How close could a spaceship carrying astronauts get to a "black hole" the size of Earth?
Answer from: Ilya Zakharov:
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The last stable orbit for a Schwarzschild black hole is at a distance of three radii from the center of the hole. You can hover on it without turning on the engine. Well, if an engine of unlimited power is available, you can literally get right up close to the black hole horizon.
Answer from: Inezilla:
> There's no time for the ship to turn sideways. Warp drive does not work. At what closest distance can the brave crew safely guide their ship?
If the black hole is rotating, the ship can safely enter a static orbit of motion toward the rotation of the BH closer to the equator of the ergosphere.
Next, using the Penrose process, the ship jettisons the broken engine, other debris, and anything unnecessary. Half of this inert mass remains on the ship in the form of additional kinetic energy and the brave crew leaves the orbit of the BH.
Schwarzschild holes are believed to be extremely rare, t.к. most stars have a rotational momentum.
Since the size of a black hole's ergosphere depends only on the rotational velocity, the size of the hole is irrelevant.
Answer from: Olga Levina:
Philosophy student. I respect the Renaissance, Tolstoy, and quantum mechanics....
I think the most important factor here would be speed. That is, if you fly past the hole at near-light speed, you can tangentially approach the event horizon. And if you stop in motion near the black hole, it will probably start to rotate the ship around its axis.
Secondly it will be important what exactly is near a black hole, if it actively absorbs matter at this moment, probably its vicinity is very dangerous.