WASHINGTON — The chief financial officer of Alliant Techsystems (ATK), builder of the space shuttle’s solid boosters and presumed provider of solid-rocket boosters for the next U.S.-owned heavy-lift rocket, has quit.

John Shroyer, who also is a vice president, will leave the company Aug. 4, the day ATK plans to release its fiscal first-quarter earnings. He is leaving to become chief financial officer of Capsugel, a Peapack, N.J., manufacturer of medical capsules.

ATK announced Shroyer’s departure in a July 14 statement. Shroyer gave notice July 11, according to a filing with the U.S. Securities and Exchange Commission.

Shroyer, 47, has been ATK’s chief financial officer since 2006. He was the company’s interim chief executive from November 2009 to February 2010, following Daniel Murphy’s retirement. 

Effective Aug. 8, Thomas Sexton, ATK’s vice president and corporate controller, will become the company’s interim chief financial officer.