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  Apollo LLRV and LLTV training

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Author Topic:   Apollo LLRV and LLTV training
heng44
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Posts: 2564
From: Netherlands
Registered: Nov 2001

posted 08-26-2004 10:35 AM     Click Here to See the Profile for heng44   Click Here to Email heng44     Edit/Delete Message   Reply w/Quote
This is something I dug up in response to a request from Henry Matthews, who is writing a book on the Lunar Landing Research Vehicle (LLRV) and Lunar Landing Training Vehicle (LLTV), both used to train for landing on the moon.
Lunar landing training was 'touch and go'
by Ed Hengeveld
Spaceflight, vol. 34, December 1992

In the meantime, preparations for the first manned Apollo mission were picking up speed and in November 1967 the prime and backup crew assignments for the second and third flights were announced. It was part of the normal crewing policy that a backup team would skip the next two flights and then be assigned to a prime crew. This made the backup crews for the second and third Apollo flights eligible for assignment to a possible lunar landing mission further down the line. Therefore, the backup commanders of these flights, Pete Conrad and Neil Armstrong, respectively, were the first astronauts to begin training in the LLRV in early 1968.

By early May 1968, Conrad had made 13 flights in LLRV no. 1, still the only craft being flown at Ellington. On May 6, Neil Armstrong made his 21st flight in the vehicle and it ended in disaster.

Armstrong lifted off and flew to an altitude of about 150 meters, where he began a simulated lunar landing. When he had descended to about 70 meters, the LLRV began to pitch forward while picking up speed. Armstrong tried to halt this forward velocity by using his attitude control thrusters, but they did not respond properly and the vehicle started tilting to the right. When he was flying on his right side, Armstrong realized that he would not be able to stop this motion and he wisely ejected. Seconds later the LLRV crashed in a field and burned. Armstrong landed by parachute and walked away without injuries. The only damage, he said later, was that he bit his tongue...

Initially there was great concern that the accident would have a serious impact on the design of the actual Lunar Module. LM-1 had made an unmanned space flight in January 1968 and it would not be good news if a serious design flaw were to be found this far along in the program. While the LLRV was grounded, MSC Director Robert R. Gilruth appointed a five-man board of investigation to track down the cause of the crash. Among its members were pilots Joe Algranti and Don Mallick, as well as astronaut Bill Anders, who was in training as lunar module pilot for the third Apollo mission. On May 16, NASA Headquarters in Washington took the unusual step of forming a second review board to work with the team from Houston.

After a thorough investigation that lasted all summer, both groups reported on October 17, 1968, that the cause of the crash was not related to the design of the LM. It was found that helium in the propellant tanks had been depleted earlier than normal, resulting in insufficient pressure to force the hydrogen peroxide fuel to the attitude control rockets. A number of improvements was recommended and the boards concluded that the accident would have no bad effects on the lunar landing program.

Two weeks earlier, on October 3, 1968, the first LLTV had made its maiden flight at Ellington AFB. Joe Algranti made a four-minute checkout, during which he reached a maximum altitude of about 15 meters. The three LLTVs incorporated changes that were the result of the initial LLRV test program at FRC and their systems were more like that of the real LM. Each one had cost about $2.5 million.

During October and November, Algranti and Ream made 14 flights in the no. 1 vehicle. Astronaut training in the LLRV and LLTV had been suspended after the crash and it was important that it be resumed as soon as possible. Apollo-7 had flown in October and now Apollo-8 was about to be launched. If all went well, men would try to land on the moon in seven months.

On December 8, Algranti took off in LLTV no. 1 for a final checkout of the vehicle before it would be released for astronaut training. It was the 15th flight for this particular craft. About four minutes into his planned six-minute flight, when he had descended from 160 to about 65 meters, Algranti suddenly experienced stability problems. He ended the simulated lunar landing to regain control of his craft. That caused severe lateral oscillations, after which the LLTV began to fall like a brick. Algranti wasted no time and ejected, one second before the vehicle crashed and exploded. He landed safely nearby, his only injury being thigh bruises from the force of ejection.

The implications of this second crash were potentially serious. Had something vital been overlooked? Was the vehicle unsafe? If it was, there was not enough time to redesign it. Astronaut Wally Schirra, who had just commanded the Apollo-7 mission, was named head of the investigating team in Houston. On January 8, 1969, NASA Administrator Tom Paine asked the review board from NASA Headquarters that had studied Armstrong's accident to review its findings and determine if there was any connection between the two crashes. Next day, the crew for the Apollo-11 mission was named. If Apollos 9 and 10 were successful, astronauts Armstrong, Collins and Aldrin would be launched in July on the first lunar landing mission. Time was beginning to run out.

In the meantime, preparations at Ellington AFB continued for resumption of qualification flights in LLTV no. 2. Wally Schirra's investigation had soon focused on wind conditions during the December 8 accident. Since Joe Walker's first flight in 1964 there had been strict flight rules for LLTV operations. Winds were not to exceed 7m/s during takeoff or 9m/s at maximum altitude. Surface winds had been calm when Algranti took off, but later wind velocities of up to 15m/s had been measured at altitude. It was possible that this had caused the LLTV to become unstable.

No immediate connection between the two accidents was found and on April 7, 1969, Bud Ream successfully completed a six-minute flight in LLTV no. 2. For safety reasons the thrust level of the attitude control thrusters had been increased. About a dozen flights were planned before astronauts would be allowed to fly the vehicle again. Plans to use the LLTVs at the Kennedy Space Center just before Apollo-11 had been abandoned because of the fast-approaching launch date.

