This is the best explanation I've read so far. Didn't know fuel scooping relied on hydrogen envelopes.
Also I'm well aware of how extreme Neutron Stars/Pulsars are, but good explanations for those who aren't fully informed.
Here's my take on it then.
The ship's drive must get its energy from a source that is capable of supplying really amazing amounts of power. The only things I can think of that are up to the job, and are actually plausible within the bounds of the game universe, are fusion and antimatter. Coal just isn't going to cut it.
We know already that we're not using antimatter to provide energy, so it must reasonably be fusion power.
Fusion reactors (I'm visiting one this afternoon actually! Woo Hoo! It's the JET and MAST facilities at Culham in Oxfordshire
), fusion reactors work best with hydrogen and helium as fuel. There are various isotopes of both that give greater or lesser capability for generating power by methods we're currently aware of. I think Helium 3 is the best but I can't remember why I think that.
OK so our drive system uses a fusion reactor as a power source.
We need to feed the reactor with fuel.
Happily the best fuels are available for free courtesy of the Big Bang and conveniently gathered into large, easily accessible balls by that consummate organiser of things, gravity.
So we can get helium from stars. They started off as pure hydrogen and then merrily fuse that, via a couple of processes, into helium. Newer stars use the end products of old stars (helium and other post-supernova metals and other bits) so they contain helium, hydrogen and a couple of other things in tiny quantities.
We can also get helium from large gas giant planets. That's I think, the best source of helium 3.
So we could fit a device to our ship that allows us to capture parts of the atmosphere's of stars and gas giants. That device would conveniently use magnetic fields to gather in the presumably ionised gas and funnel it to some sort of storage mechanism. That storage thing will remain shrouded in my head for a while until I can think of a plausible way of doing it that fits in with the rest of the universe.
So we need stars or gas giants that have a good supply of hydrogen or helium. That's most of them so we're not going to be short of places to find it.
At the moment I don't think scooping from gas giants is implemented. Maybe in a future release.
An old star will have a higher percentage of what are called "metals" (anything higher in the periodic table than helium, even if they're not actually metals) which will be effective contaminants to the fuel. You're dragging in lithium and beryllium along with the hydrogen and helium. They don't burn so good and are difficult to fuse.
I think this is where the fuel quality thing comes from. If you can get high quality fuel your drive will get more power from the fusion reactor and so you can go further for a given amount of fuel.
It's groovy stuff.
