Lockheed Martin’s aeroshell is about to be tested during Curiosity’s fiery plunge through the Martian atmosphere. The 14.8 ft diameter heat shield is covered with tiles of PICA (phenolic impregnated carbon ablator), while the back shell is covered with the material that formed the heat shield of earlier Mars vehicles. The PICA tiles are carefully arranged to minimize chances of super heated plasma torching its way through the gaps between the sections during entry.
Here Gary Napier from Lockheed Martin shows a sample of the lightweight PICA (yellow, on left) and the honeycomb supporting structure that supports the tiles. Depending on the exact trajectory, the material may have to cope with temperatures up to 3,800 deg F (2,100 deg C)
Unusually, a critical part of the entry, descent and landing includes the ejection of heavy masses of tungsten to alter the spacecraft’s center of gravity. This will be used to help create lift to steer the vehicle during the hypersonic entry phase. Initial orientation of the Curiosity starts with ejection of two 160 lb masses shortly after cruise stage separation. It will later be re-orientated to put it in a better attitude for deployment of the parachute by ejection of a further six masses of tungsten – each weighing some 55 lb.