Apparently the atmosphere is 100 times denser between 550 km and 350 km (roughly 3.5e-13 vs 3.5e-11 kg/m3). It's still hard vacuum either way, but I wonder how that additional density would affect the current 5 year lifespan number. Perhaps full-size V2 satellites have so much propellant onboard that they can keep the 5 year lifespan even at the lower altitude.
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Orbital velocity, period:
350km altitude: 28916 km/h, 80.5 minutes
550km altitude: 28459 km/h, 84.5 minutes
Dwell time and orbital angle for 25 degrees above horizon on plane:
350km: 2.58 minutes, 11.56 degrees
550km: 3.97 minutes, 16.90 degrees
Satellites in one plane (also roughly number of planes) for continuous coverage:
350km: 32
550km: 22
Ground spot is 40% the size at 350km vs 550km for the same beam width allowing higher bandwidth per unit area if it was power/channel limited.
I wonder how cool the locals will think it is if each landing can be heard from shore.
Ping is to final endpoint and back so 4 hops or 2.7 ms if satellite is directly overhead. Offset range impact is greater since radial path is the closest distance between two altitudes.
Yeah, videos certainly indicate it's audible from land... I wonder how loud that is and for what distance. I also wonder if there's any room to tweak when they break the sound barrier, although that's probably payload dependent...
Yeah, I should have been clearer to say trip to the bird and back.
If the lower orbit has no significant downsides, than why not? A couple of ms when they are targeting <30ms latency helps...
Yeah, more birds and propellant needed (which turns into more launches), everything else improves. Good thing they use Argon. Refueling would be awesome.
I figured you were talking bird impact, but RTT is the full network path. So unless less talking to the bird itself, four hops. Had to double check what ping was defined as.
Yeah, thanks... I let some Network Admin lingo slip in
I should know better, worked on systems that leveraged geosync sat IP connectivity (latency measurements in large fractions of a second...) 25 yrs ago...
I was just in the Bahamas and got up in the middle of the night to see a launch. No question I would have done anything possible to see a booster landing. Unhappily, I didn't see anything. I'm guessing I was looking the wrong direction and the booster was launching in a different direction than I thought it would. The sky was perfectly clear. So it was definitely on me.
437 miles. I thought the launch trajectory was going to go right over my head, or close enough. I must have been wrong.
Or...I am a sucker because it's all been faked! And I fell for it!
Thanks for all that wonderful data. Confirms by hypothesis that you need more satellites and your numbers tell me that it is 50% increase !!
Signal strength is ultimately a function of regulation, not geometry. SX is maxing out PFD/signal strength already, at least in high density (and thus high revenue) areas, so there’s no dee-bee gains to be had by changing altitude.
From a system perspective the concept of 350km sats is largely downside, with one very notable exception: Beam area. Because of regulated power levels, the capacity of any one beam (and thus, basically the aggregate max capacity of the system) is all but exclusively a function of how wide it is--wide as in the angle of the beam cone, NOT its projected area on the ground. If each satellite's beam is pumping 300mbps, it doesn't matter if that beam comes from a sat at 350km or 500km or 5000km (like mPower)--all the users in that beam share that 300mbps regardless how big the area on the ground. (This is the major reason GEO internet is terrible--the beam footprints are huge and the operators way oversubscribe each beam). So, If that footprint is less than half the size at 350km vs 500km, that essentially means that each satellite is putting over twice the number of beams down in a given area on the ground and thus twice the capacity, and thus (most important) can serve over twice the density of users at the same level of service. That's a serious increase in revenue.
We're still many years away from starship deploying a useful number of V2's (whose much larger antennas result in much narrower beams--which is basically the "other way" to reduce the area served by each beam), so there's really no near term fruit on that revenue tree. V2 minis are an interim step--more of a revenue bush--where their larger-than-V1 arrays (and thus narrower-than-V1 beams) can serve higher density than V1s and thus generate more revenue....but as is clear from the land-rockets-in-the-Bahamas concept, getting V2Ms on orbit needs to go faster. Unfortunately there's really no other levers SX can pull to increase user density (and corollary revenue) than lowering sats so...here we are.
From a bottom line perspective increased user density is key to the aspirational success of Starlink; that increased density will enable Starlink to make inroads into properly competing with fixed terrestrial service vs their current service that's really just competing with [the relatively small global market of] other satellite based services.
437 miles. I thought the launch trajectory was going to go right over my head, or close enough. I must have been wrong.
Or...I am a sucker because it's all been faked! And I fell for it!
Well there WAS that flat earth model in the recent lauch video:
Hmmm....
Sort of... the 53 and 53.2 shells were speced out at 22 satellites per plane (whoa, I must have done the math right!). However, there are 72 planes. So each is only 5 degress offset (at the equator). That means if they stagger adjacent planes by 8 degrees they can maintain coverage. Also works at other modalities.
The polar orbits are only 6 planes, but 40+ satellites.
https://www.nasaspaceflight.com/2022/10/spacex-3500-starlink/
That makes it sound like beams are shared by ground stations. Why would the satellite bother doing that when it can use a phased array to instantaneously shape a beam specific to each ground station that it wants to reach? If the satellite is sending the number 4 to ground station A, then it sends the 4 to ground station A with its own beam. Then it has a 6 to send to B, so it sends that directly at B. Why create a 'static' beam that covers both A and B and send 4 to A and 6 to B?
It seems like you only gain in bandwidth if you increase the number of satellites because each one represents an available data cable that a ground station can connect to. The ground stations in view of a satellite must share the wire while the satellite is in view.
What am I getting wrong here?
Ground cells are more or less fixed locations and serve all terminals within them and are 10s of km wide.
Closer sats means smaller cells means more theoretically bandwidth (given more satellites).
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