skyhook - spacehook
|a nuclear-powered efficient launch-transfer
air-speed-to-space-orbit freight elevator for
The GEO-elevator "rope-trick" design put a counterweight mass beyond Geostationary
Earth Orbit for lifting objects on a sky-cable from Earth surface to 26.2K miles,
6.9K mph, where they would be released in GEO (orbit); -or returned similarly to
Earth;- a simple tall elevator under perpetual high-speed collision threat,
stretching technology by decades and deferring interest in cheap launches.
(It had a cute aside-proposal for launching huge fleets of space-technology personnel,
equipments, supplies, for building spaceships to the moon and beyond, in one decade,
by letting each lifted mass continue beyond GEO to act as a countering weight for the
next up its sky-cable, running a continuous pulley 50/hr, 4 million in ten years ...
using Earth's rotation-momentum to upload a virtual population.)
(It also had a potential advantage of starting the whole process with a thread,
pulling up ever-thicker...till it'd upped the main cable.)
The LEO "pinwheel" required a cubic mile of asteroid core orbiting just outside the
atmosphere over a great circle of the Earth, with 100-mile spokes dipping into
the atmosphere to reach objects waiting aground,- capturing up, throwing them
outside, onward at double orbit-velocity, 41% faster than escape velocity ...
the asteroid also raising Earth ocean tides, tending to cause or trigger earthquakes,
and ultimately eventually entering the atmosphere itself,-- end of exodus, asteroid,
and much of Earth surface-living, under tsunamis.
By separating the space-base from any space-station, and putting the base mass in
MEO (orbit), and raising its elevator bottom floor to high atmosphere altitude at
supersonic jet speed, it becomes contemporarily launchable with a self-growing
capability of uploading megatons and millions of supplies, equipments, astrovoyagers,
by nuclear-power ... for inexpensive arbitrary-duration mission-stays in
regular high-turnover commercial hotel and deep-space launch facility and
research and educational university scenarios ... [*]
* ("Boom-tendency" is lossless energy-exchange orbital mechanics tending to swing a
boom or tethered plumb to full vertical stop; A megawatt is required for reeling-up
the plumb ... well-within the efficiency of affordable, power-abundant,
propellant-conservative, standalone nuclear. The energy imparted as work-done
nuclear-powered hoisting, pumps the station orbit overall.)
- The space-base consists of a high-output nuclear powerplant (standalone megawatt),
comprising most of its mass, redundant cable tanks of nonstick non-snagging cable
(coiled-reeled or scrambled; 1000+ miles each) and an aeroglider bottom-car (attachable
by supersonic jet on the fly), and linear cable-drive motors and brakes, and
digital-radio communication-and-control packages.
- The space-base sends its elevator car down by sending it back, where by orbital
mechanics it descends to forward, drawing the full cable length, thereupon stopping,
and swings down to the high atmosphere, where a supersonic jet attaches the car,
either to itself or to its sky-payload, and lets that swing back up at a few gees
as the cable top (base) continues forward at orbit speed.
- The long ascent to MEO (15 min.) slows the vertical velocity to zero, consumed by
gravity (for base mass 8× transport mass), and the sky-payload then proceeds
to the space-station, higher or lower, in about an orbit.
- The space-base repumps its own orbit by "boom-tendency" swing-dropping and
relifting an elevator car as an energy-plumb. (*)
VANTAGES: (MEO, cf GEO, LEO)
The main disadvantage of any space-elevator is its length of cable exposed to
orbiting debris, --greatly increased in the space age.
- MEO elevator cable total length is feasibly short (1/15th-to-20th of GEO)
- Kevlar™ or ruby thread (AlOx) has sufficient tension strength for
feasible thickness at the elevator's space-base
- Space-base mass can be launched in 3-4 contemporary Space Shuttle missions;
and can then upload more mass to itself if needed
- Air-speed-to-space-orbit elevator velocity difference is similar among MEO options
- The supersonic transport rotates upward to reduce bottom-floor gravity,
comparable to takeoff gees
- It programmably puts the upload destination anywhere,
eg. up to about 1500 miles high for a space station hotel [*]
- The transport's own momentum is recovered regeneratively in departure at the end of
the cable in lower "faster" orbit pulling the space-base forward while slowing itself,
going suborbital, toward vertical
- Additional momentum is gained by pulling the transport back, down faster, reaching
the atmosphere flying supersonic westward instead of eastward; approximating the freight
tons remaining at station orbit speed (for transport mass 1500 mph 6× payload)
- The transport reenters the atmosphere at airflight speed, pushing supersonic
- In case of cable break the transport glides back at "safe" suborbital speed, and
the second twin-elevator sends down its cable
- The cable is easily repairable, needing only tension strength; no tractors, guides,...
