Propelling deep space flight with new fuel source, Momentus prepares for liftoff
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Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#2Reminds me of some of Isaac Asimov's stories, where all ships are powered by nuclear reactors that flash water into steam for propulsion.
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#3180 seconds is a fairly terrible specific impulse...
Hydrazine monopropellant has something like 220 seconds, and the new safer monopropellants are comparable (less specific impulse but denser for less tank mass).
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#4180 seconds is a fairly terrible specific impulse... Hydrazine monopropellant has something like 220 seconds, and the new safer monopropellants are comparable (less specific impulse but denser for less tank mass).
Sure but can you refuel with more hydrazine on the Moon? With this new engine, just purify some water and you have more propellant ready to go.
Also, is hydrazine so efficient below 30 watts?
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#5Reminds me of some of Isaac Asimov's stories, where all ships are powered by nuclear reactors that flash water into steam for propulsion.
That's an interesting approach. Where did the water come from? Surely they weren't storing it as H20 on the ship? Seems like you'd only want to keep as much as needed for life support in that state. Stored as separate oxygen and hydrogen?
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#6Reminds me of some of Isaac Asimov's stories, where all ships are powered by nuclear reactors that flash water into steam for propulsion.
That's an interesting approach. Where did the water come from? Surely they weren't storing it as H20 on the ship? Seems like you'd only want to keep as much as needed for life support in that state. Stored as separate oxygen and hydrogen?
> Surely they weren't storing it as H20 on the ship?
Why not? It's not as if water is flammable, toxic, or highly corrosive - attributes most other fuel sources do have at least one of.
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#7Reminds me of some of Isaac Asimov's stories, where all ships are powered by nuclear reactors that flash water into steam for propulsion.
Would this increase the humidity of the local biome? Should we avoid using it in deserts?
Filling the tanks with Earth-sourced water would mean Earth bacteria, tardigrades, etc. The bacteria that stuck to the side of the tank, instead of being pulled out with the water-fuel, would reproduce once the tank is refilled from extraterrestrial (sterile) ice & water sources.
Could this be a cheap and dirty way of kickstarting terraforming? By landing and taking off on a planet like Mars with this engine, the steam exhaust would contain some of the bacteria and other denizens of the tank, some of which could be anaerobic. And this mixture could easily be intentional. The engine's steam exhaust could condense into a cloud of bacteria, and even precipitate to the surface.
Or the space ship could just have a sticker on the water-fuel tank door that says: Only use (sterile) space ice. No planetary ice.
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#8180 seconds is a fairly terrible specific impulse... Hydrazine monopropellant has something like 220 seconds, and the new safer monopropellants are comparable (less specific impulse but denser for less tank mass).
Sure but can you refuel with more hydrazine on the Moon? With this new engine, just purify some water and you have more propellant ready to go. Also, is hydrazine so efficient below 30 watts?
> Sure but can you refuel with more hydrazine on the Moon?
Water might be present on the moon in always-shadowed craters and it is not 100% proven. Those same craters might also contain other volatiles that could maybe be used to synthesize hydrazine or methane.
If water is found on the moon it could definitely be used to produce hydrolox which has amazing isp, ~450.
> Also, is hydrazine so efficient below 30 watts?
Hydrazine monopropellant is decomposed with a catalyst, it doesn't need external power.
If you need an external power source then you're competing against various ion thrusters which can get 10x the Isp. Maybe it's main advantage is extremely small size, or perhaps it gets higher thrust?
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#9Reminds me of some of Isaac Asimov's stories, where all ships are powered by nuclear reactors that flash water into steam for propulsion.
That's an interesting approach. Where did the water come from? Surely they weren't storing it as H20 on the ship? Seems like you'd only want to keep as much as needed for life support in that state. Stored as separate oxygen and hydrogen?
Without revealing too much (and possibly this qualifies as spoilers anyway), in Seveneves (Stephenson, not Asimov), it is a comet that, in a sense, 'becomes' the ship.
Re: Propelling deep space flight with new fuel source, Momentus prepares for liftoff
#10Earlier quoted context omitted.
That's an interesting approach. Where did the water come from? Surely they weren't storing it as H20 on the ship? Seems like you'd only want to keep as much as needed for life support in that state. Stored as separate oxygen and hydrogen?
> Surely they weren't storing it as H20 on the ship? Why not? It's not as if water is flammable, toxic, or highly corrosive - attributes most other fuel sources do have at least one of.
You have to have water storage if you've got people on board. I'd rather have one system that stores both fuel and life-support than have to have two separate systems and then guess exactly what proportions of both I'll need...