Re: World building: implications of counter gravity

> If all your Handwavium Drive does is produce an equal and opposite
force
> to the local gravity vector, then that just means that you've negated
> gravity -- all gravity -- on your ship. So you won't stay in orbit,
for
> instance, which is great for leaving orbit (but not so good for
getting
> into it), but tricky if you actually want to go somewhere, because
> you'll have to be pointing in exactly the right direction when you
turn
> it on, and it won't speed you up (or slow you down) at all.

The HD drive is not intended to be the only drive in use. My thought was
that it's a launch technology only. Interplanetary spaceships would be
built in orbit and never land on planets, so they'd use a different
drive
technology altogether.

> Unless, of course, you can throttle the thing and/or vector it. If
what
> the magnitude of the local gravity field does is control the magnitude
> of the thrust that you can produce without putting restrictions on
where
> it's pointing, and the thrust can be greater or lesser than the local
> gravity, then you've got something that's not unlike a rocket with
> endless fuel -- just one where the thrust produced is smaller out in
> space than near a mass.

I'm thinking throttle magnitude but not vector.

Originally I'd intended that space travel, as opposed to launch, would
need
rockets and/or ion drives. It hadn't occurred to me that it would work
for
interplanetary travel as a very low thrust drive too.

> That works fine for planets, but you'd have to run some numbers to see
> how the HD would work with smaller masses like, say, the asteroids.

I'm fine with the HD only working well with planets. The setting I'm  
thinking
of is a plausible near future / RocketPunk style (well, baring the one	
miracle
allowed that is the HD drive itself) where there are still rockets  
(possibly
nuclear now we can launch heavier payloads) and ion drives.

-- 
	 cheers,
	 Hugh Fisher