21
$\begingroup$

TL,DR:

Kinetic weapons are great at taking down shields, but can't take out the hull. I need an explosive that works in a vacuum to take out the hull. Nukes are out, since they'll hit the atmosphere too.

Here is the situation:

There is a battle around a planet. Two capital ships are in orbit, 180 degrees out of phase. They cannot see each other, but they are so big that changing their orbit is slow, making them very vulnerable to long range attacks.

One ship wants to damage to the other using explosives. A kinetic bombardment is used to take down the shields, however the kinetic weapons cannot do widespread hull damage due to the nano-tech that repairs it. Rounds that combine kinetic attack with explosives will be used to hit the hull, weakening it, and then rip it open with explosives.

What chemical can cause an explosion against the exterior of the ship?

Since both ships are hugging the atmosphere in very low orbits, nuclear weapons cannot be used.

$\endgroup$
  • 1
    $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Aug 23 '17 at 3:09

13 Answers 13

65
$\begingroup$

Almost all currently used explosives have an oxidant (or it's equivalent) "built-in". They already work in space, under water, etc just as well.

Let's look at thermite (which is not an explosive, but incendiary, but it's easy to understand) as an example. It consists of pure aluminium and iron oxide. The aluminium burns by taking the oxygen from iron oxide, resulting in aluminium oxide (slag) and molten iron. The energy of burning aluminium is greater than the energy of "un-burning" iron, so the net result is still hellish fire. It burns the aluminium with oxygen, but it doesn't use external oxygen. Thus, works in space.

The only kind ordnance I know about that won't work in space are thermobarics (fuel-air explosives), but they're extremely rare even with all that oxygen readily available on Earth.

Explosives cannot rely on mixing with anything, including atmospheric oxygen, as a part of the exploding process because to actually explode, it has to go out all at once. If it had to wait for the outer layers to oxidize and expose the inner layers to oxygen - that's how a bonfire works, not an explosion.

$\endgroup$
  • 4
    $\begingroup$ To extend the explanation of the last paragraph: explosions also tend to push the air and its oxygen away from the source of the explosion, further reducing the amount of atmospheric oxygen available to it. $\endgroup$ – David Foerster Aug 22 '17 at 10:50
  • 2
    $\begingroup$ It's also worth noting that most of the effectiveness of explosions is because of the shockwave they produce. With no atmosphere, there will be no shockwave, so even if you can make something explode in space, it will be much less dangerous than an equivalent explosion in an atmosphere. You're better off using the explosion to propel a large amount of shrapnel, or produce a burst of hard radiation. The main sorts of explosives that will retain their effectiveness are things like HESH that cause spalling, or shaped-charge (Munroe effect) warheads that use jets to cut through the hull. $\endgroup$ – anaximander Aug 23 '17 at 8:24
  • 1
    $\begingroup$ Loved the bonfire analogy :) $\endgroup$ – EralpB Aug 23 '17 at 11:38
  • $\begingroup$ Seconding "shaped charge". With this sort of technology, likely "smart bomb" approach would be most efficient: two projectiles, first one a shaped charge to create a hole in the hull, second one, following right on the tail of the first enters the hole and explodes inside, for devastating effects. $\endgroup$ – SF. Aug 23 '17 at 13:15
  • $\begingroup$ non-oxygen binary explosives also exist, you also have things that spontaneously decompose, some nitrogen compound are explosive all on their own without anything else, or course some of these also so volatile turning on the light in the room they are in is enough to get them to explode. $\endgroup$ – John Jun 17 '18 at 18:11
27
$\begingroup$

You can use whatever chemically pure explosive you think sounds the coolest.

Explosives work by being somewhat unstable molecules. Then once they are triggered they rapidly decompose releasing a lot of energy in the process. This happens regardless of the environment they are in. Most of the commonly known explosives (nitroglycerin, C4, or trinitrotoluene) all work like this.

