Exoplatz.org>Farred |
Exoplatz.org>Farred |
| Line 1: |
Line 1: |
| − | {{Move2space}} | + | {{Goto space}} |
| − | There are many upper stages in geosynchronous transfer orbit (GTO), at perigee
| |
| − | they have a velocity of about 10.5 kilometres per second, although this
| |
| − | reduces gradually over years as they slowly decay.
| |
| − | | |
| − | If a suborbital vehicle could attach a [[tether]] to one of these stages at
| |
| − | perigee, it could be towed most of the way into orbit.
| |
| − | | |
| − | To get into LEO requires 7 km/sec.
| |
| − | | |
| − | If the payload and the stage are equal mass, then the payload would be
| |
| − | accelerated by 5 km/sec and the GTO stage would be decelerated the same
| |
| − | amount.
| |
| − | | |
| − | Accelerating by 5 km/sec requires about 50 G acceleration for ten seconds,
| |
| − | which would traverse a distance of 25 kilometres (the length of tether
| |
| − | required).
| |
| − | | |
| − | Alternative profile would factor by ten, e.g. 500 G for one second,
| |
| − | traverses 2.5 kilometres (shorter length of tether but higher stress).
| |
| − | | |
| − | The tether would be on a spool with a controlled resistance (e.g. friction
| |
| − | brake, or dashpot, or E-M brake) to soften the initial jerk at contact,
| |
| − | then, pay out the tether at the right rate to control the acceleration to
| |
| − | the planned profile.
| |
| − | | |
| − | The practicalities of attaching a cable to an object moving at 10.5 km/sec
| |
| − | are daunting. In this profile the suborbital vehicle would already need to boost itself to 2 km/sec, as the 5 km/sec is not enough to reach orbit. Therefore the relative speed would be 8.5 km/sec (2km/sec less).
| |
| − | <br>
| |
| − | <br>
| |
| − | Capture perhaps via a light weight structure made of a 3-D web of kevlar
| |
| − | strands (or something stronger), like a large bullet proof vest in which the
| |
| − | GTO stage becomes embedded. Size, maybe a few hundreds metres across. The
| |
| − | webbing could be within an inflatable sphere a few hundred metres diameter,
| |
| − | or alternatively shaped as a tetrahedron for simplicity of geometry.
| |
| − | <br>
| |
| − | The mechanics of high speed collisions are difficult to analyze. At such
| |
| − | speeds, the flexibility of the strands become irrelevant, they behave more
| |
| − | like solid bars. The stage would be severely damaged, one would need to
| |
| − | devise a configuration which would not shred the GTO stage into a zillion
| |
| − | fragments. The kevlar strands would probably be stronger than the stage
| |
| − | material.
| |
| − | <br>
| |
| − | Wikipedia reports that some remarkable new developments are emerging for new
| |
| − | materials being used in bullet proof vests.
| |
| − | <br>
| |
| − | http://en.wikipedia.org/wiki/Bulletproof_vest
| |
| − | <br>
| |
| − | Researchers in the U.S. and separately in the Hebrew University are on their
| |
| − | way to create artificial spider silk that will be super strong, yet light
| |
| − | and flexible.
| |
| − | <br>
| |
| − | American company ApNano have developed a nanocomposite based on Tungsten
| |
| − | Disulfide able to withstand shocks generated by a steel projectile traveling
| |
| − | at velocities of up to 1.5 km/second. During the tests, the material proved
| |
| − | to be so strong that after the impact the samples remained essentially
| |
| − | unmarred. Under isostatic pressure tests it is stable up to at least 350
| |
| − | tons/cm².
| |
| − | <br>
| |
| − | Most upper stages are composed of Aluminum alloys (softer than steel), with
| |
| − | some graphite composites.
| |
| − | <br>
| |
| − |
| |
| − | ==See Also==
| |
| − | *[[List of Propulsion Systems]]
| |
| − |
| |
| − | {{cleanup}}
| |
| − | [[Category:Transportation]]
| |
| − | [[Category:Components]]
| |
| − | [[Category:Hardware Plans]]
| |
