of NASA’s space missions. Finding technologies that dramatically reduce launch cost is a tremendous challenge given the past lack of success.

Reliability and safety continue to be major concerns in the launch business. For NASA space missions, the cost of failure is extreme. Finding ways to improve reliability and safety without dramatically increasing cost is a major technology challenge.

2. Upper Stage Engines: Develop technologies to enable lower cost, high specific impulse upper stage engines suitable for NASA, DOD, and commercial needs, applicable to both Earth-to-orbit and in-space applications.

The venerable RL-10 engine is the current upper stage engine for both the Atlas V and Delta IV launch vehicles, but it is based on 50-year-old technology, and it has become expensive and difficult to produce. There are alternative engine cycles and designs that have the promise to reduce cost and improve reliability, and the opportunity exists for a joint NASA-Air Force technology development effort. Also, as discussed below, high-rate production can substantially reduce unit costs. To maximize production rates, new technologies should be applicable to both upper stage and in-space applications.


The results of the panel’s quality function deployment (QFD) scoring for the level 3 launch propulsion technologies are shown in Figures D.1 and D.2. Two technologies were assessed to be high priority based on their QFD scores:

•   Air Breathing Propulsion Systems: Rocket Based Combined Cycle (RBCC)

•   Air Breathing Propulsion Systems: Turbine Based Combined Cycle (TBCC)

These technologies, which received identical QFD scores, both burn oxygen extracted from the atmosphere (during the atmospheric portion of flight) giving some promise for increased efficiency and reduced cost. As discussed below, however, the greatest potential to reduce launch cost actually comes from high-priority technologies in other roadmaps.

Two medium-priority technologies deserve some mention. RP/LOX propulsion offers potential benefit for booster stages for all NASA space missions. However, this technology is already at a very mature state of development and application in Russia, and it is available commercially through products such as the RD-180 and AJ-26 engines. Therefore any decision for NASA to invest in this technology should primarily be made for programmatic and political reasons (e.g., the desire to create a domestic production capability), not technological reasons. These non-technological reasons could be important, even compelling, but the priorities in this report are based on technical— not political— considerations.

LH2/LOX propulsion is used for both upper stage and in-space applications. This basic technology area appears here in TA01 and in TA02, In-Space Propulsion (see technology 2.1.2, Liquid Cryogenic). LH2/LOX propulsion scored medium in both of these Tas, though it might have ranked higher if these two areas had been ranked together.


A matrix showing the linkage between technology rankings and top technical challenges is shown in Figure D.3. The highest ranked launch propulsion technologies are strongly correlated to the first technology challenge. The various air breathing technologies offer some prospects for reducing the cost of launch, but the correlation with launch propulsion technologies is diluted by the fact that these breakthrough technologies are somewhat speculative. The launch industry has searched for a breakthrough to lower launch costs for decades and, unfortunately, it has yet to materialize. The greatest potential for reduction in launch costs may reside in technologies included in other roadmaps, as discussed below.

There is a very strong correlation between the second challenge and the third ranked technology area.

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