$\endgroup$
  • 2
    $\begingroup$ As another example, the explosives in firearms work underwater: youtube.com/watch?v=OubvTOHWTms So it is logical that similar explosives will work find in space. $\endgroup$ – Kyyshak Aug 21 '17 at 13:12
  • 2
    $\begingroup$ Maybe a quibble, but there is a class of explosives -fuel-air or thermobaric explosives - that require oxygen from the air to function. But most explosives aren't of this type, and don't require anything from the external environment to function. $\endgroup$ – jamesqf Aug 21 '17 at 17:19
  • 1
    $\begingroup$ @jamesqf That is why I wasn't talking about fuel air mixtures, or things that just burn really fast like blackpowder. By definition a fuel air mixture isn't chemically pure. $\endgroup$ – sphennings Aug 21 '17 at 17:20
  • $\begingroup$ I would like to nominate (chlorine trifluoride)[en.wikipedia.org/wiki/Chlorine_trifluoride]. It oxidizes in the absence of atmospheric oxygen and reacts explosively with - among other things - water. It ignites glass and asbestos on contact. The only known insulation is metal treated with fluoride gas to create a protective layer of fluoride. If that layer is at all compromised, it reacts violently with the metal. $\endgroup$ – Engineer Toast Aug 21 '17 at 21:16
  • $\begingroup$ @kyyshak Technically, the bullets in those firearms "explode" in the presence of oxygen. The oxygen in this case is encapsulated in the bullet itself, along with the gunpowder. (It's kind of why corning gunpowder is a thing; course grain leaves gaps for air, thus helping a better burn than densely-packed fine powder.) The bullet itself is waterproof, so water doesn't mix with the gunpowder/air mixture, and thus the bullet fires underwater. $\endgroup$ – EightyEighty Aug 21 '17 at 21:26
11
$\begingroup$

See FOOF. Pack some of this into a warhead somehow and I dare you to find a way to make it stop burning.

Dioxygen Difluoride is a particularly reactive compound of already particularly reactive fluorine and oxygen. It's ludicrously dangerous production method as well as its reactivity with essentially everything, at any temperature make it fairly famous in the chemistry community. See the wikipedia page for details, but it truly does react with essentially anything.

The main difficulty with such a weapon would be that it would tend not to stick to hull of the enemy ship as it decomposed, but this would be a problem with pretty much any reactive agent, which is likely your best bet, aside from nuclear weapons.

$\endgroup$
  • 7
    $\begingroup$ In truth, the answer was improved because of the comment. It was not a good answer, thanks for keeping the site high-quality! :) $\endgroup$ – bendl Aug 21 '17 at 14:04
3
$\begingroup$

You can use any self-oxidising explosive, which is almost all of them, or you can use a warhead that creates something horribly unstable that will damage anything that it comes in contact with. Liquid Oxygen or Liquid Ozone are good candidates since anything that's spent a long time in space is likely to have surfaces without protective oxide layers but there's a limit to overall damage with these compounds to spite their reactivity. Then there's FOOF which is super nasty but it's components are relatively stable and transportable, I wouldn't want to be the systems engineer to who has to try to come up with a way to neutralise FOOF, and when it gets inside it'll kill the crew regardless of hull sealing technology. Oxygen difluoride would have similar effects, be less dangerous to store, but less easily synthesised within a warhead. If you want to use an explosive that isn't self-oxidising you use it plus an oxidiser, like Hydrogen Peroxide, that stores safely.

$\endgroup$
3
$\begingroup$

Getting an explosion in absence of oxygen is no big trouble.

The first obvious way is to use an explosive that already has its oxygen stored within. Pretty much everything used in present-day guns or cannons qualifies for that, this is why you can (in principle, neglecting other little details) fire a gun underwater or even in space no problemo. Pretty much every solid rocket fuel also qualifies.
Anything and everything used by and used against submarines during World War II would demonstrably do. Torpedoes, water bombs, and mines explode just fine without oxygen.

