Cargo's final frontier
After a series of delays involving modifications to command software, commercial firm Space Exploration Technologies finally launched its Dragon cargo spacecraft from Florida on May 22. A planned May 7 launch date, already pushed back from dates in February and April, resulted in nothing more than a “static fire test” of the rocket engines on the launch pad. On May 19, launch officials found an engine glitch seconds before liftoff. But Dragon is now on its way, carrying a genuine payload of cargo. If this commercial venture succeeds, a new freight mode must be added to the traditional cargo roster of road, rail, air and water.
The moment is significant, and so hotly awaited, because Dragon is the first privately owned and operated spacecraft to carry out such a mission. Dragon was expected to dock with the International Space Station to unload its cargo three or four days after launch.
The U.S. government decided several years back that “routine” transportation to low-Earth orbit, if anything in space can be described that way — tasks such as supplying the ISS and launching satellites — should be doled out to contractors. This meant the Space Shuttle program, with its increasingly high maintenance costs, could be retired, and NASA could move on to develop the systems needed for exploring, and perhaps later mining, Mars and the asteroid belt.
The ISS, essentially a $100 billion research lab co-owned and operated by the U.S., Canada, Russia, Japan and Europe, is the biggest piece of hardware in space, weighing 360 tonnes. Orbiting about 390 kilometers above the Earth, it can accommodate six crew members; many scientific experiments take place on board in zero gravity. The shuttles played a key role in building and replenishing the ISS.
When the Atlantis returned to Earth for the last time in July 2011, the 30-year shuttle program came to an end, briefly leaving other nationalities in charge of resupplying the station. The European Space Agency sends up periodic Automated Transfer Vehicles via its Ariane 5 rocket from Kourou, French Guiana. The latest to make the journey, ATV-3, delivered 7.2 tonnes of key supplies in March; it was the largest shipment to date. The one-trip ATVs burn up on re-entry to the Earth’s atmosphere, as do Japanese supply capsules. A fourth ATV is currently under construction.
Russian Soyuz spacecraft make regular departures to the ISS from the Baikonur Cosmodrome in Kazakhstan with replacement crew and supplies. A Russian cargo spacecraft, Progress M-14M, made its final journey in April as scheduled, undocking from the ISS to conduct scientific experiments and falling into the Pacific Ocean nine days later. Progress freighters have completed more than 130 space missions of various types in the past 40 years, with only one failure.
In line with the long-term U.S. strategy of using private-sector spacecraft to help keep the ISS supplied, NASA awarded contracts worth a combined $3.6 billion back in 2008 to two private aerospace firms under its Commercial Resupply Services program. Hawthorne, Calif.-based Space Exploration Technologies (SpaceX) and Orbital Sciences Corp., of Dulles, Va., were contracted to haul 20 tonnes of cargo to the Space Station through 2016. SpaceX will make 12 flights with its Falcon 9 and Dragon spacecraft, while Orbital’s Antares and Cygnus spacecraft will undertake eight flights.
Ever since completing a maiden flight in December 2010, SpaceX has worked toward launching Dragon into low-Earth orbit. While in space, a robotic arm carrying a 521-kilogram payload of food, other consumables and non-critical equipment will reach out to grab the ISS, and astronauts onboard the station will offload the cargo. The plan is for Dragon to remain attached to the ISS for several weeks before returning to Earth with a 660-kilogram payload, far beyond the capacity of the Soyuz capsules. The craft will then splash down in the Pacific in order to be recovered. SpaceX ultimately intends to develop a thruster system that will allow Dragon to return to a spaceport. In two to three years, the system will be further developed so that astronauts can be transported too, a role only the Russians can currently fulfill.