Monday, January 29, 2007


SE's Initial Tether Implementation 
Relies on Risky Rockets.
Initial Space Elevator (SE) system requires risky rocket launches to put both cable and materials into LEO; then, someday transit via complex orbital strategy to GEO. Space Elevator Enterprise plans to eventually use initial SE to deploy subsequent SEs. HOWEVER, SE's initial implementation must use risky rockets which occasionally explode and always cost a lot.

By contrast, TE Solution
Never Needs Risky Rockets.
Riding a high speed particle beam projected from Base Station, Beam Rider vehicles could accelerate from surface to midway to GEO; thence, decelerate to GEO. With propulsive force of only 1 tenth G, Beam Rider could arrive at GEO in 200 minutes (much quicker than the 7 days travel time for SE's traditional tether climber). Without rockets, initial Beam Rider and numerous payloads could safely "park" at GEO directly above Base Station; then, they could wait as long as required until all GEO Node components arrived for assembly.
As this generation's moon shot, the proposed space elevator (SE) will provide much better access to space than possible from tanks of combustible liquids; huge benefits will accrue to the world's science and economy.  Much more cost effective than other "mega-projects", it could yield gigantic economic benefits, an enormous incentive to an enterprising group of entrepreneurs.

The space elevator concept is now taken seriously at NASA, as it faces both shrinking budgets coupled with growing public expectations. NASA could give this project to qualified private partners to get done much faster. Thus, a private enterprise could and should undertake it.

This international mega-project requires global cooperation, perhaps the greatest challenge.
1) Assemble SE satellite (SE-Sat), a massive space system, in LEO.
2) Move to GEO by efficient rockets, Once there, SE-Sat assumes role of GEO Node. 3)  Deploy initial "seed" tether: 
------one end inward towards Earth.
------at same time, other end outward.
4) Completed tether must balance all longitudinal forces at the GEO node.
Space Elevator Satellite (SE-Sat) is an 80 ton deployment satellite with many fuel tanks. At Low Earth Orbit (LEO), SE-Sat must on-load a huge spool of tether fabric (likely CNT); then, continue on to the Geosynchronous Equatorial Orbit (GEO) for bidirectional deployment.  Components include:
Tether as Payload: huge spool of tether ribbon material (likely CNTs)
• Structural Elements include following:
---1) Series of propellant tanks
---2) Tether release mechanism.
• Power Subsystem: SE-Sat will use light weight, solar cells with high efficiencies.
②  Use thrusters to elevate SE-Sat to GEO.
From Low Earth Orbit (LEO), the initial Space Elevator Satellite (SE-Sat) can use thrusters to accelerate and decelerate to GEO.

Upon arrival at GEO, the upper module (eventually to become the Apex Anchor, AA) can separate from the lower module (GEO Node) and starts to deploy the tether.
③  Carefully coordinate 
2 way tether deployment of initial "seed" tether:
---Tidal forces (gravity and centrifugal) balance out by simultaneously pulling the cable both towards and away from Earth to balance the elevator at Geostationary Equatorial Obit GEO). 
---As the bidirectional cable deploys, orbital tendencies forces cause the Out-Link portion of the cable to lag the GEO Node and the lowered Up-Link portion to lead. To mitigate this effect, AA and Space Tug can use on board thrusters as required.
Subsequent Treatments. Before tether can support operational, 6 mT climbers with 14 mT payloads, specialized "baby" climbers will add more CNT fabric to transform the tether from a skinny, seed tether to a robust operationally tether.
Traditional SE tether  is a huge, complex project.  SANITY CHECK: From initial construction until operational, tether deployment will likely take a duration of decades.  Fully deployed tether is securely anchored to the Marine Anchor (MA), a collection of Floating Operational Platforms (FOPs) on a designated oceanic, equatorial location. It stretches upward to GEO Node; thence, outward to the Apex Anchor (AA).

A fully operational AA calls for following functionalities:
  computational capability,
  thrust capability,
  fuel storage [with refueling ability],
comm links to GEO Node, MA, and  designated satellites.
 release customer payloads for orbital and interplanetary missions.

NOTE: Centrifugal forces of AA and Out-Link tether must balance out the gravitational forces along the Up-Link tether.  Net longitudinal force at GEO Node must be zero.
Upon completion of initial construction, the initial filament is connected from GEO Node to both MA and AA.  However, this nascent tether is not yet strong enough to handle operational climbers (20 tonne mass). Thus, follow-up construction requires smaller  climbers to add much more CNT material with hundreds more transits on the tether. NOTE: Suspension bridges have long been built by a similar method.

Once operational, tether will require continuing maintenance by the operational climbers.  As these climbers go up the tether, they must thoroughly check the fabric for defects and supply fabric and agents (TE proposes "nanobots") to fix them.

