NASA's nascent commercial orbital transport system (COTS) is expected to go live late next year under a $3.5 billion programme. The programme's aim is to provide more than half of the cargo needed to run the International Space Station in the post-Space Shuttle era.

The agency on 23 December announced that Space Exploration Technologies and Orbital Sciences won commercial cargo resupply services (CRS) contracts valued at $1.6 billion and $1.9 billion, respectively.

Each must deliver 20,000kg (44,000lb) of a to-be-determined mix of pressurised and unpressurised cargo to the station from 2010 until 2015 under the contracts. NASA's payments are to be made in relation to a series of milestones to be completed.

A third company, PlanetSpace, which is teamed with Alliant Techsystems, Boeing and Lockheed Martin Space Systems, failed in its bid for a CRS contract.

SpaceX, which won a COTS contract in 2006, plans to use its new Falcon 9 booster topped with a Dragon capsule for three COTS demonstrations this year and next, with the first of 12 CRS launches starting in the fourth quarter 2010. Falcon 9 is based on SpaceX's smaller Falcon 1, which successfully reached orbit last September.

Steve Davis, SpaceX's lead systems engineer for Dragon, says the Dragon-Falcon 9 combination will be capable of lifting 2,550kg of cargo to the station, divided between the main pressurised module and a detachable "trunk" below. SpaceX says the Dragon can bring as much as 3,000kg cargo back to Earth.

SpaceX is building the system to be two-fault tolerant to achieve man-rated status if NASA later decides to contract out the shuttling of crews to the station under CRS. With a crew capability of seven, Davis says each Dragon passenger will have 1.5m3 (45.8ft3) of space, 15% more per person than in Russia's Soyuz capsule. Chief among the challenges with gaining a manned rating will be to build an escape system for the Dragon, says Davis.

SpaceX is also studying, at NASA's request, using a Dragon as a "life boat" replacement for, or supplement to, Russia's Energia-built Soyuz capsules for station egress. Davis says the Dragon life boat, built in a year and to cost $2-3 million more than the basic pressurised version, would be delivered in a Space Shuttle's cargo bay before the fleet is decommissioned.

 Cape Canaveral Space X
 © Space X

Forthcoming test flights under the COTS programme will reveal if SpaceX's CRS ambitions are within its means. The company is preparing to launch its prototype Dragon-Falcon from Complex 40 at the Kennedy Space Center in June. Davis says the first Dragon, sans solar array and thermal system, will orbit the Earth three times at an inclination of 34° before re-entering the atmosphere and splashing down under parachute control in the Pacific Ocean up to 483km (260nm) off the coast of California.

The second launch, late this year, will include an ISS fly-by to within 10km. The third mission, in the first quarter 2010, will see the Dragon docked to the ISS via the station's remote manipulator arm.

Orbital Sciences, which joined COTS in February 2008, will have only one test launch of its new liquid fuelled Taurus II booster and Cygnus orbital manoeuvring capsule in late 2010 before sending its first of eight CRS contract launches into orbit in late 2011. The Cygnus is designed to carry 2,300kg to the ISS and return 1,200kg to Earth.

As for a back-up plan if one of both contractors fail, NASA associate administrator for space operations Bill Gerstenmaier says NASA has the option of using another contractor "at a later date" and could also decide to prolong use of the Space Shuttle, an option NASA administrator Michael Griffin says will cost $3 billion a year for two flights to the ISS. The "ultimate" fallback, says Gerstenmaier, would be to scale back ISS operations and crew, as was done after the Space Shuttle Columbia loss in 2003.

Source: Flight International