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SpaceX Files FCC Application For Internet Access Network With 4,425 Satellites (geekwire.com)
An anonymous reader quotes a report from GeekWire: SpaceX has laid out further details about a 4,425-satellite communications network that's expected to provide global broadband internet access, with its Seattle-area office playing a key role in its development. The plan is explained in an application and supporting documents filed on Tuesday with the Federal Communications Commission. In the technical information that accompanied its application, SpaceX said it would start commercial broadband service with 800 satellites. That service would cover areas of the globe from 15 degrees north to 60 degrees north, and from 15 degrees south to 60 degrees south. That leaves out some portions of Alaska, which would require a temporary waiver from the FCC. Eventually, the network would grow to 4,425 satellites, transmitting in the Ku and Ka frequency bands. "Once fully deployed, the SpaceX system will pass over virtually all parts of the Earth's surface and therefore, in principle, have the ability to provide ubiquitous global service," SpaceX said. The satellites would orbit the planet at altitudes ranging from 714 to 823 miles (1,150 to 1,325 kilometers) -- well above the International Space Station, but well below geostationary satellites. SpaceX said it would follow federal guidelines to mitigate orbital debris. Each satellite would weigh 850 pounds (386 kilograms) and measure 13 by 6 by 4 feet (4 by 1.8 by 1.2 meters), plus solar arrays, SpaceX said. Operating lifetime was estimated at five to seven years per satellite.
The proposal’s technical attachment does contain a reasonable de-orbiting plan for the satellites, involving reducing the perigee to around 300 km which would result in a fairly rapid re-entry. The problem is that guidelines about time to removal (including the remarkably arbitrary 25 year recommendation) are just that: guidelines. There is no real international agreement about this either. Satellite manufacturers currently do little more than pay lip service to debris mitigation, and will use the cheapest, untested debris removal technology they can, with little expectation that it will actually work. Beyond an altitude of 600-800 km (depending on solar activity levels etc.) solar radiation pressure overtakes atmospheric drag as the dominant force acting on a satellite. SRP generates tiny forces which tend not to be applied in a way likely to accelerate deorbiting. The satellites as described in this article are likely to have a ballistic coefficient which will leave them in orbit for hundreds, if not thousands of years in the very likely case that their end-of-life manoeuvre fails. There just isn’t an incentive for Space-X to make it reliable.
The ironic thing is that it is definitely in their interest. If they hose things and satellites start getting destroyed with debris going everywhere in that orbit, Kessler Syndrome will be definitely a show-stopper and not just shut SpaceX down, but pretty much endeavor that goes past the atmosphere. This is already happening, with the ISS already having a solar panel get perforated by debris, and occasionally having to do maneuvers to avoid larger items.
Unless someone has a magic cure for getting space debris to just give up and fall into the atmosphere, fuck-ups by any satellite maker can affect every single space venture there is to the point where launching anything into space becomes an impossibility.
Have you bothered reading the PDF ? It has a quite long description of the deorbiting parameters, which involve putting them in elliptic orbit with perigee of 300km, meaning if they miss and only reach 400km, they're only good for 2.9 years before orbital decay.
I made some calculations, lowering the perigee from 1075km to 3000km is actually relatively cheap, some 200m/s Delta V. Depending on the Isp of the engine, and the total mass (not clear if the 386kg are with or without propellant), we're speaking of 25-40kg op propellant. Make that 30-50kg and aeorbraking is not even needed because you're impacting the ground. Barely significant compared to the total mass.