tlb wrote:But is that a useful power source AND a useful means to propel a space ship? Cthia said it was a near "infinite" source of power. If we knew how to create and destroy a black hour, I am assuming that 356 MW times 1.5 trillion years is the amount of energy to create this particular billion-tonne black hole. If so, we are well short of the power needed.
No, the energy you need is E=mc² = 9 * 10^28 J. At a constant 356 MW, that takes 8 trillion years. The power that a black hole radiates in Hawking radiation is inversely proportional to the mass squared, so it becomes brighter as it radiates. So after about one trillion years, the black hole will have lost 30% of its mass and will have ramped up to 726 MW.
I will not work it out, but it does not sound as though the gravitational pull will be giving the ship very much acceleration, unless we get much closer than 1 meter.
No, it isn't. Black holes do have attraction, but the problem is how
they move.
First, sorry, I need to correct one thing: the distance to feel the same gravitational attraction needs to be from the centre of a spherically-symmetric the object. Dimorphos is far from perfectly spherical, so its gravitational attraction won't be perfectly spherically symmetric either (nor is Earth's). Its largest dimension appears to be 208 m; so let's model it as a spherical object in a vacuum less than 200 m in radius (q.v.,
https://bigbangtheory.fandom.com/wiki/The_Joke).
That means you can't sit 1 metre from its centre without being inside of it. But you could sit 200 m from it, which would give you a gravitational acceleration of 8.34 mm/s².
You
can get much closer to a BH, which is why they're dangerous. At a tenth the distance, the acceleration would be 100x. It reaches one gravity at 5.83 m, ten gravities at 1.84 m and 34 gravities at 1 m. So the second problem you're going to see with a BH drive is the
gradient.
If you had that stupendous amount of energy, you can create black holes, for example by concentrating with lasers. That's the Kugelblitz I've linked to more than once. You can get more energy than your initial BH because you can feed it matter and let it transform that to energy. This is known physics, if still impractical. Black holes can convert matter to energy at about 10% efficiency, which is better than nuclear fusion and only loses to matter-antimatter annihilation, but without the need to come up with the antimatter in the first place.
But a Kugelblitz is not a drive, it's at best a power source. It doesn't get you anywhere, except closer to the black hole. If the black hole is in orbit of your planet, all you're going to do is accelerate a couple of metres and run over the black hole. You're not going to go to another star, and you're definitely not going FTL.
The trick that SciFi authors use is that they somehow "project" a blackhole of an arbitrary mass ahead of the ship, so the ship falls towards it for a fraction of a second, then the BH dissolves and gets recreated further ahead. That would make the ship keep falling, and thus accelerating. But even if we had a power source of enough capacity to create a black hole of sufficient mass that it could accelerate you without ripping you to shreds due to the gradient (spaghettification), the black hole won't dissolve / evaporate. Since black holes have no hair, once created, the black hole's evaporation will be proportional to the mass cubed.
And again, that's not FTL.
