Well, it depends, really... Chemical rockets are fueled only of the pad ; SRMs or solid rocket stages have to be assembled at the factory with the powder inside and can't be emptied ; fictional advanced spaceships like the DG probably have "fusion power generators" that should be pretty durable... But still, that power device needs a fuel, maybe something like xenon gas... It seems to make sense to defuel is the DG isn't going to be used for an extended duration. :2cents:
AFAIK, the Shuttles tanks were carefully decontaminated and thoroughly cleaned up between flights.
Yes, I should have specified; the delta gliders and XR vessels(for the most part); good, I'll maintain my procedures for those.
Depends on the fuel.
If you're using a Nuclear powered VASIMIR or NERVA type engine no. Your fuel is nothing like gasoline because it is a solid block of Uranium or Thorium.
Your propellant of course is whatever fluid is most convienient.
If you're talking about KeroLOX and other hydro-carbon based chemical boosters (such as the Saturn V's first stage) your fuel
is exactly like gasoline.
Hah, I had no idea the Saturn V ascent stage had kerosene in it. The same dinosaur bones in my grandpa's old lamp took men to the moon...
Okay, so for non-combustive engines it doesn't matter if you're shooting dead pepsi or water(well, density, reactivity and such, I get that, but the composition doesn't matter)...I'll assume all my psedo-infinite delta V craft are nuclear; so I don't need to worry about those...great!
Also, if your propellant is LH2, you'll have severe trouble storing it inside the spacecraft when it is parked in an atmosphere. If you power down the vessel, the hydrogen will evaporate due to cryogenic storage being offline. So yes, in most cases it's certainly the best idea to drain, if only because the thing will have to go through several maintenance checkups, whic is always easier to do when it is empty.
A purely interplanetary craft parked in Orbit might be another matter. Its storage capabilities should be just as adequate as that of a space station. But again, if you have to power the whole thing down for a reactor overhaul or somesuch, you don't want your cryogenic propellants to increase the matter density of the surrounding space by an insignificant fraction...
I hadn't even thought about cryogenics, thanks for pointing that out...even worse, if the tank is well sealed, the pressure could build and go boom, right?
This is interesting discussion, thanks everyone!