CRS-20 Dragon brings fresh science, new equipment to ISS
/
CRS-20 Dragon was berthed to the Earth-facing port of the Harmony module on March 9, 2020. Credit: NASA
The final first-generation Dragon spacecraft has been captured by the International Space Station’s robotic arm, marking the final time a SpaceX vehicle is planned to be berthed to the orbiting outpost.
At the controls of the robotic arm inside the ISS was NASA astronaut and Expedition 62 Flight Engineer Jessica Meir. She was backed up by NASA’s Drew Morgan.
While the ISS and CRS-20 Dragon spacecraft were some 422 kilometers over Vancouver, British Columbia, Meir commanded the 17.6-meter-long Canadarm2 remote manipulator system to grapple the spacecraft. Capture took place at 10:25 a.m. UTC March 9, 2020.
“The SpaceX-20 mission is a milestone for several reasons,” Meir said after the spacecraft was captured by the robotic arm. “It is, of course, the 20th SpaceX cargo mission, but it is also the last SpaceX cargo vehicle captured by the Canadarm as future vehicles will automatically dock to the space station.”
Meir also noted this was the third time this particular capsule has visited the outpost and demonstrates a “more sustainable approach” that she says is paramount to the future of spaceflight.
Following capture, ground controllers took over the several-hour process of moving the cargo freighter to its berthing location at the Earth-facing port of the Harmony module, near the forward end of the orbiting outpost.
Following installation and leak checks, the hatches between the station and spacecraft were open to allow the crew to begin the process of unloading the nearly 2,000 kilograms of supplies, experiments and hardware.
According to NASA, the pressurized compartment of CRS-20 Dragon holds 960 kilograms of science investigations, 273 kilograms of crew supplies, 56 kilograms worth of spacewalking equipment and 1 kilogram of computer resources.
Inside the external trunk is a new 468-kilogram payload platform called Bartolomeo, which is slated to be removed and attached to the forward facing side of the Columbus module later in March.
In April, a spacewalk is expected to be performed to attach power and data cables to Bartolomeo to fully activate the new platform, which has 12 different mounting locations for external payloads.
Once unloaded, CRS-20 Dragon will be reloaded with unneeded equipment and experiments slated to return to Earth to be analyzed in laboratories.
Unberthing via Canadarm2 is scheduled for April 6 with a reentry and splashdown in the Pacific Ocean off the coast of Baja California slated for several hours after release.
Once on Earth, it will wrap up the original Commercial Resupply Services contract, which was worth some $3 billion dollars for SpaceX alone. In total, 43 metric tons of supplies were delivered to the ISS over 20 missions since 2012. 33 metric tons will have been returned during that same amount of time.
The next Dragon cargo resupply mission will use a cargo variant of the spacecraft being used to send crew to the ISS. CRS-21 is currently scheduled for late October 2020.
All Dragon 2 missions, including the crewed flights starting with Demo-2 as early as May 2020, are designed to dock to an international docking adapter on the Harmony module.
The Demo-1 Dragon approaches the International Space Station in March 2019. The spacecraft docked to the forward port of the Harmony module where International Docking Adapter 2 is located. Credit: NASA
There are two adapters on Harmony — one in the front and one on the space-facing side of the module. They are themselves attached to pressurized mating adapters, which were used by the Space Shuttle between 1998 and 2011.
One downside to docking, rather than being berthed, is the size of the passageway into the ISS. Berthing mechanisms are much larger, allowing for bulkier items to move between the spacecraft and station.
International Docking Adapter 2 was installed during an August 2016 spacewalk. Credit: NASA
Berthing mechanisms have a square passageway of roughly 127 by 127 centimeters while the round docking ports have a transfer diameter of about 80 centimeters.
According to SpaceX, each cargo variant of Dragon 2 is expected to be flown up to five times. However, each of the crew variant is only planned to be flown once.
While the cargo variant will be based on the crewed capsule, there will be several notable exclusions. This includes the removal of the SuperDraco engines used for emergency launch aborts, the removal of seats and cockpit controls as well as the removal of life support systems needed for astronauts during flight to and from the outpost.
Another difference will be splashdown locations. Dragon 1 has always returned to Earth off the coast of Baja California. All Dragon 2 spacecraft are expected to use the Atlantic Ocean off the coast of Cape Canaveral as their primary splashdown locations.
Not only would this allow for crews to get back to land relatively quickly, it also means critical experiments returned from the ISS can get to laboratories more quickly.
