r_anderson@flyppr.enet.dec.com (09/24/90)
From: r_anderson@flyppr.enet.dec.com
I have started reading some books concerning WWII submarine
operations and tactics. These books were written by submarine
Commanders and Execs, so they are fairly detailed and extremely
technical. Unfortunately, they are written for people versed
in navigation technics and terminology.
Never having been in the Navy (or a ship for that matter), I
have some basic terminology questions that would help clarify
the tactics being described (why don't these books come with
manuals? :-)).
1. When a target's bearing is "marked" through the periscope,
is the angle relative to submarine (0 degrees being the bow, 180
degrees being the stern), or relative to the "true" geographic
course?
2. Can someone clearly explain the term "angle on the bow" and
how this information is useful in determining a torpedo attack?
3. Can someone clearly explain what an "Is-Was" is and how it
works?
4. Can someone clearly explain what a "TDC" is and how it works?
Thanks in advance!
Rick
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**********************************************************kulkisar@mentor.cc.purdue.edu (Aaron Kulkis) (09/27/90)
From: kulkisar@mentor.cc.purdue.edu (Aaron Kulkis) Reading suggestion at the end of this post you might regret having started me on this subject though...one of my favorites... In article <1990Sep24.002015.24721@cbnews.att.com> r_anderson@flyppr.enet.dec.com writes: > > >From: r_anderson@flyppr.enet.dec.com > >I have started reading some books concerning WWII submarine >operations and tactics. These books were written by submarine >Commanders and Execs, so they are fairly detailed and extremely >technical. Unfortunately, they are written for people versed >in navigation technics and terminology. > >Never having been in the Navy (or a ship for that matter), I >have some basic terminology questions that would help clarify >the tactics being described (why don't these books come with >manuals? :-)). This is the subject that first got me into reading military history, so, although I've never been on a sub of that or any other vintage, I have managed to decipher the lingo... If you do not understand trigonometry, learn a bit..navigation for a small area where you can assume a 'flat' planar navigation surface is almost trival...and since that's all we're worried about to sink our quarry once we've made contact, that's all you need to understand. In following, all male pronouns refer to enamy ship, all female pronouns refer to friendly ship (i.e. sub we're on), as was the usual standard of that era. > >1. When a target's bearing is "marked" through the periscope, >is the angle relative to submarine (0 degrees being the bow, 180 >degrees being the stern), or relative to the "true" geographic >course? His bearing marked is relative to submarine's course, as you stated above. > >2. Can someone clearly explain the term "angle on the bow" and >how this information is useful in determining a torpedo attack? > Angle on the bow is basically the bearing that the ship would mark if it were to "mark" bearing on the sub, or my bearing relative to him...still confused???? If a ship's Angle on the Bow is less than 90 degrees, it is comming more or less towards me, 90 - 270 more or less away, 270+ degrees, towards me. Angle on the Bow Description 0 he is headed right at me. 180 he is headed right away from me. 90 or 270 I am on his broadside range + Angle on the Bow ==> predicted path of travel relative to sub's current position. Most of the WW2 'dazzle' camoflauge patterns had nothing to do with hiding the ship but instead were to make it more difficult for the sub captain to figure out his speed, range and Angle on the bow. >3. Can someone clearly explain what an "Is-Was" is and how it >works? the Is-Was is a slide-rule device, commonly called the 'banjo' for it's distinctive shape. the technique was to arrange the device to reflect 2 sets of "Marks". I am not sure if this was used in conjunction with the running plot of the contact directly (as in used in physical contact with the charts of the current area) or used as a stand-alone calculator. Most subs relied very heavily on the banjo man, because due to the plodding speed of a submerged WW2 sub, you needed to know where the heck your contact was going as fast as possible, lest you wind up in left field with dead batteries. > >4. Can someone clearly explain what a "TDC" is and how it works? > It has been several years since I have read any 'I was there' accounts, but here is what my memory serves me. Do not take anything as ABSOLUTE because there were probably sever models of this thing all going under the same name, having different operational specs, but here is what there were like, basically: The TDC (Torpedo Data Computer) was an electro-mechanical computer which made American subs truly incredible machines after they were installed....as best I can determine, it was operated somewhat in this fashion: Whenever the captain or exec would 'mark' a set of target data, the TDC operator would dial in the data as told to him. As each set of marked data was dialed in, a more and more refined set of readings were available. The TDC would use/could tell you: 1) current Bearing of target. 