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boundary="_000_SY4PR01MB6979AF7082BE0F944BF491C7CE2DASY4PR01MB6979ausp_" Subject: Re: [Starlink] orbital maneuvers 12 per sat in the last 6 months X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 07 Jul 2023 22:28:39 -0000 --_000_SY4PR01MB6979AF7082BE0F944BF491C7CE2DASY4PR01MB6979ausp_ Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Now there is the misuse of the expression "exponentially" in cases when peo= ple just mean "a bit faster than before". If you have a time series 1, 2, 4= , 6, 8 then you could claim that it's exponential because the first three t= erms double each time, yet the last four terms could be used to claim that = it's linear. Plus, exponential growth doesn't necessarily mean fast growth. Your 2020 te= rm deposit for 5 years at 1% interest rate with interest reinvested sees yo= ur money growing exponentially, too. This is perhaps why decision-makers fr= om the economics sphere tend to get caught out be fast exponential growth (= the sort of growth us science and engineering folk tend to think of). Beyond that: I'm not sure that I can make much of orbital maneuver numbers.= Even GEO sats - for which collision probability is very low - undertake re= gular corrective maneuvers for station-keeping. For anything further down, = a maneuver could be a short-term evasive action, a longer term orbit inject= ion or change maneuver, or corrective action to any of these. Each maneuver uses some of the satellite's propellant reserve. As a general= rule, a maneuver executed over a longer period of time is more fuel effici= ent: A small change in a satellite's trajectory now can lead to a large cha= nge down the time axis, with very little propellant use - think Starlink sa= tellites transitioning from launch train to final station over months. Maki= ng small corrective adjustments to this over time might bring the total num= ber of maneuvers up, too. Conversely, large short-term corrections dip into= fuel reserves, which can impact on service life. So you'd really need to a= sk which sort of maneuvers these are, and how much each maneuver costs in t= erms of service life. -- **************************************************************** Dr. Ulrich Speidel Department of Computer Science Room 303S.594 Ph: (+64-9)-373-7599 ext. 85282 The University of Auckland u.speidel@auckland.ac.nz http://www.cs.auckland.ac.nz/~ulrich/ **************************************************************** ________________________________ From: Starlink on behalf of David = Lang via Starlink Sent: Friday, July 7, 2023 6:02 PM To: blakangel@gmail.com Cc: starlink@lists.bufferbloat.net ; Daniel= AJ Sokolov Subject: Re: [Starlink] orbital maneuvers 12 per sat in the last 6 months they have been filling shells (altitude sets), so it makes sense for the nu= mbers to have been going up. we'll have to see if they keep going up as much as they move on to differen= t altitude shells. David Lang On Thu, 6 Jul 2023, blakangel@gmail.com wrote: > I think the main point of the article is that the amount of maneuvers nee= ded > is currently increasing exponentially: "It's been doubling every six mont= hs, > and the problem with exponential trends is that they get to very large > numbers very quickly." I'm wondering if they are not taking into account = the > massive amount of satellites that have been launched since the previous s= ix > month report. > > I found the semi-annual reports filed w/ the fcc: > https://licensing.fcc.gov/myibfs/download.do?attachment_key=3D23204343 and > https://licensing.fcc.gov/myibfs/download.do?attachment_key=3D23204338 for g= en > 1 and gen 2 constellations. > > Still reading them and haven't found the older ones yet to compare. > > > David Lang via Starlink wrote on 7/6/2023 9:49 PM: > >> some people are assuming that more satellites launched will mean more >> maneuvers needed (not recognizing that what matters is only the things a= t >> the same altitude) >> >> plus, it's a scary large number :-) >> >> David Lang >> >> On Thu, 6 Jul 2023, Daniel AJ Sokolov via Starlink wrote: >> >>> On 7/6/23 17:54, Dave Taht via Starlink wrote: >>>> >>> https://www.space.com/starlink-satellite-conjunction-increase-threatens= -space-sustainability >>>> >>>> I am under the impression that each sat is capable of about 500 over >>>> the satellite's lifetime. I am curious as to what they are avoiding. >>> >>> Assuming your number of 500 is correct, I don't see any worry here. 12 >>> moves in 6 months makes 492 in 20.5 years. That is less than 500 and >>> beyond the lifetime expectation of the satellite anyway. >>> >>> A I missing something? >>> Daniel AJ >>> _______________________________________________ >>> Starlink mailing list >>> Starlink@lists.bufferbloat.net >>> https://lists.bufferbloat.net/listinfo/starlink >>> >> _______________________________________________ >> Starlink mailing list >> Starlink@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/starlink > > --_000_SY4PR01MB6979AF7082BE0F944BF491C7CE2DASY4PR01MB6979ausp_ Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable
Now there is the misuse of the expression "exponentially" in case= s when people just mean "a bit faster than before". If you have a= time series 1, 2, 4, 6, 8 then you could claim that it's exponential becau= se the first three terms double each time, yet the last four terms could be used to claim that it's linear.

