Comments of the Space Shuttle crew indicate that the Launch Entry Suit (LES) may provide inadequate cooling before launch and after reentry. During these periods some crewmembers experienced thermal discomfort induced by localized cabin heating, middeck experiments, and crewmembers' body heat and humidity.The NASA Johnson Space Center(JSC) Crew and Thermal System Division (CTSD) executed a two phase study, analysis and testing, to investigate this problem. The analysis phase used a computer model of the LES to study the transient heat dissipation and temperature response under the various Space Shuttle flight cabin environments. After the completion of the analysis, the testing phase was conducted to collect the engineering data in order to validate the analysis results. Due to the constraint of the test facility, the test was conducted on the air cooled techniques only.This paper presents the analytical model, its solution and an evaluation and summary of the test results.