Orbital Sciences Corp. conducted a successful engine test of its Antares rocket Friday, demonstrating the booster's dual-engine first stage on a Virginia launch pad and clearing a hurdle before the rocket's first flight in April.

Ignition of the Antares rocket's first stage AJ26 engines was at 6 p.m. EST. Credit: NASA/Orbital Sciences
 
As light rain fell, the Antares engines ignited at 6 p.m. EST (2300 GMT) on launch pad 0A at the Mid-Atlantic Regional Spaceport at Wallops Island, Va.

The booster's two AJ26 engines, built in Russia and modified by Aerojet, fired for 29 seconds. The rocket remained firmly attached to the launch pad as the engines generated 680,000 pounds of thrust, sending a ground-shaking roar across the coasts of Virginia and Maryland.

The hot fire test occurred at the end of a full countdown sequence, including fueling of the first stage with kerosene and cryogenic liquid oxygen.

"Our initial assessment of the test data shows that we were successful in achieving each of the primary objectives we had hoped to accomplish going into the test," said Mike Pinkston, Antares program manager at Orbital Sciences. "We will now turn our attention to the next major milestone for the Antares program, which is the inaugural flight of the rocket. I know that I speak for the entire Antares team when I say we are beyond excited to know that our newest rocket will take to the skies in just a matter of weeks."

Officials said the primary goals of the test were to demonstrate the launch pad's fueling systems, engine ignition and shutdown commands, and the performance of the AJ26 engines in a dual-engine configuration.

The launch pad's water deluge sound suppression system also worked as designed to protect the pad from damage, according to Orbital Sciences.

The Antares rocket is the first liquid-fueled vehicle developed by Orbital Sciences, and the rocket's new launch pad is the first facility at NASA's Wallops Flight Facility designed to handle large quantities of liquid propellants.

The rocket's main engines are tested one-at-a-time at NASA's Stennis Space Center in Mississippi, but Friday's hot fire was the first time two Russian-built, U.S.-owned AJ26 engines fired at the same time.

Aerojet converted Russian NK-33 engines into an AJ26 engine by removing some harnessing, adding U.S. electronics, qualifying it for U.S. propellants, and modifying the system to gimbal for steering.

Kept in storage for four decades, the NK-33 engines were originally designed and built in the 1960s and 1970s for the ill-fated Soviet N1 moon rocket.

"Aerojet purchased the NK-33 engines from JSC Kuznetsov in the mid-1990s and has been developing design modifications to ensure that the AJ26 is suitable for U.S. commercial launch vehicles," said Pete Cova, Aerojet's executive director of space and launch systems, in a statement. "As teammates, JSC Kuznetsov brings tremendous technical support to our efforts and we are looking forward to supporting Orbital in its cargo resupply contract with NASA."

The Antares first stage core tank was designed and built in Ukraine by Yuzhnoye and Yuzhmash. The Ukrainian contractors modified the 12.8-foot-diameter first stage of the Zenit rocket for Orbital's Antares program.

Orbital Sciences is one of two commercial partners commissioned by NASA to develop private resupply vehicles for the International Space Station.

Two Antares rockets are in the horizontal integration facility at Wallops awaiting launch. Credit: Orbital Sciences

"This pad test is an important reminder of how strong and diverse the commercial space industry is in our nation," said Phil McAlister, NASA's director of commercial spaceflight development. "A little more than one year after the retirement of the space shuttle, we had a U.S company resupplying the space station, and another is now taking the next critical steps to launch from America's newest gateway to low Earth Orbit. Today marks significant progress for Orbital, MARS and the NASA team."

NASA has an agreement to pay Orbital up to $288 million in a public-private partnership called the Commercial Orbital Transportation Services, or COTS, program.

The COTS agreement covers development of the Antares rocket and Cygnus cargo spacecraft. NASA has a separate $1.9 billion contract with Orbital Sciences for eight operational flights.

NASA has a similar arrangement with SpaceX, which completed its COTS obligations last year and began operational resupply services in October.

Orbital Sciences plans to remove the Antares first stage from the launch pad and return the booster to the horizontal integration facility about one mile north of the pad.

"Shortly after completing pad and fueling systems post-test inspections and performing any necessary reconditioning work, Orbital will roll out the first complete two-stage Antares rocket to prepare it for the test flight, which is expected to take place in approximately six weeks," the company said in a statement.

The Antares test flight, which could occur as soon as early April, will launch a dummy payload into orbit. A second Antares mission in June or July will launch the first functional Cygnus spacecraft on a demonstration flight to the International Space Station.

Operational flights could begin before the end of 2013.

Orbital Sciences is also trying to sell Antares rockets to NASA and the U.S. military for satellite launches.