This weekend, the U.S. space company, Space Exploration Technologies (SpaceX), started by Internet entrepreneur Elon Musk will attempt to send its unmanned Dragon capsule to dock with the International Space Station.

The success of that mission will profoundly affect American access to space. For one thing, it will mean that the U.S. can once again use one of its own spacecraft to transport goods to and from the space station. After the Space Shuttle was retired, Russia's Progress spacecraft, along with Europe's Automated Transfer Vehicle (ATV) and Japan's H-II Transfer Vehicle (HTV), have been carrying fuel, food and other supplies needed on the space station.

But once their task was completed, those craft were simply filled with rubbish from the space station and allowed to burn up in the atmosphere during re-entry. Dragon, on the other hand, will be able to bring cargo safely back to the earth as well. In the forthcoming mission, for instance, it will return over 600 kg of goods, including some used hardware and samples from a materials processing experiment.

For the U.S. space agency, the National Aeronautics and Space Administration (NASA), a successful Dragon mission will vindicate its efforts to let private companies take on the task of transporting humans and cargo to orbits around Earth.

Dragon and the Falcon 9 rocket that will launch it have both been designed to meet NASA safety requirements for taking astronauts as well. A common design for the capsule's cargo and manned configurations meant that critical safety features could be tested in the course of unmanned missions, the company pointed out. Currently, crews are wholly dependent on Russia's Soyuz capsule and rocket to reach the orbiting outpost.

But SpaceX's vision goes beyond providing transportation services for the International Space Station.

“The cost and reliability of access to space have barely changed since the Apollo era over three decades ago,” observed Mr. Musk, who is the company's CEO and also its chief designer, when he addressed a Presidential commission in 2004. SpaceX believes that its rockets will provide “breakthrough advances in reliability, cost, and time to launch.”

To meet those goals, the company has configured its rockets around a single engine that can then be turned out in large numbers. Such high-volume engine production allowed better process control, resulting in much higher quality, it said.

To this end, it developed the Merlin engine that runs on liquid oxygen and kerosene. It also took a design concept from the Soviet space programme – the use of large numbers of a less powerful engine that can be developed more easily. Falcon 9's first stage uses a cluster of nine Merlin engines. Even if one of those engines failed during flight, the company claims that the rocket will be able to successfully complete its mission.

When Falcon 9 lifts off, those engines together produce more thrust than four Boeing 747s. But even so they do not match the power of just one of Saturn V's F-1 engines, five of which fired in unison to take men to the Moon. In addition, Falcon 9's second stage uses a single Merlin engine. In April last year, SpaceX unveiled its Falcon Heavy configuration. This rocket will have “more payload capability that any [launch] vehicle in history apart from the Saturn V,” said Mr. Musk at a press conference. The rocket could see its first flight next year.

Falcon Heavy will cluster three of its predecessor's first stages. A total of 27 upgraded Merlin engines will therefore fire at lift-off. As the rocket climbs, propellants from boosters on either side will be fed to the core, keeping the latter's tanks filled. Once empty, the boosters separate and fall back to earth while the engines of the core stage continue to operate.

Mr. Musk believes that the company could launch about 10 each of Falcon 9 and Falcon Heavy annually in the coming years. With Falcon Heavy, a return to the Moon, a Mars sample return mission or a visit to an asteroid would become possible, Mr. Musk remarked.

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