Re: GPS Megadeath
From: Derek Lyons (derekl1963_at_nospamyahoo.com)
Date: 06/18/04
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Date: Fri, 18 Jun 2004 18:40:44 GMT
Steven James Forsberg <sjforsbe@bayou.uh.edu> wrote:
>: The problem with that is... We had no need of such a capability.
>: What an SSBN needs is a method of knowing it's position *without*
>: having to surface, or preferably even coming close to the surface. We
>: already had that capability with SINS, SINS/ESGM, and with ESGN.
>: From the point of view of an SSBN, GPS is 'nice-to-have', not 'must
>: have'.
>
> I'm not certain I quite agree with that.
You may do so. :) I'll refute as best I can without risking a
vacation in Kansas. (Do keep in mind I did this stuff for a living.)
>The USN definitely needed such a capability. For starters, SSBNs launch
>from relatively close to the surface, and in launching advertise themselves
>very well, and are not supposed to be anywhere near an enemy when they
>do. Thus, coming close to or at the surface is not such a liability.
SSBN's launch from considerably beneath periscope depth. Transiting
to PD and back to launch depth not only increases the length of the
launch process, but increases the 'something is up' signature. We
won't launch if we know we are being shadowed, but for obvious reasons
we always behave as if we are being shadowed and just don't know it.
Thus coming close to the surface does the two things the USN has
always avoided (and spent a great deal of money to avoid[1]);
increasing the length of the launch sequence and increasing the launch
signature. Thus coming to or close to the surface is a liability.
[1] For example, modifying the valves used to pressurize the launch
tubes in order to reduce the noise they generated. The pressurization
and flow control valves in the hovering system were also modified for
greater quietness because setting up that system as we made other
launch preps was a noisy and very obvious signature.
Across the history of the SSBN force reducing the indiscretion rate
and reducing the length and signature of the launch process have been
right behind accuracy (and not far behind at that) in the goals and
requirements of the system. Thus LORAN capability was added to the
bouy and wire (discussed below) and the BQS-3 secure fathometer
developed to avoid surface exposure. We did/do have mast mounted
antenna for Transit/GPS, but these are used as little as possible to
avoid going near the surface.
>This is particularly true if you are going to be using satcomms for any
>purpose - verification, mission update, etc.
We don't, not really. Satcomm is a backup for two other systems, one
which allows us to patrol deep (the bouy) and another which allows us
to patrol near (but not breaking as satcomm requires) the surface (the
wire). Also, SSIXS is a store-and-forward system (which requires
interrogation by the SSBN) rather than the continuous comms provided
by the systems the surface fleet and the rest of the DoD uses.
> Secondly, the USN wanted to be able to use SSBN launched missiles
>in counterfire, not a a countervalue, role. You can nuke a city without too
>much accuracy, but if you want to plink hardened silos and buried targets
>accuracy becomes much more important.
Certainly accuracy is important, but SSBN/SLBM system design also has
to consider issues (outlined above) that an ICBM system does not.
That was a prime driver behind the development of the ESGM/ESGN. Not
only was it more accurate than SINS, but it also required fewer and
less frequent (possibly detectable) external updates to maintain
overall system accuracy.
D.
-- Touch-twice life. Eat. Drink. Laugh.
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