Japan’s Hayabusa2 spacecraft has lost the last ion engine that was still propelling it toward a second asteroid target, forcing the Japan Aerospace Exploration Agency to stitch together spare components from failed thrusters in a repair strategy borrowed from the original Hayabusa mission.
Engine B, the only unit JAXA had kept in reserve during the round trip to Ryugu, broke down in mid-August after carrying most of the load on the extended voyage, agency sources told Japanese media on Thursday. Engineers had already tried and failed to restart it. A close inspection found the ion source dead while the neutralizer still worked—mirroring failures on engines C and D, whose neutralizers failed but ion sources remain usable.
Frankenstein fix before a 2031 deadline
JAXA now plans to route power through engine B’s functioning neutralizer and engine D’s still-working ion source, effectively building one hybrid thruster from two broken ones. The agency aims to restart that patched unit in the second half of October, according to the reports.
Whether Hayabusa2 can still reach asteroid 1998 KY26 in 2031 depends on how much the hardware has degraded and how much delta-v the hybrid engine can still deliver. Hayabusa2 delivered Ryugu samples to Earth in December 2020 and then set course for the much smaller body, which poses a navigation challenge even with four healthy thrusters.
Engines pushed past their design limits
Of the probe’s four ion engines, units A, C and D had deteriorated so much that JAXA leaned on B for the extended mission. That is the same pattern engineers faced on the first Hayabusa probe, which limped home from asteroid Itokawa in 2010 after similar thruster failures and component swaps in flight.
Yuya Mimasu, who leads JAXA’s Hayabusa2 extended mission team, said in comments reported Thursday that the agency would keep working with the ion engines “until the very end,” even as the hardware operates beyond its expected limits.
What comes next
If the October restart succeeds, controllers will assess trajectory options toward 1998 KY26. A miss on the 2031 arrival window would not erase the Ryugu sample return, but it would cap the extended mission short of its planned second rendezvous.
JAXA has not published a formal timeline revision. Observers at Japanese science ministries will watch the patched engine burn closely, because ion propulsion failures have defined both Hayabusa missions and because deep-space fuel margins leave little room for repeated repair attempts.