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#26 2017-10-08 14:26:27
- louis
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- From: UK
- Registered: 2008-03-24
- Posts: 7,208
Re: SpaceX's new plan to get to Mars BFR comparison and summary
I'd dispute that. There are huge swathes of Mars where the surface material is about 5% water. Just scoop it up and boil off the water.
For every 1000 kgs of regolith you process, you get 50 kgs of water and from that about 5.5 kgs of hydrogen, if I've got the calculations right. A properly designed robot rover should be able to process at least 10 tonnes of regolith per sol and produce 500 kgs of water which could then be processed for hydrogen manufacture. Maybe with 300 tonnes being delivered to Mars by Space X we could have 10 of these robot rovers at 500 Kgs per vehicle (5 tonnes) , producing 5000 kgs of water per sol and 55 kgs of hydrogen per sol. That would produce about 66 tonnes of hydrogen over 1200 sols. Would that be enough?
If Musk depends on ISRU fuel for the return and that fuel is methane he will have to find a source of hydrogen. It doesn't seem likely he will be able to ship so much of it that he can make his methane using imported hydrogen due to continual boil off from a very large tank. That being the case he has to land where there is exploitable water. Until there is an exploration effort on the surface, we don't know where that might be. We should be looking at a number of candidate landing zones to determine which is the best.
If one of his 150te payloads is a tank full of methane and that is sufficient to get a ship home he can refuel on the surface. It is relatively easy to reduce CO2 to CO and liquefy the resulting oxygen, so then he wouldn't depend on finding good water and could land most anywhere, but he will not get his tanker and cargo ships back without a hydrogen source.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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#27 2017-10-08 14:39:46
- SpaceNut
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- From: New Hampshire
- Registered: 2004-07-22
- Posts: 29,433
Re: SpaceX's new plan to get to Mars BFR comparison and summary
The trouble is the amount of energy and machinery to process it not just the collection of it from insitu sources.
We surely do not have enough details as to what the BFR really is other than a few goal posts or marks of the field for going to mars.
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