SpaceX has revealed the first successful test of Starlink satellite ‘space lasers’ in orbit, a significant step along the path to an upgraded “Version 2” constellation.
In simple terms, those “lasers” are a form of optical (light-based) communication with an extremely high bandwidth ceiling, potentially permitting the wireless, high-speed transfer of vast quantities of data over equally vast distances. Of the ~715 Starlink satellites SpaceX has launched over the last 16 months, some 650 are operational Version 1 (v1.0) spacecraft designed to serve a limited group of customers in the early stages of the constellation. Prior to SpaceX’s September 3rd announcement, it was assumed that none of those satellites included laser interlinks, but now we know that two spacecraft – presumably launched as part of Starlink-9 or -10 in August – have successfully tested prototype lasers in orbit.
Ever since CEO Elon Musk first revealed SpaceX’s satellite internet ambitions in early 2015, those plans have included some form of interconnection between some or all of the thousands of satellites the company would need to launch. While a functional low Earth orbit (LEO) satellite internet constellation doesn’t intrinsically need to have that capability to function or be successful, inter-satellite links offer some major benefits in return for the added spacecraft complexity and cost.
The single biggest draw of laser interlinks is arguably the major reduction in connection latency (ping) they can enable compared to a similar network without it. By moving a great deal of the work of networking into orbit, the data transported on an interlinked satellite network would theoretically require much less routing to reach an end-user, physically shortening the distance that data has to travel. The speed of light (300,000 kilometers per second) may be immense but even on the small scale of the planet Earth, with the added inefficiencies inherent in even the best fiber optic cables, routing data to and from opposite ends of the planet can still be slowed down by high latency.
Without interlinks, Starlink and internet constellations like it function by acting more like a go-between for individual users and fixed ground stations that then connect those users to the rest of the Internet. Under that regime, the performance of constellations is inherently filtered through the Earth’s existing internet infrastructure and is necessitates the installation of ground stations relatively close to network users. If a satellite without interlinks can ‘see’ (and thus communicate with) customers but can’t ‘see’ a ground station from the same orbital vantage point, it is physically incapable of connecting those communications with the rest of the internet.
This isn’t a showstopper. As SpaceX’s very early Starlink constellation has already demonstrated through beta testers, the network is already capable of serving individual users 100 megabits per second (Mbps) of bandwidth with latency roughly comparable to average wired connections. The result: internet service that is largely the same as (if not slightly worse and less convenient than) existing fiber options. To fully realize a LEO internet constellation’s potential of being much better than fiber, high-performance laser interlinks are thus a necessity.
With laser interlinks, the aforementioned connection dropout scenario would be close to impossible. In the event that an active satellite finds itself serving customers without a ground station in reach, it would route those forlorn data packages by laser to a different satellite with immediate ground station access. One step better, with enough optimization, user communications can be routed by laser to and from the ground stations physically closest to the user and their traffic destination. With a free-floating network of satellites communication in vacuum along straight lines, nothing short of a direct, straight fiber line could compete with the resulting latency and routing efficiency.
Interlinks offer one last significant benefit: by sacrificing latency, an interlinked network will be able to service a larger geographic area by allowing the connections of users far from ground stations to be routed through other satellites to the nearest ground station. Large-scale ground station installation and the international maze of permitting it requires can take an inordinate amount of time and resources for nascent satellite communications constellations
SpaceX’s fully-interlinked Starlink Version 2 constellation is targeting latency as low as 8 milliseconds and hopes to raise the bandwidth limit of individual connections to a gigabit or more. As soon as a viable Starlink v2.0 satellite design has been finalized and tested in orbit, SpaceX will likely end v1.0 production and launches, entering the second phase of iteration after the v0.9 to v1.0 jump.
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