Alliant Techsystems (ATK) is developing an extended cargo version of its two-stage Liberty spacecraft that will carry a pressurized logistics module in addition to its crew module.

Based on NASA’s 15-ft.-dia. Multipurpose Logistics Module for the space shuttle, the Liberty Logistics Module (LLM) will be capable of transporting up to 5,100 lb. of pressurized cargo. The LLM could accommodate four science racks to the International Space Station, ATK says.

“Liberty’s expanded service allows us to bring a commercial capability delivering up to seven crewmembers [and] 5,000 pounds of pressurized cargo, along with external cargo in a single flight,” ATK Liberty Program Manager Kent Rominger said in a statement.

Meanwhile, ATK has assembled an independent assessment team of human spaceflight veterans whose first task will be to advise the company on human-rating Liberty. FAA, which licenses U.S. commercial space launches, has not yet developed firm criteria for human-rating, but in the interim, the Liberty team will draw upon guidelines developed by NASA and other space agencies.

Bryan O’Connor, former astronaut and head of NASA’s safety and mission assurance organization, leads the independent assessment team, which also includes space shuttle veteran Ken Bowersox, space consultant Kevin Leclaire and Alain Souchier, who managed various propulsion efforts for Europe’s Ariane 5 rocket.

Liberty is based on a combination of hardware from NASA’s defunct Constellation program, including the five-segment solid-rocket booster developed for the Ares 1 rocket and a composite space capsule based on the Orion Multipurpose Crew Vehicle. Astrium Space Transportation is providing the Liberty second stage based on the liquid-fueled cryogenic core of the Ariane 5.

The Liberty rocket was first proposed in 2011 as a contender for NASA’s commercial crew program. Rominger has said the ATK and Astrium team could provide astronaut rides to and from the ISS for considerably less than the $62 million per seat that Russia currently charges for Soyuz rides. NASA rejected the initial Liberty bid in part because ATK and Astrium had no commitments by crew-vehicle developers interested in launching atop the proposed rocket.

In September 2011, ATK and Astrium said they would continue Liberty’s development under an unfunded Space Act Agreement with NASA. Under the agreement’s terms, the U.S. space agency provides engineering and other technical support to industry through mid-July, when a third round of commercial-crew development awards is expected to be announced.