Antares lifts off (Image: NASA, Bill Ingalls)

Watch out, SpaceX, there’s a new commercial rocket in town. After a few delays due to weather and a technical glitch, the Antares launch vehicle lifted off on its maiden flight on 21 April. The launch sets the stage for a second company to begin resupply missions to the International Space Station.

Since the space shuttles retired in 2011, NASA has been contracting with private firms to deliver cargo – and soon hopefully astronauts – to the space station. California-based SpaceX became the first private firm to officially resupply the ISS last October. Its Falcon 9 rocket lifted off from Cape Canaveral in Florida carrying a Dragon capsule filled with cargo and science experiments.

Antares, built by spaceflight company Orbital Sciences of Dulles, Virginia, lifted off from the Mid-Atlantic Regional Spaceport on Wallops Island, Virginia, at 22.00 GMT.


Swan song

Antares was designed to deliver the company’s Cygnus cargo craft to the ISS. For the test flight, the rocket climbed high into a clear blue sky carrying a mock cargo ship with the same mass and dimensions as Cygnus, to avoid putting the real thing at risk.

About 10 minutes into the mission, the Cygnus dummy successfully separated from the rocket and went into a temporary orbit. It will fall back to Earth in about two weeks and disintegrate upon re-entering the atmosphere. The dummy contains instruments that will collect data about the launch, to be transmitted back to mission managers before re-entry.

When the real Cygnus flies, it will carry about 2 tonnes of cargo per trip. The Dragon capsule can deliver a payload of 3 tonnes. The two craft have comparable capabilities, claims Mark Pieczynski of Orbital Sciences. But while Dragon can return from its missions loaded with cargo, no Cygnus craft will ever make it back to Earth. These craft will leave the ISS filled with trash and will burn up in Earth’s atmosphere.

Orbital’s agreement with NASA includes this trial launch and a full demonstration mission in which the rocket will bring a real, loaded Cygnus craft to dock with the ISS, perhaps as early as June. If all goes well, the company is contracted to make a total of eight cargo missions to the station over the next three or four years.