Closed-cycle cryocooler alternatives currently available for space applications in the temperature range of 10 to 20 K are not well suited to the requirements of such applications. In many cases reliability is low and vibration high. In other cases, coolers are too massive and inefficient. However, such coolers are often important components in enabling many of the advanced sensor and detector technologies of the future. This proposal describes a two-stage pulse tube cooler (PTC) that combines a bootstrap staging configuration with an innovative second-stage design to deliver cooling in the range of 10 to 20 K. The proposed cooler contains four innovative concepts that together will overcome the limitations of current cryocooler technologies and improve efficiency while simultaneously reducing mass.