[HN Gopher] The guidance system and computer of the Minuteman II...
___________________________________________________________________
The guidance system and computer of the Minuteman III nuclear
missile
Author : magnat
Score : 255 points
Date : 2024-08-19 19:06 UTC (1 days ago)
(HTM) web link (www.righto.com)
(TXT) w3m dump (www.righto.com)
| kens wrote:
| Author here if anyone has questions...
| OldSchool wrote:
| Excellent presentation, thank you!
|
| The machinery is ironically beautiful to look at!
|
| How did this compare to its approximate contemporary in the
| USSR ?
| jojobas wrote:
| Soviet 70's machines were hand-woven ferrite plate, stacked
| PCB sandwiches. Not pretty at all.
| metadat wrote:
| What is the purpose of the window?
|
| (As labeled in https://static.righto.com/images/minuteman-
| mmiii/guidance-la...)
| QuinnyPig wrote:
| From the article:
|
| > Also note the window in the side of the missile to allow
| the light beam from the autocollimator to reflect off the
| guidance platform for alignment.
| metadat wrote:
| Thanks, I finished reading the article while in the air and
| realized my faux pas without any Internet! Cheers.
|
| It's labeled in another image towards the end:
|
| https://static.righto.com/images/minuteman-mmiii/silo.jpg
| ulnarkressty wrote:
| The article states that the system was cooled using a solution
| of sodium chromate to inhibit corrosion. However the wiki page
| of sodium chromate states that it is very corrosive. Is it a
| typo or something?
|
| It's also mentioned that the computer uses one of the first
| integrated circuits for miniaturization. Do you know if this
| can be definitely traced to advances in industrial/consumer
| products? It's a common trope that military research trickles
| down - so it's a "good" thing. It's not clear if this actually
| happens or if progress would have been made eventually without
| the need for these machines.
| philipkglass wrote:
| _The article states that the system was cooled using a
| solution of sodium chromate to inhibit corrosion. However the
| wiki page of sodium chromate states that it is very
| corrosive. Is it a typo or something?_
|
| Chromates are effective corrosion inhibitors for aluminum
| alloys and some other metals. Here's a brief article about
| how they work with aluminum:
|
| "Inhibition of Aluminum Alloy Corrosion by Chromates"
|
| https://www.electrochem.org/dl/interface/wtr/wtr01/IF12-01-P.
| ..
|
| When the Wikipedia entry's "Safety" section says that sodium
| chromate is corrosive, in context it means "destructive to
| human tissue by contact." That is, like sodium hydroxide
| (lye) and many other chemicals, in concentrated form it can
| destroy skin and eyes.
| kens wrote:
| Sodium chromate is highly corrosive to humans (as well as
| carcinogenic, see the movie Erin Brockovich). However, it
| inhibits corrosion in metal, acting as a passivating
| inhibitor, forming some sort of protective oxide.
|
| I've been doing a lot of research on the impact of Minuteman
| and Apollo on the IC industry (which led to the current
| post). The Air Force likes to take credit for the IC
| industry, as does NASA, but the actual influence is
| debatable. My take is that both projects had a large impact
| on the IC industry, more from Minuteman. However, even in the
| absence of both projects, there was a lot of interest and
| demand for ICs. If I had to take a quantitative guess, I'd
| say that those projects advanced ICs by maybe a year, but the
| basic trajectory would have remained the same.
| dboreham wrote:
| Ken, the story I heard wasn't so much that the MM3 demand
| created the IC industry, but rather that it created the
| _quality_ culture that then led to ICs being widely
| accepted, because they were reliable. The AF had such
| purchasing power due to the program that they were able to
| impose quality standards on the industry that hitherto were
| not expected.
| izacus wrote:
| How does a 1-bit serial computer actually work? E.g. how does
| an ADD operation look like? It's a bit hard to picture.
| kens wrote:
| In a serial computer, you have a 1-bit ALU, say an full adder
| that generate a sum and carry. Each clock cycle you read two
| bits and feed them into the adder, and then you write back
| the sum. You hold the carry in a flip-flop to use in the next
| clock cycle. It's just like doing a binary addition with
| pencil and paper, one bit at a time.
|
| Note that you need to start with the lowest bit with a serial
| computer, which explains why x86 is little-endian. It goes
| back to the Datapoint 2200, a desktop computer made from TTL
| chips and running serially. The Intel 8008 processor was a
| copy of the Datapoint 2200 (as was the Texas Instruments TMX
| 1795). Although the 8008 was parallel, it copied the little-
| endian architecture of the Datapoint 2200.
| izacus wrote:
| Hmm, I see - how do the opcodes work and jumping then? Do
| you also read them bit-by-bit and reconfigure the ALU /
| codepaths? Is addressing also single-bit?
| howerj wrote:
| Here's a 16-bit bit-serial computer I made and tested on
| an FGPA https://github.com/howerj/bit-serial. If you look
| at `bit.c` it looks like an ordinary 16-bit Accumulator
| based Virtual Machine with a few odd instructions that
| make more sense when you know how a bit serial CPU works,
| nothing special about it. However the VHDL in `bit.vhd`
| shows how all those instructions are processed in a bit
| serial fashion, how data is fetched and stored in shift
| registers, etcetera.
|
| The bit serial CPU in `bit.vhd` is actually customizable,
| you can make a 32-bit, a 14-bit, or a 27-bit CPU if you
| want from that VHDL quite easily.
| seoulbigchris wrote:
| I've often wondered if serial computers could have a useful
| role again. At very high clock speeds and wide data paths,
| you hear about trouble controlling signal skews. In
| contrast, imagine a serial computer clocking data around at
| 8 GHz vs. an 8-bit computer clocking data at 1 GHz. You
| have to deal with faster speeds, but no skew, and it seems
| like a 1-bit ALU might be simpler (and faster) than a
| 64-bit one.
| kragen wrote:
| if you write down two binary numbers on paper and add them,
| you will almost certainly do the computation bit-serially,
| adding each pair of corresponding bits with the carry from
| the previous operation. serial computers work the same way
| bloopernova wrote:
| Do you have any plans to write about World War 2 era mechanical
| firing computers? I searched your blog but didn't see anything.
|
| Or maybe early RADAR systems of 1942 and later?
|
| (been reading about WW2 Pacific naval/air wars, and I am
| curious about these new-at-the-time technologies)
| kens wrote:
| I planned to write about the electromechanical Torpedo Data
| Computer used in WWII, but I got distracted.
| nullhole wrote:
| Any opinion on the book 'Inventing Accuracy'? It covers the
| Minuteman guidance system for a few chapters.
| kens wrote:
| I've got the book on my desk right now :-) It's a bit of an
| unusual book because it is full of technical details but it
| also has a fair bit of sociological content like "the
| construction of technical facts", "technological
| determinism", and "sociology of technological knowledge".
| This is in contrast to, say, "Minuteman: A Technical
| History", which is strictly facts and details. They are both
| good books, but it is interesting how they have completely
| different styles and focuses.
| nullhole wrote:
| I agree with your observations about "Inventing Accuracy".
| Personally I found the sociology focus a bit unexpected,
| and maybe a little too strong in some chapters, but still a
| worthwhile point of view.
|
| I will definitely be taking a look at "Minuteman: A
| Technical History". Books dealing at least in part with the
| history of IMUs are few and far between.
| bun_terminator wrote:
| I have a morbid curiosity to know how much of all that old tech
| would actually work in a full scale nuclear war, launching all
| missiles. Seems so well thought-out, but also incredibly hard to
| test. Really fascinating article!
| akira2501 wrote:
| Why would it be hard to test? We have our own anti-missile
| technology, so it's ostensibly as simple as not putting a
| payload on the missile, then launching it at your own test
| range.
| dumah wrote:
| The physical environment these weapons were designed for is
| extreme and only possible to simulate piecemeal.
|
| Each stage needs to function in the presence of nearby
| nuclear detonations, resulting from both adversary and
| friendly weapons.
