WASHINGTON — Mark Bitterman, the veteran lobbyist who in June left Orbital Sciences Corp. to work for rival rocket builder Space Exploration Technologies Corp. (SpaceX), has resigned from SpaceX.

Bitterman, who formally joined SpaceX in mid-July as a senior vice president of government relations, resigned “for personal reasons — family obligations that require more time and attention than the demands of this job would allow,” Kirstin Brost Grantham, a Washington-based spokeswoman for SpaceX, said Aug. 30. She added that “on an interim basis, the SpaceX Government Affairs team will be managed by Tim Hughes, SpaceX’s general counsel.”

Before going to SpaceX, Bitterman had spent 19 years with Orbital, most recently as its vice president of government relations.

Attempts to reach Bitterman the week of Aug. 29 were not successful.

SpaceX is headquartered in Hawthorne, Calif. Like Orbital, which is based in Dulles, Va., SpaceX is under contract with NASA to haul cargo to the international space station. For those cargo resupply missions, the companies will fly their own privately operated vehicles, which they built with financial assistance from NASA. After a spate of delays, both companies are now scheduled to begin flying space station resupply runs in 2012.

SpaceX has not shied from wooing talent away from its rivals in the space business. However, some of those more senior hires have not always stuck.

In 2009, Robert Peckham, who was president and general manager of Long Beach, Calif.-based Sea Launch for more than two years, joined SpaceX as vice president of business development. He left the company only seven months later for Boeing Satellite Systems in El Segundo, Calif., a company at which he had worked for five years before joining Sea Launch.

Another former Sea Launch president, Jim Maser, joined SpaceX in 2006 as president and chief operating officer. Maser stayed with SpaceX a little more than a year before resigning to become president of Pratt & Whitney Rocketdyne in Canoga Park, Calif.

Diane Murphy, a public relations veteran who spent nearly three years as Northrop Grumman’s director of communications in Redondo Beach, Calif., joined SpaceX in mid-2008 for a seven-month stint as vice president of marketing and communications.

In other cases, SpaceX has held onto personnel it attracted from some of the more established aerospace companies.

Tom Mueller, now vice president of propulsion development for SpaceX, has been with the company since its inception in 2002. Before SpaceX, Mueller had spent 14 years at TRW Space & Electronics in Redondo Beach. Prior to leaving, he ran the company’s propulsion and combustion products department. TRW Space & Electronics Group was purchased by Northrop Grumman in 2002.

Chris Thompson, SpaceX’s vice president of product development since 2002, is a former Boeing engineer. Thompson was a senior manager at his old company, where he oversaw production and testing of the Delta family of expendable launch vehicles, and of the Titan 4 rocket. The Delta and Titan rockets are now part of the United Launch Alliance stable. That company was formed when Boeing and Lockheed Martin merged their government launch services businesses.

SpaceX also has attracted some former spacefarers to its ranks.

In 2009, former astronaut and international space station commander Ken Bowersox joined SpaceX as vice president of astronaut safety and mission assurance. He was joined earlier this year by fellow astronaut Garrett Reisman.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.