The Apollo Lunar Surface Drill (ALSD) was deployed on Apollo 15, 16, and 17. It consisted of a cordless, battery-operated motor with specialized drill bits and modular core stems. The system was designed to extract soil column samples and to create holes for emplacement of two heat flow probes into the lunar surface. Each core stem segment was a rigid but hollow tube measuring about 40 cm. (16 in.) in length. Joined together and driven into the surface, they enabled astronauts to drill as deep as 10 ft into the lunar soil.This drill was used for training. It was transferred from NASA to the Smithsonian in 1975 and placed on display in 1979.