NASA released crew assignments for the International Space Station (ISS) through spring 2020 today. Notable by their absence are flights by the two U.S. commercial crew companies, SpaceX and Boeing. NASA had hoped that U.S. launches of ISS crews would begin this year. Instead, U.S. crew members will be staying for longer periods of time, including what will be a record-breaking mission by Christina Koch. She will remain for almost 11 months, returning in February 2020 instead of this fall.

Extending the duration of U.S. crew flights has been one option under consideration by NASA in the event the commercial crew systems were delayed. Boeing just announced another slip for its Starliner system, with the uncrewed test flight now no earlier than (NET) August 2019 and the crewed test flight NET “late 2019.” SpaceX flew the uncrewed Demo-1 test flight of its Crew Dragon system in March, but still must conduct an in-flight abort test and the crewed test flight before the system is certified for operational use.

Under the new crew rotation plan, Koch will remain on ISS for 328 days, the longest continuous mission for any female astronaut. NASA’s Peggy Whitson currently holds that record — 288 days.

Scott Kelly holds the record for the longest duration for an American astronaut: 340 days, just 12 days longer than Koch will accrue. Russian cosmonaut Valeriy Polyakov holds the world record for continuous time in space: 437 days, set in 1994-1995.

NASA astronaut Andrew Morgan also will have an “extended” mission on ISS. He will launch on July 20, 2019 and remain until “spring 2020.”

Kelly’s flight was publicized as the “Year in Space” mission although it was somewhat less than a year. He and Russian cosmonaut Mikhail Kornienko remained on ISS for that much time to allow scientists to study the longer-term effects of spaceflight on humans. ISS crews typically change every 4-6 months, but missions to Mars will take much longer than that and NASA needs data on how the human body reacts to weightlessness and other environmental factors over the long term. NASA said today that Koch and Morgan will contribute more data to that research with their extended missions.

The point is, however, that NASA wants to ensure that Americans remain aboard the ISS at all times, but must rely on Russia to take them back and forth. NASA has not been able to transport people to the ISS since the space shuttle was terminated in 2011. The commercial crew systems are intended to restore the ability to launch “American astronauts from American soil on American rockets.” Until then, NASA must pay Russia. Its contract was set to expire soon, but the agency recently announced that it will purchase two more seats as insurance against further commercial crew delays.

The usual ISS crew complement is six and six are there now: three Americans (Koch, Anne McClain, and Nick Hague), two Russians (Oleg Kononenko and Alexey Ovchinin), and one Canadian (David Saint-Jacques).

The crews travel back and forth on Russian Soyuz spacecraft, which can accommodate three people, so the crew rotations are a constant ballet of comings and goings. The plan announced today includes the flight of a “space tourist” from the United Arab Emirates (UAE), who will remain for a short duration mission.

June 24: McClain, Saint-Jacques, and Kononenko return to Earth.

July 20: Andrew Morgan (USA), Luca Parmitano (ESA/Italy), and Alexander Skvortsov (Russia) launch to ISS.

September 25: Jessica Meir (USA), Oleg Skripochka (Russia), and Hazzaa Ali Almansoori (UAE) launch to ISS.

October 3: Hague, Ovchinin, and Ali Almansoori return to Earth.

February 2020: Koch, Parmitano and Skvortsov return to Earth.

Spring 2020: Morgan, Meir and Skripochka return to Earth.

Other crew assignments are yet to be announced.

The SpaceX crewed test flight could still take place in this time frame. This schedule is for crew rotations and nominally the test flight would not be used for a crew rotation. NASA has decided, however, to use Boeing’s crewed test flight for an “extended mission” so today’s announcement suggests the agency does not expect that to take place until 2020 rather than “late 2019.”

Meanwhile, Northrop Grumman launched a cargo mission to the ISS today from the Mid-Atlantic Regional Spaceport (MARS) at Wallops Flight Facility, VA. The NG-11 Cygnus spacecraft is loaded with 7,600 pounds of supplies, equipment, and scientific experiments for the ISS crew. It will arrive at the ISS early Friday morning.

Northrop Grumman and SpaceX launch “commercial cargo” missions to the ISS under contract to NASA. The next SpaceX cargo launch, SpX-17, is scheduled for April 26. Russia just launched one of its cargo missions to the space station, Progress MS-11, on April 4. When contemplating human exploration of the Moon and Mars, it is important to bear in mind how many supplies are needed to support the crews and their homes in space.