Great video. Almost all INS systems now are a strapdown system with laser gyros and gimbal system the moveable part has been replaced with light. Two beams in opposite directions about a single axis rotation is measured by the time difference to a central point on a mirror. 3 gyroscopes in each axis are now used. Accelerometers function as before. Next video could explain this better than I can here
Thanks for the info. But I heard that modern aircraft still need time to start and calibrate the gyroscope every time the plane going to start. Is that still true ? And why the modern INS (with laser/light) still need that ?
Hello! This video is targeted towards people who are trying to learn about INS systems for the first time, so to keep it digestible I decided to leave out some details. Here's a quick summary of things that didn't make it in: - 03:16 Fun fact: in 1714 the Longitude Act was passed by the Government of Great Britain to develop a sufficiently accurate clock for maritime navigation. - 04:15 The real LN-3 had four gimbals instead of three to prevent a phenomenon called "gimbal lock". This happens when two of the rotational axis align, constraining the system to rotate in only two of the three dimensions. - 06:15 Using acceleration to determine your position is an entire topic in itself, called integration of position. The maths behind it is actually quite simple, and computers can do these calculations extremely fast. Like the sailor example, INS systems need to know where they start off from before they can start this process. - 08:04 The same "tilting" problem whereby gravity influences the measurement of accelerometers also applies to roll and yaw. That's why we need all three gimbals. - 09:58 Although accelerometers do not directly measure position and velocity, these can be calculated (or integrated) by using the acceleration. Like all other instruments, accelerometers are imperfect and will inevitably measure an error which will accumulate over time (due to dead reckoning). - 10:02 Similar to the previous point, gyroscopes will also build up an error over time due to gyroscopic precession and the friction of the gimbals. To correct the gyros for transport wander and apparent drift, this same phenomenon is used to apply torques to rotate the gyroscopes according to the spin of the earth and velocity of the aircraft. - 10:23 In reality, due to the accumulation of errors the platform *will* actually measure a small component of gravity. The reason this does not get out of hand is due to the feedback loops, which will cause the platform to oscillate as a "Schuler pendulum" (wobble back and forth around the centre of the Earth). - 10:36 Due to the previous points, over time INS systems will build up an error despite the feedback loops. They are therefore periodically updated by other navigation systems such as GPS or VOR. I mention that INS systems keep the platform level with the horizon, technically this is not true (thanks Ken Watanabe). They keep the platform level with the local horizontal plane, since the horizon could in theory depend on mountains/terrain. The point is that the platform stays level, perpendicular to the direction of gravity. Finally, these days aircraft no longer use moving-platforms but correct for gravity using maths in a computer, although the principle is the same. These types of systems are called "analytic platforms" since the computer basically uses a virtual platform instead of a real one. Another name for them is strapdown INS systems, since I guess they can be directly "strapped" to the aircraft without the need for gimbals. These more modern variants use ring laser gyroscopes, but rely on the same concepts introduced in this video. If I missed anything or made a mistake, definitely let me know. Thanks!
Seriously, would it have killed you to mention gimbal lock? The fourth gimbal is extremely important. The first systems only had three. But there was a dog fighting maneuver taught to F-4 pilots in Vietnam that locked up the platform every time. Was never a problem until then. And it was funny that you showed a video of an A-10 which didn't have INS until the mid '80s, 10 years after the first aircraft were delivered to the USAF. The rumor is they came with East German road maps. And there was no other system in the old days that could update the INS. We used a thing known as a waypoint. You'd type in the latitude and longitude of a known landmark and tell the system to update when you flew over it. And something else, the gyroscopes do not align directly with the poles and equator. The original systems did and were severely erroneous when going above 72 degrees north or below 72 degrees south because of the converging lines of longitude. But you didn't even mention how gyroscopes precess until they find the earth's rotational axis. The platform actually orients itself to local level, not the horizon. The horizon changes with altitude, local level doesn't. It does this using the accelerometers when the aircraft is sitting still during system warm up. I learned how to dead reckon in AFJROTC in high school. The process and computations performed by an INS are completely different. I used to be in the Air Force. Yep. I maintained the INS on the A-10 at Davis Montham AFB. My original job title was Avionic Inertial and Radar Navigation Systems Specialist. Then the Air Force reconfigured some specialties in the late '80s and I became Avionics Guidance and Control Systems Specialist.
Perhaps a explanation of the more modern AHRS (attitude heading reference system) would be a nice add on. In my modern aircraft, we have 3 laser ring gyros as back up. The primary source for navigation is GPS first, then IRS. GPS is almost a replacement for ground based aircraft navigation, including landing in fowl weather. Although for the lowest landing minimums, 200ft or lower, ground based systems are required.
I was an Avionics technician and Loadmaster on C-130 aircraft for both the Marine Corps and Air Force, and this beautifully explains how INS systems work.
Then could you please explain, how in real hardware the compensation realy work, by moving around the Earth. Other vlogers show, that there must be two electrolytic tilt sensors, to hold the platform with two gyroscopes steady horyzontally to Earth surface. Is it right?
I was an Inertial Navigation (and Radar) Avionics Tech from 1979-1983 on the USAF F-111. The INS was an 80+ pound, 2ft x 2 ft box when removed from the aircraft for testing in our shop, thus required 2 persons to lift and mount onto the test equipment. Parts had to be replaced and calibrated routinely for optimal performance.
Sounds like the old ASN84 we had prior to upgrading to LTN72.They took longer to align and quite often required a lot manipulation to get them up and keep them running. Stell shots were a must do, though we still had Omega.
Thats pretty neat man... It's remarkable how small INS systems has got by comparison. I work avionics on F-35s, and now its just a tiny little white composite box you can hold in a single hand. It's pretty impressive too, It will have virtually zero drift even without any GPS fix being provided for a good 30 or 45 minutes. Not bad for degraded operation lol
My dad did a lot of this when I was a kid. He didn't actually design the inertial navigation systems, he was responsible for testing and verifying them. He would talk about "gimble lock", warplanes feeding their guidance information to the ordinance, and doing star sightings from a moving plane to check the gyros. I believe they also had a physical test stand that consisted of concrete set deep into the earth. When the ring laser gyros took over, nobody knew how to make them. They would manufacture like 100 and test them all in hopes of getting one that actually worked.
Scott, your dad and my uncle probably worked very closely on this together. my uncle was heavily involved in this science and remained with it being called back to fix some issues with the cruise missile. what an exciting device to work on!
@@dysfunctional_vet The plant my dad worked at was in Little Falls, NJ. The company went through different mergers and whatnot but he worked for Singer or Kearfott at the time. Once a year they would have an open house and us kids would get to tour the plant. They also did lots of other cool family stuff that you don't see today. My clearest memory of the plant was the giant centrifuge. We also got reams of test results on tractor feed printer paper that we would take home and color on the back of.
I'm a Pilot and during theory training, we studied INS/IRS in great depth. This videos is an amazing introduction to such a system and I wish we used this video in class. Kudos for such a master explanation!!
Outstanding work. I can easily see the hidden hours of research, animation, and production that went into this video. Also, teaching in a clear and comprehensible level takes a master. Well done sir.
Thanks for showing the video. It brings back old memories. It appears to be the Litton LN3 Inertial Platform. I started my Aerospace career at Litton back in the early sixties as QA Inspector in the LN3 lab. A beautiful instrument and quite accurate for an early 1960's piece of navigation equipment. Well done!
I recently had a tour at the Litton (now Northrop Grumman) site in Woodland Hills, CA. They showed us everything they were working on. I'll definitely say, these guys are geniuses, and I'm glad to be working with them. They're constantly innovating and coming up with new tech.
You have to program the time day and month and year for the unit to know where it's at as the small telescope that reads star light during the day or night.
I worked with inertial navigation on Submarines. The saying was a multimillion dollar device that you tell it where it is and it will tell you where you are. The initial position is everything.
Very interesting. I actually build part of these inertial guidance systems back in the mid 1960’s. I worked for Litton Systems just outside Toronto. Very fine work under microscope and a lot of assembly was done in “clean rooms” where the air inside was filtered. Anyone working inside that area had to wear special clothes that went over all your street clothes including your shoes. Only your face was exposed. The fingers on your hands were covered in finger cots, they looked like miniature prophylactics. If you had a cold or were sneezing you weren’t allowed to go into that area. The tolerances on the gyros were so tight a piece of dandruff could gum up the works. Lots of inspections done on this work.
