I had the same thought. But mine is for a mortar. I was thinking about a tank of air, with a chamber just above it. With two ball valves. Open the lower to charge the chamber, close. Then open the upperball valve to shoot the rocket. Nerf mini footballs. Havent thought alot about it. you might get a dozen shots off, wwith out having to change the main tank. It would work kind of like a M203, but having a tank hooked up to the grenade.