[HN Gopher] The Halo Drive: Fuel-Free Relativistic Propulsion (2...
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The Halo Drive: Fuel-Free Relativistic Propulsion (2019)
Author : mrleinad
Score : 53 points
Date : 2023-01-13 13:30 UTC (9 hours ago)
(HTM) web link (arxiv.org)
(TXT) w3m dump (arxiv.org)
| mperham wrote:
| Prof. Kipping is well known for his Cool Worlds youtube channel,
| which is fantastic.
|
| He created a video on his Halo Drive idea:
| https://www.youtube.com/watch?v=rFqL9CkNxXw
| college_physics wrote:
| We just need to get close to a moving black hole, then and the
| Universe is our oyster.
|
| Inversely, if we spot heavy intergalactic traffic of aliens
| jumping into halo-drive that is going to be a sure sign there is
| a moving black hole nearby!
| api wrote:
| So wait... this means you can remotely steal energy from a black
| hole? Could this be exploited as a power source?
|
| Obviously wouldn't be possible on human time scales any time soon
| but the fact that physics permits this is interesting.
| Filligree wrote:
| Yup, there are a variety of ways. Probably the most dramatic
| one is the 'black hole bomb', which you should definitely look
| up~
| blamestross wrote:
| Kinda? This let's you remotely steal inertia from rotating
| black hole pairs or inertia from a black hole traveling towards
| you.
| genderwhy wrote:
| It looks like it steals energy from an object in motion, in
| this case a black hole. (Presumably because this is a dense
| object so you can get closer to it.)
|
| Existing satellite slingshot maneuvers steal energy from the
| thing they slingshot around -- every satellite that slingshots
| off earth steals a very, very small amount of energy from the
| earth. The closer you get to the center of Earth's mass, the
| more energy you can steal. It's just that in Earth's case
| there's all this "atmosphere" and "lithosphere" garbage
| preventing you from snuggling up right close to the center.
|
| With a black hole, all that stuff is compressed, so you can get
| closer and steal some of its kinetic energy. (If I understand
| the concept correctly.)
| jjk166 wrote:
| Technically this steals energy from the binary pair, not the
| black hole itself, but yes it's a potential power source for a
| sufficiently advanced civilization.
| what-no-tests wrote:
| "Event Horizon"[0] was a movie in which a spacecraft had a black
| hole used for propulsion. Somehow the spacecraft went to Hell and
| came back infested with demons.
|
| [0] https://www.imdb.com/title/tt0119081/
| gigatexal wrote:
| I love these crazy papers. I don't always understand everything
| but I love reading them.
| DennisP wrote:
| > terminal velocity of approximately 133% the velocity of the
| black hole
|
| So, do we know of binary systems with a black hole moving at
| relativistic velocity?
| cletus wrote:
| A lot of thought has gone into far-future uses of black holes:
|
| - Black hole starships [1]
|
| - Weaponizing black holes [2]
|
| - Colonizing black holes [3][4]
|
| - Black hole computers [5]
|
| Black holes may be the most efficient forms of batteries and
| power generators yet conceived. If our model of the Universe is
| mostly correct then the Univese will have an era of stars that
| will ultimately burn through all the fuel and we'll just be left
| in the dark with black holes that will evaporate over an
| extraordinarily long period of time, many orders of magnitude
| than the stellar era.
|
| For propulsion, this ultimately comes down to photons have
| momentum. We can use them to move things. This is the idea behind
| the solar sail.
|
| Black hole propulsion revolves around how you use the momentum
| from an evaporating black hole into motion for a ship. There are
| a bunch of factors to balance out here. Too small and the black
| holes dies too quick (and is too energetic). Too large and it's
| too hard to move and has a lower output and so on. Turns out
| there's a sweet spot for all this of about a million tons, which
| is in the realm of what we call Kugelblitz black holes.
|
| I personally think using stellar output to accelerate and
| decelerate ships it he most likely outcome for a spacefaring
| species. If fusion ever becomes viable this may be an alternative
| for when you're not near a star. Ultimately black holes may
| replace that but there are significant theoretical and
| engineering challenges to that like how you'd even make a small
| (a million tons of small) black hole and how you'd feed it more
| mass (since it would be the size of an atom). If we could ever
| find a material to reflect and lase gamma ray (a "graser") then
| it might be possible but that's far from certain.
|
| [1]: https://www.youtube.com/watch?v=oAocMzxPjjo
|
| [2]:
| https://www.youtube.com/watch?v=zTMxO1nJaA4&list=PLIIOUpOge0...
|
| [3]:
| https://www.youtube.com/watch?v=pxa0IrZCNzg&list=PLIIOUpOge0...
|
| [4]:
| https://www.youtube.com/watch?v=Qam5BkXIEhQ&list=PLIIOUpOge0...
|
| [5]: https://cse.buffalo.edu/~rapaport/111F04/lloyd-ng-
| sciam-04.p...
| ben_w wrote:
| > Turns out there's a sweet spot for all this of about a
| million tons, which is in the realm of what we call Kugelblitz
| black holes.
|
| "Sweet spot" deserves scare quotes, unless if you have a mirror
| made out of something that doesn't contain up or down quarks or
| any known charged leptons.
|
| That mass black hole has Hawking radiation with a temperature
| of 223 trillion Kelvin, which means most of the photons of
| light in the Hawking radiation have enough energy to not just
| cause spontaneous positron-electron pair production, but also
| proton-antiproton pair production on the surface of whatever
| you're trying to use as a mirror.
|
| To get down to Hawking radiation photons that "only" photo-
| ionise normal matter (about 6eV), you need a black body to be
| "only" about 70,000 K. That in turn means the black hole is now
| about 1766 trillion tons, and has a power output of 114
| microwatts.
|
| https://kitsunesoftware.wordpress.com/2022/05/14/no-a-black-...
|
| Also: minor point, but "Kugelblitz" is how a black hole gets
| made, not the size of the hole:
| https://en.wikipedia.org/wiki/Kugelblitz_(astrophysics)
| mabbo wrote:
| > 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.
| TrevorJ wrote:
| 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 wrote:
| 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.2012.08.0...
|
| Indeed, the author had already done a bench-top
| demonstration: https://ykbcorp.com/photonic-laser-thruster/
| naasking wrote:
| > 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.
| lallysingh wrote:
| But probably a great add-in to a sci-fi story.
| crdrost wrote:
| 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.
| BenoitP wrote:
| When there's only one author, you know it's going to be fun!
|
| (Not disparaging the science, which is surely sound)
| digdugdirk wrote:
| Do you have any other examples of great (in whatever definition
| of "great" you choose to use) single author papers?
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(page generated 2023-01-13 23:01 UTC)