Difference between IRS and INS

[john_tullamarine]

Spooky me too!
see if it happens again : l@ser
It blinking well did happen ...again !

I have no idea why it should apply to laser but my guess is that some automatic parsing in the software is causing the glitch. Suggest we just nod our heads in wonderment and ignore it ...

[vapilot2004]

Testing. . .

Baser, laser, taser, maser, laser, phaser.

I just had to try this. Sorry and please carry on.

[CV880]

Hi Graybeard,
Litton 58 was actually called an ISU (Inertial Sensor Unit) which was an earlier name for an IRU.
I called it an IRU in my earlier post which I realised was wrong after I had hit send.

[Abu Bebo]

Acronym

Maybe as "laser" is an acronym we should be spelling it "LASER"; we still talk about ATIS, STAR and DETRESFA
Lets try: L@SER

Only kidding: LASER

Nope, typed in capitals and changed by the software. I'll get my coat

[b377]

Simmer down guys these are just silly acronyms. To cool you down further remember that Apollo misions to the moon used a single INS with the attendance gimbal lock problems and all. Today FMSs backed by two or three independents INSs are the norm and if these 3 units fail, so what, you still have GPS, LORAN, VOR/DME in triplicate and ATC. Getting lost is not an acceptable excuse for not getting there any more.

What ever happened to the good old navigator? Let me see what were they known as ....

[Graybeard]

Thanks for the correction on the ISU, CV880. They say memory is the second thing to go; can't remember what's first.

The INU is the inertial platform of an INS LRU (Line Replaceable Unit).

GB

[SOPS]

I am interested in this..why was a gimbal lock such a bad thing in Apollo? How did it work?

[b377]

Spinning wheel gyros with mechanical gimbals can exceed limits as the gimbals rotate and two or more gimbals can align or occupy teh same plane. In the case of Apollo space craft ( or any thing that causes the rotation to exceed limits) on gimbal lock the angle transducers lose unabiguous axis inputs - the INS computer can not calculate correct craft orientation or attitue wrt intertial axes ( fixed stars) which is what the gyros are for.

Without attitude correct rocket sequence firing to achieve a given course is impossble.

I think A-13 had to resort to sextant.

Gimbal Angles and Gimbal Lock