SpaceX launched its Commercial Resupply Services-9 (CRS-9) cargo mission to the International Space Station at 12:45 am ET this morning on schedule from launch pad 40 at Cape Canaveral Air Force Station (CCAFS), FL. The first stage of the Falcon 9 rocket then returned to a successful landing back at a different CCAFS pad about 9 minutes later. It was the second successful SpaceX landing at CCAFS.

SpaceX CRS-9, or SpX-9, is delivering a Dragon spacecraft with 4,976 pounds (2,257 kilograms) of scientific experiments, supplies and equipment to the ISS. Dragon is scheduled to arrive at ISS on Wednesday morning.

Among the items aboard is an International Docking Adapter (IDA) that will be installed on an ISS port to enable dockings of SpaceX’s Crew Dragon and Boeing’s CST-100 Starliner commercial crew vehicles in the future. The cargo version of Dragon and Orbital ATK’s Cygnus cargo spacecraft berth, rather than dock, with the ISS. Berthing requires the ISS crew to grapple the spacecraft with the robotic Canadarm2 and install them onto ISS ports. The crew capsules need to be able to dock using their own propulsion and other systems without interaction from the ISS crew. The IDAs help enable that.

This is IDA-2. IDA-1 was destroyed on the SpX-7 failure in June 2015. A replacement, IDA-3, is being built and is tentatively scheduled for launch on the SpX-14 mission.

The IDA weighs 1,030 pounds (467 kg). The other cargo is 2,050 pounds (930 kg) of science experiments, 816 pounds (370 kg) of crew supplies, 617 pounds (280 kg) of vehicle hardware, 280 pounds (127 kg) of spacewalk equipment, 2.2 pounds (1 kg) of computer resources, and 119 pounds (54 lg) of Russian hardware.

After propelling Dragon and the Falcon 9’s second stage part of the way to orbit, the first stage turned around, fired boostback, entry, and landing burns, and successfully touched down back at CCAFS about 9 minutes after liftoff.

SpX-9 Falcon 9 first stage moments before touchdown at Landing Zone 1, Cape Canaveral Air Force Station, FL.

Snip from SpaceX live coverage, July 18, 2016 ET.

This was only the second landing on land for SpaceX. Other first stages have landed on drone ships at sea. During a briefing on July 16, SpaceX’s Hans Koenigsmann said that it is easier to land on terra firma because the pad is larger and is not moving. On the other hand, returning back to the Florida coast requires more fuel. These landings are secondary objectives — the primary purpose is launching something into orbit — and use whatever fuel remains. Clearly there was enough today. SpaceX wants to reuse the first stages to reduce launch costs. Several of the stages have been recovered so far. Koenigsmann said the one from the SpX-8 mission will be the first to refly, probably this fall, although the company has not finalized arrangements with a customer for that launch.

Dragon will remain at the ISS until August 29. It then will return to Earth, landing in the Pacific Ocean. It is the only one of the four ISS cargo spacecraft (Orbital ATK’s Cygnus, Russia’s Progress, and Japan’s HTV are the others) that can survive reentry. In this case, it will return more than 3,300 pounds (1,500 kg) of science experiments and hardware.