Author Topic: ITS Earth return propellant  (Read 818 times)

Offline Dalhousie

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ITS Earth return propellant
« on: 07/13/2017 03:33 PM »
Is there an authoritative reference for the estimated mass of propellant needed to return t the ITS from Mars surface to Earth?  I need it for a conference presentation. 

Otherwise some best attributable estimates would be appreciated.

Thanks

Dalhousie
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline envy887

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Re: ITS Earth return propellant
« Reply #1 on: 07/14/2017 12:33 PM »
On May 2, 2017, Tom Mueller, propulsion CTO at SpaceX, conducted a speech/interview with some members of the New York University Astronomy Society.

Quote from: Tom Mueller
The Mars rocket is meant to be completely reusable. Both stages, ship and [inaudible] can lift hundreds of tons in a single flight; it can go all the way to Mars and back, and you’ll have to fuel it on Mars; we’ll need to make about 1000 tons of propellant on Mars over a two-year cycle; bring it back; and that’s a tall order. You need about half a megawatt of energy to [inaudible] that much propellant [inaudible]

https://zlsadesign.com/post/tom-mueller-interview-2017-05-02-transcription/

Offline Lar

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Re: ITS Earth return propellant
« Reply #2 on: 07/14/2017 03:27 PM »
On May 2, 2017, Tom Mueller, propulsion CTO at SpaceX, conducted a speech/interview with some members of the New York University Astronomy Society.

Quote from: Tom Mueller
The Mars rocket is meant to be completely reusable. Both stages, ship and [inaudible] can lift hundreds of tons in a single flight; it can go all the way to Mars and back, and you’ll have to fuel it on Mars; we’ll need to make about 1000 tons of propellant on Mars over a two-year cycle; bring it back; and that’s a tall order. You need about half a megawatt of energy to [inaudible] that much propellant [inaudible]

https://zlsadesign.com/post/tom-mueller-interview-2017-05-02-transcription/
1000 tons (or tonnes) of propellant can get you the water needed as follows

Assume stoich (a SWAG) and no other losses (again a SWAG) and integer atomic weights (a fair approximation at this accuracy level) so the atomic ratios are :

 1 CH4          + 202     ( -> 1 CO2 + 2 H20 )
    12 + 4*(1) + 4*16 or  80  of which the hydrogen is 4 or 1/20

So you need 50 tons (or tonnes) of hydrogen

The water is going to be (2+16)/2 more than that or 9x or about 450 ton(nes)

Check this, how much CO2 is needed

 12+2*16/80 = 44/80ths or 550 ton(nes) 

Yaay it balances.
"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

Offline Dalhousie

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Re: ITS Earth return propellant
« Reply #3 on: 07/15/2017 03:44 PM »
Excellent!
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

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