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