Like other modules made by Bigelow Aerospace, Galaxy was based on the inflatable TransHab design by NASA, and was to be used for advanced systems testing before the company launched human-rated vehicles.

Galaxy started life as twin spacecraft named Guardian which would have acted as 45% scale intermediates between the one-third size Genesis I & Genesis II pathfinders and the full size BA 330 man-rated module.

This Galaxy had twice the interior volume of the Genesis craft: 23.0 cubic meters (812.2 cu ft).

Instead, many of the module's systems—possibly the entire craft—would be constructed and ground tested, allowing Bigelow employees to gain further experience and potentially advance Sundancer's schedule.

Among the most notable upgrades were improved avionics and attitude control systems, a more damage-resistant interior air barrier and expanded communications bandwidth capabilities.