The last 300 feet to the moon
After making the 240,000-mile journey to the moon cruising through open space, the last 300 feet down to landing represented the most difficult and dangerous part of the Apollo missions.
The Apollo astronauts needed a way to practice that final descent and landing before Apollo 11 astronauts Neil Armstrong and Edwin “Buzz” Aldrin made the first historic moon landing in their lunar lander named Eagle on July 20, 1969.
On the 45th anniversary of the first moon landing, it’s worth looking back at the development of one type of the lander simulators, the Lunar Landing Research Vehicle, or LLRV.
At the start of the Apollo program in 1961, there were no simulators for would-be moonwalkers to learn the art and finesse of landing on the lunar surface. So, as the program got under way, NASA began planning for such simulators. Three types were developed: an electronic simulator, a tethered lander, and the ambitious NASA Flight Research Center contribution, a free-flying vehicle. The three types became serious projects, and all contributed greatly to the success of Apollo.
The LLRVs, humorously referred to as flying bedsteads, were used by NASA’s Flight Research Center at Edwards Air Force Base, Calif., to study and analyze piloting techniques needed to fly and land the Apollo Lunar Module in the moon’s airless environment.
Success of the two LLRVs led to the building of three Lunar Landing Training Vehicles used by Apollo astronauts at the Manned Spacecraft Center in Houston, predecessor of NASA’s Johnson Space Center.
Neil Armstrong, first human to step onto the moon’s surface, said the mission would not have been successful without the type of simulation provided by the LLRVs and LLTVs.
Built of aluminum alloy trusses, the vehicles were powered by a 4,200-pound thrust General Electric CF-700-2V turbofan engine 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 rockets with thrust that could be varied from 100 to 500 pounds 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-pound 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 that would then lift him away to safety.
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.
Modifications to some of the vehicles gave astronauts a three-axis side control stick and a more restrictive cockpit view, both features of the real lunar module that they would later fly down to the moon’s surface.
During training flights at Houston, three of the five vehicles were destroyed in crashes; LLRV No. 1 in May 1968 and two LLTVs in December 1968 and January 1971. Neil Armstrong was one of the pilots who ejected to safety following an engine failure.
Donald “Deke” Slayton, then NASA’s chief astronaut, later said there was no other way to simulate a moon landing except by flying the LLTV.
The final 300-foot descent to the lunar surface was the last major step in the journey to the moon, leading to Armstrong’s incredible first step there 45 years ago.
Epilogue: NASA back on pathway to deep space
NASA’s path to Mars is utilizing a stepping-stone approach consisting of fundamental human health research and technology demonstrations aboard the International Space Station; development and evolution of the Space Launch System and Orion spacecraft to enable human exploration missions in deep space, including to an asteroid; and development of game-changing technologies for tomorrow’s missions.
Though not a major player in the agency’s solar system exploration strategy, NASA Armstrong nevertheless is supporting NASA’s human space flight efforts on several fronts, including flight tests of advanced Space Launch System rocket control systems, structural loads tests of a prototype Hypersonic Inflatable Atmospheric Decelerator, and flight validation of a large number of promising space-technology payloads on sub-orbital rockets, high-altitude balloons and parabolic-profile reduced-gravity aircraft via the Flight Opportunities Program.
For more on how NASA is celebrating the 45th anniversary of the first Apollo moon landing and the steps the agency is taking for its “next giant leap” to extend human presence further into the solar system, visit: http://1.usa.gov/1qZwiZO
In the words of NASA administrator Charlie Bolden, “In this year after Neil’s passing, knowing that he is looking down at us as we strive to measure up to what he would have expected of us as a nation, I feel very special obligation to say ‘thank you’ Neil, Buzz and Mike. We’re standing on your shoulders, building on your historic achievements, and getting ready to take the next giant leap for humankind.”
EDITOR’S NOTE – NASA marks the 45th anniversary of the first moon landing this month while it takes the steps needed for America’s next giant leap to send astronauts to Mars. NASA’s Apollo 11 crew landed on the moon July 20, 1969. The world watched 45 years ago as astronauts Neil Armstrong and Buzz Aldrin set their lunar module Eagle down in the Sea of Tranquility, while crewmate Michael Collins orbited above in the command module Columbia. NASA’s Flight Research Center at Edwards Air Force Base – recently renamed to honor the late Neil Armstrong – made a number of contributions to the NASA human space flight program during that era. Two of the most significant were the X-15 rocket plane hypersonic research program and the Lunar Landing Research Vehicle, both of which had a direct impact on the Apollo missions to the moon.
This article, originally published in July 2004 on the 35th anniversary of the Apollo 11 moon mission, explores the contributions of the Lunar Landing Research Vehicle (LLRV) development and flight-testing to the Apollo moon-landing program.