Encyclopedia Astronautica
1969.05.27 - Manual guidance for TLI on Apollo missions


Apollo Program Director Sam C. Phillips wrote to MSC regarding a Flight Readiness Review action item on translunar injection (TLI: insertion into a trajectory toward the moon) dispersions after manual guidance for TLI on Apollo missions.

He enclosed a memorandum prepared by W. G. Heffron of Bellcomm, Inc., on the subject. Phillips stated that fuel reserves on Apollo 10 were such that dispersions seemed acceptable and he would have permitted use of manned guidance during TLI if it had been needed. He pointed out that margins would be much less for the Apollo 11 mission, and that it would be necessary either to reduce the dispersions or limit the use of the capability. ASPO Manager George M. Low replied to the letter on June 13 and submitted the following comments for consideration: ". . . I see little advantage to not attempting manual launch vehicle guidance for TLI. . . . If the dispersions are within the 120 feet (37 meters) per second budgeted for translunar midcourse corrections, the mission would be continued as planned. If the dispersions are within 270 feet (82 meters) per second, the mission would be completed utilizing a slower transearth trajectory. If the dispersions are very large, the mission would be limited to a circumlunar flight in which all of the service propulsion system and LM descent stage propellants could be used for midcourse corrections. . . ."

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