Do you support a Nuclear Space Initiative? - Poll Results.

dicktice · 2003-02-16 11:15:18

I'm in favour of water-ice-use as much as possible in interplanetary spacecraft, to the extent of being actually surrounded by a "cake of ice," as the solution to many of the problems arising in connection with human transportion in space. I'm assuming, according to latest estimates, there'll be plenty of (admittedly dirty) cometary ice to be found for this purpose, orbiting inside or crossing Earth's orbit.

RobertDyck · 2003-02-16 11:48:15

Water is H2O. Hydrogen has an atomic weight of 1.0079 and oxygen is 15.9994; so the molecular weight of oxygen is 18.0152. Thrust is generated from gas expansion, so breaking water into mono-atomic gasses would produce 3 atoms for every molecule of water. Hydrogen would produce 2 atoms from each molecule of LH2. LH2 masses 2.0158 grams per mole, vs water at 18.0152 grams per mole. There are 6.022*10^23 molecules per mole. This means water or ice would substantially increase the mass of propellant for a given thrust, and that dramatically reduces specific impulse (Isp). Would the reduced Isp really be worth the reduced tank size?

Echus_Chasma · 2003-02-16 23:02:16

Would the reduced Isp really be worth the reduced tank size?

Depends, which would be more fuel efficient?
Personally, I would go for an increased Isp, cos, I suppose with more fuel efficiency, you don't need to carry as much fuel, so, therefore you don't need a biggish fuel tank.

Sorry, but I can't do any of that maths too work it out.

soph · 2003-02-23 20:19:32

If you had a fusion drive, water would be worthwhile-because that would be your propellant, and you would need only 1%-10% propellant, depending on your mass.

If you were on an interplanetary mission-water is the way to go, crack for fuel, use for radiation protection, and crack for oxygen. Especially on an interplanetary mission. However, for a fission-based launch vehicle or SSTO, water isnt the way to go.

Shaun Barrett · 2003-02-26 17:29:38

Timberwind or liquid core NTR, what are the chances of getting it past the screaming rent-a-crowd protesters?
As has been pointed out elsewhere in New Mars, they practically had apoplexy about the Cassini RTG! Imagine the orchestrated insanity we'd see with NTR ground launches!

I don't mean to be a party-pooper, but ...

RobertDyck · 2003-02-27 00:13:24

Perhaps you're right. I was saying the same thing until the announcement about Prometheus. However, that initiative is focusing on nuclear electric propulsion for interplanetary spacecraft.

TJohn · 2003-02-27 12:33:43

RobertDyck,

How long do you think we will be able to use nuclear electric propulsion to transport humans to the moon, Mars, and other areas within the inner solar system?

soph · 2003-02-27 16:57:22

TJohn:

I don't think NEP should ever be our primary propulsion method. Fusion will be ready by the time we get any significant thrust out of NEP, so I think the best use for an NEP would be as a hybrid NTP/NEP, to maximize thrust and fuel efficiency.

However, NEP might be a good option for probes, where speed is not as much of an issue.

TJohn · 2003-02-28 07:27:23

Thanks, soph.

You mentioned that NEP be used for probes. Is the JIMO mission NEP?

soph · 2003-02-28 11:31:12

I believe so.

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Re: Do you support a Nuclear Space Initiative? - Poll Results.

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