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Common in sci-fi tropes but absolutely climactic nonetheless, a spaceship faces impending doom after encountering a gravity well such as a stellar black hole. The spaceship's captain gives the order to discard all reactor cores onboard and detonate them to produce a powerful shock wave, the spaceship then escapes the gravity well by leveraging the energy carried by this shock wave.

Is this trick feasible? Wouldn't the spaceship be bathed in deadly high energy particles and radiation? And wouldn't the impulse of the explosion splatter everyone on board because of the spike in G-forces?

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  • $\begingroup$ How deep in the gravity well are they? $\endgroup$
    – L.Dutch
    Dec 4, 2023 at 12:30
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    $\begingroup$ @L.Dutch they are precisely on the "Drama Line", the altitude at which it is possible to blasted to safety by a makeshift bomb cobbled together from bits of your ship that really shouldn't be going bang. Below the drama line, all you'll be able to do is to send out a tearful goodbye message, possibly telling your children how proud you are of them, before you plummet to your doom and/or explode. Above the drama line you can just fly away, and as such no-one is really interested in that flight regime. $\endgroup$ Dec 4, 2023 at 16:12
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    $\begingroup$ @Gillgamesh if there is an accretion disk you aint getting anywhere near the horizon $\endgroup$
    – ErikHall
    Dec 4, 2023 at 23:54
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    $\begingroup$ @cybernard antimatter reactors would actually produce copious amounts of gamma radiation $\endgroup$
    – Seggan
    Dec 5, 2023 at 19:40
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    $\begingroup$ "Shock wave" is not the same thing as "blast." An expanding cloud of matter is a blast. It will push on anything that gets in its way, though for a dense object like a ship, it probably will push past the ship, engulfing it. The ship will only get a small boost. It won't ride the leading edge of the blast the way a surfer rides a wave. Shock waves, on the other hand tend to break things without producing much (if any) motion. No worries out in space though, because a shock wave needs a medium. You can't have a shock wave in vacuum. $\endgroup$ Dec 6, 2023 at 14:17

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I would vote no.

Whether or not you are in the well of a black hole doesn't really matter. The gravitational well of a black hole is almost identical to that of any other celestial body outside the event horizon—leaving aside frame dragging and other such inconveniences.

What you are describing is, in essence, nuclear-pulsed propulsion, which is a very real concept; however, you need to design your spacecraft for this type of propulsion.

Diagram of spaceship

As any illustration of Project Orion will tell you, these ships need a rather heavy mechanism to convert the almost instantaneous blast of the bomblet into a smooth multi-second-long acceleration.

Even so, you can't just use any bomb or explosion. Despite what some may think, Project Orion does not work by using radiation pressure. Instead, the bomblets have a bit of propellant at the top, which the nuclear explosion underneath slams into the pusher plate. That's what's transferring the momentum—the radiation does barely anything. This is why conversations of Orion's per-bomblet yield are difficult, as depending on the design a 1Mt bomblet might generate less "thrust" than a 10kt one.

The big issue with doing redneck Orion is that while all spaceships should have extensive radiation protection, they definitely do not have a spare pusher plate sitting around with an absorption mechanism. Even if your ship could structurally survive being blasted by a huge explosion, your crew can't. This is actually a huge problem for Orion—if the pusher plate for any reason jams or is out of sync the spaceship as a whole, it suddenly absorbs the entire force of the nuke and would probably just break apart.

So, I would say this is infeasible if the spacecraft isn't explicitly designed to be a nuclear-pulsed one. You might be able to do some retrofit Project-Medusa-type deal, but if you have the spare parts for that, I feel like you are not really trapped in the first place.

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    $\begingroup$ Introducing the human meat patty, sourced from NASA astronauts - expiry date: Indefinatly. That radiation keeps them fresh! $\endgroup$
    – Pica
    Dec 5, 2023 at 8:15
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Yes. If you're resourceful.

Nuclear pulse propulsion is the way to go - however it is possible to use the 'Medusa' method instead of intensively using pusher plates and springs.

This is when you eject a nuclear bomb in the direction you want to go. You have a series of wires connecting a parachute behind it, such that when the nuclear bomb goes off it pushes on the parachute and 'pulls' the spacecraft.

enter image description here

The advantages are:

  • All components are in tension, lightweight and uses wires, so you do not need complex pusher plates, coils and springs
  • The parachute can be as far away as needed for longevity, its material is just in tension, can be fabricated from almost any material and its size just has to be angularly larger than the spaceship to create a net force in the direction of the bomb
  • All you need is spare wire, and a parachute (which you might have for some sort of re-entry?) or a series of parachutes would do
  • If you have wires long enough, you could position your spacecraft a long way from the bomb, so it is not affected as much by the radiation when the bomb is detonated.

A video can be found here, although in this example the wires are shown quite short, and they use a ring as a 'spring': AnimationLink

I actually think the Medusa spacecraft concept is safer, smarter and longer wearing than push-plate nuclear pulse propulsion designs.

