NASA's commercial partner Orbital ATK pulled off the first major test of its new, upgraded rocket yesterday. The main engines on the vehicle, called the Antares, were ignited for 30 seconds as the rocket was held down on a launch pad at the Mid-Atlantic Regional Spaceport in Virginia. This is known as a hot fire test, and early signs indicate that it was successful, Orbital says. If confirmed, that means that Orbital ATK's upgraded Antares is ready for its first commercial cargo flight to the International Space Station, scheduled for sometime this July.

Orbital ATK has spent the last year and a half refurbishing the Antares, after a previous version of the rocket exploded during a launch in October 2014. The company ultimately determined that the explosion began in the rocket's AJ26 engines — refurbished Soviet-era engines made by Aerojet Rocketdyne. There's been some debate as to whether poor manufacturing of the engines were to blame or if the crash was caused by something else, like foreign debris getting into the hardware. Despite this uncertainty, Orbital still opted to replace the AJ26 engines on the Antares with RD-181 engines, made by the Russian manufacturer NPO Energomash.

The main goal of yesterday's hot fire test was to see if these new engines integrated well with the rest of the Antares and if the system operated well on the launch pad. "Early indications show the upgraded propulsion system, core stage, and launch complex all worked together as planned," Mike Pinkston, Orbital ATK's general manager and vice president of the Antares program, said in a statement. Though the test seems to have gone well, Orbital engineers will continue to look over the data from the test for the next two weeks to make sure everything worked as expected.

A fully functioning Antares rocket means that Orbital can start launching cargo to lower Earth orbit using its own vehicles again. Orbital holds a contract with NASA to periodically resupply the International Space Station, by launching the company's Cygnus cargo capsule on top of the Antares. But after the 2014 accident, the Antares was grounded while Orbital figured out how to replace the vehicle's engines. In the meantime, the company resupplied the ISS twice by launching the Cygnus on top of two Atlas V rockets made by the United Launch Alliance.

The flight in July will mark the first launch of the newly upgraded Antares vehicle. If successful, it will also be Orbital's sixth cargo mission overall to the ISS. But the Antares that was tested yesterday won't be the one to fly in July. The vehicle that underwent the hot fire will undergo further reconditioning before it's launched on another cargo supply mission later this year. The Antares rocket that will be used for the July mission is in final stages of "integration, systems testing, and check-out," according to Orbital. The company has yet to announce an exact date for the launch.