The Block II of Ranger’s seismic packages represented scientists’ earliest attempts to measure the seismic properties of the Moon. Rangers 3, 4, and 5 hoisted a seismometer within a balsawood impact-limiter at their apex, a device designed at the California Institute of Technology. During Ranger’s flight, the lunar seismometer was programmed to separate from the main capsule, with the seismometer breaking free from the rocket as it approached close enough to the Moon to be pulled in by gravity. The balsawood case would strike the surface at 150 MPH, at which point the seismometer could begin its measurements. The device floated in an oil film within the balsawood shield and was meant to transmit data for 30 days. Though it was designed to withstand a 200 MPH impact, all three attempts to crash on the Moon with a functioning seismic device failed. Rangers 3 and 5 missed the Moon due a guidance systems and electrical failure, respectively; Ranger 4 successfully hit the Moon but the computer-timer failed, thus preventing any data collection.

NASA's Marshall Space Flight Center transferred this to the Museum in 1972.