468 was a self-imposed limitation implemented early in the program and will be reversed in future CubeSats);  therefore we needed to design for a much lower operating temperature to reduce the risk of damaging the resistors. We therefore chose to limit the operating temperature to 115°C. In practice, actuation temperatures rarely reach 115°C, but setting the actuators for flight gets much easier as the temperature increases. The aluminum cup is thermally isolated from the host structure with G-10 isolators to minimize heat loss and the overall power needed to actuate the device. We are exploring the idea of coating the flight actuators with low emissivity coatings to reduce power required for actuation by limiting heat loss due to thermal radiation.  The aluminum parts are plated with a hard coat anodize treatment, but the titanium parts were left bare.  The device acted as its own tell-tale separation indicator. When the plug is fully seated in the cup, it contacts the kick-off spring, which is electrically connected to the cup. A circuit is completed from the CubeSat input-output card through the CTERA and its titanium plug, through the solar array substrate, back over the solar array  hinge line, into the CubeSat harness into the IO card. When the plug is  released, continuity is broken, indicating separation. We verified the concept through several cycles of operation on the tension-only test-stand. The design required great care to re-set. The single-piece plug needs to be precisely aligned with the cup, inserted in as short a time as possible to reduce plug heating. This second-generation design also required fighting against a 44.5-N (10-lb) kickoff spring force during insertion. We ended up galling the surface of the plugs in our efforts to accomplish this. The second generation device functioned unreliably in flight-like use with a solar array wing. The flight-like wing, with its hinge line parallel to the gravity vector, imposed side loads upon the release mechanism that the test stand did not.   Figure 2 – Underside (left) and top side (right of the second generation device)  The third generation device  featured a lower mass high CTE part, a reduced length interface between  the two materials, and less heat transfer between the high CTE and low CTE parts, and surface treatments on both of the mating parts. Elimination of the kickoff spring preload during the precision mate of the high and low CTE parts made the mechanism much easier to re-set. Redesign of the solar array fitting accommodated the  range of motion constraints imposed by the flight solar array wing by using a  custom ‘near-spherical bearing’ featuring a pin and dual conical hole. The new interface to the reference mission solar array wing allows more alignment adjustability between the wing and the actuator. This tolerance eliminates racking and binding during wing deployment. Figure 3 depicts the third generation actuator body and plug and the assembly of pin, lower interface bracket and plug cap. The space-saving pin and dual cone features provide ‘near spherical bearing’ behavior in much less volume. To minimize galling and cold welding the aluminum and titanium parts under a sustained 6.9 mPa (1000 psi) interface pressure, surface finishes were critical. Two versions were fabricated, featuring different combinations of surface treatments on the high and low CTE materials. Some limited functional testing was used to determine which surface treatment combination would be used for the final design. Metrics were part wear, the change in temperature required to achieve separation, and the electrical energy expended to achieve separation. We selected hard coat anodize for the aluminum parts, and Tiodize, Type 2 for the titanium parts. Reduction of the contact area between plug and cup significantly reduced the amount of energy required for the actuator to function. Additionally, the annular interface area between the bottom of the plug and the cup was reduced by the addition of 8 radial ridges, which dramatically reduce the amount of heat transfer between the cup and the plug. Reducing energy absorbed by the plug reduces the amount of delta-T required to separate the plug from the cup. Because of the solar array deployed  Plug Cup Resistors  G-10 Isolator