HALO DRIVE: Could We Use Black Holes for Space Travel?

[dsmike1980]

https://youtu.be/pC2pB29HHnc

So this happened today. There is a link to the paper he is referencing in the video description.

[Drashner1]

Yeah, I came across this 2 or 3 weeks ago. Meant to post something about it, but got sidetracked. It's clever, but suffers from the rather major problem that (as this video mentions) the nearest known black hole is thousands of light-years away and that even if one was relatively 'nearby' it would still be so far away that if we could reach it in the first place we probably wouldn't need to use this technique, as we would have developed other methods that are as (or more) capable and don't require a black hole to work.

To use an example already found in OA - Beamrider technology would let you accelerate a starship up to a high percentage of the speed of light (potentially even high enough that travel to the Andromeda galaxy in less than a human lifetime becomes possible to contemplate - although we don't take it that far in the setting) at extremely high efficiency using a small fraction of the energy output of nearly any star (so no need to first travel to a specific - and possibly quite distant - location before you can use this tech. Magnetic braking sails would let you slow that same starship down from high fractional c to about one half of one percent of c in less than three years - with no expenditure of reaction mass.

I'm not totally dismissing the idea - points to the author for putting the different pieces together to come up with this. But I don't really see it as having much practical value from a near to intermediate future interstellar travel standpoint (unless maybe we postulate that future starships might employ multiple different modes in the course of their travels - taking advantage of any black holes they come across or know of for a given trip?). The author does talk about a sort of galactic network that uses the black holes (in particular binary black holes (which the video itself doesn't talk about much) to accel and decel ships (potentially of planetary dimensions) - which might work if you have a galactic civ that is sending ships all over the galaxy. But for smaller scales, it is rather iffier. Again, you'd have to get to the black hole(s) before you could use them. And if you have the ability to do that - do you actually need them?

My 2c worth,

Todd

[radtech497]

Yeah, I came across this 2 or 3 weeks ago. Meant to post something about it, but got sidetracked. It's clever, but suffers from the rather major problem that (as this video mentions) the nearest known black hole is thousands of light-years away and that even if one was relatively 'nearby' it would still be so far away that if we could reach it in the first place we probably wouldn't need to use this technique, as we would have developed other methods that are as (or more) capable and don't require a black hole to work.

To use an example already found in OA - Beamrider technology would let you accelerate a starship up to a high percentage of the speed of light (potentially even high enough that travel to the Andromeda galaxy in less than a human lifetime becomes possible to contemplate - although we don't take it that far in the setting) at extremely high efficiency using a small fraction of the energy output of nearly any star (so no need to first travel to a specific - and possibly quite distant - location before you can use this tech. Magnetic braking sails would let you slow that same starship down from high fractional c to about one half of one percent of c in less than three years - with no expenditure of reaction mass.

I'm not totally dismissing the idea - points to the author for putting the different pieces together to come up with this. But I don't really see it as having much practical value from a near to intermediate future interstellar travel standpoint (unless maybe we postulate that future starships might employ multiple different modes in the course of their travels - taking advantage of any black holes they come across or know of for a given trip?). The author does talk about a sort of galactic network that uses the black holes (in particular binary black holes (which the video itself doesn't talk about much) to accel and decel ships (potentially of planetary dimensions) - which might work if you have a galactic civ that is sending ships all over the galaxy. But for smaller scales, it is rather iffier. Again, you'd have to get to the black hole(s) before you could use them. And if you have the ability to do that - do you actually need them?

My 2c worth,

Todd

If it takes too long to get to a natural black hole, you'll just have to whip up a local Kugelblitz.

[AstroChara]

Still need a lot of mass to make it useful though.

[Rynn]

If it takes too long to get to a natural black hole, you'll just have to whip up a local Kugelblitz.

You could indeed, but unfortunately there is no such thing as a free lunch. The energy the laser beam gains from going round the black hole comes from its angular momentum, which came ultimately from the energy used to make the black hole. You could just use that energy to propel space craft directly. But like Todd I’m not dismissing the idea some systems might choose to pump gigantic amounts of energy into a black hole so that future travellers can easily use it for transport.

[Drashner1]

One of the things I need to try and get a better handle on in this paper (unless one of you fine people can beat me to it ) is that it is mentioned that the system can accelerate a ship up to a max of 133% of the BHs velocity. I'm not really clear on what that is supposed to mean.

133% of its velocity through space? Of its rotational velocity? Of the binary holes rotational velocity? Something else? And what does that translate into as a percentage of c or kps?

On a different note - you could probably use this same basic idea to extract energy from the BH(s) and power an orbiting habitat. In fact, that would probably be easier since the hab would be in a predictable orbit instead of moving at high speed on some trajectory and accelerating. You could also position a hab so that issues with the laser encountering the accretion disk or similar things could be minimized or avoided (or at least predicted).

Todd

[iancampbell]

One could probably do something similar with a white dwarf or neutron star, examples of both of which are present much closer than the nearest known black hole. Nearest white dwarf is Sirius B, nearest neutron star is 250-1000 LY away.