SpaceX has garnered much praise and criticism with the creation of Starlink, a constellation that will one day provide broadband Internet access worldwide. To date, the company has launched over 800 satellites and (as of this summer) produces them at a rate of about 1
However, there were some problems along the way. In addition to the usual concerns about light pollution and radio frequency interference (RFI), there are failure rates that these satellites have experienced. In particular, about 3% of its satellites have been unresponsive and no longer maneuver into orbit, which could be dangerous for other satellites and spacecraft in orbit.
To prevent collisions in orbit, SpaceX equips its satellites with Hall-effect krypton motors to elevate their orbit, maneuver in space, and deorb at the end of their lives. According to two recent reports sent by SpaceX to the Federal Communications Commission (FCC) in the summer (mid-May and late June), several of their satellites have lost their ability to maneuver as they were deployed.
Unfortunately, the company did not provide enough information to indicate which of their satellites were affected. For this reason, astrophysicist Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics (CfA) and the Chandra X-ray Center presented their own analysis of the orbital behavior of satellites to suggest which satellites have failed.
The analysis is published on McDowell’s website (Jonathan’s Space Report), where he combines SpaceX’s own data with US government sources. From this, he found that about 3% of the satellites in the constellation have failed because they no longer respond to commands. Naturally, a certain level of wear is inevitable and 3% is relatively low as failure rates continue.
But any satellite that is unable to maneuver due to problems with its communications or propulsion system poses a risk of collision to other satellites and spacecraft. As McDowell said Business Insider:
“I would say that their failure rate is not terrible. It is not worse than the failure rate of anyone else. The worry is that even a normal failure rate in such a huge constellation will end up with a lot of bad space junk.”
Named after NASA scientists Donald J. Kessler, who first proposed it in 1978, Kessler’s syndrome refers to the threat posed by collisions in orbit. They lead to catastrophic breakdowns that create more debris that will lead to further collisions and breakdowns, and so on. When you consider the frequency of failures and SpaceX’s long-term plans for a “megaconstellation,” this syndrome naturally retains its ugly head.
Not long ago, SpaceX received permission from the Federal Communications Commission (FCC) to deploy about 12,000 Starlink satellites in orbits ranging from 328 km to 580 km (200 to 360 miles). However, recent statements from the International Telecommunication Union (ITU) indicate that the company hopes to create a megaconstellation of 42,000 satellites.
In this case, the failure rate of 3% reaches 360 and 1260 (respectively) 250 kg (550 lbs) satellites, which over time become non-existent. As of February 2020, according to the ESA Space Waste Service (SDO), there are currently 5,500 satellites in Earth orbit – about 2,300 of them are still in operation. This means (using bare math) that a full megaconstellation of Starlink would increase the number of non-functioning satellites in orbit by 11% to 40%.
The problem of debris and collisions seems even more threatening when you consider the amount of debris in orbit. In addition to the non-functioning satellites, SDO also estimates that there are currently 34,000 objects in orbit larger than 10 cm (~ 4 inches) in diameter, 900,000 objects between 1 cm and 10 cm (0.4 to 4 inches), and 128 million objects between 1 mm to 1 cm.
Naturally, SpaceX stressed that the risk of a collision is very small. In its declarations to the FCC in April 2017, SpaceX considered the possibility of collision risks, accepting levels of satellite damage that led to the inability to perform collision avoidance procedures of 10, 5 and 1 percent. In response, the company stated that even a 1% risk is unlikely, given the following specifications and guidelines:
- Designing the Starlink constellation to go beyond NASA’s debris mitigation guidelines and an “aggressive surveillance program” to detect potential problems and affect affected satellites.
- Schedule of gradual deployment over a long period of time (which they accomplish by deploying a batch of 60 satellites per launch).
- An iterative design process that uses new technologies and upgrades, avoiding the launch of more satellites identified as problematic, and deorbing those identified as risky.
Last but not least, SpaceX emphasized that it was conducting simulations, which was confirmed by information from the USAF Joint Space Operations Center (JSpOC) and NASA’s orbital debris engineering model. From this, they claimed that based on a satellite failure rate of 1% and a lack of corrective maneuvers, there was “an approximately 1% chance that every failed SpaceX satellite would collide with a piece of tracked debris in a decade.”
The deployment of 60 Starlink satellites confirmed pic.twitter.com/x83OvjB4Pa
– SpaceX (@SpaceX) October 6, 2020
There is also a possible scenario in which Starlink satellites naturally deorb if their propulsion systems fail and they are unable to increase their orbit or apply corrective thrust. But even with their lower orbits, compared to other telecommunications satellites, this process will still take one to five years. In the end, there are no guarantees, only vigilance and readiness.
Musk, meanwhile, announced earlier this month that with the latest batch of their satellites launched into orbit, Starlink plans to launch a beta test of its Internet service. “Once these satellites reach their target position, we will be able to release a fairly broad public beta in the northern United States and, hopefully, southern Canada. Other countries will follow as soon as we receive regulatory approval,” he wrote on Twitter.
SpaceX is looking for many more satellites for a space-based Internet network
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Quote: About 3% of Starlink satellites have failed so far (2020, October 26), retrieved on October 26, 2020 from https://phys.org/news/2020-10-starlink-satellites.html
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