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I've been thinking about a steampunk style world where a lot of the transport is done with balloon powered airships. Obviously there are conflicts and I'm trying to think of ways these craft could be a little more resilient to attack. A flying navy.

At the moment I can't see any reason why a cannon ball through the balloon and the ship will crash fairly spectacularly!

What defensive measures can an airship take to prevent itself from crashing as soon as it's attacked?

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  • $\begingroup$ Not a complete answer but look at how Terry Brook's handles airships in his Shannara series. He has them levitated through their thrust rather than bouyancy (less physical I know) but this eliminates the large balloon which is a main weak point while maintaining the steampunk feel. $\endgroup$
    – Godric Seer
    Sep 18 '14 at 12:08
  • $\begingroup$ We're talking airships which have the same general layout as Zeppelins? How big? $\endgroup$
    – PipperChip
    Sep 18 '14 at 18:46
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    $\begingroup$ Also, don't forget that cannon (at least in the Napoleon era) didn't have much of range - less than 2km under ideal conditions and more like 1.5km average. I don't know if you were planning on having airship shoot at each other, but they'd have to be really close to be able to do that. $\endgroup$
    – Richiban
    Jan 16 '15 at 12:09
  • $\begingroup$ Actually a single cannon shot would just make a slow leak in an airship bag, rigid or nonrigid. $\endgroup$
    – Oldcat
    Dec 2 '15 at 23:23
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    $\begingroup$ Airships are flimsy? Did the numerous pilots in WW1 that got killed trying to shoot down Zeppelins do that just for fun? ....... Please investigate, and realize you are working on a false premise. $\endgroup$
    – user79911
    Oct 26 '20 at 14:20
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Here are a few thoughts that come to mind:

  • Provide a system where incoming projectiles can be deflected.
  • Possible a system where human gunners would try and shoot a cannonball to knock it off course
    • Another possibility of this would be an automated system.
  • Force fields
  • Plate it in metal (you'd have to work out the physics for that).
    • Sloped metal plating format (T-34) could reduce thickness and therefore weight.
  • Remove technology that would easily destroy it (not all cannons can shoot very far up)
  • Use a series of pockets filled with air inside the balloon. That way not all of the air would leave the balloon if some pockets were punctured
  • Use a lifting gas which is not flammable. Thermal airships use hot air, for instance.

I'm following the suggestion in this meta post on how to answer list questions. Please feel free to add your own possibilities to this answer.

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    $\begingroup$ While use of a non-flammable lifting gas could certainly prevent loss of life in the event of a puncture (not to mention preventing accidental ignition from within), it wouldn't necessarily keep the ship from going down; if all your hot air is escaping through the massive, gaping hole, it isn't going to be doing a very good job of keeping your ship in the air. $\endgroup$
    – Katie
    Sep 18 '14 at 18:35
  • $\begingroup$ Would brass-coated ceramic foam be a suitable replacement for armour plating? $\endgroup$
    – Scott Downey
    Nov 11 '14 at 9:12
  • $\begingroup$ @Katie - I agree. The US used helium as its lifting gas for its airships, and they crashed regularly. Storms, structural failures, etc. $\endgroup$
    – Oldcat
    Nov 13 '14 at 19:53
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    $\begingroup$ @ScottDowney - the lifting weight of a gas is fairly limited. Every pound added armoring the gasbag takes away from the crew and cargo weight. $\endgroup$
    – Oldcat
    Nov 13 '14 at 19:55
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You're starting from a false premise.

Look at the performance of airships during World War I to see how things really work out. The Zeppelin bombers could take an incredible amount of punishment without crashing -- it was only with the development of incendiary ammunition that British fighters had a hope of shooting them down. If your lifting gas is non-flammable, even that isn't an option.

The fundamental fact is that any realistic airship is huge. A Hindenburg-class airship has about 300,000 square feet of envelope fabric. This fabric provides essentially no resistance to penetration, so a cannon shell will simply pass through without detonating, leaving a pair of tiny little holes. (A time fuse could make the shell detonate within the envelope, leaving lots of tiny little holes, but the results wouldn't differ much.) Since a rigid airship uses an unpressurized envelope, the lifting gas is in no hurry to escape, and even if the attacker can turn it into Swiss cheese, it'll take hours or days for the airship to lose the ability to stay aloft.

There's no need to armor an airship against enemy fire: its sheer size is sufficient protection. You may want to armor the cockpit, engines, and other critical structures, but that's a much smaller area that needs protection.

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  • $\begingroup$ Yes, I remember watching that. A bullet sized hole won't let much gas through, and compared to the total volume is not significant in a short time scale. However, planes were using machine guns firing bullets. Would cannon balls and blunderbus rounds create large gaping holes? $\endgroup$
    – JDługosz
    Jan 10 '15 at 8:20
  • $\begingroup$ @jdlugosz, a cannon ball would create a cannon-ball-sized hole, which, on the scale of an airship, is still tiny. $\endgroup$
    – Mark
    Jan 10 '15 at 9:22
  • $\begingroup$ Make a purpose-specific weapon based on the blunderbus filled with lengths of chain: two balls with a strong wire between them, or a 3-armed bolis if that's more stable. The idea is to make a long slash, not a neat hole. If a few of those intersect then the envelope will fall apart in tatters. Each slash will leak far more than a neat hole, on its own. $\endgroup$
    – JDługosz
    Jan 10 '15 at 22:40
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    $\begingroup$ @jdlugosz, sounds like a variation on chain shot/bolo shot. That might be a threat, if it's got enough range to hit an airship in flight. $\endgroup$
    – Mark
    Jan 10 '15 at 22:44
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    $\begingroup$ @Mark, there is: self-sealing membranes are heavy and are only good against small holes, not long tears. Since small holes aren't a threat, it's not worth the weight penalty. $\endgroup$
    – Mark
    Jan 12 '15 at 5:12
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I'm going to post it as an answer (rather than in the question) because it's the only idea I have - I'd really like to get some other (and hopefully) better ones!

