The cone-shaped Mercury spacecraft consisted of a single module, or capsule, pressurized with pure oxygen. The single astronaut rode in a seat with his back towards the base. An escape tower powered by rocket topped the spacecraft, being designed to pull the capsule away from the launch vehicle in an emergency. Strapped to the base was a retro-rocket pack, which was fired to slow down the spacecraft so that it could drop from orbit. Externally, the base was covered with a heat shield of ablative material - material that melted and boiled off under re-entry heating. Final braking for Mercury was provided by parachute, housed in the top of the cone. The heat shield extended just before splashdown at sea to cushion the impact.
