Author Topic: Water, Methane, and Oxygen ISRU on Mars  (Read 25069 times)

Offline speedevil

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #80 on: 02/19/2018 01:57 PM »
The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.

If, and only if, ISRU seems a cheaper, or more reliable way of doing it for a given mission, including development costs.
Methane and oxygen also exist in earths atmosphere, nobody ISRUs, because you can get them in better ways.

(Buy them)

A lot of the posts in this thread are at best theoretical concepts with regrettably few ties to $ and W.

Offline DrRobin

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #81 on: 02/19/2018 03:20 PM »
The necessary gasses are already on Mars in various forms. Identify the path for extracting each (the purpose of this thread), and send the required ISRU equipment instead on early missions.
If, and only if, ISRU seems a cheaper, or more reliable way of doing it for a given mission, including development costs. Methane and oxygen also exist in earths atmosphere, nobody ISRUs, because you can get them in better ways. (Buy them) A lot of the posts in this thread are at best theoretical concepts with regrettably few ties to $ and W.
Right. Waaaay back at the start of this thread, the OP pointed to a NASA presentation showing the total mass to Mars was much lower for a complete CH4/O2 ISRU system than for Oxygen-only ISRU. Well, sure, but $'s burned in the process may not be optimized in the most mass-efficient choice. I don't think many are arguing against full ISRU as the long-term sustainable path. Still, it may be the case that shipping say, Ammonia, from Earth to give you both Hydrogen and fixed Nitrogen at the outset while efforts to generate Hydrogen locally are ramping up may be the best initial value to get things going. (My own scientific training is in biochemistry, so I can comment with more -that is to say nonzero- authority on these chemistry issues than for most of the other very interesting topics on this board. Nitrogen fixation, for example, is hard.) No one I have seen is suggesting shipping Ammonia from Earth to Mars as a long-term solution. That's what Ceres is for, silly.  :)

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #82 on: 02/23/2018 03:54 AM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #83 on: 02/23/2018 05:53 AM »
As you mentioned BFR, I chose C. Human operated ISRU.

Online Lar

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #84 on: 02/23/2018 05:53 AM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

Happily that's not the choice, though. B is no more than 3 "Musk years" later than A  (which is by no means happening tomorrow) and so very much more capable.
« Last Edit: 02/23/2018 06:00 AM by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Online RonM

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #85 on: 02/23/2018 01:58 PM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

We could have done Option A back in the 1990s when it was suggested, but nobody wants to pay for it. Not an option.

SpaceX is working on Option B. Probably will be done within 10 years, if it works at all. This is the only option being funded and it's cheaper.

There is no "If the choice were between" for Mars exploration. SpaceX may not be able to pull it off, but it's the only game in town.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #86 on: 04/01/2018 05:22 PM »
As you mentioned BFR, I chose C. Human operated ISRU.

To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.

Offline guckyfan

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #87 on: 04/01/2018 05:32 PM »
As you mentioned BFR, I chose C. Human operated ISRU.

To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.

How so? They go there, get ISRU going and fly home. No option A with hydrogen needed.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #88 on: 04/01/2018 05:34 PM »
If the choice were between..

A a sensible small scale scientific exploratory mission that imports hydrogen in a stable form and in small quantity and uses indirect return.

And..

B a ramping up of robotic ISRU to a scale necessary to support Musk's architrcture that puts off an actual manned mission another 10-15-20 years.

I choose A.

We could have done Option A back in the 1990s when it was suggested, but nobody wants to pay for it. Not an option.

SpaceX is working on Option B. Probably will be done within 10 years, if it works at all. This is the only option being funded and it's cheaper.

There is no "If the choice were between" for Mars exploration. SpaceX may not be able to pull it off, but it's the only game in town.

Well I don't agree here. If you want to know what I honestly think. I think that there will probably be small scale scientific/exploratory missions initially. I also think that its quite likely that the US won't be the main actor because of its political/cultural/economic problems.

I also think that when the initial missions occur they will benefit from very much lower launch costs, new technology and from fresh thinking. So mid 2030s is my best guess.

In that kind of time frame, we'll either see other competitors to Musk that go for mostly reusable boosters, or a British/European SSTO space plane (see my other thread).

I remain highly skeptical of large scale/colonisation ideas. Both for reasons of business case and for reasons that go to the dubious motivations behind such plans which I wont go into here.

I'm definitely in the camp of lets do it. But I also maintain that you have to walk before you can run.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #89 on: 04/01/2018 05:46 PM »
As you mentioned BFR, I chose C. Human operated ISRU.

To get those humans there to do the ISRU you need to get them there and back and thus you go back to option A first.

How so? They go there, get ISRU going and fly home. No option A with hydrogen needed.

