Airborne Power Supply Unit (APSU)

The Airborne Power Supply Unit (APSU) is a programmable DC/DC converter that can supply multiple constant voltage or constant current outputs in a small enclosure, enabling power conditioning from a single battery bus to multiple experiments with differing requirements.  The technology behind the APSU allows Suborbital Platforms and Range Services (SPARS) users requiring DC power distribution to minimize the number of battery packs and relays required for missions, thus reducing mass, volume, complexity, cost, and increasing flight safety and reliability.  The primary beneficiary for this technology is the science customer as the APSU consolidates power distribution and generation to a single unit, alleviating the customer of this burden and allowing the Principal Investigator (PI) to focus on the science.

The APSU concept is based on a buck regulator circuit first developed for use on the AETD Diminutive Assembly for Nanosatellite deployables (DANY) experiment which required 3.3V constant voltage from a +28V battery source.  Furthermore, the buck regulator circuit was also flown  and provided the flexibility late during integration to regulate the +28V battery bus to +12V which prevented the strain gauge experiment from overheating.  Finally, the buck regulator circuit was further refined and used on a Goddard Spaceflight Center's CubeSat on the Special Services Card (SSC) to provide constant current for deployment of the solar panels and magnetometer boom.

The primary objective of this effort is to develop a solid-state circuit in a small footprint that will efficiently convert a raw battery voltage to an adjustable constant voltage or constant current output.  Additionally, the APSU will integrate a microcontroller to adjust output set points, turn services on and off, and monitor power draw of active loads for fault detection and isolation.

The APSU proposal addresses risk reduction in existing airborne power distribution systems commonly used on suborbital platforms.  For example, Sounding Rocket PIs are currently responsible for providing their own experiment power conditioning.  The APSU would enable consolidation of power distribution and generation to a single architecture with fault protection (i.e. overvoltage, overcurrent, etc.), allowing NASA to provide experiment power conditioning as a standard service to the suborbital science community.

In addition to the suborbital science community, the APSU core technology could be modified to meet CubeSat needs with appropriate parts selection for the mission environment, allowing it to be utilized by the SmallSat community to deploy solar panels via electric motors, actuate CubeSat deployables via burn wires, or provide power conditioning to multiple satellite experiments utilizing a common battery bus.   

The innovative elements of the work proposed are:  high efficiency power conversion (switching versus linear), small form-factor, inherent fault protection, and robust solid state circuitry.