[Starlink] Starlink power use & satellite tracking

[Ulrich Speidel]

In the aftermath of our cyclone here, I got dragged out for a bit of 
media comment and, downstream, a few questions came up on dishy power 
use. Here's what I know and can glean - comments welcome:

  * Starlink's own specs say 50-75 W "Average Power Usage":
    https://www.starlink.com/specifications. But that's average, not
    peak, and peak is what matters when people start recommending that
    Starlink could be run out of a small inverter and a car battery in a
    disaster.
  * Small inverters usually come with cigarette lighter cables, and
    cigarette lighter sockets are typically fused with 8 or 10 A fuses.
    That puts maximum safe power outputs in the 96W to 130-something W
    range depending on battery voltage.
  * Our lab's "RV" subscription rectangular dishy & router regularly
    clocks in at around 80-100 W, and I've seen it go as high as 108 W
    on one occasion. I've also seen it go as low as 30 W for the first
    time last night.
  * I have a user report from an older round dishy owner having seen up
    to 200 W on occasion.
  * Assuming conservatively 90% inverter efficiency, that could mean up
    to ~120W and maybe more for the rectangular version and over 220 W
    for the circular one.
  * If dishy goes over cigarette lighter fuse capacity, people may lose
    their ability to charge phones from their car - also a critical
    capability in a disaster.
      o Not everyone takes kindly to the suggestion that advising
        inverter + car battery use could potentially be counterproductive.
  * So, what's the peak power use you have seen on your version of dishy?
  * It appears that the current mode of operation here is that dishy
    uses several satellites in parallel if these can all see a gateway
    and have capacity to carry traffic.
      o So for us in urban Auckland with few Starlink users in the cell
        and three gateways in the vicinity, our dishy is spoiled for
        choice and usually gets to use maybe three or more satellites at
        once. That takes a corresponding amount of power but also means
        great data rates a lot of the time.
      o For a rural user with more Starlink users in the cell and
        further away from gateways, the satellites that the cell can see
        and that  can also see a gateway may be fewer in number. This
        means dishy only gets to talk to maybe one or two birds at a
        time and so uses a lot less power, and you get more average data
        rates there.
  * If this is so, then it begs a question:
      o If Starlink could cap the number of satellites dishy can use in
        an emergency area, they would be able to keep your fuse intact.
        Should they aim for that, even if it means that you might see
        lower data rates in a situation when many people depend on one unit?

Starlink is currently being touted as THE comms solution for emergencies 
as large swathes of NZ's northern and eastern North Island remain 
without terrestrial or mobile Internet coverage after cyclone Gabrielle. 
This is the outage map of one of the larger mobile phone providers just 
for these areas:

Most of these are due to power outages to sites, but there are quite a 
few backhaul cable issues as well.

One of the biggest problems is that electronic payment systems don't 
work without Internet. In our largely cashless society, this is leading 
to situations where emergency services can't refuel their vehicles 
because their fuel cards won't work, supermarkets and other stores can't 
sell anything because customers have no means of paying, and the air 
force is flying in hard cash in order to help the locals buy food.

-- 
****************************************************************
Dr. Ulrich Speidel

School of Computer Science

Room 303S.594 (City Campus)

The University of Auckland
u.speidel at auckland.ac.nz  
http://www.cs.auckland.ac.nz/~ulrich/
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