Apollo Xenon Engine (AXE)

A NASA JPL-designed thruster with rad-hard PPU for high thrust, high impulse missions

The Apollo Xenon Engine (AXE) is an electric propulsion system using a Hall thruster designed by JPL and industrialized by Apollo, matched to an Apollo radiation-hardened PPU and propellant management system. Class-leading features include:

  • World's first 1,000W magnetically shielded Hall thruster with 2 MN-s lifetime
  • Highest efficiency 1,000W Hall thruster in the world
  • Multi-propellant operation with xenon, krypton, and proprietary propellants
  • 100 kRad radiation hardened, 95% efficient, single board PPU
  • High thrust-to-power at 55 mN/kW

Matured for eight years by NASA JPL

From 2011-2019, NASA JPL invented, developed, tested, and matured the MaSMi (Magnetically Shielded Miniature) Hall thruster. Significant thruster performance improvements were realized over the life of the program, including peak thrust (increased by 200%), peak total Isp (increased by 65%), and peak total efficiency (increased by 104%). A lifetime analysis campaign consisting of both direct erosion measurements and high-fidelity plasma simulations suggest a throughput capability corresponding to a useful lifetime of >15 kh.

MaSMi-40 (2012)1
Demonstrated MS was possible at sub-500W; poor performance

MaSMi-60-LM1 (2014)2
First low-power Hall thruster to demonstrate fully shielding topology

MaSMi-60-LM2 (2016)3
Significantly improved performance through improved magnetic circuit

MaSMi-DM (2017)4
Exceptional performance, center cathode, & optimized anode manifold

MaSMi's performance meets or exceeds typical requirements for interplanetary missions and those for commercial smallsats in LEO and MEO. This thruster, industrialized by Apollo Fusion and paired with a higher-power version of Apollo's efficient, radiation-hardened, single-board, single-operating point PPU, form the basis of AXE – an integrated electric propulsion system with outstanding performance for spacecraft with >750W of Orbit Average Power.

Industrialized by Apollo under exclusive commercial license

JPL issued an exclusive commercial license of the MaSMi Hall thruster to Apollo Fusion in March 2019. Apollo Fusion’s Design-For-Manufacturing (DFM) improvements will enable high quality production in the significant volumes required for large constellation customers. These updates will reduce cost, lead time, and mass while preserving the key features – including anode gas distributor geometry and magnetic field topology – which contribute to MaSMi's strong performance. Apollo expects to complete these industrialization activities by the end of 2019:

    • Eliminating exotic materials
    • Eliminating sole source vendors
    • Reducing long lead time items

    • Reducing use of high cost materials
    • Redesigning to simplify assembly
    • Qualifying to constellation requirements

Highest efficiency 1,000W Hall thruster in history

DRY MASS 15 kg

Magnetic shielding for 2 MN-s total impulse

Typically, during Hall thruster operation the plasma causes propellant ions to erode the ceramic thruster head. This is a significant life-limiting factor for thrusters like ACE. But the thruster used in AXE was designed to be magnetically shielded, resulting in a 10x improvement in lifetime, up to 2 MN-s.

Uses 95% efficient, single board PPU, radiation hardened to 100 kRad

AXE 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 is a single circuit board. Learn more

Choose one or two thrusters for constellations, four to eight for LEO to GEO, the Moon, or Mars

AXE can be configured with multiple thrusters and PPUs to handle a wide range of missions, from communication satellites with >750W Orbit Average Power up to third-stage orbit raising tugs needing 7 km/s delta-V. With multiple thrusters, LEO-GEO raises can take as little as 12 weeks, and missions to Low Lunar Orbit and Mars become possible starting from 500km LEO injection.

AXE is a complete integrated system

Compact thruster

AXE includes a Hall effect thruster with 55% efficiency and magnetic shielding for 2 MN-s of total impulse. AXE was matured by NASA JPL as a clean sheet design with major innovations.

Rad hard PPU

The AXE 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

AXE tanks are sized to fit the unique requirements of each customer mission. The propellant management system is designed and manufactured 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 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 US and flight ready in 2020

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 CM facilities