The RS-76 is a development stage man-rated reusable engine designed to support the proposed Reusable First Stage (RFS), which is also known as the Liquid Fly-Back Booster (LFBB), for NASA's Space Shuttle.

 The RS-76 engine system is being developed as a reliable, low cost LOX / kerosene booster engine utilizing a staged combustion power cycle with an oxidizer-rich pre-burner.  The maximum sea level thrust is 900,000 pounds and the vacuum specific impulse is above 340 seconds.  The simple engine layout includes one pre-burner, a single shaft main turbo pump assembly, one thrust chamber, three control valves and no gear box.  The engine's simplicity and low cost will be achieved in part by greatly reducing the total part count.  As currently designed, the RS-76 has one-tenth the number of parts of the SSME