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| A Scout Reentry Test launch cover from “Hudson”, postmarked at Wallops Island with a machine cancel on August 18, 1964. |
The primary purpose of the Scout Reentry Test 4 (Scout S-129R / X-4A) was to evaluate ablative heat-shield material for Apollo's Command Module under simulated lunar-return conditions. The test article used Avcoat 5026-39 H/G, a low-density charring ablative material being considered for the Apollo spacecraft. The Scout's trajectory was designed to reproduce the intense heating and aerodynamic loads that a spacecraft would encounter during atmospheric reentry from the Moon.
