Realistic TL9 or 10 "corridor blocker" foam grenades?

[Peter Knutsen]

I watched "World War Z" a day or two ago, and I've played a bunch of "7 Days to Die" recently.

The movie got me thinking that it'd be nice to be able to have a sort of "foam grenade" that creates a huge space-filling blob of foam, one that zombies or other pursues will need to spend some time chewing through, so that you can use it to block a corridor if you're being pursued, or maybe even a door opening.

I doubt anything much can be achieved here at mid or (arguably) late GURPS TL8, but what about reasonable speculation about TL 9 or 10?

I'm imagining a fairly large can, probably the size of a spray can, rather than a hand grenade, and I'm thinking it becomes more feasible to get a larger foam volume if such a device can only function in a terrestrial atmosphere, that is if it is "allowed" to make use of atmospheric gasses at the partial pressures that we have on our planet, and possibly only functioning optimally if the total pressure is at least not too far from 1 atmosphere.

But is it even feasible? Given that the expansion will most likely be even in all directions, what's needed is a blob with a diameter of at least 1.8 meters, preferably even 2.5. (In fact, direction-controlled expansion is incompatible with the envisioned usage mode, which is "press the big red button, trow the thing and then run!")

And it needs to be cheap. As I see it, part of the charm of this non-lethal anti pursuer device is that spy agencies and the like can hand them out to their operatives without grave budgetary concerns. I'm sure early TL9 can give me an absurdly wonderful nanotech-based prototype, that'll work in a vacuum, and even do my laundry for me, but if it costs a billion dollars then it's not really something that's going to see any actual use, whether or not there is a zombie apocalypse.

[Anthony]

A foam grenade is almost certainly not possible, a foam sprayer is pretty dubious. You want about 3 cubic meters of foam, and to achieve that you either need 3 cubic meters of compressed gas in your grenade, or you need to arrange for 3 cubic meters of air to mix with the foaming liquid. You can't realistically fit 3 cubic meters of compressed gas in a grenade, you're not going to get more than a factor of 1,000 or so compression, and a 3 liter grenade is a large milk container, not a spray can. Even if you solve the gas problem, the best quality aerogels only manage around 1 kg of solids per cubic meter, and that's with industrial processes.

You might have better luck with web, glue, or slime grenades. A 1mm web line might have a breaking strain of 1,000N per strand, which would be difficult (though possible) for a human to break, and a 0.5 liter bottle could produce 500 meters of thread like that; for a 1.8 meter area, that's a net with a separation of 10-20mm. For a layer of glue or slime, 1.8 meters is 2.5 square meters, and 0.5 liters will give you a 0.2mm layer.

[jeff_wilson]

Originally Posted by Anthony

You might have better luck with web, glue, or slime grenades. A 1mm web line might have a breaking strain of 1,000N per strand, which would be difficult (though possible) for a human to break, and a 0.5 liter bottle could produce 500 meters of thread like that; for a 1.8 meter area, that's a net with a separation of 10-20mm. For a layer of glue or slime, 1.8 meters is 2.5 square meters, and 0.5 liters will give you a 0.2mm layer.

How opaque could this be made to appear, if only to discourage aimed shots through it?

[Anthony]

Originally Posted by jeff_wilson

How opaque could this be made to appear, if only to discourage aimed shots through it?

Mix it with a tinsel grenade? Or a silly strings grenade? It's probably practical to make it at least difficult to see through, though hard to avoid having holes.

[Andrew Hackard]

Moved from Geek Culture to the GURPS forum since the post refers to specific game mechanics.

[Nereidalbel]

How fast does modern spray foam in a can set, and just what kind of volume can that fill? I'd imagine it would at least slow somebody down if TL9/10 could expand more and/or set faster.

[Refplace]

I read but dont recall where, Heinlen maybe? Use of web grenades which seem reasonable. For blocking makr the expansion gas opaque and with glitter or something to stick to the threads it seems doable for a few seconds.

[namada]

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[Gedrin]

One possibility is a binary compound that reacts with the existing materials present, mostly oxygen and nitrogen. The compound would rob the area of those materials, possibly creating a bit of a vacuum, drawing more in. Most of these types of reactions tend to violate the conditions of calling something "non-lethal" when they occur at any sort of swift speed. However, you've got TL10 chemistry to work with, so however magical aerogels and superconductors would seem to a guy in the 40's...go with that much magic science.

Another option is rapid nanites. Deploy the wire, but it's coated with nanites that rapidly use surrounding materials to construct vanes or other structures to block view. These would prevent sight, but not anything forceful...unless they're super strong somehow and super thin materials can stop bullets in your world.


Option three, it just works. You don't actually need to invent the thing, just define the type of object, the effect, and some general rules for use. "It blocks up to X hexes, using a chemical compound, taking Y seconds to set, and is a material with DR/HP, Foam-A-Way removes it but is a high LC to purchase, a commonly sold hair care product will also do the job providing you have six liters of the stuff."

[Nymdok]

For tech 8 or 9 I think Id go with something like an inflatable raft with adhesive around the outside. Id guess about the size of a 2 liter coke bottle before deployed.

Your plausability may vary, buts gadgeteerable :)

Nymdok