The second obvious way is to use a pressurized tank full of hydrogen and a pressurized tank full of oxygen, break the tanks open, add the tiniest little spark, and you have hell break loose. Gas explosions, next to dust/aerosol explosions ("thermobaric weapon") are some of the most devastating explosions we know.
If you wish to be a bit more posh, substitute oxygen with chloride, and you do not even need a spark. Releasing the gas and exposing it to sunlight suffices. That's truly an explosion in absence of oxygen.

The third, somewhat cheating way is to not cause an explosion at all, but to have gas expand rapidly anyway -- to the exact same effect. How would you do that? Take a chemical which is cheap/easily produced or abundant, and has a low boiling temperature (say, carbon dioxide, but quicksilver or water would do as well) and heat it to considerable temperature (2,000-3,000K) very rapidly. I'll leave to your imagination what the best way would be to achieve this. If nothing else, it might convert kinetic energy from the impact (but in Sci-Fi, it can be whatever... energy from a "plasma generator"?).
This is not-an-explosion, which however has the same net effect and works perfectly well in absence of oxygen.

Nuclear weapons are out of the question. But why? The rare element catalysium will, if added to normal plutonium, increase the yield to upwards of 97%, and with a proper bounconium reflector to upwards of 99.975%. Fallout is minimal.
Bullshit? Well, no, it's actually exactly what, in the real world, boosted fission bombs (and beryllium or carbide reflectors) are trying to achieve, and they do achieve it, only not at that scale (but it's fiction, after all).

$\endgroup$
  • $\begingroup$ Why oxigen stored in the explosive? Any unstable bound will do. Even N<sub>7</sub>. $\endgroup$ – Hennes Aug 21 '17 at 20:27
  • 1
    $\begingroup$ Gas explosions don't work in space. The lack of pressure means that the hydrogen and oxygen will rapidly disperse, rather than mix. Also, this would be an adiabatic expansion, which cools the remaining hydrogen and oxygen. $\endgroup$ – MSalters Aug 22 '17 at 7:07
  • $\begingroup$ @MSalters> assuming you have a container (don't see how to move the gas around otherwise), it will only break after your ignite your gas mix and the pressure builds up to its failure point. That gives your explosion a good lead on dispersion. If, in addition, you manage to trigger a detonation, the shock-wave will move at speeds of thousands of km/h. That means even a 10m container will explode in under 0.01s. I don't really see the gas disperse in that interval. $\endgroup$ – spectras Aug 22 '17 at 13:30
  • $\begingroup$ @spectras: The initial idea was two tanks, so not mixed, and "break the tanks open". That just vents gases into space, cooling (potentially freezing) the remaining hydrogen and oxygen. Carrying a single tank will cause the two to be pre-mixed'. BTW, pressurized hydrogen will be escaping extremely rapidly. You'd need to liquify it. $\endgroup$ – MSalters Aug 22 '17 at 13:56
  • $\begingroup$ @MSalters> Ah, of course they'd have to be mixed already. That's true in atmosphere as well, if they're not it will just burn at mixing point. Intense burn, but not an explosion. $\endgroup$ – spectras Aug 22 '17 at 14:48
2
$\begingroup$

Try looking up some of NASAs monopropellant fuels. Hydrazine, for instance, is a chemical fuel that burns in space with no oxygen. I'm sure if you got enough of it then it would be fine.

Alternatively, take the oxygen with you. Use conventional explosives but at the head of the warhead is a delicate oxygen container which bursts, surrounding the impact point with oxygen immediately before the detonator goes off.

Option three would be to use just highly pressurised oxygen without explosives. Oxygen is surprisingly reactive in high concentrations (look up videos of what liquid oxygen can do) and, depending on the metal used in hull construction, you could burst through it by releasing the physical pressure on the cannister, then as soon as the oxygen comes in contact with any source of ignition (heat, electricity, both pretty common on spaceships) then it'd burn through most things.

$\endgroup$
1
$\begingroup$

1) No chemical, but nuclear weapons. They won't make shock wave or anything like that, they will be only ball of expanding plasma from the detination.

So this weapon on impact will not need oxygen, it will emit high amount of heat, radioactivity, EMP pulse theoretically...anything like that can damage enemy ship drastically. Or their crew.