|
| These detonations are expected to cause severe shock,
| thermal, radiation, and electromagnetic transients.
|
| In the case of the most important targets, it is guaranteed
| that numerous detonations near the target, from ABM systems
| and friendly impacts, will occur, and these systems have been
| engineered and are expected to perform reliably under such
| conditions.
| akira2501 wrote:
| This weapon is an ICBM. The payloads are delivered to orbit
| then launched at the target from there. You're already
| facing severe shock, thermal, radiation and EM transients
| just to get to orbit. Once there, you're ultimately
| dropping MIRVs, the design of which is considerably
| simpler.
|
| The delivery vehicle and the reentry/payload vehicle have
| entirely different life cycles and deployment concerns.
| nradov wrote:
| The weapons technically never enter orbit; they follow a
| sub-orbital trajectory.
| kens wrote:
| Moreover, putting nuclear weapons in orbit would be a
| violation of the 1967 Outer Space Treaty. As an aside,
| Atlas and Titan were capable of reaching orbit, and were
| used for the Mercury and Gemini missions respectively.
| Minuteman, on the other hand, was not powerful enough to
| put a payload in orbit.
| arethuza wrote:
| The Soviets did have a "Fractional Orbital Bombardment
| System" (FOBS) for a while:
|
| https://en.wikipedia.org/wiki/Fractional_Orbital_Bombardm
| ent...
|
| It's main advantage being that it could attack the US
| from the South (or presumably any other direction).
| cpgxiii wrote:
| A key operational requirement for any fixed US ICBM is
| that you can launch during and after an enemy nuclear
| attack on your silo fields (silos dispersed and hardened,
| redundant command links, etc) and penetrate defended
| areas protected by nuclear-armed ABM systems (e.g.
| A-135/ABM-4 Gorgon). That means resistance to high
| radiation flux from nearby detonations at both launch and
| reentry, as well as the need to survive flying through
| the expected debris clouds kicked up by previous
| detonations.
| akira2501 wrote:
| If the enemy is using ICBMs you are very likely to get
| yours launched well before their weapons make the first
| impact. If that weren't true, then the high flux
| conditions do not last for a substantial period, so
| you're describing a problem that would occur if an enemy
| warhead hit at the precise moment yours was leaving the
| silo. Your enemy cannot possibly have this precision in
| timing.
| JumpCrisscross wrote:
| > _If the enemy is using ICBMs you are very likely to get
| yours launched well before their weapons make the first
| impact_
|
| This is a terrible assumption to make if you're trying to
| deter nuclear war.
|
| Unless any random outage or terrorist/conventional strike
| against one's early-warning radars, or errant satellite
| launch by a low-grade nuclear power, is automatic grounds
| for a universal MAD offensive.
| mrguyorama wrote:
| >Unless any random outage or terrorist/conventional
| strike against one's early-warning radars, or errant
| satellite launch by a low-grade nuclear power, is
| automatic grounds for a universal MAD offensive.
|
| They are, that's what Stanislav Petrov is famous for
| helping prevent. A single early warning satellite had an
| anomalous reading and everyone wanted to start nuclear
| Armageddon, only prevented because he didn't believe the
| US would send only a few warheads, to the point he was
| willing to bet his country on it.
|
| Famously the US plans early on didn't really have any
| distinction as to _who_ fired, and the only retaliatory
| option available was to go full send with everything on
| Soviet cities.
|
| Specifically about satellite launches, yeah, that's a
| genuine concern, which is why they are talked about
| publicly, even when it's a classified spy satellite going
| up, why you are very loud and public about testing
| ballistic missiles anywhere you do so, and why both the
| US and USSR worked very very hard on making computers to
| quickly estimate the landing point of a ballistic launch.
|
| Meanwhile the entire point of nuclear missile submarines
| is that ground based missiles are an explicit target of
| known enemies, and thus not likely to survive a first
| strike. They are not intended or planned to survive such
| a first strike, which is why we had SAC flying B52s 24/7
| for like 40 years. Any missiles that aren't out of their
| tubes before enemy detonation are mostly assumed lost.
|
| In fact, nuclear submarines have gone a long, long way to
| improve the situation, because now you don't have to rely
| on those ground based or air based warheads as much, so
| you can be more conservative in your judgement. If you're
| wrong and the soviets really did initiate nuclear war, oh
| well, Tridents will show them the error of their ways.
|
| The biggest "eh, we should wait before we launch" cause
| is simply the lack of tension between world powers.
| Despite Russia's blustering, in official capacities they
| have not signaled that they are looking to launch nukes.
| They have not significantly increased their readiness,
| towards a large scale anti-NATO war, to the point that
| they are literally removing defenses from the border with
| Finland in order to divert those resources to invasion.
|
| There has only been one "Oh shit oh god" moment that I
| know of; when an S300 missile (which I believe later
| turned out to be Ukrainian) landed in Poland and killed a
| farmer. There was a crisis meeting of NATO members.
| bun_terminator wrote:
| I was thinking mostly of the bits of the tech designed for
| working when the launch site is hits with nuclear explosions
| kens wrote:
| They did dozens of tests of the Minuteman missiles and reentry
| vehicles. The warheads were tested underground until the
| comprehensive test ban treaty of 1996. So it's pretty likely
| that the systems would work if needed. One risk is that
| something may have gone wrong with the warheads over 30 years.
| (Of course they maintain them, but without testing you can't be
| sure.) Another risk is that you don't know how the missiles
| would function in an environment with nuclear blasts and EMP
| all over the place. They put a whole lot of effort into
| mitigating these factors, but you can't be sure. Hopefully we
| never find out.
| leeter wrote:
| Note: While none of the Annex 2 countries that are
| signatories have conducted tests since 1996; the treaty never
| took effect because it was never ratified by all the required
| countries. Most notably the US, China, and Russia (although
| all three signed). In 2023 Russia officially withdrew,
| allegedly based on the US non-ratification. At least one
| political candidate for the presidency in the US has
| advocated for resuming testing. It is not inconceivable that
| testing could resume in the near future.
|
| Opinion: I don't think the US would if Russia or China didn't
| first. China likely won't for the same reason the US doesn't
| need to: they have super-computers and the sims line up with
| the data from prior tests. Russia might however if only to
| saber rattle, although they likely don't need to either.
| Russia however is likely not in any hurry to have a test
| failure right now. So while testing could resume, I wouldn't
| put money on it.
| Joel_Mckay wrote:
| There was an area of redundant symmetric electronic design,
| that auto compensated for component level failures. I remember
| reading an "aerospace" manual all about it when I was a kid. It
| was necessitated when the tolerance and reliability of
| components were terrible by today standards.
|
| Note too, that mil spec silicon is different in that it is
| resistant to CMOS latch-up, redundant CRC protected self-
| correcting consensus register ops, and large gate sizes less
| sensitive to Gamma radiation.
|
| It was an interesting time, and a few people still think living
| under the Sword of Damocles builds character. =3
| detourdog wrote:
| Here is a link to a bunch of artifacts from of those
| computers and their development.
|
| https://www.icloud.com/sharedalbum/#B0YG4TcsmGWIVSf
| kens wrote:
| Nice collection of Autonetics photos! Are those your
| photos?
| detourdog wrote:
| Yes, I'm the guy the always promises to mail you the
| chips but always fails at the follow through.
|
| Seeing this article make me Think I really have to get
| you these chips.
| kens wrote:
| I'm always ready with my microscope to take some die
| photos!
| Joel_Mckay wrote:
| There are several chip lines that used this method over
| the years for various reasons:
|
| https://en.wikipedia.org/wiki/Wafer_backgrinding
|
| Best regards =3
| Ringz wrote:
| Impressive work and very interesting! Since I was instantly
| interested in the tiny ,,window" and its purpose I found a little
| error:
|
| ,,Aligning the missile was a tedious process that used the North
| Star*t* to determine North.,,
| kens wrote:
| Thanks! I fixed that.
