50 which was nearly triple the milestone objective of  16.7 kW/kg (50 hp/lb). Mo reover, the instantaneous  specific power, again using Equation 1 at each time-st ep, was plotted throughout the usable stroke of the  test fixture, and is shown in Figure 11. 

Figure 11.  Specific Power Throughout Test Fixture Stroke  The important conclusion to draw from Figure 11 is that the specific power exceeded the milestone of  16.7 kW/kg (50 hp/lb) for virtually the entire effective stroke. Two different methods were originally used to  curve-fit the displacement-time data, resulting in so me variation in the calculation of peak power. The  other method resulted in a peak of 57.1 kW/kg (171 hp/ lb), or about 20% higher. The more conservative  results are published here, but there should be recognition of some small level of uncertainty.  Even more power may be available with the existing setup, since only mid-sized adjustment spacers (shown in Figure 6) were used in the release/trigge r mechanism; higher initial pressure (and thus final  combustion pressure) could be achieved with the current hardware. Some minor fixture wear from usage was observed at this stage of the program, but nothing appeared to be detrimental to the demonstrated performance.   Practical Actuator Application Description 

After proving that the state of t he art in actuator technology coul d be exceeded, the next goal for the  project was to develop a practical application for such an actuator. That application was to use the actuator, in concert with a power transfer mechanism  assembly, to twist a scale prototype rotor blade.  Twisting such a blade in flight was intended to improve the performance at multiple points in the  performance envelope.  The actuator designed and developed for the roto r blade twist mechanism is a bidirectional  electrochemical-combustive actuator  designed to provide the mechanical force to twist and untwist the  blade. The actuator body has mounting points and is sized to mount in the interior of the blade. The end of the piston shaft has a threaded connection to c ouple the actuator to the blade’s internal twist  mechanism. Electrical control wires extend from the act uator through the interior of the blade to its root  end. Connections to external control electronics can be made from there.  The actuator design incorporates two electrochemical -combustive units that act on a single piston to  provide activation in two directions. In typical bl ade operation the electrochemical-combustive units would  be activated alternatively. One elec trochemical-combustive unit serves to extend the piston shaft, while  the other serves to withdraw it.   The electrochemical-combustive units operate in tw o phases. In the first, or “charge,” phase the  electrochemical unit generates combustible gas. Then in the “fire” phase, the igniter initiates the  combustive process and the resulting sudden pressure pulse drives the piston, producing motion of the shaft. The force exerted by the ac tuator can be adjusted by varying the duration of the “charge” time. 050100150200 0 0.0005 0.001 0.0015 0.002 0.0025 0.003HP / lb Time (sec)Instantaneous Horsepower-per-Pound NASA/CP-2010-216272