The International Space Station (ISS) is a permanently crewed, multinational space laboratory in low-Earth orbit. Continuously staffed since 2 November 2000, it is the longest-running space station program of all time, and consistently cited among the world's most ambitious engineering projects. Boasting a pressurized volume of 932 cubic meters, the ISS has an interior space equivalent to 24 shipping containers and with regular supply missions can indefinitely host up to 7 crewmembers.
The station is typically staffed by dual 3-person crews assigned to overlapping six-month missions, with each unique complement of 6 people composing a numbered Expedition (each 3-person crew will serve on two Expeditions during their stay). NASA and Roscosmos have also experimented with one-year crews.
In the Integration Building at the Baikonur Cosmodrome in Kazakhstan, ISS crew members Christina Koch of NASA (left), Alexey Ovchinin of Roscosmos (center) and Nick Hague of NASA (right) pose for pictures in front of the Soyuz MS-12 spacecraft March 10 during final pre-launch inspections.
Drew Morgan of NASA (left), Alexander Skvortsov of Roscosmos (center), and Luca Parmitano of the European Space Agency (right) pose for pictures in front of their Soyuz MS-13 booster rocket on 16 July 2019 at the Baikonur Cosmodrome.
The station's altitude averages just over 400 kilometers. Earth's atmosphere continually drags it down. Mission controllers reboost its altitude regularly using either engines on the Zvezda service module or on visiting spacecraft. The station’s high, 51.64-degree orbital inclination carries it over 90 percent of the world's population, and its large size and reflective solar panels make it easy to spot from even brightly lit cities. You can sign up to receive text or email alerts from NASA when the station is visible from your location.
The ISS also offers a means of cooperation for five of the world’s major space agencies: NASA, Roscosmos, ESA, JAXA, and CSA. Station astronauts regularly videoconference with students around the world.
Dimensions: 109 meters across the central truss, 73 meters across the pressurized modules
Power: The station’s primary power source is 8 Solar Array Wings (SAWs), each consisting of 2 retractable blankets of dual-sided solar cells. The wings actuate to follow the sun on 2 axes as the station orbits the Earth, capturing both direct and reflected sunlight. The maximum beginning-of-life output of each wing is 31 kW, creating a theoretical max of 248 kW from the entire system. Power from the SAWs is shunted to lithium-ion batteries. There are also smaller solar arrays on the Russian Zarya and Zvezda modules; Zarya supplies an average of 3 kW, while Zvezda supplies a maximum of 13.8 kW.
Time zone: The space station’s official time zone is UTC, a compromise between NASA’s mission control in Houston (CST, UTC-6) and Russia’s mission control near Moscow (MSK, UTC +3).
The Russian Soyuz is currently the only vehicle able to carry astronauts to the ISS, following the retirement of the space shuttles in 2011. In September 2014, NASA selected SpaceX and Boeing for space station crew transportation, the culmination of a plan to return crewed launch capability to the United States.
Soyuz TMA-15M departs the International Space Station on 11 June 2015 carrying NASA's Terry Virts, ESA's Samantha Cristoforetti, and Roscosmos' Anton Shkaplerov.
The Soyuz has been in service since 1967. Launching on the identically named Soyuz rocket, it has 3 sections: a pressurized descent module that carries up to 3 crew members during liftoff and landing, a pressurized orbital module used on orbit for storage and extra crew space, and a separate, inaccessible service module that houses the propulsion, solar arrays, and other instrumentation. The capsule is not reusable.
Pressurized space: 10.5 cubic meters (6.5 cubic meters in orbital module, 4 cubic meters in descent module)
Mass: 6,800 kg dry mass (2,900 kg descent module, 1,300 kg orbital module, 2,600 kg service module)
Crew Dragon holds position 20 meters away from the International Space Station's forward docking port on 3 March 2019, during its inaugural test flight.
Derived from SpaceX's Dragon cargo vehicle that debuted in X, Crew Dragon consists of a pressurized capsule capable of hosting up to 7 astronauts, and an unpressurized trunk for cargo space as well as power via a solar array-lined exterior. Crew Dragon launches on Falcon 9; the trunk is jettisoned before vehicle reentry. The capsule is designed to be reusable.
Pressurized space/dimensions: Full stack 8.23 meters tall. Pressurized capsule 4.88 meters tall, 3.96 meters in diameter. Unpressurized trunk 3.66 meters tall, 3.66 meters in diameter.
Propulsion: 16 Draco maneuvering thrusters, 8 SuperDraco engines (4 sets of 2) used for launch abort, including a late-stage orbital insertion if necessary.
Major differences from Cargo Dragon include the SuperDraco engines, an articulating nosecone to protect the vehicle's docking hardware during launch and reentry, fins used for stabilization in the event of a launch abort, and built-in rather than fold-out solar panels on the trunk, thanks to a lower overall power budget than Cargo Dragon. Starting with CRS-21 around 2020, Crew Dragon will replace Cargo Dragon for uncrewed cargo resupply flights to the ISS. | DM-1 post-FRR briefing
Boeing CST-100 Starliner
An artist's rendering of Boeing's Starliner spacecraft.
Starliner consists of a pressurized capsule capable of hosting up to 7 astronauts, and a service module for propulsion and power via solar panels on the bottom that provide 2,900 watts of power. Starliner launches on the Atlas V, and will eventually launch on Vulcan. It can touch down on land using airbags; the capsule is designed to be reusable.