| firesteelrain wrote:
| Your article on the guidance system reminds me of this
| https://youtu.be/bZe5J8SVCYQ?si=LuVwiZ7NEI21czoH
| kens wrote:
| I refrained from including that link :-)
| beerandt wrote:
| Even as someone who's actually done the math that video is
| trying to explain(in an actual class covering missile
| geodesy), it's still so absurd.
|
| But honestly only about half as crazy as GPS would sound if
| you tried to put it in similar terms. And that's before
| considering the signal itself is way below the noise floor.
|
| As much as I love these technical writeups, I wish more
| people who understand the slightly expanded bigger picture/
| implications of the missile technologies would write what
| they know before the generation goes extinct.
|
| There's so many dots that are easily connected from articles
| like these... but I suspect some level of classification
| prevents those in the know from being able to publish.
|
| The bulletin of atomic scientists is the only non-fringe
| source that ever comes close. (Their article on the new
| generation of warhead fuses is a great resource for those
| wanting to go down the rabbit hole. Even it now seems to have
| been scrubbed from their site. [0])
|
| [0] https://web.archive.org/web/20170307194641/https://thebul
| let...
|
| Eta working bulletin link:
| [1]https://thebulletin.org/2017/03/how-us-nuclear-force-
| moderni...
| mananaysiempre wrote:
| Looks like thyey just didn't care enough to do a redirect:
| https://thebulletin.org/2017/03/how-us-nuclear-force-
| moderni...
| beerandt wrote:
| Thanks- edited/added.
|
| Multiple search engines still pointed to the stale link.
|
| When there's as much secrecy by obscurity as I've seen
| re: the topic, my tinfoil hat always assumes the worst.
| minkles wrote:
| Ha that's great. I was expecting this for some reason
| https://www.youtube.com/watch?v=yXFh54fc8GM
| benjam47 wrote:
| I live several miles from a Minuteman silo in Montana, maintained
| by Malmstrom Air Force Base. The underground cabling between
| sites is also an interesting read
| (https://minutemanmissile.com/hics.html). Anytime I want to dig
| on my property, I have to make sure it won't interfere with their
| pressurized cables. I have heard a story from someone that did
| accidentally cut a cable, and Malmstrom AFB was able to locate
| the break and respond rapidly. I am a volunteer firefighter, and
| our station has a VHS tape and a paper guide titled "Incident
| Guide for Missile Field Fire Response" provided to us by the DoD
| regarding our role in responding to fire incidents near or at a
| silo. A year or so ago, we did respond to a fire near a silo, but
| it occurred entirely outside the security fencing. My
| understanding is that the personnel at the silos also have their
| own ability to respond to fires.
| nonethewiser wrote:
| > Anytime I want to dig on my property, I have to make sure it
| won't interfere with their pressurized cables.
|
| Sounds like a serious weak point
| cpgxiii wrote:
| The missile silos and control facilities are connected in a
| sort of semi-mesh topology, so any one cable break is
| unlikely to cause a communications failure. There are backup
| launch control interfaces available via airborne platforms
| (specifically the E-6 today) as well.
|
| Digging into one of the cables is going to get you a prompt
| and unpleasant visit from base security.
| toomuchtodo wrote:
| https://news.ycombinator.com/item?id=41019604
|
| https://computer.rip/2024-07-20-minuteman-missile-
| communicat...
| preisschild wrote:
| They have redundancy. But they obviously want to know where
| it happened in case it was sabotage.
| bunabhucan wrote:
| Image showing the layout/redundancy of the communications:
|
| https://en.m.wikipedia.org/wiki/LGM-30_Minuteman#/media/File.
| ..
|
| There are alternate ways to launch the missiles (e.g. radio
| from a plane) in the event of an attack.
| kev009 wrote:
| The tape is probably a reponse to some infamous
| disasters/tragedies:
|
| * https://en.wikipedia.org/wiki/LGM-25C_Titan_II#Mishaps
|
| * https://en.wikipedia.org/wiki/1965_Searcy_missile_silo_fire
|
| *
| https://en.wikipedia.org/wiki/1980_Damascus_Titan_missile_ex...
| beerandt wrote:
| How different is it than a standard 811 utility-locate call?
|
| Actual change in procedure? Or just extra cheek-clinching?
| benjam47 wrote:
| Today it is the same thing (part of an 811 call). In the
| distant past, it was a separate call.
|
| Around 2000 land owners are affected, and anecdoctally it
| seems to add a few days to a 811 response (~a week instead of
| 2-3 days).
| JoeDaDude wrote:
| But isn't it the case that there is typically no personnel at
| the silo (or Launch Facility LF) itself? Instead, the Missile
| wing Commanders at the Launch Control Centers (LCC) some
| distance away. The LCC commands some number of LFs remotely.
|
| https://en.wikipedia.org/wiki/Missile_launch_control_center
| benjam47 wrote:
| Good question. They definitely do have launch control
| centers. All available information online does seem to
| indicate that is the case that the silos themselves are
| unmanned. My understanding is that there was some security on
| site, but that is just based on second hand stories I've
| heard, and may not be true.
|
| I do see military vehicles traveling to and from the one that
| I am close to semi regularly, perhaps a month or so on
| average.
|
| As far as fire response, they likely have their equipment for
| that at the control centers as well.
| plasma_beam wrote:
| Given we are talking about nuclear missiles, I'd like to
| think that while unmanned and housing decades-old tech,
| that the sites themselves have state of the art top secret
| levels of security. Then again I grew up in northern VA and
| we all used to assume as kids that the pentagon had
| missiles to protect from attack, then 9/11 happens, things
| like Jan 6, and you lose that confidence..
| minkles wrote:
| Just a bit of additional trivia. Jim Williams (somewhat famous EE
| at Linear) had a minuteman computer on his living room wall known
| as "the tapestry": https://www.eetimes.com/photo-gallery-
| remembering-jim-willia... (last picture in particle). Not sure
| what revision.
| kens wrote:
| Those boards are from the Minuteman I, the cylindrical
| computer. I wonder what happened to his boards?
| minkles wrote:
| Thanks for confirming (and thanks for the excellent article
| btw). I wish I knew for sure. Anything of that nature
| deserves to be carefully preserved.
| blantonl wrote:
| These systems are so vastly complicated, old, and rarely if ever
| launched. These aren't like data center generators which have
| testing schedules etc, and STILL there are failure points.
|
| I really wonder what the failure rate would be if they were all
| actually launched today. And I mean failure, from not lifting
| off, to failure in flight, to misguided warheads etc.
| minkles wrote:
| They have operational models with statistical failures included
| so they understand what the interception and failure
| probabilities likely are for each item at component level. You
| can design that into a system and test for it.
|
| Obviously you can't factor in unknown problems but that's what
| drills and test flights are for.
| krisoft wrote:
| But they do have testing schedules. They certainly tests the
| electronics regularly. And every so often they randomly pick a
| missile and launch them from Vandenberg.
|
| https://www.spaceforce.mil/News/Article-Display/Article/3796...
|
| > I really wonder what the failure rate would be if they were
| all actually launched today
|
| I hope we will never find out. But certainly there would be
| many duds. But this is calculated into the effectiveness of the
| system by simply having more missiles. That is how it achieves
| its goal of dettering a would be attacker. (Not even talking
| about how there are two other totaly separate legs of the
| nuclear triad with dissimilar personel and technical
| solutions.)
| m_mueller wrote:
| > randomly pick a missile and launch them from Vandenberg
|
| Jeff! Did you remember to take out the warheads? Jeff?!
| mrguyorama wrote:
| Somewhat soberingly, earlier in the war with Ukraine,
| Russia managed to launch a ballistic missile with a
| concrete "Warhead simulator" installed, literally a mass
| designed to test the launch vehicle without using a nuclear
| device.
|
| If that was an accident, that means they didn't properly
| know which warheads are where. That's.... upsetting.
