A focus on easy maintenance would reduce the operating costs of the HL-20 PLS. The vehicle would be prepared in a horizontal position, and its large exterior access panels permit easy access to subsystems, allowing easy servicing or replacement. The selection and design of these subsystems would emphasize simplicity and reduce maintenance requirements: for example, hydraulic systems would be replaced by all-electric controls. Moreover, unlike the Space Shuttle, the HL-20 would not have a payload bay or main engine propulsion, and its thermal protection system, while similar to the Space Shuttle's combination of tiles and ablative coatings, would be far quicker to inspect and maintain due to the HL-20's much smaller size. These design changes and subsystem simplifications, along with the adoption of aircraft maintenance philosophies, could reduce the HL-20 preparation man-hours to less than 10 percent of the Space Shuttle Orbiter's requirement.