03-05-2023, 06:55 PM | #11 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
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.
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03-05-2023, 07:14 PM | #12 | |
Join Date: Aug 2007
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
Quote:
Only the unavailability of sufficiently powerful reactionless drives would make this a truly desirable option.
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Fred Brackin |
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03-05-2023, 07:51 PM | #13 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
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.
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03-06-2023, 04:51 PM | #14 |
Night Watchman
Join Date: Oct 2010
Location: Cambridge, UK
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
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.
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03-07-2023, 09:10 AM | #15 | |
Join Date: Jul 2008
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
Quote:
Also, why would you stop thrusting? If you reach the Kármán limit flight profile, it doesn't mean you've finished orbital injection, it means that there's no longer much question of whether you can (assuming you're not going to run out of delta-V).
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03-07-2023, 09:26 AM | #16 | |
Join Date: Aug 2007
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
Quote:
We can do a little better than that today but not with a payload-carrying craft. The numbers are already far higher than the theoretical winged orbiters from Space 1e.
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Fred Brackin |
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03-07-2023, 10:14 AM | #17 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
There's a reason this type of discussion is only used for reactionless drive; even if possible in theory, it's a pretty dumb idea with real world rockets.
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03-07-2023, 10:56 AM | #18 | |
Join Date: Jul 2008
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
The appeal, of course, would be to be able to use something much more efficient than normal rockets.
But most concept deep-space rockets likely wouldn't work in atmosphere anyway, or have enough thrust to sustain flight. Quote:
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03-07-2023, 11:03 AM | #19 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
You need enough thrust to exceed your drag, or you slow down (thus failing to accomplish your purpose), and drag is equal to the weight of the vehicle divided by its lift to drag ratio.
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03-07-2023, 11:31 AM | #20 |
Join Date: Jul 2008
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Re: Reactionless drive ships orbital flight in 3rd ed physics?
Yes, but I don't believe the Kármán line calculation cared about that. It was assessing how fast you could survive going and how fast you had to go to not drop out of the sky, not whether you could actually go that fast.
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Tags |
aircraft, reactionless drive, spaceships |
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