CAPS is a flexible and modular CubeSat propulsion system that employs DSSP’s electric solid propellant technology. The system can fire up to 12 different micro-thruster elements, each having a lifetime exceeding 250 pulses. Ignition power is delivered via capacitor discharge, which results in an extremely high power, short duration impulse. Pulse frequency is dependent on power input and can reach 0.04 Hz. The CAPS controller is a miniature bi-level PCB stack less than 2.25 inches in height. Thrusters can be board-mounted on a third stacking PCB or be installed in modular housings that wire to the controller. CAPS accepts a 5V to 12V DC supply and has a simple SPI communications interface. Power consumption is dependent on the user-programmable arm rate and varies over the range of 0.1 to 2.3 Watts.
Delivering approximately 50 m/s of delta-v to a 4kg, 3U CubeSat, DSSP’s space qualified CDM-1 is designed for either a single delta-V maneuver or a rapid deorbit. The adapter plate is designed for easy mounting of the motor to the standard CubeSat structure. The CDM-1 mounts on the outside of the CubeSat which then fits inside deployment spring of a P-Pod so that the CDM-1 does not intrude into any of the normal CubeSat payload area. The CDM-1 is optimized for smooth plug-and-play integration into the CubeSat standard. The CDM-1 draws less than 5W of power for operation, using an Omnetics Bi-lobe 9-pin connector for arm and fire commands.
DSSP is currently in development of a multi-pulse motor fueled by a similar nonmetallized, Electric Solid Propellant (HIPEP) to that which was deployed from the International Space Station during the SPINSAT mission. The design goal of this system is to desaturate reaction wheels on 6U or 12U deep space CubeSats. The motor is currently TRL 3, but DSSP is planning on having a flight-ready system by mid-2017.
In partnership with the Naval Research Laboratory, DSSP developed the propulsion system for SpinSat and has had it deployed from the pressurized, manned section of the International Space Station through the airlock on the Kibo lab module. For this mission, DSSP’s ESP microthrusters were adapted to the satellite’s existing UMS plugs. This simplified the satellite structural design and allowed for a modular propulsion solution. On SpinSat, each UMS plug houses six microthrusters. There are twelve of these UMS “clusters” or 72 total thrusters per satellite. DSSP’s Power Processing Unit (PPU) is a switching power converter that operates in current-mode. Specifically, the circuit is a non-inverting buck-boost converter that has very little output filter capacitance. Current, delivered from a DC source, is stored in an inductor and then released into the load. The switch timing is such that all of the inductor current, and thus the energy, is allowed to dissipate in the load before the next charge cycle begins. In this way, since frequency and inductor current are programmable, average power is controlled. Typical values for energy and frequency on the SpinSat are 0.002 Joule and 100 kHz, respectively, which amounts to 200 W of ignition power, including losses. Since the current is limited on a per-cycle basis, intermittent short-circuits are tolerated.