SpaceX's 31st robotic cargo mission is headed back to Earth.
SpaceX's Dragon cargo capsule undocked from the International Space Station (ISS) on schedule today (Dec. 16) at 11:05 a.m. EST (1605 GMT) today (Dec. 16). The spacecraft will begin a series of deorbit burns to complete the company's 31st commercial resupply services mission (CRS-31) for NASA, splashing down of the coast of Florida tomorrow (Dec. 17). The agency won't webcast the splashdown but will provide updates via its ISS blog.
CRS-31 is returning to Earth with thousands of pounds of equipment and experiment specimens from ongoing microgravity research aboard the space station. Dragon is currently the only ISS cargo spacecraft capable of returning equipment and experiments safely to Earth. The other two operational freighters — Northrop Grumman's Cygnus spacecraft and Russia's Progress capsule — face a fiery atmospheric incineration, burning up during reentry, along with whatever waste from the space station is packed aboard them.
The CRS-31 Dragon launched to the ISS from NASA's Kennedy Space Center (KSC) in Florida on Nov. 4, riding a SpaceX Falcon 9 rocket to low Earth orbit. The spacecraft rendezvoused with the orbital laboratory a day later, delivering about 6,000 pounds (2,700 kilograms) of science and supplies for the Expedition 71 astronauts aboard.
Related: SpaceX launches 3 tons of cargo on 31st ISS resupply flight for NASA (video)
Among those astronauts are NASA's Butch Wilmore and Suni Williams, who originally launched to the station on the first crewed flight of Boeing's Starliner spacecraft in June. Complications with Starliner turned an eight-day mission into an eight-month stint aboard the ISS for the two astronauts. NASA eventually decided to return Starliner to Earth uncrewed; Wilmore and Williams will come home in February on SpaceX's Crew-9 mission, which arrived at the station in September.
At the time of Starliner's launch, the ISS was in need of a pump replacement for its urine processing system, which Wilmore and Williams were tasked with delivering. To make room aboard the spacecraft, however, the two astronauts were forced to leave their own luggage behind, including their change of clothes and other personal items.
Two other cargo missions preceded CRS-31 after Wilmore and Williams' arrival — a Cygnus and a Progress mission, which were able to relieve the astronauts of their space station hand-me-downs and supply them their own shirts and toothbrushes. However, every cargo mission brings welcome goods to the station's entire crew, with a crowd-favorite supply of fresh fruits and vegetables.
Among the cargo CRS-31 delivered to the ISS last month were fresh food, research equipment, maintenance supplies and personal items to help sustain the orbiting astronauts.
NASA will be able to retrieve the CRS-31 Dragon spacecraft relatively quickly after splashdown tomorrow, reaping the benefits of any experiments in need of quick attending following atmospheric reentry. These experiments will be transported to NASA's Systems Processing Facility at KSC, where scientists are able to continue research in the post-microgravity environment.
Today's undocking was originally supposed to occur on Dec. 6, but bad weather in the splashdown zone pushed it back repeatedly.
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