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====Super light-weight ablator====
''SLA'' in ''SLA-561V'' stands for ''super light-weight ablator''. SLA-561V is a proprietary ablative made by [[Lockheed Martin]] that has been used as the primary TPS material on all of the 70° sphere-cone entry vehicles sent by NASA to Mars other than the [[Mars Science Laboratory]] (MSL). SLA-561V begins significant ablation at a heat flux of approximately 110 W/cm<sup>2</sup>, but will fail for heat fluxes greater than 300 W/cm<sup>2</sup>. The MSL aeroshell TPS is currently designed to withstand a peak heat flux of 234 W/cm<sup>2</sup>. The peak heat flux experienced by the ''[[Viking 1]]'' aeroshell which landed on Mars was 21 W/cm<sup>2</sup>. For ''Viking 1'', the TPS acted as a charred thermal insulator and never experienced significant ablation. ''Viking 1'' was the first Mars lander and based upon a very conservative design. The Viking aeroshell had a base diameter of 3.54 meters (the largest used on Mars until Mars Science Laboratory). SLA-561V is applied by packing the ablative material into a honeycomb core that is pre-bonded to the aeroshell's structure thus enabling construction of a large heat shield.<ref>{{cite
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