Lunar Landing Training Vehicle (LLTV)
• 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
• Main Engine: LLRV-General Electric CF700-2V turbojet
Probably one of the most unusual vehicles ever flown by Gen. 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, and has been covered in many books and articles. But how to actually land on the moon posed many challenges that have often been overlooked. Should the landing 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. And pilots needed to develop 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), building 2 prototypes. Lift was provided by a GE turbojet mounted vertically in the center, and 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). 3 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.
Of course, a drawback to this system was there was little margin 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, 1 was cannibalized for parts and 3 were lost in accidents. First man on the moon Neil Armstrong narrowly escaped an LLRV on 6 May 1968, when he lost power to the maneuvering rockets and the vehicle went out of control and had to eject.
Flying the LLRV/LLTV was a case study of rewards outweighing the risks. The vehicle could carry a maximum of 9 minutes of fuel, and most mission profiles usually lasted only 2 minutes with climbs to over 1,000’ during those 2 minutes.
After starting the engine the pilot would then climb to altitude, usually around 1,000’. He would then engage the autothrottle 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. While an extremely demanding vehicle to fly, he enjoyed the challenge of flying the LLTV.
Other astronauts such as Apollo 12 Commander Pete Conrad have commented, “(NASA Administrator) Dr. Gilruth, bless his soul, just worried to death that somebody was going to get bagged in an LLTV. And so, he asked everybody when they came back (from the Moon) ‘Do you think it’s necessary to fly the LLTV?’ And, the feeling that I think Neil had and myself – and I’m quite sure the rest of the guys – was ‘Yes, you really should go ahead and fly the LLTV.’ But, having had the three accidents and having that one vehicle left, Dr. Gilruth asked the guys to figure out how many flights we got on a vehicle before we crumped one. And it turned out to be like 260 flights or something like that. To finish the training after the third accident, they had to fly 240 more flights; and, so, when Gene (Cernan, the Apollo 17 Commander) flew the last flight in his training, the thing went to the Smithsonian or whatever because nobody was ever going to fly that thing again as far as Gilruth was concerned. And he almost didn’t authorize the training, see. And so, at least the early guys pushed very hard for everybody to continue flying it.”
The surviving LLTV is now at the NASA’s Johnson Space Center in Houston, TX.
Thanks to HFM Volunteer Steve Kessinger for researching and writing this material.