Tim Furniss/LONDON

NASA has admitted for the first time that full assembly of the International Space Station (ISS) will not be completed until 2006 - two years later than forecast when the first element was launched in 1998 and 10 years later than planned when the project was first announced in 1984.

The US space agency has adopted what Robert Cabana, astronaut and ISS programme manager, describes as a schedule that is more realistic. "We have begun to rethink the entire approach to the assembly process," he says.

NASA says it is beginning to reap the benefit of Russia's expertise and experience in long-duration spaceflight operations and its "marathon approach" to space exploration, as opposed to the USA's "sprinter's approach", born from the Apollo days and continuing with the short-duration Space Shuttle missions.

The station currently comprises three modules, Unity, Zarya and Zvezda, and a Progress unmanned tanker. Although Russia's financial and technical problems have caused some delays to the ISS already and are threatening to cause more, there have been problems on the US side as well.

Several NASA components have been delayed by new technical problems, including the Destiny laboratory module, the launch of which is being delayed for a further 30 to 60 days from January 2001as a result of computer and command and control problems.


Meanwhile, the Space Shuttle Discovery (STS 92) was rolled out to launch pad 39A at Kennedy Space Center on 11 September, as its sister ship Atlantis was docking with the ISS on mission STS 106.

Discovery is scheduled to fly the much-delayed STS 94 mission on 5 October to carry the first section of the truss framework that will provide the backbone of the station. STS 92 will also provide another docking port to the station.

The launch of Atlantis from pad 39B on 8 September began a frenetic campaign of Shuttle missions which should see up to 10 flights before the end of next year.

After docking with the ISS, two crewmen, an American and a Russian, made a 6h EVA on 10 September to fix a magnetometer to the outside of the 13-storey space station, opened the aperture of a manual docking target device, plugged external cables between Zarya and Zvezda and installed an EVA foot restraint to be used during later maintenance spacewalks.

With the EVA work complete, the STS 106 crew entered the ISS on 11 September to begin preparing the station for occupation by early November. The mission has been extended by a day to allow the crew to transfer 2,760kg (6,080lb) of equipment into the three modules.

Atlantis had just a 150s launch window for its flight from the Kennedy Space Center on 8 September. Traditionally, windows for missions to the ISS (and previously to Mir) have been five minutes long. By launching within a 150s window, the Shuttle saves fuel, which would be useful if one of the main engines failed during launch, when the Shuttle's Orbital Manoevering System could be required to complement the remaining two main engines. Launching later in a five-minute launch window results in using more propellant to reach the required orbit.

Source: Flight International