[HN Gopher] Advanced Inertial Reference Sphere (1997)
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Advanced Inertial Reference Sphere (1997)
Author : xoa
Score : 53 points
Date : 2021-10-12 11:10 UTC (1 days ago)
(HTM) web link (nuclearweaponarchive.org)
(TXT) w3m dump (nuclearweaponarchive.org)
| [deleted]
| tablespoon wrote:
| > The AIRS has 19,000 parts. In 1989 a single accelerometer used
| in the AIRS (there are three) cost $300,000 and took six months
| to manufacture.
|
| What it would cost to build an equivalent-performance
| accelerometer today?
| politician wrote:
| I'm loading this on my iPhone. It's completely unreadable unless
| I manually switch to reader mode. Why can't Apple fix Safari to
| make sites like this render at humane font sizes? They literally
| control how it renders.
| Robotbeat wrote:
| Really? I actually read it fine as-is, and I've got the
| smallest iPhone (SE 2020) and a badly cracked screen.
|
| I much prefer this plain HTML style, and it's easy to change
| the font size, pinch to zoom, rotate to landscape, or use
| reader mode. I actually prefer this to the non-zoomable
| "mobile"-ified modern webpage. The larger view makes it easier
| to keep track of where I am in the text versus a contextless
| feed of huge font text.
|
| Try holding your phone in landscape!
| politician wrote:
| Yeah. I know how to rotate my phone and I also like plain
| text pages.
|
| I don't like that Safari thinks rendering Times New Roman on
| a recent iPhone in what is effectively 2-point font and
| waiting for me to switch to Reader Mode is a good experience.
|
| A better experience would be for Safari to render it in
| Reader Mode by default for sites where it would look better
| by default.
|
| How could it possibly do this you ask? Render the pages to an
| offscreen buffer run an image readability heuristic to pick
| the one with better properties. Convert it to a bitmap and
| select the less dense one.
| the_other wrote:
| The fact that Reader View can help you out suggests that in
| fact the site was made well. I absolutely don't want Safari
| "fixing" web content unless I ask it to (i.e. Reader View).
|
| I'm short sighted, use pinch-to-zoom and pan&scan about 95% of
| the time I'm using a computer. I'd rather this kind of content
| than most "fancy" web pages. (a well designed, readable blog is
| preferable-still).
| avalys wrote:
| This is exactly what Reader View does. On my iPhone the address
| bar flashes "Reader View Available" when I load that site. But
| you can also get to it from the context menu that includes
| other website settings.
| roywiggins wrote:
| Both Firefox and Chrome on Android render it readably without
| reader mode though, it's fair to wonder why Safari can't do
| the same.
| the_other wrote:
| Firefox (macOS & iOS) and Safari (macOS and iOS) render it
| almost exactly the same as their platform counterpart, and
| pretty close cross-platform. It's simple HTML with few
| display directives so I don't find this surprising. What
| are you seeing?
| shawkinaw wrote:
| Besides Reader View as mentioned by others, you can increase
| the zoom of the page (accessible in the "aA" button to the left
| of the URL.) This particular site renders pretty well at 200%
| on my phone in portrait. The zoom is site-specific so it won't
| screw up any other sites. It's generally a good way to make
| desktop sites legible.
| rkangel wrote:
| > and perhaps marks the end of a long process of continuous
| refinement of INS technology.
|
| Submarines are the main target for highly precise INS development
| over the last few decades. GPS doesn't work under water, so they
| rely on dead reckoning navigation over long periods of time, only
| getting a 'proper' fix on the rare occasions that they surface.
|
| Also, militaries prepare for situations in which GPS isn't
| available. The simplest case for that being jamming - GPS is a
| weak signal so fairly easy to jam over an area.
| xoa wrote:
| A number of military aircraft have incorporated systems as
| well, and they can be combined with automated celestial fixing
| systems for a hybrid astro-inertial navigation system. The
| SR-71 Blackbird used one, the Nortronics NAS-14V2 [0], and it
| was pretty amazing for the time (same as everything about the
| SR-71 granted). Even with a much less accurate INS then this
| one and primitive computer/star tracker it could maintain high
| accuracy to enable the precise flight paths and camera
| activation needed for a spyplane like that to get exact images
| from 85k feet going Mach 3.2. At altitude an aircraft can
| always see the stars with the right filter even in the day,
| which can be used to precisely correct drift.
|
| I'm glad this piece itself got some attention, the AIRS system
| to me is one of the most impressive pinnacles of
| electromechnical technology and fine machine crafting, feels
| kind of like the ultimate evolution of efforts dating back to
| the earliest days of watch making. But there are definitely a
| range of other systems from the 60s-90s still incredible in
| their own right but all the more so for what was made to work
| without all sorts of tools and modeling we take for granted
| now. And I think ongoing research to allow production of modern
| such systems at a more mass scale (perhaps a modern AINS using
| laser or fiber gyros and taking advantage of advancements in
| cheap quality digital cameras) is worthy of continued effort,
| just in case. Precise navigation via GPS has become central to
| an enormous range of modern human activity, but it is
| relatively fragile and easily jammed. If we can use tech to
| also create a reasonable fallback that seems like a valuable
| hedge.
|
| ----
|
| 0:
| https://airandspace.si.edu/webimages/collections/full/NAS-14...
| joshvm wrote:
| The NAS-14V2 also worked on the ground - it had multiple
| modes (astroinertial [default], inertial, airstart and dead
| reckon). See 10A-17 and Figure 10A-4 in the manual. If you
| read the following sections it describes procedures for
| calibrating the system in the event of a rapid takeoff (where
| a fix wasn't available), for example the runway heading can
| be entered as a quick heading fix.
