How did early US nuclear powered subs fix their position?

[MarkShot]

I suppose modern subs use some form of inertial guidance system and I guess if they approach the surface there is alway GPS.

O'Kane in "Wahoo" and "Clear the Bridge" talks about getting star fixes when surfacing at night to charge batteries. Given that early nuclear subs probably stayed submerged for more than a day or two, how did they fix their position? Were inertial guidance systems already in existence?

Thanks.

[TLAM Strike]

I think Skate used an Internal Navigation system when it when under the ice and surfaced at the North Pole.

[timmyg00]

Technically, a "fix" is position data received from an external source (Radio signals like GPS, visual references like the stars or land features/navaids, or radar fixes), so INS, SINS, or ESGN doesn't count as a "fix"; they are just very advanced dead-reckoning systems. Basically, you enter a position from a fix into one of these systems, and the system computes your expected position based on your course and speed. I think ESGN is still the standard for advanced DR systems today.

Older systems used for position fixes included LORAN and OMEGA (Radio Nav systems at LF and VLF) and NAVSAT (a precursor to GPS). GPS and visual (when properly performed and at slow speeds) fixes are the most accurate. Anything that takes into account at least 3 external references is considered a fix (3 radar positions of fixed objects counts as well).

TG

[Rip]

Originally Posted by timmyg00

Technically, a "fix" is position data received from an external source (Radio signals like GPS, visual references like the stars or land features/navaids, or radar fixes), so INS, SINS, or ESGN doesn't count as a "fix"; they are just very advanced dead-reckoning systems. Basically, you enter a position from a fix into one of these systems, and the system computes your expected position based on your course and speed. I think ESGN is still the standard for advanced DR systems today.

Older systems used for position fixes included LORAN and OMEGA (Radio Nav systems at LF and VLF) and NAVSAT (a precursor to GPS). GPS and visual (when properly performed and at slow speeds) fixes are the most accurate. Anything that takes into account at least 3 external references is considered a fix (3 radar positions of fixed objects counts as well).

TG

Very accurate. You must have been a forward ET or a Quartermaster

Also of note is that even without inertial navigation keeping track of a rouch ships position is not all that hard. The combination of the gyro compass and EM log for speed allows manual DR on the plot. You can even compute currents and adjust for that. The QMOW (quartermaster of the watch) is responsible for always maintaing a manual DR track for a sanity check and in case of dire emergency.

Also on the note of fixes we could add visual fix, radar fix, and the biggie Star Fix. One of my favorites. No better way to endear yourself with the Navigator than to be proficient with the sextant.

Just noticed you had listed visual, the navigation party favorite :rotfl:

[timmyg00]

I was on the Piloting party for almost my whole stint on SSN-760... loved that job Started off as a bearing recorder but quickly moved to secondary plot, did a little primary as a chow relief, and manned the periscope for some homeport approaches.

Never worked with the sextant though!!

ET1/SS TG (ESM/radio)

edit: P.S. if you were really bored, you could get RDF fixes as well...

[Rip]

Originally Posted by timmyg00

I was on the Piloting party for almost my whole stint on SSN-760... loved that job Started off as a bearing recorder but quickly moved to secondary plot, did a little primary as a chow relief, and manned the periscope for some homeport approaches.

Never worked with the sextant though!!

ET1/SS TG (ESM/radio)

edit: P.S. if you were really bored, you could get RDF fixes as well...

Of course, my BRD-7 instructor would be fuming that I forgot that one

It sounds like we have had a very comparable background. My was just on SSN699/662

[Mcarm]

They consulted the stars!

[timmyg00]

Originally Posted by Rip

Of course, my BRD-7 instructor would be fuming that I forgot that one

It sounds like we have had a very comparable background. My was just on SSN699/662

Which means you got to play on the WLQ-4, correct? I wanted that school bad

TG

[Rip]

Originally Posted by timmyg00

Which means you got to play on the WLQ-4, correct? I wanted that school bad

TG

That is why I went from a 688 to a 637. I loved the Sea Nymph but 637s didn't do much for me. I guess the Seawolfs have it as well? I even managed to go through EW A school in Pensacola, since I was a striker and returned from the fleet for BE/E and A school. Then I reenlisted for WLQ-4 school.

[scott613]

Hi...

Hmm - seems like a bunch of Et1/SS's around... Me too...

On one of those - them thar 94 boats... Well at least mine was a "stretch" and had a boomer sail... Made it look way better than the rest of the class...

We had DMINS - Dual Miniture Inertial Navigator made by Rockwell - I believe... The NAV liked to call them the Demi-Gods - and - he treated them like his children... Really kewl guy - obtw...

An Omega fix - LOL - ours would at least get us in the right ocean...

Anyway - nice o see others with a similiar background...

Good Hunting...
Scott

[timmyg00]

Originally Posted by scott613

An Omega fix - LOL - ours would at least get us in the right ocean...

That's all that counts

TG