Starlink Questions

I got a great couple of questions on an earlier post about Starlink. My good friend Tobi asked about concerns that massive satellite internet constellations could lead to a bunch of space junk in orbit and also concerns that these constellations will cause problems for astronomers.

SpaceX, with 12,000 or more Starlink satellites in it’s completed constellation, won’t be the only company in the low-flying internet satellite game. OneWeb already has satellites in orbit and they want to put up at least 7,000 total up there. Amazon’s Kuiper hasn’t put anything in orbit yet but they want to launch at least 3,000 satellites pretty soon. And don’t expect major governments to stay out of this game. In just a few years we will have more internet satellites in low Earth orbit than all other orbiting satellites combined, working and dead. And these satellites have a fairly short lifetime, 5 years or so before they run low on fuel and must spend their last remaining fuel to de-orbit.

SpaceX is planning for the largest constellation of the companies I know about and they’re doing it seemingly responsibly. They have built Starlink satellites out of materials that will burn up completely when they de-orbit. The Starlink satellites have onboard ion propulsion thrusters powered by krypton gas. They use these thrusters to achieve their orbits, maintain those orbits against the drag of the upper atmosphere, and to de-orbit the satellites at the end of their lifetimes. Even if something goes wrong with a Starlink satellite’s thrusters, the constellation is low enough that it will only take a few years for the satellite’s orbit to decay and the satellite succumb to drag and burn up.

SpaceX is also working to mitigate Starlink’s impact on astronomy. You may have seen photos or videos of “Starlink trains” rows of lights moving across the sky. These bright satellite trains are only that bright while they’re in the process of raising their orbits. SpaceX launches the satellites into a very low orbit, about 155 miles up, and they then use precession to spread out and use their ion thrusters to raise their orbits to about 335 miles. That process takes a few months and during that time the satellites are low and clumped up and so fairly bright. SpaceX has cut down on that brightness a lot by changing the orientation of the satellites during orbit raise so they don’t reflect as much sunlight. But even when they reach their ultimate orbits, higher up and spread out, they still reflect some sunlight at dusk and dawn. SpaceX has mitigated a bunch of by outfitting all of their recently launched Starlink satellites with sun shades that eliminate a lot, but not all, of the reflection.

I think SpaceX has a firm handle on the problem of space junk. They’ve designed and built satellites and a process for replacing old satellites with new ones that will not lead to space junk. I think they’ve got less of a grip on the problems they may be creating for astronomers, especially hobbyists who may not have the tools to remove any Starlink interference from their data and images. They are working on it though and have made some real progress.

One idea I had was that SpaceX, which is after all a rocket company, could remediate some of the harm they may cause to terrestrial astronomy by offering free launch services to publicly funded (universities!) space telescopes. It costs anywhere from tens of millions to hundreds of millions of dollars just to launch a space telescope into orbit. If that barrier was gone, think about how many new space telescopes might be built, from great big ones like James Webb or Hubble to miniature ones like the BRITE nanosatellites, and everything in between.

I know that space telescopes can be more expensive to build and they can’t replace terrestrial ones for every use case, but by eliminating most or all of the launch costs, SpaceX could help usher in a new era of space-based astronomy. I think that could really help build some bridges with the astronomy community.

Starlink’s Path to Success Part 1

I previously posted some of the innovations that I believe made Starlink possible. But possible and successful are not the same thing. For Starlink to be successful, they need to make dramatic progress on several fronts and the first is launch cadence.

To provide really solid coverage to the initial (quite large, if the registrations are to be believed) group of potential customers, Starlink needs to have about 4,000 satellites in orbit. Today they have just over 1,000 satellites in service. About 1,400 will give them pretty solid global coverage but without the redundancy needed to serve as many customers as are ready to sign up. That’s because each satellite can only serve so many users in a particular area. To serve more customers in a given area means more satellites.

