Historical Photo of the Month - June 2009

Impact Limiter
Photograph Number 355-1394B

In October 1965, JPL was working on various methods to enable a spacecraft to safely reach the surface of a planet. One of these was an "impact limiter" that would cushion the impact of landing. Unlike the airbags used by Mars Pathfinder and the Mars Exploration Rovers, this object was not designed to bounce, but to deflate immediately after impact, like an airbag in a car.

The prototype impact limiter included a series of Mylar "convexities" or domes, Mylar/nylon webbing, and cords made of music wire. The domes were clear to allow photographs of the payload upon impact. The limiter held a 12.2 pound payload suspended in the middle of the polyhedron. Before the impact limiter was assembled, its components were tested. There was a tensile test of the cords and webbing and a pressure test of one Mylar dome, which failed at 12.5 psi (about 7,000 pounds of force). The photo above shows Sheet Metal Shop technicians J.R. (Jimmy) Kallen (front) and E.A. (Gene) Otto fabricating the prototype.

The prototype impact limiter was about five feet in diameter, the largest that could be tested in JPL's vacuum chamber, launched from a pneumatic cannon. With next month's photo, you can learn more about those impact tests.

For more information about the history of JPL, contact the JPL Archives for assistance. [Archival and other sources: Ron Ross, Bill Layman, photo album and index, The Design and Testing of an Inflated Sphere Impact Limiter, December 15, 1966, Technical Report 32-1037, by Ross and Layman.]