4 ms·

To be more concrete, space rockets nearly all fly with inertial navigation, but they are extreme case, because most use only inertial navigation just few minute

by simne 2y ago

To be more concrete, space rockets nearly all fly with inertial navigation, but they are extreme case, because most use only inertial navigation just few minutes (so all those classic gyros/accelerometers integrated errors are small enough to successful enter stable orbit, and then using some sort of radio or optical fine measurements and making corrections with fine engines). Planes flights are much more lengthy than rockets - I think, typical ~40 minutes or more (most long I hear 20 hours), so INS could integrate huge mistake.

p_l 2y ago
INS essentially was expensive and AFAIK once GPS became available started to drop off in use outside of military. And with GPS availability coinciding with switching to more modern integrated Flight Management System/Computer, a lot of planes simply don't have INS installed.
- scrlk 2y ago
  > a lot of planes simply don't have INS installed Perhaps in general aviation, but I can't think of any modern commercial airliner without an INS via the air data inertial reference unit.
  - simne 2y ago
    Many small planes don't have INS in typical meaning, but their pilot is INS computer, calculated approximate nav from air data (air speed + weather data + compass or radio compass).
  - p_l 2y ago
    Except ADIRU isn't INS. The INS unit is separate and often has its own set of gyros and has to be connected as separate input to FMS or other navigational computers, same as connecting GPSes or other radio nav components. For example the current model of popular Universal Avionics UNS1 series of NCU (navigational computer part of FMS) come with built-in augmented GPS receiversz but do not mention INS functionality at all even in extended models. Don't have access to manuals at the moment, but I'd expect to see INS as optional to connect over one of the external connectors on the MCU, as it was on the older models without integrated GPS
    - scrlk 2y ago
      In that case, I stand corrected. I had assumed that the ADIRU’s inertial reference data from its gyroscopes and accelerometers would feed into the FMS to provide INS capabilities in case GNSS was unavailable.
      - p_l 2y ago
        ADIRU in its minimal common form (some vendors might make a beefier one, who knows) provides the equivalent of old pneumatic "air data central" + artificial horizon and turn indicator gyros. GNSS becoming "reasonably easy" to add meant that there was way less push to integrate INS after early use in transoceanic flights
- simne 2y ago
  Your words are near to truth. Before GPS from nearly 1950s used LORAN navigation system, with similar to GPS principles, but used long waves and have relatively low precision - about kilometer at best. https://en.wikipedia.org/wiki/LORAN https://en.wikipedia.org/wiki/LORAN Before LORAN, used radio beacon navigation and star navigation (from Newton time), and good human navigator could achieve about 50km precision. You could easy see signs of star navigation on good preserved old planes - they all have some sort of fully glass dome, or blister, to provide good near semi-sphere view. And sure, all those before-GPS era planes have separate navigator job position, sometimes shared with mechanic. https://www.reddit.com/r/WWIIplanes/comments/59xfkz/pby_waist_gunner_mounting_port_side_gun_blister/?rdt=52558 https://www.reddit.com/r/WWIIplanes/comments/59xfkz/pby_wais... You could ask, how planes could fly with 50km precision? Answer is easy - at all plane routes built ground structures easy seen from air and last mile navigation become essentially visual flight, nothing more, nothing less. On some places ground navigation structures preserved now, for examples: https://en.wikipedia.org/wiki/Airway_beacon https://en.wikipedia.org/wiki/Airway_beacon https://en.wikipedia.org/wiki/Transcontinental_Airway_System https://en.wikipedia.org/wiki/Transcontinental_Airway_System
  - p_l 2y ago
    LORAN was mostly long range over sea, on the ground we had NDB, DME, VOR, etc all ultimately linking into "airways" for higher altitude operations where earth might be not visible due to cloud cover for example
foldr 2y ago
I believe submarines navigate long distances using INS. I don’t know how accurate it is, or how often they have to make corrections using other data. But ballistic missile submarines can’t really use active sonar or surface with any frequency, so I’m not sure what other method they’d use.
- simne 2y ago
  I talked with captain of submarine. He said, in real life navigation was not reliable, so they have to go to surface and make adjustments with some classic navigation - radio beacons and star navigation. And civilian education now close to forgot star navigation, but navy still train people to navigate with stars and learn Morse code. https://news.ycombinator.com/item?id=43319923 https://news.ycombinator.com/item?id=43319923
- simne 2y ago
  > ballistic missile submarines can’t really use active sonar or surface with any frequency Detect semi-surfaced submarine at night is really hard, if don't have intelligence data that it will surface on some non-random position. From experience of Ukrainian war, my country have success with eliminating surface military ships, because have constantly monitoring their moves with satellites, but I cannot remember any case when semi-surfaced submarine was hit.
  - foldr 2y ago
    Are they not easy to detect on radar? Even during WWII, radar got good enough to detect submarine periscopes. It's hard to imagine that a partially surfaced submarine wouldn't have a significant radar return. That doesn't mean that they're easy to detect at long ranges, but I would have thought that partially surfacing or raising a periscope would be a significant risk to a submarine if the enemy knew its rough location. At a guess, Ukraine probably can't deploy naval assets with powerful radar close enough to where Russian subs are operating. But an adversary with a more powerful navy might be able to.
    - maratc 2y ago

by simne 2y ago

p_l 2y ago

INS essentially was expensive and AFAIK once GPS became available started to drop off in use outside of military. And with GPS availability coinciding with switching to more modern integrated Flight Management System/Computer, a lot of planes simply don't have INS installed.

