Randall Munro, who draws the geeky and very funny xkcd comic strip has recently taken up the mantle of Internet Science Answer Man. As suits his strip, though, he doesn’t’ take on the usual questions like “Why is the sky blue?” or “Will I die if I eat 200 marshamllows? Asking for a friend *burp*”. No, he takes on the truly important questions like “Can I do that thing Yosemite Sam does where he shoots his guns into the floor and flies up into the air, but bigger?”
The answer, you’ll be pleased to know, is “yes”. The hitch is — and since this is science, there’s always a hitch because you can’t get anything cool out of science without one, like flying monkeys who by dint of their blasphemous mutations also have a taste for human flesh — you need a really big gun, or one that fires ridiculously fast, to get off the ground for very long.
Fortunately for us, such guns do exist.
The GAU-8 Avenger fires up to sixty one-pound bullets a second. It produces almost five tons of recoil force, which is crazy considering that it’s mounted in a type of plane (the A-10 “Warthog”) whose two engines produce only four tons of thrust each. If you put two of them in one aircraft, and fired both guns forward while opening up the throttle, the guns would win and you’d accelerate backward.
To put it another way: If I mounted a GAU-8 on my car, put the car in neutral, and started firing backward from a standstill, I would be breaking the interstate speed limit in less than three seconds.
As good as this gun would be as a rocket pack engine, the Russians built one that would work even better. The Gryazev-Shipunov GSh-6-30 weighs half as much as the GAU-8 and has an even higher fire rate. Its thrust-to-weight ratio approaches 40, which means if you pointed one at the ground and fired, not only would it take off in a rapidly expanding spray of deadly metal fragments, but you would experience 40 gees of acceleration.
In your face, Bob Costas, you sanctimonious little garden gnome! Guns do have a real benefit!