Nuclear Rockets Moving Along

AKAImBatman writes "Bruce Behrhorst of NuclearSpace.com recently stumbled across a new engine from everyone's favorite Jet Engine maker, Pratt & Whitney. Unlike P&W's previous engines, however, this engine is not a jet, and is powered by Nuclear Fission. It seems that P&W has responded to the need for Mars transportation by inventing the first commercially viable nuclear thermal rocket. They have heavily improved upon the NERVA NRX design from the 60's, and have even solved the graphite ablation problem! With this new engine, it seems that an inexpensive trip to Mars is now firmly within our grasp. Will we rise to the challenge?"

Comments

Re:Indeed.

[AKAImBatman]

This design is significantly different from the NRX. For one, they didn't attempt to build the most powerful reactor in the universe. For another, they took advantage of LHOx afterburners. With both of those design choices in mind, they were then able to use a titanium shell to act as the heat sink for the reactor. Not only does it not ablate, but the titanium will melt and scram the reactor long before the reactor itself experiences meltdown.

In other words, this is an extremely safe reactor design. :-)

Re:Nuclear subs

[lousyd]

So Nuclear subs have been operating in secret?

Well, yeah...

You're more right than you (may) know. I served on a nuclear sub, as a reactor operator. In the two years of schooling we get, there's much emphasis on rote memorization as well as understanding. One list we had to memorize is "negative public consequences if there were an accident", one of them being "negative public reaction to the naval nuclear program". We were operating in secret. We were taught that a major part of the reason that the naval nuclear program even still exists is because it's never (ever) had an actual accident. ("Accident" being a strict government policy-defined term.) The only reason we can get away with six nuclear reactors bobbing up and down in San Diego's bay right at this moment is because people really honestly don't know they're there. They're not in the news, they have a low physical profile. "Well yeah", nuclear subs have been operating in secret.

Re:Not quite

[Catbeller]

Ya need to know that sub-critical nuclear fuel is never going to produce a mushroom cloud. Producing a runaway nuclear reaction is extremely difficult. You'd require the right isotope of uranium, first. Then you'd need two sub-critial lumps separated enough so the radiation engendered by their proximity wouldn't simply vaporize the engine before a chain reaction could take off. The two-sub-critical masses have to be brought into close proximity quickly, usually by firing the masses into each other with two high-explosive devices; picture a tube with HE on each end, with a uranium "shell" on each charge. You'd fire both shotgun shells down the tube to meet each other. The temperature and the radiation caused by their increasing proximity tries to vaporize the assemblage, but the sheer speed at which they collide enables the neutron levels to increase to a the point where a runaway chain reaction released enough energy to raise the temp to a few million degrees. Boom.

If a nuke Challenger went down, the LH2 used as propellant would ignite with the O2 from the air, and you'd get a big boom. Not as much as the Challenger with it's perfect blend of LOX and LH2, but it'd be pretty big, as booms go. But the reactor would simply fall like a radioactive Geo Metro. No boom. Wrong isotopes, no way to go critical.