2) Current Range 3) Current Angle on the Bow 4) Target speed 5) sub's bearing 6) sub's speed 7) Torpedo's speed 8) how many yards to "the track" (path of the target ship) 9) length of run of the torpedos if fired at this moment to hit target as defined above (in yards, or seconds, I forget) There may have been variances among different models, I do not know. Additionally, US torpedos had an option so that torpedos did not have to run along the same bearing that sub was sailing... It's been many years since I've read a submarine account, but I know that they could be steered several degrees off of the sub's current line of travel (45 - 90 degrees max, I believe). In pre-TDC days, these were set by hand. The TDC would constantly adjust for an optimal shot. Additionally at least some models could be manipulated relatively easily to fire several torpedos over a 5 - 10 degree spread (in case marked data was erroneous) in hopes that 2 out of 3 would hit or some such. At least some TDC's (all?) could handle multiple targets from what I gather. Later version may have been connected to the ship's navigation gear (don't bet $$$ on it though!!!) to make for even more efficient updating of data British subs had a device that could allow a torpedo to be shot 90 degrees off present course (to either broadside) called the Ninety Bender...idea was to sail parallel and ahead of your intended victim. since, as I have stated, it has been about 10 years since I've last read anything seriously on the subject, there may be minor mistakes, but you should get the idea from this post. Reading suggestions: 1 _Submarine!_ by Capt. Edward L. Beach, (US Navy, Ret.) several (like 20) US submarine war patrols in pacific are documented. Chapters alternate between Beach's experiences, and famous/notable patrols by other boats. So good that it is the only book in my entire life that I have ever checked out on 3 seperate occasions, each from a different library. Also has a wonderful poem, kind of a fighting verse for the USS Trigger, Beach's first command. Covers the whole US submarine war from opening days of faulty torpedos to the final days when nobody could find a target to save their life. Widely available at public libraries, and ...welll, I've looked it up so much, I've even got it's usual Dewey Decimal number memorized: 940.54B Capt Beach also wrote 3 fictional sub books: Run Silent, Run Deep Dust on the Sea All are excellant Cold is the Sea 2 There is also a very good book by a British sub captain whose name escapes me at the moment...as does the title of the book. it is one of the early titles in the highly successful Bantam War Book series of paperbacks. Very different craft which they sailed. External tubes f'rinstance. I will try to find book and post relevant info. 3 Explore beyond US submarines...German subs were a different life in many ways...they did not always have the technological upper hand, and yet they came up with some really neat innovations such as MAGNETIC-ACOUSTIC-HOMING-CIRCLING TORPEDOS and Piffenwhiffer (spelling) a chemical device which would generate false sonar reflections by making air bubbles. [mod.note: "Pillenwerfer", if memory serves. - Bill ] I ahve yet to find anything concerning Japanese submariners so far, though. And last but not least, I will suggest the game Submarine by the Avalon Hill Game Company, Baltimore Maryland. The advanced version of the game will give you an idea of what it's like to try to close in for the kill... Well, I think I've rambled enough now......... Good Luck, and Good Hunting! There used to be a psycho kitty here, Ackphffzzzt! It's Bill, Oh where, oh where did my psycho kitty go... Aaron R. Kulkis Ancient Engineer
lasala@svax.cs.cornell.edu (Steve LaSala) (09/28/90)
From: lasala@svax.cs.cornell.edu (Steve LaSala) In article <1990Sep24.002015.24721@cbnews.att.com> r_anderson@flyppr.enet.dec.com writes: > >1. When a target's bearing is "marked" through the periscope, >is the angle relative to submarine (0 degrees being the bow, 180 >degrees being the stern), or relative to the "true" geographic >course? Early in the war, targets were described by relative bearing to the observing ship. This caused confusion in some of the battles in the Solomons, when sightings giving relative bearings were radioed to ships not facing the same way as the one doing the observing. Subsequently, all bearings were given relative to the earth, though whether magnetic or geographic I don't know. Did they have gyro-compasses yet?
