It's anchors aweigh on refurbishments to NASA's Pegasus barge, which will be used to ferry the massive core stage of America's next great ship -- the Space Launch System. SLS will be the most powerful rocket ever built for deep space missions, including to an asteroid and ultimately to Mars.

The core stage, towering more than 200 feet tall with a diameter of 27.6 feet, will store cryogenic liquid hydrogen and liquid oxygen that will feed the vehicle's RS-25 engines.

The core stage is made up of five parts: the engine section, liquid hydrogen tank, intertank, liquid oxygen tank and forward skirt. Work is currently underway at NASA's Michoud Assembly Facility in New Orleans to build the core stage using state-of-the-art welding techniques and machinery.

During the space shuttle era, Pegasus was used to carry shuttle external tanks and other hardware from Michoud to NASA's Kennedy Space Center in Florida.

"Modifications were needed to the barge due to the sheer size of the SLS -- which is more than 50 feet taller than the shuttle, and will launch more than three times as much weight into space," said Alan Murphy, team lead for the Pegasus project at NASA's Marshall Space Flight Center in Huntsville, Alabama.

"The core stage is 59 feet longer and more than 500,000 pounds heavier, including the ground support equipment, than the space shuttle external tank. The modification work is on schedule, and we look forward to seeing the barge back in the water for a new era of exploration."

Pegasus -- housed since 2011 at NASA's Stennis Space Center near Bay St. Louis, Mississippi -- is now docked at Conrad Shipyard LLC in Morgan City, Louisiana.

Conrad will perform all necessary modifications and refurbishments to ensure the restored vessel meets American Bureau of Shipping standards, including load line certification, or verification of the barge's legal loading limit to safely maintain buoyancy during water travel.

The Corps of Engineers' Marine Design Center in Philadelphia, Pennsylvania -- utilizing the engineering expertise of Bristol Harbor Group of Bristol, Rhode Island -- is performing the architecture and engineering work for the barge modification, as well as managing the Conrad contract.

Conrad crews are currently building a new, 165-foot center section for the barge. The modifications will bring the total length of the barge from 260 feet to 310 feet -- a little more than the length of a football field. A 115-foot center section of the existing barge will be removed and the new piece installed later this fall. Work is expected to be completed in early 2015.

Once the modifications are complete, the Pegasus will be stationed at Michoud for operational readiness and maintenance. The first planned set of voyages for the Pegasus will be from Michoud to the Marshall Center to deliver the core stage structural test articles for testing to ensure that these huge structures can withstand the incredible stresses of launch.

The barge also will deliver the flight core stage from Michoud to Stennis, where it will be tested in late 2016 and early 2017 on the B-2 test stand. The core stage will be installed on the stand -- currently undergoing its own modifications -- for propellant fill and drain testing and a hot fire test.

Once testing is complete at Stennis, the Pegasus will transport the core stage to Kennedy Space Center for preparation and integration into the SLS flight vehicle in the Vehicle Assembly Building.

The first flight test of the SLS will be configured for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system. As the SLS evolves, it will be the most powerful rocket ever built and provide an unprecedented lift capability of 130 metric tons (143 tons) to enable missions even farther into our solar system.