OK, another of my general ideas has been kicking around and I’ve not done anything with it. Today, thanks to the explosions in Boston, is likely a reasonable time to “set it free”.
There are “water barriers” that folks might have seen in use. Some are like the concrete barriers that keep cars from crossing to the wrong side of a freeway. Others more like things that keep people away from cars (and have openings in them).
In London, during the IRA bombing years, there were so many bombs in trash cans that a ‘bomb resistant trash can’ was developed.
My idea is a simple one. Make a “water barrier” where the plastic “container” is a fiber reenforced material. Basically, a Kevlar / Aramid like layer thick enough to stop / slow projectiles, that can then be filled with a load of water (that further stops / slows projectiles, but also absorbs and redirects explosive forces.)
There are pictures of some water barriers here:
They even have an “organization”:
Generally speaking, they are used for their very light weight and ease of set up / moving. Then the water is added for mass sufficient to slow / stop vehicles and such. My idea simply extends that to include explosive forces and projectiles.
So instead of a cheap thermoplastic surface, one that is more complex, and strong. Either with embedded reinforcing materials (such as fiberglass or if it works in such constructions, Kevlar) or with a ‘drape’ of Kevlar fabric (on the outer surfaces or in a protected ‘pocket’ inside). In this way, any projectile materials are contained inside the barrier. Also, explosive forces will tend to be redirected up the slope of the walls. The ability of an explosion to do damage to people is strongly reduced when the force is redirected upward toward the sky. Finally, to the extent the barrier is breached, the water spray generated tends to absorb and dissipate the explosive forces. The amount of energy water can absorb is quite high.
So, for example, a trash can made with an inner and outer shell with Kevlar layers, then filled with 4 inches of water, will resist a rather large explosive force and redirect most of that upward though the unrestrained lid. To the extent it gets broken up and sent flying, Kevlar “fluff” and water spray has very high air drag and will rapidly slow below damaging levels.
For “events” like the Boston Marathon, one can set up a line of the “car barrier” kind of these and simply require than any packages, backpacks, bags, trashcans, etc. be behind the barrier. So an 8 foot wide sidewalk viewing area could have 3 feet along the building facade where bags could be placed behind such a barrier, and 5 feet for folks to line up along the street. (As you can’t see much from more than 5 feet back, no big loss ;-)
Now any ‘left package’ can have very limited scope of action. It is either on a person in transit (so they go with it), or behind an energy absorbing barrier where damage is very limited.
At the end of the event, plugs are removed from the barriers and water drains. Now they are “mostly empty” light weight plastic structures that are easily moved and stored. These same barriers can be used for non-threat circumstances (where the Kevlar layers make them a bit heavier, but otherwise the same) and some could be designed such that the ‘drape’ forms could be deployed without Kevlar. (Those with heavier embedded materials will stay heavier).
So that’s the basic idea. Water barriers with a design goal of projectile suppression, explosive force absorption, and force redirection. As long as the top of the ‘package’ area is open, they ought to work rather well. Buildings that are used to fabricate explosives and fireworks have strong walls, but ‘blow off roofs’ for exactly this function. To redirect the forces upward and prevent damage to nearby structures or people. This just makes it all smaller, and lets it be “built on site” with water fill.
If anyone makes these, a footnote of recognition would be appreciated.
Sidebar On Origin
I’d originally conceived of these as a way to give “portable bomb disposal” rigs. A normal bomb disposal trailer has a very large very heavy “tank” on it, where an explosive device can be put inside. My original idea was to make a large Kevlar Ring that could be packed in a patrol car trunk. Then any officer who “sees something suspicious” could just set the ring around it, and hook up the hose to the nearest faucet. (one of those hoses that ‘inflates’ to be included – the ones with a thin rubber liner and fabric shell – along with both a regular hose end and a ‘clamp on’ for bathroom faucets).
I still that has merit too. It would redirect most minor explosions upwards and contain the small debris from most “quart sized devices”. I’d guessed that about a 1 foot thick bag of water would be enough for most things (inside a Kevlar skin…)
A more “stowable” but less effective unit would include an “inflation canister” of Urethane Foam (or similar foam). That way it is just “set the ring around the package, pull the release, and walk away”. It lacks the mass and evaporation heat absorption abilities, but will still do a fair amount of force redirection and projectile trapping. “Beats nothing” by a long shot. Very fast to deploy, and not a lot of ‘time near what goes boom’ for folks not in bomb suits. Frankly, were I an officer in a car, I’d want a Kevlar donut with pull tab I could just put over something and walk away. Makes standing 40 feet from it hollering at folks to “Stay Back” a bit more comfortable… where shrapnel from an unblocked device is ‘line of sight’ for a very long ways…
It would benefit from testing and sizing on a test range.
For high risk areas or where faucets are rare, a 10 gallon or 15 gallon tank of water in the trunk, or even a 20 or 30 gallon canister on a roof rack, becomes an easy and cheap “small town” bomb disposal unit.
So that’s the idea. Hopefully it is helpful to someone. If anyone wants to “hire the inventor” to make it happen, just let me know… There are a few other enhancements I’ve thought of that are a bit complex to put in a posting. (A simple one is a ‘pull tab’ of contact adhesive on the bottom so it ‘stays put’ in wind while inflating and is harder to be pushed out of position by an asymmetrical force. Can also be applied to things on walls then too…)