| kens wrote:
| That reminds me of the 2007 incident when the Air Force
| meant to transfer twelve unarmed cruise missiles from North
| Dakota to Louisiana but loaded up six nuclear-tipped
| missiles by mistake. The missiles remained unprotected on a
| B-52 for 36 hours before someone noticed the missiles were
| nuclear. A whole lot of people including 8 generals got in
| trouble over this.
|
| https://en.wikipedia.org/wiki/2007_United_States_Air_Force_
| n...
| dboreham wrote:
| Air force takes one at random, transports it to Vandenberg sans
| warhead and lights the fuse to see if it works. Or at least
| they used to. I also heard that the Soviet equivalent of this
| random testing process was to simply retarget a random missile
| and launch it straight out the operational silo.
| cpgxiii wrote:
| Strategic weapons _are_ tested regularly, except for the
| warhead. The Trident II D5 has had about 200 tests in the last
| 35 years. That 's about the same number of test missiles
| expended as are actively deployed at any given time. While
| there are a theoretical maximum of 344 deployed at any one time
| (14 _Ohio_ -class, each with 20 tubes, plus 4 _Vanguard_ -class
| with 16 tubes) some number of those boats are unarmed in refit
| at any given time.
| justin66 wrote:
| You can watch video of the most recent test, a little more than
| a month ago, of a Minuteman III. This is a short clip:
|
| https://www.youtube.com/watch?v=zUg7x1zo7D0
|
| They can test the missiles and reentry vehicles, everything
| except the nuclear warhead. The closest those come to a test is
| a supercomputer simulation, since those tests are forbidden by
| treaty.
|
| Minuteman III has an excellent but not perfect [0] failure
| rate. Some other older systems, like the UK's submarine
| launched Trident missiles... not so much.
|
| [0] https://www.airandspaceforces.com/icbm-test-failure-
| nuclear-...
| arethuza wrote:
| Th UK Trident 2 missiles are literally the same missiles used
| by the US submarines operating in the Atlantic - both sets of
| submarines are supplied by a shared pool:
|
| https://en.wikipedia.org/wiki/UGM-133_Trident_II
|
| However, the warheads on the UK missiles are designed and
| manufactured by the UK.
| justin66 wrote:
| Interesting. Are recent US missile tests at sea as bad as
| the recent UK tests? I don't remember seeing news to that
| effect.
| arethuza wrote:
| I suspect that just indicates that it wasn't just the
| missiles that were causing the failures...
| justin66 wrote:
| I had the same thought. They lovingly take Minutemen out
| of their silos and launch them after reassembly from
| Vandenburg AFB or someplace for a test. I'm pretty sure
| trident tests happen at sea.
| jonathanyc wrote:
| > The new guidance platform also added a gyrocompass under the
| alignment block, a special compass that could precisely align
| itself to North by precessing against the Earth's rotation. At
| first, the gyrocompass was used as a backup check against the
| autocollimator, but eventually the gyrocompass became the primary
| alignment. For calibration, the alignment block also includes
| electrolytic bubble levels to position the stable platform in
| known orientations with respect to local gravity.
|
| Had never heard of gyrocompasses before. I worked on a small
| robot in the past and remember having to calibrate the magnetic
| compass, which was not very accurate (similar to smartphone
| compasses). I never thought about how they'd get super precise
| headings for ICBMs.
|
| The Encyclopedia Britannica article on gyrocompasses is really
| good. Here it explains why you can't use a gyrocompass on a
| vehicle on fast aircraft (and I guess small robots that are
| jostled around a lot):
|
| > A major contribution by Schuler was the discovery that, when
| the period of oscillation is 2p[?](Earth radius/gravity), the
| heading precession of the gyroscope spin-axis due to acceleration
| is exactly the rate of change of the angle between the apparent
| and true meridians seen on a moving vehicle. The gyrocompass will
| then read true north at all times if its indicating reference is
| offset by the angle between these two meridians. The angle, at
| ship speeds, is a direct function of the north-south speed and is
| easily set into the system. The need for accurate speed
| measurement for this offset is the main reason why a gyrocompass
| is not practical for use in aircraft.
|
| https://www.britannica.com/technology/gyrocompass
|
| Love this article!
| maxglute wrote:
| What's the actual color of the yellow paint? Goldish like first
| pic of lemonish like latter pics. Contrast/aesthetics of the gold
| is just chefs kiss. There's something about American MIC pallette
| that rarely miss.
| ornateelephant wrote:
| It's the corrosion protective primer, usually containing zinc
| chromate. Colours may vary slightly but they are usually some
| shade of yellowy green.
|
| https://aviation.stackexchange.com/questions/49961/why-are-a...
| tempaway4575144 wrote:
| _The idea behind inertial navigation is to keep track of the
| missile 's position by constantly measuring its acceleration. By
| integrating the acceleration, you get the velocity. And by
| integrating the velocity, you get the position._
|
| This sounds like it couldn't possibly work (surely all the little
| errors compound?) but apparently it's how Apollo navigated
|
| https://wehackthemoon.com/tech/inertial-measurement-unit-mec...
| Zircom wrote:
| I mean it's a nuclear missile, millimeter accuracy isn't really
| necessary. Somewhere in the general vicinity is good enough for
| it's purpose of going boom.
| nox101 wrote:
| shooting something 12000 miles away, 0.1% off is 12 miles.
| That's missing the target and will not destroy whatever you
| were trying to destroy
| lazide wrote:
| In the early days, that's why nukes went into the megaton
| range. Because then 12 miles will still destroy your
| target.
|
| Then they got a lot more accurate than .1%
| kens wrote:
| Well, accuracy makes a big difference if you're trying to hit
| a hardened target like a missile silo. Missile guidance has
| been a constant effort to squeeze out more and more accuracy.
| Minuteman I started with an accuracy of 2 km, but now
| Minuteman III is said to have an accuracy of 120 meters. The
| Peacekeeper (MX) missile, no longer in service, is said to
| have an accuracy of 40 meters. You can use a much, much
| smaller warhead if you're 40 meters away compared to 2
| kilometers.
| wkat4242 wrote:
| One thing I never understood is why they phased out the
| peacemaker and not the much older minuteman.
| _djo_ wrote:
| The START II treaty limited Russia and the US's ICBMs to
| a single warhead each, and the Peacekeepers were
| optimised as a platform to host multiple independently
| targetable re-entry vehicles (MIRVs) and when the US
| agreed to revert to a single warhead per missile the
| Minuteman III was much cheaper to maintain than the
| Peacekeeper.
|
| So even though Russia withdrew from START II almost
| immediately, the US continued to unilaterally remove the
| MIRV capability from its ICBM fleet and stick to single
| warhead Minuteman IIIs.
| chickenbig wrote:
| The following was an interesting read on the super-fuze.
|
| https://thebulletin.org/2017/03/how-us-nuclear-force-
| moderni...
| mannyv wrote:
| In general, the USSR had bigger bombs because they weren't as
| accurate as US bombs. So yes.
| jonathanyc wrote:
| I also could not believe inertial navigation systems worked as
| well as they do when I first learned about them. At some point
| in time the most sophisticated IMUs were actually export-
| controlled!
|
| Maybe this has changed or is ineffective now that
| smartphone/quadcopter IMUs have caught up.
| jandrewrogers wrote:
| Advanced IMUs are still export controlled and the state-of-
| the-art is classified. The US military considers this a
| cornerstone technology and has invested heavily in R&D over
| the years. The IMUs that are widely available commercially
| have improved significantly over the years but so have the
| military versions.
| krisoft wrote:
| > Maybe this has changed or is ineffective now that
| smartphone/quadcopter IMUs have caught up.
|
| They did not caught up. There are two kind of IMUs: one where
| you have to account for the rotation of the Earth during
| signal processing and one where there is no point because it
| will be lost in the noise anyway. The smartphone/quadcoptee
| IMUs are the second kind. The first kind is still export
| controlled.