The ship could use a series of pockets inside the balloon (similar to the watertight sections in the Titanic). Any cannon/bullet which strikes the balloon would go straight through but only a limited amount of air would escape. Obviously there would be a certain percentage of these which would need to be in tact for the craft to continue to fly.

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    $\begingroup$ We all know what happened to Titanic :D $\endgroup$
    – Envite
    Sep 18 '14 at 8:58
  • $\begingroup$ You're writing about several layers of inflation (like an onion), or several pockets (if one pops, there are 4 or 5 other pockets in other parts of the balloon)? $\endgroup$
    – Shokhet
    Nov 11 '14 at 0:54
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    $\begingroup$ @Shokhet the latter. It's what was used in most actual airships and it works. It's also a lot easier to build, and you can make the bags spherical which is a far more optimal shape for a pressure container than a cigar. $\endgroup$
    – jwenting
    Nov 11 '14 at 8:04
  • $\begingroup$ @jwenting ....I'm unfamiliar with the construction of the Titanic ;-) ....thanks for explaining :-) $\endgroup$
    – Shokhet
    Nov 11 '14 at 14:33
  • $\begingroup$ @Shokhet the what? imdb.com/title/tt1627715/plotsummary?ref_=tt_ov_pl $\endgroup$
    – Liath
    Nov 11 '14 at 14:35
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Your question is premised upon gas envelopes being very fragile, but there is no reason this has to be so.

You could make the gas envelopes out of some strong fibers which could absorb most impacts (think kevlar). The overpressure of the impact would have to be absorbed, but some relief valves mean you lose some lifting gas rather than pop.

Smaller projectiles are of no concern because a polymer coating on the inside can be self-healing. So long as the projectile has not caused a hole so large the polymer cannot touch itself again, it could reseal the hole (as a little experiment on polymers, fill a plastic sandwich bag with water and stick it with a needle - when you pull out the needle, it will not leak).

Worse comes to worse, you lose one envelope - prudence dictates that your lifting body is comprised of several independent gas envelopes. This has been fairly common in real-world dirigibles.

I'm not sure how much weight it would add for an armor mesh (a thin mail armor to protect against shrapnel cutting through), but that is another possibility to bolster resistance. Keep in mind that this is not intended to be thick enough to stop everything, just some shrapnel from flack. One must accept the possibility of being hit - not much different than a surface fleet navy getting hit with shells from battleships.

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    $\begingroup$ Actually the impact pressure would be spread over a massive volume so would probably automatically get damped/absorbed/spread out, $\endgroup$
    – Tim B
    Nov 7 '14 at 23:00
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One very important thing would be the material of the airship envelope and design - Even folks who agree with the hydrogen hypothesis of the hindenburg disaster seem to think that the coating contributed. You don't want your airships covered in incendiary compounds! You do, however want tough, light materials. Apparently silk (while admittedly very expensive) was used in early bullet proof vests and effective against black powder rounds (However I will leave actual testing of small cannon balls against period accurate materials to the reader)

Secondly, you could design your airships to consist of independent 'cells'. Even if one or more cells were breached, the other cells would still hold up, slowing down your decent.

Otherwise, your design choices may be similar to a contemporary/parallel period ship. You'd want some peril of fire (you are powering this with stream and other such dangerous things), and ammo bunker explosions. Danger is exciting

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    $\begingroup$ silk is highly resilient, and if layered correctly can indeed help against blunt force impact (black powder rounds from early guns were slow, large surface area, much like a slug round fired from a modern day shotgun). AA rounds tend to be faster, smaller, pointy bits of steel. I doubt silk would do much to stop them unless you use a lot of layers. But the principle holds with other materials. $\endgroup$
    – jwenting
    Nov 11 '14 at 8:11
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The other answers all have good ideas for making the airship more resilient (or reasons to believe it already may be so). In the interest of covering other possibilities, I'll take a slightly different route, and suggest that the best defense is a strong offense. Keep the airships back away from the front lines, but give them the longest-range guns possible, so that they can bombard targets from far away, before they become a target themselves. Airships, with their great altitude, make a perfect platform for long-range canon fire. Of course, the enemy airships will likely be taking the same strategy, leading to an interesting standoff, where each side is trying to be the first to score a hit while staying out of the other's range.

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  • $\begingroup$ Actually, not that good a cannon platform once you count in recoil. You need to know where you are to aim at long ranges, and recoil messes that up. $\endgroup$
    – Oldcat
    Nov 13 '14 at 19:51
  • $\begingroup$ @Oldcat: Check out the Norden Bombsight. en.wikipedia.org/wiki/Norden_bombsight. Airships with mechanical analogue computers for aiming: how steampunk can you get? $\endgroup$
    – Paul Johnson
    Apr 8 '17 at 12:32
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As others have noted, compartmentalization would work. Alternatively, use a scale mail approach - a scale can be pushed aside, then pressure will simply put it back. The cannonball flies through but the holes are temporary. A variant on silly putty could also work for this - a liquid in the material flows into the hole, solidifying in contact with the gas.

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