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I have noticed this in many fictions: during a battle between spaceships exchanging fire in empty space, a pulse of laser fire hits the hull and the entire spaceship explodes into many pieces.

Is this possible? Wouldn't the surface of the spaceship absorb all the energy from the pulse and burn? Could an energy-based projectile pierce through many layers of structure and blow up the engine, in blatant disregard of the Beer-Lambert law? I'd think that even a pressurized compartment wouldn't explode that violently if opened to vacuum by the shot.

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    $\begingroup$ Battle scenes wouldn't be quite so exciting if they didn't (Rule of Cool (warning: TVTropes))... $\endgroup$ – Spencer Mar 8 at 11:38
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    $\begingroup$ The immensely powerful X-rays laser pulse penetrates the hull and breaches the fusion bottle, leading to a devastating explosion which reduces the enemy ship to molecular dust. $\endgroup$ – AlexP Mar 8 at 11:42
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    $\begingroup$ This is what happens to a vessel when it is exposed to a pressure difference it was not meant to work with. Notice the tanker in this video implodes because the vacuum is in... A pierced space vessel would have the gas leak out, and the ensuing gas jet would give the vessel momentum in the opposite direction, which would not be comfortable to the crew: youtu.be/Zz95_VvTxZM $\endgroup$ – Renan Mar 8 at 12:33
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    $\begingroup$ Um... "energy based projectile"? $\endgroup$ – T.J.L. Mar 8 at 15:09
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    $\begingroup$ As often for hard-SF, there is a relevant Atomic Rocket page: projectrho.com/public_html/rocket/spacegunconvent.php $\endgroup$ – Eth Mar 8 at 15:09
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Wouldn't the surface of the spaceship absorbs all the energy from the pulse and burns?

It might or might not absorb all of the energy, depending on what type of weapon is being considered (different wavelengths of laser light and different types of particle will have different properties). However, it won't burn in the sense you're probably thinking - the amount and, crucially, concentration of energy involved is enough to reduce parts of the hull to plasma. This is the principle of laser ablation. Plasma is much less dense than solid matter, e.g., hull plates. As a result, it expands violently as it changes phases. In other words, it explodes.

One interesting side effect is that if the explosion is too small to simply tear the ship apart, the ship will tend to direct the force outward. The plasma is propelled away from the ship, and as a consequence, the ship is propelled away from the plasma - making it look like laser strikes are physically knocking the ship around.

Even pressurised compartment don't explodes that violently am I right?

Of their own accord, they cannot. Depressurization is not generally as dramatic as shown in movies. These kinds of incidents (when they aren't made up out of whole cloth) tend to be based on airliners that suffer damage to the fuselage, which can indeed rip apart dramatically - but that's because airliners are flying into 500 mile per hour winds. Spacecraft obviously are doing no such thing, and the atmospheric pressure within isn't sufficient to do much damage.

However, if an energy weapon manages to strike through the hull, it will turn the air inside to plasma just as readily as the hull (even more readily, in fact, since it can skip a few endothermic steps along the way), destroying the ship from the inside. And, as AlexP points out in comments, there's always the possibility of touching off secondary explosions from sources like fuel, weapons, or volatile parts of the life support system.

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    $\begingroup$ Depressurization might not be violent if it's just a room at atmospheric pressure - but if the weapon pierces the wall of a high pressure tank (of oxygen, hydrogen, methane, or whatever at 100+ bar), that would be a different story. $\endgroup$ – Skyler Mar 8 at 15:13
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    $\begingroup$ Also the pulse itself will be rather short to avoid wasting energy. After a short moment the expanding cloud of plasma covers the spot where the laser is aimed. This means now the plasma absorbs the laser energy, not the enemy ship. And you have no reason to waste your lasers on plasma. $\endgroup$ – user31389 Mar 8 at 15:13
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    $\begingroup$ Also note that Hiroshima never got into contact with the matter of the bomb that destroyed it. The bomb was detonated 600m above the city and basically "just" released an insane amount of gamma rays (extremely intense light!) which got absorbed by the surrounding air, which instantly turned into extremely hot plasma. It's the air that eventually formed the fire-ball that burned the city, and which created the shock-wave that destroyed the already burning city. Likewise, a spaceship hit by a space weapon (nuclear, laser, whatever) will always be ripped apart by its own matter. $\endgroup$ – cmaster Mar 9 at 20:21
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Can energy based projectile pierce through many layers of structure and blow up the engine totally disregard beer-lambert law?

