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What's New ?
Go to Recent Changes for the webpages that I've been working on lately. I'm always tinkering with the design, my notebooks have a lot of information and ideas I have not formally written about and illustrated yet.
The 2009 paper was a cleanup and expansion of the 1993 AIAA paper. Since then, I've worked on many improvements:
Velocity Transformer Track
Segmented Bolt Rotor
Some (needs reference!) have written about a tether hanging from a heavy orbiting station. An ascending vehicle matches velocity with the bottom of this rail, then climbs up, perhaps powered with acoustic energy on the tether. This will rob the station of momentum and angular velocity, but that can be added back with slow, high efficiency electric engines (VASIMR engines with cheap argon propellant, perhaps).
A CaptureRail climbing capture tether arrives with a higher velocity, and decellerates all the way up a relatively stiff rail. That can require no climb energy, and slightly less angular velocity correction at the station.
A vertical spaceport resembling the 1979 Arnold/Kingsbury horizontal capture spaceport. This will capture (and add angular momentum to) a frequent stream of fast upbound vehicles launched from the launch loop. Unlike the LEO spaceport, the vehicles will shed energy and slow down in relation to the spaceport; it will be a net energy generator. This will require a significant inclination on a launch loop at 8°S latitude or (vectoring rocket thrust during descent), so the equatorial plane crossing is at GEO altitude. Inclination change will be cheaper at the apogee of a high orbit, but that might add hours or days to the ascent.
A launch loop can launch slightly faster than escape velocity, but it cannot produce as much angular momentum as a GEO orbit. Many cargo vehicles will also be launched into a high, slow orbit, where a relatively small impulse at apogee can add a lot of angular momentum. These vehicles will be captured by the GEO Spaceport on descent.
Geosynchronous Construction Orbit
Before a capture system is built in a synchronous location in GEO, or for the assembly of interplanetary missions requiring a lower perigee, we can launch to multiple highly elliptical 86164 second period Construction Orbits with a perigee of 8378 km (2000 km altitude) and a perigee of 75950 km. These orbits are synchronized with the daily availability of the launch loop (within a 15 minute window) for the delivery of multiple payloads.
Interplanetary missions should start at a low perigee for maximum escape velocity. A low perigee also permits a "12 hour return" for crew rotation and medical emergencies given a relatively small 114 m/s delta V at apogee. Two more delta V's will put the vehicle into a circular geostationary orbit.
80 km track, 30 km West Station
With a pointy nosecone, the hypersonic drag for an acceleration path at 80 km is acceptable, the lower altitude reduces stabilization cable weight, and the 33 times higher atmospheric density should reduce space debris flux by a corresponding factor.
Vehicle drag power and heating is proportional to velocity cubed. Vehicles will increase acceleration slowly from West Station, and increase speed as they gain altitude and encounter less drag. A lower altitude west station allows it to be heavier, makes maintenance and staff "commuting" easier, and reduces the time and expense of the west station elevators.
Acoustic Elevators from the Surface to West Station
I presented this at the 2017 ISEC Space Elevator Conference (ADD LINK to paper). If a very strong tether material ever becomes available, it will be stiff enough to make a superb "tin can telephone" high power vibration transport to an ascending climber.
- Sadly, carbon nanotubes are superlubricious (ADD LINK to Huang paper) and will never be both strong and crosslinked enough to make a Space elevator to GEO and behond. Graphite is a lubricant. However ...
A 30 km high elevator to West Station can be made from Kevlar, or from stronger (but more expensive) materials like Torayca T1100G ( ADD LINK to datasheet ). A Kevlar acoustic elevator must be much stouter, but can lift a vehicle in a few minutes. A launch loop will need dozens of these elevators.
This replaces recent "loop and pulley" elevator approaches.
Server Sky Positioning, Control Information, and Precision Debris Prediction
Return Track Bolt Acceleration and Deceleration