Sir, that’s absolutely fascinating. Lord knows my notifications for TH-cam are all sorts of outta wack, but I’d appreciate any more info or stories you have from your time there, or in related fields. As someone who loves American history and 20th century history (especially postwar) - the amount of mundane people one can meet now in person or online is wild. All these stories hardware and vehicles, and those who had hands-on day to day such as yourself are here and around to speak about it.
@@yeetyateyote5570 , I only worked at Litton Systems for about 13 months. I mostly worked on what was called the end bell which underneath the round end of the gyro. The metal was anodized aluminum. There were holes drilled for very tiny electrical contacts all around the circumference. We had to glue in tiny literally gold coated contacts into these holes withe special adhesive. I believe the tube was called LC 9. They were kept in a freezer. We had to sign each tube out and they were only good to use for 30 minutes. We used a tiny applicator to put about a 90% circle around the gold contact which was imbedded in a glass insulator. This work was done under a 10x power microscope. We had to place the contact into the hole and not get any of the glue onto the side on the way down. These end bells were placed into small autoclaves to cure the glue. I forget how many contacts were on each bell. We had rubber coated trays that held 5 end bells. We were expected to do I think 30 per week. Not big pay, only around $1.15 hourly in ‘64. All of these end bells were inspected to ensure there was no glue on the side of the walls. After curing a clear sealant was put onto each contact and it was cured too. If you had any rejected you had to clean it all up and re submit it for inspection. I was pre darn good after getting a few rejections at first. Being more precise was better than cleaning up.
@@rickbullock4331 That’s fascinating. I got my pilot’s license in 1992, but never used ILS because my family owned many FPO that my grandfather (an early adopter of personal aircraft) had founded during the time many airports were being built. I’m shocked when this video says that a gyro will need correction due to changing gravity. Although it was never discussed, I assumed that a gyro would adjust to local gravity and always stay exactly positioned as it was started in reference to L&L. If I took off from Lubbock to Honolulu, I assumed old ILS was flattening out as I flew- in relation to the starting position. How did I miss this all these years? LOL I never learned ILS or even continued flying fixed wing, as I knew 30 years ago that we had employees that would always be better at it than me. My thing is exotic cars and guns. I figured I would live longer if I let the guys who were passionate about flying to the flying. I’ll drive the race cars once we get there and make my money with guns. BEST WISHES. Nick
@@rickbullock4331 Damn youtube for having nonfunctioning notifications. That's quite interesting- it's wild they were paying you guys next to nothing for what is inherently skilled/precise assembley work. To have efficient per-worker use of the temp sensitive glue and more importantly to eliminate the maximum possible amount of inconsistency between final products with such manual methods, you'd think the wage should've been higher!
I worked on these systems as an apprentice, nice to know technology from the sixties is still relevant today. It makes sense that the military would still be using them. The biggest upgrade they made during my employment was RLG (ring laser gyroscope). This brings back memories of driving around in a Landrover testing a PADS ( position azimuth determining system) The MOD loves an acronym.
Years ago, before the satellite supported GPS system had been established, my artillery Battalion was issued a new vehical with this Inertial Navigation System mounted on it. We gave it trial at 29 Palms. We performed a 27 mile traverse and closed on a known point. After 27 miles, we had an error of less than 1 foot. That's not good enough if you're going to the moon, but plenty good enough when you are firing 155mm rounds with a 70 meter, (230 foot), killing radius.
@@oldgysgtDifferential gps uses a signal from a ground based station to further reduce errors associated with pure satellite systems and can therefore be traced when using this ground station which is not impossible to shall we say hack.
My great uncle worked for the Bendix Corporation in California. They had a contract to make ball bearings for a ballistic missile nav system. The balls had to be machined to millionths of an inch. As they began delivering the balls, the missile company was rejecting them as being out of spec. Bendix had to mount an investigation to understand what was happening. Turns out the method being used to measure them was so sensitive that it was measuring a thin film of oil left by the machining and adding it to the overall measurement. They began cleaning the balls with alcohol before measuring them and that solved the problem.
I was shown the somewhat secretive Inertial Guidance Systems used in our Intercontinental Ballistic Missiles. It was explained to me that in order to be highly accurate the systems ran 24 hours per day. That kept the system warmed up and ready to go on a moments notice. They did not just sit idle.
I found this to be a really clear and concise explanation of the fundamentals of INS, together with a very clear commentary. All of this in an incredibly short time. Excellent.
The submarines that I was stationed on in the 1980s had inertial navigation units which we used all the time. They were invaluable for navigating when we were submerged.
@@stayfree6115 Actually, no. Targeting was done by navigational sonar using meticulously mapped locations on the sea floor. The U.S. Navy actually had three ships, USNS Bowditch, USNS Dutton and USNS Michelson (the last replaced by USNS H H Hess) whose only purpose in life was identify appropriate locations (some relief but not too much) and then meticulous map those. There were a lot more identified locations than boomers, backups to backups to backups if you will. The last of the mapping ships was deactivated in the early 1990s. Another ship, USNS Waters, is still in service (I believe) as a testbed for modifications and improvements to the navigation sonar.
@@stayfree6115 The INS position was important for the initial phase of the missiles flight but I believe that latter missiles received a star tracker system (certainly Trident) & could be independent of GPS and INS. -The most accurate INS ever developed was the "Advanced Inertial Reference Sphere" (AIRS) for the MX peacemaker. I worked out it was accurate to 0.5m at the end of a flight of 6000nmi. It's actually accuracy error was about 100m due to flaws in the gravitational maps of the earth.
@@williamzk9083I don’t know that a W78 really needs to be placed that accurately. I mean, if you’re going to renovate the architecture of a medium sized city with one device, half a metre accuracy seems a bit tighter than strictly necessary.
The first series of airline ABS braking is pretty ingenious as well. There was a generator affixed to each wheel. As long as they were turning, they generated a specific voltage. When the wheel locks up, the voltage drops and the relay opens up the brake that goes to that wheel. When it starts spinning again, the brake pressure is allowed to continue.
Wow ! I always wondered what inside my Litton 72. As a retired military avionics technician, I flew 4000 flight hours in Lockheed C130 and P3 maritime aircraft. The Litton INS was one of the most reliable black boxes I had aboard the aircraft. We could fly in excess of 10 hour missions , in the middle of nowhere and upon returning , if the INS had a bad day it might be a half a mile off. Amazing technology that was before GPS navigation. Thanks for the video !
INS is brilliant. I worked with Litton 72 in the Nav 40 years ago. The whole concept of INS coupled with updating bias was facinating then and remains so today. Thanks for the post.
I love your use of dead reckoning to help explain the INS, I never thought about it like that before! Even modern airliners still USE INS/IRS (/Inertial Reference System), but it's mostly used to supply attitude and heading data to the PFD. It also still serves as a backup in case of a GPS and Radio Navigation outage, or the airplane's receivers fail.
What a superb device AND presentation, thank you :-) I remember the early US transcontinental INS validation flights. Soon followed by commercial aircraft such as Concorde and the first 747 series being fitted with three INS units that would monitor each other's performance... allowing a 747 to fly from Sydney to London (with two stops) in the pre-GPS era. Of course, there were also ground based radio navigation devices (VORs and NDBs) that allowed INS cross checks and updates, when necessary, as the route progressed.
I was a technician on a US Air Force test aircraft during the 1970s and we had a Litton LTN-51 INS onboard. It was a cantankerous device at best which often had significant errors. At the time, we also carried an Air Force navigator with us. His services were often needed. And if the INS ever failed inflight, it could not be reset until we were back on the ground.
In the Navy, was fascinated by a related bit of equipment, the gyrocompass. Also based on the gyroscope, but some ancillary equipment to turn it into a north-seeking system, independent of magnetic fields. Also a really cool device.
I would have loved to have had this video 30 years ago when I was teaching these systems in the Air Force. You took a very complex system and made it into an easily understood video. Outstanding job. I look forward to binge watching the rest of your content.