Give a look at this video showing the effect of a laser pulse on a droplet.

You will see that first the laser vaporize/nebulize part of the droplet, like you can see in the frame below

frame 1

then the resulting shockwave actually deforms the droplet into something looking like a pancake, like you can see in the frame below

frame 2

If the beam is energetic enough in the right wavelength and its dynamic is shorter than the dynamic of the targeted ship, it is plausible that the explosion happens in a dramatic way. The video again shows good example of such behavior.

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  • $\begingroup$ Very cool video :-) $\endgroup$ – cmaster Mar 9 at 20:06
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A laser pulse is nothing else than concentrated light which carries an enormous amount of energy. If that beam of light hits the hull of a ship, the energy is transferred to the material of the hull (or penetrates it, depends on the wavelength and the material), which then is evaporated and turned to plasma. This plasma is expanding at incredible velocity, not unlike an explosion, and damaging other parts of the ship and the hull. The overall effect would be similar to a bombardment with HE-grenades (HighExposive).

Additionally, not every bit of the transmitted energy is going into the plasma, a certain amount will remain on the ship as heat. In a realistic setting, dissipation of heat is a major concern for a spaceship, and if the heat influx is greater than the heat outflux... well, I hope you like saunas.

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Wouldn't the surface of the spaceship absorbs all the energy from the pulse and burns?

Note: I am using heat as an example of energy. Similar explanations exist for other types of energy but heat is the easiest to understand.

If I unleash a flamethrower on your front door, is your house going to distribute and absorb the heat? Or is the door doing to break down first?

Heat can only dissipate at a given rate in a given material. If you apply more heat than can be dissipated, then the area you're supplying the heat to is going to heat up considerably more than the other parts.

Can energy based projectile pierce through many layers of structure and blow up the engine totally disregard beer-lambert law?

Assuming your laser supplies more heat than the ship's hull can dissipate, it's going to heat the point of impact. For the sake of scifi, you can assume that lasers are a tremendous amount of energy that no common material can handle. That makes the most sense:

  • If a common material could handle it, then the laser weapon wouldn't be a good weapon.
  • If hulls in general could handle it, no one would have ever needed to develop shield technology.

The hull melts, it creates a hole, and your laser will now be shooting through the hole, hitting the next thing in its path. This same thing keeps happening over and over, until there is nothing blocking the laser's path anymore.

  • Maybe that happened because it was a clear through-and-through. That wouldn't blow up the ship, but it would of course still be a severe hull breach.
  • Otherwise, you may have hit a critical component of the ship, which exploded the ship to pieces, thus "removing" anything else for your laser to hit. Maybe the explosion is localized and only breaks the ship in two, or maybe it just blows a massive hole in the hull, or maybe the explosion travels through the entire hull.

Drawing from common scifi material, mostly Star Trek in this case, ships are capable of targeting specific parts of their enemy (the engines, the shield generator). Probably because they have some anatomical knowledge of their enemy's ship type.

This means that you could intentionally aim your laser so that you know it will hit a volatile or explosive component (e.g. fusion reactor). This can be an explanation as to why kill shots always blow up the enemy ship rather than disable it.

Even pressurised compartment don't explodes that violently am I right?

A pressurized compartment decompressing is no different from a balloon emptying. At best, the water vapor in the air is going to be visible because outer space is much colder and may freeze the humidity. But other than that, not much will happen.

