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Experiment Title: Balloon Material Degradation

Original Principal Investigator(s): Strganac, Dr. Thomas - Invest. Role: Present, Allen, David - Invest. Role: Original,

It has been observed that exposure of polymers to the low Earth orbit (LEO) environment can result in significant degradation due primarily to atomic oxygen attack. LEO lies between 200 and 500 km above the Earth's surface and has an atmosphere which consisted predominately of atomic oxygen. Spacecraft at this particular orbit travel at a rate of 8 km/s which has the effect of providing the atomic oxygen with a translational energy of approximately 5 eV as it strikes ram facing (direction of travel) surfaces. Under these condition many polymers are degraded with resulting mass loss.

With the increasing importance of polymers in orbiting spacecraft it has become imperative to determine how, and to what extent, the properties of polymers are affected by this type of an environment. Knowing this polymers can subsequently be developed or selected which are suitable for LEO applications. This degradation is synergistically increased in the presence of high levels of ultraviolet (UV) radiation. To date, the large body of knowledge associated with the use of polymers in LEO has probed the chemical mechanisms associated with atomic oxygen attack and UV exposure. Although it is recognized that the presence of atomic oxygen and UV radiation alters the chemical integrity of polymers, it was not know to what extent these chemical alterations affect the mechanical behavior of the material.

Data on the effects of the space environment on very thin polymeric films are needed to properly support NASA programs involving the flight of extremely high altitude scientific balloons. In particular, significant scientific benefit will be derived from the development of a long-duration balloon platform capable of carrying payloads on the order of 250 kg to altitudes greater than 40 km for periods in excess of 60 days. The National Scientific Balloon Facility has actively pursued this program in the past. However, the engineering of these large systems could be significantly accelerated if data regarding degradation and/or alteration of various material properties could be obtained and compared to laboratory simulations of the space environment.

LDEF was essentially a free-flying cylindrical structure developed by NASA to accommodate 57 totally self-contained experiments on trays mounted on the exterior of the structure. The extended duration of the LDEF mission significantly enhanced the opportunities to characterize the morphological and mechanical properties of exposed polymers. The balloon materials exposure experiment by Texas A&M, S1006, consisted of 38 polymer film specimens and 24 fibrous cord specimens. The location of these samples (polyethylene, polyester, and nylon films in addition to Kevlar fibers) on the LDEF was fortuitous because they were exposed to the smallest amount of direct sunlight of any other experiment row aboard the satellite. In addition, the samples were placed such that the normal from the surface of the samples was nearly perpendicular to the ram direction of the atomic oxygen flux, thereby limiting the atomic oxygen fluence of the specimens. The finding of this research contributes to the predictive models of material constitutive characteristics.

Photograph Classification: Postflight

Associated Photograph(s):
LaRC - L90-13439
KSC - KSC-390C-1033.09
JSC - None
LaRC - L90-10454
KSC - None
JSC - S32-82-006
LaRC - L84-07068
KSC - KSC-384C-193.10
JSC - None

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