SpaceX CRS-21, also known as SpX-21, was a Commercial Resupply Service mission to the International Space Station which launched on 6 December 2020. The mission was contracted by NASA and was flown by SpaceX using a Cargo Dragon 2. This was the first flight for SpaceX under NASA's CRS Phase 2 contract awarded in January 2016. This was also the first Cargo Dragon of the new Dragon 2 variant, as well as the first Cargo Dragon flight that was docked at the same time as a Crew Dragon spacecraft (SpaceX Crew-1). This mission used Booster B1058.4, becoming the first NASA mission to reuse a booster previously used on a non-NASA mission. This was also first time SpaceX launched a NASA payload on a booster with more than one previous flight.
Cargo Dragon
SpaceX plans to reuse the Cargo Dragons up to five times. It was launched without seats, cockpit controls, the life support system required to sustain astronauts in space and SuperDraco abort engines. Dragon 2 improves on Dragon 1 in several ways, including lessened refurbishment time, leading to shorter periods between flights. While CRS-21 was for a standard 30 days mission, the most recent Flight Planning Integration Panel (FPIP) document indicates that beginning with CRS-23, SpaceX cargo missions will begin to stretch out to 60 days and beyond. Sarah Walker, director of Dragon mission management at SpaceX, said "the new Cargo Dragon can stay at the space station for up to 75 days, more than twice as long as the first-generation Dragon spacecraft". With this mission, this was the first time that two Dragon capsules were docked at the ISS at the same time. Beginning with the CRS-21 mission, the new Dragon Cargo capsules splash down under parachutes off the coast of Florida in either the Atlantic Ocean or the Gulf of Mexico. This NASA preference was added to CRS-2 awards.
Mission
Timeline T+00:00: Liftoff T+01:18: Maximum aerodynamic pressure T+02:30: First stage main engine cutoff (MECO) T+02:34: Stage separation T+02:41: Second stage engine start T+06:37: First stage entry burn begins T+08:38: Second stage engine cutoff (SECO) T+08:38: First stage landing on drone ship T+11:49: Dragon separation T+12:35: Dragon nose cone open sequence begins
Return Dragon undocked from the ISS on 12 January 2021 at 14:05 UTC. SpaceX recovery teams were on standby for the parachute-assisted splashdown on 14 January 2021 at 01:26 UTC in the Gulf of Mexico, west of Tampa, Florida. Dragon returned to Earth with 2,002 kg (4,414 lb) of cargo, according to NASA.
Payload NASA contracted for the CRS-21 mission from SpaceX and therefore determines the primary payload, date of launch, and orbital parameters for the Cargo Dragon. The CRS-21 mission carries 2,972 kg (6,552 lb) of cargo to ISS.
Science investigations: 953 kg (2,101 lb) Vehicle hardware: 317 kg (699 lb) Crew supplies: 364 kg (802 lb) Spacewalk equipment: 120 kg (260 lb) Computer resources: 46 kg (101 lb) Russian hardware: 24 kg (53 lb) External payload (Nanoracks Bishop Airlock): 1,090 kg (2,400 lb)
Nanoracks Bishop Airlock, formerly known as Bishop Airlock Module, is a payload airlock attached to the Tranquility module of the ISS, commercially developed and operated by Nanoracks. The Bishop Airlock provides five times the satellite deployment volume previously available, when the Japanese Kibō airlock served that role alone. Nanoracks is the prime contractor, with Thales Alenia Space manufacturing the pressurized shell and Boeing providing the berthing mechanism. It is the second commercial module of the ISS, after the Bigelow Expandable Activity Module (BEAM), which was attached to the ISS in April 2016 and is expected to stay at the ISS until at least 2028. The Bishop Airlock began construction in 2015, and was berthed to Tranquility on 19 December 2020 by the Canadarm2.
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