# Space-based black hole weapon effects

For the fluff of my story one of the space-ships is equipped with what I hope is one of the biggest F-you weapons in ship-to-ship combat: a miniature black hole launcher.

The launcher fires a whopping 329 metric tons heavy black hole, which is tiny compared to any other black hole. Hawking radiation causes this black hole to evaporate in a mere 3 seconds, causing a violent burst of radiation in that time. To maximize the effect an unobtanium machine prevents the black hole from evaporating until it reaches the enemy ship.

The question is: what would happen when it activates and moves through the enemy vessle?

My idea was as follows: it activates close to the target and starts releasing its energy. In space this explosion of 3.28×10^15 MW does relatively little as it has plenty of directions to go. Then the black hole enters the outer layer of the enemy ship. The black hole event horizon is smaller than the molecules around it and expells so much energy that nothing is absorbed, but it does force everything apart as the equivalent of a nuclear bomb explosion eminates from inside the hull material. Then the black hole starts passing through bulkheads and passage ways inside the ship, tearing holes and burning the air, men and materials to cinders as it does. A well aimed shot is virtually unstoppable and unless your ship is able to handle an atomic bomb detonating inside the hull it is scrap metal.

Is that a correct assumption?

• Even if surrounded by unobtanium, you will have to grab & hold 329 tons of subatomic-sized mass and move around i.e. hold on to it well enough so that if the transporting ship takes off, the mass doesn't just stay in place / fall out the rear. That's a FedEx nightmare. How do you propose to do that? – David Tonhofer May 6 '20 at 23:10
• What if the enemy also has an unobtanium machine? – Schwern May 7 '20 at 4:22
• @Schwern we could build a railgun that fires shells with a timer. Can we use the same technology as easily to stop that shell? – Demigan May 7 '20 at 6:08
• @DavidTonhofer a big ship. – Demigan May 7 '20 at 6:09
• @Demigan Mainly long? It would like having a CERN LHC, but instead of having lead ions in the tube, you carry 328 ton ions. And you have to make them stand still relative to the tube. – David Tonhofer May 7 '20 at 6:12

## Your description is accurate, but not very efficient.

Your black hole is so heavy and small that it will just pass right through any target without really slowing down; so, the real question is how much time does the black hole spend inside of a ship vs how much time it takes to evaporate.

Because space is vast and empty, kiting strategies inevitably make space fights prefer those who can move faster and shoot farther over who can do the most damage per hit. So, if your black hole weapon is to compete with easier to make relativistic weapons like lasers or particle cannons, it needs to itself be able to move at relativistic speeds, or else you will never get close enough to use it.

Let's say for the sake of argument, it moves at 0.5C (~150,000,000 m/s). If it takes 3 seconds to evaporate, then that means it will release its energy over the course of 450,000,000 meters. If you hit the enemy ship along a cross section that is only 45m thick, then you've wasted over 99.99999% of your weapon's power on over penetration (not to mention the ridiculous amount of power it takes to accelerate 329 metric tons to 0.5C). While this would still turn the entire target ship into an exploding ball of plasma, it will only bombard the target ship with an energy output of 236 kilotons out of its total 7,073,500,000 kilotons of total output making it grossly inefficient.

To fix this, you should actually fire much smaller black holes. Smaller black holes release hawking radiation much faster; so it would release more energy per meter of penetration while also taking much less power to make and launch. Because of this, your weapon would make a lot more sense firing shells that are much smaller range but compressed so small that they pass right through shields and armor where they can then radiate so quickly as to release all of thier mass before passing through the target.

For example: a 1 metric ton black hole dissolves in 8.41072E-8 seconds. At that time scale, it would dissipate over a distance of only 15 meters while releasing an entire 21,500,000 kiloton blast inside of the enemy ship. While antimatter weapons could release similar amounts of energy, by condensing your weapon into a black hole, it would be virtually impossible to detect, intercept, deflect, etc.

An even more practical example may be to use an ultra tiny black hole. Even something as small as a 0.6 gram black hole will explode with the force of the hiroshima atomic bomb once you take away the artificial anti-hawking radiation field. While not as spectacular as a multi-gigaton weapon, at 16 orders of magnitude smaller than an electron it could simply pass right through anything you want it to allowing you to detonate it directly inside of a target ship's reactor. If an internal explosion capable of devastating a small city can't destroy the ship you are shooting at, the critical explosion of its reactor should finish the job.

