NASA awarded $20.7 million to a Rockledge, Fla., construction company to modify a mobile launcher at Kennedy Space Center for the Space Launch System (SLS) heavy-lift rocket the agency is building to launch the Orion crew capsule on deep-space missions.

Under the firm, fixed-price contract announced May 8, J.P. Donavon Construction Inc. is expected to begin work at NASA’s Florida launch site in June and finish by the end of 2014. Midwest Steel Inc. of Detroit is a major subcontractor on the project. 

SLS is slated to make its first launch in 2017, lofting an unmanned Orion toward the Moon. A crewed repeat of the circumlunar mission is targeted for 2021.