History and experience of overcoming thermal barriers in rocket and space technology: 2. ballistic and sliding descent of spaceships.

This paper continues the series of publications on the history of overcoming "thermal barriers" in the space and rocket industry. "Thermal barrier" is an obstacle hampering the operation of individual assemblies, aggregates, or even the entire spacecraft in general due to off-the-scale thermal loads. First-generation crewed spaceships faced a serious danger from the "thermal barrier" caused by aerodynamic heating during atmospheric descent from a low-Earth orbit or during the return from the Moon with the velocity close to the second escape velocity. This paper briefly touches upon the history of choosing structural and layout solutions for the first-generation spaceships in the USSR and the USA. The most emphasis is given to specifics of creating thermal protection of reentry vehicles of spaceships. In the creation of thermal protection systems, the experience of creating warheads of long-range guided missiles played a very important part. The paper remarks on the efficiency of polymer composite materials as elements of ablative thermal protective coatings. Characteristics of descent vehicles of different generation spaceships are compared. [ABSTRACT FROM AUTHOR]