Crew Dragon in the context of SpaceX Dragon 1

The Soyuz programme (/ˈsɔɪjuːz/ SOY-yooz, /ˈsɔː-/ SAW-; Russian: Союз [sɐˈjus], meaning "Union") is a human spaceflight programme initiated by the Soviet Union in the early 1960s. The Soyuz spacecraft was originally part of a Moon landing project intended to put a Soviet cosmonaut on the Moon. It was the third Soviet human spaceflight programme after the Vostok (1961–1963) and Voskhod (1964–1965) programmes.

The programme consists of the Soyuz capsule and the Soyuz rocket and is now the responsibility of Roscosmos. After the retirement of the Space Shuttle in 2011, the Soyuz was the only way for humans to get to the International Space Station (ISS) until 30 May 2020 when Crew Dragon flew to the ISS for the first time with astronauts.

The NASA Docking System is NASA's implementation of the International Docking System Standard (IDSS), an international spacecraft docking standard promulgated by the International Space Station Multilateral Coordination Board. NDS is a spacecraft docking and berthing mechanism used on the International Space Station (ISS) and the Boeing Starliner and planned to be used on the Orion spacecraft. The international Low Impact Docking System (iLIDS) was the precursor to the NDS. NDS Block 1 was designed, built, and tested by The Boeing Company in Huntsville Alabama. Design qualification testing took place through January 2017.

Using NDS, NASA developed the International Docking Adapter (IDA) to provide two IDSS-compliant docking ports on the ISS. The IDAs were delivered to the ISS starting in 2016. Each of two existing Pressurized Mating Adapters has an IDA permanently attached, so the former PMA function is no longer available for visiting spacecraft. Since 2019, visiting spacecraft that implement IDSS dock to the NDS ports on the IDAs. These include Crew Dragon, Cargo Dragon 2, and Boeing Starliner.

A launch escape system (LES) or launch abort system (LAS) is a crew-safety system connected to a space capsule. It is used in the event of a critical emergency to quickly separate the capsule from its launch vehicle in case of an emergency requiring the abort of the launch, such as an impending explosion. The LES is typically controlled by a combination of automatic rocket failure detection, and a manual activation for the crew commander's use. The LES may be used while the launch vehicle is on the launch pad, or during its ascent. Such systems are usually of three types:

• 

  A solid-fueled rocket, mounted above the capsule on a tower, which delivers a relatively large thrust for a brief period of time to send the capsule a safe distance away from the launch vehicle, at which point the capsule's parachute recovery system can be used for a safe landing on ground or water. The escape tower and rocket are jettisoned from the space vehicle in a normal flight at the point where it is either no longer needed, or cannot be effectively used to abort the flight. These have been used on the Mercury, Apollo, Soyuz, and Shenzhou capsules.
• The crew are seated in seats that eject themselves (ejection seats) as used in military aircraft; each crew member returns to Earth with an individual parachute. Such systems are effective only in a limited range of altitudes and speeds. These have been used on the Vostok and Gemini capsules, and Space Shuttle Columbia during its testing phase.
• Thrusters integrated in the capsule or its detachable service module having the same function as an escape tower, as in the case of Crew Dragon, Starliner and New Shepard.