From the Archives (July 28, 1971): Apollo-15 and Moon landing

The Apollo-15 Astronauts successfully fired their main spacecraft engine for one second in a special test to-night [Space Centre, Houston, July 27] clearing the way for a lunar landing attempt on Friday. There is a short circuit somewhere in the engine’s electrical system. If the engine had not fired, astronauts David Scott, James Irwin and Alfred Worden would have abandoned the landing goal and conducted an alternate lunar orbit scientific mission. Mission Commander David Scott sounded jubilant and relieved. Mission Control said the test proved that the trouble with the engine system was only something “which might be a little annoying.” Slightly more than half-an-hour before the firing, Apollo-15 passed the half-way point of its outward journey, when it was 209,354 km. from both earth and moon. Experts at Mission Control will need time to evaluate the engine burn. But Flight Director Glynn Lunney said earlier to-day that if the power plant fired as planned, the astronauts would press on with the landing. Astronauts Scott and Irwin are to land at the base of the Apennine mountains, the tallest on the moon, to search for clues to the birth of the solar system.