SpaceX completed its 33rd cargo delivery to the International Space Station early Monday, when a Dragon supply ship glided to an automated docking with more than 5,000 pounds of scientific experiments and provisions for the lab's seven-person crew.
The resupply flight is part of the normal rotation of cargo and crew missions that keep the space station operating. The Dragon spacecraft's cargo haul comprised packages of fresh food, including some 1,500 tortillas, and equipment for numerous research investigations demonstrating 3D printing in microgravity and examining how the human body responds to long-duration spaceflight.
The cargo manifest is typical of most Dragon resupply flights traveling to the International Space Station. What's different with this mission is a new rocket pack mounted inside the Dragon spacecraft's rear trunk section. In the coming weeks, SpaceX and NASA will use this first-of-its-kind propulsion system to begin boosting the altitude of the space station's orbit.
Maintaining control
"The space station's altitude slowly decays over time due to the thin amount of atmosphere still at our altitude," said Bill Spetch, NASA's operations integration manager for the International Space Station. "To counteract that drag, we must occasionally raise the altitude of the ISS."
Responsibility for maintaining the station's orbit has historically been borne by the Russian space agency, which had the sole capability to reboost the ISS after NASA retired its space shuttle fleet in 2011. Russia's Progress cargo freighters often use their own thrusters to raise the lab's altitude or steer it out of the way of space junk. What's more, Progress ships can refill propellant tanks inside the station's Russian command post, giving the outpost the ability to perform its own maneuvers when necessary.
But that is changing as NASA works with SpaceX and Northrop Grumman, the agency's other commercial cargo transport contractor, to modify their Dragon and Cygnus supply ships for reboost missions.