5 ms·
With some exceptions, depending on how you define reaction-less: https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly
by chris_va 8y ago
With some exceptions, depending on how you define reaction-less:
https://en.wikipedia.org/wiki/Pioneer_anomaly https://en.wikipedia.org/wiki/Pioneer_anomaly
- gilbetron 8y agoThat's not a reactionless situation, there is an asymmetry of photons causing the acceleration.
- chris_va 8y agoYes, of course, but there is no finite propellant being consumed.
- danbruc 8y agoThe photons come from the decay heat of the plutonium in the radioisotope thermoelectric generator, so that is a finite propellant being consumed.
- chris_va 8y agoA theoretical EM-drive would run on electricity, as well, so thus wouldn't be propellant-less? Well, assuming one can violate only one law of physics at a time, this is just semantics.
- gilbetron 8y agoThere is nothing coming out of the EM-drive, it just creates a force, which is why it would be awesome.
- roywiggins 8y agoNo, it is different. Photon drives are like a reactionless drive in that you are not expelling matter, but photon drives are emitting mass/energy in one direction and moving in the other and conserve momentum. Reactionless drives just produce force, pushing off "nothing." They violate conservation of momentum and break physics as we know it pretty conclusively.
- trhway 8y agoThey push off the whole Universe. They go in one direction, the Universe - much slower, in the opposite, and thus momentum is conserved :)
- danbruc 8y agoI am not sure if you are joking...but one should not imagine the situation like a tiny space ship inside an egg pushing against the egg shell from within.
- spartanatreyu 8y agoThe photons would be the "finite propellant". (However strained a term that is.)
- lopmotr 8y agoI think you do have a good point. Of course it's not reactionless like the EM drive, but in practice, what's the difference? Both require a power source and both can continue providing thrust forever without running out of reaction mass as long as they have that power source. Even the EM drive, if it works, would still need an RTG or solar panels or something to power it, and that would still limit its use for interstellar travel.