portillo

This is exactly right!

I think that 5M is a high number (at least with the current number of satellites and their architecture), specially if they do not apply data caps.

I would say that 1M customers in the US is a more reasonable figure. If they hit these number, I expect the performance to degrade significantly.

A satellite dish does not transmit any information to the satellite. Satellite TV is a pure broadcast system in the forward direction.

Moreover, comparing a parabolic receiver with a phased array is quite unfair. The amount and complexity of the electronics and processing power required is several orders of magnitude different.

You can get 24/7 connectivity to LEO right now (and 25 years ago too) using TDRSS.

The system costs a fraction of what Starlink will cost, as you only need 3 GEO satellites.

The current satellites do not have crosslinks, and in any case, in their FCC filings SpaceX talks about optical crosslinks, not RF.

I agree, this was the real reason why the project failed. Moreover, it was not clear at all that fractionation would bring any lifecycle costs savings, neither that any of the alleged extra flexibility (and maneuverability, resiliency, maintenability, and other -ilities) would result in any added value for the missions.

Fractionation is very hard,it introduces a lot of complexity in the design and interfaces, and it requires lots of coordination between multiple vendors. Project Ara by Google (a modular cellphone similar to Phoneblocks) also vouched for this idea of fractionation (and in fact was also led by Paul Ermenko) and was also cancelled.

Sure, operated manually by a bunch of people with PhDs.

I think so too. In addition, they seem to have regenerative payloads on-board (otherwise I don't get how they get ~20Gbps/sat with a single Ka-band antenna), so they need to do full decoding + encoding on the satellite. Not sure how fast that can be done, but it will add some latency ms probably.

Hi Mark,

Thanks for your reply. I agree with you, using user-terminals is extremely challenging, especially from a link-budget perspective. You cannot pump enough data to make it worth it. For the gateways, my main concern is that the Ka-band spectrum would have to be shared between user-data and "inter-satellite" data.

Finally, I think that the use-case your described for those latency-sensitive customers is going to be hard to pull off, mainly because of link-availability concerns. There are too many "passes" through the atmosphere to guarantee the availability numbers that a user of such a service requires (99.5%?). Rain in any of these links might cause an outage or a re-route (causing too high jitter). Plus, it would be extremely difficult to have signals traveling from one continent to another.

These analyses are quite optimistic as they only consider propagation delay.

Moreover, the idea of using user-terminals/gateways as ground-relays to bounce signals up-and-down is quite impractical, since you would be greatly reducing the capacity available to satellites on those "intermediate" satellite.

That is not the round trip time, it's the one-way delay. Also, processing time can be significant in satellite networks. Finally, given the current architecture of SpaceX without crosslinks, the total RTT will be ~30 ms + processing time + whatever is the RTT of the backbone network they deliver the traffic to.

It will not work. Their use case is low data rate applications. It's one of those case where you pick 2 among high number of users, high bandwidth, and low gain user terminals.

> to a self-described expert, who unfortunately didn't provide a ton of context),

Are you questioning the expertise of Tim Farrar? If that is the case, you couldn't be more wrong. Check his blog and you will see he has been doing this thing for more than 20 years...

Also, lynk will never be able to provide enough bandwidth to deliver internet connectivity. It is envisioned to be used for short messages.