SANITY CHECK:Even if tether deployment proceeded perfectly, we must still consider overwhelming likelihood that any taut tether can "snap" at anytime. Several massive Carbon Nano-Tube (CNT) strands, (each thousands of kilometers in length) careening around the planet like a snapped rubber band could be a terrible man-made catastrophe.
During every tether transit, climber inspects ribbon; then, repair as required.
Replace very long, physical cable with a "virtual" cable of ions.  Thus, the permanent tether and associated risks can go away. Replace the climber with a "beam rider" vehicle to use a high speed, particle beam to go from Earth's surface to the GEO platform.

• Constructing Base Station's particle accelerator will likely take decades similar to tether infrastructure.
•  Mass mfg of many beam riders will likely take similar size effort as the tether climbers.  
• Beam riders (200 minutes travel time) will travel much quicker than tether climbers (1 week travel time) to GEO Node.
•  Virtual tether (ion beam) can turn on/off as needed to propel Beam Rider; however, physical tether (CNT fabric) must remain in place and taut regardless of how many climbers are on it.
LIKELY TETHER HAZARD: After inevitable tether "snap", thousands of tonnes of CNT strands might fall on the Earth.
ION BEAM HAZARD:Slight concern about stray particles causing cosmetic damage.
Ion Beam Construction Considerations
Subsequent tethers can be built with components delivered by initial tether. HOWEVER, initial tether depends on risky rockets to reach GEO. Such dependencies disappear:
if SE uses particle beams to propel vehicles from Earth to midway point.
if SE uses fast Beam Riders as their transport vehicles.

Thought Experiment (TE) assumes an ocean based "particle accelerator" sends a constant beam of high speed particles to propel the Beam Rider with following features:
TE proposes Beam Rider use a large magnetic field to receive collective momentum from high speed particles; thus, "ride the beam" to midway point.
TE also proposes Beam Rider store a portion of collected particle beam ions in the vehicle's tokamak engine for future use during deceleration phase.
To decelerate from midway, TE proposes Beam Riders use on board cyclotrons to emit protons from tokamak.

TE further assumes that initial Beam Rider payloads could "park" indefinitely at GEO orbit directly above Base Station with no platform.  Eventually, a platform, GEO Node, would be assembled, and subsequent Beam Rider payloads could go directly to it.  Thus, same particle beam and same Beam Riders could deliver initial components to GEO for very first mission as well as subsequent components for subsequent missions.

Thus, no need for risky rockets, not even for first mission.
Safely nestled among SE support vessels, TE assumes a particle accelerator can generate streams of high speed ions to propel vehicles toward GEO.
Tether climbers slowly pass through the Van Allen radiation belt on their way to GEO; the many hours of radiation dosage would be fatal for humans. Perhaps shielding might help.  Typical radiation shields rely on mass to protect contents, a very heavy solution which decreases payload capacity.  Electromagnetic shielding might be lighter, but it will need a robust power supply which is also problematic.

On the other hand, Beam Riders need only 200 minutes to both accelerate and decelerate entire distance to GEO.  This much shorter travel time greatly reduces radiation exposure to well within tolerable levels for humans.
A permanent, physical tether extending to the heavens could hazard both aircraft and satellites. 
① Aircraft could be diverted by air-traffic controllers. 
② To avoid rupture by an orbiting object, use a movable anchor ("Marine Anchor") for the tether to "dodge" any space object large enough to track. 
③ Some tethers might even be designed to "sweep" the heavens of unwanted space debris. A robust cable could absorb impacts of small debris without breaking. 

On the other hand, Beam Riders ride an ion beam which can energize on demand. At other times, beam is off; thus, no nav hazard when off, and no problem with space debris.
②Avoid Satellites
to Avoid Ribbon Ruptures
Small Space Debris
Can Embed in Tether.
INTERNATIONAL COOPERATION essential since the SE must operate in several international legal zones, ---from the high seas ---to the “international sky” ---to outer space itself. Each zone has unique legal and political challenges.

Though not aligned with any sovereign state, the SE's base station will likely be the most aggressively secured "no-fly" zone in the world. ---Watched internally by sophisticated surveillance.
---Watched from beneath by underwater security, ---Watched at altitude by radar sweeps and fighter patrols, ---Watched from space by nearby satellites. The UN will likely assign these vital functions to highly skilled enterprises to be tasked exclusively with Space Elevator security.
SERVE HUMANITY via relevant international forums; these may include: ISECG and/or UNOOSA.

TRADITIONAL TETHER  is a good start toward non-rocket launch into orbit; however, it requires complex deployments, and the taut tether can snap at anytime, a significant hazard.

INNOVATIVE ION BEAM will have challenges, but it deploys simpler without the "snap" hazard.



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