Lunar Landing Research Vehicle
Encyclopedia
The Bell Aerosystems Lunar Landing Research Vehicle (LLRV) was an Apollo Project era program to build a simulator for the Moon landings. The LLRVs, humorously referred to as "flying bedsteads"
, were used by the FRC, now known as the NASA Dryden Flight Research Center
, at Edwards Air Force Base
, California, to study and analyze piloting techniques needed to fly and land the Apollo Lunar Module
in the moon's low gravity environment.
The research vehicles were vertical take-off vehicles that used a single jet engine mounted on a gimbal
so that it always pointed vertically. It was adjusted to cancel 5/6 of the vehicle's weight, and the vehicle used hydrogen peroxide rockets which could fairly accurately simulate the behaviour of a lunar lander.
Success of the two LLRVs led to the building of three Lunar Landing Training Vehicles (LLTVs) used by Apollo astronauts at the Manned Spacecraft Center in Houston, Texas, predecessor of NASA's Johnson Space Center. Nearly all of the flying bedsteads were destroyed in crashes, but the purpose built rocket ejection seat system recovered the pilot safely in all cases.
The final phase of every Apollo landing was manually piloted by the mission commander. Because of navigational problems, Neil Armstrong
, Apollo 11
commander, said his mission would not have been successful without extensive training on the LLRVs and LLTVs.
es, the vehicles were powered by a General Electric CF700-2V
turbofan engine with a thrust
of 4,200 lbf (19 kN), mounted vertically in a gimbal
. The engine lifted the vehicle to the test altitude and was then throttled back to support five-sixths of the vehicle's weight, simulating the reduced gravity of the moon. Two hydrogen peroxide
lift rocket
s with thrust that could be varied from 100 to 500 lbf (440 to 2,200 N) handled the vehicle's rate of descent and horizontal movement. Sixteen smaller hydrogen peroxide thrusters, mounted in pairs, gave the pilot control in pitch, yaw and roll. As safety backups, six 500 lbf (2,200 N) thrust rockets could take over the lift function and stabilize the craft for a moment if the jet engine failed. The pilot had an ejection seat for safety. Manufactured by Weber Aircraft LLC
, it was one of the first zero-zero ejection seats, capable of saving the operator even if the aircraft was stationary on the ground - a necessity given the LLRV's low and slow flight envelope.
After conceptual planning and meetings with engineers from Bell Aerosystems, Buffalo, New York, a company with experience in vertical takeoff and landing (VTOL
) aircraft, NASA issued Bell a $50,000 study contract in December 1961. Bell had independently conceived a similar, free-flying simulator, and out of this study came the NASA Headquarters' endorsement of the LLRV concept, resulting in a $3.6 million production contract awarded to Bell on February 1, 1963, for delivery of the first of two vehicles for flight studies at the FRC within 14 months.
The two LLRVs were shipped from Bell to the FRC in April 1964, with program emphasis on vehicle No. 1. It was first readied for captured flight on a tilt table constructed at the FRC to test the engines without actually flying. The scene then shifted to the old South Base area of Edwards. On the day of the first flight, 30 October, 1964, research pilot Joe Walker
flew it three times for a total of just under 60 seconds to a peak altitude of ten feet (3 m). Later flights were shared between Walker; another Dryden pilot, Don Mallick; the Army's Jack Kluever; and NASA Manned Spacecraft Center pilots Joseph Algranti and H.E. "Bud" Ream.
NASA had accumulated enough data from the LLRV flight program at the FRC by mid-1966 to give Bell a contract to deliver three LLTVs at a cost of $2.5 million each.
In December 1966 vehicle No. 1 was shipped to Houston, followed by No. 2 in January 1967, within weeks of its first flight. Modifications already made to No. 2 had given the pilot a three-axis side control stick and a more restrictive cockpit view, both features of the real Lunar Module that would later be flown by the astronauts down to the moon's surface.
After testing at the FRC, the LLRVs were sent to Houston, where research pilots learned to become LLTV instructor pilots. In December 1967, the first of the LLTVs joined the LLRVs to eventually make up the five-vehicle training and simulator fleet.
In all, NASA built five LM trainers of this type. During training flights at Ellington AFB near Houston, Texas, three of the five vehicles were destroyed in crashes. Two were an early version called the Lunar Landing Research Vehicle or LLRV. Neil Armstrong
was flying LLRV-1 on May 6, 1968 when it went out of control. He ejected safely and the vehicle crashed. A later version was called the Lunar Landing Training Vehicle or LLTV and three were built. Two of these were lost in crashes on December 8, 1968 (piloted by Joe Algranti) and January 29, 1971 (piloted by Stuart Present). The other pilots also ejected safely from the crashing LLTV's.