If you really want to make it a super weapon, make it able to modulate its shots such that it can do anything from about 329 metric tons to 1 gram. A 329 metric ton exploding black hole weapon is about 30 times less powerful than the Chicxulub impactor event, but still more than enough to end an entire civilization with a single shot, or you could scale it way back for one shotting ships, cities, and space stations.

• Although it doesnt exactly answer the question itself it does offer a more reasonable method of using it, thanks! – Demigan May 6 '20 at 17:35
• @Demigan Short answer is that as long as you are working with black holes that are nowhere near as massive as natural black holes, your effect will look similar to a nuclear explosion happening inside of the enemy ship. There are a lot of factors that can play into how big of a nuke equivalency you are dealing with and how efficiently you are doing it, but in at the end of the day, you are looking at reducing the target ship to a cloud of plasma. Updated may answer with some additional practical examples. – Nosajimiki May 6 '20 at 19:19
• Actually, let me revise that. There is a large range of sizes much bigger than 329 metric tons but smaller than a real black hole that will not do much at all as it passes through a ship at relativistic speeds and a large range that is bigger than that which will not hit you with significant radiation but will do significant gravitational shearing damage without being nearly black hole size, but the most bang for your buck will generally be black holes that are no more than a few thousand kg. – Nosajimiki May 6 '20 at 19:39
• The radius of the black hole would be about 1/2 the diameter of a proton. See Schwarzschild radius for the formula. – Bohemian May 7 '20 at 2:26
• In fact, consider a missile containing the tiny black hole and the "the artificial anti-hawking radiation field" generator accelerated to some ungodly speed. When it's time to detonate close to the target, shut off the field and the black hole evaporates, releasing all that energy. If the enemy happens to hit your missile with something, the field generator is destroyed and the missile detonates. They better not let it get too close... – Kryten May 7 '20 at 16:15

You’ve drastically under-estimated the force of the explosion. All of those 329 tons of mass will be converted to energy during the 3 seconds of evaporation. That’s 3E22J of energy. A 1 megaton nuclear explosion is about 4E15J of energy. So your black hole explosion is equivalent to 7.5 million megatons of nuclear weapons. For comparison, the biggest nuclear weapon ever made, the Tsar Bomba, was 50 megatons. So you’ve got the same size explosion as 150 thousand of those.

• So it's a guaranteed killer, and you need to launch from a respectable standoff distance. Looks like the only thing to consider is the cost-benefit ratio. If it's cheaper to launch, e.g. a hundred KEWs , guided, moving at a measurable fraction of c, then choose the latter. – Carl Witthoft May 6 '20 at 13:23
• I used this calculator: vttoth.com/CMS/physics-notes/311-hawking-radiation-calculator. I was under the impression that the 3,28×10^15MW was on a per second released basis (watt= 1 joule per second right?). So it would be 3,28×10^21 joule/s released for a total of 9,84×10^21 joule. Now I'm totally for making this weapon even more ridiculous as that is the point but could you provide your calculation? – Demigan May 6 '20 at 13:53
• @Demigan Your methodology is a bit flawed, since the energy radiated goes up pretty significantly as the black hole loses mass, so it won't be $3.28\times 10^{15} MW$ during the entire period of evaporation. Still, doing the $mc^2$ calculation this answer suggests leads only to $~3\times 10^{22} J$ of energy being released, so it's off by a factor of 1000. My guess is that the author accidentally used $g$ instead of $kg$ in the formula. Even so, $~3\times 10^{22} J$ is a tremendous amount of energy and this weapon would very rapidly obliterate any realistic structure. – el duderino May 6 '20 at 14:37
• @elduderino You’re right about my error, and I have edited my answer. – Mike Scott May 6 '20 at 16:23
• @Demigan As elduderino says, 3.28E15MW is the power generated at the 329 ton point — it doesn’t stay at that level. As the mass reduces, the power increases very quickly. If it stayed at 3.28E15 MW, it would take much longer then three seconds to evaporate. – Mike Scott May 6 '20 at 16:26

One problem in your description would be any technology capable of containing a black hole until you need it to explode, could just as well be used to defend against said black hole weapon. (for instance "catch" the black hole and only let it dissipate away from your ship)

Alternatively you could have, whats essentially a missile, that creates a black hole upon impact (similar to how a nuke doesn't contain a nuclear blast, but triggers one using the materials it has). in this case you could even use parts of the enemy ship as the mass being compressed, instead of having to haul 329 tons of matter around (that's a lot of matter to accelerate to intercept a spaceship) It's also a lot safer, than having potentially hundreds of black hole ammunition somewhere in your ship :)

Second problem you need to take into consideration is space is biiig, that's why it's called space, there's so much of it... (just kidding, that's not why it's called space)

Your black hole is an unguided round, so you would need to be extremely close before firing it, or simply making it unlikely that you would ever hit your target.

