Three Swift Kicks: PUNCH fires a novel thruster on-orbit

@punch-mission.bsky.social

PUNCH successfully fires a new kind of rocket engine Between 2025 April 2 and 2025 April 3, the WFI-2 spacecraft successfully "hot-fired" its onboard Hydros rocket engine three times in a row, unattended – a milestone for PUNCH. Top plot showspressure in the tanks as water is electrolyzed to make fuel (which is then burned). Reaction wheel speeds show repeatable torque impulses from each thruster firing.

PUNCH will maintain the constellation with a novel, water powered, shot-glass-sized rocket engine attached to each spacecraft. Each spacecraft carries about a British pint (600g) of water in a small canister. To run the engine, PUNCH electrolyzes about 1/10 tsp (0.5 mL) of water, building up small stores of hydrogen and oxygen at about 200 psi. Then it burns the fuel in just a few seconds. Each cycle delivers a "kick" of about one inch/sec (2 cm/sec): just enough to correct for small orbital shifts and keep the constellation stable. PUNCH is the first space mission to use this type of engine, which carries safe propellant but is complex to operate.

Each WFI needs to fire its thruster hundreds of times, reliably and repeatably, over the mission. On 2-April, as part of its commissioning, the WFI-2 spacecraft demonstrated its first three perfect charge-and-fire cycles, increasing drift rate to help arrive on-station by early June.

(This is PUNCH Nugget #6; nuggets are archived at the PUNCH website.)

punch-mission.bsky.social
PUNCH mission

@punch-mission.bsky.social

Four spacecraft, one instrument … imaging almost nothing at all.
PUNCH is a polarizing wide-field imager, distributed across four
orbiting spacecraft, to track space weather (and solar wind) across
the heliosphere. (Non-NASA account for the mission team).

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