The HTV has an external payload bay which is accessed by the robotic arm after it has been berthed to the ISS. New payloads can be moved directly from the HTV to "Kibō"'s exposed facility. Internally, it has eight International Standard Payload Racks (ISPRs) in total which can be unloaded by the crew in a shirt-sleeve environment. After the retirement of NASA's Space Shuttle in 2011, HTVs became the only spacecraft capable of transporting ISPRs to the ISS. The SpaceX Dragon and Northrop Grumman Cygnus can carry resupply cargo bags but not ISPRs.