You pre-land a small quantity of methane and the problem is solved. The whole story line about ISRU derives from the original assumption that its expensive to get mass into low Earth orbit (and thus hideously expensive to get to Mars). Now that its getting a whole lot cheaper to get stuff to low Earth orbit, getting a few tonnes of methane to Mars surface is becoming a trivial problem relative to the overall cost of the mission. Remember that eventually its development costs that really bite and the simpler it is and the more robust and less risky it is, the less development cost and the sooner we get there.

Oxygen ISRU for small scale exploratory missions is a worthwhile goal (because we need to breath too). And since it doesn't require complex operations and maintenance its also suitable for pre-landing.

Offline Slarty1080

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #90 on: 04/01/2018 05:48 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?
The first words spoken on Mars: "Humans have been wondering if there was any life on the planet Mars for many decades … well ... there is now!"

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #91 on: 04/01/2018 05:52 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.

Offline Slarty1080

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #92 on: 04/01/2018 05:55 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.

Perhaps this issue alone would make it "easier" to make use of hydrated minerals as a source of water and steer away from ice (at least initialy)?
The first words spoken on Mars: "Humans have been wondering if there was any life on the planet Mars for many decades … well ... there is now!"

Offline CuddlyRocket

Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #93 on: 04/02/2018 04:22 PM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

No. If planetary protection protocols effectively stop human missions to Mars then the protocols will be changed.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #94 on: 04/03/2018 01:23 AM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

They certainly make it a lot harder to just dive in with the sort of mining needed for colonisation scale ISRU.

Perhaps this issue alone would make it "easier" to make use of hydrated minerals as a source of water and steer away from ice (at least initialy)?

The planetary protection issue is one thing that steers me towards harvesting water from the Martian air, rather than soil.
« Last Edit: 04/03/2018 01:25 AM by Russel »

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #95 on: 04/03/2018 01:52 AM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

No. If planetary protection protocols effectively stop human missions to Mars then the protocols will be changed.

My point is that it makes a difference whether your aim is limited exploration or its outright colonisation.

The former can be achieved without mining. The latter probably cannot be achieved without mining and quite probably will venture into richer sources of subsurface water if at all available.

Offline philw1776

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #96 on: 04/13/2018 02:52 PM »
This looks very interesting. One step production of carbon dioxide (CO2) and water (H2O) into ethylene (C2H4) and oxygen (O2).

CO2 + H2O → 0.5C2H4 + 1.5O2

http://pubs.acs.org/doi/abs/10.1021/acssuschemeng.7b02110

Compare this trying to make methane (CH4):

CO2 + 4H2 → CH4 + 2H2O (Sabatier)
4H2O → 4H2 + 2O2 (electrolysis)

Overall reaction is

CO2 + 2H2O → CH4 + 2O2

That is, making methane requires twice as much water as ethylene as well as having a lower density and Isp compared to ethylene!

Propellants  MR   dp (kg/L)  ve (m/s) Id (Ns/L)
O2/CH4       3.6   0.8376     3656     3062
O2/C2H4      2.7   0.9007     3678     3313


What does "a solar-to-ethylene energy efficiency of 1.5%." mean?
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Offline LMT

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #97 on: 05/31/2018 02:50 PM »
Of relevance:  Steve Hoeser's new article series at The Space Review, with references and discussion: 

"Engineering Mars commercial rocket propellant production for the Big Falcon Rocket"



Part 1Methane Production:  Sabatier Processing Subsystem / Raw Material Sources for Sabatier Process / Water ISRU Sourcing on Mars

Part 2Oxidizer Production:  An oxygen production alternative using solid oxide electrolysis of carbon dioxide / Reverse water-gas shift (RWGS) reactors / Gases to Liquid Processing / Propellant Densification / Summing up the total power needed

Part 3Electric power: The options / Finding the right combination

--

In Part 3, one commenter states, "...the problem with a nuclear system would be getting rid of the rejected heat as there are no longer any large bodies of water on Mars."  And surely large nuclear plants would require significant mass for heat rejection systems.  How to minimize that mass?  I broached the possibility of a "supraglacial cooling pond"; presently exploring questions on required pond dimensions and radiator mass. 


Online A_M_Swallow

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #98 on: 06/15/2018 10:56 PM »
An alternative source of oxygen is to extract it from perchlorate salts. Although getting rid of the chlorine may cause a few problems.

Offline Russel

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Re: Water, Methane, and Oxygen ISRU on Mars
« Reply #99 on: 07/24/2018 10:38 AM »
Are "planetary protection" issues likely to put a spoke in the wheel of any planned extraction of Martian water for ISRU?

No. If planetary protection protocols effectively stop human missions to Mars then the protocols will be changed.

There is quite a difference between human missions to Mars and colonisation. Small scale missions can do well without ISRU sourced hydrogen.

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