| rcxdude wrote:
| consumer-grade IMUs are still well below the performance of
| even much older military-grade IMUs (which tend to be
| impressive feats of precision engineering with pricetags to
| match, but also physically much larger). You'll still find
| anything that's useful for working out position over any time
| period is export-controlled (dual-use or stricter).
| benjam47 wrote:
| It is how Apollo navigated, although both the ground (via
| ground tracking) as well as the crew (via locating stars
| through a extant, and the Apollo computer having a database of
| the position of several dozen bright stars) could update their
| current position throughout the flight.
| embedded_hiker wrote:
| Apollo used star sightings to check the accuracy of the gyros
| that measured which way the spacecraft was pointed. The stars
| could not be used to determine position like a ship at sea
| could do.
|
| Besides inertial navigation, they had a transponder that
| would echo back a continuous pseudorandom bit stream, and the
| delay gave a precise measurement of distance.
| benjam47 wrote:
| Thank you for the correction, but are you sure that is
| accurate? I was definitely under the impression that
| although their position was normally updated by the ground
| (to the AGC, via their uplink capability), and the sextant
| was normally used to determine their orientation, the
| astronauts could use their optical equipment and
| calculations to determine their position as well as their
| orientation, albeit it with less precision. This NASA
| website (https://www.nasa.gov/history/afj/compessay.html#:~
| :text=Opti...) seems to say as much:
|
| "Optical navigation subsystem sightings of celestial bodies
| and landmarks on the Moon and Earth are used by the
| computer subsystem to determine the spacecraft's position
| and velocity and to establish proper alignment of the
| stable platform."
|
| And Wikipedia
| (https://en.m.wikipedia.org/wiki/Apollo_PGNCS):
|
| "The CM optical unit had a precision sextant (SXT) fixed to
| the IMU frame that could measure angles between stars and
| Earth or Moon landmarks or the horizon. It had two lines of
| sight, 28x magnification and a 1.8deg field of view. The
| optical unit also included a low-magnification wide field
| of view (60deg) scanning telescope (SCT) for star
| sightings. The optical unit could be used to determine CM
| position and orientation in space."
| bigiain wrote:
| The errors would be less of a problem than Apollo's, when
| your longest possible flight is only 45 minutes or so. And
| I'm not sure, but I guess the ballistic portion of the flight
| is uncontrolled (since the steering is from the rocket
| motors), so perhaps only the first few minutes are all it
| needs to maintain accuracy for?
| beerandt wrote:
| I said it downthread, but GPS is even more absurd. And we take
| it for granted.
|
| But it's based on the same idea, only getting position as a
| derivative of velocity. (And some borderline-magic statistics
| applied.)
|
| And that's before taking into account the absurdity of how low
| power the broadcast signal is.
| CamperBob2 wrote:
| GPS doesn't work that way. It uses instantaneous time-of-
| flight computation.
| beerandt wrote:
| How do you think the 'instantaneous time-of-flight'
| computation is done?
|
| There's a lot of math that phrase is hiding. It's not a
| magic black box. It just often seems that way.
| CamperBob2 wrote:
| At no point is velocity differentiated when computing a
| GPS fix. (Or integrated, which may be what you meant.)
|
| Your point stands, though... the way it _does_ work is
| pretty much indistinguishable from magic, from a 1970s
| perspective. Those guys were wizards.
| rx_tx wrote:
| If you want to understand GPS more,
| https://ciechanow.ski/gps/ is always an amazing read,
| witchcraft confirmed.
| HPsquared wrote:
| Isn't it about finding the time difference between
| pseudorandom coded signals. Granted the satellite
| positions and paths need to be known, which is another
| part of the puzzle. That involves some calculus, I'm
| sure.
| beerandt wrote:
| Yes but measuring diffs in either the pseudocode itself
| or the underlying carrier wave is basically measuring
| relative velocities wrt each sat and the observer.
|
| It's all summing dx/dt + dy/dt + dz/dt, for i paths
| between satellites and ground stations (or more receivers
| for differential or rtk or vrs style). [2]
|
| Which reduces most of the time to summing DELTA-Xi +
| DELTA-Yi + DELTA-Zi + delta-t(timeerrors). For i paths
| between each sat and ground receiver.
|
| Which you should recognize the transformation if you've
| ever taken calculus. Even if you don't integrate every
| time you get a fix.
|
| Part of what I describe as math 'magic' is that you can
| cancel out most of the unknowns and most of the unsolved
| calculus if you add a second fixed receiver.
|
| Google and Apple location services 'cheat' and do this
| via subbing a nearby wifi MAC with known coordinates,
| which for them is good-enough. But augmented gps from FAA
| or DOT or coastguard etc work the same way, but with real
| gps receivers on the ground in realtime. Obviously
| without having to substitute anything.
|
| Either way- the extra known variable greatly simplifies
| the math via canceling-out terms.
|
| Plus there are both closed and open form solutions
| developed since initial GPS deployment that allow solving
| without direct integration.
|
| Chapter 12 of [0] Surveying gets into the math, including
| transformations, if you want to see the math details.
|
| Or [1] GPS by van Sickle for a good overview of the
| various methods/ technologies. (Also survey-centric).
|
| [0]https://books.google.com/books/about/Surveying_theory_
| and_pr...
|
| [1]https://books.google.com/books?id=J0fLBQAAQBAJ&pg=PA63
| &sourc...
|
| [2] despite wgs84 and lat/lon being associated as default
| 'GPS coordinates', the 'raw' gps system data is xyz
| Cartesian in feet, then transformed to lat lon or
| whatever else.
| HPsquared wrote:
| My assumption was that GPS doesn't use dead reckoning to
| get a fix (other than the satellite paths). Do receivers
| use the Doppler effect to directly measure velocity?
|
| Edit: this article seems to support my view that they
| don't start with velocities: https://insidegnss.com/wp-
| content/uploads/2018/01/marapr15-S... "How does a GNSS
| receiver estimate velocity?"
| KK7NIL wrote:
| > surely all the little errors compound?
|
| Random errors (i.e. noise) cancel out in the long run thanks to
| integration. You're then only left with systematic offset
| errors which can presumably be calibrated out to a large
| extent.
| petermcneeley wrote:
| Really depends on what you mean by random. If it is truly
| random then you will end up with a random walk.
|
| https://en.wikipedia.org/wiki/Random_walk
| KK7NIL wrote:
| We can assume the error will have a random (whether it's
| actually truly random or merely pseudo-random doesn't
| matter here, just assume it's indistinguishable from truly
| random for this discussion) and a non-random component.
|
| The random component I assume to be gaussian (thermal
| noise, for example) and therefore symmetrical around the
| real value. It's obvious we can remove this type of noise
| through averaging (of which the core operation is
| integration).
|
| The non-random component I assume to be a skew that can be
| calibrated out.
|
| With these two assumptions in mind you can see that yes,
| it's indeed a random walk, but a very well behaved one.
| kens wrote:
| No, you can't remove the random walk error by
| integrating. The point is that after integrating, what
| you're left with the random walk error. To make this
| concrete, if you buy a commercial-grade gyroscope for
| $10, it will have a random walk error of several o/[?]h.
| So after summing the errors for an hour, you're left with
| several degrees of random error, which is bad. If you
| spend $100,000 on a navigation-grade gyroscope, you'll
| get a random walk error < 0.002o/[?]h, which is much
| better.
|
| As far as calibrating out the skew, of course you can do
| that to some extent, but it's not a magic bullet. The
| Minuteman periodically measures skew and even applies
| equations for the change in skew with acceleration. The
| problem is that skew is not constant; it changes with
| time, changes with temperature, changes with position,
| and changes randomly, so you can't just calibrate it out.
| That's one reason why missiles use strategic-grade IMUs
| for a million dollars rather than a commercial-grade gyro
| for $10: you're getting drift of .0001o/hour instead of
| .1o/second.