2) In Honor Harrington universe, they used also laser-warheads, those rockets went near the target and emitted powerful lasers to penetrate the enemy ships. (They used nuclear warheads too, if lasers were out of stock)

Adding link to wiki about missiles used in Harrington world (even though those were for more advanced future probably, it might be good for read, too): http://honorverse.wikia.com/wiki/Missile

$\endgroup$
  • 1
    $\begingroup$ @AricFowler You probably misunderstood the laser thingie. It is not fired from ship, it is rocket that flies as normal one, but instead of detonation it releases laser pulse. $\endgroup$ – Antoine Hejlík Aug 21 '17 at 12:14
  • $\begingroup$ No, that won't be such a problem for a planet. As long as you are on proper orbit outside the atmosphere. $\endgroup$ – Antoine Hejlík Aug 21 '17 at 12:18
1
$\begingroup$

Just add oxygen to your own bombs. Have your engineers do stoichiometry to determine how much oxygen the other components of your bombs need to explode properly and then just add that to your explosive device. People literally have tanks of oxygen attached to their nose all the time.

You're not going to get combustion without oxygen and since you nixed nuclear stuff the most you can hope for is something expanding quickly and making a shockwave. You're basically stuck with your weapons either having their own oxygen or being some rapidly expanding gas for "reasons".

$\endgroup$
1
$\begingroup$

Explosions are fine. They are not worth as much in space where there is not gas to produce a shock wave. Also the ship would see the explosive coming kilometers away, shoot it with something like an Aegis gun and disable it.

Kinetic impacts are the way to go. You can shoot them all you want but their trajectories will change minimally: they have inertia. Your kinetic projectile is too fast to travel in the same orbit as the capitol ships. But you could use a fast projectile and some tricks to get it to hit your target.

1: Bank it around the gravity well. You could fire your fast projectile low, banking it around the earth in a slingshot-like maneuver. It is too fast to stay in that low trajectory but the proximity of the planet will curve its trajectory. If your math is good it will come back up from the planet under your target. enter image description here from https://astronomy.stackexchange.com/questions/5934/how-does-a-gravity-slingshot-actually-work/5936

2: Skip it off the atmosphere. from https://newwest.net/main/article/meteor_brings_back_memories_of_the_great_daylight_fireball_of_1972/

Thousands of people from Utah to Canada had witnessed what would be called The Great Daylight Fireball of 1972. There were hundreds of pictures taken of the thing, and a pair of home movies, and it was tracked using infrared sensors aboard an Air Force satellite.

Scientists inferring from the temperature of the ball and its 900-mile trajectory from Utah to Alberta calculated that it passed over Montana at an altitude of less than 35 miles, was between ten and thirty feet in diameter, and weighed at least 4,000 tons, big enough to obliterate a Denver-sized city with a force equal to Little Boy and Fat Man, the uranium and plutonium bombs that destroyed Hiroshima and Nagasaki. Because no trace of the beast has ever been found, and because no sonic booms were heard as it sailed across Canada, astrophysicists now believe its low angle of descent allowed it to skip off the earth’s atmosphere like a flat stone on a still lake.

If you fired your projectile at a low trajectory you could skip it up off the atmosphere, again with the projectile rising up under your target ship.

3: Late boost. If your projectile can carry explosives, why not have it carry rocket fuel? Send it back along the orbit. Then when your target ship is 100 km out you accelerate the projectile in a straight line over the remaining distance into your target. Even if defensive fire incapacitates the rocket before it is exhausted the massive payload will continue along its trajectory.