SpaceX launches Starlink satellites in batches of 60 with its Falcon 9 rocket. They fly “flight proven” rocket boosters for all of their Starlink missions and they have a fleet of 7 of these already been flown boosters to work with. (SpaceX keeps the cost of Starlink launches down by taking a rocket that a commercial launch customer already paid for, and relaunching it with its own Starlink payloads.) It takes them a while to refurbish and stage these rockets between flights but with some improvements to that turnaround time and if they can maintain their existing fleet size, I do believe they can dramatically improve the pace of Starlink launches.

In 2020, SpaceX had 15 launches putting 900 satellites in orbit and ideally they’d almost double that pace, launching something like 1500 sats this year and for the next couple of years as well. They’ve said they intend to launch about every two weeks and so far this year they’re hitting that pace. They’ve had some delays because of weather, both at the launch site and the booster landing barges out at sea, but it hasn’t yet knocked them off their quickened pace.

They’ve also had repeated delays with a launch of booster B1049 which has flown 7 prior missions and may be starting to show its age. SpaceX wants to get at least 10 flights out of each rocket booster before retiring them but they may find that the current Block 5 design doesn’t consistently hit that mark. SpaceX cannot afford to launch Starlink missions on new boosters so maintaining their fleet of flight proven boosters is quite important.

A further concern is the fate of booster B1059 which failed to land (crashed into the ocean) earlier this month, reportedly because of heat damage. B1059 had only flown 5 prior missions so hopefully it wasn’t wear and tear but some other issue that SpaceX can mitigate for the rest of the fleet if needed. As noted above, they can’t afford to lose too many of their flight proven boosters without it putting a real dent in their launch cadence.

In addition to an improved Falcon 9 launch cadence, SpaceX needs to make dramatic progress on its next generation rocket, named Starship. Where Falcon 9 is about 12 feet in diameter and 230 feet tall with a launch to low earth orbit capacity of about 50,000 lbs, Starship will be 30 feet in diameter and 400 feet tall with the ability to put 220,000 lbs into low earth orbit.

If all goes well with Starship, SpaceX should be able to carry about 400 satellites to orbit in one launch (compared to the 60 that Falcon 9 can hold.) Starship is also being designed to be rapidly and fully reusable so we could see amazing growth in the size of the Starlink constellation starting in two to three years when Starship should be ready to take over the Starlink missions from Falcon 9.

Starlink Innovation Part 3

The third key innovation from SpaceX that makes Starlink possible is the mass-produced, inexpensive, flat-packed satellite.

Because Starlink satellites fly very low to provide very low latency service, the satellites move across the sky very quickly and that means you need a lot of them to provide continuous coverage. Also, because one satellite can only serve a certain number of people for a given area, you want multiple satellites overhead of any location at any given time to be able to support many customers. SpaceX has already launched over 1,000 Starlink satellites and the constellation is just getting started with several thousands more planned for the first phase and even more than that planned for the second phase. If SpaceX is successful, they will have somewhere between 12,000 and 40,000 satellites in low earth orbit.

So, how do you build and launch thousands of satellites in short order? You mass produce them, at a low cost, and at a size and shape that makes it easy to mass launch them.

Traditional telecommunications satellites are gigantic in size, weight, and effort. A provider of traditional satellite internet could spend something like five or six years developing a single satellite at the cost of hundreds of millions of dollars. Because of their size, they rarely launch more than one at a time and launches can cost a hundred million dollars or more. If anything goes wrong with the launch or the orbiting satellite, it’s a catastrophic failure.

SpaceX treats satellites quite differently. They miniaturized and streamlined the design so they can fit dozens of Starlink satellites in the footprint of just one traditional telecommunications satellite. They’ve designed Starlink to be flat-packed to be densely stacked inside a rocket nosecone, 60 at a time. They’ve created a satellite assembly line that produces them for as little as a few hundred thousand dollars each, and as many as 120 a month. If one of them fails, even after launch, it’s no big deal because there are so many others and a failed satellite is easily and cheaply replaced.

Fast, cheap, and small, Starlink satellites are radically different than anything that’s come before and it’s those innovative characteristics that help make Starlink possible.

Starlink Innovation Part 2

The second key SpaceX innovation that makes Starlink possible is an affordable, reasonably sized phased array antenna. Let’s take a look at what that is and why it matters.