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  • $\begingroup$ Okay, now try using that flame thrower on the heat shield of a re-entry vehicle? The space shuttle insulation wouldn't even flinch at a blow torch, let alone a flame thrower, except perhaps for the ablating force of the fast-moving air itself. $\endgroup$ – Justin Thyme Mar 8 at 17:07
  • $\begingroup$ @JustinThyme: That's a very skewed example. You are correct, but (a) the insulation is expressly built for that purpose (b) the heat shield is relatively fragile to anything else, e.g. kinetic hits, and (c) heat shields use an ablator. WIthout ablation, there is no heat dissipation. Once the material is gone, the heat shield stops working. At best, it's delays the destruction of the laser. It doesn't block it permanently. $\endgroup$ – Flater Mar 8 at 17:44
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Almost all spaceships have vast stores of energy on board. Military ships of course have a bunch of ordinance, even civilian ships have whatever powers their drive system.

Hits which find such a system make for a big kaboom. Hits which fail to find such a system have virtually no externally visible manifestation--the point of a weapon is to damage what's inside, not to damage the hull. You want to punch through the hull with as small a hole as possible and deliver your energy inside. The performance of the ship may be degraded by the hit but it would take a careful external examination to find the damage. (Internally is another matter, you might have nasty damage.)

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One way it could happen is Thermal Shock. The outer hull of the ship is likely to be very cold, because it is in direct contact with outer space. A laser or maser would be very hot. This temperature difference could lead to catastrophic failures of the effect sections. Plasma based weapons would also have a similar effect. The "swiss cheese" effect is not the only possible outcome.

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  • $\begingroup$ there is no "direct contact" with literal nothingness. ships in space aren't very cold and in fact need to dissipate heat. $\endgroup$ – ths Mar 10 at 0:19
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You are absolutely correct. Directed energy beams are just as much a bust for space military opera as 'energy shields'. In all of the tests of directed energy beam weapons, the best the US army has done is to put holes in the target. There just isn't enough energy in a directed energy beam to do much damage. Certainly not enough to cause a space battleship to be completely destroyed. Like using a laser pointer to 'destroy' a drone.

And there would be no need for shields. Plating and other such coverings on space ships would be much more effective, as well as being passive. 'We lost power to the shields, captain!' just doesn't cut it in warfare. But special reflective coatings, materials with super efficient heat transfer abilities, special hardened plating against radiation (lead as an example) don't suffer from power loss, and would be much more effective, making directed energy beams pretty much useless. At best, 'shields' would be surface charges on the outer skin, sort of like an electrostatic surface charge.

Kinetic weapons will always win out. Less dramatic, but more effective.

So why do sci-fi writers insist on using them?

Perhaps because of the very false belief that exploding percussion weapons don't work in space. The explosive gasses and materials from the explosion don't just vanish, they continue in a 'wave' of energy equivalent to the original energy of the explosion. 'Shrapnel', if you will.

And maybe because of the problems with targeting projectile weapons. Space is huge, and so the battling space ships would have to be very close together in order for evasive action to not be effective. A 'speed of light' weapon is always much more dramatic and immediate than the slowness of space missiles. Imagine how boring it would be if the antagonists had to wait fifteen, twenty minutes for the missiles to get to their target, which of course would no longer be there? 'Fire missile tubes three, four, and five! Now, go for a coffee break and wait to see what happens!' just doesn't generate a lot of suspense. Yet, even directed energy beams take time to travel through astronomical distances.

Or more specifically, a 'space military opera' wouldn't be very entertaining without huge battleships, and even bigger explosions. The stories are written for us earthlings, who think about space warfare as simply naval warfare translated into space. Huge battleships facing off against each other. But it is more like air warfare. There is no advantage to huge 'battleship' fighter planes. Smaller and more maneuverable is better than huge, ungainly and easily targeted blimps.

But my money is on the simple point that space military opera sci-fi writers in general are just not creative enough (lazy?) to think of anything other than the 'same old same old' stock-in-trade directed energy beam weapons. The readers accept it, the writers need to churn out their works quickly, and so they fall back on the same tried-and-true memes. No need to be creative, when you can fill your story with mega explosions, fancy energy beams, impenetrable shields, and huge ships blowing up with loss of all lives and the book will sell.

