The Astronomy Thread

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Mudcrush Durtfeet

Mudcrush Durtfeet

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Big Phoenix said:
Looks like a fairly complete prototype here;



Can also take wiki with a grain of salt;



The Hydrogen isnt actually coolant, its the fuel. Could have said it better but meant the nuclear reactor in nuclear rockets isnt all that different from a power reactor. Difference is you run liquid hydrogen through it to turn it into super heated gas for exhaust v running water through a power reactor. Just different plumbing.

Though Im not sure what happens after nuclear rocket is done firing to deal with the residual heat. In that video of a hypothetical mission to Mars it looks like they only use each engine for one burn then discard. Von Braun's idea post apollo was using nuclear powered "tugs" to do all the moving in space, reusing them over and over.
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Apparently it's 20 tons with a terrible thrust to weight ratio, 20 feet tall and 8 feet wide (a Raptor engine is apparantly about 1.5 tons, nine times the thrust and a lot smaller) . I don't think it gets you to orbit and I did read that it was meant for a second stage of a rocket. That also means it cannot land, so it's not going to have a lot of reuse capability without one hell of a lot of space infrastructure. Maybe more useful in 20 years?

TL;DR:

NERVA requires a superheavy first stage chemical rocket and would not be reusable in the current state of space infrastructure. Such rockets would be _really_ expensive.

This is all from a wikipedia article about the thing that was never put on a spacecraft and cancelled in the 70s. Take with a grain of salt.
 
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Big Phoenix

Big Phoenix

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Mudcrush Durtfeet said:
Apparently it's 20 tons with a terrible thrust to weight ratio
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Thrust to weight ratio isnt really important in space.
Mudcrush Durtfeet said:
That also means it cannot land, so it's not going to have a lot of reuse capability without one hell of a lot of space infrastructure.
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That was kind of the whole point it wasnt just an engine. It was supposed to be part of a larger project for Mars that was all scrapped when Nixon went with the Shuttle.
 
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Mudcrush Durtfeet

Mudcrush Durtfeet

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Big Phoenix said:
Thrust to weight ratio isnt really important in space.

That was kind of the whole point it wasnt just an engine. It was supposed to be part of a larger project for Mars that was all scrapped when Nixon went with the Shuttle.
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It cannot take off from Earth is the point. You still need a super heavy rocket for that.
 
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Cybsled

Cybsled

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I have to imagine they took video on board, wonder how long it will take for it to post
 
Cad

Cad

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Mudcrush Durtfeet said:
It cannot take off from Earth is the point. You still need a super heavy rocket for that.
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If they get to the point where the rockets are fully re-usable and can launch some usable payload to LEO, land, refuel, and do it again... then you can assemble some monstrous ships in space that wouldn't have a chance of leaving an atmosphere. These kind of engines would be used to escape earth, they'd be used in the final ship to accelerate to speeds that a chemical rocket in space couldn't come close to.
 
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Mudcrush Durtfeet

Mudcrush Durtfeet

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Cad said:
If they get to the point where the rockets are fully re-usable and can launch some usable payload to LEO, land, refuel, and do it again... then you can assemble some monstrous ships in space that wouldn't have a chance of leaving an atmosphere. These kind of engines would be used to escape earth, they'd be used in the final ship to accelerate to speeds that a chemical rocket in space couldn't come close to.
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Yes that's true, but those things couldn't themselves go land on large masses such as planets or some large moons (and take off again).

Besides, such mega spacecraft are going to be colossally expensive. Who is going to pay for such things? (Spoiler: no one).

If we get serious infrastructure going in space, it's going to be via SpaceX, at least for the forseeable future. Anything other than really cheap orbital access is going to be too expensive and only SpaceX is getting anywhere about doing this in the near future. Even other developers that are starting to talk seriously about reusability are way behind, it's going to take them years to match Falcon 9, by which point Starship should be fine tuned and being used heavily.

SLS? 1B per launch, lol. Starship might yet beat SLS to orbit, which is pretty amazing considering the developement time for both projects.

***

There have been some alternatives to chemical rockets that have already seen use, I forget the name of the asteroidal probe that matched orbit with a major asteroid, then left it and matched orbit with another.

There has been some light sail usage also if I recall.
 
Cybsled

Cybsled

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It’s space, but only in the sense that you tell someone you visited Chicago, but all you did was have a layover at O’Hare before flying elsewhere

It’s still cool, but obviously just a joyride vs an actual journey.

Also one thing stood out to me: both the Virgin and Blue Origin flights mostly had people messing around in zero G but very little looking out windows. With such a narrow window of time up there, makes it hard to choose
 
Cybsled

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Big Phoenix said:
Call me cynical but something not right about billionaires patting themselves on the back while the world is in such turmoil.
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You’re cynical

Nothing triggers me more than to go online and read posts like “instead of doing this, they could give clean water to (insert country here)”. Sure, and lots of other things could that as well, but people always single out space stuff

Long term survival of our species requires being able to live beyond Earth boundaries
 
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jooka

jooka

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If Bezos was actually working towards that and not space tourism I'd agree with you
 
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Cybsled

Cybsled

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Well they are technically, but people say the same shit about SpaceX also
 
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Gavinmad

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I realize I'm a bit late to the NERV discussion, but that's the whole goddamn point of super efficient low TWR engines, they're designed to only be viable in later stages.

I feel like experience playing KSP should be a prerequisite to being allowed into these discussions.
 
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jooka

jooka

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When I think of Musk and his motivation for this stuff its "I gotta get my family off this rock" type shit in his wacky head.
 
Gavinmad

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I mean its less about the patting themselves on the back and more about the unimpressive feat that they're patting themselves over.
 
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