Reactionless drive ships orbital flight in 3rd ed physics?

[evilDictatorInTraining]

Originally Posted by dcarson

Because it needs to fly for a lot longer than any fuel could last.

The distinction between deep space ship and planetary body launch capable is useful for a reason.
I would suggest either one ship have multiple types of engines (one engine with high thrust for lifting off planetary bodies and another with high/unlimited efficiency for long range space travel).
Or more realistically splitting those into two ships.
A shuttle to take you into orbit and a pure space craft (powered by your reactionless drive) to take you quickly to other planets.

[Anthony]

Originally Posted by David Johnston2

Don't think so. Lifting bodies can fly into space provided only that they have enough reactionless thrust to exceed the planetary gravity.

That's what non-lifting bodies can do. A lifting body just needs enough thrust to exceed the drag required to keep from falling, plus the ability to survive extended periods of hypersonic flight.

[Fred Brackin]

Originally Posted by Anthony

That's what non-lifting bodies can do. A lifting body just needs enough thrust to exceed the drag required to keep from falling, plus the ability to survive extended periods of hypersonic flight.

That's while they have enough air to generate lift (or drag). You'll hit practical vacuum eventually and if you're not at a viable orbital speed you'll fall again. Possibly to "skip" off the upper atmosphere and you might have to do this multiple times.

Only the unavailability of sufficiently powerful reactionless drives would make this a truly desirable option.

[Anthony]

Originally Posted by Fred Brackin

That's while they have enough air to generate lift (or drag). You'll hit practical vacuum eventually and if you're not at a viable orbital speed you'll fall again.

Lift (and drag) scale with velocity^2 * atmospheric density, so you just stay at whatever altitude (and atmospheric density) required for your lifting capabilities. This will allow flying all the way up to orbital velocity, though you'll have a plasma sheath at a certain point, which will cause issues unless you have TL^ hull materials and sensors to go with your TL^ drive.

[johndallman]

The Kármán line is the altitude at which going fast enough to support yourself by aerodynamic lift means you're at orbital velocity anyway.

Of course, that means there's enough drag that you'll slow down pretty fast if you stop thrusting. Flying into orbit like that isn't actually practical, just theoretically describable.