Tim Furniss / London

Agency is considering its escape vehicle options in a bid to double crew numbers and increase scientific work

NASA is considering the use of two Russian Soyuz TM Crew Return Vehicles (CRV) on the International Space Station (ISS) in an effort to restore crew numbers to original plans and allow an increase in scientific work.

The scheme would double the current ISS crew to six people. With only one Soyuz TM attached, it is not worth the risk of increasing crew size, says Tommy Holloway, ISS manager. An emergency evacuation with a single Soyuz TM could only be made by three crew.

Six-person missions supported by two Soyuz TMs are possible, but could not be flown for much longer than a month, according to Hollaway.

Working normal ISS shifts of 90 days would pose logistical problems, particularly by increasing the required number of supporting flights of Russian Progress tankers to provide equipment, food and water.

Another option being considered by NASA is the use of a Space Shuttle orbiter equipped with an Extended Duration Orbiter (EDO) multi-fuel cell system, which could support missions by up to 10 crew for about 20 days.

The studies follow NASA decisions to cancel a US-built CRV and a habitation module to stem ISS budget overruns. The two items would have helped support up to seven crew.

Budget constraints have also caused NASA to reduce science work by 40%. The present Soyuz studies are aimed at restoring some of the work without incurring heavy additional costs.

The third expedition crew for the ISS will be launched on 9 August on the STS105 Endeavour mission. This will also deliver equipment and supplies and bring back the second crew, which has been on board since April.

In another cost-cutting move, the Space Shuttle orbiter Columbia could be mothballed on a "ready-to-be-reactivated" basis as part of NASA's response to a projected $800 million budget Shuttle programme shortfall to 2007. Other measures being considered are cancelling some planned Space Shuttle upgrades and closing a number of test facilities.

Columbia, which has flown 26 missions since inaugurating the programme with STS1 20 years ago, is the only orbiter not equipped to dock with the ISS and has been scheduled for just two definite flights next year - a Hubble Space Telescope refurbishment mission and a science research flight. Mothballing Columbia would leave NASA with three operating Shuttles.

On 31 July, NASA set up an 18-strong ISS Management and Cost Evaluation Task Force under Thomas Young.

Source: Flight International