iheartbbq

iheartbbq t1_j6ipagh wrote

Reply to comment by danielravennest in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

Again, the juice is simply not worth the squeeze. You're adding nuclear complexity to every launch (nobody wants a dirty bomb going off in the sky) and you're just not getting significant benefits. You're still going to run out of propellant after an X minute burn. And now you're stuck with a super complex, hazardous, expensive boat anchor on your space craft that's VERY hard to cool because you only have radiation as conduction and convection don't exist in space.

Also

>Lighter molecules go faster at a given temperature, and H2 is much lighter than H2O. So you get roughly twice the exhaust velocity/specific impulse.

Oh, twice huh. H2 weighs 2 grams per mole, it will need to be ejected at nine times the velocity of a water molecule at 18 g/mol to have equal the force.

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iheartbbq t1_j6imc8u wrote

Reply to comment by danielravennest in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

Groan. Worst kind of pedant.

It's also what the main boosters of the shuttle system did.

The combustion process adds significant velocity to the propellant when properly nozzled. What is the point of adding the danger of a nuclear energy source in space when the propellant is completely expended? Just use chemistry.

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iheartbbq t1_j6i9j8s wrote

Reply to comment by A_curious_fish in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

And then what? Nuclear power on earth just steam power. Propulsion in space requires Newtons 1st law - to go forward you gotta shit some stuff out the back. You can't just heat up water and shoot it out the back, I mean, you can, but that's a lot of squeezing for not a lot of juice.

Just permanently emitting a stream of decayed nuclear atoms would produce a tiny amount of thrust, but it could build up to tremendous speeds over time. But again, not really practical for transit during human life time scales.

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iheartbbq t1_j6i6sie wrote

Reply to comment by Larry_Phischman in NASA tested new propulsion tech that could unlock new deep space travel possibilities by Creepy_Toe2680

Pulsejets require an atmosphere to operate. By definition they can't reach orbit with a single stage. There's no kind of conspiracy to hold back technology to prevent cheaper cost per kilogram to space or reusability.

Aerospike rockets are a FAR more practical SSTO technology (and pretty reusable, btw). Just never got serious funding because of the intense costs up front.

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