4 ms·

> In selling away the rocket equation you buy yourself drag. Lots of energy up front means lots of drag. Overcoming that drag means more energy and, hence, more

by arkh 8y ago

> In selling away the rocket equation you buy yourself drag. Lots of energy up front means lots of drag. Overcoming that drag means more energy and, hence, more drag. The middle child of this solution is tremendous G force. Would it be possible and useful to do it with a 2 payloads system: one dumb piece of material first which can take lot of G followed closely by your "fragile" payload using its draft?

jbattle 8y ago
You have to accelerate both pieces to the same speed, which implies (in a rotational launcher), the same G (acceleration). Maybe there's some configuration where the leading payload pushes air out of the way for the first few km (the 'real' payload drafting behind), but the blocking payload isn't given enough energy to reach orbit and falls short. Seems like the following payload would crash into the leading one though.
JumpCrisscross 8y ago
> followed closely by your "fragile" payload using its draft? G-forces [1] are a consequence of acceleration. An accelerating object will experience g-forces in an atmosphere or in a vacuum. ("Drafting" [2] is an aerodynamic process by which a following object exploits a leading object's slipstream to reduce the former's drag.) With a slingshot, the destructive force is the g-force inflicted by the acceleration. (With a rocket, the destructive forces are mostly vibrations and aerodynamic stress.) Note that a slingshot doesn't require lots of Gs. One could use a super-long slingshot to achieve the necessary velocity. But super long is super expensive, so high Gs it is. [1] https://en.wikipedia.org/wiki/G-force https://en.wikipedia.org/wiki/G-force [2] https://en.wikipedia.org/wiki/Drafting_(aerodynamics) https://en.wikipedia.org/wiki/Drafting_(aerodynamics)
- JoeAltmaier 8y ago
  I can imagine a heavy dead weight accelerated in the slingshot. Once released, it drags a cable, carefully laid out at an angle, with the payload attached. That payload would be accelerated into line behind the weight over a brief period. Taking fewer Gs and only once. Very long cables are a lot cheaper than very large slingshots? Anyway just thinking out loud.
  - JumpCrisscross 8y ago
    > Once released, it drags a cable, carefully laid out at an angle, with the payload attached Unless your cable were elastic, this would not materially change the payload's acceleration. That said, you might find skyhooks [1][2] interesting. [1] https://en.wikipedia.org/wiki/Skyhook_%28structure%29 https://en.wikipedia.org/wiki/Skyhook_%28structure%29 [2] http://adventuretime.wikia.com/wiki/Skyhooks http://adventuretime.wikia.com/wiki/Skyhooks
    - JoeAltmaier 8y ago
      Of course it would. Like a lever has different forces on the short end and the long end, the cable could be curved and lengthened to control exactly the rate of transfer of momentum between weight and payload.

by arkh 8y ago

jbattle 8y ago

You have to accelerate both pieces to the same speed, which implies (in a rotational launcher), the same G (acceleration). Maybe there's some configuration where the leading payload pushes air out of the way for the first few km (the 'real' payload drafting behind), but the blocking payload isn't given enough energy to reach orbit and falls short. Seems like the following payload would crash into the leading one though.

JumpCrisscross 8y ago

> followed closely by your "fragile" payload using its draft? G-forces [1] are a consequence of acceleration. An accelerating object will experience g-forces in an atmosphere or in a vacuum. ("Drafting" [2] is an aerodynamic process by which a following object exploits a leading object's slipstream to reduce the former's drag.) With a slingshot, the destructive force is the g-force inflicted by the acceleration. (With a rocket, the destructive forces are mostly vibrations and aerodynamic stress.) Note that a slingshot doesn't require lots of Gs. One could use a super-long slingshot to achieve the necessary velocity. But super long is super expensive, so high Gs it is. [1] https://en.wikipedia.org/wiki/G-force https://en.wikipedia.org/wiki/G-force [2] https://en.wikipedia.org/wiki/Drafting_(aerodynamics) https://en.wikipedia.org/wiki/Drafting_(aerodynamics)

JoeAltmaier 8y ago
I can imagine a heavy dead weight accelerated in the slingshot. Once released, it drags a cable, carefully laid out at an angle, with the payload attached. That payload would be accelerated into line behind the weight over a brief period. Taking fewer Gs and only once. Very long cables are a lot cheaper than very large slingshots? Anyway just thinking out loud.
- JumpCrisscross 8y ago
  > Once released, it drags a cable, carefully laid out at an angle, with the payload attached Unless your cable were elastic, this would not materially change the payload's acceleration. That said, you might find skyhooks [1][2] interesting. [1] https://en.wikipedia.org/wiki/Skyhook_%28structure%29 https://en.wikipedia.org/wiki/Skyhook_%28structure%29 [2] http://adventuretime.wikia.com/wiki/Skyhooks http://adventuretime.wikia.com/wiki/Skyhooks
  - JoeAltmaier 8y ago
    Of course it would. Like a lever has different forces on the short end and the long end, the cable could be curved and lengthened to control exactly the rate of transfer of momentum between weight and payload.