The Super Soaker
As we saw in the last two sections, the main problem with conventional water guns is that they don't produce a very powerful stream. This is because the water pressure must be generated with each shot, either by the shooter or by a motorized system. It's not feasible to produce a high-pressure stream because it would mean applying a great deal of force in a short amount of time.
In 1982, a nuclear scientist named Lonnie Johnson came up with an ingenious solution to this problem. In his spare time, he was working on a new heat-pump system that would use moving water to regulate temperature. Late one night, he attached a model of the pumping mechanism to the bathroom sink, and was startled by the powerful water blast that shot across the room. In that instant, he was struck by the idea for a water gun that would use compressed air to provide pressure for a water blast.
To make his idea a reality, Johnson enlisted the help of an accomplished inventor named Bruce D'Andrade. Together, D'Andrade and Johnson came up with the basic design that would become the Super Soaker.
Super Soakers are built around a pump mechanism, but moving the pump doesn't actually drive water out of the gun; it serves to build up water pressure before the blast. In the first wave of Super Soakers, you built up this pressure by pumping air directly into a single water reservoir. As you pumped in more air, it became more and more compressed and so applied greater pressure to the water inside.
In later models, you built pressure by pumping water instead of air. In the diagram below, you can see how the pieces of this sort of gun fit together.
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Unlike its predecessors, this gun has two water reservoirs (labeled A and B), which are connected together via a network of tubes. To load the gun, you fill the larger reservoir (A) with water. To prime the gun for a blast, you pull the pump handle (C) in and out several times. The pump handle is connected to a long, narrow piston (D), which moves back and forth inside a cylinder (E). This pump is similar to the one in a squirt-gun pistol, and it relies on the same one-way-valve system to control the direction of water flow. The first valve (F) is positioned between the large water reservoir and the pump mechanism, and the second valve (G) is positioned between the pump and the smaller water reservoir, which feeds into the barrel of the gun (H).
On the upstroke of the pump cycle, when you pull the pump handle out, the receding piston pulls in water from the large reservoir above. The second one-way valve (G) keeps water from flowing up from the smaller reservoir (B). On the downstroke of the pump cycle, when you push the pump handle in, the plunging piston drives the water out of the cylinder, through the second one-way valve (G) and into the small reservoir (B). The first one-way valve (F) keeps the pressurized water from flowing back up into the large reservoir (A).
But what is all this accomplishing? In the next section, we'll put the pieces together to see how the Super Soaker builds such a powerful blast.