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    $\begingroup$ On the last sentence, i disagree. A pusher plate, from a design perspective, is incredibly simple. Its a huge chunk of steel with some big boy shock absorbers. A design very hard to screw up and that is by its very nature extremely resistant to damage. Medusa is less efficient that Orion, way bigger and the sail can take significantly less punishment than a plate. $\endgroup$
    – ErikHall
    Dec 4, 2023 at 18:01
  • $\begingroup$ @Fattie I'm open to suggestions to improve the answer, but I don't think your comment is warranted, nor its tone. The point of the answer is that parachutes and wires are possibly readily available - you don't need "10,000,000:1 springy properties (sic)" - the parachute can be positioned as far as you like away from the spacecraft. If you could suggest an alternative method of answering the question, then perhaps it would be best to provide an answer. $\endgroup$
    – flox
    Dec 7, 2023 at 2:01
  • $\begingroup$ @flox - fair enough! the issue is that pulling by wires (even if a zillion miles long) produces exactly the same momentary explosive force/acceleration as using a pusher plate, no difference unfortunately! $\endgroup$
    – Fattie
    Dec 7, 2023 at 13:25
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No.

No matter how tough the egg is, the yolk would still get scrambled. Any explosion strong enough to throw a spaceship into space would kill everyone onboard.

You'd need force fields and inertial dampeners and if you have that tech, you don't need to ride an explosion into space.

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  • $\begingroup$ The correct and simple answer. $\endgroup$
    – Fattie
    Dec 6, 2023 at 22:16
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No... except, maybe

Propulsion is what you get when reaction mass expands in a controlled fashion inside a suitable chamber, thereby pushing your ship along. The keyword here is "mass."

The problem with the SciFi trope from a realism perspective is that there simply isn't enough mass to push the ship along. Most of the mass is lost to interstellar space. What mass remains is a fraction of what would have been used for propulsion had the "core" (or whatever was used to make the explosion) been capable of detonation inside the suitable reaction chamber (like the propulsion bells of the Saturn V F1 engines).

Then there's that maybe

Thanks for the tag! let's stretch a little and rationalize what you're trying to do. It just so happens that your ship is equipped with Solar Sails. Perhaps they're used betimes to supplement your primary engines for greater fuel efficiency or maybe they're there for emergency propulsion.

And getting trapped in the gravity well of a black hole is definitely an emergency!

Deploy those sails, jettison that core, and hold on tight! But only with one hand... things like this should be done with style.

enter image description here
Image courtesy Wikipedia

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To escape a gravity well one needs to supply to the escaping object enough energy to reach infinite distance from the well with velocity 0.

In principle any sufficiently big explosion can satisfy this requirement, as long as the escaping object is not yet past the event horizon of the black hole. Past the event horizon the only escape is to wait to be turned into Hawking radiation.

However any structure has an energy threshold which can withstand, after which it will get damaged or destroyed by the explosion, which I assume is not the intention.

At the end a chemical rocket is nothing more than an explosion, sufficiently spread over time so that the rocket doesn't get damaged and can accomplish its mission.

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I'm going with maybe, but for reasons not previously mentioned.

Let's talk about star drives and their power output, then compare that to the power output of an explosion.

Your ship is capable of travering deep space casually and easily, it's not a generation ship or you wouldn't be exploring event horizons up close, hence it has a superluminal drive system, the power output of which is quite simply magnificent.

In short, an explosion can't match this. Not an Orion drive, probably not even a supernova.

they are precisely on the "Drama Line", the altitude at which it is possible to blasted to safety by a makeshift bomb cobbled together from bits of your ship that really shouldn't be going bang. Below the drama line, all you'll be able to do is to send out a tearful goodbye message, possibly telling your children how proud you are of them, before you plummet to your doom and/or explode. Above the drama line you can just fly away, and as such no-one is really interested in that flight regime. - Starfish Prime in the comments

There are several Drama Lines to define, importantly the explosion Drama Line is considerably further out than the star drive's Drama Line.

The quirk of black holes is that you need to be able to travel faster than the speed of light to escape the event horizon. Your star drive can already do this.

Now you need to tell a story

The important part is that you're still outside, but approaching, the explosion Drama Line, which leaves you well outside your star drive Drama Line. Something has gone wrong with your star drive, technology is now a character in your story, you can begin the technobabble.

You get a choice, and you can build up to it. Either you blow up the drive now and escape on the explosion Drama Line, or you try to hold out and fix the drive and get out ahead of the star drive Drama Line. This inverts the traditional plot where the drive repairs fail and then you blow everything up.

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Only a spaceship with very advanced technology would dare explore black holes. Escape by riding a shockwave was actually the plan all along (how else would you escape!?). The ship is equipped for it: It puts the entire structure in a stasis field which completely shields the ship and its interior from any interaction with its surroundings; all forces of the explosion are acting only on the infinitesimally thin boundary layer.

This stasis field needs ginormous amounts of energy which the normal engines cannot deliver in the few microseconds available (no, not even these very advanced ones). Thankfully, there is plenty of energy available from the explosion. The stasis field projectors are activated and powered by the radiation of the very blast they are protecting against. The stasis field progresses with the wave front through the ship, limiting the crew exposure to a tolerable minimum.

This bootstrapping scheme is known as is "Self-triggering deployment", or STD. The apparatus itself is called "Stasis forwarding unit", or STFU.

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    $\begingroup$ " ' lol ' " :) :) $\endgroup$
    – Fattie
    Dec 6, 2023 at 22:16

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