OKLAHOMA CITY--(BUSINESS WIRE)--July 24, 2006--Rocketplane Kistler (RpK) and Orbital Sciences Corporation (NYSE:ORB) announced today that they have entered into a strategic relationship to support the NASA COTS program and other applications of RpK's innovative space transportation system.

Orbital will join the RpK industrial contractor team with supporting responsibility for program management, systems integration, launch operations, and safety & mission assurance. David Low, Orbital Vice President, will lead Orbital's effort with support from Dr. Antonio Elias, Executive Vice President of Orbital's Advanced Programs Group. As part of this agreement, Orbital also plans to make a strategic investment in RpK.

Rocketplane Kistler and its K-1 space transportation system has been selected as one of the six finalists in NASA's Commercial Orbital Transportation Services (COTS) program. RpK has proposed using its fully reusable K-1 to provide cost-effective and reliable delivery and return of cargo and science payloads to and from the International Space Station. The K-1 is in an advanced state of development and will be capable of providing end-to-end ISS servicing beginning as early as 2009.

Commenting on the strategic alliance, Mr. George French, Chairman and CEO of RpK, stated, "We are very pleased that Orbital has joined the RpK team as a key strategic partner and principal contractor in the K-1 development program. Orbital brings a wealth of experience and expertise as a prime contractor and system integrator in space-based programs. We look forward to their participation in the final stages of the K-1 development program. We expect their contributions will have an immediate and profound impact on the program."

Mr. David Thompson, Orbital's Chairman and CEO said, "With the establishment of our new partnership with Rocketplane Kistler, we are excited to have the opportunity to join a program that could revolutionize space launch services. Having studied the substantial amount of work that has been accomplished on the K-1 program and the planning that is already in place, we are convinced that it can be operational in a relatively short period of time. We are committing top management and engineering resources to ensure K-1 mission success for NASA's COTS program."

About Orbital Sciences Corporation

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

About Rocketplane Kistler

Rocketplane Kistler (RpK) brings together two industry-leading makers and future operators of the next-generation orbital and suborbital space transportation vehicles. RpK was formed when Kistler Aerospace Corporation and Rocketplane Limited, Inc. were brought under common ownership. RpK markets the services of the fully reusable, two stage Kistler K-1 orbital launch vehicle and the fully reusable, suborbital Rocketplane XP Spaceplane, both of which will be first to fly in their respective markets.

About Rocketplane Limited, Inc.

Rocketplane was formed in 2001 to develop and produce vehicles for the suborbital space tourism market. Over the last 5 years, Rocketplane developed and is currently building the first XP Spaceplane, a four-seat, fighter sized vehicle powered by two jet engines and a rocket engine. For more information, please visit the website: www.rocketplane.com

About Kistler Aerospace Corporation

Kistler was formed in 1993 to design, develop and operate the first fully reusable orbital space transportation vehicles. Kistler has completed significant K-1 production milestones, including production of primary structure and engine testing. The K-1's design enables it to provide a variety of space transportation services, not only to LEO, but also to Medium Earth Orbit (MEO) and Geosynchronous Transfer Orbit (GTO).

    CONTACT: Orbital Sciences Corporation
             Barron Beneski, 703-406-5528
             beneski.barron@orbital.com
                 or
             Rocketplane Kistler
             Will Trafton, 619-519-2931
             wtrafton@san.rr.com

    SOURCE: Orbital Sciences Corporation