this post was submitted on 03 Jul 2026
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38
End of the blue glow: BepiColombo turns off solar electric propulsion for Mercury arrival (www.esa.int)
submitted 1 day ago by Delta_V@lemmy.world to c/space@mander.xyz
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...After a long, challenging cruise phase with nine planetary flybys (one by Earth, two by Venus and six by Mercury), BepiColombo finally closed this chapter last Monday by permanently switching off its SEP thrusters...

Without any other source of propulsion, BepiColombo will follow a “ballistic” or free-falling trajectory as it initiates its first key arrival manoeuvre – MTM separation – on 3 September 2026.

After the MTM is ejected, the remaining spacecraft composite (MPO-Mio-MOSIF) will continue its planetary approach using MPO’s chemical propulsion system. This system will adjust the spacecraft’s trajectory ahead of the critical Mercury orbit insertion manoeuvre on 21 November, then guide it into Mio’s deployment orbit in early December before finally lowering MPO into its science orbit by March 2027...

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[–] Delta_V@lemmy.world 17 points 1 day ago* (last edited 1 day ago) (2 children)

I love the Kerbal-esque architecture of this mission.

-An ion drive stage drops it down a deep hole, toward the sun, then spends all its fuel slowing down almost enough to be captured by Mercury's gravity instead of just flying by it at screaming fast speed. The empty fuel tanks and ion engines get thrown away when they're used up.

-Then one of the stacked probes turns on its chemical engines for the capture burn, and it ditches some of its sun screen.

-When its just barely captured in a highly elliptical polar orbit, it releases a satellite equipped with its own independent systems.

-Then it maneuvers to a lower orbit that's optimal for the other satellite.

Mercury is hard to get to, and only one other space craft has ever orbited it: MESSENGER. Now there will be 2 more delivered with a single launch.

[–] Rubisco@slrpnk.net 2 points 18 hours ago* (last edited 18 hours ago)

9 flybys?! And no "warp to encounter".

The stacked spacecraft left Earth with a hyperbolic excess velocity of 3.475 km/s (2.159 mi/s). Initially, the craft was placed in a heliocentric orbit similar to that of Earth. After both the spacecraft and Earth completed one and a half orbits, it returned to Earth to perform a gravity-assist maneuver and was deflected towards Venus.

Following its Earth flyby in April 2020, BepiColombo was briefly mistaken for a near-Earth asteroid, receiving the provisional designation 2020 GL2.

Two consecutive Venus flybys reduced the perihelion near to the Sun–Mercury distance with almost no need for thrust. A sequence of six Mercury flybys lowered the relative velocity to 1.76 km/s (1.09 mi/s). After the fourth Mercury flyby in 2024, the spacecraft is in an orbit similar to that of Mercury and remains in the general vicinity of the planet.

Yeah, Earth was a little distracted in April of 2020.

And then came the thruster issues:

On 15 May 2024, ESA reported an issue preventing the spacecraft's thrusters from operating at full power during a scheduled manoeuvre on 26 April 2024.[54] On 2 September 2024, ESA reported that to compensate for the reduced available thrust, a revised trajectory had been developed that would add 11 months to the cruise, delaying the expected arrival date from 5 December 2025 to November 2026.

What a ride! Very KSP.
The way Ap is drawn in at Mercury reminds me of airbraking at Kerbin.

So fucking cool. Hats off to the team.

https://en.wikipedia.org/wiki/BepiColombo

[–] wraekscadu@vargar.org 6 points 1 day ago

Thanks for the writeup! Interesting project indeed!