In order to make satellite internet competitive with terrestrial internet, SpaceX needs to fly their satellites at a very low orbit. Traditional internet satellites fly very high, at an altitude that allows the satellite to sit in the same spot in the sky relative to the ground. This is good for making the user’s antenna dish as simple a device as possible. Once you properly point the dish at the satellite, the dish just sits there and does its job. It’s bad, however, for a responsive internet because a satellite that sits in one place in the sky needs to be so far away that it takes ages (about half a second or more) to establish a connection between the satellite and the user’s antenna on the ground.

SpaceX flies its Starlink satellites in a very low orbit so the distance from the user’s antenna to the satellite isn’t so great and the connection latency is much improved (about 65 times better than traditional satellite internet.) But this comes with a challenge. At low altitudes, the satellites don’t sit in one place in the sky, they move across the sky, and rather quickly. That means your antenna needs to track the satellites as they move.

One way to do that would be to put some motors on the antenna so it could rotate to follow a satellite’s movement across the sky. But then you run into the problem of swinging the antenna back in the opposite direction to point at the next incoming satellite. You’d need to do that really fast to not have a gap in connectivity and that’s just not practical with motors. Perhaps you could have two antennas then, one tracking the satellite that’s leaving view and another tracking the satellite that’s coming into view. Now you’ve increased the cost and complexity of the system and doubled the number of failure points though — and made the user’s terminal large and cumbersome.

So, how does SpaceX solve this problem? With something called a phased array antenna. Phased array antennas are not new technology but they’ve traditionally been very large and very expensive. How they work is a bit complicated but a simplified description is something like this: you have many small antennas that act as one larger antenna. By powering those antennas individually and selectively you cause them to interfere with each other in such a way that the antenna’s collective beam is bent. This steerable beam can track movement and change direction and location almost instantaneously.

Big and expensive doesn’t sound like such a great solution though. And this is where SpaceX’s innovation comes in. Their hardware team miniaturized the technology, putting hundreds of small integrated circuit antennas onto a single computer board about the size of a typical internet satellite dish. And, they’ve managed to get the cost of building this phased array antenna down to something like $2500. Now, that’s still pretty expensive and so SpaceX is actually subsidizing most of that, charging users only $500 for the $2,500 antenna terminal. They hope future innovation plus mass production will get the cost down further but I suspect that it’ll be some time before they get costs down low enough to no longer need to subsidize. Instead, they’ll lose some money on the terminal and make it back up with the monthly internet service fee. If everyone that signs up for Starlink keeps the service for a couple of years, that will pay for the terminal and then start to be profitable for SpaceX.

If you’d like to read more about phased array antennas, and you should because they’re very cool and if you’ve read this far you’re probably into that kind of thing, start with the Wikipedia article at https://en.wikipedia.org/wiki/Phased_array It’s a good primer and has some nice animations that help a lot to describe phased arrays.

Final Starlink Mount Plans?

Thank you all for your advice and direction. I have or have on order nearly all of the parts to make this build happen.

At the top you see the Starlink user terminal which has a short mast, approximately 16 inches. That mast has a round spring clip for locking into the tripod base that came with the Starlink kit. I’ll remove that clip leaving a half inch hole through the lower part of the terminal’s mast.

The mast slides perfectly inside of a Channel Master J pole that I’ll drill a half inch hole through near the top. Then I’ll place a bolt and locknut to secure the terminal to the J pole. (That bolt and nut are the only parts I’m missing. Will probably have to brave the hardware store.)

The J pole connects to a mounting bracket that’s 1/8″ steel. The connection point is made by two bolts, one through a curved raceway that lets you adjust the angle of the pole.

Up the pole are a pair of Skywalker heavy duty 1/8th inch steel braces that stand off the tree about 8 inches and attach to the J pole with 1/4″ U clamps.

The J pole bracket will be secured to the tree with six 12″ XERATH quarter inch structural screws. Each of the two heavy duty braces will be attached to the tree with two 12″ XERATHs.

