Lunar Landing Training Vehicle (LLTV)

NASA photo: Lunar Landing Research Vehicle (LLRV) with Bell 47 Helicopter providing chase supportTechnical Specs

  • Lift Rockets: Hydrogen peroxide
  • Attitude Control Thrusters: Hydrogen peroxide
  • Length: 22.5 ft.
  • Width: 15 ft.
  • Height w/ footpads and struts: 10 ft.
  • Tread: 13.3 ft.
  • Maximum Takeoff Weight: 3,702 lbs.
  • Useful Load: 1,192 lbs

Engine

  • Main Engine: LLRV-General Electric CF700-2V turbojet

Probably one of the most unusual vehicles ever flown by William Anders was the Lunar Landing Training Vehicle, aka “The Flying Bedstead”. This odd-looking craft was one of the most remarkable flying machines ever designed, and one of the most essential training devices used in the Apollo Program.

Getting to the moon was one thing, but how to actually land on the moon posed many challenges that have often been overlooked. Should the landing be done horizontally like an airplane, or vertically like in a helicopter? Since there was no atmosphere to provide air pressure to conventional aircraft instruments, engineers needed to invent devices to acquire altitude, speed, and rate of descent data, and instruments to present it to the pilot. The pilots needed methods to interpret this information to make reliable, safe landings. In other words, they needed to invent an entirely new way to fly!!

In late 1961, in collaboration with Bell Aircraft (builders of the X-1 and other research aircraft), engineers at NASA’s Flight Research Center at Edwards Air Force Base began work on a flying vehicle that would allow these problems to be investigated and solved.

Bell designed a vehicle called the Lunar Landing Research Vehicle (LLRV) and built two prototypes. Lift was provided by a GE turbojet mounted vertically in the center, while pitch, roll and yaw control were provided by reaction control rockets similar to those on the X-15. This provided six degrees of movement, exactly what the pilot would encounter during a lunar landing.

On 30 October 1964, NASA pilot Joe Walker made the first LLRV flight. After some 200+ successful flights in 1967, the design was upgraded, becoming the Lunar Landing Training Vehicle (LLTV).  Three LLTVs were built.

Without wings or conventional aerodynamic control surfaces, the vehicles had no aerodynamic way to stabilize themselves like normal aircraft. Instead, an autopilot was designed that used the  hydrogen peroxide maneuvering rockets for primary vehicle stabilization, just like the Lunar Module did.

Using this analog computer system to control an unstable aircraft was the first “fly-by-wire” flight control system, which eventually led to modern digital fly-by-wire aircraft such as the F-16 fighter, and the Boeing 777 jetliner.

There was little margin of error for failure of  the vehicle’s systems, or if a pilot exceeded performance or control parameters.  Out of the 2 LLRVs and 3 LLTVs built, one was cannibalized for parts and three were lost in accidents. Neil Armstrong narrowly escaped an LLRV on 6 May 1968, when he lost power to the maneuvering rockets, the vehicle went out of control and he had to eject.

Flying the LLRV/LLTV was a case study in rewards outweighing the risks. The vehicle could carry a maximum of nine minutes of fuel, and most mission profiles usually lasted only two minutes with climbs to over 1,000 feet.

After starting the engine, the pilot would climb to altitude, usually around 1,000’. He would then engage the auto throttle to use the turbojet to support 5/6 of the vehicle’s weight, and begin his simulated lunar landing profile. The remaining 1/6 was supported by hydrogen peroxide lift rockets, which the pilot used to control his rate of descent to the simulated lunar surface.

General Anders was one of the first two astronauts (along with Neil Armstrong) qualified to fly the LLTV. Despite the demanding nature of the flight, he enjoyed the challenge.

The surviving LLTV is at NASA’s Johnson Space Center in Houston, TX. and the surviving LLRV is on display at the Air Force Flight Test Museum.

Links

Check out the NASA Images site for historic photos  [Click Here]

Credits

Thanks to HFM Volunteer Steve Kessinger for researching & writing this material.