DULLES, Va.May 10, 2006--Orbital Sciences Corporation (NYSE:ORB) announced today that it has been awarded a research and development contract by the U.S. Air Force for the Hybrid Launch Vehicle (HLV) Studies and Analysis Program. Under this new contract, Orbital will develop operationally responsive space launch designs that combine a reusable first stage with various types of expendable upper stages. This approach will enable lower-cost responsive space access in the near future, while lowering life cycle costs compared to fully reusable or fully expendable systems.

Mr. Brian Winters, Orbital's HLV Program Manager, said, "The U.S. Air Force seeks a space launch architecture that combines the cost reductions and fast response time that a reusable design offers, while avoiding some of the penalties associated with a fully reusable system. We are using the X-34 research vehicle that Orbital designed and built for NASA in the late 1990's as a point of departure for this effort. As a result, the HLV effort is afforded a significant head start compared to starting the program from scratch."

Under the HLV Studies and Analysis contract, Orbital is evaluating alternative aerodynamic, propulsion and structural configurations, identifying potential development program risk and mitigation plans, and providing recommendations for technical risk reduction activities.

The HLV Studies and Analysis Program also examines potential subscale demonstrators of an operational spacelift concept and recommends an associated flight demonstration program. The subscale demonstrator flights can be used as part of a risk reduction program to validate the architecture concept. Orbital is also assessing infrastructure at various candidate launch sites and comparing them to requirements derived in the architecture development activities.

Orbital has already begun the process of sharing concepts with the Air Force. In late April, Orbital hosted the Air Force HLV team for a "kick-off" meeting at the company's Dulles, Virginia facilities, where a wide range of design trades were examined and discussed.

About Orbital

Orbital develops and manufactures small space and rocket systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-orbit, geosynchronous-orbit and planetary spacecraft for communications, remote sensing, scientific and defense 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 offers space-related technical services to government agencies and develops and builds satellite-based transportation management systems for public transit agencies and private vehicle fleet operators.

More information about Orbital can be found at: http://www.orbital.com


    CONTACT: Orbital Sciences Corporation
             Public and Investor Relations
             Barron Beneski, 703-406-5528

    SOURCE: Orbital Sciences Corporation