Submarine Related "Downdates"
We all know that "updates" are advisories containing more recent information.
Downdates and downdating are the opposite (rather than notorious rumors of social arrangements sought by a few ancient sailors in remote ports of call).
In researching Tracking The Gotland: The Attendant Mysteries some interesting, unclassified facts came to light from the 1997 era (HMS Gotland had been commissioned in 1996, you may remember). Here are some examples:
The fire control (system) power requirement for the HMS Gotland was 75 kW in 1997. The related power requirement for the 688I class subs was 550 kW. (GE engineers say the electric power requirement for my gas range is 1.8kw).
Bubblehead and I have blogged about the Navy facility at Pend Oreille in the past, but did you know there is another facility, more accessible to San Diego, at the Behm Canal. Hawkbill (SSN-666) was the first Sturgeon class sub to run the Behm acoustic range in Alaska.
Undermatched welding for HY 100 pressure hull applications had been approved. Future testing would still be necessary before HSLA 100 could be approved. (Disclaimer: I don't know what "undermatched" welding means, but I hope its not like dating chimpanzees).
The surface roughness of 1997 U.S. submarines was about 200 microns (compare that to your five o'clock shadows; good but not good enough).
Off-hull mine reconnaissance systems will either be tethered or nontethered, will be preprogrammed, and will have search rates of 30 square nautical miles per day with an endurance of several days by 2010. (I think some of this has been operational: UUVs in the Gulf).
Finally, there is United States Patent 4333169 (Apparatus for suppression of water flow noises in connection with a keel mounted sonar dome): A solution of water soluble polymer is ejected through a series of holes along the leading edge of the sonar dome under forward movement of the ship. The concentration and flow rate is chosen to "bathe" the dome in a very dilute dispersion (10 parts per million by weight) of the polymer. Full-scale testing has shown that polymer ejection not only reduces submarine self-noise, but it will also decrease hull drag and propulsor-generated radiated noise. Speed increases of 10 to 15 percent and reductions in self-noise exceeding 10 dBs (decibels) at certain frequencies for a given speed are possible. (polymer reservoirs [tanks] on DDXs?)
Want to read more? Here is Chapter 4: Submarine Platform Technology.
Submarines, always silent and strange.