PATENT OF SPACECRAFT RADIATOR COVER (1969): Patent Greeting Card

Text on the reverse side:

The space shuttle has a thermal protection, also known as a heat shield, with more than 30,000 tiles made essentially of sand, enabling the shuttle to withstand the intense heat when re-entering the earth's atmosphere. Even after being heated to peak temperature, the tiles are able to cool fast enough to be held by the naked hand only a minute later.