Slashdot Mirror
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.
4425*850*$4000=$15 045 000 000
so $26 billion would be enough.
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.
First off, it's not "in addition to", it's "instead of". Earth fiber networks don't run on fairy dust either, they also consume power. The internet is one of the biggest power consumers on Earth. That's just the way it is.
Doing my own math. You could fit ~141 in a Falcon Heavy to LEO. They don't say how many are actually planned, or even whether they plan to use Falcoln 9 or Heavy. Taking into account the higher altitude and practical considerations, let's say 60 satellites per flight on Heavies. So that's about 75 flights. Per FH flight, RP1 mass is ~400 tonnes and LOX mass ~935 tonnes. LOX is cheap and low energy to produce, so let's focus on the RP1. Total that's 30k tonnes of RP1. Which is 1,4TJ, or about 380 MWh higher heat value, which is 100-200MWh electricity generation potential. I didn't find how much energy Chicago consumes per year, but a reference on MIT's School of Engineering states that NYC consumes 60 TWh electricity per year. So I think you're way off in your estimate.
It's times like this I wish I had a friend named 'The Professor'.
how do you solve the logistical problem of replacing 10 satellites all in completely different positions around the earth in one launch?
You don't. The way Iridium handles it is having some of the satellites in orbit allocated as spares and not in active service. They have 66 active birds plus six spares. The spares run in a different orbit which circles the earth faster than the active constellation but can still easily transfer to the correct orbit, minimizing fuel needs for activating one in exchange for a longer time spent waiting for the orbits to sync up properly for the transfer.
Basically you set things up like a large "cloud" host where there's enough spare capacity that individual device failures just aren't really a priority and you can replace the failed hardware in bulk every so often rather than having to do something one-off immediately.
I used to get high on life, but I developed a tolerance. Now I need something stronger.
Beyond this, I expect that a lot of these would actually be nearly "free" - I would not be in the least surprised if their plan is to pack these as secondary payloads in existing launches to take up the remaining payload capacity of the launch vehicle.
Also, spending a few billion years on average during operation is a very small amount compared to the amount spent globally on internet infrastructure.
It's times like this I wish I had a friend named 'The Professor'.
There are some issues with these calculations.
1) The per pound price:
- The prices you used are per kilogram, not per pound
- The prices do not take into account the first stage reusability that will presumably become standard by the time the sats are launched
- If we use the Falcon Heavy costs with reusability (e.g. from here) we get $50mil/(0.7*119930) = about $600 per pound.
- The $600 price per pound includes the SpaceX profit margin. If that is not taken into account the price would be even lower.
2) SpaceX will first launch only 1600 sats to make the system operational. From then on the future expansion can be funded by the operational profits.
Given the above calculations, the launch prices for getting the system to work will be 1600*850*600 = $816 million
That is well within the SpaceX financial capabilities.
Now, the above assumes that the FH launches of the sats would be mass limited, rather than volume limited. I suspect that in reality they would be volume limited, however, thus the price would be higher. In any case it would be much lower than your original estimate.