270V Battery for Concept X-38:
Crew Return Vehicle (CRV)
AZ Technology lead
the effort to design, manufacture, verify
and deliver the 270V Flight Battery
Modules containing rechargeable nickel cadmium
cells. AZ Technology, system integrator,
strategically partnered with Symmetry
Resources, Inc. to provide battery expertise
for the X-38 project.
The X-38 program was an activity to demonstrate
key technologies associated with development
of a Crew Return Vehicle for the International
Space Station (ISS). The X-38 concept vehicle was to consist
of a lifting body spacecraft and a De-orbit
Propulsion Stage (DPS). The DPS would provide
on-orbit attitude control and 28V power via lithium primary batteries for the CRV for up to 7 hours. Thereafter, it would de-orbit
the spacecraft and be jettisoned before
the spacecraft re-entered. Prior to jettison,
the X-38/CRV would switch to internal nickel
metal hydride batteries for 28V power for
3 additional hours of runtime. During the
atmospheric entry phase, the vehicle would
fly with the use flight control surfaces
(2 body flaps and 2 rudders) controlled
by Electromechanical Actuators. Before landing,
the vehicle would deploy parachutes controlled
by winches. Both the Electromechanical Actuators
and winches were to be controlled by one set
of three 270V nickel cadmium Flight Battery Modules (FBM).
AZ Technology and Symmetry Resources developed and space qualified this 270V FBM for the X-38 concept crew return vehicle. This was the first 270V battery system approved for human spacecraft.
The FBM uses a self-contained ground support equipment (GSE) unit to provide fast charge/discharge control and battery diagnostic functions using 120VAC 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 an RS 232 port. The GSE and battery have safety interlocks that enable dead-face cable connections.
The 270V battery uses commercially available sealed nickel-cadmium cells and has a rated capacity of 9.6Ah. The battery consists of four 210-cell strings with individual control electronics and protection circuits. The cell string design will deliver up to 2,870W/L or 1,120W/kg, in a pulsed duty cycle application. During mission profile, the battery easily delivers the required 36kW- 100 millisecond pulses over a 220-second duration at 50 % state of charge.
The battery design qualification was completed for NASA-JSC in July 2002. The qualification testing consisted of 20-G mechanical shock and 9.05Grms random vibration while under load, thermal performance (10 deg C to 70
|deg C) while discharging to the mission profile, overpressure and vacuum exposure, thermal cycling from (-31 deg C to 45 deg C), radiation, and various other tests. One battery/GSE and four flight batteries/GSE were produced.