I was an Avionics Guidance and Control Technician in the Air Force/ANG working on KC-135 Air Refueling Aircraft , and worked on the INS System, very amazing technology. Another interesting System was the SAS (Stability Augmentation System) which helped stabilize the KC-135 during refueling operations. it contained Rate Gyros and Displacement Gyros on a platform to control spoilers on the wings to eliminate the effects of turbulence etc.. I always was amazed how it used these Gyros to detect direction of movement rate and displacement BEFORE it occurred to provide the necessary correction to maintain precise level fight. Which was a highly technical operation considering the size difference of the Refueling Tanker and smaller Jets being Refueled, which both responded differently to turbulence and other outside factors. Also the Fighters were flying at a much lower speed than Typical, and the KC-135 faster than typical. I flew on a few Refueling Missions in the U.S. and Japan. One of the most memorable was refueling other Air National Guard Aircraft which included F-15's F-16's and even F-4 Phantoms! the Air National Guard Units utilized Aircraft long after Active Duty Units moved on to newer planes. During childhood I lived in England where my Father worked in Air Reconnaissance, developing the Film from U-2 and SR-71 Aircraft. I would have loved to see one during Refueling from the Observation Window at the bottom of the fuselage near the Tail like the other Jets I had watched. I was always fascinated by the SR-71, and saw one fly directly overhead during and Air Show at Fairchild AFB. We we parked just outside the fence at the end of the runway and it flew very low overhead as it took off. The sound, and immediate blast of heat from the engines was intense! Years later while in Basic Training at Lackland AFB I saw another fly overhead during a Retirement Ceremony for it. They announced over the PA System as it went overhead and crossed various states soon after, and witnesses several Sonic Booms as it accelerated away. I was fortunate to be directing visitors and not forced to stand in formation on the Parade Grounds with most of the Recruits. They were not permitted to "Look Up" during the fly over, and see it.
That was soooo interesting with great explanations, thank you ! I didn’t know your channel I’m glad to discover it and look forward to see your next videos :)
This is an OUTSTANDING presentation of a fairly complex concept. I served 20+ years as an USAF Avionics Specialist (FB-111, F-16, F15), and our training was not this clear and concise. Great graphics and organized explanations: quick to “like” and glad to subscribe.
The missile knows where it is at all times. It knows this because it knows where it isn't, by subtracting where it is, from where it isn't, or where it isn't, from where it is, whichever is greater, it obtains a difference, or deviation. The guidance sub-system uses deviations to generate corrective commands to drive the missile from a position where it is, to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position where it was, is now the position that it isn't. In the event of the position that it is in is not the position that it wasn't, the system has required a variation. The variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too, may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computance scenario works as follows: Because a variation has modified some of the information the missile has obtained, it is not sure just where it is, however it is sure where it isn't, within reason, and it knows where it was. It now subracts where it should be, from where it wasn't, or vice versa. By differentiating this from the algebraic sum og where it shouldn't be, and where it was. It is able to obtain a deviation, and a variation, which is called "error"
Loved the video. That's the way I drive when I'm drinking. I hold my glass in two fingers, with my elbow not resting on anything. It once saved my life when I had some rolls and ended upside down.
The the number one reason the military uses INS is for stealth. No signals coming or going to be detected. The commercial application is for backup redundancy. Excellent presentation! ❤
Receiving GPS signals is just as stealthy. GPS satellites are constantly emitting all over the planet. There are no emissions from the aircraft. Actually any signal navigation, whether it's coming from the ground, sea, or another aircraft would be relatively stealthy as long as the receiving aircraft doesn't have to emit. But I guess INS takes away the need for signals altogether to some extent. The problem with INS without GPS/signal/manual correction is that it becomes inaccurate over time, "INS drift" as they call it.
Worth noting that because it is impossible to tell acceleration from tilt with no outside reference, instrument navigation is crucial for flying through clouds, low visibility, night, etc, or pilots could mistakenly fly straight into the earth, or at wonky orientations, especially when other aircraft failures occur. The gyroscopes are crucial, as well as altimeters.
A few crashes have happened because the pilot was damn sure the plane was rising, so they nosed down, right into the ground/water, when they should have just trusted the instruments.
Very interesting video! What I didn't yet really understand is why the whole platform needs to move. Can't you just have 3 Gyroscopes by which the orientation is being provided (which is basically the direction of the vector of the acceleration of gravity) then take the data of the accelerometers and subtract the gravitational acceleration from the resulting vector? Aren't moving parts also usually more error prone or maintenance intensive? What am I missing?
I'm delighted that you ask this question, because it's exactly the same conclusion engineers came to when digital computers started to become available! Modern systems do exactly what your intuition says: they correct for gravity by subtracting the vector through a computer. There is then no longer any need for moving parts at all, and this removes a lot of problems related to precision and accumulation of errors (exactly as you said). At the time of the INS shown in the video, computers were not yet available/compact enough (not sure which), so everything was done mechanically and through voltages in wires. This essentially was "the computer". Hope this makes sense, and the fact that you came to this conclusion by yourself means you thoroughly understand the essence of the topic. Have a good one!
Ok dude, these are exactly the videos I've been searching for for quite some time. This one alone made me subscribe within a few mins. Great work thank you
I'm sorry. Like most, you get the name wrong. It is DED Reckoning, for Deductive. No deaths occurred in the creation of this practice. You are DEDUCING where you are by the recording of your position over time. Thanks for listening, and you can look it up...
My father was a guidance control engineer in the late 50s. He worked on gyro’s @ SPERRY RAND working on the Sidewinder missile system and the Polaris program. In 1962 He went to work for NASA working under contract @ General Electric to work on guidance controls for the Apollo program. In 1969 we moved to northern Va. where he worked @ the Navel Research Laboratory. He wasn’t able to tell us much about this job but what I gathered is that he was working on future missile systems for the US NAVY.
A few years ago I bought a gyroscope for F104 from a military surplus online store (the orange part). Now I know that it was not complete and that we even need two and even a platform. Nice video, I will study it carefully.
Having never seen this before, it’s quickly plainly obvious what it’s doing, but that’s friggin amazing that it can be so precise just based on force and orientation
This explanation is terrible. You cannot talk about Inertial navigation without explaining the relationship between acceleration, velocity and distance and the mathematical operation of integration. Understanding that is fundamentally essential to understanding the principe of inertial navigation. Why do we measure acceleration? What do we with the electrical signals output from the accelerometer? This kind of video is misleading and it is not teaching the basic principles.
@@RawbLV Understanding why acceleration is measured isn't really a technical aspect. It is fundamental as to why the inertial nav system works. It is like producing a video to explain how a quartz crystal watch works without explaining the role of the quartz crystal. It is that fundamental.
@@RawbLV You obviously don't know the principles behind inertial guidance, do you? To explain how inertial nav systems work means you have to explain the relationship between acceleration and distance. Initial nav systems *MEASURE* acceleration so they can then *CALCULATE* distance. The relationship between acceleration and distance *IS* mathematical! Therefore you *CANNOT* adequately explain how inertial guidance works without explaining why acceleration is measured, what the purpose is *AND* the relationship to distance. Come back to me when you *TRULY* understand this subject.
I worked with these systems in Naval Aviation in the early 70's. I felt pretty accomplished since just two years earlier I was delivering electrical supplies to construction sites after high school. Both lead to a long career in the electrical trade. Thanks to all involved!
Couple of things: The item displayed is a "Twin Gyro Platform (TGP)" it provides the inputs to a Navigation computer for integration with time to get velocities and distance. The TGP not only has to maintain level but must also point True North (the Accelerometers provide N-S and E-W acceleration into the nav computer, which then calculates Lat Long, distance traveled, course etc. ). During start up the TGP senses the earths rotation to perform a levelling and TN alignement (helps if you know your starting Lat, Long). Limitations of the TGP - Does not like to climb vertical, nor travel over N or S poles (gimbal lock).
Before MEMS, accelerometers used a taught steel wire with a weight in the middle of the wire. On each side of the weight, the two sections of wire were kept vibrating (like a guitar string) using electromagnetic feedback. The cycles of the vibrating string on each side of the weight were fed into a counter - each cycle on one side of the weight caused the counter to count up, and each cycle on the other side caused the counter to count down. Under no accelleration, each side of the wire is vibrating at the same frequency and so the number of "up" counts over any time period equals the number of "down" counts and the counter stays at zero. If the wire was accellerated at right angles to the wire, then the frequency of both sides would change by the same amount and the counter will still stay at zero. If however there is a vector of accelleration along the same axis as the wire, then the weight causes one side of the wire to get tighter, increasing its frequency, and the other side to go slack, decreasing its frequency. Thus the counter will no longer get the same number of up and down counts, and its count (+ve or -ve) will equate to the total accumulated accelleration experienced along the axis of the wire since the counter was last cleared.
thanks for the video. as a biomedical engineer I just want to point to something in the video : humans can tell if they are tilted because we have the inner ears that does the same job you're describing for us, except at much higher real time speed to keep us balanced too. (being bipedal is not that easy). so yeah our bodies don't have that limitations, it just too natural for us we don't pay attention to it.
