Laser Generated Blackhole Drive

[KJ_Lesnick]

http://nextbigfuture.com/2015/10/laser-produced-blackhole-interstellar.html

While I think interstellar travel is pretty awesome: Doesn't generating a black-hole as a power-source strike you guys as being just a tad insane?

 

[XP67_Moonbat]

Ask the Romulans.

 

[sferrin]

http://nextbigfuture.com/2015/10/laser-produced-blackhole-interstellar.html

While I think interstellar travel is pretty awesome: Doesn't generating a black-hole as a power-source strike you guys as being just a tad insane?

Sounds a bit Rube Goldberg. "Were gonna use lithium batteries to power a laser which is going to heat this water to turn a turbine to generate electricity to charge the batteries. . ."

 

[jeffb]

http://nextbigfuture.com/2015/10/laser-produced-blackhole-interstellar.html

While I think interstellar travel is pretty awesome: Doesn't generating a black-hole as a power-source strike you guys as being just a tad insane?

Sounds a bit Rube Goldberg. "Were gonna use lithium batteries to power a laser which is going to heat this water to turn a turbine to generate electricity to charge the batteries. . ."

Ha. ;D

It's actually a really cool idea, assuming Hawking is right about black holes evaporating of course.

 

[Orionblamblam]

Sounds a bit Rube Goldberg. "Were gonna use lithium batteries to power a laser which is going to heat this water to turn a turbine to generate electricity to charge the batteries. . ."

Not really. You dump mass - any mass - into the black hole; it re-radiates the mass in the form of Hawking radiation, i.e. photons. It's one of the few conceivable ways to convert mass into energy at 100% efficiency. Assuming the radiation comes out in the form of photons rather than something wretched like neutrinos, it's a dandy way to make a photon drive using dull matter as the fuel.

Not to say there aren't a passel of troubles with this. First being the generation of a black hole with gamma ray lasers: focusing that much laser power into a volume the size of an atom, or smaller? Yeah. Let me know how that goes.

 

[Moose]

http://nextbigfuture.com/2015/10/laser-produced-blackhole-interstellar.html

While I think interstellar travel is pretty awesome: Doesn't generating a black-hole as a power-source strike you guys as being just a tad insane?

All black holes are not created equal, the type of pinpoint artificial hole envisioned wouldn't accidentally consume the Earth or anything.

 

[jeffb]

Sounds a bit Rube Goldberg. "Were gonna use lithium batteries to power a laser which is going to heat this water to turn a turbine to generate electricity to charge the batteries. . ."

Not really. You dump mass - any mass - into the black hole; it re-radiates the mass in the form of Hawking radiation, i.e. photons. It's one of the few conceivable ways to convert mass into energy at 100% efficiency. Assuming the radiation comes out in the form of photons rather than something wretched like neutrinos, it's a dandy way to make a photon drive using dull matter as the fuel.

Not to say there aren't a passel of troubles with this. First being the generation of a black hole with gamma ray lasers: focusing that much laser power into a volume the size of an atom, or smaller? Yeah. Let me know how that goes.

The original paper I read talked about powering whole civilizations with these things. You use the first one to power a factory which builds a series of them and, as you say, you just dump matter into them to get back photons and usable energy. Turning them into spaceship drives means essentially putting one in a box with an opening on one side, though to my thinking that'll be one hell of a box. Google should turn up the relevant articles.

As you say though, building that first one may be a bit tricky.

[quote author=Wikipedia]
According to the authors, a black hole to be used in space travel needs to meet five criteria:

has a long enough lifespan to be useful,
is powerful enough to accelerate itself up to a reasonable fraction of the speed of light in a reasonable amount of time,
is small enough that we can access the energy to make it,
is large enough that we can focus the energy to make it,
has mass comparable to a starship.

Black holes seem to have a sweet spot in terms of size, power and lifespan which is almost ideal. A black hole weighing 606,000 metric tons (this is about the mass of the Seawise Giant, the longest sea-going ship ever built) would have a Schwarzschild radius of 0.9 attometers (0.9 × 10–18 m, or 9 × 10–19 m), a power output of 160 petawatts (160 × 1015 W, or 1.6 × 1017 W), and a 3.5-year lifespan. With such a power output, the black hole could accelerate to 10% the speed of light in 20 days, assuming 100% conversion of energy into kinetic energy. Assuming only 10% conversion into kinetic energy would only take 10 times longer to accelerate to 10%c (10% of the speed of light).
[/quote]

http://arxiv.org/abs/0908.1803v1

 

[sferrin]

Sounds a bit Rube Goldberg. "Were gonna use lithium batteries to power a laser which is going to heat this water to turn a turbine to generate electricity to charge the batteries. . ."

Not really. You dump mass - any mass - into the black hole; it re-radiates the mass in the form of Hawking radiation, i.e. photons. It's one of the few conceivable ways to convert mass into energy at 100% efficiency. Assuming the radiation comes out in the form of photons rather than something wretched like neutrinos, it's a dandy way to make a photon drive using dull matter as the fuel.