$\endgroup$
  • $\begingroup$ Remember that the ships are pretty much touching the atmosphere, so there is nowhere for projectiles to go downwards without burning up or being deflected $\endgroup$ – Aric Aug 22 '17 at 7:39
  • $\begingroup$ ICBMs and cruise missiles go thru the atmosphere just fine. Your late boost projectile could do exactly that - an atmospheric rocket that skims the surface, traveling a straight line from one ship and arriving at the other just as it comes over the horizon. The last 100 km of acceleration will be through decreasingly dense atmosphere. Plus it would be hard to see this one coming at a distance because it would be so low. $\endgroup$ – Willk Aug 22 '17 at 20:25
  • 2
    $\begingroup$ If your weapon is a bucketful of appropriately size steel shot you can set off a small explosion shortly before impact so that you have a large number of small projectile doing wide area damage instead of a large projectile doing heavy localized damage. This can also reduce the chance of a near-miss for a balistic design. A more complex design will result in a more equalized damage distribution. The shot can be made of steel, depleted uranium, etc. as desired. $\endgroup$ – Gary Walker Aug 23 '17 at 0:01
  • $\begingroup$ @Gary Walker - space shotgun! I like it. $\endgroup$ – Willk Aug 23 '17 at 15:02
1
$\begingroup$

If you want to avoid oxygen completely, consider Chlorine trifluoride. It can be condensed to a liquid at root temperature (so can be easily delivered to the target) and will ignite and / or explode on contact with most substances, including glass and water. Reaction byproducts typically include strong acids as a bonus.

$\endgroup$
1
$\begingroup$

The contrary approach would likely be the most mass efficient (while there is no weight in your space I guess, there is mass to accelerate!): Just send an oxidiser that is aggressive enough to use your target as fuel. Such do exist in the real world.

Also be aware that halogens can create very similar reactions with fuels as oxygen can - flames included! Actually, any sufficiently self-sustaining exothermic reaction can go that way, reaction heat vaporises things into a gas/plasma that is even more reactive than the solid material...

What will help you is that a lot of metals will not have been slowly pre-oxidised if they've been in space, in the best case the oxide layers that used to exist have been punctured or ablated by heat, vapor pressure effects, micro impacts etc. Many real-world light metal alloys would be extremely unstable if they didn't instantly build a passive oxide layer from atmospheric oxygen (which they can't as well in a more vigorous reaction. Compare what a dishwasher tends to do to aluminium stuff..)

BTW, iron rusting is an oxidation too - slow but rather destructive. Sufficiently fine iron dust is actually know to catch fire all by itself in atmospheric conditions...

$\endgroup$
0
$\begingroup$

Seems like chunking a bomb with oxygen is a real fine waste of oxygen in space.
On Earth, explosions work great because we have a ready supply of Oxygen for combustion. Consider some combustion examples:

enter image description here

Also, consider that of the elements used in explosives Oxygen is one of the greatest mass. So if you wanted to make an actual fireball in space you need a really heavy big bomb.

The majority damage from explosions also come from the expansion of gasses creating a shockwave. In space, the shockwave of expansion will dissipate rapidly (no medium to pass through). Therefore, unless the explosion is inside the enemy ship you likely won't be creating any kind of damage.

Here is the only way I can see this working: You load up a normal exploding ordinance round and fire at the enemy vessel. The round penetrates the hull and then explodes inside the ship. The air inside the enemy ship is used for combustion. The worst that could happen is the round doesn't explode and just punches a hole in the enemy ship, which is just fine for you anyway. If it does explode inside the enemy ship that may create a nice big explosion indeed. Ships are designed to contain pressure from space, but would it be able to handle a shockwave inside? The normal pressure inside the ship wants to escape to space anyway so just a little help along the way and you may end up with a nice explosion.

$\endgroup$
0
$\begingroup$

You could use a self oxidising explosive, like thermite(It is rust powder and very, very finely powdered aluminum, and it takes oxygen from the rust)

$\endgroup$
  • 1
    $\begingroup$ There is already an answer (the one with the most upvotes, in fact) which suggests this and also gives thermite as an example $\endgroup$ – Aric Aug 23 '17 at 14:49
  • 1
    $\begingroup$ Well, I didnt read through, just felt like answering the question. Thanks for telling me though. EDIT: It even talks about the molten aluminum oxide and iron. $\endgroup$ – TheSleepingInsomniac Aug 23 '17 at 20:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.