Your vestibular system (inner-ear) is sensitive to angular acceleration, which is a rotation over time. If your orientation does not change over time (zero acceleration), your inner-ear won't be able to tell you if you're tilted or not. Thanks!
@@FlyByMaxsorry I fail to understand your point. is there a case where the body(or the head at least) can tilt without it changing orientation during flights?
@@aymenninja8120 You're right, to change orientation means an angular acceleration must have occured. My point is this: after a certain amount of time of constant orientation/angular velocity, your vestibular system no longer senses any input. Imagine sitting on a chair with your eyes closed and rotating at a constant speed. After a while you won't be able to tell you're rotating. This means that we must still need an external reference (e.g., eyes, or in the video - a gyroscope) to figure out our true orientation. Sorry if I misunderstood your comment, have a good one!
Well you got the explanation about the ship's 'log' a little backward. They didn't time how long it took for a certain number of knots to be pulled over the side, they did the opposite. They threw the end of the rope over and turned an hourglass. Then counted the number of knots that went over the side in a fixed amount of time. (that is, the time was always the same and the ship's speed would determine how many knots were paid out. P.S. The end of the rope had a small triangular piece of wood that was rigged to be pulled facing into the water to keep that end more or less stationary. After the measurement, a sharp 'tug' would pop a little peg out and let the wood turn edgewise to the direction of movement so it was easier to pull the 'log line' back in again. :)
When I started work on my first job (aquiring data from oil boreholes), we had an instrument in our toolstring that used accelerometers and magnometers to determine the deviation and azimuth of the toolstring. Then, once the data aquisition, is complete, we could process the data into a true vertical depth format, instead of measured depth.
@07:30 no, wrong. you can tell if you are going on flat road or hill, because the CG changes with direction of gravity force, thus your senses in ear and body sense change in acceleration wrt CG.
Ive always been amazed by this technology, requires no external help or signal of any kind. Certainly not nearly as accurate as newer technology but its SUPER reliable and ingenius.
I worked on spinning mass gyro INS systems on F4s. It amazing what we do today compared to back then. Except ours was a two gyro system that stabilized the platform. The accelerometers measured the movement of the aircraft and the separate analog computer did the navigation calculations. Later after college I was a naval engineer and I worked on fiber optic gyros that do the same basic thing that lasers do now. But you can wrap many layers of fiber optic cable around the optic path such that the light goes much further and the phase difference is more accurate. Then I worked on EGI embedded GPS and a INS in the same system. Lots of stuff going on.
Excellent video! I was worried that you made a fundamental mistake by stating that the stable platform would always remain level with the horizon early on in the video, but you’ve covered that wonderfully in the last chapter. The inertial measurement units used on the Apollo lunar modules had issues caused by apparent drift when after they were shut down to save power on the surface. The moon would rotate during the few days spent on the surface and caused the IMUs to not know which way was up when they were restarted. The engineers solved this by detecting the acceleration caused by gravity and a star sighting to correct for any errors caused by uneven terrain.
02:30 I have to tell you exactly where your Dutch sailor is - and he’s not leaving Amsterdam…… Your inset is a schooner departing Portsmouth Harbour (that’s Hampshire, England) about five miles from whee I am typing this and it’s heading south with the Isle of Wight in the distance and Spit Sand Fort some 500 metres off the vessel’s starboard bow. The three masts that you see slightly closer are part of a navigation system for our Queen Elizabeth class aircraft carriers and they hark back to an even early method of navigation using “transits”.
That is one of the greatest inventions mechanical over software I have ever seen. It might be one of the most important inventions in the future. Amazing true amazing!
Wonderful article. Complex enough to understand things but not so complex that it confuses things. However, there are a couple of things I'd like to comment on. As remarked by several others, I am sure that this INS was not on the F-104; that plane was much too early for this type of system. As stated by others, it was used on the F-4C and later versions of that plane. I think it was the first widely used airborne INS. In the mid to late 60's I taught the ASN-48 and ASN-46 navigation system at the Air Force technical school at Keesler Air Force Base in Biloxi Mississippi. At that time I knew a lot about how the thing worded, but alas a lot of that knowledge has disappeared with time. One thing I do remember is that the gyros and gimbals communicated their positions to the rest of the aircraft's avionics by using resolvers, which were analog predecessors of our current digital encoders. As stated in the video, the accelerometer outputs were integrated in analog electronics. These signals were then used to move motors which turned shafts that provided mechanical analogs of N and E velocities. Subsequently the velocities were fed to an additional stage of integrators (and motors and shafts) which produced position readouts. One question that I saw several times in the comments was about gyrocompassing. That was part of the system startup and calibration. I have forgotten the exact method, but it worked something like this. If the stable platform was not exactly aligned to N, then one of the corrections sent to the azimuth axis would cause the platform to slowly tip. This error was detected by one of the accelerometers and was fed back to the azimuth axis to rotate it to North. When the azimuth was closer to N, then there would no longer be a tip and the correction would be stopped and the system would switch out of gyrocompass mode and into the normal operating mode. (or something kinda like that!) Keep up the good work!
Nice! Just to emphasise, the accelerometers measure a change in velocity or speed in a particular direction, not the velocity. The velocity is determined from the initialization of a zero point along with the additions (and subtractions) of accelerations in three directions along the route. The gyroscopes keep track of the direction changes made during the route. The computer keeps track of all the data and gives the location at any point along the route. Thanks for this great video!!!
After a 12 hour cross pacific flight, my INS position was over 100 NM off, about 3.5x over allowable limits. All depends on how well calibrated the system is though
Thank you for taking the trouble to create this truly excellent video. I can't begin to imagine how much time and effort it must have taken, but perhaps not quite as long as it took to develop the LN3-2A itself! Would it be fair to say that the gimbals solve the trigonometry equations which could not be solved using computers and data acquisition available at the time? As a previous comment notes, laser ring gyros and modern microprocessors allow a strapdown solution with no moving parts, like motors, slip rings and synchro resolvers. Far more reliable and accurate and (relatively) lower cost I'm sure, but now there is nothing to see - no inspiration. Like electric motors vs steam engines! I believe that there was an even bigger, heavier control system attached to the platform and this comprised gears and electronics to process the signals for presentation to the pilot / navigator. I have some pictures and diagrams if anyone would like to PM me.
Of interest to watchers of this video is that three people were formally recognized for their contributions to basic science leading to success of the Apollo program and moon landing. They were Wernher von Braun for rocketry, Dr Robert Cannon for development of the inertial navigation system for Apollo, and Margaret Hamilton for the computer system that controlled the flight. In 1969, I was an undergraduate at Stanford and took Engineering 104, “Dynamics of Physical Systems,” a course taught by Cannon. In fact, he authored the textbook used in the class. He announced at the beginning of the course that he would give anyone a dollar for each typo we found in the book. I think I found the most. We developed a nice friendship, and he even invited me to his home for study help. What a great guy!
The feedback part was neatly glossed over as basically "magic". I didn't even know about the problem before and an actual explanation on how the feedback works would have been nice(I suspect it's just a filter -- very low frequency signals come from the Earth's rotation as the Earth is rotating "slowly" relative to the aircraft's movements).
The fact that somebody took the time to make a video on the subject alone not to mention actually getting everything correct showing that they have the understanding of what they’re talking about not to mention the presentation alone pretty much to me I feel like would aid in educating somebody whether they were looking for this subject or had an interest in aerospace engineering or engineering alone this video was to me a combination of a documentary as well as a “How to” I know how to video really isn’t what I’m trying to explain but overall just gives a clear understanding therefore you got yourself a new subscriber! I look forward to seeing what else you cover on top of that I wouldn’t be shocked if you reach 10,000 subscribers either on or before the first of the year and hopefully sooner but 100 K by the end of next year!
The guidance system knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance system uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't. In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the guidance system must also know where it was.
I think these explanations are an attempt at (not bad) humor. You say, "By subtracting where it is . . ." If you know where it is so that you can do the subtraction, why bother? You already know where it is.
