One of the more unusual stories this week and another I really didn’t expect to happen was the surprise delivery of the next Atlas V first stage to Cape Canaveral on NASA’s Pegasus barge.

The United Launch Alliance (ULA) factory is in Decatur, Alabama, and its rocket stages produced there are transported on different rivers in the U.S. on a dedicated ship called the R/S RocketShip. The RocketShip can navigate both the shallow water of rivers and the open ocean to deliver rockets to Florida or through the Panama Canal to California. This method contrasts with SpaceX, which designed its Falcon rocket stages to be road transportable.

The reason that Pegasus had to be used instead of the R/S RocketShip was because of a lock closed for maintenance on the Tennessee River, preventing the large RocketShip from moving.

The Pegasus barge was designed for first the space shuttle external tank and now the SLS core stage, so it can handle large rockets. The Atlas V first stage is 33 meters long and 3.8 meters wide.

To get the Atlas V stage to Pegasus, ULA first put it on a barge that could fit through a smaller but open lock and took the stage to where Pegasus was. From there, Pegasus took it the rest of the way, following the usual route of the RocketShip.

This Atlas V core stage joins the already stacked Centaur and interstage plus two solid rocket boosters for the Starliner mission. The original first stage for Starliner’s OFT-2 mission was used by the Lucy asteroid mission because of the tight turnaround required. The Centaur could not be used on the Lucy mission, as it was specific to the Starliner configuration, two engines rather than one. Starliner OFT-2 is expected to launch in May.

More Information

ULA press release