Monday, January 29, 2007

LIFEBOATS


















Since tether ribbons will inevitably rip, it makes imminent good sense to plan emergency return capabilities.
For some scenarios, consider a "lifeboat"; another type of vehicle for payload to make its way back to Earth's surface. Preferably, it will land precisely at the "base station" at the bottom of the tether.
ASSUMPTION: Tether remains intact. This chapter assumes tether sustains damage but remains intact.  Thus,  tether is still taut, but vehicles cannot safely traverse damaged area (i.e. "rip"). In another chapter, TE proposes tether will host numerous nanobots to expeditiously repair any rips; however, practicality compels us to assume that such repairs will take a while and will need testing prior to subsequent climber traffic. 

NOTE: "Severed tether" would have global impacts, and the safe return of climbers would become a trivial priority. Thus, this concern is discussed in a later chapter (still in work).

I. Stranded on Down-Link.


If rip is above climber vehicle,
it might continue a tenuous descent to surface if the rip doesn't completely sever the ribbon.


The option to dismount the ribbon and free fall to the surface would be very useful.



If rip is beneath climber, occupants might wish to dismount tether and free fall to surface. 

Perhaps a combination of jet packs and chutes might safely cushion impact at surface.


If climber is far from Earth's surface, it cannot safely free fall to Earth's surface; thus, it must return to GEO Node. HOWEVER, passengers and payloads may need to evacuate while tether is still in disrepair; thus, a new vehicle type will be needed.



Replace Down-Link Tether with Particle Beam.
① As vehicle approaches Earth, gravitation force grows from .05 g to 1g at surface.
② Earth bound particle accelerator sends high speed, particle beam upward to slow vehicle down during final portion of descent from GEO Node.
Upon departing GEO Node, TE assumes free falling lifeboat's linear velocity toward Earth increases from 0 to about 15 kps just before impacting surface.



Since 15 kps is way too fast, the lifeboat will need a reliable method to slow down for a safe impact.
Virtual Tether: High Speed, Particle Beam. To decelerate lifeboat for safe landing at Earth's surface, TE proposes high speed, particle beam to impart collective momentum against lifeboat's magnetic field extending from bottom.
Perhaps start decelerating at midway (about 20,000 km above surface) for about 30 minutes deceleration time with resultant deceleration force of -1G.
II. Stranded on Up-Link





If rip is above climber, 
climber reverses direction 
to return to base station.








If rip is below, climber might continue Up-Link if GEO Node provides safe haven.







Occupants of Up-Link's GEO Node might need to return to Earth before the ribbon repair is complete.  The traditional return route involves the Cross-Link shuttle to Down-Link's GEO Node to take Down-Link climber on tether back to Earth.



Instead of Down-Link climber, take the lifeboat for a much quicker trip back to Earth.  Lifeboat would accelerate via increasing Earth gravity back to lower LEO; then, 1G decelerate via a particle beam for a zero velocity return at Earth surface. As non-tether Down-Link solution, the lifeboat vehicle would be a much speedier and safer trip back to Earth.
SUMMARY
Down-Link's traditional physical tether uses climber vehicle to grapple ribbon.
Replace with TE's virtual tether and lifeboat which rides Earth gravity to LEO.
At LEO, lifeboat's magnetic "skirt" starts to gather collective momentum
from high speed ions emitted by Earth bound particle accelerator.
CONCLUSION: 
Perhaps Down-Link physical tether is not needed!



VOLUME 0: ELEVATIONAL
VOLUME I: ASTEROIDAL
VOLUME II: INTERPLANETARY
VOLUME III: INTERSTELLAR



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