So much wrong here. We (mariners and pilots) still use knots (Nautical miles per hour) because a nautical mile is 1/60th of a degree of latitude. This makes it easy to estimate things using the formula 60D/ST. Early ship crews tied knots into the speed log line to do the measuring, so Nautical Miles per hour got shortened to Knots. Early explorers made ocean travel navigation using early versions of the sextant (a tool to measure angles) to keep themselves on a latitude line. Each day at apparent noon the navigator would do a noon sight of the sun at its apogee. This angle of the sun off the horizon plus some simple addition and subtraction would give the navigator their latitude. If during the previous day they drifted off course from wind or current, they could correct over the next 24 hours. A good navigator could keep the ship within a few miles of a latitude line on a weeks long crossing. A trip east or west would start with the ship travelling north or south along a coastline until they reached a specific latitude across from their intended target across the sea, then the east or west travel would begin, using a chronograph to keep time, plus the speed log and DED Reckoning (means Deductive) to estimate position. Folks who don't know any better call it dead reckoning. All of these errors and misconceptions in the first 4 minutes make me wonder how much of the rest of your video is in error... Read "Carry on Mr. Bowditch" and "Longitude" "Celestial Navigation" and "The American Practical Navigator" "Chapmans" is good too for more basic and comprehensive boating knowledge. Now-a-days all this is computerized, but we still have a compass, chronograph and Sextant aboard, along with the tables to make it all work.
Used to work on older INS gyros. I can't count how many times they wouldn't spool up and the fix was to literally remove the box from the frame, drop it about 12 inches on the ground and reinstall. There was a tech fix involving a rubber mallet but dropping it did the trick 95% of the time. This saved the US taxpayers untold fortunes in back-shop repairs.
There needs to be more videos about the INS because it is such a revolutionary system! When aligning, that is the ONLY time you need outside input so it’ll work in conjunction with stuff like synthetic vision and EGPWS. But that’s it. You can lose all VOR and VFR stations, all GPS satellites, and all your comms and still be able to go wherever you want without an issue.
Extremely interesting video. As other peoples said, modern ins uses either laser gyros, based on the sagnac effect, discovered before restrained relativity, but easily explained now thanks to it, or a new technology is based on the oscillating deformation of a glass cup, initially caused by piezzo electricity, the cup acts as a pendulum which oscillating planes doesn't change despite the rotation of the support (Foucault's pendulum)
Great video. Almost all INS systems now are a strapdown system with laser gyros and gimbal system the moveable part has been replaced with light. Two beams in opposite directions about a single axis rotation is measured by the time difference to a central point on a mirror. 3 gyroscopes in each axis are now used. Accelerometers function as before. Next video could explain this better than I can here
Thank you so much! I've also thought about doing a video on strapdown INS's exactly as you say :) who knows!
@@FlyByMax pls do it
Yes, please!!!!
Maybe three gyroscopes, one for each axis.
Thanks for the info. But I heard that modern aircraft still need time to start and calibrate the gyroscope every time the plane going to start. Is that still true ? And why the modern INS (with laser/light) still need that ?
Hello!
This video is targeted towards people who are trying to learn about INS systems for the first time, so to keep it digestible I decided to leave out some details. Here's a quick summary of things that didn't make it in:
- 03:16 Fun fact: in 1714 the Longitude Act was passed by the Government of Great Britain to develop a sufficiently accurate clock for maritime navigation.
- 04:15 The real LN-3 had four gimbals instead of three to prevent a phenomenon called "gimbal lock". This happens when two of the rotational axis align, constraining the system to rotate in only two of the three dimensions.
- 06:15 Using acceleration to determine your position is an entire topic in itself, called integration of position. The maths behind it is actually quite simple, and computers can do these calculations extremely fast. Like the sailor example, INS systems need to know where they start off from before they can start this process.
- 08:04 The same "tilting" problem whereby gravity influences the measurement of accelerometers also applies to roll and yaw. That's why we need all three gimbals.
- 09:58 Although accelerometers do not directly measure position and velocity, these can be calculated (or integrated) by using the acceleration. Like all other instruments, accelerometers are imperfect and will inevitably measure an error which will accumulate over time (due to dead reckoning).
- 10:02 Similar to the previous point, gyroscopes will also build up an error over time due to gyroscopic precession and the friction of the gimbals. To correct the gyros for transport wander and apparent drift, this same phenomenon is used to apply torques to rotate the gyroscopes according to the spin of the earth and velocity of the aircraft.
- 10:23 In reality, due to the accumulation of errors the platform *will* actually measure a small component of gravity. The reason this does not get out of hand is due to the feedback loops, which will cause the platform to oscillate as a "Schuler pendulum" (wobble back and forth around the centre of the Earth).
- 10:36 Due to the previous points, over time INS systems will build up an error despite the feedback loops. They are therefore periodically updated by other navigation systems such as GPS or VOR.
I mention that INS systems keep the platform level with the horizon, technically this is not true (thanks Ken Watanabe). They keep the platform level with the local horizontal plane, since the horizon could in theory depend on mountains/terrain. The point is that the platform stays level, perpendicular to the direction of gravity.
Finally, these days aircraft no longer use moving-platforms but correct for gravity using maths in a computer, although the principle is the same. These types of systems are called "analytic platforms" since the computer basically uses a virtual platform instead of a real one. Another name for them is strapdown INS systems, since I guess they can be directly "strapped" to the aircraft without the need for gimbals. These more modern variants use ring laser gyroscopes, but rely on the same concepts introduced in this video.
If I missed anything or made a mistake, definitely let me know. Thanks!
Awesome thank you for sharing this about Navigation Systems. More videos on the physics of flight?
Seriously, would it have killed you to mention gimbal lock? The fourth gimbal is extremely important. The first systems only had three. But there was a dog fighting maneuver taught to F-4 pilots in Vietnam that locked up the platform every time. Was never a problem until then.
And it was funny that you showed a video of an A-10 which didn't have INS until the mid '80s, 10 years after the first aircraft were delivered to the USAF. The rumor is they came with East German road maps.
And there was no other system in the old days that could update the INS. We used a thing known as a waypoint. You'd type in the latitude and longitude of a known landmark and tell the system to update when you flew over it.
And something else, the gyroscopes do not align directly with the poles and equator. The original systems did and were severely erroneous when going above 72 degrees north or below 72 degrees south because of the converging lines of longitude. But you didn't even mention how gyroscopes precess until they find the earth's rotational axis.
The platform actually orients itself to local level, not the horizon. The horizon changes with altitude, local level doesn't. It does this using the accelerometers when the aircraft is sitting still during system warm up.
I learned how to dead reckon in AFJROTC in high school. The process and computations performed by an INS are completely different.
I used to be in the Air Force. Yep. I maintained the INS on the A-10 at Davis Montham AFB. My original job title was Avionic Inertial and Radar Navigation Systems Specialist. Then the Air Force reconfigured some specialties in the late '80s and I became Avionics Guidance and Control Systems Specialist.
More in-depth stuff please.
and now modern aircraft no longer use this type os system except as a backup. They use a "ring laser Gyro"
Perhaps a explanation of the more modern AHRS (attitude heading reference system) would be a nice add on. In my modern aircraft, we have 3 laser ring gyros as back up. The primary source for navigation is GPS first, then IRS. GPS is almost a replacement for ground based aircraft navigation, including landing in fowl weather. Although for the lowest landing minimums, 200ft or lower, ground based systems are required.
I was an Avionics technician and Loadmaster on C-130 aircraft for both the Marine Corps and Air Force, and this beautifully explains how INS systems work.
Thank you so much, means a lot coming from a real world avionics technician!
Then could you please explain, how in real hardware the compensation realy work, by moving around the Earth. Other vlogers show, that there must be two electrolytic tilt sensors, to hold the platform with two gyroscopes steady horyzontally to Earth surface. Is it right?
It was a pleasure to read your comment.. I’d love to hear all your knowledge and memories.
Sounds amazing.. thank you. 👏🏾👏🏾👏🏾👏🏾
I was an Inertial Navigation (and Radar) Avionics Tech from 1979-1983 on the USAF F-111. The INS was an 80+ pound, 2ft x 2 ft box when removed from the aircraft for testing in our shop, thus required 2 persons to lift and mount onto the test equipment. Parts had to be replaced and calibrated routinely for optimal performance.
M
Sounds like the old ASN84 we had prior to upgrading to LTN72.They took longer to align and quite often required a lot manipulation to get them up and keep them running. Stell shots were a must do, though we still had Omega.
what an amazing device
I used to fly them, it was accurate to about one part in ten thousand. Quite good for the era.