So TLDR would probably be, yeah it would hurt to get hit, but your probably not going to get hit, so you don't really need to worry about your enemy shooting it at you. (Those missiles with a gigaton payload comming at you on the other hand, those are scary)

• It's not unguided - he said it was inside a (presumably guided) container and only released when in close proximity to the target – Carl Witthoft May 6 '20 at 13:21
• Well any technology that can accelerate a bullet can also stop it right? The problem is that you need something specific and the bullet (BH in this case) needs to be at a specific spot to be launched and work correctly. But that is all besides the point. The point isnt "could it dodge the shot", "could it stop the BH" or "I activate my improbability drive and cause them to implode while I reach my improbable destination", the point is "what would happen if this weapon reaches your ship and causes havoc". – Demigan May 6 '20 at 13:59
• Throughout history, the technologies used to make a weapon work and those that stop them are almost always fundamentally different. Usually someone comes up with a weapon, then a few decades/centuries later, someone finds a way to stop it. – Nosajimiki May 6 '20 at 19:44
• Because of conservation of energy, for the missile to create a black hole which evaporates with energy X it needs to carry that energy with it. If the missile can get to the ship with all that energy there's less exotic ways to turn it into destruction. – Schwern May 7 '20 at 4:33
• @Demigan - "Any technology that can accelerate a bullet can also stop it" is fundamentally untrue. You can't stop a bullet with a gun unless you have truly impossible aim. The weapon vs. defense imbalance is generally more akin to unscrambling an egg. – jdunlop May 7 '20 at 17:20

tl;dr: The idea of a sub-atomic black hole as a warhead is great, but how are you going to hit anything? If you have 1e23 Joules to play with, a directed energy weapon or railgun is much more effective and requires no unobtanium machine.

That black hole doesn't come for free, nor does firing it at any appreciable speed. As much energy had to go into creating it as it is capable of releasing. Probably A LOT more. The question becomes...

and

# Why aren't you doing them? In space.

As with every weapon system we must ask whether it's a significant improvement over the alternatives? This is difficult to answer without knowing the state of offense and defense, and the presence of one unobtanium machine throws all physical limits into question, but there's still one problem.

# Hitting Things (in space)

It's really, really, really hard to hit things in space, especially if they don't want to be hit. Sci-fi depicts spaceships lobbing broadsides into each other at point blank range. In reality, everything in space is so far apart, and traveling so fast, that your ability to track and predict the movement of your target becomes paramount.

Speed of your projectile is also paramount. Just like on the ground, the faster your projectile is going, the less time it has in flight, the easier it is to aim, and the less chance the enemy will maneuver away. At a certain point increasing your range is pointless; the flight time is so long that the enemy can simply turn in any direction to avoid your shot. For battleships this was about 30 seconds. Any more distant and the enemy captain simply had to turn when they saw the flash of your guns.

But space has a speed limit, the speed of light. This introduces two very interesting problems. First, there is a maximum effective range in space for unguided weapons, and it's A LOT shorter than you might think. Let's say your ships have a roughly 100m cross-section. The target only has to maneuver 100m in an unexpected direction for an unguided payload to miss.

At the energy levels you're playing with a ship's delta-v is limited only by how much stress it can put on its structure and its crew. Let's say it's 9g's, the limit of human endurance.

How long does it take for a ship able to accelerate at 9g's to move 100 meters? 1 g is roughly $$10\frac{m}{s^2}$$. 9g is roughly $$90\frac{m}{s^2}$$. So a bit over a second.

In one second, a ship can maneuver out of the way of an unguided projectile. This means even an energy beam has an effective range against a maneuvering target of 1 light-second or about 300,000 km.

The second problem is, unlike a battleship, light delay means you're seeing where they were 1 second ago further complicating the aiming process. OTOH if the enemy sees "the flash of your guns" they've been hit. However, the target only need to make random zig-zags during combat to remain effectively immune to unguided weapons beyond 1 light-second.

# Directed Energy (Space) Weapons

If a sub-atomic black hole can penetrate their defenses, then a focused, high-energy photon beam can as well. It's even smaller, and it also has no electric charge. It travels at the speed of light making aiming as easy as it's going to get. What's not to like?

Range. As the range increases, the focus will decrease. This puts a limit on the effective range of an energy weapon; eventually it's so defocused that it's no longer effective. But effective unguided range is already limited to 1 light-second, so this isn't a big problem. And that defocusing might be a good thing, the weapon can hit a wider area.

