MOUNTAIN VIEW, California — Satellite electric propulsion startup Apollo Fusion is midway through a 4,000-hour life-cycle test of its Apollo Constellation Engine, ACE, which is aimed at constellations of communications satellites where each satellite weighs between 30 and 1,000 kilograms.

The company said 2017 testing at The Aerospace Corp. confirmed ACE’s overall system performance. Several orders, from unnamed customers, have already arrived even before the life-cycle testing concludes.

Apollo has its own demonstration satellite launching this summer into low Earth orbit. Further down the . . .

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