Starlink 4–7 doomed by the Sun
I’ve started branching out, writing less strictly rocket news things for Cosmoquest’s Daily Space news show.
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One of the more unusual press releases this week came from SpaceX, providing an update on the Starlink 4–7 launch which we covered last week. It turns out that a geomagnetic storm that produced an impressive aurora visible in the northern U.S. also puffed up the Earth’s atmosphere to the point where up to 40 of the 49 satellites launched last week will decay from orbit uncontrollably.
(update 2/15/22: 11 Starlinks survived to begin orbit raising, not the worst case of 9
The solar storm heated up the atmosphere. When you heat things up, they move apart, so the satellites at a higher altitude experienced more drag than usual from the extra air molecules. SpaceX controllers turned the satellites into safe mode, a configuration that reduces drag as much as possible. Unfortunately, the drag was too much, and some of the satellites were not able to come out of safe mode and begin to raise their orbits. So instead, they will decay from orbit in the next few days.
Starlink satellites are launched into a low 210×340-kilometer orbit for checkouts before they are raised to the operational orbits at 550 kilometers altitude. This approach helps clear the low Earth orbit of defective satellites quickly, as a non-zero number of Starlinks have been dead on orbital insertion. According to statistics kept by Jonathan McDowell, 201 Starlinks have been deorbited or decayed uncontrollably since the first launch in 2019. That’s over three entire launches’ worth of satellites lost to various defects. Even if the propulsion system checks out, the communications payload may not be functional, so the satellite will be deorbited.
Fortunately, the low orbit also means that the satellites have very little risk of colliding with any other satellites on their way back down into the atmosphere, and the satellites are designed to burn up completely in the atmosphere. This is an example of good orbital stewardship by the Starlink project, but they’re by no means perfect.
Back in 2019, during the early stages of the satellites’ deployment, ESA’s Aeolus weather satellite had to fire its thrusters to avoid a collision with a Starlink satellite that SpaceX didn’t move. The International Space Station has had to maneuver out of the way at least once because of close passes of the tension rods used to hold the satellites on the second stage. More recently, the Chinese space station Tianhe had to perform two avoidance maneuvers in 2021, in July and October, to avoid being hit by Starlink satellites. This resulted in a formal complaint to the United Nations.
Overall, this is a massive W for the Sun in the fight against mega-constellations! Nature is healing. Or something like that.
This problem will become even more of an issue as the Sun gets more active; we’re just getting out of the lowest part of the solar cycle, and it’s only gonna get worse. If this keeps happening, we may need to coin a new term for an artificial meteor shower when large numbers of failed Starlinks reenter in a short period.
The increased solar activity may also impact a new satellite being developed by a consortium in Singapore. Nanyang Technological University and others plan to launch a 100-kilogram microsatellite to a 250-kilometer orbit, or Very Low Earth Orbit. The satellite will be able to obtain a much higher resolution for its imaging system than satellites in a higher orbit but at the expense of needing more propulsion. Another investigation on the satellite will gather data on spacecraft charging, a problem where spacecraft essentially get static electricity on their surfaces, damaging them. The satellite will use an ion engine constantly providing a small amount of thrust to stay in orbit. Once its mission is complete, the engine will be turned off, and the satellite will decay in days, not leaving any debris in orbit.
More Information
SpaceX press release (via archive.today)