Kinetic-energy- absorbing liners made of aluminum foam have been developed to replace solid lead liners in blast containers on the aft skirt of the solid rocket booster of the space shuttle. The blast containers are used to safely trap the debris from small explosions that are initiated at liftoff to sever frangible nuts on hold-down studs that secure the spacecraft to a mobile launch platform until liftoff.
The desire to replace the lead liners arose from the large mass density of lead and its poor energy-absorption performance in the specific application, along with the toxicity of lead and its susceptibility to corrosion in the seacoast launch environment. The aluminum foam liners are products of a program of design and testing in which the mechanical properties of the foam were tailored for the specific application. Factors considered in the program included mass density, degree of porosity, sizes of pores, resistance to corrosion, strength-to-weight ratio, responses to loads, and variable stress-vs.-strain characteristics.
Static drop tests were performed on foams of various thicknesses and densities to optimize the design. On the basis of the results of these tests, aluminum foam liners with densities of 16 and 24 percent were selected. Sample foam liners were tested in a simulated launch configuration (see figure). The results of the tests showed that suitably designed and fabricated aluminum foam liners absorb energy more effectively than the solid lead liners do.
This work was done by Donald L. Balles, Thomas M. Ingram, Howard L. Novak, and Albert F. Schricker of USBI Co. for Marshall Space Flight Center. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category.
Inquiries concerning rights for the commercial use of this invention should be addressed to the Patent Counsel, Marshall Space Flight Center; (256) 544-0021. Refer to MFS-31563.