The first International Docking Adapter headed to the International Space Station on Sunday will be a physical connecting point for spacecraft, but for NASA it will be a metaphorical gateway to a future in which crews go to the station aboard America's first new, human-rated spacecraft since the space shuttle.

The adapter, designated IDA-1, was built by Boeing and has been loaded into the trunk of the SpaceX Dragon spacecraft that will rocket into orbit aboard a Falcon 9 rocket on the company's seventh commercial resupply mission to the orbiting laboratory. CRS-7, as the mission is called, is slated to launch Sunday at 10:21 a.m. EDT from Cape Canaveral Air Force Station's Space Launch Complex 40.

Astronauts will work inside and outside the station to install the docking adapter on the pressurized mating adapter at the forward end of the Harmony module. Weighing just over 1,000 pounds, the first IDA will be moved out of the Dragon using the space station's robotic arm and will be temporarily stowed on the external station structure.

Spacewalking astronauts and robotics controllers will later attach IDA-1 to the Pressurized Mating Adapter at the forward end of the Harmony module and connect cables and the other relevant systems to make the adapter a permanent part of the station.

The second IDA is scheduled to be delivered to the station on the ninth SpaceX commercial resupply mission and will be installed on another Pressurized Mating Adapter that will be located on the space-facing side of the Harmony module.

Boeing's CST-100 and SpaceX's Crew Dragon spacecraft will dock at the adapters in the near future when bringing astronauts to the station as part of NASA's Commercial Crew Program.

The adapters were built to the International Docking System Standard, which features built-in systems for automated docking and uniform measurements. That means any destination or any spacecraft can use the adapters in the future - from the new commercial spacecraft to other international spacecraft yet to be designed.

The adapters also include fittings so power and data can be transferred from the station to the visiting spacecraft. The work by private companies to take on low-Earth orbit missions is expected to free up NASA's resources for future missions into deep space with astronauts in the Orion crew capsule launching on the Space Launch System Rocket to prepare for future journeys to Mars.

"It's really opening up a new era for commercial crew support to ISS," said Mark Ortiz, Boeing's project manager for the two IDAs. "The IDA enables flexibility for multiple commercial and international vehicles to dock to ISS and opens the door to a new international standard."

It took international and national teams working together to construct the IDAs. Parts from companies in 25 states were assembled to make the adapters, which measure about 42-inches tall and about 63-inches wide each. The Russian company RSC-Energia made the primary structures of the IDAs. Docking targets, laser retro-reflectors and related systems are arrayed around the outer perimeters to give them an outer diameter of about 94 inches. NASA's Johnson Space Center also collaborated on the design, Ortiz said.

The systems and targets for IDA-1 were put through about a month of tests at Kennedy's Space Center's Station Processing Facility before being loaded for launch. The targets are much more sophisticated than previous docking systems and include lasers and sensors that allow the station and spacecraft to talk to each other digitally to share distance cues and enable automatic alignment and connection. Think of it as a car that can park itself.

"We set the hardware up and had the folks from Boeing and SpaceX come over and do some alignment checks and testing so they would know their systems would work," said Steve Bigos, project manager for orbital replacement unit processing at Kennedy. "There was a lot of new technology, so it was very interesting."

The team then packaged it for launch and put it in the configuration it will need for the ride into space and placement on the station.

"I might've expected more issues with everybody coming in to look at it, but the teams worked together really well," said Curt Horanic, NASA's operations lead for the work. "The commercial world and the NASA world all worked well together, and in the world of changing cultures it all seems to be molding together."