On June 5, Schirra's team presented its findings. They concluded that "the primary cause of the accident was that the vehicle entered a region of flight where aerodynamic moments overpowered the control system in use, such that attitude control was lost." In other words, a gust of wind had probably thrown the LLTV out of control. No systems malfunctions were found. As a result of the investigation the cabin roofs on the other LLTVs were removed to provide an outlet for trapped air.

These findings cleared the way for astronaut training to resume and on June 14, with about a month left before the Apollo-11 launch, Neil Armstrong made his first flight in the LLTV since his crash more than a year before. Over a period of three days he completed eight flights in the vehicle, for a total flight time of 40 min. 14 sec. During these eight flights he made 14 takeoffs and landings, six of which were in the lunar simulation mode.

Armstrong stressed the importance of the LLTV when he talked to news media after the flights. "We are very pleased with the way it flies," he said. "It's a significant improvement over the LLRV, which we were flying here a year ago. I think it does an excellent job of actually capturing the handling characteristics of the Lunar Module in the landing maneuver."

He added that "it's really a great deal different than any other kind of aircraft that I've flown. The simulation of lunar gravity has some aspects that make this type of flight sufficiently different from anything else we've done to make this vehicle very worthwhile, and I'm very pleased that I've had the opportunity to get some flights in it here just before the Apollo-11 flight."

micropooz
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Posts: 1239
From: Washington, DC, USA
Registered: Apr 2003

posted 08-26-2004 07:39 PM     Click Here to See the Profile for micropooz   Click Here to Email micropooz     Edit/Delete Message   Reply w/Quote
It was great to read so much about such a little known facet of Apollo. There is a bit of history out there on the LLRV flights at Edwards, but zilch on the flights at Ellington.

It is good too to see that Henry Matthews is digging into this. For any of you not familiar with Henry, he has produced some rocketplane books that have broken new frontiers (especially his MX-324 and X-2 books). His website.

spacecraft films
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From: Columbus, OH USA
Registered: Jun 2002

posted 08-31-2004 08:38 PM     Click Here to See the Profile for spacecraft films   Click Here to Email spacecraft films     Edit/Delete Message   Reply w/Quote
If LLRV were the first two vehicles with the later production vehicles designated LLTV, what was the structure at Langley called?

heng44
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Posts: 2564
From: Netherlands
Registered: Nov 2001

posted 09-01-2004 01:19 AM     Click Here to See the Profile for heng44   Click Here to Email heng44     Edit/Delete Message   Reply w/Quote
The tethered contraption at Langley was the Lunar Landing Research Facility or LLRF. I admit these names are very similar and cause confusion.

heng44
Member

Posts: 2564
From: Netherlands
Registered: Nov 2001

posted 09-06-2004 01:54 AM     Click Here to See the Profile for heng44   Click Here to Email heng44     Edit/Delete Message   Reply w/Quote
The rest of the story...
The first lunar landing mission was launched on July 16, 1969, and four days later Neil Armstrong successfully flew the LM Eagle to its designated landing spot on the Moon. However, the job of the LLTV was by no means complete. On July 9, one week before the Apollo-11 launch, Apollo-12 commander Pete Conrad had resumed flying the trainer in preparation for the next mission, scheduled for November. After a number of familiarization flights he flew the vehicle again in October and completed the series on October 26, 1969, with his 27th flight (including the 13 LLRV flights in 1968).

Conrad echoed Armstrong's praise of the vehicle when he remarked: "This is, like Neil said, the frosting on the cake as far as simulations are concerned. The LLTV is a tricky vehicle. So is the Lunar Module."

It became standard practice for Apollo commanders and their backups to fly a series of simulations in the LLTV about one month prior to the scheduled launch date. Apollo-13s Jim Lovell flew the trainer in March 1970 and Apollo-14s Al Shepard in December of that year. In between these flights the LLTVs were regularly taken aloft by MSC pilots to keep them in perfect flying condition. On one of these trials, on January 29, 1971, pilot Stuart M. Present lost his attitude control because of a failure in the electrical system of LLTV no. 2. The vehicle started flipping over backwards and when he was facing straight up, Present ejected and parachuted to safety.

The incident came two days before the Apollo-14 launch, but NASA hastened to say it would not affect the mission, since the LLTV's electrical system was totally different from that in the LM. There was some talk of ending the LLTV flights altogether because they were too risky. However, the astronauts strongly disagreed because experience had shown that the vehicles accurately forecast the LM's handling characteristics during the final descent to the Moon. Chief astronaut Deke Slayton said there was "no other way to simulate Moon landings except by flying the LLTV." NASA management concurred and the flights continued.

Final Flight

On November 13, 1972, three weeks before the final mission in the Apollo program, Apollo-17 commander Eugene A. Cernan made the last flight in LLTV no. 3 before it was retired. Despite the fact that three of the five training vehicles crashed, the program was very successful. Hundreds of LLTV flights had given the Apollo crews the confidence they needed to make a total of six flawless landings on the Moon. The LLRV/LLTV was absolutely essential to this record of success.

Two of the vehicles still exist today. LLRV no. 2 is displayed at the Dryden Flight Research Center, where it made its maiden flight in 1967. LLTV no. 3 had been on display at the Alabama Space and Rocket Center for 12 years when it was returned to Houston for the 20th anniversary of the Apollo-11 mission in 1989. It can now be seen at the Johnson Space Center's visitor center.

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