Nuclear Rocket Petition On White House Website

Nuclear Thermal Rockets can have a higher efficiency than than conventional chemical rockets, but it's not as much as you might think. There's a limitation that to have a higher exhaust velocity in a thermal rocket, the exhaust needs to be hotter. And it can only be so much hotter before your reactor starts becoming molten rather than a solid. Which means that efficiency tops out at a bit less than double the exhaust velocity of conventional rockets.

Now, that's still useful, if you can get enough thrust to get up off of the planet (and to overcome the weight of the reactor in the process), then you might be able to lift quite a bit more into orbit. Except the petition is for an NTR that would only operate in space. And in space, where you don't really have to worry about the amount of thrust, and your speed is limited by your fuel and your exhaust velocity, things like ion drives can reach efficiencies an order of magnitude higher, or more. Which means, an NTR in space only wouldn't be as useful, compared to nuclear-electric or solar-electric propulsion.

I suppose an NTR not used for Earth surface to orbit might still be useful in landing or taking off from other objects. Really, that's where its strength would be, if you can get it to have high enough thrust, then it would be useful for getting things into orbit and back, as a surface-to-orbit ship. But as far as orbit-to-orbit ships go, ion drives and other electric propulsion can get a lot more speed out of the same tank of propellant.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/yAdDhNRRkDo/story01.htm

Santa Claus Feliz Navidad Netflix down Ryan Freel Melissa Nelson sound of music foot locker