Apollo 15 15 separated from the booster, the S-IVB maneuvered away, and would impact the Moon about an hour after the crewed spacecraft entered lunar orbit, though due to an error the impact was away from the intended target. The booster's impact was detected by the seismometers left on the Moon by Apollo 12 and Apollo 14, providing useful scientific data. There was a malfunctioning light on the craft's service propulsion system (SPS); after considerable troubleshooting, the astronauts did a test burn of the system that also served as a midcourse correction. This occurred about 028:40:00 into the mission. Fearing that the
Apollo 21 Apollo 21 "Apollo 21" is an apocryphal reference to an eleventh manned Moon landing mission of NASA's Apollo program. Apollo contracted for the construction of fifteen Saturn V launch vehicles used to launch the Apollo spacecraft to the Moon, and achieved the first manned landing with the sixth one (Apollo 11), leaving nine for follow-on lunar missions, through Apollo 20. However, budget cuts caused NASA to cancel the last three missions, ending the lunar program after Apollo 17. One Saturn V was used to launch the Skylab space station, and parts of the other two became museum displays. An "Apollo