Thats pretty neat man... It's remarkable how small INS systems has got by comparison. I work avionics on F-35s, and now its just a tiny little white composite box you can hold in a single hand. It's pretty impressive too, It will have virtually zero drift even without any GPS fix being provided for a good 30 or 45 minutes. Not bad for degraded operation lol
My dad did a lot of this when I was a kid. He didn't actually design the inertial navigation systems, he was responsible for testing and verifying them. He would talk about "gimble lock", warplanes feeding their guidance information to the ordinance, and doing star sightings from a moving plane to check the gyros. I believe they also had a physical test stand that consisted of concrete set deep into the earth.
When the ring laser gyros took over, nobody knew how to make them. They would manufacture like 100 and test them all in hopes of getting one that actually worked.
Scott, your dad and my uncle probably worked very closely on this together. my uncle was heavily involved in this science and remained with it being called back to fix some issues with the cruise missile.
what an exciting device to work on!
I think he abused you
@@georgeburns7251 What gave you that?
It's "gimbal lock". More about that here: th-cam.com/video/OmCzZ-D8Wdk/w-d-xo.html
@@dysfunctional_vet The plant my dad worked at was in Little Falls, NJ. The company went through different mergers and whatnot but he worked for Singer or Kearfott at the time. Once a year they would have an open house and us kids would get to tour the plant. They also did lots of other cool family stuff that you don't see today. My clearest memory of the plant was the giant centrifuge. We also got reams of test results on tractor feed printer paper that we would take home and color on the back of.
I'm a Pilot and during theory training, we studied INS/IRS in great depth. This videos is an amazing introduction to such a system and I wish we used this video in class. Kudos for such a master explanation!!
You are still pilot ??
@@srikanthsarjanaa8075He's the pilot that will save PAKISTAN
Outstanding work. I can easily see the hidden hours of research, animation, and production that went into this video. Also, teaching in a clear and comprehensible level takes a master. Well done sir.
Thank you, means a lot!
agree! maybe sometime another one with gimble lock added.
gotta love the good old double integral
100% agree
Thanks for showing the video. It brings back old memories. It appears to be the Litton LN3 Inertial Platform. I started my Aerospace career at Litton back in the early sixties as QA Inspector in the LN3 lab. A beautiful instrument and quite accurate for an early 1960's piece of navigation equipment. Well done!
Thank you!
I recently had a tour at the Litton (now Northrop Grumman) site in Woodland Hills, CA. They showed us everything they were working on.
I'll definitely say, these guys are geniuses, and I'm glad to be working with them. They're constantly innovating and coming up with new tech.
So the INS unit knows where it is because it knows where it isnt?
Yes you got it
You have to program the time day and month and year for the unit to know where it's at as the small telescope that reads star light during the day or night.
Funny reference 😂
Absolutely!!
I worked with inertial navigation on Submarines. The saying was a multimillion dollar device that you tell it where it is and it will tell you where you are. The initial position is everything.
Very interesting. I actually build part of these inertial guidance systems back in the mid 1960’s. I worked for Litton Systems just outside Toronto. Very fine work under microscope and a lot of assembly was done in “clean rooms” where the air inside was filtered. Anyone working inside that area had to wear special clothes that went over all your street clothes including your shoes. Only your face was exposed. The fingers on your hands were covered in finger cots, they looked like miniature prophylactics. If you had a cold or were sneezing you weren’t allowed to go into that area. The tolerances on the gyros were so tight a piece of dandruff could gum up the works. Lots of inspections done on this work.
How old r U❓
Sir, that’s absolutely fascinating. Lord knows my notifications for TH-cam are all sorts of outta wack, but I’d appreciate any more info or stories you have from your time there, or in related fields.
As someone who loves American history and 20th century history (especially postwar) - the amount of mundane people one can meet now in person or online is wild.
All these stories hardware and vehicles, and those who had hands-on day to day such as yourself are here and around to speak about it.
@@yeetyateyote5570 , I only worked at Litton Systems for about 13 months. I mostly worked on what was called the end bell which underneath the round end of the gyro. The metal was anodized aluminum. There were holes drilled for very tiny electrical contacts all around the circumference. We had to glue in tiny literally gold coated contacts into these holes withe special adhesive. I believe the tube was called LC 9. They were kept in a freezer. We had to sign each tube out and they were only good to use for 30 minutes. We used a tiny applicator to put about a 90% circle around the gold contact which was imbedded in a glass insulator. This work was done under a 10x power microscope. We had to place the contact into the hole and not get any of the glue onto the side on the way down. These end bells were placed into small autoclaves to cure the glue. I forget how many contacts were on each bell. We had rubber coated trays that held 5 end bells. We were expected to do I think 30 per week. Not big pay, only around $1.15 hourly in ‘64. All of these end bells were inspected to ensure there was no glue on the side of the walls. After curing a clear sealant was put onto each contact and it was cured too. If you had any rejected you had to clean it all up and re submit it for inspection. I was pre darn good after getting a few rejections at first. Being more precise was better than cleaning up.
@@rickbullock4331 That’s fascinating. I got my pilot’s license in 1992, but never used ILS because my family owned many FPO that my grandfather (an early adopter of personal aircraft) had founded during the time many airports were being built. I’m shocked when this video says that a gyro will need correction due to changing gravity. Although it was never discussed, I assumed that a gyro would adjust to local gravity and always stay exactly positioned as it was started in reference to L&L. If I took off from Lubbock to Honolulu, I assumed old ILS was flattening out as I flew- in relation to the starting position. How did I miss this all these years? LOL
I never learned ILS or even continued flying fixed wing, as I knew 30 years ago that we had employees that would always be better at it than me. My thing is exotic cars and guns. I figured I would live longer if I let the guys who were passionate about flying to the flying. I’ll drive the race cars once we get there and make my money with guns.
BEST WISHES.
Nick
@@rickbullock4331 Damn youtube for having nonfunctioning notifications.
That's quite interesting- it's wild they were paying you guys next to nothing for what is inherently skilled/precise assembley work. To have efficient per-worker use of the temp sensitive glue and more importantly to eliminate the maximum possible amount of inconsistency between final products with such manual methods, you'd think the wage should've been higher!
This channel is so underrated! Love your content and the animations especially. Keep it up!
Thank you so much! Glad you liked the animations, it was a real learning curve for me :)
I worked on these systems as an apprentice, nice to know technology from the sixties is still relevant today.
It makes sense that the military would still be using them.
The biggest upgrade they made during my employment was RLG (ring laser gyroscope).
This brings back memories of driving around in a Landrover testing a PADS ( position azimuth determining system)
The MOD loves an acronym.
Years ago, before the satellite supported GPS system had been established, my artillery Battalion was issued a new vehical with this Inertial Navigation System mounted on it. We gave it trial at 29 Palms. We performed a 27 mile traverse and closed on a known point. After 27 miles, we had an error of less than 1 foot. That's not good enough if you're going to the moon, but plenty good enough when you are firing 155mm rounds with a 70 meter, (230 foot), killing radius.
They are still used in modern artillery, because gps can be jammed or tracked.
@@udenszirnis1644; I thought GPS was passive. How can the user be tracked?
@@oldgysgtDifferential gps uses a signal from a ground based station to further reduce errors associated with pure satellite systems and can therefore be traced when using this ground station which is not impossible to shall we say hack.
My great uncle worked for the Bendix Corporation in California. They had a contract to make ball bearings for a ballistic missile nav system. The balls had to be machined to millionths of an inch. As they began delivering the balls, the missile company was rejecting them as being out of spec. Bendix had to mount an investigation to understand what was happening. Turns out the method being used to measure them was so sensitive that it was measuring a thin film of oil left by the machining and adding it to the overall measurement. They began cleaning the balls with alcohol before measuring them and that solved the problem.
I was shown the somewhat secretive Inertial Guidance Systems used in our Intercontinental Ballistic Missiles. It was explained to me that in order to be highly accurate the systems ran 24 hours per day. That kept the system warmed up and ready to go on a moments notice. They did not just sit idle.
Makes sense, I know that the INS alignment for planes can take up to 10 minutes. Wasting that much time for an icbm would be unnacceptable
In the early days the INS took 30 minutes to warm up and be ready to navigate. The ring LASER gyros take 7 minutes now.
I found this to be a really clear and concise explanation of the fundamentals of INS, together with a very clear commentary. All of this in an incredibly short time. Excellent.
