Resistojet Propulsion Systems

Space-based Resistojets

EPL offers complete ammonia propulsion systems at nominal power levels of 100 W and 450 W. Our propulsion system design offers wide-ranging modularity for power and propellant subsystems which enables our customers to meet their specific mission requirements. The APS units feature ammonia gas storage and flow control, and a dedicated command, control, and telemetry system. All hardware is fully qualified for space use. The nominal 450 W resistojet featured has a demonstrated life of at least 75,000 N·s with 16,500 demonstrated heat exchanger cycles. The APS 500 system offers an option of a fully integrated 440 Whr battery pack. This pack functions as the primary power source for both the spacecraft BUS and the APS 500 propulsion system. First flight of the APS-500 resistojet will occur in support of Atomos Space on SpaceX’s Transporter-10 in the first quarter of 2024.

APS 100

EPL offers the battery operated APS 100. This small capable propulsion system uses liquid ammonia which self-pressurizes at 125 psia at 20 C. Ammonia was the first green propellant, it freezes at -80 C and has no condensable products to affect spacecraft surfaces. With high thrust and a specific impulse of 280 s, the APS 100 is well suited to spacecraft in the range of 10 kg to 50 kg. 

APS 100 System Wet2.63 kg
Specific Impulse280 s
Thrust28 mN 
Power100 W
Turn on Time to Full Thrust from Cold5 s
Total Impulse2,200 N-s
Demonstrated Resistojet Assembly Total Impulse6,050 N-s
Idle Power Requirement1.5 W
Operating/Non-Operating Temperature Range-25 C to 60 C / -40 C to 60 C
Communication InterfaceRS-485
Envelope2.5 U

APS 500

This high performance propulsion system uses liquid ammonia which self-pressurizes at 125 psia at 20 C. Ammonia was the first green propellant, it freezes at -80 C and has no condensable products to affect spacecraft surfaces. With a thrust of 0.15 N at a specific impulse of 350 s, the APS 500 offers excellent propulsion capability for spacecraft in the range of 50 kg to 300 kg.

APS 500 System Wet13.4 kg
Specific Impulse350 s
Thrust0.150 N
Power450 W
Turn on Time to Full Thrust from Cold15 s
Total Impulse 25,200 N-s
Demonstrated Resistojet Assembly Total Impulse75,000 N-s
Idle Power Requirement3 W
Operating/Non-Operating Temperature Range-25 C to 60 C / -40 C to 60 C
Communication InterfaceRS-485
Envelope27,300 cm3

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