An engine for every constellation.

Apollo Constellation Engine (ACE)

Xenon and Krypton electric propulsion system with best in class performance for spacecraft with less than 1 kW of power.


Xenon and Krypton electric propulsion system with a magnetically shielded thruster and 1.5 MN-s total impulse for spacecraft with more than 1 kW power.

Xenon, Krypton PROPELLANTS Krypton, Xenon
400 W INPUT POWER 1,450 W
~25 mN (Xe)
~18 mN (Kr)
THRUST ~60 mN (Xe)
~54 mN (Kr)
~1,400 s (Xe)
~1,300 s (Kr)
~1,800 s (Kr)
300 kN-s (Xe) TOTAL IMPULSE 1.5 MN-s
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Complete systems available with our partners

Compact thrusters

ACE and ACE Max include an instant-start center mounted cathode and compact design. Each thruster leverages the past 50 years of Hall thruster research in a clean sheet design with major innovations.

Rad hardened PPU

The Apollo PPU (Power Processing Unit) is radiation hardened by design, replacing many microprocessors with simple and reliable components. Its single circuit board design is 95% efficient.

Feed systems with heritage

Apollo’s krypton configurations include gaseous feed systems in single and multi-thruster configurations with flight-proven components from a respected industry partner with heritage.

COPV propellant tanks

Apollo’s krypton configurations include tanks sized to fit the unique requirements of each customer mission with flight-proven COPV construction rated to 2,700 psi or 4,000 psi.

Why constellations prefer Apollo

  • Our thruster, PPU, and feed system have been designed and tested to work together
  • Our performance specifications often exceed requirements from constellation primes
  • Our manufacturing partner is ISO9001/AS9100 certified and US-based
  • Our systems can be delivered as an integrated, tested propulsion module
  • Our US-made propulsion system is attractive to US government customers

Tested to meet or exceed all customer requirements

Apollo and our suppliers are completing qualification testing in line with ESA, MIL, and ISO standards. Test flow plans, test order, test procedures, and test levels are set to meet or exceed the performance, physical, electrical, environmental, thermal, and radiation requirements set by customer agreements. Learn more

High volume, high reliability acceptance testing facilities

Apollo's research and development lab has five vacuum chambers and one thermal-vac chamber, allowing for hundreds of tests per week. This has enabled the development of new system designs in weeks instead of years. These facilities are fault-tolerant by design and able to grow to enable acceptance testing of hundreds of systems per month. Learn more

Manufactured in the USA

Apollo has partnered with a high-volume aerospace manufacturing partner based in Silicon Valley. Apollo’s manufacturing partner specializes in high reliability aerospace and defense products and has the capacity to produce hundreds of units per month to Apollo Fusion customer specifications. Learn more

  • Manufacturing partner is ISO9001, AS9100 certified
  • Manufacturing process based on statistical process control
  • Apollo has offices on-site at manufacturing partner facilities

About Apollo Fusion

Apollo Fusion is a venture-funded small business led by Mike Cassidy (CEO and co-founder). Mike previously co-founded four successful startups and was a Vice President at Google where he led Project Loon, a high-altitude balloon telecommunications system using Free Space Optical Communications. The Apollo Fusion team includes domain experts in electric propulsion, Hall thrusters, aerospace engineering, systems engineering, electrical engineering, and software engineering. Our team has designed and built hardware on over 400 spacecraft that have reached orbit.

Planning a constellation? Reach out to us at and let's talk.