Gravity_Ray":12y84bji said:
There are a couple of basic problems with building with small parts in orbit (obviously there are some good things as well), but since you asked here are the problems:
1. Fuel storage in orbit. This problem needs to be licked before building in orbit can be solved. Fuel just doesn’t do very well in the heat and cold of space. There is no real data on how that fuel will hold up in orbit. Some obviously some work needs to be done to get some data points on this subject.
I keep seeing people say that, and it is in the Obama Space Plan, but I wonder, why would you store fuel in orbit? Why not simply wait until it is needed before launching it?
In other words, let's say you are going to assemble a vehicle to go to an asteroid. You put the crew habitation and command module in orbit. Then, you prep another module, which has the propulsion device (chemical rocket, vasimr, whatever), and you put that in orbit. Then, you launch a fuel module containing the fuel. Finally, you launch the people on a space taxi. All these launches are using commercial rockets such as Delta IV or Falcon 9 or whatever.
The module with the fuel should not stay up for more than, say, two or three days before the people go up and you leave.
I don't really see why you would have a fuel depot in LEO unless you're somehow generating the fuel in LEO. Otherwise, you have to launch the fuel to put into the depot, which itself requires fuel.
--Brian