EZ-Rocket Frequently Asked Questions List
1. What is the EZ-Rocket
The EZ-Rocket is a modified Long-EZ homebuilt aircraft. The aircraft is powered by twin 400 lb thrust regeneratively cooled rocket engines and fueled by isopropyl alcohol and liquid oxygen. The EZ-Rocket includes an external composite fuel tank and an insulated internal aluminum liquid oxygen tank. The modifiecations were performed at XCOR Aerospace's Mojave, CA shop. Tests are performed at the Mojave Civilian Flight Test Center.
2. Who is your test pilot?Retired United States Air Force Lieutenant Colonel Dick Rutan is under contract to fly the EZ-Rocket. He has lots of experience in this type of airplane. None of the operating limitations of a standard Long-EZ are exceeded in this airplane, although a steep climb is needed to keep from exceeding Vne with both engines running. Recently, our chase plane pilot Mike Melville also flew the EZ-Rocket. His first words after shutting the engines down were "That was a real kick in the pants!"
3. What is the performance?
With both engines running (800 lb thrust total) and maximum propellant load, takeoff roll is 500m (1650 ft) for 20 seconds. After pulling up, climb is established at constant airspeed at Vne, or 195 knots. Burnout is after a maximum of two minutes, still at 195 knots indicated, which equals Mach 0.4. The maximum altitude that can be attained is 1.91 miles (10,000 ft). The maximum climb rate is 52 m/sec (10,000 ft/min). It is likely we will never take the plane to the maximum altitude capability. The engines are quite capable of overspeeding the airframe, a steep climb must be maintained to prevent this.
4. How many times have you flown?
The EZ-Rocket has flown 15 times under rocket power.
The Airframe also has 500 hours on it under piston power.
5. What are the safety features of this airplane and its rocket propulsion system?
The airplane flies just like any other Long-EZ. The pilot does not need to learn to fly the plane at the same time as controlling the rocket propulsion systems. Single engine performance is similar to a Lycoming O-320 with constant speed prop.
There is an ultraviolet fire sensor in the engine bay that illuminates a light on the instrument panel in the event of a fire. We tested it. It works really well.
Large bottles of helium can be dumped into the engine bay by pilot command (the guarded "FIRE" switch on the upper panel) for fire suppression. These helium bottles hold several times the inert gas that a fire extinguisher bottle would.
Each engine has its own dedicated electrical system and controller. They can be independently started and stopped. The plane climbs well on a single engine.
Each engine has its own kevlar blast shield. Each engine has a chamber pressure gauge that lets the pilot monitor combustion health. Each engine has a burn-through sensor connected to a red light on the panel.
The pilot can depressurize either or both propellant tanks in flight. This vents helium outside the airplane.
The pilot can dump the LOX through a manual valve into the atmosphere. Venting oxygen behind a 200 MPH glider is not hazerdous. We've done this during a safe-abort flight.
Most rocket engine explosions happen because of what is known as a hard start. This happens when main propellants collect in the combusion chamber and are belatedly ignited. We prevent this by interlocking the main valves with an igniter operation sensor. The only time an XCOR engines comes apart is when we put our wrenches on it.
Main propellant valves are mechanically linked together, preventing incorrect valve timing.
The pilot has a parachute and the canopy is quick to open.
If an engine fails to shut down, or a fire is detected, the pilot has a manually operated valve pair that shuts off both propellants to both engines. We've used this feature successfully in a safe-abort flight.