Current AF-NASA architecture level studies project future need for a heavy-lift, unmanned launch vehicle with low Earth orbit (LEO) payload delivery capability. To achieve this capability, vehicle concepts considered range from fully expendable to fully recoverable. Expendables entail high operations costs; recoverables, high development costs and, in the minds of many, high technical/cost risk. A concept that has been extensively studied is the partially reusable Shuttle-Derived Vehicle (SDV), seen as a potential candidate offering two to three times more cost-effectiveness than Titan or Shuttle ($/lb payload), and based on available hardware elements and current technology upgrades. The SDV is currently considered a viable candidate launch vehicle in ongoing systems studies.