samples is a simple enough task that if you're already there, you may as well pick up a few rocks.

Quote
I should note that the 12kW example unit would also produce about 2 tons of CO (although not wholly separated) "for free."

And regarding RTGs, it's not very feasible for advanced RTGs to have a specific power greater than about 10W/kg(based on info here), whereas it may be possible to deploy a very lightweight solar array that could approach and even surpass that specific power (especially if they could be kept clean), if it didn't need to use batteries. EDIT:I actually still think we should use advanced "RTGs" of some sort, but they need to be better than they are now, and we need more fuel.

That's one reason I decided to use solar panels for the ISRU.  It turned out that the RTGs were a little too bulky to allow for the ascent stage tanks to fit in with the wheels and ISRU plant.  One MMRTG puts out a lot of heat, and it would take three or four of those to equal the average power output of the solar power array specified (and I was really conservative on the solar array output, dividing the peak power output by eight to obtain an assumed average), and those put three MMRTGs put together still weighed more than the array.  Plus, inserting the RTGs into the aeroshell is something that is done at the last minute.  Inserting three of them and making them all fit would be a little difficult.  There is a little door on the side of the aeroshell just for the MMRTG.  I decided to use that hatch for astronaut transfer between the Dragon capsule and the lander instead.

Offline MickQ

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Re: Mars To Go
« Reply #31 on: 11/01/2010 07:16 am »
Maybe an ISRU demo on Mars should be the next "X Prize".

Mick.

Offline Nathan

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Re: Mars To Go
« Reply #32 on: 11/01/2010 07:32 am »
Yes, thought yes.
But take a look at this
http://esamultimedia.esa.int/docs/Aurora/iMARS_Report_July2008.pdf

MSR is a science mission. There is NO WAY the scientific community is going to risk their $5-7billion once-in a lifetime mission ( thats the ticket price of the above ) on something as unproven as Martian ISRU propellant.

Hence, its not in the concept.

EDIT: Its also not in the latest NASA reference MSR design

Perhaps it's a once in a lifetime $5-7b mission because it is not using ISRU?

Perhaps if they spent the money on a small demonstrator mission that simply hopped from place to place they would have a better chance of making it affordable.

Perhaps that X-prize idea is the way to go!
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline savuporo

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Re: Mars To Go
« Reply #33 on: 11/01/2010 02:39 pm »
As discussed elsewhere, proposal to do a ISRU tech demo missions is NOT going to come from science community.

You need to find another budget/funding source.

Considering Google generously put up $20M for a very basic lunar lander, and its a long shot...
 i believe martian lander WITH ISRU demo on board is far out of reach for a privately sponsored prize as of now.
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Offline Robotbeat

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Re: Mars To Go
« Reply #34 on: 11/01/2010 04:26 pm »
As discussed elsewhere, proposal to do a ISRU tech demo missions is NOT going to come from science community.

You need to find another budget/funding source.

Considering Google generously put up $20M for a very basic lunar lander, and its a long shot...
 i believe martian lander WITH ISRU demo on board is far out of reach for a privately sponsored prize as of now.
I agree a Martian lander with ISRU demo is probably out of reach right now of an X-Prize effort, considering all the failed Mars missions. But if the Lunar X-Prize actually works, it's not inconceivable that it could be feasible in a decade or so.

More realistic X-Prize goals would be for an Earth-bound Martian ISRU demo tested in conditions that simulate the Martian environment. An X-Prize for a Mars orbiter would be interesting, too... And probably a lot easier than a Mars lander/ISRU demo combo. (I'd be interested in prizes of just interplanetary communications and autonomous navigation in the solar system.)
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Offline savuporo

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Re: Mars To Go
« Reply #35 on: 11/01/2010 06:54 pm »
More realistic X-Prize goals would be for an Earth-bound Martian ISRU demo tested in conditions that simulate the Martian environment.
Like http://moonrox.csewi.org/ ?
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Offline Robotbeat

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Re: Mars To Go
« Reply #36 on: 11/01/2010 07:28 pm »
More realistic X-Prize goals would be for an Earth-bound Martian ISRU demo tested in conditions that simulate the Martian environment.
Like http://moonrox.csewi.org/ ?
Yes, that's what I was thinking of, except for Martian ISRU.
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Offline savuporo

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Re: Mars To Go
« Reply #37 on: 11/01/2010 07:38 pm »
You are free to go to
http://www.nasa.gov/challenges , find the "Idea submissions" link from the left menu and submit it.

As you can see, there are millions of dollars offered for things like autonomous sample return robot right now.
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Offline Robotbeat

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Re: Mars To Go
« Reply #38 on: 11/01/2010 07:40 pm »
You are free to go to
http://www.nasa.gov/challenges , find the "Idea submissions" link from the left menu and submit it.

As you can see, there are millions of dollars offered for things like autonomous sample return robot right now.
I just might do that! :)
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Offline A_M_Swallow

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Re: Mars To Go
« Reply #39 on: 11/01/2010 08:45 pm »
An unmanned ISRU mission to Mars will be mass limited which restricts the payload design.  For a mission in this decade the LV will be a Delta II, Falcon 9 or possibly a larger EELV (SDHLV is next decade).  Any viable estimates on how much a single launch can get to Mars orbit?  And Mars surface?

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