It would replace two flights of the Guardian module earlier planned.
The flight would test the operational life support system that would provide a nitrogen/oxygen atmosphere to occupants of the full-sized station. The internal structural arrangement (central hardened spine, internal longerons, solar arrays, and attitude control system) would all be more representative of the operational system.
Habitable Volume: 30.00 m3.
Gross mass: 3,000 kg (6,600 lb).
Height: 6.80 m (22.30 ft).
Diameter: 2.20 m (7.20 ft).