[uikjhgyujmn]

Not allowed to fly cryogens on the shuttle as a safety feature. You also aren't allowed to carry propellant or use propellant on serviceable satellites, that was one of the design problems with the HST + shuttle.

It's not a shuttle specific thing it's the problem of anything man rated - you can't put anything dangerous onboard.

[rbanffy]

Then the shuttle is the problem. It's like saying crossing the river is impossible because you are required to use a school bus as a vehicle.