| KK7NIL wrote:
| You are correct, I forgot to separate between long-term
| and short-term random effects.
|
| Short-term random effects (as in, the part of the gyro's
| random walk error significantly higher in frequency than
| the inverse of the integration period) will get cancelled
| out by integration, assuming they're Gaussian.
|
| Long-term random effects (mainly from time and
| temperature like you mentioned) will instead tend
| accumulate with integration aka worsening with time.
|
| P.S. great fan of your many ventures into retro tech,
| keep them coming!
| kragen wrote:
| that was not what you forgot and your summary is still
| wrong. kens is correct. i suggest programming some simple
| simulations using a random number generator to get a
| better feel for the space
| KK7NIL wrote:
| Would you like to expand on what I missed and how my
| summary is still wrong? Genuinely asking.
| kens wrote:
| One can't cancel out random errors by integrating. You
| should take kragen's suggestion and write a quick
| simulation. To make this concrete, flip a coin 10 times.
| Take a step to the left for heads and a step to the right
| for tails. Most of the time you won't end up where you
| started, i.e. you have residual error.
| KK7NIL wrote:
| > One can't cancel out random errors by integrating.
|
| An ideal integrator has a response of 1/s. That's just a
| 1st order low-pass filter with the pole at 0. Therefore,
| it will filter out high frequency noise.
|
| > Take a step to the left for heads and a step to the
| right for tails. Most of the time you won't end up where
| you started, i.e. you have residual error.
|
| I wrote a quick simulation based on your suggestion [1].
| Started by generating 1e6 random points and then applied
| a high-pass filter. Calculated the cumulative sum on both
| the original and the filtered version. TL;DR: filtered
| version has small and very fast variations but doesn't
| feature the much larger amplitude swings seen in the
| original.
|
| Integration indeed does not help for those large slow
| swings (I'd call it drift in case of a gyroscope), but
| that's what I was trying to get at when I started to
| distinguish between short and long term random effects.
| What I was trying to get across originally is that "all
| the little errors" (which I read to mean tiny fast
| variations, forgetting that drift is a much bigger issue
| in gyroscopes) which OP mentioned get filtered/canceled
| out. I totally missed to explain that this will vary with
| frequency, which was my bad.
|
| [1] https://github.com/afonsotrepa/noise-sim/tree/master
| kragen wrote:
| yes! but also keep in mind that 1/ _s_ is never 0 for any
| finite _s_ , so even at high frequencies the error
| resulting from random noise is never zero, it's just
| strongly attenuated
| KK7NIL wrote:
| That's right but "the Bode plot of an integrator is a
| line with a -20 dB/decade slope" doesn't really roll off
| the tongue ;)
| kragen wrote:
| it's implicit in this comment by kens though:
|
| > _if you buy a commercial-grade gyroscope for [us]$10,
| it will have a random walk error of several o /[?]h. So
| after summing the errors for an hour, you're left with
| several degrees of random error, which is bad. If you
| spend [us]$100,000 on a navigation-grade gyroscope,
| you'll get a random walk error < 0.002o/[?]h, which is
| much better._
|
| if the slope was anything else, the unit of deg/[?]h
| wouldn't make sense; it would have to be deg/h or
| deg/[?]h or something. similarly for noise figures given
| in nanovolts/[?]Hz
| rcxdude wrote:
| try it: take gaussian white noise with zero mean and
| integrate it twice. You'll see the signal does not stay
| close to zero, in fact it will drift arbitrarily far away
| from it over time (it's only necessary to integrate once
| for this to be true, but doing it twice as an IMU needs
| to will make it more obvious).
| KK7NIL wrote:
| You are correct, I initially did not explicitly separate
| the noise according to its frequency (my mistake).
| Integration only helps with high frequency error and can
| actually worsen low frequency error, more details in my
| second reply to kens.
| jfoutz wrote:
| When the MacBook got the acceleration sensor, I hacked up a
| little program to estimate velocity, and a button to reset at
| stoplights. Some friends drove me around, it worked poorly. it
| did pretty ok on the highway, but awful in the city.
|
| I think if I kept messing with it, it'd get a lot better, but I
| sorta lost interest. This was more of a fun weekend toy.
|
| I think all phones have them, and they might be reachable
| through chrome/safari. And it is kinda fun to play with, but
| you'll probably hit sampling rate errors pretty quick. you
| gotta guess the shape of the curve between datapoints.
| ghaff wrote:
| At least modern ICBMs do a star sight to calibrate at the top
| of their trajectory but, yes, that's what inertial guidance is.
| Draper Labs basically pioneered.
| jojobas wrote:
| It's far from the top of their trajectory (by then the
| warheads are long separated), and only submarine-launched
| missiles need it.
| ghaff wrote:
| Ah. I'm only somewhat familiar with Trident.
| kevin_thibedeau wrote:
| That is how all self-guided weapons systems worked before GPS
| was viable. Many still retain that capability as a fallback.
| Notably, the Tomahawks fired during Desert Storm had to transit
| over Iranian airspace because they needed the mountainous
| terrain to correct for their inertial drift before turning
| toward their targets over the flat Iraqi plains.
|
| https://en.wikipedia.org/wiki/TERCOM
| lupusreal wrote:
| Almost all. Walleye television-guided glide bombs used edge
| detection on a television signal to aim themselves in. A
| human would designate a target at the start but then the bomb
| would autonomously track the target. An optical fire-and-
| forget system developed in the 1960s.
|
| Sidewinders are another example. Both developed at China
| Lake.
| flavius29663 wrote:
| > before GPS was viable
|
| GPS can be jammed (see Russia-UKraine war), so inertial
| systems are still very important for rockets, for example
| some HIMARS rockets start with GPS and then rely only on
| inertial while getting close to target.
| missedthecue wrote:
| Himars relies on inertial navigation the entire flight and
| uses GPS updates to course correct. If the GPS is blocked
| for a sufficient amount of flightime, even with the
| intertial navigation, the accuracy can become unusably low.
|
| This is how the Russians have been throwing double digit
| percentages of launches off course.
| ethbr1 wrote:
| Terminal guidance since ~1995 on higher-end weapons has
| switched to hybrid inertial + scene matching (various
| sensor types).
|
| F.ex. the 90s Tomahawk used terrain contour matching to
| orient itself
|
| For more details see
| https://apps.dtic.mil/sti/tr/pdf/ADA315439.pdf (US
| translation of a mid-90s Chinese survey of the guidance
| space, but it covers the material and is publicly
| available)
|
| Afaik, most modern systems use infrared target matching
| for final course correction. (Initially developed to
| allow anti-shipping missiles to autonomously prioritize
| targets, but now advanced enough to use in land scenarios
| as well)
| mrguyorama wrote:
| I don't think ATACMS or GMLRS missiles have any terminal
| guidance apart from their aim point. The GMLRS missiles
| that carry german SMART munitions do, technically, since
| the SMART munition has it's own targeting system.
|
| It wouldn't make much sense to me, as most ATACMS
| warheads are area based, not point target based, so they
| wouldn't expect to aim at a single target. Also these
| systems are relatively cheap compared to things that DO
| have such guidance
| ethbr1 wrote:
| They don't and are definitely at the dumb/cheap end of
| the scale. (or in ATACMS' case, dumb/big)
|
| I think anything developed before ~2005 that wasn't
| explicitly anti-ship doesn't have terminal guidance.
| Cruise missiles maybe/not.
|
| Things after (e.g. SBD2 / StormBreaker) started to,
| because components were finally cheap and mature enough
| during the development cycle.
| missedthecue wrote:
| Only cruise missile have tercom. Himars and Excalibur do
| not have any camera or terrain matching system
| dingaling wrote:
| The little errors do compound, but the errors have been made
| progressively littler; a modern ring-laser gyro INS has a drift
| of one millidegree per hour or less.
|
| Or you can add an external correcting factor, such the
| Trident's astronav system that takes star-shots to recalibrate
| the INS.
