A SpaceX Dragon cargo capsule met up with the International Space Station (ISS) on Saturday (July 16), delivering more than 5,800 pounds (2,630 kilograms) of supplies to the orbiting lab.
The robotic Dragon launched atop a two-stage Falcon 9 rocket on Thursday night (July 14) from NASA’s Kennedy Space Center in Florida. The Falcon 9 delivered Dragon to low Earth orbit, and the rocket's first stage came back down for a successful landing on the SpaceX droneship A Shortfall of Gravitas.
Dragon's orbital chase ended Saturday: The capsule docked with the ISS at 11:21 a.m. EDT (1521 GMT), while the two spacecraft were flying 267 miles (430 kilometers) above the South Atlantic.
The current mission is SpaceX’s 25th cargo flight to the ISS for NASA, so it's known as CRS-25. (CRS stands for "commercial resupply services.") The number has increased at a slow but steady pace of about two per year since the company’s first operational ISS cargo mission in 2012.
SpaceX’s overall launch cadence is much higher, of course: CRS-25's liftoff was the 30th Falcon 9 launch so far this year. In contrast, SpaceX launched just 31 missions in all of 2021. According to Benji Reed, SpaceX's senior director of human spaceflight, the company is poised to double that number by the end of this year.
"It kind of blows my mind," Reed told reporters during a teleconference shortly after Thursday night's launch. "To think that we've launched three Dragons to the station already this year is pretty cool," Reed added, "including the first all-commercial mission to station and a NASA crew mission as well."
The other two Dragon missions that lifted off this year — both in April — were crewed. One, called Ax-1, carried paying customers to the orbiting lab on a flight organized by Houston company Axiom Space. The other was Crew-4, SpaceX's fourth contracted astronaut mission for NASA.
About half of the weight that Dragon hauled to the ISS on CRS-25 is dedicated to scientific research. The mission is contributing to nearly 40 ongoing research projects taking place on the orbital lab and dropped off a handful more, NASA officials said.
One study, from the European Space Agency and the University of Florence in Italy, is investigating the effects of microgravity on the healing process of sutured wounds. Another, from the University of California, San Francisco, will study the immune system’s relationship to aging and the body’s ability to heal itself. There’s also an investigation to study a special type of biopolymer concrete, which could aid the search for future construction materials on the moon.
Loaded in Dragon’s trunk, the EMIT experiment — short for the Earth Surface Mineral Dust Source Investigation — will be pulled from its stow using the ISS’s robotic arm and mounted to the ExPRESS Logistics Carrier 1, an exposed external payload bay used for experiments and storage. EMIT will spend the next year studying the mineral composition of dust in Earth’s arid regions to help scientists better understand the planet’s global climate system.
Some of the CRS-25 cargo, while not part of other ongoing investigations, serves as a symbol of the science that keeps everyday life on the space station going — and also highlights how miraculous it is that we can operate a scientific laboratory in space at all. Dina Contella, NASA's operations integration manager for the ISS, highlighted other hardware packed aboard Dragon.
"One item is a spare dose pump, which is critical for the toilet," Contella said in Thursday’s press call. Dose pumps are used to treat urine prior to the filter and reclamation process to convert it back into potable water — in case you forgot that there’s no water in space and astronauts have to drink their own recycled pee.
"Also, we've launched some brine processor assembly bladders," Contella said. "These allow us to recover even more water from the urine effort [than] normal processing. So the new bladders further increase our ability to reclaim as much water as possible." She added that two filters for the station’s potable water dispensers were also included in the Dragon's manifest.
Dragon is expected to remain docked to the ISS for about a month and be packed with gear from the station before returning to Earth with a splashdown off the coast of Florida sometime in mid-August.
Editor's note: This story was updated at 11:55 a.m. EDT on July 16 with news of the successful docking.