Diving into a Gas Giant for spaceship fuel

[doctorevilbrain]

Is diving into a Gas Giant for fuel realistic? I've tried to look for info, and couldn't find anything. What would it take without damaging or destroying a ship? How would you filter out the impurities?

[Anthony]

Originally Posted by doctorevilbrain

Is diving into a Gas Giant for fuel realistic?

Gas giant skimming, a la Traveller, is not realistic. Under certain assumptions gas giant mining for helium-3 may be viable, but that would generally involve mining platforms held up by hot gas balloons or aerodynamic effects, not spaceships.

[Timolas]

I may be missing something; but why is Traveller style fuel skimming unrealistic? Wouldn't it be a little like aerobraking only you have your fuel scoops wide open? Might take a few dives to fill up completely, and it's probably a rough ride, but the concept seems sound to me.

Or is temperature the problem? The hydrogen would be superheated by the ram compression effect / friction - so I guess you'd need some pretty clever thermal management tech...

...thermal management tech a little like the stuff that pretty much every single fictional spacecraft must have anyway, of course... (the heat is dumped into jump space donchaknow)

[Anthony]

Originally Posted by Timolas

I may be missing something; but why is Traveller style fuel skimming unrealistic? Wouldn't it be a little like aerobraking only you have your fuel scoops wide open?

Sure, but if you're at a level where you can collect meaningful amounts of fuel, drag will be so high that you will leave orbit.

[Mgellis]

Since spacecraft in Traveller have contragravity, maybe "skimming" is simply a matter of lowering oneself into the atmosphere until you can collect enough hydrogen.

With a large gas giant, if your thrusters don't provide enough acceleration, you might not be able to hover, so you might have to "skim" by dropping down into the atmosphere in a hyperbolic orbit and then boosting away again before you slow down too much and plummet to your doom. If a ship can boost at 1 gee indefinitely, it's probably not too hard to achieve escape velocity pretty quickly.

(It's probably a lot easier to just shovel ice into the fuel processor and crack it into hydrogen and oxygen. There will almost always be plenty of ice in a solar system.)

Just a thought...

Mark

[vicky_molokh]

I guess it depends on the local g (small-g, that is) at the altitude where helium density is meaningful. No idea how they correlate, though.

[Figleaf23]

If I recall my old black soft-cover, spine-stapled Traveller books correctly, it was only streamlined ships that could refuel from a gas giant, and thus 'skimming' implied aerodynamic interaction with the atmosphere.

[Langy]

Gas giant skimming is probably possible - you just need to be going fast enough that you hit the atmosphere, go deep inside it, grab your loot, and get out all without touching your thrusters. If you don't have reactionless drives it's possible (and likely probable) that you won't get enough utility out of the gas you 'skim' to pay for the fuel used to get it. If you have a reactionless drive, you're in luck though - with one of those, you can probably do gas giant skimming quite easily for fuel. It's just not realistic, because reactionless drives aren't realistic either.

[Anthony]

Originally Posted by Mgellis

Since spacecraft in Traveller have contragravity, maybe "skimming" is simply a matter of lowering oneself into the atmosphere until you can collect enough hydrogen.

Sure, but once the words 'contragravity' or 'reactionless thrusters' enter the discussion, 'realistic' has left.

[vicky_molokh]

Originally Posted by Anthony

Sure, but once the words 'contragravity' or 'reactionless thrusters' enter the discussion, 'realistic' has left.

And 'fuel' gets . . . irrelevant?