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SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Martian air breathing engine

The real issue is what can we do with the engine which has landed with the use of a different landing fuel?

RGClark

Member

From: Philadelphia, PA

Registered: 2006-07-05

Posts: 765

Website

Re: Martian air breathing engine

If we can seperate CO from the atmosphere relatively cheaply, then the gas shift reaction can be used to make other fuels.

H20 + CO = H2 + CO2. 

…

Thanks for that. I was thinking of simple filtration of CO and O2 at low energy cost out of the Martian atmosphere a la the NASA proposal mentioned by Calliban rather than by the high energy chemical breakdown of CO2 to produce propellant for CO+O2 propulsion. But this would be a low energy propulsion method. But if we can also get H2 via the reaction H20 + CO —> H2 + CO2, then we could also get the high energy H2+O2 propulsion.

  Robert Clark

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Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

RGClark

Member

From: Philadelphia, PA

Registered: 2006-07-05

Posts: 765

Website

Re: Martian air breathing engine

The real issue is what can we do with the engine which has landed with the use of a different landing fuel?

You can also make CH4 once you have H2 if your engine uses CH4. The amount of energy needed if done by chemical breakdown for the propellant production for the return trip is so high that it’s a serious limitation on ISRU plans for propellant. Robert Zubrin suggested a nuclear fission plant for example. And solar panels would require huge area to be covered on Mars with a great mass needed to be transported there.

See this video for a discussion of the issue:

SpaceX Starship can return from Mars without surface refilling.

https://youtu.be/u55zpE4r-_Y

Beginning at about the 12 minute point, the author runs the numbers and considers it so daunting, at least for initial missions, that he suggests it might be better instead to transport the propellant from Earth with multiple Starship tanker flights all the way to Mars.

  Robert Clark

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Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Martian air breathing engine

Engines that are made to burn hydrogen would need modifications to burn methane but engines that burn hydrogel, would be a real problem since manufacturing those from scratch have not been done outside of the industrial manufacturing for use.