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James Oberg On Mars!
Marvin the Martian wrote:
I thought Bolden said "Mars in 39 hours"! Or days, or whatever. What pipe-dream was he smoking? That was the ion engine claim. I'm going to assume that aerobraking is not a possibility if you're moving that fast, so does that figure presume some ion engine braking as part of orbital insertion, or ion engine braking plus aerobraking? Dave |
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James Oberg On Mars!
David Spain wrote:
I'm going to assume that aerobraking is not a possibility if you're moving that fast, so does that figure presume some ion engine braking as part of orbital insertion, or ion engine braking plus aerobraking? That wasn't a ion engine, it was the superconducting VASIMR plasma engine, which generates a lot more thrust than a ion engine. Pat |
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James Oberg On Mars!
Pat Flannery wrote:
That wasn't a ion engine, it was the superconducting VASIMR plasma engine, which generates a lot more thrust than a ion engine. Pat OK, my bad, sorry. What's cooling those superconducting magnets? If they aren't YtBaCuO2 it ain't liquid N. That'd be liquid H or liquid He. I suppose you could ionize H, so it could double as a coolant for the magnets and as a fuel source. But liquid N might be easier to deal with with a lower ionization energy if you could use it instead or the colder liquid O, but N would be less corrosive. Liquid O might be more utilitarian to have around tho'. Liquid H, requires more energy to ionize, but would yield a higher thrust. Probably rules out Now you've got long term cryogenic fuel storage issues, but dramatically shorter transit times I suppose. It's a stretch, but so's any kind of Mars program, so a research project possibly. Woah! Take a look he http://chemed.chem.purdue.edu/genche...ch7/ie_ea.html I must remember to pay more attention to my atomic orbitals! Lithium might be the best bet. Li at Atomic # 3 won't yield as good an ISP as H but look at the ionization energy! This has got be the sweet spot for this type of engine! No cryo issues except for magnet cooling! So you feed it a supply of solid Li, heat it in vacuum to sublime to gas and you're ready to go into stage 1 of VASIMIR. Thus only need enough liquid H to cool the magnets, or maybe liquid N if using high T superconducting magnets. Damn, do we *need* superconducting magnets? What's the mag flux needed for this that normal electromagnets can't do? Still need that beefy electrical power source. Dave |
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