Nuclear propulsion is the simplest thing in the world. Obviously, the word NUCLEAR is scary. Apparently, the presence of this world has destroyed more projects than the Congressional Budget Office. But still, Nuclear Thermal Propulsion, to be specific, is easy peasy lemon squeezy.
Figure 1. The simple view of a Nuclear Thermal Rocket.
To start with, you get a tank of water. Then you boil it. Then you squirt it behind you. Yeah, that’s about it. You can use Helium, Hydrogen, Water, Liquid just about anything will work. The boiling process is run by a hot nuclear fission reactor.
Now, a couple of points:
- It doesn’t turn off and on like your stove. It takes hours to heat up and days to cool off.
- The waste is slightly radioactive.
- The thing could melt if run too hot without propellant. So, accidents could happen.
- You get a lot of thrust per pound of fuel.
- It is very efficient. ISP around 1000, twice as good as a chemical engine.
- It can last for tens of years, used carefully.
Well, looking at those points, what is the engineering argument? You probably shouldn’t light one off on the ground. They save literally tons of fuel, but with a high thrust, so you can use them in a gravity well. (Super high efficiency engines often have almost no thrust, gravity and atmospheric drag can defeat their efforts.)
The best locations for nuclear rockets are planetary orbits, possibly the occasional moon landing or Mars launch. Good bang for the buck.
So, when it comes time to move Man from low earth orbit (LEO) to geosynchronous earth orbit (GEO), or even the Moon. Nuclear Rockets are the best engineering choice.
Again, we first need to develop a solid method of delivering payload and fuel to a LEO space station. Then, we need to develop a strong work horse to deliver these payloads where they need to go. A deep-space dock at a location like L2 (shown below) might be the best choice. But satellites have lots of locations to go to, a good delivery service is worth hundreds of millions each year.
Figure 2. Lagrange (L) points on a map. The closest to Earth are L1 and L2. The others could simply be called “co-orbit with Earth.”
So, when you are looking at the future of space flight. It starts with delivery to LEO, but that is too close for real space work. To get human projects out of the gravity well, we need a workhorse. I recommend a nuclear rocket for near-space travel.