LLRV No. 2 was eventually returned to Dryden, where it is on display as a silent artifact of the Center's contribution to the Apollo program. The sole surviving LLTV, NASA 952, is on display at the Johnson Space Center.
There were two distinct modes of flight for the LLTV. The basic mode was with the gimbaled engine fixed to the body so that it always pointed downward in relation to the body. But in the gimbaled "Lunar Sim Mode", the engine was allowed to swivel and was kept pointing downward to the earth. This allowed the vehicle to tilt at the far greater angles that would be typical of hovering and maneuvering above the lunar surface. Despite its ungainly appearance, the LLRV was equipped with an astonishingly sophisticated array of early sensor and computational hardware. The system had no specific name, but the effect it produced was called "Lunar Sim Mode". This was the highest degree of hardware-based simulation, and was the purpose of the whole project. This was not a system to unburden the pilot, such as an autopilot
does, nor was it meant to introduce any sort of safety or economy. The system's sole intention was to project the illusion of piloting the Lunar Module. So, Lunar Sim Mode can be thought of as a mixture of stability augmentation, recalculation of vertical acceleration according to the lunar gravity constant, all followed by accompanied instantaneous corrective action. The LLRV's Lunar Sim Mode even was able to counter-correct wind gusts within milliseconds, as they definitely would have disturbed the impression of a missing atmosphere. Sensor input for the Lunar Sim Mode was the Doppler radar
. The visually significant sign of an engaged Lunar Sim Mode was the free-gimbaled turbofan
, always strictly pointing downward toward the ground, regardless the LLRV's current attitude. This unique aircraft represents one of the few hardware simulators that ever became airborne.
Donald "Deke" Slayton
, then NASA's chief astronaut, later said there was no other way to simulate a moon landing except by flying the LLRV.
by Bell Aerosystems, Inc. which had engineering facilities located in Niagara Falls
, New York
. The LLTV was a second generation vehicle, after the Lunar Landing Research Vehicle
, used by NASA Apollo Program astronauts to develop piloting skills. The LLTV provided Apollo program commanders the opportunity to experience the flight characteristics associated with the 1/6 gravity conditions on the moon. The first LLTV vehicle was assembled at Ellington Airforce Base in Houston, Texas in 1967. A total of 3 LLTV vehicles were eventually delivered to Ellington AFB. The last remaining of the three LLTV vehicles is on display at the Johnson Spacecraft Center in Houston, Texas.
The electronic control system was designed with redundant channels that used 2 of 2 logic. The outputs of each primary channel were compared on a continuous basis. If a fault was detected in the primary control system, then control was automatically switched to an identical backup channel and the pilot immediately took measures to bring the vehicle to the ground. All the controls were analog circuits utilizing Burr-Brown transistor amplifier modules and other analog components. Unlike modern digital control circuits, in 1967 the technology available was limited to discrete transistors.
Flying bedstead
The Flying Bedstead was a nickname given to two completely different experimental vertical take-off and landing aircraft, both receiving the nickname because each comprised a skeletal platform raised on four legs that resembled a bedstead....
, were used by the FRC, now known as the NASA Dryden Flight Research Center
Dryden Flight Research Center
The Dryden Flight Research Center , located inside Edwards Air Force Base, is an aeronautical research center operated by NASA. On March 26, 1976 it was named in honor of the late Hugh L. Dryden, a prominent aeronautical engineer who at the time of his death in 1965 was NASA's deputy administrator...
, at Edwards Air Force Base
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...
, California, to study and analyze piloting techniques needed to fly and land the Apollo Lunar Module
Apollo Lunar Module
The Apollo Lunar Module was the lander portion of the Apollo spacecraft built for the US Apollo program by Grumman to carry a crew of two from lunar orbit to the surface and back...
in the moon's low gravity environment.
The research vehicles were vertical take-off vehicles that used a single jet engine mounted on a gimbal
Gimbal
A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of two gimbals, one mounted on the other with pivot axes orthogonal, may be used to allow an object mounted on the innermost gimbal to remain immobile regardless of the motion of its support...
so that it always pointed vertically. It was adjusted to cancel 5/6 of the vehicle's weight, and the vehicle used hydrogen peroxide rockets which could fairly accurately simulate the behaviour of a lunar lander.
Success of the two LLRVs led to the building of three Lunar Landing Training Vehicles (LLTVs) used by Apollo astronauts at the Manned Spacecraft Center in Houston, Texas, predecessor of NASA's Johnson Space Center. Nearly all of the flying bedsteads were destroyed in crashes, but the purpose built rocket ejection seat system recovered the pilot safely in all cases.
