Sunday, July 11, 2021

A simulation of the SpaceX, Amazon, Telesat and OneWeb broadband satellite constellations

Over two years ago, an MIT research group ran a simulation of the low-Earth orbit broadband constellations of OneWeb, SpaceX, and Telesat, and last January they repeated the simulation updating with revised constellation characteristics and adding Amazon's Project Kuiper.

They ran the new simulation twice, once using the planned initial deployments of each constellation and a second time using the configuration shown below, which shows final deployments assuming that change requests that were pending in January would be approved. (SpaceX's have been approved). I will discuss the second simulation here and you can consult the paper for the results of the initial deployment simulation.

The following figure shows the total system throughput for each constellation as a function of the number of ground stations and whether or not the satellites have optical inter-satellite links (OISLs) enabling them to route traffic through the in-orbit grid. (The lines show averages and the shaded regions show interquartile values).

Note that Telesat is committed to having OISLs in all their satellites and SpaceX will have them in their polar-orbit version 1.5 satellites that are launching this year and in all version 2 satellites starting next year. OneWeb initially planned to include OISLs but decided not to for now and Amazon has not committed to them but has formed an OISL hardware team.

The following figure shows the number of satellites in line of sight (LoS) at full deployment and population as a function of latitude. All Amazon satellites are in inclined orbits, so, while major population centers are served, polar regions are not and the altitudes of the OneWeb and Telesat constellations increase the numbers of satellites in LoS.

If interested, you should read this and the earlier paper (links in the opening paragraph) for details on the methodology, assumptions, and results, but I will conclude with a couple of caveats.

This simulation ignores the 7,518 very low-Earth orbit satellites that have been approved for SpaceX and the designs of all of the constellations are in flux. SpaceX will soon be launching version 1.5 satellites followed by version 2 next year. Similarly, OneWeb will be launching improved satellites by the time the constellation is complete and Telesat and Amazon are still in the design phase.

The simulation assumes that demand is proportional to population (based on a 0.1-degree resolution grid), so mobile utilization by ships, planes, and vehicles is not considered. It also assumes each individual consumes an average of 300 Kbps and the total addressable market is 10% of the global population. As they admit, the 10% is optimistic. (Elon Musk expects 3-5%). Since SpaceX will be charging the same price in every nation, their per-capita subscription rates will vary with national income, and the companies' target markets vary. For example, Telesat will not market to consumers

While the specifics will change and this and other simulations will have to be rerun over time, this simulation considers key variables, and general conclusions can be drawn. For example, in this simulation, maximum throughput is from 13-42% higher when 20 Gbps OISLs are assumed. Currently, only SpaceX and Telesat are committed to OISLs, but since OISL technology is improving and they also improve latency, save on ground station cost and enable coverage at sea and other isolated locations, I expect all operators to eventually adopt them. (We may also see OISLs between layers, for example, between Telesat's LEO and GEO constellations).

Thursday, July 01, 2021

Elon Musk interview: SpaceX, Starlink and his motivation and philosophy

Elon Musk packed a lot about SpaceX and Starlink into a 32-minute interview at the 2021 Mobile World Congress and ended with a discussion of his motivation and the roles of his three companies -- SpaceX, Starlink, and Neuralnk. Let's start with the SpaceX and Starlink update and conclude with the philosophy and motivation. (Scroll to the end of the post for the video of the interview).

  • Starlink will fill in the gaps between fiber and 5G offering viable service to the most difficult to reach 3-5% percent of the population that are in sparsely-populated regions.
  • They currently have over 1,500 operating satellites with 5 MW combined power and a capacity of about 30 Tb/s.
  • They may have over 500,000 users in 12 months.
  • They expect to achieve sub-20 ms latency.
  • They are currently authorized to provide service in about 12 nations and will be able to offer global service (excluding polar regions) in five weeks.
  • Their software-defined phased-array antennas for satellites and ground stations are the  most sophisticated and advanced technology available, offering microsecond switching with no discernable jitter.
  • They have advanced rapidly reusable (booster and fairing) launch capability.
  • Last year they delivered about 2/3 of all payload mass to orbit and this year they expect to deliver closer to 80 percent. China will deliver about 12 percent and everyone else the remainder.
  • They are learning how to make satellites, terminals, and gateways -- improving the "machine that makes the machines."
  • They will soon be launching version 1.5 satellites with inter-satellite laser links (ISLLs) to serve high latitude regions.
  • Next year's version 2 satellites will have significantly more capability and ISLLs.
  • They plan more gateways at major service centers.
  • They are nearly ready to announce data backhaul agreements with two major-nation mobile companies.
  • They have an attractive proposition in countries in which telephone companies are required to subsidize rural connectivity.
  • They will have invested $5-10 billion by the time they have a positive cash flow and will have to continue investing -- maybe $20-30 billion over time -- to remain competitive with constantly improving cellular and cheaper geosynchronous satellite Internet service.
  • Their goal is rapidly reusable reliable rockets. With a Falcon 9 launch, 60% of the cost is the booster, 20% the upper stage, 10% the fairing, and the launch and recovery process is about 10%, and they are doing well at booster and fairing recovery.
  • The retail price of Starlink service will be the same everywhere, which surprised me.
  • Terminal cost is now over $1,000 and they hope to get that down to $250-300.
  • Starship is designed for full and rapid reusability and will be able to launch 100 and with refinement 150 tons to orbit with no refurbishment between flights -- like an airplane.
  • Starship uses low-cost methane-oxygen fuel so the propellant cost per launch will be about the same as with the Falcon 9.
  • The marginal cost per launch will be around $2 million, which is less than the original Falcon one rocket.
  • With orbital refueling, Starship will be able to deliver 100, possibly 200, tons to The Moon or Mars.
  • Musk repeated his oft-quoted statement that his goal for Starlink is not to go bankrupt and his oversimplified claim that setting up a Starlink terminal is as simple as plugging it in and pointing it at the sky. He also restated his recent sophomoric tweet about having 69.420 customers.

Underlying philosophy

At the end of the interview, the moderator said Musk seemed to take on new challenges rather than opportunities and asked what criteria he used when deciding to take on a new challenge.

Musk began his answer by stating the purpose of three of his companies

  • SpaceX: to extend the scope and scale of consciousness beyond Earth.
  • Tesla: To ensure that life is good on Earth with sustainable energy.
  • Neuralink: To achieve long-term AI-human symbiosis.
All contribute to the end of expanding the scope and scale of consciousness:
"Generallly these companies are oriented toward, like, what actions can I think of to do to maximize the probability that the future is good and that that future jncludes the expansion of the scope and scale of consciouslnes. This is based on my fundamental philospy of, you know, we dont really know what all the answers are or even what questions to ask but if we are able to expand the scope and scale of conciousness then we are better able to know what questions to ask about the answer that is the universe."
I wish the interviewer had followed up by asking him to speculate on the possible side-effects of expanding the scope and scale of human-machine consciousness in pursuit of understanding the universe.

Here is the video of the interview: