Pratt & Whitney, Rocketdyne, and Dynetics, Inc. presented a competitor known as "Pyrios" in NASA's Advanced Booster Program, which aims to find a more powerful successor to the five-segment Space Shuttle Solid Rocket Boosters intended for early versions of the Space Launch System, using two increased-thrust and heavily modified F-1B engines per booster. Due to the engine's potential advantage in specific impulse, if this F-1B configuration (using four F-1Bs in total) were integrated with the SLS Block 2, the vehicle could deliver to low Earth orbit, while is what is regarded as achievable with the planned solid boosters combined with a four-engine RS-25 core stage.