Apollo Constellation Engine (ACE)




A smaller, lighter, better electric propulsion system

The Apollo Constellation Engine (ACE) is a Hall effect thruster propulsion system with best in class performance at a fraction of the size. ACE leverages the past 50 years of Hall thruster research in a clean sheet design with major innovations, including:

  • Heaterless, center-mounted, instant-start cathode
  • Propellant management with no moving parts
  • Novel magnetic lensing and magnetic circuit
  • Advanced high temperature materials
  • 95% efficient single board PPU
  • Proprietary propellant

Solves the biggest satellite pain points: mass and volume

The clearest way to compare the mass and volume of propulsion systems is to measure their performance in total impulse per mass (N-s/kg) and total impulse per volume (N-s/L). ACE offers 3x more impulse per mass and volume than other systems.

Impulse per system volume, N-s/L
250kg sat, 500m/s delta-V, 1 thruster, with propellant
Blue bars represent competitive systems.

Impulse per system mass, N-s/Kg
250kg sat, 500m/s delta-V, 1 thruster, with propellant
Blue bars represent competitive systems.

ACE has extraordinary performance

INPUT POWER 400 W 500 W
THRUST 24 mn 33 mN
SPECIFIC IMPULSE 1,250 s 1,500 s
TOTAL IMPULSE 200 kN-s 200 kN-s
DRY MASS 4.5 kg 4.5 kg

This enables smaller spacecraft and larger payloads


Tanks are compact and scale to fit every mission

Hall thrusters accelerate ions to speeds faster than escape velocity

As ACE's propellant is ionized, the electrical field accelerates it to speeds up to 15 km/s. In comparison, this is far faster than escape velocity. Objects in LEO traveling faster than 7.8 km/s escape Earth's gravitational pull and leave Earth's orbit entirely.

Uses rad-tolerant or rad-hard, 95% efficient, single board PPU

ACE includes a proprietary Power Processing Unit (PPU) which is radiation hardened by design, replacing failure-prone microprocessors with simple and reliable components wherever possible. The design prevents gate ruptures and latchups, is tolerant of transients and upsets, and is suitable for missions from LEO through the Van Allen belts to GEO. The PPU is 95% efficient, and while many PPUs are the size of a desktop PC, ACE’s PPU is a single circuit board. Learn more

Choose one or two thrusters for constellations, six to eight for LEO-GEO orbit raising

ACE can be configured with multiple thrusters and PPUs to handle a wide range of missions, from the smallest earth observation satellites with 100W Orbit Average Power, up to large communication satellites with multiple kilowatts of solar power. With multiple thrusters, LEO-GEO raises can take as few as 12 weeks.

Tested to 12,000 cycles and 1,200 hours to date

Performance testing with xenon and proprietary propellants has included over 1,200 hours of operation on a single thruster with over 2,000 hours operation overall, with 12,000 start/stop cycles performed on a single thruster in automated testing. Ongoing testing continues in response to specific customer requirements.

The Aerospace Corporation performance tests matched our xenon results within 0.5%

The Aerospace Corporation, a federally funded research and development center, tested our thruster at the power levels between 260 W and 500 W with Xenon. In this power range the thrust varied from 15 to 29 mN, system Isp varied from 952 to 1407 seconds, and efficiency from 28% to 41%. A complete test report is available.

ACE is a complete integrated system

Compact thruster

ACE includes a Hall effect thruster with best in class performance at a fraction of the size. ACE leverages the past 50 years of Hall thruster research in a clean sheet design with major innovations.

Rad tolerant PPU

The ACE Power Processing Unit (PPU) is radiation hardened by design, replacing failure-prone microprocessors with simple and reliable components. Its single circuit board design is 95% efficient. Learn more

DOT certified tank

ACE tanks are sized to fit the unique requirements of each customer mission. The tanks are designed and manufactured by Apollo to meet DOT, ODAR, system integrator, and launch range requirements.



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 architectures 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



ACE is made in the US and available in Q3 2019

Apollo has partnered with a high-volume aerospace contract 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 CM facilities