Space traffic jam up at International Space Station (ISS)

After months of delays, mission managers are conducting one final review to make sure the space shuttle Discovery, its six-astronaut crew, and the conditions at its destination – the International Space Station – are in order for the launch of Discovery’s on her 39th and final flight. The shuttle is currently slated to lift off on Thursday, Feb. 24. 

A big item on the review docket is whether adjustments need to be made to Discovery’s launch schedule to accommodate other cargo craft heading to the orbiting outpost.

The European Space Agency’s Automated Transfer Vehicle-2 launched Wednesday (Feb. 16) from the northeast coast of South America after a one-day delay due to a technical glitch. The ATV-2, called the Johannes Kepler, is now in the midst of an eight-day journey to the space station to deliver about 7.1 tons (6,400 kilograms) of supplies.

Discovery is targeted to liftoff from NASA’s Kennedy Space Center in Cape Canaveral, Fla. on Feb. 24, the same day that the ATV-2 Johannes Kepler is now scheduled to arrive and dock at the space station.

Artist impression of ATV docking with ISS.

European Space Agency ATV

Initially, NASA officials thought the space traffic jam would force mission planners to delay Discovery’s launch by one day – to Feb. 25. But, NASA officials announced Wednesday (Feb. 16) via Twitter that the launch of Discovery’s STS-133 mission will not necessarily be moved. This was also confirmed early on in today’s meeting, where live updates are being provided through Twitter.

Last week, space shuttle program managers met and unanimously agreed to proceed toward the orbiter’s targeted launch. Officials also discussed the possibility of adding a bonus photo session to the flight, in which the Russian Soyuz capsule will undock from the space station and fly around to snap photographs of Discovery while the ship is docked to the fully completed orbiting lab.

The unique photo opportunity is being discussed during today’s Flight Readiness Review (FRR), but the latest Twitter update from the meeting confirmed that a final decision on the matter will not be made prior to Discovery’s launch.

“All partners will have a vehicle docked to ISS during STS-133 – decision for Soyuz fly about for pics will be made during flight,” NASA officials said via Twitter.

Also docked at the ISS is the H-II Transfer Vehicle (HTV), nicknamed Kounotori (Oriental Stork or White Stork), is an unmanned resupply spacecraft used to resupply the Kibō Japanese Experiment Module (JEM) and the rest of the International Space Station (ISS). The Japan Aerospace Exploration Agency (JAXA) has been working on the design since the early 1990s. The first mission, HTV-1, was originally intended to be launched in 2001. It lifted-off at 17:01 UTC on September 10, 2009 on an H-IIB launch vehicle.

HTV is about 10 m long (including maneuvering thrusters at one end) and 4.4 m in diameter. Total mass is 10.5 tonnes, with a 6,000 kilograms (13,000 lb) payload.  HTV is a larger and simpler vehicle than the Progress spacecraft currently used by Russia to bring supplies to the station, since it does not have a complex docking and approach system. Instead, it will be flown just close enough to the station to allow capture by Canadarm2, which will pull it to a berthing port on the ISS Harmony module.

The Progress is a Russian expendable freighter spacecraft. The spacecraft is an unmanned resupply spacecraft during its flight but upon docking with a space station it allows astronauts inside, hence it is classified manned by the manufacturer.  It was derived from the Soyuz spacecraft, and is launched with the Soyuz rocket. It is currently used to supply the International Space Station, but was originally used to supply Soviet space stations for many years. There are three to four flights of the Progress spacecraft to the ISS per year. Each spacecraft remains docked until shortly before the new one, or a Soyuz (which uses the same docking ports) arrives. Then it is filled with waste, disconnected, deorbited, and destroyed in the atmosphere. Because of the different Progress variants used for ISS, NASA uses its own nomenclature where “ISS 1P” means the first Progress spacecraft to ISS.

As mentioned above also docking at the ISS will be the Automated Transfer Vehicle or ATV which is an expendable, unmanned resupply spacecraft developed by the European Space Agency (ESA).  ATVs are designed to supply the International Space Station (ISS) with propellant, water, air, payload and experiments. In addition, ATVs can reboost the station into a higher orbit.

Jules Verne ATV at bottom of photo docking at ISS.

With all this action the following spacecraft will all be docked at the ISS at the same time: the Space Shuttle Discovery, The European Space Agency Kepler ATV, Russian Progress supply vehicle, Russian Soyuz-TMA capsule and Japan’s H-II Transfer Vehicle.  Five spacecraft hovering around the Space Station all at once.  They are going to need a traffic cop up there to keep everything straight.  m

Idea for this post provided by D.N.