Over the course of 30 years, from 1981 to 2011, NASA’s Space Shuttle program carried out 135 missions, completing 21,152 Earth orbits and traveling 542,398,878 miles during 1,334 days of flight time. But when the Atlantis returned to Earth on July 21, 2011 the program came to an end. Three years later, the consequences of NASA’s decision to end the Space Shuttle program are appearing in the U.S. and UK submarine-launched ballistic missile (SLBM) program. Because both the space shuttles and the U.S. Trident D5 SLBMs rely on solid propellant fuels, NASA’s decisions about its space programs have repercussions in the defense industry. In 2017, NASA plans to launch the first mission of the new Space Launch System (SLS). In 2016, NASA will decide how exactly the SLS will be propelled. If major changes to the rocket propellant system are made, there could be severe consequences for the solid propellant fuel industry, and, consequently, the Trident SLBM program. Rockets and missiles use two main types of propulsion systems: solid fuel and liquid fuel. NASA’s space shuttles used liquid propellant engines for the main engine system. Each rocket, however, also used two solid fuel boosters, which provided about 85% of the initial thrust needed for liftoff. These boosters are the largest motors ever built for use on manned rockets; each contains approximately 1.1 million pounds of solid propellant. After each launch, the boosters separated from the shuttle, and were recovered and reused. ATK, an aerospace technology company in Utah, was responsible for preparing the boosters for reuse by reloading them with fuel. The Trident D5 missile is powered by a similar, but smaller solid propellant rocket. The motor systems and fuel for the missiles are, like the space shuttles’ fuel, supplied by ATK. However, the rocket engines purchased for the Trident missile system account for less than one-fifth of U.S. solid rocket motor business. After all, an entire Trident D5 missile weighs approximately 130,000 pounds, about 10% of the weight of just the fuel in one of a space shuttle’s boosters. The end of the Space Shuttle program immediately had implications for the solid rocket fuel industry and U.S. defense expenditures. A 2011 Department of Defense Selected Acquisition Report stated that solid rocket motor costs had increased due to decreased demand for solid rocket propellant. The report also concluded that, “The decreasing demand is expected to continue and will accelerate downward as both NASA and the Air Force reduce their procurements over the next several years, increasing the risk of future unit cost increases to the Navy.” The solid rocket propellant industry will be severely impacted again by the decisions that NASA makes in 2016 about the SLS propulsion system. In order to develop the SLS propulsion system, NASA is holding a design competition (the SLS Advanced Booster Engineering Demonstration and/or Risk Reduction [ABEDRR] procurement). NASA awarded contracts to three major aerospace technology companies (ATK, Dynetics in collaboration with Pratt and Whitney Rocketdyne [PWR], and Teledyne Brown in collaboration with Aerojet) to develop proposals for a new rocket booster for the SLS. The three proposals are expected to include two liquid propulsion systems (from Dynetics/PWR and Teledyne Brown/Aerojet) and one solid fuel booster (from ATK). The research and development contracts extend through March 31, 2015, and NASA is expected to choose a design in 2016. For NASA, there are convincing arguments on both sides of the solid-liquid propellant debate. Both solid propellant boosters and liquid propellant boosters have advantages that may lead NASA to prefer them over the alternative. Solid boosters have traditionally been used in NASA’s rockets and are also likely to be less expensive. On the other hand, liquid boosters would likely have higher performance. Selecting one of the liquid booster options would significantly limit NASA’s demand for solid rocket booster fuel and the overall demand on the industry, increasing, once again, the price of the Trident propulsion systems. This price increase could occur concurrently with the Navy’s Trident D5 Life Extension program (LE), which is intended to extend the lifetime of the Trident missile through 2042. According to former Strategic Systems Programs (SSP) Director Rear Adm. Dwyer, “the biggest challenges [of LE] involve determining the service life of the three-stage boost motors that comprise the missile propulsion system […].” The LE program is already projected to cost approximately $25 billion over the course of 7 years from 2011 to 2018, and those expenses could rise rapidly if solid fuel booster prices increase. In addition to the increased costs that would be imposed upon the Navy, Vice Adm. Terry Benedict, the current SSP director, argues that NASA choosing to use a liquid booster would, “result in diminished critical skills in the solid rocket motor industry production lines […],” endangering the entire industry and jeopardizing the progress of the tightly scheduled, multi-billion dollar Trident LE program. The limited options available to the Navy further complicate the issue. Solid fuel propulsion is currently the only possible system for the Trident missile; liquid rocket fuel is not safe in the close quarters of a nuclear submarine. Transitioning to liquid fuels (alongside NASA and the Air Force missile forces) is simply not an option. Instead, collaborative research and development efforts in the Navy, Air Force and the solid propellant industry are focused on developing a new solid propellant mix that can meet the needs of commercial, naval and air force users and take advantage of bulk purchase prices. The fact of the matter is NASA’s scientific decisions have the potential to severely weaken the industrial base of the Trident missile program. Limitations to that program would have a significant impact on NATO nuclear deterrence. The Trident D5 missile is the SLBM that arms both the U.S. and UK ballistic missile submarines (SSBNs). The U.S. and UK Navies’ SSBN modernization plans rely on access to the Trident D5 missile through 2042. The SSBN forces are the cornerstone of U.S. strategic deterrence and the only leg of the UK deterrent. Any limitations to that capacity would likely have serious effects on the strength of NATO nuclear deterrence.