The payload class ranges of these requirements include 3 to 4 small (<2 t) payloads per year, 2 to 3 medium (2–20 t) payloads per year, and a heavy (20–50 t) payload requirement every few years. As a customer of launch services, SMD depends on national capabilities and does not invest in launch propulsion system technologies; it is primarily interested in low-cost and reliable launch services. ESMD has a significant proposed investment in LPSTA; this can be seen in the HLPT plan and its emphasis on selected engine technologies, e.g., RP and methane (CH4) prototype engines. It is also reflected in the HEFT planning to support a near-Earth object (NEO) mission (the requirement for a crewed super-heavy (>50 t) launch vehicle in the 2020 time frame)