5
$\begingroup$

Is there a way to recover any of the energy of reentry of a Mars lander?

  • Tremendous energy is generated as a craft enters the atmosphere – admittedly over a fairly short time - and only one time.
  • We have seen regenerative braking on various vehicles, starting with diesel-electric locomotives, now electric cars and some F-1 racing cars which are capable of significant energy recover over very short time spans.
  • The recover could be mechanical, thermal or electrical but would have to be worth lugging along a system.

  • For example, an ice supply could be heated to water, saving the energy to do it later on the surface.

  • Water could be converted to superheated steam for some use, either during reentry or later on the surface). It is conceivable that ice freighters (from an asteroid) might be bringing large cargos to the surface. A water or ice system might help cool the reentry shield.
  • An auto rotating propeller might assist in aerodynamic deceleration at a later stage in a reentry, while also storing some energy. Such propellers have been proposed for earth reentry although the thin Martian atmosphere is a problem.
$\endgroup$
  • $\begingroup$ Related, possible duplicate: space.stackexchange.com/q/15001/58 $\endgroup$ – called2voyage Dec 13 '16 at 16:08
  • $\begingroup$ The actual question referenced in the above comment seems to be different than this one, although some of the information in the ANSWERS may be relevant. Thank you for the link. $\endgroup$ – A. Flowers Dec 13 '16 at 16:31
  • $\begingroup$ Propellers don't work beyond Mach 1. $\endgroup$ – David Hammen Dec 13 '16 at 17:42
  • $\begingroup$ What unobtanium device are you going to use to store this immense amount of energy? Consider, for example, the reentry of an Apollo spacecraft, which needed to slow down from 11 km/s to near zero. With a mass of 5560 kg, that represents 336 gigajoules of energy that were mostly dumped into the atmosphere. That's the amount of energy in 8 metric tons of oil. Atmospheric breaking enables a spacecraft to not use thrusters for much of the landing. $\endgroup$ – David Hammen Dec 13 '16 at 18:21
  • 1
    $\begingroup$ Looking back, I can see that this question would have better been phrased as “How can some of the energy of reentry of a Mars lander be utilized”, which would focus on more modest goals than an attempt to recover a large amount of energy. This puts it more in the league of utilizing hot radiator water to run a car’s heater, or even the windmill driven fuel pump on a Sopwith Camel – important but minor uses of energy. Maybe the case of a landing ice freighter, with tons of ice as cargo, might suggest some possibilities. Converting ice to water would facilitate its offloading at least. $\endgroup$ – A. Flowers Dec 14 '16 at 23:44
3
$\begingroup$

I'm going to say no, not directly. Just one of the many problems is the energy is merely heat. Relatively speaking heat is easy to get, just make a big concentrating solar panel and you have high grade heat all day. What you want to do is preserve the energy in a valuable form: kinetic or orbital energy.

It is hypothetically possible to recover much of the orbital energy before reentry and thus reduce the amount of energy dissipated during reentry - although the energy recovered wont be available to the lander itself. This involves transferring the kinetic energy of the lander to another object in orbit. The basic concept is a Skyhook, while normally conceived as a way of lifting payloads out of Earth's atmosphere, they can also be used in reverse, catching an object which is in a high orbit, swinging it around the anchor and depositing it at lower speeds in the atmosphere. In the process, much of the kinetic energy of the lander is transferred to the skyhook assembly, raising the orbit of the skyhook, that energy can then be later reused to lift another object out of the atmosphere and into orbit, for example a payload destined for Earth.

Of course there would be immense technical challenges to actually building the skyhook and executing the maneuvers, but it is physically possible.

$\endgroup$
  • $\begingroup$ Your point about the general availability of HEAT is pertinent and something I had not adequately considered. I guess the heat would have to be needed in an immediate scenario, in order to this to be remotely worthwhile. $\endgroup$ – A. Flowers Dec 13 '16 at 20:15
3
$\begingroup$

While it would be hard to do, in part because of the very short time, and would be of questionable value, here is a concept for using MHD to do regenerative braking during Mars entry from the generated plasma.

$\endgroup$

Your Answer

By clicking "Post Your Answer", you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.