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With this I mean using elastic energy to land and possibly reuse this energy at takeoff. So that the "spring" will remain in the compressed state between landing an takeoff by locking it in to place.

So I refer to storing energy in the landing gear, instead of just absorbing and dissipating it.

The advantages I can think of are:

  • No/less need rockets at touchdown, so less dust will be blown from the surface into a cloud at the landing site.
  • Less fuel is needed to land and takeoff.
  • Mechanical potential energy seems more reliable that rocket engines, which have to pump fuel, ignite, ect.

The disadvantages I can think of are:

  • If it fails it can have more devastating results as a leak in a fuel tank, since the fuels needs to be combined and given activation energy for it to release its potential chemical energy.
  • The fuel needed to bring the "spring" with you might be more than you gain from it.
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  • $\begingroup$ fibonatic, your post is not entirely comprehensible. Would you please re-write it? $\endgroup$
    – Deer Hunter
    Commented Dec 23, 2013 at 4:59
  • $\begingroup$ @DeerHunter, they seem to be asking harnessing Regenerative brake as used in automobiles for spacecraft landing and takeoff. $\endgroup$
    – James Jenkins
    Commented Dec 23, 2013 at 11:53
  • $\begingroup$ @James Jenkins, that is indeed what I am asking. $\endgroup$
    – fibonatic
    Commented Dec 23, 2013 at 15:07
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    $\begingroup$ If anyone has access to this paywalled document on Gear-Part-Flying Mechanism (GPFM), could you please check if it's relevant to the question asked? I believe it might be, it discusses conservation of kinetic energy on soft-landing, but I'm not entirely sure it's meant to be reused later for launch too. Cheers! $\endgroup$
    – TildalWave
    Commented Dec 23, 2013 at 17:09

2 Answers 2

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An integrated single vehicle regenerative brake would not be feasible. In short because you would not be able to gain any more lift then you could capture at landing. So if you have spring loaded landing legs 100 feet long, the most lift you you get is about 100, which on a journey to orbit is insignificant.

There are several ground (semi ground) based solutions that have been considered for recapturing energy between launch and landing. A good overview of one solution is described in Can a "free launch" from a space elevator really be free?

Pretty much any ground based launch system, can in theory be used to recapture energy from returning vehicle if designed with that in mind. But there are difficulties; consider an example with the Space Gun using a magnetic propulsion similar to trains could recapture some of the energy, but this would require that a incoming vehicle enter the "barrel" of the gun at high speeds.

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  • $\begingroup$ I'm not sure if the intro part on the ability to conserve kinetic energy from landing is just awkwardly put, or plain wrong? What do you mean with "...the most lift you you get is about 100" with respect to the length of the landing feet? If we assume such a spring being a part of the launch platform that stays behind (easier to imagine, but not necessary), why would the released energy stored in them on landing be only sufficient for a lift equal to its length? $\endgroup$
    – TildalWave
    Commented Dec 23, 2013 at 17:02
  • $\begingroup$ I second TildalWave, the energy in the springs is limited to the acceleration you're willing to accept and mechanical limits, not the height of the springs. With springs of unobtainium and a gun-rated payload you could "soft" land on the moon from an impacting "orbit" and then take back off into such an orbit with less than 100' of spring. Design it right and you could bounce back and forth between the lunar surface and an orbiting ship and only use rockets to make up for the heat losses in the springs. $\endgroup$
    – Loren Pechtel
    Commented Dec 23, 2013 at 17:56
  • $\begingroup$ With device as part of the ship, you can only collect the energy within a range that is directly conected to the ship. So if you have feet that touch at 1 foot. All of the energy collected in that foot is what you will have for take off. Assuming a you are will to have equal g fources on take off and landing. 1 foot at 10 G's gets you 10 feet of lift before you start falling back, 100 feet at 10 G's gets you 10 G's of lift at 100ft (acceleration) or maybe 1000 feet of lift before you come crashing back. $\endgroup$
    – James Jenkins
    Commented Dec 23, 2013 at 20:11
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    $\begingroup$ @JamesJenkins Note that I said a gun-rated payload--something that can take some really extreme g forces. You can't do it on a body with atmosphere anyway. If I'm not messing up the math one meter springs and 2,400 G's will permit you to land and take off from the moon. $\endgroup$
    – Loren Pechtel
    Commented Dec 24, 2013 at 18:50
  • $\begingroup$ @LorenPechtel that is interesting. Is there any science on the materials or design that would contain that much energy? $\endgroup$
    – James Jenkins
    Commented Dec 24, 2013 at 18:55
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The Philae lander, part of ESA's Rosetta mission to land on a comet, uses the elastic energy from the landing to drive spikes into the ground. Each landing leg contains a threaded spike, the landing compresses the landing leg, this motion is converted to a rotation and extension of the spike.

Presentation containing image of the spikes. Video explanation using a Lego model of Philae.

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  • $\begingroup$ Good catch. However, Philae uses the spring only for landing. On he other hand, [Fobos-Grunt][1] would have used a spring-loaded mechanism for takeoff of the sample return vehicle. However neither system uses the spring to store energy collected during landing for takeoff. [1]: en.wikipedia.org/wiki/Phobos-Grunt $\endgroup$
    – oefe
    Commented Jan 19, 2014 at 22:09

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