The final phase of every Apollo landing was manually piloted by the mission commander. Because of navigational problems, Neil Armstrong
Neil Armstrong
Neil Alden Armstrong is an American former astronaut, test pilot, aerospace engineer, university professor, United States Naval Aviator, and the first person to set foot upon the Moon....
, Apollo 11
Apollo 11
In early 1969, Bill Anders accepted a job with the National Space Council effective in August 1969 and announced his retirement as an astronaut. At that point Ken Mattingly was moved from the support crew into parallel training with Anders as backup Command Module Pilot in case Apollo 11 was...
commander, said his mission would not have been successful without extensive training on the LLRVs and LLTVs.
Development
Built of aluminum alloy trussTruss
In architecture and structural engineering, a truss is a structure comprising one or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes. External forces and reactions to those forces are considered to act only at the nodes and result in...
es, the vehicles were powered by a General Electric CF700-2V
General Electric CF700
|-See also:-External links:* *...
turbofan engine with a thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
of 4,200 lbf (19 kN), mounted vertically in a gimbal
Gimbal
A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of two gimbals, one mounted on the other with pivot axes orthogonal, may be used to allow an object mounted on the innermost gimbal to remain immobile regardless of the motion of its support...
. The engine lifted the vehicle to the test altitude and was then throttled back to support five-sixths of the vehicle's weight, simulating the reduced gravity of the moon. Two hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...
lift rocket
Rocket
A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...
s with thrust that could be varied from 100 to 500 lbf (440 to 2,200 N) handled the vehicle's rate of descent and horizontal movement. Sixteen smaller hydrogen peroxide thrusters, mounted in pairs, gave the pilot control in pitch, yaw and roll. As safety backups, six 500 lbf (2,200 N) thrust rockets could take over the lift function and stabilize the craft for a moment if the jet engine failed. The pilot had an ejection seat for safety. Manufactured by Weber Aircraft LLC
Weber Aircraft LLC
Weber Aircraft LLC is an American manufacturer of airline seats headquartered in Gainesville, Texas. The company is a subsidiary of Zodiac Aerospace of France, and is one of the largest manufacturers of airline seats in the world, competing with companies such as Recaro, B/E Aerospace, and...
, it was one of the first zero-zero ejection seats, capable of saving the operator even if the aircraft was stationary on the ground - a necessity given the LLRV's low and slow flight envelope.
VTOL
A vertical take-off and landing aircraft is one that can hover, take off and land vertically. This classification includes fixed-wing aircraft as well as helicopters and other aircraft with powered rotors, such as cyclogyros/cyclocopters and tiltrotors...
) aircraft, NASA issued Bell a $50,000 study contract in December 1961. Bell had independently conceived a similar, free-flying simulator, and out of this study came the NASA Headquarters' endorsement of the LLRV concept, resulting in a $3.6 million production contract awarded to Bell on February 1, 1963, for delivery of the first of two vehicles for flight studies at the FRC within 14 months.
The two LLRVs were shipped from Bell to the FRC in April 1964, with program emphasis on vehicle No. 1. It was first readied for captured flight on a tilt table constructed at the FRC to test the engines without actually flying. The scene then shifted to the old South Base area of Edwards. On the day of the first flight, 30 October, 1964, research pilot Joe Walker
Joseph A. Walker
Joseph Albert "Joe" Walker was an American NASA test pilot, and member of the U.S. Air Force Man In Space Soonest program. In 1963, he made two X-15 Experimental rocket aircraft flights beyond the altitude of 100 kilometers - at the edge of outer space...
flew it three times for a total of just under 60 seconds to a peak altitude of ten feet (3 m). Later flights were shared between Walker; another Dryden pilot, Don Mallick; the Army's Jack Kluever; and NASA Manned Spacecraft Center pilots Joseph Algranti and H.E. "Bud" Ream.
NASA had accumulated enough data from the LLRV flight program at the FRC by mid-1966 to give Bell a contract to deliver three LLTVs at a cost of $2.5 million each.
In December 1966 vehicle No. 1 was shipped to Houston, followed by No. 2 in January 1967, within weeks of its first flight. Modifications already made to No. 2 had given the pilot a three-axis side control stick and a more restrictive cockpit view, both features of the real Lunar Module that would later be flown by the astronauts down to the moon's surface.
After testing at the FRC, the LLRVs were sent to Houston, where research pilots learned to become LLTV instructor pilots. In December 1967, the first of the LLTVs joined the LLRVs to eventually make up the five-vehicle training and simulator fleet.