| ddalex wrote:
| When Nintendo Wii motes first appeared, they were some of the
| few devices at the time with cheap MESM accelerometers and
| gyroscopes that were programmer-friendly.
|
| I remember taping two together back to back and integrating
| acceleration across them. That's when I learned Kalman filters.
| It was accurate enough so I could throw it across my desk and
| measure the desk length :)
| JR1427 wrote:
| See https://news.ycombinator.com/item?id=40692333
| rjsw wrote:
| Operation Black Buck [1] used inertial navigation.
|
| [1] https://en.wikipedia.org/wiki/Operation_Black_Buck
| spoonfeeder006 wrote:
| Interesting tech and all, but ultimately efforts like this are a
| waste. If we humans could instead get over our self-perceived
| need to engage in warfare for childish reasons then we could
| dedicate such efforts to more productive things like helping
| homeless people get housing and skills, or developing better
| psychological sciences to help drug addicts get free from their
| disease of addiction, you name it
|
| > O SON OF SPIRIT! The best beloved of all things in My sight is
| Justice; turn not away therefrom if thou desirest Me, and neglect
| it not that I may confide in thee. By its aid thou shalt see with
| thine own eyes and not through the eyes of others, and shalt know
| of thine own knowledge and not through the knowledge of thy
| neighbor. Ponder this in thy heart; how it behooveth thee to be.
| Verily justice is My gift to thee and the sign of My loving-
| kindness. Set it then before thine eyes. > > ~ Baha'i Teaching
| CamperBob2 wrote:
| It would be great if we could all share that sentiment. But ask
| the Ukrainians how unilateral disarmament worked out for them.
| Unfortunately, it seems that this particular waste of resources
| and intellect is still necessary.
| spoonfeeder006 wrote:
| Sorry, I don't mean anything against legitimate self defense,
| I'm talking rather about "self-perceived need to engage in
| warfare for childish reasons"
|
| Examples of that would include ego, greed, petty revenge,
| etc...
|
| But I guess the way I said it did come across that way, so
| yeah, my bad
|
| I'm just saying that if we could evolve past such petty ego-
| based sentiments in the world, then wouldn't such pressure to
| develop weaponry in such massive amounts, and hence we could
| focus on actually making a functioning society
| shiroiushi wrote:
| >I'm just saying that if we could evolve past such petty
| ego-based sentiments in the world
|
| That would be nice, but it seems that would make people no
| longer human. Happily following a petty ego-based Dear
| Leader's orders into warfare seems to be the norm for much
| of the human population, looking at history, so this
| tendency appears to be deeply-rooted into the human psyche.
| lloeki wrote:
| Not just humans, apes at large.
|
| https://en.m.wikipedia.org/wiki/Gombe_Chimpanzee_War
|
| Cue the opening scene of 2001 A Space Odyssey.
| em-bee wrote:
| why? the majority of humans are peaceful and friendly.
| the problem is that we have been raised to follow leaders
| instead of thinking for ourselves. that is what needs to
| change. when people learn to think for themselves then we
| won't have that problem anymore.
|
| as the quote above says:
|
| _thou shalt see with thine own eyes and not through the
| eyes of others, and shalt know of thine own knowledge and
| not through the knowledge of thy neighbor_
|
| it all comes down to better education, specifically moral
| education, and learning to critically evaluate any
| information we get.
|
| if people blindly follow a leader, then this is exactly
| what they are missing.
| CamperBob2 wrote:
| So, the problem with that is that not everybody is
| equally good at "thinking for themselves." A
| sufficiently-large group of people will always divide
| itself, as inevitably as if Maxwell's Demon himself were
| prodding them, into subsets of people who can be easily
| herded and people who can't be. By the same token there
| will always be a small minority, drawn from both subsets,
| who are unusually good at doing the herding.
|
| Everything that goes wrong later can be traced to that
| inequality. Things that go right can usually be traced
| back to it as well. Any faith or philosophy that doesn't
| begin with an understanding of that aspect of human
| nature is a waste of time at best. Thank you for coming
| to my TED talk.
| spoonfeeder006 wrote:
| > not everybody is equally good at "thinking for
| themselves." A sufficiently-large group of people will
| always divide itself, as inevitably as if Maxwell's Demon
| himself were prodding them
|
| true, but perhaps we do have capacity to learn to think
| well enough to pick leaders who are better people than
| the most of us overall, e.g. learning to not mistake
| charisma for pure intention or intellectual insight
|
| with some self awareness, it takes less effort overall to
| know who is better than us or our friends in terms of
| ethics and intellect, than it is to be right on every
| issue
|
| and thats probably more important than the specifics of
| each issue, especially since the lay person doesn't have
| time to delve into the finer details of everything
|
| now if we can get in a cycle of electing leaders like
| that then that would set us on a trajectory of constant
| societal growth, but to get to that our system probably
| also needs to change so as to actually present people
| with realistic options
|
| that is probably a lot harder, and the two are certainly
| locked into a feedback loop
|
| and I don't have answers on that one, but I believe if
| its possible to get to where we are from pond scum, then
| perhaps we can get to that point in the future as well
| spoonfeeder006 wrote:
| > O rulers of the earth! Be reconciled among yourselves, that
| ye may need no more armaments save in a measure to safeguard
| your territories and dominions. Beware lest ye disregard the
| counsel of the All-Knowing, the Faithful.
|
| > Be united, O kings of the earth, for thereby will the
| tempest of discord be stilled amongst you, and your peoples
| find rest, if ye be of them that comprehend. Should any one
| among you take up arms against another, rise ye all against
| him, for this is naught but manifest justice.
|
| > ("Gleanings from the Writings of Baha'u'llah", pp. 253-254)
| ThinkBeat wrote:
| How did you reprogram the destination on the missiles?
| kens wrote:
| It depends. For Minuteman I, the missile needed to be
| physically rotated in the silo to be aligned with the target.
| Then the "Targeting Van" connected to the missile, downloaded
| the new targeting data to the disk, and checked that the
| guidance system was aligned. As for the targeting data, it was
| generated by a mainframe that determined the right trajectory
| and produced the optimized navigation polynomials that the
| targeting algorithm used. It was something like 740 words of
| data per target so only two targets could fit in the computer.
|
| Minuteman III used a smarter targeting algorithm that only
| needed 70 words of data per target, so the missile could
| support something like 8 targets at once, selected by a knob on
| the launch console. (The launch officers didn't know what the
| targets were; they were just told to use target #3 for
| example.) The targeting data was read off punched tape for
| Minuteman II and a magnetic tape cartridge for Minuteman III.
| beerandt wrote:
| It was organized primarily via wargame scenarios, such that
| one target group comprised targets for a given scenario.
|
| Simplified launch orders via the football, etc.
|
| One group scenario might have been silo coordinates for an
| offensive first-strike. One group city coordinates for launch
| on warning strategic counter-strike, etc.
|
| Each missile got a target from each scenario list programmed
| into a 'memory slot' with some overlap.
|
| The organization/ optimization is mind-boggling.
|
| But few understand that this is WHY the wargames and strikes
| had to be pre-planned ahead of time. It wasn't political
| hubris, but a technical requirement due to memory allocation.
| krisoft wrote:
| > It wasn't political hubris, but a technical requirement
| due to memory allocation.
|
| I don't understand why it would be "political hubris".
|
| Proper targeting is hard work. You need to map your enemy
| territory to make optimal choices. Not just in a
| geographical "what are the coordinates" sense, but also in
| a "what are the important nodes to get the coordinates for"
| sense. At the same time your enemy doesn't want to be
| mapped and resists your efforts.
|
| Doing this properly takes time. On the order of months. But
| once you are under attack you don't have that time. So you
| have to select your targets ahead of time.
|
| It is not because the missiles have limited memory. If they
| would have needed more memory they would have added more
| memory. It is because the President doesn't have time once
| under attack to name each enemy railway depot one by one
| and decide which ones are important, and which ones are
| better left unharmed. Instead what they have is a menu of
| options. Something like option 1 destroy all red military
| ports, military airports and military bases; option 2
| destroy major military installations plus main industrial
| centers; option 3 destroy main population centers.