Not to say there aren't a passel of troubles with this. First being the generation of a black hole with gamma ray lasers: focusing that much laser power into a volume the size of an atom, or smaller? Yeah. Let me know how that goes.

Except they said they'd need to dump MORE laser power into creating the black hole than the black hole would ever produce. Why not just use the beam itself as a "rocket"?

"It would radiate 160 petawatts. It would evaporate in 3.5 years.
The lasers that create must be more powerful."

"Additionally shown is that 45% of the Hawking power and 55-58% of the Hawking flux are emitted on inaccessible channels."

Neutrinos and gamma rays?

 

[Mat Parry]

http://www.darpa.mil/Our_Work/MTO/Programs/Ultrabeam.aspx

Sadly the link no longer works, a cursory search also failed to find any mention of Ultrabeam... (perhaps it was a bust)

ULTRABEAM
The goal of the Ultrabeam program is to demonstrate, with laboratory-scale equipment, the world’s first gamma ray laser.

The demonstration of a laboratory-scale X-ray laser with record-high photon energy of 4.5 keV in the first phase of the Ultrabeam program opens the possibility of creating gamma ray lasers.

Compact gamma ray lasers can enable new and more effective radiation therapy and radiation diagnostic tools for medical and materials/device inspection applications (e.g., TRUSTed ICs).

The unique X-ray laser technology developed in UltraBeam could enable the development of compact, laboratory-scale, high-brightness coherent sources and ultimately enable 3-D molecular-scale imaging of living cells.

The Ultrabeam program has two phases. The first phase demonstrated saturated X-ray gain at 4.5 keV with an estimated 10 mJ, about 30 attosecond as pulsed output and obtained evidence for the transmission of these X-ray pulses through normally opaque low-Z solid targets, an anomalous propagation behavior consistent with the formation of dielectric plasma-waveguide channels in the solid targets.

The second (current) phase of the Ultrabeam program is a 36-month effort that is structured to develop a higher-power X-ray pump laser, gamma ray diagnostics, and gain modeling; develop necessary pump power compression and gain-length techniques and demonstrate coherent gamma ray amplification in high-atomic number solid materials.

 

[Orionblamblam]

Except they said they'd need to dump MORE laser power into creating the black hole than the black hole would ever produce.

Two things:
1)If true, so what? Antimatter is another starship fuel... and any conceivable manufacturing process is going to be vastly inefficient. But antimatter, like the black hole, makes a dandy energy *storage* system. Leave all the truly massive power generation systems at home, and fly away on, essentially, battery power.
2) But it's not (theoretically) true. If you used gamma ray lasers to create the black hole and simply let the black hole evaporate away and gathered up the Hawking radiation to use as power... yes, due to inefficiencies it'd produce less than it cost. But as the hole evaporates, you can refill it by simply dumping *stuff* into it. You could theoretically keep a black hole at a static mass, radiating a constant stream of power, for a trillion years if you simply kept a constant stream of matter flowing into it.

For a black hole meant to power a civilization, you could feed it by simply pouring trash into it and recovering the kinetic energy transferred into the "garbage bucket." But the tiny black holes being discussed here would need to be fed with something like a precisely aimed relativistic proton beam. The hole itself is about the size of an atom, and it would have a hard time swallowing anything bigger than itself faster than it would radiate away. In fact at these small sizes and vast powers, the radiation pressure would be liable to push matter *away* stronger than the gravity attracts. You'd have to force-feed the hole.

 

[sferrin]

Except they said they'd need to dump MORE laser power into creating the black hole than the black hole would ever produce.

Two things:
1)If true, so what? Antimatter is another starship fuel... and any conceivable manufacturing process is going to be vastly inefficient. But antimatter, like the black hole, makes a dandy energy *storage* system. Leave all the truly massive power generation systems at home, and fly away on, essentially, battery power.
2) But it's not (theoretically) true. If you used gamma ray lasers to create the black hole and simply let the black hole evaporate away and gathered up the Hawking radiation to use as power... yes, due to inefficiencies it'd produce less than it cost. But as the hole evaporates, you can refill it by simply dumping *stuff* into it. You could theoretically keep a black hole at a static mass, radiating a constant stream of power, for a trillion years if you simply kept a constant stream of matter flowing into it.

For a black hole meant to power a civilization, you could feed it by simply pouring trash into it and recovering the kinetic energy transferred into the "garbage bucket." But the tiny black holes being discussed here would need to be fed with something like a precisely aimed relativistic proton beam. The hole itself is about the size of an atom, and it would have a hard time swallowing anything bigger than itself faster than it would radiate away. In fact at these small sizes and vast powers, the radiation pressure would be liable to push matter *away* stronger than the gravity attracts. You'd have to force-feed the hole.

Okay that makes sense.

 

[KJ_Lesnick]

Just make sure they test it in outer space...