The new medium-sized rocket intended for missions to the International Space Station successfully completed the final ground test on Friday February 22 evening, its developer said, according to RIA Novosti.

Preliminary analysis of data from the 29-second hotfire test of the Antares launch vehicle indicate that its engines and fueling systems are fully operational, Orbital Sciences Corporation said.

The result paves the way for the inaugural flight of the rocket, which is expected to take place in early May, the Virginia-based company said on its website.

The hotfire test was initially slated for February 14, but aborted 1.5 seconds before start due to nitrogen purge issues.

The Antares, initially known as Taurus II, is an expendable launch vehicle with a maximum payload of 5,000 kilograms. It is expected to deliver Cygnus unmanned spacecraft to the International Space Station for NASA, which has no low Earth orbital spacecraft after the retirement of the Space Shuttle in 2011.