Apollo Power Processing Unit (PPU)

Apollo PPU for LEO

Radiation tolerant single circuit board design

ACE includes a 95% efficient, single-operating point PPU for 400W and 500W set points that is radiation tolerant to 20 kRad TID and has evolved significantly over the past 2 years in both capability and footprint. This PPU has successfully operated thrusters in thermal vacuum chambers, has been radiation tested, and has been shock and random vibration tested.

Remarkably compact

The design choice to standardize a single operating set point was made to reduce complexity, mass, and volume. While many PPUs are the size of a desktop PC, ACE’s PPU is a single circuit board.

Performance and specifications

INPUT VOLTAGE 22-38 VDC (unregulated)
MASS 1.5 kg

Apollo PPU for MEO/GEO

Radiation hardened PPU developed for MEO and GEO

In early 2018, Apollo's PPU for LEO had 70 active components and only tolerated a total ionizing dose of 10 kRad. Later that year, Apollo completed a radiation hardened PPU redesign for a US government customer in less than 6 months.

Rapid design improvements came when Apollo acquired team members experienced in the design and assembly of flight hardware which flew on Planet Labs and SpaceX missions. Recent testing included heavy ion testing, six rounds of proton bombardment testing, and additional rounds of shock/vibe testing.

  Advanced simulations & prototype iteration with Google-derived high reliability software practices Parts screening Radiation testing Shock/vibe testing LEO PPU GEO PPU
Design revision 1 2 3 4 5 6 7 current current
Added team from   Stanford Planet SpaceX          
Collaborated with         RTS UC Davis Planet    
Rad tolerance 10 kRad 10 kRad 25 kRad 100 kRad       20 kRad 100 kRad
Active (distinct) parts 70 70 70 14       14 14
Optocouplers yes yes rad-hard removed       rad-hard -
High current - supported supported supported       supported supported
Fault detection - - robust robust       robust robust
Protection circuits - - robust robust       robust robust
Mass 1.5 kg 1.5 kg 2.5 kg 1.5 kg       1.5 kg 2.5 kg

The PPU is now radiation hardened by design, replacing any 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.

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

Apollo PPUs are made 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 CM facilities