This means a lot more to me than you can probably imagine. Thank you :)
The submarines that I was stationed on in the 1980s had inertial navigation units which we used all the time. They were invaluable for navigating when we were submerged.
Used these systems in submarines in 1960’s. Very accurate depending on period checks with other methods
They were extremely accurate, I believe the missile guidance systems we're dependent on them for target accuracy.,
@@stayfree6115 Actually, no. Targeting was done by navigational sonar using meticulously mapped locations on the sea floor. The U.S. Navy actually had three ships, USNS Bowditch, USNS Dutton and USNS Michelson (the last replaced by USNS H H Hess) whose only purpose in life was identify appropriate locations (some relief but not too much) and then meticulous map those. There were a lot more identified locations than boomers, backups to backups to backups if you will. The last of the mapping ships was deactivated in the early 1990s. Another ship, USNS Waters, is still in service (I believe) as a testbed for modifications and improvements to the navigation sonar.
@@stayfree6115 The INS position was important for the initial phase of the missiles flight but I believe that latter missiles received a star tracker system (certainly Trident) & could be independent of GPS and INS.
-The most accurate INS ever developed was the "Advanced Inertial Reference Sphere" (AIRS) for the MX peacemaker. I worked out it was accurate to 0.5m at the end of a flight of 6000nmi. It's actually accuracy error was about 100m due to flaws in the gravitational maps of the earth.
@@williamzk9083I don’t know that a W78 really needs to be placed that accurately. I mean, if you’re going to renovate the architecture of a medium sized city with one device, half a metre accuracy seems a bit tighter than strictly necessary.
The first series of airline ABS braking is pretty ingenious as well.
There was a generator affixed to each wheel. As long as they were turning, they generated a specific voltage. When the wheel locks up, the voltage drops and the relay opens up the brake that goes to that wheel. When it starts spinning again, the brake pressure is allowed to continue.
Is that the Maxaret system?
Don't remember..
Wow ! I always wondered what inside my Litton 72. As a retired military avionics technician, I flew 4000 flight hours in Lockheed C130 and P3 maritime aircraft. The Litton INS was one of the most reliable black boxes I had aboard the aircraft. We could fly in excess of 10 hour missions , in the middle of nowhere and upon returning , if the INS had a bad day it might be a half a mile off. Amazing technology that was before GPS navigation. Thanks for the video !
Thanks for sharing your experience and thanks for the feedback!
Amazing how engineers could figure all this out
And the engineering inside is miraculous
How did the INS know the wind drift?
INS is brilliant. I worked with Litton 72 in the Nav 40 years ago. The whole concept of INS coupled with updating bias was facinating then and remains so today. Thanks for the post.
This will blow flat-earthers minds.
They dont have minds
Casually debunks earth's rotation at 1:05
I love your use of dead reckoning to help explain the INS, I never thought about it like that before!
Even modern airliners still USE INS/IRS (/Inertial Reference System), but it's mostly used to supply attitude and heading data to the PFD. It also still serves as a backup in case of a GPS and Radio Navigation outage, or the airplane's receivers fail.
What a superb device AND presentation, thank you :-) I remember the early US transcontinental INS validation flights. Soon followed by commercial aircraft such as Concorde and the first 747 series being fitted with three INS units that would monitor each other's performance... allowing a 747 to fly from Sydney to London (with two stops) in the pre-GPS era. Of course, there were also ground based radio navigation devices (VORs and NDBs) that allowed INS cross checks and updates, when necessary, as the route progressed.
I was a technician on a US Air Force test aircraft during the 1970s and we had a Litton LTN-51 INS onboard. It was a cantankerous device at best which often had significant errors. At the time, we also carried an Air Force navigator with us. His services were often needed. And if the INS ever failed inflight, it could not be reset until we were back on the ground.
In the Navy, was fascinated by a related bit of equipment, the gyrocompass. Also based on the gyroscope, but some ancillary equipment to turn it into a north-seeking system, independent of magnetic fields. Also a really cool device.
Gyrocompass, that is quite interesting.
i was building an inertial navigation system as a part of my graduation project before this video popped up in my feed and crushed my dreams ; )
I would have loved to have had this video 30 years ago when I was teaching these systems in the Air Force. You took a very complex system and made it into an easily understood video. Outstanding job. I look forward to binge watching the rest of your content.
Thank you!
We need more of this kind of videos. The quality is fenomenal. There is so much more of aviation systems to cover
Super informative and very professional video! This channel deserves more recognition!!
Thanks a lot :)
The video starts at 4:08 not before. Beautiful, thank you! 🙂
Need more videos like this! Keep it up!
Thank you :)
I was an Avionics Guidance and Control Technician in the Air Force/ANG working on KC-135 Air Refueling Aircraft , and worked on the INS System, very amazing technology. Another interesting System was the SAS (Stability Augmentation System) which helped stabilize the KC-135 during refueling operations. it contained Rate Gyros and Displacement Gyros on a platform to control spoilers on the wings to eliminate the effects of turbulence etc.. I always was amazed how it used these Gyros to detect direction of movement rate and displacement BEFORE it occurred to provide the necessary correction to maintain precise level fight. Which was a highly technical operation considering the size difference of the Refueling Tanker and smaller Jets being Refueled, which both responded differently to turbulence and other outside factors. Also the Fighters were flying at a much lower speed than Typical, and the KC-135 faster than typical. I flew on a few Refueling Missions in the U.S. and Japan. One of the most memorable was refueling other Air National Guard Aircraft which included F-15's F-16's and even F-4 Phantoms! the Air National Guard Units utilized Aircraft long after Active Duty Units moved on to newer planes. During childhood I lived in England where my Father worked in Air Reconnaissance, developing the Film from U-2 and SR-71 Aircraft. I would have loved to see one during Refueling from the Observation Window at the bottom of the fuselage near the Tail like the other Jets I had watched. I was always fascinated by the SR-71, and saw one fly directly overhead during and Air Show at Fairchild AFB. We we parked just outside the fence at the end of the runway and it flew very low overhead as it took off. The sound, and immediate blast of heat from the engines was intense! Years later while in Basic Training at Lackland AFB I saw another fly overhead during a Retirement Ceremony for it. They announced over the PA System as it went overhead and crossed various states soon after, and witnesses several Sonic Booms as it accelerated away. I was fortunate to be directing visitors and not forced to stand in formation on the Parade Grounds with most of the Recruits. They were not permitted to "Look Up" during the fly over, and see it.
That was soooo interesting with great explanations, thank you ! I didn’t know your channel I’m glad to discover it and look forward to see your next videos :)
Thanks a lot :)
This is an OUTSTANDING presentation of a fairly complex concept. I served 20+ years as an USAF Avionics Specialist (FB-111, F-16, F15), and our training was not this clear and concise. Great graphics and organized explanations: quick to “like” and glad to subscribe.
Thanks!
The missile knows where it is at all times. It knows this because it knows where it isn't, by subtracting where it is, from where it isn't, or where it isn't, from where it is, whichever is greater, it obtains a difference, or deviation. The guidance sub-system uses deviations to generate corrective commands to drive the missile from a position where it is, to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position where it was, is now the position that it isn't. In the event of the position that it is in is not the position that it wasn't, the system has required a variation. The variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too, may be corrected by the GEA. However, the missile must also know where it was. The missile guidance computance scenario works as follows: Because a variation has modified some of the information the missile has obtained, it is not sure just where it is, however it is sure where it isn't, within reason, and it knows where it was. It now subracts where it should be, from where it wasn't, or vice versa. By differentiating this from the algebraic sum og where it shouldn't be, and where it was. It is able to obtain a deviation, and a variation, which is called "error"
I was hoping someone would leave this comment, fantastic.
If Missiles always worked perfectly, they'd call them "Hittiles".
Go away
Wish this video was published sooner. When I was doing my ATPL last year I struggled so so much to undertand how INS works
Thank you for the video. As a non-technical person, the workings of an INS were clearly explained and illustrated. Nice work!
Thanks!
Loved the video. That's the way I drive when I'm drinking. I hold my glass in two fingers, with my elbow not resting on anything. It once saved my life when I had some rolls and ended upside down.
I love the channel, all videos are very high quality, I learning many stuff inside
Thank you!
The the number one reason the military uses INS is for stealth. No signals coming or going to be detected. The commercial application is for backup redundancy. Excellent presentation! ❤
Thank you!
