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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10441
Loc: Amargosa Valley, NV, USA
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Quote:
Actually the benefits are pretty small. Even "high subsonic speed" would be less than 5% of orbital speed, which means it has less than 0.25% of the kinetic energy needed to get into orbit.
But what I'm thinking of is the amount of propulsion mass required to boost a payload even that far.
During the launch of the shuttle, how much of the shuttle's fuel/oxidizer mass is used up getting it to the first seven miles in altitude?
Using atmospheric oxygen and aerodynamic lift for that portion of the flight could change the fuel/payload ratio at least enough for some significant economies.
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"S.O.E." (Sauron's Other Eye) 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Next Project: The "Eye of Sauron" Observatory!
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Kobayashi
sage
Reged: 07/10/08
Posts: 291
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Quote:
The energy saving is a bit more than that. Low earth orbit is ~100 miles...
It's more like 200 miles for a stable orbit. ISS orbit is about 210 miles.
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-- Ken Kobayashi
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Jay_Bird
professor emeritus
Reged: 01/04/06
Posts: 678
Loc: Nevada 36N 115W
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Real progress to a track or an elevator would be exciting.
I think Dave might be driving at something like this, a track, booster sled, and orbiter.
Track gets payload to supersonic speed and maybe above 10,000 - 20,000 feet at end of track
"Sled" on track is something like an oversized Blackbird that can lightup jets at end of track and get to high single digit Mach number and something like 20-25 miles elevation before flying back to launch center
Orbiter is a shuttle-like rocket that then 'only' needs the fuel to get from Mach 5-6 or so to Mach 25 orbital speed, without fighting much air drag.
Certainly not easy (especially cost of building the the track) but eventually will the huge track or elevator fixed costs pay out compared to expendable rockets? (one quote 'piling fuel on top of fuel to put a pea in orbit, maybe from Ted Taylor) when averaged over many, many trips to space...
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'these things stand like stone - kindness in another's troubles, courage in your own' Gordon
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