In all, NASA built five LM trainers of this type. During training flights at Ellington AFB near Houston, Texas, three of the five vehicles were destroyed in crashes. Two were an early version called the Lunar Landing Research Vehicle or LLRV. Neil Armstrong
Neil Armstrong
Neil Alden Armstrong is an American former astronaut, test pilot, aerospace engineer, university professor, United States Naval Aviator, and the first person to set foot upon the Moon....
was flying LLRV-1 on May 6, 1968 when it went out of control. He ejected safely and the vehicle crashed. A later version was called the Lunar Landing Training Vehicle or LLTV and three were built. Two of these were lost in crashes on December 8, 1968 (piloted by Joe Algranti) and January 29, 1971 (piloted by Stuart Present). The other pilots also ejected safely from the crashing LLTV's.
LLRV No. 2 was eventually returned to Dryden, where it is on display as a silent artifact of the Center's contribution to the Apollo program. The sole surviving LLTV, NASA 952, is on display at the Johnson Space Center.
Lunar Sim Mode
Autopilot
An autopilot is a mechanical, electrical, or hydraulic system used to guide a vehicle without assistance from a human being. An autopilot can refer specifically to aircraft, self-steering gear for boats, or auto guidance of space craft and missiles...
does, nor was it meant to introduce any sort of safety or economy. The system's sole intention was to project the illusion of piloting the Lunar Module. So, Lunar Sim Mode can be thought of as a mixture of stability augmentation, recalculation of vertical acceleration according to the lunar gravity constant, all followed by accompanied instantaneous corrective action. The LLRV's Lunar Sim Mode even was able to counter-correct wind gusts within milliseconds, as they definitely would have disturbed the impression of a missing atmosphere. Sensor input for the Lunar Sim Mode was the Doppler radar
Doppler radar
A Doppler radar is a specialized radar that makes use of the Doppler effect to produce velocity data about objects at a distance. It does this by beaming a microwave signal towards a desired target and listening for its reflection, then analyzing how the frequency of the returned signal has been...
. The visually significant sign of an engaged Lunar Sim Mode was the free-gimbaled turbofan
Turbofan
The turbofan is a type of airbreathing jet engine that is widely used for aircraft propulsion. A turbofan combines two types of engines, the turbo portion which is a conventional gas turbine engine, and the fan, a propeller-like ducted fan...
, always strictly pointing downward toward the ground, regardless the LLRV's current attitude. This unique aircraft represents one of the few hardware simulators that ever became airborne.
Donald "Deke" Slayton
Deke Slayton
Donald Kent Slayton , better known as Deke Slayton, was an American World War II pilot and later, one of the original NASA Mercury Seven astronauts....
, then NASA's chief astronaut, later said there was no other way to simulate a moon landing except by flying the LLRV.
Specifications (LLRV)
Control system
The electronic control system for the Lunar Landing Training Vehicle was developed for NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
by Bell Aerosystems, Inc. which had engineering facilities located in Niagara Falls
Niagara Falls
The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has...
, New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
. The LLTV was a second generation vehicle, after the Lunar Landing Research Vehicle
Lunar Landing Research Vehicle
The Bell Aerosystems Lunar Landing Research Vehicle was an Apollo Project era program to build a simulator for the Moon landings. The LLRVs, humorously referred to as "flying bedsteads", were used by the FRC, now known as the NASA Dryden Flight Research Center, at Edwards Air Force Base,...
, used by NASA Apollo Program astronauts to develop piloting skills. The LLTV provided Apollo program commanders the opportunity to experience the flight characteristics associated with the 1/6 gravity conditions on the moon. The first LLTV vehicle was assembled at Ellington Airforce Base in Houston, Texas in 1967. A total of 3 LLTV vehicles were eventually delivered to Ellington AFB. The last remaining of the three LLTV vehicles is on display at the Johnson Spacecraft Center in Houston, Texas.
The electronic control system was designed with redundant channels that used 2 of 2 logic. The outputs of each primary channel were compared on a continuous basis. If a fault was detected in the primary control system, then control was automatically switched to an identical backup channel and the pilot immediately took measures to bring the vehicle to the ground. All the controls were analog circuits utilizing Burr-Brown transistor amplifier modules and other analog components. Unlike modern digital control circuits, in 1967 the technology available was limited to discrete transistors.
See also
External links
- LLRV Fact Sheet
- Lunar Landing Research Vehicle landing dynamics - NASA report (PDF format)
- Lunar Landing Terminal descent study using LLRV - NASA report (PDF format)
- Lunar Landing Research Vehicle - LM technology - NASA report (PDF format)
- LLRV/TV flight summary (sci.space.history post)
- http://grin.hq.nasa.gov/ABSTRACTS/GPN-2000-001901.html Pictures
- http://www.hq.nasa.gov/alsj/LLTV-952.html Pictures