scrlk 2y ago
> a lot of planes simply don't have INS installed Perhaps in general aviation, but I can't think of any modern commercial airliner without an INS via the air data inertial reference unit.
- simne 2y ago
  Many small planes don't have INS in typical meaning, but their pilot is INS computer, calculated approximate nav from air data (air speed + weather data + compass or radio compass).
- p_l 2y ago
  Except ADIRU isn't INS. The INS unit is separate and often has its own set of gyros and has to be connected as separate input to FMS or other navigational computers, same as connecting GPSes or other radio nav components. For example the current model of popular Universal Avionics UNS1 series of NCU (navigational computer part of FMS) come with built-in augmented GPS receiversz but do not mention INS functionality at all even in extended models. Don't have access to manuals at the moment, but I'd expect to see INS as optional to connect over one of the external connectors on the MCU, as it was on the older models without integrated GPS
  - scrlk 2y ago
    In that case, I stand corrected. I had assumed that the ADIRU’s inertial reference data from its gyroscopes and accelerometers would feed into the FMS to provide INS capabilities in case GNSS was unavailable.
    - p_l 2y ago
      ADIRU in its minimal common form (some vendors might make a beefier one, who knows) provides the equivalent of old pneumatic "air data central" + artificial horizon and turn indicator gyros. GNSS becoming "reasonably easy" to add meant that there was way less push to integrate INS after early use in transoceanic flights
simne 2y ago
Your words are near to truth. Before GPS from nearly 1950s used LORAN navigation system, with similar to GPS principles, but used long waves and have relatively low precision - about kilometer at best. https://en.wikipedia.org/wiki/LORAN https://en.wikipedia.org/wiki/LORAN Before LORAN, used radio beacon navigation and star navigation (from Newton time), and good human navigator could achieve about 50km precision. You could easy see signs of star navigation on good preserved old planes - they all have some sort of fully glass dome, or blister, to provide good near semi-sphere view. And sure, all those before-GPS era planes have separate navigator job position, sometimes shared with mechanic. https://www.reddit.com/r/WWIIplanes/comments/59xfkz/pby_waist_gunner_mounting_port_side_gun_blister/?rdt=52558 https://www.reddit.com/r/WWIIplanes/comments/59xfkz/pby_wais... You could ask, how planes could fly with 50km precision? Answer is easy - at all plane routes built ground structures easy seen from air and last mile navigation become essentially visual flight, nothing more, nothing less. On some places ground navigation structures preserved now, for examples: https://en.wikipedia.org/wiki/Airway_beacon https://en.wikipedia.org/wiki/Airway_beacon https://en.wikipedia.org/wiki/Transcontinental_Airway_System https://en.wikipedia.org/wiki/Transcontinental_Airway_System
- p_l 2y ago
  LORAN was mostly long range over sea, on the ground we had NDB, DME, VOR, etc all ultimately linking into "airways" for higher altitude operations where earth might be not visible due to cloud cover for example

foldr 2y ago

I believe submarines navigate long distances using INS. I don’t know how accurate it is, or how often they have to make corrections using other data. But ballistic missile submarines can’t really use active sonar or surface with any frequency, so I’m not sure what other method they’d use.

simne 2y ago
I talked with captain of submarine. He said, in real life navigation was not reliable, so they have to go to surface and make adjustments with some classic navigation - radio beacons and star navigation. And civilian education now close to forgot star navigation, but navy still train people to navigate with stars and learn Morse code. https://news.ycombinator.com/item?id=43319923 https://news.ycombinator.com/item?id=43319923
simne 2y ago
> ballistic missile submarines can’t really use active sonar or surface with any frequency Detect semi-surfaced submarine at night is really hard, if don't have intelligence data that it will surface on some non-random position. From experience of Ukrainian war, my country have success with eliminating surface military ships, because have constantly monitoring their moves with satellites, but I cannot remember any case when semi-surfaced submarine was hit.
- foldr 2y ago
  Are they not easy to detect on radar? Even during WWII, radar got good enough to detect submarine periscopes. It's hard to imagine that a partially surfaced submarine wouldn't have a significant radar return. That doesn't mean that they're easy to detect at long ranges, but I would have thought that partially surfacing or raising a periscope would be a significant risk to a submarine if the enemy knew its rough location. At a guess, Ukraine probably can't deploy naval assets with powerful radar close enough to where Russian subs are operating. But an adversary with a more powerful navy might be able to.
  - maratc 2y ago