Reynard said:
The oft repeated question here is how will that 100Mwt translate to thrust. Will a truck sized reactor and the thrust mechanism (plus a the specialized fuel) be actually efficient and cost effective both for a useful payload and getting someplace? Oh, you did notice they mention the radioactive waste issue? Compound this with a fusion drive dumping tremendous amounts of radioactive death out it's nozzles and you will NEVER use it anywhere near Earth let alone as a surface to orbit system! Page 71 of Fire, Fusion and Steel describes as much for a fusion rocket. Such a ship needs to be built in space and aimed away from the planet. It's not clean Star Trek stuff, it's big, dirty and probably slow as a snail.
And again, reality sucks.
Your assuming again that it is launched under its own power from the surface of the Earth, that is incorrect, it is magnetic confinement fusion, that means a vacuum is required. After all the fusion plasma must be kept at a certain temperature, at about 5 times the core temperature of the Sun, as I understand it, this plasma is extremely diffuse, as fusion a tiny amount of it per second generates 100 megawatts, so density wise this plasma is very close to a laboratory vacuum, only very hot. To get a fusion drive to lift a spaceship off the ground, you would have to open up the fusion reactor to the outside to make it a rocket, and if you do that on Earth, the air would rush in, cool the plasma till it was no longer a plasma, and therefore would no longer be confined by magnetic fields, thus the fusion would stop. A fusion rocket of this sort only works in a vacuum. The good news is if it could be hauled by a truck it could also be launched into orbit by the SLS, which can lift 100 tons into orbit, it is a chemical rocket, but it can lift the entire reactor in one piece into orbit, so you don't have to build it in orbit. All you would basically do is add the crew module and fuel tanks, the advantage of this thing is it could deliver a crew to Mars in less than 30 days, and it would also open up the outer Solar System, Jupiter and Saturn to Human colonization because it reduces the travel time to those place. A trip to Mars with chemical rockets takes 6 months, it takes about 3.6 years to get to Saturn, it would take only 6 month with a fusion drive, so if we could reach Mars in 6 months with a chemical drive, a fusion drive would get you to Saturn in that same 6 months, and a fusion reactor would make a convenient power source for a settlement on Titan, as Solar Power is quite out of the question at this distance from the Sun, and with Titan's cloud cover. Titan has deuterium however, as much of its crust is made of water ice, and also there are methane lakes, methane contains hydrogen, a portion of that is deuterium. 100 megawatts could heat a lot of air. Warming up Titan's air and adding oxygen, is about what would be required to make it breathable, as its mostly nitrogen anyway, much like Earth's atmosphere.
