SpaceX’s Falcon 9 rocket successfully launched from Cape Canaveral, Florida this morning, lofting the company’s Dragon cargo capsule into orbit around Earth. Bound for the International Space Station, the Dragon will bring nearly 5,000 pounds of supplies and science experiments for the station’s onboard crew. Today’s launch marks the ninth cargo resupply mission that SpaceX has done for NASA, and the eighth one to make it to orbit.

Just before the Dragon capsule successfully separated from the second stage of the Falcon 9, the first stage of the rocket landed back at Cape Canaveral. It was the second time SpaceX has landed one of its rockets on solid ground, and the fifth rocket the company has landed overall.

The Dragon capsule is set to remain in orbit for the next two days, during which it will fire its thrusters, bringing it gradually closer and closer to the ISS. NASA astronaut Jeff Williams will then use the station’s robotic arm to grab the Dragon early Wednesday morning and attach the capsule to the ISS Harmony module a few hours later.

Of the items headed Dragon is bringing to the station, the most critical piece of cargo includes an international docking adapter, or IDA. This 63-inch-wide ring will eventually be installed onto a port outside the station, allowing future commercial spacecraft to automatically dock with the ISS. It’s a crucial piece of hardware needed for NASA’s Commercial Crew Program — an initiative that tasks private companies with building and operating spacecraft that can ferry astronauts to and from the ISS. Both SpaceX and Boeing are currently developing vehicles for that program, but without the IDA, there’s no way for those vehicles to attach to the station.

There was added pressure to get this IDA to the station, too, since there was already supposed to be a docking adapter installed on the ISS. The first IDA was slated to launch summer of last year, but it was destroyed when the Falcon 9 that was carrying it disintegrated during launch. Now, SpaceX has made up for that mishap by successfully getting this IDA into space.

The IDA isn’t actually packed inside the Dragon, but is riding to space inside the Dragon’s trunk. That’s the cylindrical structure attached to the end of the capsule that holds the Dragon’s solar panels and provides support during launch. It can also be used to transport unpressurized cargo, like the IDA. Once Dragon is docked at the station, the astronauts will use the robotic arm to remove the IDA from the trunk and attach it to its intended port. The astronauts will then conduct a spacewalk later this summer to fully connect the IDA to the station.

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