2013-02-23 00:58:38 -


-- Company Completes Final Ground Testing on New Medium-Class Launch Vehicle --

-- Next Program Milestone:  Test Flight From Mid-Atlantic Regional Spaceport at
NASA's Wallops Flight Facility --

(Dulles, VA 22 February 2013) -- Orbital Sciences Corporation (NYSE: ORB), one
of the world's leading space technology companies, today announced it
successfully conducted an extended-duration "hot fire" test of the first stage
propulsion system of its new Antares(TM) medium-class rocket.  Developed over a
four-plus-year period, Antares will be used to launch cargo supply missions to
the International Space Station as part of a $1.9 billion contract with NASA.

The 29-second hot fire test took place at 6:00 p.m. (EST) on February 22, 2013
at the Mid-Atlantic Regional Spaceport's (MARS) Pad 0A, which was designed and
built over the last several years to accommodate liquid-fuel space launch
vehicles.  The primary goals of the test were to ensure that the launch
complex's fueling systems and the Antares stage one test article functioned
properly in a fully operational environment, that engine ignition and shut down
commands operated as designed, and that the dual AJ26 first stage engines and
their control systems performed to specifications in the twin-engine
configuration.  The test included a full propellant loading sequence, launch
countdown and engine ignition operation. The pad's high-volume water deluge
system flowed throughout the entire period of the test to protect the pad from
damage and for noise suppression.

"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 Mr. Mike Pinkston, Orbital's Antares Program Manager.  "We
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."

With the hot fire test complete, Orbital will purge and clean the engines of
residual propellants and return the first stage test unit to the vehicle
integration facility for full reconditioning.  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.

Orbital is scheduled to conduct two launches under the Commercial Orbital
Transportation Services (COTS) Space Act Agreement with NASA in 2013.  In
addition, the company will launch eight operational cargo resupply missions to
the International Space Station (ISS) using Antares vehicles from late 2013
through 2016 under the Commercial Resupply Services (CRS) contract with NASA.
 The COTS and CRS flights will launch from NASA's Wallops Flight Facility in
eastern Virginia, which is ideally suited for ISS missions, and can also
accommodate launches to other orbits.  In addition, Orbital is currently
evaluating its options for development of a west coast launch site that would
enable the Antares rocket to address an even wider range of customer missions.

The Antares medium-class launch system will provide a significant increase in
the payload launch capability that Orbital can provide to NASA, the U.S. Air
Force and other customers.  The Antares rocket will be able to launch up to
14,000 lbs. into low-Earth orbit, as well as lighter-weight payloads into
higher-energy orbits.   Orbital's newest launcher is currently on-ramped to both
the NASA Launch Services-2 and the U.S. Air Force's Orbital/Suborbital-3
contracts, enabling the two largest U.S. government space launch customers to
order Antares for "right-size and right-price" launch services for medium-class

About Orbital

Orbital develops and manufactures small- and medium-class rockets and space
systems for commercial, military and civil government customers.  The company's
primary products are satellites and launch vehicles, including low-Earth orbit,
geosynchronous-Earth orbit and planetary spacecraft for communications, remote
sensing, scientific and defense missions; human-rated space systems for Earth-
orbit, lunar and other missions; ground- and air-launched rockets that deliver
satellites into orbit; and missile defense systems that are used as interceptor
and target vehicles.  Orbital also provides satellite subsystems and space-
related technical services to government agencies and laboratories. More
information about Orbital can be found at  Follow
Orbital on Twitter @OrbitalSciences.

# # #
Notes to Editors:

Barron Beneski (703) 406-5528
Public and Investor Relations

[Insert links to Hot Fire photos and videos]

Other high-resolution photos and images of Orbital's Antares rocket can be
downloaded for publication at

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