How the EZ-Rocket Works

How It Works
The EZ-Rocket on takeoff
The EZ-Rocket on takeoff
Photo courtesy XCOR Aerospace

When the pilot (usually Bert Rutan's brother, Dick) starts up the EZ-Rocket, alcohol flows under pressure from the fuel tank into the rocket engine. A piston pump pumps the liquid oxygen into the engine. XCOR had to design a unique pump because turbopumps used in other rocket engines are too large. Then an electrical igniter sparks the fuel and oxidizer. Combustion begins. and the hot gases leave the rocket nozzle out the back, generating the thrust. With both engines running (generating 800 pounds of thrust), it takes 20 seconds and 1650 feet (500 meters) of runway to take off.

The EZ-Rocket takes off, flies, and lands like a conventional airplane, with some exceptions:

  • The rocket engine burns for about two minutes to reach 195 knots (Mach 0.4). Conventional aircraft of the same size and type (Long-EZ) cannot reach these speeds -- only jet aircraft can.
  • The rocket plane climbs at 10,000 feet per minute (52 meters per second).
  • It can reach a maximum altitude of nearly two miles (10,000 feet, or about 3 kilometers).
  • During the flight, the pilot can turn the rocket motor on and off to make adjustments, such as lining up on the runway for landing.
  • When the fuel is exhausted, the rocket plane glides to a landing on the runway. Most planes land under power.

In one test, the pilot performed a a touch-and-go maneuver -- he touched down on the runway without power, rolled several hundred feet, re-ignited the rocket engine and took off again. The EZ-Rocket has successfully performed 15 flights and a number of tests, including touch-and-go maneuvers and an in-flight abort maneuver. It has also demonstrated its abilities at air shows, including the 2005 X-Cup Rocket Racing Exposition in New Mexico.

A test-fire of the EZ-Rocket's LOX/alcohol engine. The series of rings in the plume are shock diamonds, or Mach disks, which occur when the exhaust plume's pressure is lower than atmospheric pressure.
Photo courtesy XCOR Aerospace

While the EZ-Rocket was built onto the Long-EZ airframe, it was never intended for personal use -- only as a test bed for new technologies. But like any aircraft or spacecraft, there must be safety features built in to meet the most frequent emergency needs such as a fire in the engine or engine failure. The EZ-Rocket has an ultraviolet fire sensor in the engine bay wired to the instrument panel, which alerts the pilot to any fire in the engine. Two large bottles of pressurized helium in the bay are used as fire extinguishers when the pilot throws a switch on the instrument panel. Each engine has its own control systems and can be turned on and off independently (the EZ-Rocket can climb on one engine). Each engine also has a blast shield made of Kevlar and a burn-through sensor that signals the pilot when the fuel is gone.

If necessary, the pilot can depressurize both fuel tanks and vent the alcohol and/or the liquid oxygen into the atmosphere. He can also shut off fuel to both engines if there is a fire or one engine fails to shut down. The main valves and igniter are linked to prevent gases from collecting in the combustion chamber and igniting inadvertently, and the propellant valves are linked together to coordinate valve timing. The canopy can open quickly and the pilot has a parachute in the event he has to exit the EZ-Rocket.

XCOR successfully tested many of these safety features in the in-flight abort maneuver. Now the company is building on the success of the EZ-Rocket with two new projects. We'll learn about these in the next section.