"Puncturing Hovercraft Skirts" Topic

So what happens when you puncture the skirt of a hovercraft?

Are the skirts compartmentalized so that a few holes won't effect the air cushion?

Or would it be much easier to immobilize a hovercraft by shooting the skirt compared to tracking a 20th century tank?

Depends on the design. There are three that come to mind and yes the bag or tube style would be in danger but I have heard of safety features that are basically loose flaps inside the shirt that act as pressure dressing from within.

A rod or finger style that is a series of separate long sections and a stacked cone or cell design that usually are easily replaceable as they snack in and out of the skirt support.

But I do not know about easier or not, one would assume so if sitting still…hover craft are pretty fast and throw up a bunch of dust and air.

?

My understanding is that, in most designs, holes on the order of small arms rounds would have negligible effect. You'd need to either put a LOT of such little holes in the skirts or blow larger chunks out of the skirt to seriously affect the plenum pressure.

Doug

I've seen a hovercraft (not military grade) blow out half its skirts just trying to load up into its transport trailer.

So yes, I would think that a .50 cal burst into the skirts would virtually immobilize a hovercraft.

I think this illustrates why hovercraft are really only useful in situations where they won't get shot at. No matter how you look at it, they ride on airbags that are pretty easy to puncture.

to immobilize a hovercraft you need to shot up the lift fans not the skirt

For one it takes a lot of HE to damage the skirt ( as in most AT mines will not do enough damage to be noticed) and if you have one big enough to take out the skirt the hovercraft has all kinds of other problems that the skirt would be low on the list. Small arms and AT weapons would be a wast of ammo on the skirts of modern hovercraft even if they do put a hole in it.

All this is because they are super tough and flexible. explosions just fold/push them out of the way and small arms don't penetrate. Also it takes a lot of holes to over come the power of the lifting fans.

I saw a test photo once were a contractor drilled 1 in. holes with 1/2 in. spaces over a whole skirt and the craft still hovered.

(not military grade)

That may be the critical difference.

Doug

I've landed on a couple shores in them… the rubber is very thick and sturdy. Granted, sand does not pose a penetration threat, but rocky beaches would. The LCAC is designed to land in an opposed environment with the expectation of incoming rounds. The ability to ingest air to fill the bladder is far more critical. If the lift fans are disabled, then the vehicle is useless. The intakes are far easier to disable.

it should be like firing small arms against a zeppeling. The only, but very important diference, is that te hovercraft donīt have a fixed amount of air inside that you can deplete. The fans are renoving the air all the time, so you should be able to make holes big enough to make the cushion to loose more air than it gets through the fans

Holes themselves are not the issue…tears, slices, and rips would be bad.

So a single 50cal would not ruin the day but a chain of 50cal rounds coming down range would and could create a serious problem.

Again it depends on the design.

But also mentioned was function. Hovercraft are meant for special application to environmental conditions…land to water back to land…dealing with the conditions easily.

Just about any soft or unarmored vehicles would suffer serious issue from series of 50cal rounds coming down range.

Hovercraft in open battlefield is liken to walkers…more of a cosmetic guilty pleasure than a real functional element :)

I'm not sure a few .50cal guns would even slow down an LCAC… RPGs and bigger guns, sure.

The problem with HE is that you can effectively depressurize the plenum chamber, which leaves you immobilized in the impact zone for however long it takes to refill the chamber. I don't think you'd get a second chance to leave the beaten zone if that happened!

I imagine they pump so much air through them that even a large number of small holes will have little effect, e.g. like on the LCAC.

They also produced self-sealing fuel tanks back in WWII, so no reason to doubt that the air cushion chambers have this capability as well.

Also, in some scifi settings, the plenums are armored so, this is another design element to take into account.

"They also produced self-sealing fuel tanks back in WWII, so no reason to doubt that the air cushion chambers have this capability as well."

Only if you're willing to fill the air cushion chambers with gasoline!

"Self-sealing tanks have two layers of rubber, one of vulcanized rubber and one of untreated rubber that can absorb oil and expand when wet. When a fuel tank is punctured, the fuel will spill on to the layers, causing the swelling of the untreated layer, thus sealing the puncture."

They sell green goop that they put in tires, to keep them from flattening immediately due to a puncture. Works with air leaks, so presumably could work for this application.

Memory materials are already being worked with. I assume that you could easily justify self-healing memory materials in a future where a hovertank is viable.

"They sell green goop that they put in tires, to keep them from flattening immediately due to a puncture. Works with air leaks, so presumably could work for this application."