|
| It wasn't particularly quick, mind - up to 96 minutes for the
| full ground procedure. They also talk about calibration in
| hangars, which is important because you don't want your
| secret spyplane sat on the apron for satellites to see for
| over an hour!
|
| There are some interesting tidbits in there. The tracker
| automatically compensates for shockwave and thermal gradients
| over the sighting window, for example.
| simplicio wrote:
| I read that sentence as not meaning that there are no future
| applications of INS, but that its unlikely that any future
| application will need to be more accurate then the AIRS.
|
| So its unlikely anyone will put $ into trying to improve on it,
| even if it continues to be used.
| KennyBlanken wrote:
| The article says AIRS accuracy was not necessary back in the
| eighties for many applications.
|
| It's important to note they mean drift over time. When you
| have at least some sort of external reference, drift is much
| less of a problem to compensate or correct for.
| rkangel wrote:
| > What I was trying to say was that governments have
| continued to invest millions of dollars in improving INS in
| the years since the AIRS was developed. The drift you need
| for days/weeks/months of navigation in a submarine is much
| much better than what you need for a few minutes of missile
| flights.
| KennyBlanken wrote:
| The article isn't about highly precise INS development. It's
| about an INS so accurate it didn't need any external
| references, and says such applications haven't been necessary
| in decades.
|
| Submarines still use external referencing. Unlike a missile, a
| submarine can use the earth's magnetic field to determine
| orientation in at least two axis. They can also reference fixed
| sound sources, know their depth, and so on.
|
| I believe highly sensitive magnetometers were used to help
| correlate position - namely, the Navy had done surveys and so a
| record of magnetometer data could be 'fit' a track to the map
| by a computer.
|
| That's the point of the article. So many navigation systems can
| use at least some sort of external reference, a completely
| independent positioning system isn't necessary.
| rkangel wrote:
| Good INS actually involves combining several sources of
| information to produce a result better than any of them. A
| Kalman filter is the normal technique for this.
|
| You're right that magnetometry information is incorporated,
| but better and better INS help too. Laser Ring gyros
| (mentioned elsewhere) were an innovation that was first
| developed for submarines. I have no idea what they use now.
| leeter wrote:
| Also airplanes, satellites etc. The standard now is laser ring
| gyroscopes as they have no moving parts, are super sensitive,
| and very light in comparison to older options. Mentour pilot
| has an episode on how these are used in the 737.
|
| https://en.wikipedia.org/wiki/Ring_laser_gyroscope
| jjoonathan wrote:
| Speaking of which, these seem like the kind of thing that
| would integrate well, but cell phones are still stuck with
| gyros/accelerometers/magnetometers that are pretty bad,
| especially in cities, double especially near buried power
| lines. The old "my heading spins rapidly in circles whenever
| I walk on a certain section of sidewalk" problem. Are there
| engineering challenges to integration or is it a spooky
| controlled technology conspiracy?
| leeter wrote:
| IIRC it's a size and power thing. You can emulate most of
| what a ring laser gyro does with good accelerometers and
| that's the better choice for most devices needing long
| battery life and compact size. Ring laser gyros (while
| small) are not that small last I checked. A quick google
| shows you can get them in about the size of a pocket watch.
| So potentially a good case addon for those that need it
| without the cost/power usage issues that would hit those
| that don't.
| jjoonathan wrote:
| By "integration" I meant "turn the module into a chip"
| rather than "put the module in a phone" -- though your
| point about power could be the answer. Some lasers and
| optics just feel like the kind of thing that a clever
| team could squeeze onto a wafer, maybe with a loop in the
| third dimension. Or maybe just require two of them.
| There's probably a good answer as to why that's harder
| than it seems, I just don't know what it is.
| leeter wrote:
| It looks like there is work in that direction... but like
| most things it's 10years (TM) away.
|
| https://www.nature.com/articles/s41566-018-0266-5
| https://arstechnica.com/science/2018/11/tiny-laser-
| gyroscope...
| jjoonathan wrote:
| Cool, thanks for the links!
| phkahler wrote:
| Submarines should also be able to use passive sonar and a map
| of the sea floor.
| xxpor wrote:
| Two things: couldn't the sonar pings be detected if you're
| close enough? And does anyone actually have a detailed enough
| map of the sea floor to do navigation based on it?
| monocasa wrote:
| Passive sonar doesn't use pings.
| Arrath wrote:
| Those that do have such detailed maps, if they do, probably
| aren't likely to talk about them.
| tablespoon wrote:
| > Those that do have such detailed maps, if they do,
| probably aren't likely to talk about them.
|
| Though I think it's a reasonable inference that the US is
| probably didn't have them in 2005 for the whole ocean:
|
| https://en.wikipedia.org/wiki/USS_San_Francisco_(SSN-711)
| #Co...
|
| > The seamount that San Francisco struck did not appear
| on the chart in use at the time of the accident, but
| other charts available for use indicated an area of
| "discolored water", an indication of the probable
| presence of a seamount. The Navy determined that
| information regarding the seamount should have been
| transferred to the charts in use--particularly given the
| relatively uncharted nature of the ocean area that was
| being transited--and that the failure to do so
| represented a breach of proper procedures.
|
| > Nonetheless, a subsequent study by UMass Amherst
| indicated that the Navy's charts did not contain the
| latest data relevant to the crash site because the
| geographical area was not a priority for the Defense
| Mapping Agency.
| KennyBlanken wrote:
| Nobody said the USN had them for the whole ocean. The
| point is that the Navy likely has numerous methods of
| providing external references to a submarine's INS.
|
| Map != position, by the way...
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(page generated 2021-10-13 23:01 UTC)