This innovation provides for significantly improved protection from micrometeoroid and orbital debris (MMOD) particles, and reliably determines the location, depth, and extent of MMOD impact damage.

A typical thermal blanket has an external cover. Just under the external cover in this blanket, materials are added that improve the breakup of impacting MMOD particles. This layer is the disrupter layer. The preferred material options for the disrupter are fiberglass cloth (either e-glass or s-glass), or betacloth (which is a fabric woven from Teflon-coated glass fibers) due to their availability, low cost, good performance in impact tests, compatibility with the space environment, and compatibility with thermal function. Other materials, such as ceramic fabrics (Nextel ceramic cloth is an example), thin metal foils, metal woven materials, metal meshes, and metal foams can also be used in the disrupter layer.

A spacer is added to standard thermal blankets to improve MMOD shielding performance by allowing particles that are disrupted or broken up on the exterior layer or layers of the thermal blanket to expand across the gap created by the spacer. The expansion of the projectile debris delivers a lower energy and momentum per area on the back layer of the thermal blanket than would otherwise have been the case without the spacer. This lower energy and momentum areal density effectively reduces the mass required to stop high-speed MMOD particles. The spacer is composed of a low-mass, open-cell foam.

The open-cell foam allows the expansion of the debris cloud (whereas a closed-cell foam or honeycomb core would be less able to allow lateral expansion of the debris cloud, thus degrading the MMOD effectiveness of the spacer). The open-cell foam allows the spacer to retain its flexibility, while the closed-cell foam is more rigid. Open-cell foam allows for venting, which is important for space applications. The spacer can be further lightened by adding holes that reduce mass without decreasing the ability of the spacer to perform its function to keep the front layers separated from back layers of the thermal blanket. The thickness of the spacer can be increased to improve MMOD shielding performance. Spacers of 1 to 6 in. (≈2.5 to 15.2 cm) were tested, with the 1-in. spacer providing protection from 6.0- mm-diameter hypervelocity particles.

A stopper layer, composed of high strength-to-weight materials such as Spectra 1000 or Kevlar KM2 fabric materials, is added to standard thermal blankets near the back side of the thermal blanket, to improve its MMOD protection capability. The purpose of the stopper layer is to slow or stop the debris created from the projectile impact on the outer layers of the blanket.

This work was done by Eric Christiansen, Christopher Madden, Kristin Stafford, Dana Lear, John Alred, and Kristina Rojdev of Johnson Space Center; and Terry Byers of Jacobs Technology. MSC-25247-1


NASA Tech Briefs Magazine

This article first appeared in the November, 2015 issue of NASA Tech Briefs Magazine.

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