XCOR EZ-Rocket

The XCOR EZ-Rocket was a test platform for the XCOR XR-4A3 rocket propulsion system. The airplane was a modified Rutan Long-EZ, with the propeller replaced by first one, then later a pair of pressure-fed regeneratively cooled liquid-fueled rocket engines and an underslung fuel tank. The engines were restartable in flight, and were contained within Kevlar armor shielding. The EZ-Rocket was registered as an experimental aircraft.

EZ-Rocket one week after its first flight
Cockpit. Engine on-off switches on left side panel are placarded "FWD - LOUD; BACK - QUIET"

Development and history

The first flight took place on July 21, 2001, flown by test pilot Dick Rutan.[1]

On a typical flight, the EZ-Rocket took off on rockets, gained altitude for a minute or so, then switched off the rockets and glided to a dead stick landing.

The vehicle actually flew better during dead stick landings than a standard Long-EZ due to lack of drag from a stationary pusher propeller — the vehicle's aerodynamics were cleaner in spite of its belly tank. It was also lighter due to the lack of a piston engine (the rocket propulsion system was significantly lighter), so enjoyed significantly lower wing loading than a standard Long-EZ.

When XCOR began flying its EZ-Rocket in 2001, the company decided to have it FAA certified as an experimental aircraft, avoiding the additional time required to seek a launch vehicle license from the Office of Commercial Space Transportation (AST). Jeff Greason, a co-founder of XCOR, said on February 10, 2003 if they were starting out at that time they probably would seek an AST license due to the progress made in developing a regulatory regime for suborbitals.[2]

Milestones and records
EZ-Rocket, flown by Dick Rutan, touches down at California City, California on December 3, 2005, setting a point-to-point distance record for rocket-powered, ground-launched aircraft.
  • October 8, 2000 - First firing of an XCOR Aerospace LOX-powered rocket engine.[3]
  • July 21, 2001 - First flight, flown by Dick Rutan (single-engine configuration).[3]
  • October 3, 2001 - First flight in twin-engine configuration.[3]
  • January 24, 2002 - First rocketplane inflight engine relight. Piloted by Mike Melvill.
  • June 24, 2002 - First touch-and-go of a rocket-powered aircraft (world record).[3]
  • Jul 11, 2002 - EZ-Rocket flies twice in one day. First same day rocketplane flights since 1945.
  • July 25, 2002 - EZ-Rocket first Oshkosh flight at the 2002 EAA AirVenture Oshkosh air show. First rocketplane air show flight in the United States.
  • July 27, 2002 - EZ-Rocket second Oshkosh flight at the 2002 EAA AirVenture Oshkosh air show. Second rocketplane air show flight in the United States.
  • August 26, 2005 - EZ-Rocket requalification flight after three-year retirement. Piloted by Dick Rutan.
  • August 29, 2005 - Searfoss qualification flight.
  • September 1, 2005 - Altitude validation flight to 11,546 feet. Aircraft demonstrated sufficient range to fly from Mojave to California City and back without a relight, a prerequisite for the world record flight.
  • October 9, 2005 - EZ-Rocket second and third Las Cruces flights, at Countdown to X PRIZE Cup. Third and fourth rocketplane air show flights in the United States.
  • December 3, 2005 - Set the point-to-point distance record for a ground-launched, rocket-powered aircraft, flying 16 km from Mojave to California City in just under ten minutes, piloted by Dick Rutan.[4][5] Also first official delivery of U.S. Mail by a rocket-powered aircraft.[4] In recognition of this achievement, the FAI awarded Rutan the 2005 Louis Blériot Medal.[6]
  • December 15, 2005 - First cross-country return flight of a rocket-powered aircraft in the United States, return flight from California City, piloted by Rick Searfoss.[4]

Derivatives

The Rocket Racing League aircraft currently in development, the Mark-III X-racer, is a design descendant of the EZ-Rocket aircraft. Although XCOR is not the developer of the rocket engine for the Mark-III, XCOR did develop the rocket engine for the Mark-I X-Racer, the first of the X-Racers to use a single rocket engine on a Velocity SE basic airframe, and the first X-Racer to utilize kerosene instead of isopropyl alcohol fuel. XCOR used both design and operational experience from the EZ-Rocket in the Mark-I rocket aircraft design.

Specifications
Twin rocket engines
Dick Rutan standing next to the engines of the EZ-Rocket, after the official rollout flight, November 12, 2001
  • Two XR-4A3 400 lbf (1.8 kN) thrust rocket engines (non throttleable, restartable in flight)[7]
  • 20 sec 500 m takeoff roll
  • Vne = 200 kn (370 km/h)
  • climb rate = 52 m/s (10,000 ft/min)
  • maximum altitude = 11,546 ft (3,519 m) MSL
  • Fuel: isopropyl alcohol and liquid oxygen
  • Chamber pressure: ~ 350 psi (2.4 MPa)
  • Specific impulse: 250 seconds (2.5 km/s) to 270 seconds (2.6 km/s)
  • Noise: 128 dB at 10 meters[8]

See also

References
  1. Flight Tests Of XCOR’s EZ-Rocket and Progress Toward a Microgravity and Microspacecraft Launcher
  2. "Reusable Launch Vehicle (RLV) News". HobbySpace. Retrieved 2022-05-02.
  3. "First Flights - XCOR Aerospace". Mojave Virtual Museum. Archived from the original on 2006-11-10. Retrieved 2006-11-13.
  4. Deaver, Bill (2005-12-22). "XCOR EZ-Rocket makes more history at CalCity". Mojave Desert News.
  5. FAI Records Archived March 10, 2007, at the Wayback Machine
  6. List of Blériot medals awarded to Dick Rutan
  7. "LOX-Alcohol Rocket Engine". www.xcor.com. XCOR Aerospace, Inc. Archived from the original on 2015-06-26. Retrieved 2015-06-15.
  8. "XCOR Aerospace: EZ-Rocket FAQ". Archived from the original on February 20, 2009. Retrieved January 29, 2009.
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