High Performance Batteries: X-38 Crew Return Vehicle

X-38 Crew Return VehicleThe X-38 program is an activity to demonstrate key technologies associated with development of Crew Return Vehicle for the International Space Station (ISS). The X-38 vehicle consists of a lifting body spacecraft and a De-orbit Propulsion Stage (DPS). The DPS provides on-orbit attitude control and 28V power via lithium primary batteries for the CRV for up to 7 hours. Thereafter, it de-orbits the spacecraft and is jettisoned before the spacecraft re-enters. Prior to jettison, the X-38/CRV will switch to internal nickel metal hydride batteries for 28V power for 3 additional hours of runtime. During the atmospheric entry phase, the vehicle will fly with the use flight control surfaces (2 body flaps and 2 rudders) controlled by Electromechanical Actuators. Before landing, the vehicle will deploy parachutes controlled by winches. Both the Electromechanical Actuators and winches will be controlled by one set of three high-power Flight Battery Modules.X-38 CRV (courtesy of NASA)

AZ Technology chose SRI to provide battery expertise for the NASA X-38 project. SRI aided in the design, manufacture, verification and delivery of the 270V Flight Battery Modules (FBM) containing rechargeable nickel cadmium cells. The FBM utilizes self-contained Ground Support Equipment (GSE) unit that provides fast charge/discharge control and battery diagnostics functions using 120 VAC input. The GSE performs battery diagnostics and provides battery status information such as temperature,  effective internal resistance, voltage, and capacity. The GSE provides analog outputs and digital input/output via RS 232 port. The GSE and battery have safety interlocks that enable dead-face cable connections.

The 270V battery utilizes commercially available sealed Nickel Cadmium cells, has a rated capacity of 9.6Ah and is designed for extreme conditions. The battery consists of four 210-cell strings with individual control electronics and protection circuits. The cell string is capable of delivering up to 2, 870 W/L or 1,120 W/kg, in a pulsed duty cycle application.  During Mission Profile, the battery easily delivers the required 36kW-100 milli-second (170A) pulses over a 220-second duration at 50% state of charge.

             high powered battery assembly


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