For the Lunar Mission BW1 the PERSEUS satellite will evaluate the following technologies:

The thermal arcjet thruster TALOS is developed as one of the main propulsion systems for the Lunar Mission BW1. The propellant used for this thruster is ammonia. A high discharge voltage in the range of 2000 V is applied to cathode and anode. Ignition is accomplished via a Paschen-discharge. The arc between cathode and anode heats up the propellant causing dissociation and ionization of the propellant. The propellant is then expanded through a nozzle converting the thermal energy into directed kinetic energy. As the exhaust velocity is inversely proportional to the molecular weight of the propellant, light propellants are preferred to achieve a high exhaust velocity and, hence, thrust. This includes hydrogen, hydrazine and ammonia. For reasons of storability, hydrogen is only used for laboratory thrusters, whereas hydrazine and ammonia are used in flight applications. Using hydrazine for north-south station keeping applications on board of geostationary satellites is advantageous since it may be used for a combined propulsion feed system together with the chemical apogee thruster. The performance characteristics of arcjet thrusters depend on the total energy input, mass flow range and propellant used.

Laboratory test of the TALOS thermal arcjet thruster

The pulsed plasma thruster ADD SIMP-LEX is developed to form the main propulsion system for the operation on PERSEUS and the long-term operation on the later Lunar Mission BW1.
ADD SIMP-LEX is a pulsed plasma thruster (PPT) using the solid propellant PTFE (Polytetrafluoroethylene). The thruster itself comprises the capacitor bank, the spark plug and the electrodes. For the operation a functional power supply as well as a propellant feed system are necessary. In order to verify the operability, one complete propulsion system including thruster, power supply and propellant feed system will be implemented in the satellite. On-board diagnostics and sensor systems of the satellite will determine whether the operation in real space shows comparable performance characteristics as the ground experiments. Further, lifetime of the components will be tested igniting several thousands of pulses also in regard to a later application as cruise engine (>10 Mio. pulses). Propellant feeding poses a challenge concerning the storage and the unproblematic functionality. The technology developed will be tested on-board.
The results of the experiments will influence the development of ADD SIMP-LEX for the Lunar Mission BW1. Further ground testing might be necessary to result in a propulsion system suitable to transfer the satellite successfully to the moon.

Laboratory model of the ADD SIMP-LEX pulsed plasma thruster

The attitude and orbit control system for PERSEUS has to satisfy two very different demands posed by the mission objectives.
First, in the Engine Test Phase, it has to provide the proper attitude to perform orbit maneuvers with both thrusters. In this phase the ACOS has to respond to large disturbance torques generated by thrust misalignments. Even though the demands on attitude accuracy are quite low (about 1 deg), the stability of the attitude over a prolonged thrust phase in the presence of large disturbances makes the AOCS design challenging.
Later, during the Science Phase, the absolute pointing accuracy of the satellite becomes the dominant requirement. In order to perform astronomical observations, the satellite has to be oriented towards the target star with an accuracy of 7 arcsec (about two thousandth of a degree) during the whole time of the measurement.
To achieve those requirements with the attitude control hardware already used for the Flying Laptop, extensive sensor data processing and ground testing has to be performed.