I want to make the job as easy as possible for the tree climber while also ensuring it’s secure and won’t wobble in the wind. What do you all think? Does it seem secure? Easy enough to assemble and attach while strapped to a tree 100 feet off the ground?

starlink mount

Starlink Innovation Part 1

The first key SpaceX innovation that makes Starlink possible is rocket re-use. Let’s take a look at why.

To make satellite internet responsive, the satellites need to fly much lower than traditional telecommunications/internet satellites which suffer from high latency. But if you fly in low earth orbit, rather than way up at geostationary orbit, your satellite moves across the sky rather quickly, and in a matter of minutes is on the other side of the planet totally out of view of your antenna. So one satellite, or even a few, isn’t enough. Flying in low earth orbit means you need hundreds, even thousands of satellites to ensure one is always overhead of every customer.

A significant chunk of the cost of satellites is the rocket launch to place the satellite in Earth orbit. Commercial rocket launches historically have cost anywhere from 100 million dollars to several hundred million dollars. The high cost of rocket launches is mostly due to their disposable nature. Traditional rockets are one-use beasts that, after their jobs are done, crash into the ocean never to be seen again.

SpaceX has created a partially re-usable rocket in the Falcon 9. Falcon 9 has two main parts or stages. The bottom, and much larger (and more expensive) part is the booster stage. The booster is a giant propellant tank and a bunch of rocket engines, nine in the case of Falcon 9. The booster is used to get the vehicle through most of the atmosphere where drag is a major force working against it. Once its job is done, the booster separates and falls back to Earth which lightens the load for the upper part or second stage to finish the job by achieving enough speed to reach orbit. Falcon 9’s second stage is much smaller and has only one engine. Once the second stage achieves orbit, it drops off the payload and falls back to Earth.

With the Falcon 9, the expensive first stage doesn’t burn up or crash into the ocean. Instead, it relights its engines and performs a propulsive landing and than can be re-used. The second stage, which is much less expensive does crash into the ocean.

To explain why saving the booster stage for re-use is so important to Starlink, let’s look at how SpaceX uses a rocket. Estimates are that it costs SpaceX about 30 million dollars to build a Falcon 9 rocket. 2/3ds of that cost is the booster and 1/3rd is the second stage. For a Falcon 9’s maiden voyage, SpaceX sells a launch to a commercial customer for say 60 million dollars making 30 million dollars in profit. That’s where a typical space launch provider would call it a day and start building its next rocket but not SpaceX. SpaceX lands that booster, refurbishes it, adds a new 10 million dollar second stage and flies it again for either another commercial customer, at a much higher profit margin, or uses it to launch its own Starlink satellites. And then they land the booster again, and can re-use it again, and again. The leading booster in SpaceX’s fleet has been launched 8 times.

So, SpaceX’s cost to launch a batch of Starlink satellites is probably about 1/6th the cost of its retail commercial launches, and 1/3rd the wholesale cost of a new rocket. By lowering this cost so much, SpaceX is able to launch an unprecedented number of satellites for far less than anyone else has been able to do before it. My rough math says that SpaceX was able to launch the first 1,000 Starlink satellites for about the same cost as a single satellite launch from a traditional satellite internet company.

When your plan is to launch 14,000 satellites, though, you need to find even more savings. And SpaceX is working on that. Their next rocket, called Starship, is fully re-usable. Both the first and the second stage return safely to Earth to be rapidly re-used. SpaceX wants rocket flights to be more like airline flights, where you fly, land, re-fuel, and fly again. By making the whole rocket re-usable, and by making it significantly larger and more powerful than the Falcon 9, SpaceX will be able to put the rest of the Starlink constellation up for an unheard of low cost.

Starship is in prototype stages, having made several low altitude flights but SpaceX hopes to achieve orbit with Starship very soon. Oh, and Starship is also the rocket that’s going to be first to put humans on Mars.

Starlink Architecture

Starlink is an interesting architecture. There are three main components. The first is the user terminal. It’s a sophisticated antenna. The second is the satellite, relatively small, mass-produced telecommunications satellites in low earth orbit. The third is the gateway. Gateways are ground stations with 8 antennas each which are connected to the terrestrial internet backbone.

