Shape of things to comeUsing a giant light-gas gun to blast object into space

When Jules Verne, in the nineteenth century, wrote in about a gigantic gun that could be used to launch people into space, no one expected it to become a reality. Now physicist John Hunter has outlined the design of such a gun that he says could slash the cost of putting cargo into orbit.

David Shiga writes that the gun is based on a smaller device Hunter helped to build in the 1990s while at the Lawrence Livermore National Laboratory (LLNL) in California. With a barrel 47 meters long, it used compressed hydrogen gas to fire projectiles weighing a few kilograms at speeds of up to 3 kilometers per second.

Now Hunter and two other ex-LLNL scientists have set up a company called Quicklaunch, based in San Diego, California, to create a more powerful version of the gun. At the Space Investment Summit in Boston last week, Hunter described a design for a 1.1-kilometer-long gun that he says could launch 450-kilogram payloads at six kilometers per second. A small rocket engine would then boost the projectile into low-Earth orbit.

Huge g-forces
Humans would clearly be killed and conventional satellites crushed by the gun’s huge g-forces, but it could lift robust payloads such as rocket fuel. Finding cheap ways to transport fuel into space will lower the cost of keeping the International Space Station in orbit, and in future it may be needed to supply a crewed mission to Mars.

Shiga writes that the gun would cost $500 million to build, but Hunter says that individual launch costs would be lower than current methods. “We think it’s at least a factor of 10 cheaper than anything else,” he says.

Franklin Chang-Diaz, a former astronaut and physicist at the Ad Astra Rocket Company based in Webster, Texas, says a launch gun might make more sense on the moon, where there is no atmosphere. “You don’t have to worry about drag or heating or anything like that,” he says.

Welder’s torch
Hunter acknowledges that the projectile would be slowed by its passage through Earth’s atmosphere. He says, though, that the drag would be minimal on a pointy-nosed projectile, causing it to slow by only half a kilometer per second. He also admits that the heat generated by the high-speed passage through the atmosphere is “like a welder’s torch.” It would, however, be relatively short-lived, he says, with the projectile clearing the atmosphere in less than 100 seconds. Designing the projectile so that it could survive having some layers of its outer skin burned off would get around this problem, Hunter says. 

Gerald Bull
Hunter’s long-gun design brings to mind an intriguing episode from the past. On 22 March 1992, Israeli agents killed Gerald Bull outside his apartment in Brussels, Belgium. Bull, a Canadian engineer, was helping the Iraqis develop a long-range gun capable of firing projectiles a long distance with great accuracy. His Extended Range, Full Bore [ERFB] GC-45 could routinely place rounds into 10 meter circles at ranges up to 30 km, extending this to 38 km with but little loss in accuracy. This was just the beginning. Bull became convinced that a gun could launch objects into space — and do so more cheaply than missiles. He designed a 45 meters, 350 mm caliber gun for testing purposes, and then started work on the “real” machine — a gun that was 150 meters long, weighed 2,100 tons, with a bore of one meter (39 inches). It was to be capable of placing a 2,000 kilogram projectile into orbit. The Iraqis told Bull they would finance his gun project only if he would also help with development of their longer ranged Scud-based missile project. Bull agreed. The Israelis were afraid that the Iraqis would use the long-range weapons Bull was designing to launch chemical or biological weapons at Israel. Several attempts to persuade Bull to cease and desist proved futile, and Mossad agents killed him. Bull, by the way, had a colorful career: His efforts on behalf of the U.S. military in the 1970s earned him a U.S. citizenship. The end of the Vietnam war saw funding for his projects dwindle, and he turned more and more to rogue countries such as Iraq, South Africa, and North Korea for financial support.