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Yes! NERVA in the variant for reaching LEO was planed as an upper stage for the saturnV, with no option of reusability, so no cooling needed. If it blows up it produces alot space rubbish/debris, but it was the spirit of the 60s and 70s, or just the missing of knowledge about that.
Do you have a source for that? I know the drop-in NTR stages were not reusable, I'm asking whether they were intended to blow up or not.
I'm pretty sure that by then, they knew that an exploding stage would at least create a lot of debris...
A space tug doesn't need strong NTR thrusters like a LEO-shuttle, because it is allready in LEO and has enough time for its job, it uses a small NTR and so heat is not a big problem.
Yes! That's a very good point, although it does not remove the heat problem. It just reduces it.
But i would really suggest you to use LANTR, when this enables mutch smaller reactors, the extra thrust comes from the oxygen injection.
But for the same ISp and thrust you have to use LOX and LH2, which an pure CH4-NTR only can do by big reactors. But maybe you can use the air in the first flight phase as an afterburner and later a small LOX-tank when air is to thinn, then later in space the shuttle has lost some fuel mass, so that small reactors are strong enough for doing the rest thrust to orbit, MAYBE.
No, I will not use LANTR. I've already explained, that LANTR even with LOX/LH2, has less specific impulse than I do with methane! The extra thrust with the LOX injection only comes with a corresponding reduction in exhaust velocity.
I am already using pure airbreathing propulsion in the lower atmosphere, this is advantageous as it negates, for example, the need to ignite the reactors on the ground.
The extra complexity isn't warranted by the lower capability that LANTR provides...
Thrust is not problematic for me, specific impulse is. Even though I need more thrust than an LEO tug, for example, I already have around more than twice the needed thrust. The main engines are used relatively late in the ascent, and I am also not trying to do vertical climbs or aerobatics. I don't need superpowerful engines.
maybe the fact we don't have a NTR-LEO-shuttle are next to the NIMBY NIMBY exact all these technical problems.
It's less to do with OMG-nuclear-its-bad-do-not-want-NIMBY-NIMBY-NIMBY! and more to do with economics and politics in general. Heck, that's the reason why we don't have a chemical shuttle (ok, well, we do, sortof, but you get my point).
The more and more I look at this, the more hurdles it has, but that is also just engineering, not to mention the fact that I highly doubt that after all the work that has been done on NTR, any such "achilles heel", so to speak, would have been so easily missed...