# A Well-Aimed Space Rock

If you're going to fire this black hole at a ship unguided it has to be going as fast as possible. Let's say 0.9c. Accelerating 329 tons of matter to 0.9c costs, at minimum, 4e22J. As much energy as the black hole itself. Why bother with the black hole, just fire a 329 ton rock. Sure, it's not sub-atomic, but if their ships can withstand 4e22 Joules smacking into them we're at a whole other level.

# The Black Hole Space Torpedo Must Be Guided Through Space

To offer an advantage over a directed energy weapon, or a rock, the black hole must be able to deliver its energy over a longer range. In order to have a chance of hitting the target it must be guided, and it must be more maneuverable than the target; a black hole torpedo. This means engines, sensors, not to mention a trigger mechanism and the unobtanium machine to keep it stable, etc... size and weight.

You're no longer firing a sub-atomic black hole at the target, you're firing a small space ship. A small space ship which can itself be targeted and shot down by the enemy's own simpler and cheaper directed energy weapons and railguns. And that is its Achillies heel. Missiles and torpedoes don't make sense in space when you have directed energy weapons and railguns, they're too vulnerable.

You can't hit the ship.

• This sounds very believable to me! Can you recommend any sci-fi with space battles like what you describe? Like random zig-zags make so much sense but I've never seen it done. – Daniel Darabos May 7 '20 at 9:49
• @DanielDarabos re: "random zig-zags". It's not a movie, but this technique is discussed in The Forever War by Joe Haldeman. – Kryten May 7 '20 at 16:21

# Unobtainium Unnecessary

If you want to prevent a black hole from evaporating, you just need to feed it. As long as the energy in == energy out, it will remain at any fixed size you desire, for as long as you can maintain those conditions. The real problem with micro-BHs is that their mouths are much smaller than the mass you want to feed them. They are just as happy with a diet of photons as with baryonic matter, but photons carry much less energy density with them. So while they are easier to focus down to a tiny point, you need to pump in a lot more to keep the BH from exploding.

# Launch Velocity

Others have suggested that the "black hole bullet" (BHB) be launched at relativistic speeds so as to deter countermeasures. Obviously, the faster you can launch it, the better. Launching 300 tons to relativistic speed implies an energy source so large you might be able to dispense with the BHBs and just point your power plant in the general direction of the enemy. Anyway, I propose a "smart bullet" with the following design:

Instead of letting the BHB radiate away its valuable mass on the way to its target, you encase it in a shell of ordinary matter which is reflective in the most common frequencies emitted by the BHB. Unfortunately, this probably includes X-rays, for which we do not have efficient reflectors. Also, this shell will inevitably radiate a blackbody spectrum, which gives away its position all the way to the target. Even so, ordinary matter can act as an X-ray scintillator, absorbing the X-rays and re-radiating them in lower, more reflective frequencies (UV, visible, etc.). Thus, you should be able to feed a respectable fraction of the radiation back into the BHB to sustain it. Since this "reflection" is obviously quite lossy, you will need to augment it with additional mass. We can use the innermost layer of the shell as an ablative layer which we sacrifice to stabilize the BHB on its journey. The X-rays bombarding the inner layer will embrittle it, causing chunks to come off naturally, but this process can be more finely controlled with some clever nanotechnology and geometric design of the inner surface.

Finally, we can give the BHB active steering, rather than a ballistic trajectory by creating a hole in the protective shell and using on-board gyros to rotate the hole to any position desired. This will essentially let us use the BHB as a kind of radiation jet to steer the "bullet".

# Countermeasures

How do you defend against such a weapon? If you can destroy the shell long before it reaches your ship, then it will evaporate outside of the lethal range (although it may still deliver a quite unpleasant shock of hard ionizing radiation). This could be accomplished either using directed energy weapons or kinetic projectiles. If the BHB has steering capability, it can defeat some to most kinetic PD weapons, at least until it gets within lethal range. Beam weapons are obviously more difficult to counter, but are also more difficult to use. Creating a high-powered beam which can feasibly burn through a thick metal shell will not have a small collimation radius. Focusing it down to something maybe tens of cm across will be quite difficult. It may be possible to keep the beam on the BHB for the entire trajectory, but the BHB may have such a small cross section that it only absorbs a small fraction of the beam energy, reflecting the rest away or even absorbing it and re-radiating it in a directed fashion to use as guidance propulsion. Basically, big lasers are good for burning big holes in big targets, but not so good for burning tiny holes in anything.

