3 ms·

> Using a moving black hole as a gravitational mirror, kinetic energy from the black hole is transferred to the beam of light as a blueshift and upon return the

by mabbo 4y ago

> Using a moving black hole as a gravitational mirror, kinetic energy from the black hole is transferred to the beam of light as a blueshift and upon return the recycled photons not only accelerate, but also add energy to, the spacecraft. Okay, so, not something NASA needs to investigate immediately then.

lallysingh 4y ago
But probably a great add-in to a sci-fi story.
- crdrost 4y ago
  I think the best approach to using this mechanism in sci-fi would involve using it for braking rather than sending. The problem with sending is that you want the black hole traveling fast in the direction that you are going and this requires creating a binary black hole system somewhere in the close interstellar neighborhood of the star you want to come from (since if it's 4 light years away you need to have already solved interstellar travel in order to travel between stars with this mechanism...) The engineering for using one of these to brake against, just requires one to make a smallish black hole that is falling into a gas giant planet and consumes a large chunk of it to form a black hole orbiting your star. Then anyone who wants to visit you can use much more of their fuel to accelerate to a much higher speed with the confidence that they can use your black hole to slow down as they are entering your system.
TrevorJ 4y ago
Out of all the theoretical propulsion systems, THIS is pretty much the only one that we know would work without novel (made up) physics like negative energy, etc. In fact, I don't really think we'd need new/novel technology to test this. Biggest hurdle is getting into the right position with respect to a black hole to do this in the first place.
- mrDmrTmrJ 4y ago
  There are much simpler propellant-free ideas for producing relativistic speeds that respect known physics. I particularly like the resonant Photonic Laser Thruster: https://sci-hub.se/https://doi.org/10.1016/j.phpro.2012.08.026 https://sci-hub.se/https://doi.org/10.1016/j.phpro.2012.08.0... Indeed, the author had already done a bench-top demonstration: https://ykbcorp.com/photonic-laser-thruster/ https://ykbcorp.com/photonic-laser-thruster/
- naasking 4y ago
  > Out of all the theoretical propulsion systems, THIS is pretty much the only one that we know would work without novel (made up) physics like negative energy, etc. Light sails are totally feasible too, depending on whether you consider them a propulsion system.

by mabbo 4y ago

lallysingh 4y ago

But probably a great add-in to a sci-fi story.

crdrost 4y ago
I think the best approach to using this mechanism in sci-fi would involve using it for braking rather than sending. The problem with sending is that you want the black hole traveling fast in the direction that you are going and this requires creating a binary black hole system somewhere in the close interstellar neighborhood of the star you want to come from (since if it's 4 light years away you need to have already solved interstellar travel in order to travel between stars with this mechanism...) The engineering for using one of these to brake against, just requires one to make a smallish black hole that is falling into a gas giant planet and consumes a large chunk of it to form a black hole orbiting your star. Then anyone who wants to visit you can use much more of their fuel to accelerate to a much higher speed with the confidence that they can use your black hole to slow down as they are entering your system.

TrevorJ 4y ago

Out of all the theoretical propulsion systems, THIS is pretty much the only one that we know would work without novel (made up) physics like negative energy, etc. In fact, I don't really think we'd need new/novel technology to test this. Biggest hurdle is getting into the right position with respect to a black hole to do this in the first place.

mrDmrTmrJ 4y ago
There are much simpler propellant-free ideas for producing relativistic speeds that respect known physics. I particularly like the resonant Photonic Laser Thruster: https://sci-hub.se/https://doi.org/10.1016/j.phpro.2012.08.026 https://sci-hub.se/https://doi.org/10.1016/j.phpro.2012.08.0... Indeed, the author had already done a bench-top demonstration: https://ykbcorp.com/photonic-laser-thruster/ https://ykbcorp.com/photonic-laser-thruster/
naasking 4y ago
> Out of all the theoretical propulsion systems, THIS is pretty much the only one that we know would work without novel (made up) physics like negative energy, etc. Light sails are totally feasible too, depending on whether you consider them a propulsion system.