- MEO is adaptable to scheduling for orbiting debris,- unlike LEO which keeps its
rotation, and GEO which keeps its position
- (There may be programmable scenarios for operating both elevators simultaneously:
one up, one down)
The main disadvantage of the skyhook itself is scheduling more than one per planet,
ADDITIONAL: (notes, calculations, drag, obstacles)
LEO and MEO cable mass is similar because the swing acceleration, whence the weight, is
inversely proportional to length: the shorter cable must be retroportionally thicker;
Bottom gravity is the same and distributes across the thickness, and is close
compensation for the greater LEO velocity, -But LEO over-the-top velocity, after
less deceleration during shorter ascent, can escape orbit. GEO cable hangs vertically
and supports the full bottom gravity for its entire orbit, --though the cable itself,
weighs less in its higher altitudes.
- At straight vertical hang, the elevator bottom would travel at proportionally
4/5ths MEO speed, (about 13Kmph). Exact atmosphere height is daily changeable, and
five miles overall cable length is a hundred miles lead, six degrees off vertical.
- Ascent vehicles, suborbital in the atmosphere, must advance to catch the elevator
bottom stage car at this forward position, and pull forward, ahead until rotation,-
minimizing atmospheric drag on the fast-moving cable by increasing the leading angle.
- Then subsequently in space, draw potential energy from the base; and once up at
orbit altitude, additional from elevator pull.
- (At the end of the slower base-orbit-pumping-only regime the aeroglider avoids entry,
and elevator power hoists the cable.)
- The space-base loses altitude in lifting the elevator car with the jet sky-payload,
but total mass and extremities remain in orbit.
- The elevator cable remains taut while the vehicle rises high above the base to reach
the station orbit (matching ephemerides).
- On return, braking to "boom-tendency" exact position, elasticity,
powered pullbacks and repeated brakings, affect entry speed.
- The station is a plate-wheel (eg. 100 m dia. rotating twice per minute simulating
.22 gee at its perimeter) orbiting edge-on in a great circle around the Earth,- thus
minizing frontal exposure: Only the tire needs whipple armour.
- Alternatively, To expedite station arrivals and departures, the station and base may
be tethered as a tall tower stabilized by orbital mechanics to vertical orientation:
The velocity difference, both proportional and direct orbital, facilitates transfers
(eg. 100 mile at 1000 differs about 460 mph total), and departing transfer vehicles
drop at 6% gee.
- The -contemporary- disadvantage of MEO is the high density radiation belts,
much less dense at GEO,-- but there are ample technological remedies to come, in terms
of mu-glass shielding, electrostatic repulsion, per NASA design, etc. [*]
NB. The GEO-elevator has a major disadvantage usually undisclosed:
Velocity in GEO is 1.9 mi/sec, much faster than the Earth surface
0.3 mi/sec, that must be gained or lost by each elevator car,--
But without direct horizontal acceleration the proposed fast-scent
cars will swing far, plucking the cable with great mechanical advantage
at 0.26 mph/mile-climb, (0.002 gee at 600 mph, 37-hour trip);-
the Earth base doesn't pull the cable but to sub-gee tension-reel it,
to compensate said swing and low frequency oscillations due to diurnal
GEO-positioning under solar and lunar tidal-draw (and of near planets) ...
the car will sway for enough angle (44 miles at low altitude,- redoubling till high up).
... #2. If a car air-pressure tank ever blows, it may swing wild thousands
of miles freed from its tension-reel, in satellite space.
... #3. If cars travel oppositely, simultaneously, they will contend horizontally:
coming up west, going down east; and in passing, flip over, -unless they crawl passed-
... wilder and weirder than any skyhook, on 20×
longer -exponentially tapered- cable.
* [High-voltage proton "radiation" at MEO is ameliorated by dousing, trapping,
deflecting,- by designs similar to interior surfaces of hot
fusion plasma containment vessels, and designs special for this environment,
eg. superconductive nano-whiskers, trillions per sq'are ("beach fuzz"), maintaining
a free-electron surface cloud at subzero work function where each incoming proton
accelerates thousands of individual electrons, gradually slowing the proton;
or eg. thick heavy high-tesla mu-surfaces deflecting both protons and electrons]
This skyhook-spacehook would be usable on Earth. On the Moon, maneuvering across its
airless surface to catch an elevator car might be less effectual than
but the spacehook might be sufficiently controllable for precision touchdown.
On Mars the thin vacuous atmosphere hampers flight, but precision
touchdown may work as for the moon; On Venus the thick lower atmosphere may support
floating-platform cities in the clouds (54Km up) but its global stormy multiple
jetstreams hamper precision touch-down.
© 2001, 2005