Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Discussion of subs/INS
    From: Frank Reed
    Date: 2012 Apr 12, 15:38 -0700

    Alex, you wrote:
    "I also apologize for triggering this submarine discussion, but let me recall that it started from this important Cel Nav question: Who needed high precision Celestial Navigation, and was this really ever needed?"

    While the submarine navigation question is off-topic, it's only one step removed which I think is reasonable. And as you note, it does get back to a celestial question.

    You wrote:
    "By "high precision" I understand less than 1 nm accuracy. Ordinary practitioners do not care about this"

    Right. I have occasionally DEFINED traditional celestial navigation by including this level of acceptable error. And you're quite correct that submariners were one group who needed high accuracy celestial navigation, at least for a while. Both the submarines and the early missiles used stellar fix data to constrain errors in the inertial system. In fact, from what I understand, French ballistic missile submariners still use high accuracy celestial fix data.

    You wrote:
    "This is still a conjecture and there is no direct proof of this. However,
    there is much indirect evidence."

    There's plenty of information on these systems in the (unclassified) literature. Naturally there are other aspects which remain entirely classified, and those of use without security clearance can only speculate once we hit that wall. There's a book by Donald Mackenzie, written in 1993, "Inventing Accuracy: A Historical Sociology of Nuclear Missile Guidance" (portions available in preview on Google Books) which discusses both the technology and the implications in terms of the nuclear arms race. And those implications are not trivial. Submarine missiles were originally pure deterrence. They were "city busting" weapons reserved strictly for the deadly second strike of the doctrine of "mutually assured destruction:. In essence they were non-weapons. Submarine-launched ballistic missiles were doomsday devices, only be used in a nuclear armageddon. But from the earliest Polaris missile era in the US, there was a seemingly inevitable desire to apply technology to turn those missiles into something far more dangerous: counter-force or first strike weapons which could be used to destroy hardened military targets, like missile silos, in the Soviet Union. This logic was also driven by good old-fashioned inter-service rivalry. The US Navy was second tier in the nuclear triad with the Air Force controlling the ICBMs and the bombers. Eventually the submarine force got the accuracy they wanted. Supposedly, the Trident missiles, still deployed by the US in fourteen Ohio class submarines and by the UK in four Vanguard class submarines, have this high accuracy capability. Increased accuracy in SLBMs was highly de-stabilizing.

    You wrote:
    "It seems clear that INS alone, without checks is not capable of the required
    accuracy. The question is what checks were available before satellites,
    and also what checks are available without surfacing."

    Celestial through the periscope. There are some big problems with this process which may not have been discussed yet. Once you get down to 0.1 nautical mile accuracy, you have to worry about time accurate to better than one second (and that time has to be UT1 or equivalent, not UTC unless it's corrected by DUT). But the really huge problem is the Earth's gravity field. While it's an almost perfect oblate sphere when you're working at the level of accuracy of traditional celestial navigation, the gravitational field is quite "bumpy" at the higher level of accuracy required by submariners. The field had to be mapped in order to support high accuracy missile launches. This problem applies to both high-accuracy celestial navigation and "stable platform" inertial navigation, too, since both depend on the local vertical.

    -FER

    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site