|
| Thinking that the memory allocation is why it is the way it
| is is super tech centered and quite frankly putting the
| cart before the horse.
| ThinkBeat wrote:
| One of the great things about chemical propulsion rockets is that
| they can take off with little to no prep at all. Ready to go at
| the press of a button.
|
| The scary thing is that, when left alone for a long time, and
| these rockets have been, "the plates" keeping the chemicals from
| meeting each other ahead of schedule, corrodes, just a tiny bit
| at a time. each time raising the possibility of premature
| ejaculation just a tiny little fraction.
| kens wrote:
| I think you're talking about the Titan missiles, which use
| hypergolic propellants. The Minuteman missiles are solid fuel,
| so there are no separated chemicals.
| beerandt wrote:
| There are separated chemicals, the hypergolic means no
| ignition source required.
|
| Which to his point would be even more scary, but just isn't
| the actual real world risk with the way the things were
| designed.
|
| Plus hypergolics are usually toxic on their own, even without
| mixing and/or booming, in a quieter, more-deadly-to-
| technicians way.
|
| Spills and defueling and meeting well-intentioned but bad
| safety guidelines that require abundant fiddling were the
| real source of danger. More fiddling == bad.
|
| Iirc, the fuels/oxidizers/reagents/ whatever-liquids mainly
| behaved like aluminum oxidizing, such that reaction with the
| tanks components actually created an increased buffer layer
| of oxidation/ protection.
|
| Tank corrosion wasn't high on the list of risks after it was
| figured out on a per-chemical basis.
|
| I think it's one of the aspects covered fairly well in (the
| great, often posted) Ignition! [0]
|
| [0]https://archive.org/details/ignition_201612
| krisoft wrote:
| There is a bit of a misunderstanding here.
|
| The minuteman missiles are solid fueled. There are no
| liquids and no hypergolics involved in the stages which
| loft it towards the enemy. Structurally it is more similar
| to a candle than a fuel tank. There are no spills or
| defueling with this system. This is a fact. In this system
| you won't find a separate oxidiser/fuel. The two components
| are mixed together and they form a kind of rubber like
| cylinder with a hole in the middle. The hole is shaped
| appropriately so the rocket engine burns at the right
| rates.
|
| There are hypergolic fuels at the very end of the rocket in
| the payload. They are used for deorbiting and to control
| the return vehicles. But it is a much smaller part of the
| whole missile. (Both by mass, and by encapsulated energy.)
| beerandt wrote:
| Yes I was speaking to the historically overblown concern
| of fuel and oxidizer tank corrosion, which yes, does not
| even apply to minuteman or solid fuels.
|
| Should have prefaced that response with a big IFF/WHEN
| old liquid rockets.
| ThinkBeat wrote:
| A cheerful thought is that according to atomic scientists the
| world is closer to nuclear holocaust now, than we have ever been.
|
| The future so bright, I gotta wear shades.
|
| https://thebulletin.org/doomsday-clock/current-time/
| IamTC wrote:
| I believe parts of the subsea industry uses a similar concept,
| i.e., gyroscope based for inertial navigation.
|
| Obtaining position & veocity: I think it even more interesting
| when one compares the difficulties of getting these fundamental
| navigation data in an aerial, ground and undersea platforms.
| aussieguy1234 wrote:
| So. The world could be blown up with just 8kb of memory. No need
| for a killer AI with hundreds of GB's of vram.
| artemonster wrote:
| A testament to human ingenuity and genius, work of art even. The
| machined parts, the crude electronics, all of it
| LarsDu88 wrote:
| So much discrete circuitry and now any bum can get the same
| performance from a 15 year arduino
| N_A_T_E wrote:
| Wow, so this thing needs to be pointed directly at the target
| 8,000 miles away and will miss the target by the amount of error
| in aim.
|
| "To target a Minuteman I missile, the missile had to be
| physically rotated in the silo to be aligned with the target, an
| angle called the launch azimuth. This angle had to be extremely
| precise, since even a tiny angle error will be greatly magnified
| over the missile's journey. " ... "The guidance platform was
| completely redesigned for Minuteman II and III, eliminating the
| time-consuming alignment that Minuteman I required. The new
| platform had an alignment block with rotating mirrors. Instead of
| rotating the missile, the autocollimator remained fixed in the
| East position and the mirror (and thus the stable platform) was
| rotated to the desired launch azimuth. "
| ianbicking wrote:
| I noticed that too. That seemed odd at first read... after all,
| it has a guidance system, it's not relying on exact aim. I'm
| assuming it's more that its guidance system can only has so
| much fuel at its disposal and ability to correct errors, and if
| it's aimed incorrectly it would exhaust its fuel before it
| corrects its trajectory.
| ethbr1 wrote:
| Sometimes it's less work to engineer a hard problem into an
| easy one, than to solve the hard problem.
|
| Most of the tech for the Minuteman I was developed in the
| mid-1950s.
|
| With that level of processing, would you rather solve a 2d
| problem by precisely orienting the missile before launch? Or
| a 3d one by requiring it to orient during flight?
|
| Keep in mind: any equipment to self-orient in-flight also
| needs to be carried on the missile itself, while being
| tolerant of launch, acceleration, and reentry forces.
|
| Any precision machinery at the launch site has no such
| requirements.
| aeonik wrote:
| This doesn't make sense to me. I would assume the engines
| starting by themselves would introduce enough error to
| throw the entire system off. Let alone natural seismic
| events in the ground, plus wind.
|
| I would guess you must solve the 3D problem at least to
| some degree.
| ethbr1 wrote:
| I'm not a rocket scientist, but I think thrust is pretty
| constant at that scale. That's why they start, spool up,
| then release from cradle.
|
| Vs something like a Polaris SLBM that has a much more
| variable guidance problem
|
| It'd be curious to see how early ICBM and SLBM guidance
| systems differ.
| kens wrote:
| I haven't looked at submarine systems in detail, but my
| understanding is that the big problem is that an ICBM
| knows where it's starting, but the submarine travels. So
| submarines have super-accurate inertial navigation
| systems on board to determine their position.
| ecshafer wrote:
| Shooting a projectile, accounting for the earths rotation and
| wind, is essentially a solved problem (with computers). So I
| don't think this is that outlandish and I imagine it gets
| pretty accurate. Creating an analytical solution by hand is a
| junior level physics problem.
| kens wrote:
| There are two factors. First, any missile with inertial
| guidance needs to have a precise angle reference as a basis for
| the guidance system. If the guidance system starts off slightly
| wrong about which way is North, it's going to miss the target.
| Second, the guidance system in Minuteman I could only turn
| about 10 degrees from its initial angle before the wires would
| get tangled up. The solution in Minuteman I was to use the
| launch azimuth as the reference angle, so it was precisely
| lined up against this angle. Most of the alignment was
| physically rotating the missile, but the last bit of alignment
| was by constantly rotating the stable platform for alignment
| with the light beam from the autocollimator.
| datavirtue wrote:
| Purely a deterrent. No one in their right mind would try to
| launch these expecting them to hit their target.
| somat wrote:
| There is a well written video essay on the inner workings of the
| d-17 computer used on the minuteman 1
|
| Minuteman D-17b: The Desktop Computer Was Born in an ICBM
|
| https://www.youtube.com/watch?v=MJPnZzZtswc (Alexander the ok)
| mrguyorama wrote:
| This is Youtuber has had several very well researched and
| thorough videos about topics that readers of Ken would enjoy,
| including Buran, the F-14 Air data computer, Elite, and the
| birth of Digital fly by wire out of the Apollo program.
|
| Check him out and give him slack for his vocal fry. It's mildly
| annoying but the content is just so good.
___________________________________________________________________
(page generated 2024-08-20 23:02 UTC)