"As the SLiME treated tube rotates, centrifugal force pushes the sealant to the tread area creating a layer of protection, repairing punctures as they occur or treating existing punctures. SLiME is not intended for use in tubes losing pressure from sidewall punctures, bead leaks, damaged rims or faulty valves."

The issue that I see is scale--a leak in a tire is a millimeter across, perhaps, so a viscous liquid can hold across that distance. If the hole is 10mm across, I have a hard time imagining something goopy enough not to flipple out.

The bigger issue is how much pressure you would need to hold the goop against the sides of the bladder. The centrifugal force of a bicycle tire makes this easy--note that they specify that it won't work on sidewalls. Even if you generate as much internal pressure in the bladder as the Slime experiences inside a bicycle tire (with centrifugal force taken into account), that pressure isn't doing anything to press the goop to the sides. It'll be just as happy on the bottom of the bladder, doing nothing useful.

The military question should be what weapon does it take to effectively deal with Hovercraft.

They still put "rubber" tires on light armored vehicles, what weapons have been designed expressly for destroying said tires?

There a several I have seen, but they are for law enforcement and not military use. Not say they aren't applicable, just haven't seen them deployed in a military sense.

Okay, so we need to develop quick-hardening slime, that cures when it gets outside the chamber.

I imagine it will be available before, or by the time hover tanks become a reality.

It's also probably not an issue at all, since far more air will be displaced out the bottom of the chamber to hold up a 100+ ton vehicle, than will ever be lost through any small holes made in the sides of them.

Silly Putty will fix everything.

tsk tsk tsk…duct tape can and will fix everything :)

"It's also probably not an issue at all, since far more air will be displaced out the bottom of the chamber to hold up a 100+ ton vehicle, than will ever be lost through any small holes made in the sides of them."

It's not an issue of total air displacement, it's an issue of whether the bladders can maintain enough rigidity to create the plenum chamber. Suppose you have 20 bladders around the perimeter of the plenum (it's only a simple example, number doesn't really matter). If one bladder depressurizes, you now have a piece of fabric flapping around with higher-pressure air behind it. That's where you're going to get significant leakage out the side, which is how the hovercraft loses performance. If you've got the dead bladder on one side, you're going to get some sideways push that you'll have to counter. You may also get rotation, if the loss is near the front or rear side of the vehicle.

If we only lose one of our 20 bladders, that section is still going to hold it some of the air, just not nearly as effectively as if it was fully inflated. Let's suppose that, even though we've lost 5% of our bladders, we only lose 2% of our containment. Not much of a problem, is it? The problem comes when we lose, say, three bladders in a row. Now the deflated middle bladder is nearly unanchored, so our total containment loss is going to look more 10-12%. Again, that doesn't seem too bad until we consider that these are all likely on the same side, so we're getting air blowing out that side causing lateral thrust.

Anyhow, these are pretty charitable assumptions. A hovercraft naturally loses efficiency very quickly as it loses plenum chamber pressure. If the 10% containment loss means that the skirts are dragging 20% of the time (even if only a little), we've gone from skimming along like an air hockey puck to pulling a travois.

We have spray foams for riot control that harden and expand almost instantly.

Large rips and tears….can see it now .."lads prepare to repel ACVs,stow firearms don yer battleaxes!Lets have at em boys!"

So what happens when you puncture the skirt of a hovercraft?

If it's self-healing nanotech holes don't matter.

Taken to its logical extreme, you don't need a blast of air to hover on, just a rolling cloud of nanobot-infested buckyball aerogel.

I wonder if one the objections to armoured cars back in WWI was: "but the tires will just get punctured by bullets and shrapnel."

The skirts on the Slammers' combat cars get holes in them quite often (by buzzbombs generally, when the CID charges aren't armed) and this does tend to reduce the combat effectiveness of them.

However, a combat car's lift is much greater than it's mass, and is capable of even 'leaping' small terrain purely on the lift fans.

Top Gun Ace said on 23 Feb 2011 4:44 p.m. PST--

"Okay, so we need to develop quick-hardening slime, that cures when it gets outside the chamber.

I imagine it will be available before, or by the time hover tanks become a reality."

Quick-hardening slime would be a great anti-personnel weapon that the hovercraft could expel from vents or hoses, like the live steam anti-boarder hoses of the late 19th century.

Trouble is, what do you do with the insta-statues once they're immobilized?

Trouble is, what do you do with the insta-statues once they're immobilized?

Push them over the side, at least until the insta-statue slime gets banned as a weapon, like live steam.

Then it's called a War Crime.