The art and science of re-entering a vehicle into a planetary atmosphere poses many problems, which are today on the edge of man’s mental and industrial capabilities. Re-entering a vehicle into the earth’s atmosphere incurs the following major problems: —

• (a) Kinetic heating as it passes through the denser regions of the atmosphere. Materials have to be found which can deal with the enormous amounts of heating experienced by the vehicle.

• (b) Design of a vehicle to withstand large thermal and mechanical shock.

• (c) Dynamic stability at hypersonic velocities.

• (d) Accuracy of direction of entry into the atmosphere.

• (e) Recovery of the capsule after impact, wherever it landed.

This paper deals with the kinetic heating aspect of re-entry and shows how present day materials are utilised in restricting the inside temperature of re-entry vehicles to within reasonable limits. Unmanned re-entry is specified because to re-enter a manned capsule puts large restrictions on deceleration and inside temperature limits and hence produces some unique problems which are not covered in this paper.