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Evaluation of Reentry Effects of Delta II Second Stage Propellant Tanks

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Aerospace Corporation El Segundo United States

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Reentry effects were determined for two Delta II Stage 2 propellant tanks that reentered Earths atmosphere. One of the tanks reentered on February 19, 2010 and landed near Buren, Mongolia. The tank was retrieved from Mongolia by AFSMC and provided to Aerospace for a thorough metallurgical evaluation. Reentry effects were determined by visual observations, hardness measurements, and microstructural evaluations of mounted and polished cross sections including scanning electron microscopy with energy-dispersive x-ray spectroscopy for chemical analyses. Peak reentry surface temperatures were estimated at various locations on the cylindrical tank with domed ends. The other tank reentered and landed near Durbanville, South Africa on April 27, 2000. Although this tank was not retrieved by the USAF for evaluation, it was moved to and is on display at the South African Astronomical Observatory SAAO in Cape Town. Dr. Peter Martinez of the University of Cape Town generously provided photographs of the entire exterior surface of the South Africa tank to Aerospace for assessing its reentry condition. Reentry effects on the two tanks were compared to those documented by Aerospace in 2003 on a Delta II Stage 2 propellant tank that reentered over The United States on January 22, 1997 and landed in Texas. Common observations for the Texas, South Africa, and Mongolia debris included complete removal of an epoxy primer coating from the exterior surface, molten metal splatters at numerous locations on the tank surfaces, and localized melting along portions of the forward and aft ends of the cylindrical section due to enhanced aerodynamic heating at the exposed edges. A large hole through the forward dome wall was created by melting of the 410 stainless steel tank skin on the Texas and Mongolia tanks, but not on the South Africa tank. It was concluded that molten aluminum that splattered onto the propellant tanks from attachment hardware ignited and burned in the atmosphere.

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Technical Report




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Approved For Public Release;

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