The Biggest Bang

Jim Livingston happens to have a summer cottage on Lake Conesus, N.Y., a stone’s throw from this year’s launch site, and it is here that he and Whitmore prepare the motor for Livingston’s 14-foot-tall Viper rocket. On this sultry summer afternoon, Whitmore is inspecting his high-test home brew. “When I’m sweating like this,” he tells me, “I don’t know whether it’s because I’m exerting myself so much or I’m just excited being around this much propellant.” Before he slides the sleeve of propellant packets into an aluminum casing that will slip into place inside the rocket body just above the fins, he permits himself a final deep whiff. “Oh, yeah!” he exclaims. “This is one of the most beautiful smells in the world.”

A rocket is basically fuel ignited in a contained space with only one way out. The rapidly expanding gases and flaming particulate matter push against the walls of the combustion chamber and are forced through a narrow nozzle that concentrates their energy as forward thrust. Rocket guru Wernher von Braun once likened the process to continuously firing a machine gun off the stern of a rowboat, pushing the boat forward with the force of the recoil. The simplicity of the mechanism, and the lack of moving parts in the finished product, go a long way toward explaining how it is possible to assemble a sizable rocket motor in a summer cottage.

Whitmore prepares to secure his motor inside the rocket booster stage. He fits a steel compression, or snap, ring into two retention bolts, so that at liftoff the motor won’t push through the forward bulkhead or shoot out the nozzle underneath. “When you see me begin to compress the snap ring,” he says, “step slightly this way or that. If these things slip off the groove, you have a bullet in the house.”

Obeying the first law of high-powered rocketry—“Big is good”—Whitmore has built a motor that, in the nomenclature of the hobby, is N class, meaning that over the course of its burn it will put out between 10,240 and 20,480 Newton-
seconds of thrust, the so-called “total impulse.” (A Newton-
second is the force applied over one second that would accelerate one kilogram of mass an additional meter per second.) Every time you go up a letter, you double the total impulse, so this N motor has twice the power of Whitmore’s recent M motor projects—M being the standard attention-grabbing muscle motor at an LDRS event—and 8,192 times the power of the A motors that drive the small model kits. “Working with these big motors really gets your heart rate up,” he says.