Plus, exponential growth doesn't necessarily mean fast growth. Your 2020 te= rm deposit for 5 years at 1% interest rate with interest reinvested se= es your money growing exponentially, too. This is perhaps why decision-make= rs from the economics sphere tend to get caught out be fast exponential growth (the sort of growth us science a= nd engineering folk tend to think of).

Beyond that: I'm not sure that I can make much of orbital maneuver numbers.= Even GEO sats - for which collision probability is very low - undertake re= gular corrective maneuvers for station-keeping. For anything further down, = a maneuver could be a short-term evasive action, a longer term orbit injection or change maneuver, or corre= ctive action to any of these.

Each maneuver uses some of the satellite's propellant reserve. As a general= rule, a maneuver executed over a longer period of time is more fuel effici= ent: A small change in a satellite's trajectory now can lead to a large cha= nge down the time axis, with very little propellant use - think Starlink satellites transitioning from launc= h train to final station over months. Making small corrective adjustments t= o this over time might bring the total number of maneuvers up, too. Convers= ely, large short-term corrections dip into fuel reserves, which can impact on service life. So you'd really = need to ask which sort of maneuvers these are, and how much each maneuver c= osts in terms of service life. 

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

Department of Computer Science

Room 303S.594
Ph: (+64-9)-373-7599 ext. 85282

The University of Auckland
u.speidel@auckland.ac.nz
http://www.cs.auckland.ac.nz/~ulrich/
****************************************************************
From: Starlink <starlink= -bounces@lists.bufferbloat.net> on behalf of David Lang via Starlink <= ;starlink@lists.bufferbloat.net>
Sent: Friday, July 7, 2023 6:02 PM
To: blakangel@gmail.com <blakangel@gmail.com>
Cc: starlink@lists.bufferbloat.net <starlink@lists.bufferbloat.ne= t>; Daniel AJ Sokolov <daniel@falco.ca>
Subject: Re: [Starlink] orbital maneuvers 12 per sat in the last 6 m= onths
 
they have been filling shells (altitude sets), so it makes sense for t= he numbers
to have been going up.

we'll have to see if they keep going up as much as they move on to differen= t
altitude shells.

David Lang

On Thu, 6 Jul 2023, blakangel@gmail.com wrote:

> I think the main point of the article is that the amount of maneuvers = needed
> is currently increasing exponentially: "It's been doubling every = six months,
> and the problem with exponential trends is that they get to very large=
> numbers very quickly." I'm wondering if they are not taking into = account the
> massive amount of satellites that have been launched since the previou= s six
> month report.
>
> I found the semi-annual reports filed w/ the fcc:
> https://licensing.fcc.gov/myibfs/download.do?attachment_key=3D23204343 = and
> https://licensing.fcc.gov/myibfs/download.do?attachment_key=3D23204338 = for gen
> 1 and gen 2 constellations.
>
> Still reading them and haven't found the older ones yet to compare. >
>
> David Lang via Starlink wrote on 7/6/2023 9:49 PM:
>
>> some people are assuming that more satellites launched will mean m= ore
>> maneuvers needed (not recognizing that what matters is only the th= ings at
>> the same altitude)
>>
>> plus, it's a scary large number :-)
>>
>> David Lang
>>
>>  On Thu, 6 Jul 2023, Daniel AJ Sokolov via Starlink wrote: >>
>>> On 7/6/23 17:54, Dave Taht via Starlink wrote:
>>>>
>>> https://www.space.com/starlink-satellite-conjunction-increase-threatens-spa= ce-sustainability
>>>>
>>>> I am under the impression that each sat is capable of abou= t 500 over
>>>> the satellite's lifetime. I am curious as to what they are= avoiding.
>>>
>>> Assuming your number of 500 is correct, I don't see any worry = here. 12
>>> moves in 6 months makes 492 in 20.5 years. That is less than 5= 00 and
>>> beyond the lifetime expectation of the satellite anyway.
>>>
>>> A I missing something?
>>> Daniel AJ
>>> _______________________________________________
>>> Starlink mailing list
>>> Starlink@lists.bufferbloat.net
>>> https://lists.bufferbloat.net/listinfo/starlink
>>>
>> _______________________________________________
>> Starlink mailing list
>> Starlink@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/starlink
>
>
--_000_SY4PR01MB6979AF7082BE0F944BF491C7CE2DASY4PR01MB6979ausp_--