"Radioactive exhaust during the launch phase is a non-starter. It just won't happen." I totally agree with that. That's why ORION can never happen or be allowed to happen. This also rules out NERVA type engines as well. We don't want any radioactive exhaust going into the atmosphere. Hell, I have to live here too.I don't want to glow in the dark from inhaling that nasty stuff. Using the reactors as a source of power, we can convert it to other means of propulsive force without it directly venting to the atmosphere. <br /><br />As far as I can tell, only fighter jets produce enough engine power to fly vertical on their tails much like a rocket during flight. Most if not all other aircraft takes advantage of air over wings to reduce the power needed to fly level or climb higher. The problem with nuclear is that the sheilding makes them heavy, but I'm sure that with real research into the problem we can make them lighter and even more powerful. I also know that most of the larger commerical airliners use fanjets as opposed to turbojets. So the idea then would be to use the reactors power to spin up the fanjets compressors instead of burning fuel in a combustion chamber. With that, you can fly to almost 100k ft or almost 20 miles. That's a third of the way to where space begins. At that height, even if you are only doing a couple hundred miles per hour you can switch the engines over to running on hydrogen for the final climb to orbital speed and altitude. Even if our thrust level is low, as long as we are not using Ion or Hall effect type propulsion systems we can slowly accelerate to where we need to go. So what if it takes two hours as opposed to the current 8 minutes on a regular rocket? The overall stress and strain on passengers and payload would be a lot less. Since the reactors don't need refueling every mission, all we'd need to do is add more prop and go. With this idea, we eliminate the radioactive exhaust, take advantage of wings in atmosphere <div class="Discussion_UserSignature"> </div>