But the truth is, real 'space warfare' if it ever happens will be boring, slow, plodding, and 99.99999% uneventful. Not really the stuff that makes for good high-suspense action-packed seat-of-your-pants fiction.

So, sci-fi space opera warfare will continue to be energy beams and 'shields up' and huge battleships exploding in space, with the reality hand waved away.

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    $\begingroup$ That just means they're not putting enough energy into the beam. Sci-fi spaceships usually have a much stronger power source than anything on present-day Earth, and spaceships don't have to worry about a pesky atmosphere absorbing any of the beam's energy. $\endgroup$ – eyeballfrog Mar 8 at 17:57
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    $\begingroup$ Saying that directed energy weapons are too weak because there's not enough energy in the beam makes no sense. There is exactly as much energy in the beam as you put into it. Directed energy weapons which travel at or near light speed (lasers and particle beams) have significant merits in space combat and are quite feasible. $\endgroup$ – Elukka Mar 8 at 23:51
  • $\begingroup$ @ Elukka Alas, there will always be people who actually believe cars really DO blow up in a crash they way they do on television and in the movies. $\endgroup$ – Justin Thyme Mar 9 at 14:51
  • $\begingroup$ due to waste heat, very high powered lasers will sooner cook the shooting ship than the target. $\endgroup$ – ths Mar 9 at 20:36
  • $\begingroup$ @ths, true, but the firing ship has control -- they know where that heat is going to be coming from and were able to design for its dissipation; whereas an ideal target surface is one that won't be able to handle the same amount of energy. $\endgroup$ – Charles Duffy Mar 9 at 21:10
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Nuclear Stuff

The energy weapon itself passes straight through the ship without imparting momentum. But all the matter along the way is converted into new and exciting forms of plasma and radiation, which expands outwards and this is the resulting explosion. We're talking a fission/fusion reaction but not a self-sustaining one.

Wouldn't the surface of the spaceship absorbs all the energy from the pulse and burns?

I'd imagine a beam weak enough to be absorbed by the ship probably wouldn't be strong enough to do the nuclear stuff above. And a beam strong enough would probably pass straight through, effectively wasting most of the energy. That makes the weapon tremendously inefficient which is the real problem with beam weapons.

Can energy based projectile pierce through many layers of structure and blow up the engine totally disregard beer-lambert law?

All the Beer-Lambert law says is the beam will do at least as much direct damage to the first few layers as it does to the engine itself. You cannot design a beam that say punches through several layers of bulkhead and then detonates inside the cockpit. But we could still cause the engine itself to detonate by hitting it (and everything in between) hard enough.

This raises a bigger problem: Presumably this engine is nuclear and thus designed to resist rupturing from the nuclear forces inside it. So it might be hard to rupture it using a nuclear based weapon from outside. It would probably be easier to just it hard enough that it stops working but doesn't explode.

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    $\begingroup$ what nuclear stuff? $\endgroup$ – Geronimo Mar 8 at 15:28
  • $\begingroup$ The beam imparts a huge amount of energy to the atoms it passes through. This either causes fusion (smooshing them into each other) or fission (knocking bits off) reactions. Both of these release further energy in the form of heat and radiation. This secondary energy is the cause of the explosion. $\endgroup$ – Daron Mar 8 at 15:56
  • $\begingroup$ I can go into more detail if you tell me how comfortable you are with nuclear physics. $\endgroup$ – Daron Mar 8 at 15:59
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    $\begingroup$ @jdunlop That depends. Exactly how powerful a laser canon are we talking about? $\endgroup$ – Yakk Mar 8 at 21:38
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    $\begingroup$ Hi thanks for the answer however I suspect you might mistaken the condition necessary for chain reaction to occur. $\endgroup$ – user6760 Mar 9 at 4:46

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