I'm a firm believer that, sometimes, chemicals are the right answer.
216 karma · joined December 13, 2019
This is pretty optimistic because the shells at different altitudes have overlapping beams and can not all use the same spectrum at the same time (OK, technically, two satellites can share the same spectrum if they use different polarizations, but, anyway, SL plans to have 3 orbital shells according to WP.) LEO bandwidth scales sublinearly with the number of satellites because of this. Also, this doesn't take into account inefficiency due to timing and coordination between satellites, nor the fact that 70% of the total bandwidth is over water and even the bandwidth over land is mostly not over population centers. The actual cost per bit is estimated to be about 2.5x-10x higher (see https://twitter.com/Megaconstellati/status/13103869669917040...).
> Starship will carry 240 satellites at a $2 million launch cost.
I think the operative word here is "will". In 2019, SX charged around $2700/kg to launch (not sure to what altitude, but let's take that figure, if you will.) A SL satellite is around 260 kg. If I round the numbers down to $2500/kg and 250 kg/satellite, I get $37.5 MM to launch 60 at a time. Suppose Starship can overcome the laws of physics and aerodynamics and launch 240 satellites with the same amount of fuel, so the cost drops by 75%. That's still roundabout $9.3 MM/launch, or, around $1 B in launch costs every five years.
Nevertheless, as you pointed out, that's not much compared to the cost of the satellites themselves. My understanding is that $250k/satellite would be very good, even at scale, but let's take that number. That brings the cost of making and launching the constellation to around $8.5 B / 5 years.
But, that's just the satellites. You need an entire ground segment to make the whole thing work. As a rough estimate, say that's another $8.5 B, but it'll last twice as long, so, $4.25 B / 5 years. OK, now we're at around $2.5 B / year just for the machinery, not including the CPE, landing rights, or personnel to keep things humming.
> If you do the math, a fully operational Starlink will print vast sums of money...
I think that's the big question everyone wants the answer to: Who will pay for this? SL will cost around $2.5 B / year in just the ground segment and the space segment. At $100/month, SL needs a bit over 2 MM customers just to cover the cost of equipment. But those 2 MM customers are not spread out evenly around the Earth, where all of the bandwidth is.
If you have any insight as to who will pay for this, I'd genuinely like to know because I'd be happy to buy into the SL IPO and retire early.
Not that it matters, but, I could.
> How many Mbps is that? Not a lot.
So, e.g., Viasat offers 100 Mbps service.
> the aggregate throughput capacity of a single CMTS port on a DOCSIS3 or DOCSIS3.1...
Yes, you can get tons of traffic through a coax cable. There's more bandwidth and you can use higher efficiency modulations because the SINR is way better. Not sure how this is relevant, though.
I'll point out, though, that plenty of people see slowdowns on their cable modem networks during peak busy times. Even these networks have their limits.
> ... it becomes a very poor end user experience.
Again, I think some people would disagree with you on that.
> ... real world throughput needed to be a viable option for rural broadband. Because the link budgets are much better with small antennas and small tx poweer electronics, due to the LEO orbit. And the much lower latency.
No doubt about the lower power electronics (vis-a-vis GEO) and the lower latency, but even so, SL's CPE is around $1,000, and the reliability through rain, wind, and snow is unknown. Setting aside the reliability question for now, I think what it really comes down to is the price vs latency trade-off. In order to be profitable, SL will have to be more expensive than traditional GEO solutions because the CPE, the ground network, and the actual constellation all cost more on a $/bit basis than GEO solutions. It will be interesting to see if the lower latency will be enough to draw consumers.
The big X-Factor in all of this is how much more capital Elon can raise. He has an amazing talent for raising money and if retail investors don't care that SL is less cost-effective than other options, then it can go on for a long time.
Not sure how that's relevant. In any case, the total cost of a GEO is closer to double that.
> saying that the throughput of all of the ka-band spot beams on a satellite is 1Tbps is both double-counting math for the capacity in both directions, and does not reflect the actual capability of the satellite.
This is not correct.
> maybe if every single ground station was something large enough and with enough link budget to operate at 16APSK and better modulations. not a realistic figure if you're talking about low-cost, sub $1500 hardware, consumer grade ku and ka band vsats.
I'm not sure if you're talking about the ground stations that connect to fiber backhaul, here, or to the CPE terminals. In any case, ground station capacity is not an issue, and neither is CPE terminal capacity.
> for a randomly chosen rural zip code in WA state, hughesnet is offering a 50GB quota/month for $150/month. so yes, 60GB transfer limits and things are still a real thing. and during peak evening hours TDMA contention means that latency will be 1150ms+, or worse.
Yup, that's what I said: "... unless you're still using HughesNet."
> the unavoidable economics of consumer grade small VSAT require serious oversubscription. Dedicated 1:1 satellite capacity starts from $1500/Mbps and up, and requires a serious VSAT terminal, not a hughesnet/viasat/wildblue type toy.
Again, not sure how this is relevant. Every residential (and even many business) connectivity option is oversubscribed.
If you're saying that satellite cannot compete with fiber or cable, then you'd get no argument from me. If you're saying that satellite is a shitty option, well, I think you'd find that some people disagree with you on that.
That's not to say there isn't room for improvement, but providers know this and are working on it.
But, what is that value? Of the ~ 800 SL satellites launched so far, about 5% have already deorbited. Of the remainder, all but 2 don't have inter-satellite links. The others will deorbit in 5 years. LEOs, in general, require tremendous amounts of money just to maintain an existing constellation size. At steady state, SpaceX would have to launch something like 60 satellites per week just to maintain their constellation. I can't remember the numbers now, but I think that meant costs in the $10's of millions / week just in maintenance once you account for construction and launch costs.
Actually, GEO satellites have quite a bit of aggregate capacity (1 Tbps and going up) and more capacity where it matters (over land, and specifically, population centers) than LEO constellations, and therefore have better bandwidth economics. They also last ~3x as long, which brings the $/Mbps down more.
60 GB/month caps are not really a thing anymore, unless you're still using HughesNet.
Latency will be dealt with using hybrid modems that can use LEO/DSL/4G for latency-sensitive applications and GEO for large amounts of cheap bits. Hughes, to their credit, has had such a solution available since 2007, last I checked.
Is it possible that a 5-10% change is actually "massive"?