Aerospace company Orbital Sciences Corp. suffered a big failure late Tuesday when one of its unmanned rockets bound for the station exploded moments after liftoff. The launch pad failure is a setback for a company with a 30-year history in private spaceflight, including 42 successful missions on its Pegasus small-payload rockets since 1990. The explosion also comes at a delicate time for the company, which is closing a $5 billion merger with defense contractor ATK. The company's launch pad and other facilities near a Virginia site were spared major damage, based on a preliminary analysis, Orbital executives said Wednesday. Orbital has a contract with Boeing to make boosters for missile defense. Orbital Sciences' most high-profile competitor in private spaceflight is Elon Musk's Space Exploration Technologies Corp., commonly called SpaceX. According to the company's history page, it got its first NASA contract in 1985, when it had 20 employees. In 2009, a NASA mission to monitor global warming from space ended when the satellite plunged into the ocean near Antarctica minutes after launch.