at 28,000 mph (ca. 12.5 km/s) at 135 km altitude. This was faster than the Apollo mission capsules and 70% faster than the Shuttle. PICA was critical for the viability of the Stardust mission, which returned to Earth in 2006. Stardust's heat shield (0.81 m base diameter) was made of one monolithic piece sized to withstand a nominal peak heating rate of 1.2 kW/cm2. A PICA heat shield was also used for the Mars Science Laboratory entry into the Martian atmosphere. PICA-X An improved and easier to produce version called PICA-X was developed by SpaceX in 2006–2010 for the Dragon space capsule. The first reentry test of a PICA-X heat shield was on the Dragon C1 mission on 8 December 2010. The PICA-X heat shield was designed, developed and fully qualified by a small team of a dozen engineers and technicians in less than four years.<ref name="N+SX_picaX"> {{cite web |last=Chambers |first=Andrew |title=NASA + SpaceX Work Together |url=http://www.nasa.gov/offices/oce/appel/ask/issues/40/40s_space-x_prt.htm |publisher=NASA |access-date=2011-02-16 |author2=Dan Rasky |date=2010-11-14 |quote=''SpaceX undertook the design and manufacture of the reentry heat shield; it brought speed and efficiency that allowed the heat shield to be designed, developed, and qualified in less than four years. |url-status=dead |archive-url=https://web.archive.org/web/20110416170908/http://www.nasa.gov/offices/oce/appel/ask/issues/40/40s_space-x_prt.htm |archive-date=2011-04-16 }}</ref> PICA-X is ten times less expensive to manufacture than the NASA PICA heat shield material. PICA-3 A second enhanced version of PICA—called PICA-3—was developed by SpaceX during the mid-2010s. It was first flight tested on the Crew Dragon spacecraft in 2019 during the flight demonstration mission, in April 2019, and put into regular service on that spacecraft in 2020. SIRCA Silicone-impregnated reusable ceramic ablator (SIRCA) was also developed at NASA Ames Research Center and was used on the Backshell Interface Plate (BIP) of the Mars Pathfinder and Mars Exploration Rover (MER) aeroshells. The BIP was at the attachment points between the aeroshell's backshell (also called the afterbody or aft cover) and the cruise ring (also called the cruise stage). SIRCA was also the primary TPS material for the unsuccessful Deep Space 2 (DS/2) Mars impactor probes with their aeroshells. SIRCA is a monolithic, insulating material that can provide thermal protection through ablation. It is the only TPS material that can be machined to custom shapes and then applied directly to the spacecraft. There is no post-processing, heat treating, or additional coatings required (unlike Space Shuttle tiles). Since SIRCA can be machined to precise shapes, it can be applied as tiles, leading edge