So, the user terminal is the thing that looks like a flat-faced dish and connects to your local network, probably via a wi-fi router (SpaceX provides a router as part of the “kit”.) This “dish” is actually a phased array antenna which is capable of digital steering so it doesn’t have to do physical steering to track the satellites as they move across the sky.

The satellites are very cool. They are designed to be flat-packed so that 60 of them can stack inside one rocket nose cone. They’re rectangular in shape, a slab 9 feet on one side and 4.5 feet on the other with a 30 foot solar array that deploys to give the satellite an L shape. There are currently about 1,000 of them orbiting Earth of a planned 14,000. They fly at super-low orbits and move across the sky in just a few minutes. Their orbits are spread out to ensure there is always a satellite overhead.

The gateways are strategically located to provide overlapping areas of coverage. Each gateway is a collection of 8 antennas that connect the satellites to the ground-based internet at major fiber optic connection points. There are about 40 of these gateways already providing nearly full coverage to the U.S.

So, as a customer, my computer makes a request for something on the internet. It sends that request across my home wi-fi network to the Starlink user terminal which beams it up to a Starlink satellite that’s moving across the sky at 17,000 mph. The satellite beams my signal down to a Starlink gateway where it connects to and races across the fiber optic backbone, eventually finding its way to the requested resource. Then everything happens in reverse as that resource is delivered back to my computer.

But this is just how it works today, with the first generation of Starlink satellite. The second generation of satellite, some of which are already launched, have laser interlinks. Instead of simply relaying the signal from my user terminal directly to a gateway where it travels to its destination on the terrestrial internet backbone, the satellites will talk to each other, becoming a part of the internet backbone itself, in space. This will mean far fewer, but larger gateways will probably become the norm as Starlink coverage expands.

(Perhaps not practically useful, but nonetheless interesting to me, for some connections, especially those that are from one side of the world to the other, the Starlink latency could be lower than the terrestrial fiber optic network’s. That’s because light travels faster in space than in glass.)

Upgrading

We live in a 100 year old log cabin in a beautiful redwood forest about 15 miles from the heart of Silicon Valley. There’s a lot to love about it, the trees, the creeks, the quiet, and more.

One thing that’s not so great is the internet connectivity. Cable doesn’t make it out here. The trees are too tall for traditional satellite. We’re too far from the nearest teleco office for DSL. The closest cell coverage is about 3 miles away. And forget about fiber ever making it here.

So, for the last 11.5 years, we’ve relied on a small wireless ISP for our internet connectivity. Even that was a bit of a chore, requiring us to mount the radio and antenna near the top of a 200 foot tall redwood. We still weren’t able to get line of sight and the signal moves through the tree tops so our speed is limited to about 1.5 Mbps.

Before the pandemic, this slow speed was tolerable because if I needed a fast connection, I could go to the office. But now, working from home full-time, with lots of videoconferencing, the slow speeds are starting to be a real problem. I have to ask Deanna to get off the computer when I take a meeting and that’s usually several hours a day 🙁

This is why Starlink is so exciting. Going from 1.5 Mbps to 150 Mbps is going to be a game changer. We’ll be able to stream television in HD! We’ll be able to videoconference and surf the web at the same time. I won’t have to drive up the mountain to a cell signal to do software updates for our computers and phones.

If you see me posting a lot about Starlink over the coming weeks and months, that’s why.

Excitement

The Starlink antenna is still sitting on the ground so connectivity is very intermittent but when it is connected, I’m seeing some pretty encouraging speeds and latency.

Hopefully soon we’ll have it mounted up high enough to be usable.

I plan to maintain our old connection for a while and set up a dual WAN router with failover so that when the high-speed Starlink connection isn’t available, we’ll fall back to our slow connection.

In case you’re wondering why I’m posting this, it’s because Starlink is approximately 100 times faster than our current internet connection. That excites me!

speed test showing 160 Mbps

It’s Alive

Starlink is alive! I’ve temporarily set up the antenna on the ground to make sure everything works and this is the first sign of life. Can’t wait to get it mounted way up high where it has a full view of the sky. (For comparison, my connection for the last 11 years is about 1 Mb/s)

speed test results showing 91 Mbps