cga66@ihlpy.att.com (Patrick V Kauffold) (09/29/90)
From: cga66@ihlpy.att.com (Patrick V Kauffold) >From article <1990Sep26.024624.26984@cbnews.att.com>, by jabishop@uokmax.ecn.uoknor.edu (Jonathan A Bishop): > > ... The TDC's on WWII > subs were analog computers which automatically calculated this lead angle > and transmitted it to the torpedo fire control system. The TDC was a _mechanical_ analog computer - no electronics (to speak of). The mechanism included high-precision integrators and some other very nifty and clever devices to solve differential equations. You can see examples of a TDC at the sub base in Groton, CT in their museum, along with the guidance mechanism for the torpedoes. The manual solution was done on the "maneuvering board" using some basic vector graphics. This same device is still used for radar navigation and multi-ship formations. A related device was the lead-computing AA gunsights and fire control equipment which appeared toward the end of the war in the Pacific on 20MM, 40MM and 5" dual-purpose guns. Surface ships also had a device called the "dead reckoning tracer" which moved a "bug" under an illuminated frosted glass table according to ship' heading and speed inputs from the gyro compass and static log. The plotter would make a dot on a paper (or chart) periodically to plot the ship's "true" motion, and also plot range/bearing points of the target being tracked, so you would have a "bird's eye view" on the DRT as well as a relative view on the maneuvering board or radar/sonar plot. (Don't know if these were on subs or not). Pat Kauffold AT&T Bell Labs
steve@uunet.UU.NET (Steve Nuchia) (10/01/90)
From: nuchat!steve@uunet.UU.NET (Steve Nuchia) >From: r_anderson@flyppr.enet.dec.com >1. When a target's bearing is "marked" through the periscope, >is the angle relative to submarine (0 degrees being the bow, 180 >degrees being the stern), or relative to the "true" geographic >course? The bearing coming off the 'scope is relative, but the boat knows her heading, so conversion is trivial -- just add the relative bearing to the true heading, modulo 360, and you have a true bearing. The relative bearing is dialed into a target computer (analog, of course) which has a true heading input as well, and it figures it all out for you. There is probably a backup computation going on using graphical techniques on paper, but I am not familiar with the details. That was WWII. Today you normally don't use the scope for targeting, you fire on a solution derived from passive sonar data, and it is probably computed digitally. >2. Can someone clearly explain the term "angle on the bow" and >how this information is useful in determining a torpedo attack? A torpedo targeting solution is derived from a series of sightings, each of which is taken from a particular spot on the ocean and returns bearing and estimated range to the target, and an estimate of the direction the target is travelling. This last datum is based on the "angle on the bow", the relative bearing of the observer from the target. A good skipper can call that angle within 10 degrees. A bow angle of 000 means you are looking at the target head on, 090 you are broad on her starboard beam, etc. The targeting computer takes the time-series of sighting data and fits an assumed straight-line, steady speed target course to it. Usually after the solution is computed and you are ready to fire you take one more confirming peek -- if the target is exactly where the computer predicts it should be you have a good solution, and you fire. >3. Can someone clearly explain what an "Is-Was" is and how it >works? >4. Can someone clearly explain what a "TDC" is and how it works? Not familiar with the terminology, sorry. -- Steve Nuchia South Coast Computing Services (713) 964-2462 "To learn which questions are unanswerable, and _not_to_answer_them; this skill is most needful in times of stress and darkness." Ursula LeGuin, _The_Left_Hand_of_Darkness_
rbeville%tekig5.pen.tek.com@RELAY.CS.NET (Robert E Beville) (10/03/90)
