page_title: Apollo 6
section_title: Vehicle assembly
hierarchical_section_title: Apollo 6 / Vehicle assembly
caption_attribution_description: English: The Lunar Module Test Article [LTA] 2R, for the second Saturn V mission, is being moved from the low bay of the Manned Spacecraft Operations Building for mating with the spacecraft Lunar Module Adapter. The second Saturn V [502], except for a different lunar return trajectory, will be a repeat of the Apollo 4 unmanned Earth orbital flight of a high apogee for systems testing using several propulsion system burns and a heat shield test at lunar re-entry speed. Français&#160;: La ùaquette du module lunaire du programme Apollo, code LTA-2R (Lunar Module Test Article ), est préparée au centre spatial à Houston avant d'être lancée le 4 avril 1968 avec le vol Apollo 6 pour tester le comportement dynamique de sa structure. Le moteur et les équiments sont remplacés par des instruments de mesure.
context_page_description: Apollo 6, launched on April 4, 1968, was the second A-type mission of the United States Apollo program, an uncrewed test of the Saturn V launch vehicle. It was also the final uncrewed Apollo test mission.
  The objectives of the flight test were to demonstrate trans-lunar injection capability of the Saturn V with a simulated payload equal to about 80% of a full Apollo spacecraft, and to repeat demonstration of the command module's heat shield capability to withstand a lunar re-entry. The flight plan called for following trans-lunar injection with a direct return abort using the command and service module's main engine, with a total flight time of about 10 hours.
  A phenomenon known as pogo oscillation damaged some of the Rocketdyne J-2 engines in the second and third stages by rupturing internal fuel lines, causing two second-stage engines to shut down early. The vehicle's onboard guidance system was able to compensate by burning the second and third stages longer, though the resulting parking orbit was more elliptical than planned. The damaged third-stage engine also failed to restart for trans-lunar injection.
context_section_description: The S-IC first stage arrived by barge on March 13, 1967, and was erected in the VAB four days later, with the S-IVB third stage and Instrument Unit computer arriving the same day. The S-II second stage was two months behind them and so was substituted with a dumbbell-shaped spacer so testing could proceed. This had the same height and mass as the S-II along with all the electrical connections. The S-II arrived May 24. It was stacked and mated into the rocket on July 7.
  Testing was slow as they were still checking out the launch vehicle for Apollo 4, a limitation of the system where there wasn't two of everyone and everything. The VAB could handle up to four Saturn Vs, but could only check out one at a time.
  The CSM, a Block I model, similar to that flown on three previous uncrewed tests, arrived September 29 and was stacked December 10. It was actually a hybrid of two production spacecraft, consisting of CM-020 and SM-014, since SM-020 had been destroyed in a tank explosion and CM-014 had been dismantled to support the investigation into the Apollo 1 fire. After two months of testing and repairs, the rocket was moved to the pad on February 6, 1968.
caption: The Lunar Module Test Article (LTA-2R) is being moved for mating with the spacecraft–LM adapter.
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