With the Expedition 64 team now formally in charge aboard the International Space Station (ISS), NASA has announced that the first uncrewed visiting vehicle of their increment will launch from historic Pad 39A at the Kennedy Space Center (KSC) in Florida, no sooner than December.
The CRS-21 mission—SpaceX’s first flight under the second-phase Commercial Resupply Services (CRS2) contract with NASA—will mark the first outing of the cargo-carrying version of the Crew Dragon which launched Demo-2 astronauts Doug Hurley and Bob Behnken back in May. For the first time, a Cargo Dragon will autonomously dock (rather than berth) at the space station and, also for the first time, it is expected to do so whilst a Crew Dragon is in residence.
December’s launch will come on the back of more than a decade of Dragon operational experience, which began in December 2008 when SpaceX was awarded its initial CRS1 contract by NASA. Under the terms of that $1.6 billion deal, the Hawthorne, Calif.-headquartered launch services provider was required to fly 12 Dragon cargo flights and transport up to 44,000 pounds (20,000 kg) of supplies to successive ISS crews. Three additional missions were secured in early 2015, followed by five more in spring 2016, which resulted in the CRS1 first-phase contract closing out in March 2020 with the launch of the CRS-20 flight.
Across the span of those 20 missions, a cumulative total of 95,000 pounds (43,000 kg) of cargo was taken to the station and around 75,000 pounds (34,000 kg) was brought home. Unlike the other ISS uncrewed visiting vehicles—Russia’s Progress, Japan’s H-II Transfer Vehicle (HTV), Europe’s Automated Transfer Vehicle (ATV) and Northrop Grumman Corp.’s Cygnus—Dragon alone has the capability to return payloads safely back through Earth’s atmosphere and into the hands of researchers.
And although each uprated Cargo Dragon for CRS2 (based on SpaceX’s Crew Dragon design) is able to fly up to five flights to the ISS, its first-generation predecessor could more than hold its own in terms of reusability. From June 2017 to earlier this year, nine individual Dragons flew more than once and, indeed, the final three CRS1 ships launched in July and December 2019 and March of this year were marking their third trips to the ISS.
In fact, the capsule which flew CRS-20 had pulled off its most recent station duty only 15 months prior, making it the current first-place record-holder for the shortest turnaround between two missions by a Cargo Dragon.
In the meantime, in January 2016, SpaceX was one of three finalists (alongside Northrop Grumman and Sierra Nevada Corp.) to win funding for the second-round CRS2 contract to continue restocking the ISS in the 2019-2024 timeframe. Under the terms of this award, SpaceX is required to deliver at least six more cargo-filled Dragons to the station, of which CRS-21 will be the first.
Assuming an on-time launch in December, it is expected that the vehicle will dock autonomously at International Docking Adapter (IDA)-3 on the space-facing (or “zenith”) port of the Harmony node a couple of days later, for a month-long stay. Whereas the CRS1 Dragons were “berthed”—captured by means of the station’s 57.7-foot-long (17.6-meter) Canadarm2, then affixed to a Common Berthing Mechanism (CBM) on either the Harmony or Unity nodes—the CRS2 Dragons (like their astronaut-carrying cousins) are capable of fully autonomous dockings.
For its part, Northrop Grumman has already kicked off its own CRS2 commitment, with three Cygnus launches between November 2019 and the currently in-progress NG-14 mission, whilst Sierra Nevada targets the maiden voyage of its Dream Chaser Cargo System late next year atop a United Launch Alliance (ULA) Vulcan-Centaur heavylifter.
Taking pride of place aboard CRS-20 for December’s mission is the Bishop commercial airlock, destined for installation onto the starboard port of the Tranquility node. Preparations of the node for Bishop’s arrival were completed during an Extravehicular Activity (EVA) by Expedition 63 spacewalkers Chris Cassidy and Bob Behnken last summer.
The origins of this first-ever private airlock—which is being developed jointly between Thales Alenia Space, ISS prime contractor Boeing and NanoRacks—date back to the middle of the last decade. In May 2016, a Space Act Agreement (SAA) was signed between NASA and NanoRacks and early the following year Boeing was selected to build Bishop’s Passive CBM, with Thales Alenia Space responsible for the pressure shell, Micrometeoroid Orbital Debris (MMOD) shielding and Multi-Layer Insulation (MLI) for the airlock.
The project passed Critical Design Review (CDR) in March 2018 and early in 2019 Thales Alenia Space announced that it had completed work on Bishop and was preparing it for shipment to NanoRacks’ facility in Houston, Texas.
“The airlock module will provide a broad range of capabilities to our payload customers and expand greatly on the commercial utilization of the station,” noted Brock Howe, NanoRacks’ head of airlock, in a February 2017 press release. Commercial opportunities aboard Bishop are expected to include the kind of cubesat and smallsat deployments currently handled by Japan’s Kibo lab. All told, Bishop reportedly has five times greater capacity for cubesat and smallsat deployments than are currently available on the ISS.
In addition to Bishop, a number of other payloads will ride uphill aboard CRS-21. Joseph Wu of Stanford University is leading the Cardinal Heart study, which will explore changes in gravitational force on cardiovascular cells at cellular and tissue levels using Engineered Heart Tissues (EHTs). This research may help to identify heart treatments which might benefit people on Earth.
Elsewhere, Cody Farinacci of the Middleburg Heights, Ohio-based research and technology firm ZIN Technologies is supplying its HemoCue device to provide quick and accurate white blood cell counts in microgravity. This will allow the measurement of a variety of health conditions, including viral and bacterial infections, impacts of radiation exposure and inflammatory diseases.
And Charles Cockell of the University of Edinburgh in Scotland is leading the BioAsteroid Investigation to ascertain the role in gravity in the interaction between microbes and rock within liquid media, a particularly vital focus as NASA looks ahead to the future use of lunar regolith in life-support and other systems.