From: Robert E Beville <rbeville%tekig5.pen.tek.com@RELAY.CS.NET> There is nothing like putting the terminology with the physical hardware... The next time you're in Honolulu, visit the Submarine Museum... It is next door to the Arizona Memorial Visitors Center. It has the USS Bowfin docked there for boarding... the deck above the forward and aft torpedoe room have been 'butchered' to allow steps for the visitors, and you carry a radio receiver 'stick' with you to listen to the narrative about each compartment. On shore the exhibit building has displays/models from the beginning of subs up thru SSBNs... has all the WW2 sub battle flags, logs, news and memorabilia of many of the battle accounts. ... has instruments, torpedo firing consoles, nuclear missile firing consoles, etc.... some Japanese and German submarine artifacts... On the grounds are some sections of subs: the con tower + periscopes, an intact 2-man Japanese sub/torpedo, ack-ack gun from the deck of U.S. ship, and sit on a real torpedo near the snack bar/gift shop. This museum is maintained by an association of members, unlike the Arizona Memorial(by USN and Parks Dept). The museum is a very good treatment and an honor to the Silent Service. You can take your time through it, too, unlike the press of visitors for the Arizona. Now that you've been to the Arizona Memorial and The USS Bowfin, re-board city bus #20 and return to Waikiki... get out at Fort DeRussy (the movie location for "From Here to Eternity") and visit Battery Randolph. This battery, facing Waikiki Beach, is in great condition compared to the batteries at Fort Stevens, OR. and the treatment of the attack on Pearl Harbor is exhaustive... photos, models, hardware, full size displays, souvernirs... US and Japanese tanks out- doors, gift shop; rest of museum treats Korean and VN era. One room is devoted to Medal of Honor winners from among the Pacific Islands... You are not done yet... now rent a Moped bike and head for Diamond Head... not the geological feature... THE FORTRESS!!! Carry a flashlight-- you need it going through the halls and tunnels to the gun emplacements-- there's no light in most... Quite a few steps and walls to scale if you REALLY want to visit the place... On the way to the Polynesan Cultural Center, the bus driver/ tour guide will point out the remote radar installation that noticed the incoming Pearl Harbor attack force... In Honolulu harbor there is a visitors attraction of a ride in a real submarine... not like the controlled & tethered Neptune thing at Disneyland. Sorta like a glass-bottomed boat that submerges, for viewing the sealife, corals and a guy in a scuba suit feeding fish... Sorry I strayed off the sub terminolgy heading -- but when you're there... just do it! that's -OWARI- from GLOWWORM-7-9-4 best regards, rbeville@tekig5.PEN.TEK.COM Bob Beville, Tektronix, Inc., Beaverton, OR 97077
cr2r+@andrew.cmu.edu (Christian M. Restifo) (10/03/90)
From: "Christian M. Restifo" <cr2r+@andrew.cmu.edu>
nuchat!steve@uunet.UU.NET (Steve Nuchia) writes:
"That was WWII. Today you normally don't use the scope for targeting,
you fire on a solution derived from passive sonar data, and it is
probably computed digitally."
Currently, the method of finding a firing solution is as follows:
Sonar obtains a contact and assigns a tracker. This tracker is a
computer designation that "follows" the target. All data is fed into a
fire control system. Your experienced FTG (fire control technician)
then uses a three point method. He takes into account the speed, range,
and bearing of the target. Because of these three factors, it is
possible to come up with more than one firing solution. For example,
you could come up with two different bearings and ranges. It is up to
the FTG to figure out the correct one. If his current solution tells
him the target is a merchant moving at 50 knots, it is obviously the
wrong solution. He must go back and 'tweek' his controls to arrive at a
sensible one. The FTG must also watch sonar's back. If sonar fails to
realize that there are biologics on the bearing, for example, your
solution will really be screwed up. (I have seen this happen.)
Under the current rules of engagement, a US warship technically cannot
fire until there is positive proof of the target's identity. Thus, to
torpedo a ship, a submarine must make a visual sighting. OOD's in
training are still required to learn how to mark bearings via a
periscope. (Obviously, this doesn't count when you have a submerged
contact. Then you're in trouble.......)
-MIDN 3/C (SS) Christian Restifo
Carnegie Mellon NROTC
"All opinions posted here are mine and mine alone. They are not to be
taken to be the official opinions of the DoD, Department of the Navy,
NROTC, or anyone else who thinks they own me."