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Old 06-03-2020, 05:14 PM   #11
Ulzgoroth
 
Join Date: Jul 2008
Default Re: TL7 Spaceship Design

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Originally Posted by scc View Post
Nuclear thermal rockets would be an environmental disaster, spewing radiation everywhere.
I don't think there's any evidence for that.

Unless you mean in the event of a crash or explosion.
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Old 06-03-2020, 06:33 PM   #12
scc
 
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Default Re: TL7 Spaceship Design

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Originally Posted by Ulzgoroth View Post
I don't think there's any evidence for that.

Unless you mean in the event of a crash or explosion.
The US and the USSR both experimented in the area during the cold war and the USSR apparently got a bomber to fly completely under nuclear power, to do this however they had to make some sacrifices, one of them involved heating the air with the water that circulated within the reactor, meaning the plane irradiated THE AIR ITSELF! They also had to skimp on reactor shielding.

With all the more advanced technology we have today we might be able to get a custom built aircraft off the ground under nuclear power with spraying radiation everywhere, but I wouldn't bet on it carrying any cargo.
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Old 06-03-2020, 06:42 PM   #13
Michael Thayne
 
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Default Re: TL7 Spaceship Design

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Originally Posted by scc View Post
Using Spaceships rules a SABRE engine allows you to get something like 1.19 mps from a single fuel tank, over the 0.15 you'd normally get.
Hmmm. I'm fiddling with the math here and I'm wondering if the SABRE designers are assuming that by the time you're cruising along at Mach 5.5 at the flight ceiling of the air-breathing mode, you've basically paid the vast majority of the cost of air resistance / gravity losses? So then you'd only need about an additional 3.7 mps to get to orbit, which might work out.

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Originally Posted by Ulzgoroth View Post
I don't think there's any evidence for that.

Unless you mean in the event of a crash or explosion.
Wasn't radioactive exhaust one of the considerations that killed Project Pluto? Ofc if you're building an SSTO design you might make some compromises to avoid that problem.
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Old 06-03-2020, 07:20 PM   #14
Fred Brackin
 
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Default Re: TL7 Spaceship Design

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I'm pretty sure that Steampunk as a genre runs on Cinematic Gadgeteers.


Lack of funding and a political has hampered spaceflight in the real world, not really a problem in my setting.
Steampunk Gadgeteers also need to have their inventions be within genre and a very sophisticated TL9 spaceplane wouldn't be.

There was absolutely no lack of funding or political support for manned spaceflight in our world at TL7 (on the US side at least). Werner von Braun did not go to Congress and beg for funding. Congressmen came to him just to check if he needed any.

NERVA didn't spew radiation very broadly. They even blew one up while it was running just to see how big a mess it made and the answer was apparently "not that bad" at least by the standards of the time. Fission makes sut enogu neutrons to ssutainitself. Good designs minimize their loss to the environment.

Then there's hydrogen. Using LH2 for an upper stage that only burns in near vacuum is relatively hard at TL7. Doing it for a first stage is TL8. Doing it for your SSTO spceplane is bouble hard because it will not be able to land with enough fuel to return to orbit. It would have to process its' fuel at its' landing site. Even liqud H2 can't be stored for truly long periods of time. It all leaks away.

I've done designs for a vertol lander with a somewhat useful cargo capacity at TL9 but it used HEDM and carried a fission reactor and a fuel processing module.
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Old 06-03-2020, 07:28 PM   #15
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Default Re: TL7 Spaceship Design

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Originally Posted by Michael Thayne View Post
Wasn't radioactive exhaust one of the considerations that killed Project Pluto? Ofc if you're building an SSTO design you might make some compromises to avoid that problem.
I've always heard radioactive exhaust on Project Pluto declared a feature. On the other hand, the wiki writeup argues that Pluto's engine wouldn't deliver particularly much fallout - though that may have been intended in comparison to the multiple nuclear warheads it was supposed to drop.

Pluto wasn't a space rocket, isn't even properly a rocket at all. It's a nuclear ramjet cruise missile/unmanned strategic bomber.

