The next hot fire attempt for the Antares rocket's first stage could come within a week, leading to the privately-developed launcher's first test flight in early April, the chief executive of Orbital Sciences said Thursday.

Photo of the Antares first stage on the launch pad at Wallops Island, Va. Credit: NASA/Wallops Flight Facility
 
"After a preliminary overnight review of the data from the hot fire test attempt on February 13, Orbital's Antares team has identified low pressurization levels of a 'nitrogen purge' of the aft engine compartment as the reason the Antares flight computer, acting as designed, aborted the test with about 1.5 seconds left in the countdown," the Dulles, Va.-based company said in a statement.

The company said all other systems functioned normally, both on the Antares first stage and the launch pad at the Mid-Atlantic Regional Spaceport at Wallops Island, Va.

"Based on a preliminary assessment on the cause of the scrub, it looks like the turnaround work to prepare for another test will be fairly straightforward," said David Thompson, Orbital's chairman and CEO, in a quarterly conference call Thursday with investment analysts. "I'm hopeful that we'll be ready for another try within a week."

The hot fire test will include a 29-second firing of the Antares first stage's two AJ26 engines. The kerosene-fueled engines will ramp up to 680,000 pounds of thrust, testing the integrity of the first stage, launch complex and the dual-engine configuration for the first time.

Following the hot fire, engineers will remove the Antares first stage from the seaside launch pad and return it to Orbital's horizontal integration facility, where a full-up two-stage Antares rocket is nearly ready for launch. The full-up Antares will roll out to the launch pad for the rocket's first test flight.

"A successful outcome of the hot fire test will clear the way for the program's next big milestone, the long-awaited first flight, which will use the second Antares vehicle," Thompson said. "Subject to completing pad refurbishment and vehicle checkout, we're planning to conduct the test flight in early April."

Orbital Sciences, with up to $288 million in funding from NASA, is developing the Antares rocket and the Cygnus spacecraft to deliver supplies to the International Space Station. NASA and Orbital have a $1.9 billion Commercial Resupply Services contract for eight operational robotic logistics missions through 2016.

Thompson said the second Antares flight could occur in June or July, assuming a successful outcome of the test launch, which will carry a dummy payload into orbit along with several small CubeSat satellites.

This summer's launch will send Orbital's first Cygnus spacecraft into orbit on a NASA-sponsored demonstration mission to the International Space Station.

If the Cygnus demo flight is successful, Orbital could begin its eight-mission operational resupply manifest in the fall, Thompson said.

Orbital Sciences and SpaceX were contracted by NASA in 2008 for eight and 12 cargo flights, respectively. SpaceX accomplished its first operational mission to the space station in October, and the next launch is scheduled for March 1.

SpaceX and Orbital Sciences are scheduled to complete their resupply missions in 2016, and NASA will need to procure further cargo missions to service the space station through at least 2020, the outpost's current targeted retirement date. Thompson said he expects negotiations for a follow-on Commercial Resupply Services contract to begin in 2014 to ensure enough manufacturing lead time to offer continuous cargo services.