So, I reject the assumption that technology needed to create such a weapon implies the ability to defeat it. In general, offense will always be ahead of defense, because it is always possible to add enough energy to a target to disintegrate it (exceed the binding energy of the target), while the ability to dissipate energy fast enough to preserve integrity scales too poorly to keep up at all power densities.

Fun fact: a very small black hole is radiating energy so quickly it starts emitting electrons and positrons, making a micro-black hole a nice antimatter source, which is going to do all kinds of fun things to your target (and, unfortunately, your "bullet shell"). Furthermore, these are ultrarelativistic, which might mean it is infeasible to contain them without pretty massive shielding. Someone else will have to do the calculations on that.

• "you just need to feed it": Well, that's pretty tough to do when the thing you are trying to feed is smaller than a proton, and hotter than pretty much everything known in universe. The biggest nuke exploding is an arctic frost in winter compared to an evaporating black hole. Anything you try to feed the BH with will be blasted away long before it can reach to the BH. – cmaster - reinstate monica May 7 '20 at 6:46
• Depends on the size. Yes, a BH small enough to be an effective bomb becomes increasingly difficult to feed, but it's not exactly going to bounce EM radiation back at you, so you can always shoot it with a laser. – Lawnmower Man May 7 '20 at 20:07
• A laser of $10^{15}MW$?!? A laser focused to a single proton?!? A proton is less than a femtometer ($10^-{15}m$) in diameter, you'd need a laser with a wavelength in the same vicinity to be able to focus it that small. Visible light has about 500 nanometers. That's a factor of 500 millions too big, you are talking about a gamma ray laser here! The european XFEL (en.wikipedia.org/wiki/European_XFEL), one of the most bad-ass X-ray sources in the world, can "only" reach down to 50 picometers ($10^-12$). No, you can't feed a 3-second BH. Just no. – cmaster - reinstate monica May 7 '20 at 21:15
• You don't need to focus all the energy onto the BH precisely. You just need to cover it. Obviously, the worse your focus is, the more energy is wasted (unless you have really good optics and can reflect most of it back onto your target). – Lawnmower Man May 7 '20 at 22:59
• Please, reread the figure about the required power. If, after doing that, you still believe that it's possible to feed a 3s BH, I can't help you. By the time you have such a laser, you'll simply forget about black holes, and simply direct your laser at your enemy. – cmaster - reinstate monica May 8 '20 at 6:02

The question is: what would happen when it activates and moves through the enemy vessle?

What would happen is that the enemy will steal the tech (or, seeing that it's feasible, develop it on their own), and then counter-attack their enemy's home world. The admiral who used this for ship-to-ship combat will be forever ridiculed in the military history of the original civilization -- not that it will matter, because that civilization won't exist much longer.

This technology is for attacking planets, not starships.

The mechanism might be realistic (I defer to the other answers that have done the math, and weigh in on aiming, range, etc.), but a civilization using this as a ship-to-ship weapon is not. (No matter how much the admirals want to say "F-you" to their enemy admirals.) A civilization with this tech would attack the enemy's home world and colonies.

With the kind of energy you are talking about, you could do a lot more damage attacking a planet, and timing it so that the black hole Hawking-evaporates as it passes through the interior of the planet. I would not expect this to flat-out blow the planet apart, but it will cause dramatic, planet-wide seismic disruptions (to put it mildly).

Or, you time it so the explosion takes place mainly at or near the core of the planet. Again, the planet itself won't blow apart, but this will have dramatic, destructive, planet-scale effects.

Or, you set off the explosion near the surface, (a) causing massive damage in that entire region, and (b) creating a plume of ejecta that will adversely affect the global climate for decades or centuries, or even (c) induce a small but significant (to weather, climate, and everything that depends on them -- in other words, everything) wobble.

Or, you set the explosion off inside the planet's moon, if it can be partially or entirely destroyed, raining large meteors down on the planet for a long time to come, or near the moon's surface, using the ejecta stream to destabilize that moon's orbit -- crashing it into the home planet, say.

And, before launching these attacks, the enemy civilization might wonder why their enemy who came up with this limited themselves to a very arbitrary-sounding 329 metric tons. If a 150,000x-Tsar-Bomba explosion isn't quite enough for the above uses, they could crank it up to 500 metric tons. Or 1,000. Or --

This is a war, for goodness sakes : Your thinking about how this might work seems okay (given unobtanium, of course), but if you throw this into your story as fluff, and if I were reading it, it would be jarring, because I would be asking "Why bother blowing up ships with that kind of tech?"