It does seem like the NERVA prototypes had some core erosion problems that probably would result in some radioactives getting the fuel stream though, so that's not nothing.
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Old 06-03-2020, 07:39 PM   #16
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Default Re: TL7 Spaceship Design

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I'
It does seem like the NERVA prototypes had some core erosion problems that probably would result in some radioactives getting the fuel stream though, so that's not nothing.
It's uranium and fission by-products though. It's not neutrons spewing everywhere. Pluto was probably also designed around a juiced up reactor using weapons grade fuel.
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Old 06-03-2020, 07:41 PM   #17
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Default Re: TL7 Spaceship Design

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The US and the USSR both experimented in the area during the cold war and the USSR apparently got a bomber to fly completely under nuclear power, to do this however they had to make some sacrifices, one of them involved heating the air with the water that circulated within the reactor, meaning the plane irradiated THE AIR ITSELF! They also had to skimp on reactor shielding.

With all the more advanced technology we have today we might be able to get a custom built aircraft off the ground under nuclear power with spraying radiation everywhere, but I wouldn't bet on it carrying any cargo.
Irradiating the air itself is almost entirely negligible, and even more so when you switch from a jet to a rocket. A nuclear thermal rocket probably will irradiate its reaction mass - but with hydrogen that's going to produce very little in the way of concerning products. Some tritium probably.

The usual worry with regard to radioactive exhaust is fissionables, fission products, and radioactivated materials from inside the core being blown out along with the intended reaction mass.
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Old 06-03-2020, 07:45 PM   #18
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It's uranium and fission by-products though. It's not neutrons spewing everywhere. Pluto was probably also designed around a juiced up reactor using weapons grade fuel.
Uranium and fission byproducts is way worse pollution than some free-range neutrons, isn't it? Radioactive heavy elements stick around. Unshielded neutron flux will kill you if you stand in it. But it doesn't leave a lot of residue from a rocket launch to worry about. (Well, so long as you don't drop parts of the rocket that were heavily irradiated following core ignition back into the atmosphere.)
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Old 06-03-2020, 07:55 PM   #19
scc
 
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Default Re: TL7 Spaceship Design

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Originally Posted by Michael Thayne View Post
Hmmm. I'm fiddling with the math here and I'm wondering if the SABRE designers are assuming that by the time you're cruising along at Mach 5.5 at the flight ceiling of the air-breathing mode, you've basically paid the vast majority of the cost of air resistance / gravity losses? So then you'd only need about an additional 3.7 mps to get to orbit, which might work out.
Something along those lines seems to be the idea.
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Originally Posted by Michael Thayne View Post
Wasn't radioactive exhaust one of the considerations that killed Project Pluto? Ofc if you're building an SSTO design you might make some compromises to avoid that problem.
Pluto was a cruise missile to deliver nuclear warheads.

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Originally Posted by Fred Brackin View Post
Steampunk Gadgeteers also need to have their inventions be within genre and a very sophisticated TL9 spaceplane wouldn't be.
Massively complicated flying machines are very much in genre for steampunk.

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Originally Posted by Fred Brackin View Post
There was absolutely no lack of funding or political support for manned spaceflight in our world at TL7 (on the US side at least). Werner von Braun did not go to Congress and beg for funding. Congressmen came to him just to check if he needed any.
Said funding and support basically dried up after Apollo and didn't exist at the start of the TL.

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Originally Posted by Fred Brackin View Post
NERVA didn't spew radiation very broadly. They even blew one up while it was running just to see how big a mess it made and the answer was apparently "not that bad" at least by the standards of the time. Fission makes sut enogu neutrons to ssutainitself. Good designs minimize their loss to the environment.
NERVA was designed for exo-atmospheric use, this is in atmosphere, very different situation.
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Old 06-03-2020, 08:12 PM   #20
Ulzgoroth
 
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Default Re: TL7 Spaceship Design

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NERVA was designed for exo-atmospheric use, this is in atmosphere, very different situation.
All NERVA tests were done on the ground, though, so what difference are you pointing to here?
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