@@FlyByMax your channel is being spammed by "text me"
Also no jamming. GPS can be uses for guidance by just receiving signals without emitting but can be jammed. INS can't
Receiving GPS signals is just as stealthy. GPS satellites are constantly emitting all over the planet. There are no emissions from the aircraft. Actually any signal navigation, whether it's coming from the ground, sea, or another aircraft would be relatively stealthy as long as the receiving aircraft doesn't have to emit. But I guess INS takes away the need for signals altogether to some extent. The problem with INS without GPS/signal/manual correction is that it becomes inaccurate over time, "INS drift" as they call it.
Superb, first time viewer, Now subbed. Thanks for the awesome vid! The graphics really helped nail the point down!!
Thank you so much, means a lot. Have a good day!
Yes! RW-pilot here who just found your channel and loves to repeat stuff I forgot! Great job!
Thanks!
Awesome video man! Really informative and underrated channel. Keep it up! 😄
Thank you so much!
Worth noting that because it is impossible to tell acceleration from tilt with no outside reference, instrument navigation is crucial for flying through clouds, low visibility, night, etc, or pilots could mistakenly fly straight into the earth, or at wonky orientations, especially when other aircraft failures occur. The gyroscopes are crucial, as well as altimeters.
A few crashes have happened because the pilot was damn sure the plane was rising, so they nosed down, right into the ground/water, when they should have just trusted the instruments.
Very interesting video! What I didn't yet really understand is why the whole platform needs to move.
Can't you just have 3 Gyroscopes by which the orientation is being provided (which is basically the direction of the vector of the acceleration of gravity) then take the data of the accelerometers and subtract the gravitational acceleration from the resulting vector? Aren't moving parts also usually more error prone or maintenance intensive? What am I missing?
I'm delighted that you ask this question, because it's exactly the same conclusion engineers came to when digital computers started to become available!
Modern systems do exactly what your intuition says: they correct for gravity by subtracting the vector through a computer. There is then no longer any need for moving parts at all, and this removes a lot of problems related to precision and accumulation of errors (exactly as you said).
At the time of the INS shown in the video, computers were not yet available/compact enough (not sure which), so everything was done mechanically and through voltages in wires. This essentially was "the computer".
Hope this makes sense, and the fact that you came to this conclusion by yourself means you thoroughly understand the essence of the topic. Have a good one!
This is a very clear explanation of an INS-- wonderfully presented.
Ok dude, these are exactly the videos I've been searching for for quite some time. This one alone made me subscribe within a few mins. Great work thank you
Thank you so much, very happy to read this.
Amazing way to simply explain this complicated price of hardware!!
Very good video. I wished you spent some time also to explain how to measure position from acceleration (integrating)
Thank you! In hindsight, it is something that I could have spent some more time on. Thanks for the feedback.
As a keen sailor and a person interested in space exploration, this is a fantastic explanation of an intriguing piece of human ingenuity.
Thank you for this. No shouting presenters, just how things work. Perfect. Bit worried that the INS readout can’t spell acceleration though 😉
Oh, my bad!
I used to work on the Litton LTN-72 INS in the NZ Air Force as an Avionics Technician back in the early 1090s. Fantastic pieces of equipment.
Dusting them off doesn't count
@@billp4 A bit more than just dusting. I remember there had to be an exact number of drops of oil on each gimbal bearing after cleaning them.
1 more details about what is inside that system would be nice
2 how does it communicate with the main circuitry if each mechanical link is a gimbal ?
Slip rings. Same tech in your cars steering wheel.
I'm sorry. Like most, you get the name wrong. It is DED Reckoning, for Deductive. No deaths occurred in the creation of this practice. You are DEDUCING where you are by the recording of your position over time. Thanks for listening, and you can look it up...
Amazing video!
Thank you :)
My father was a guidance control engineer in the late 50s. He worked on gyro’s @ SPERRY RAND working on the Sidewinder missile system and the Polaris program. In 1962 He went to work for NASA working under contract @ General Electric to work on guidance controls for the Apollo program. In 1969 we moved to northern Va. where he worked @ the Navel Research Laboratory. He wasn’t able to tell us much about this job but what I gathered is that he was working on future missile systems for the US NAVY.
Thanks!
A few years ago I bought a gyroscope for F104 from a military surplus online store (the orange part). Now I know that it was not complete and that we even need two and even a platform. Nice video, I will study it carefully.
Flat earthers dislike this video 😂
Having never seen this before, it’s quickly plainly obvious what it’s doing, but that’s friggin amazing that it can be so precise just based on force and orientation
This explanation is terrible. You cannot talk about Inertial navigation without explaining the relationship between acceleration, velocity and distance and the mathematical operation of integration.
Understanding that is fundamentally essential to understanding the principe of inertial navigation.
Why do we measure acceleration? What do we with the electrical signals output from the accelerometer?
This kind of video is misleading and it is not teaching the basic principles.
Seems like you're interested in the technical aspect of things. In that case the video is not for you.
@@RawbLV Understanding why acceleration is measured isn't really a technical aspect. It is fundamental as to why the inertial nav system works.
It is like producing a video to explain how a quartz crystal watch works without explaining the role of the quartz crystal. It is that fundamental.
@@deang5622 You said you want maths, this video is not for you.
@@RawbLV You obviously don't know the principles behind inertial guidance, do you?
To explain how inertial nav systems work means you have to explain the relationship between acceleration and distance.
Initial nav systems *MEASURE* acceleration so they can then *CALCULATE* distance.
The relationship between acceleration and distance *IS* mathematical!
Therefore you *CANNOT* adequately explain how inertial guidance works without explaining why acceleration is measured, what the purpose is *AND* the relationship to distance.
Come back to me when you *TRULY* understand this subject.
@@deang5622 That should have been your initial comment.
As a guy who watches a lot of TH-cam videos, your explanation is excellant :) GOOD JOB MAX !
I worked with these systems in Naval Aviation in the early 70's. I felt pretty accomplished since just two years earlier I was delivering electrical supplies to construction sites after high school.
Both lead to a long career in the electrical trade. Thanks to all involved!
Couple of things: The item displayed is a "Twin Gyro Platform (TGP)" it provides the inputs to a Navigation computer for integration with time to get velocities and distance. The TGP not only has to maintain level but must also point True North (the Accelerometers provide N-S and E-W acceleration into the nav computer, which then calculates Lat Long, distance traveled, course etc. ). During start up the TGP senses the earths rotation to perform a levelling and TN alignement (helps if you know your starting Lat, Long).
Limitations of the TGP - Does not like to climb vertical, nor travel over N or S poles (gimbal lock).
Before MEMS, accelerometers used a taught steel wire with a weight in the middle of the wire. On each side of the weight, the two sections of wire were kept vibrating (like a guitar string) using electromagnetic feedback. The cycles of the vibrating string on each side of the weight were fed into a counter - each cycle on one side of the weight caused the counter to count up, and each cycle on the other side caused the counter to count down. Under no accelleration, each side of the wire is vibrating at the same frequency and so the number of "up" counts over any time period equals the number of "down" counts and the counter stays at zero. If the wire was accellerated at right angles to the wire, then the frequency of both sides would change by the same amount and the counter will still stay at zero. If however there is a vector of accelleration along the same axis as the wire, then the weight causes one side of the wire to get tighter, increasing its frequency, and the other side to go slack, decreasing its frequency. Thus the counter will no longer get the same number of up and down counts, and its count (+ve or -ve) will equate to the total accumulated accelleration experienced along the axis of the wire since the counter was last cleared.
This is probably the coolest explanation engineering video I've seen 2 date
Thank you!
The British AS90 self propelled gun has been using a similar system since the 1990 onward. Brilliant system.
Wow!! Extremely well done and well explained work! Thank you very much for making it available to the world!
Thanks!
thanks for the video.
as a biomedical engineer I just want to point to something in the video : humans can tell if they are tilted because we have the inner ears that does the same job you're describing for us, except at much higher real time speed to keep us balanced too. (being bipedal is not that easy). so yeah our bodies don't have that limitations, it just too natural for us we don't pay attention to it.
Your vestibular system (inner-ear) is sensitive to angular acceleration, which is a rotation over time. If your orientation does not change over time (zero acceleration), your inner-ear won't be able to tell you if you're tilted or not. Thanks!
@@FlyByMaxsorry I fail to understand your point.
is there a case where the body(or the head at least) can tilt without it changing orientation during flights?
@@aymenninja8120 You're right, to change orientation means an angular acceleration must have occured. My point is this: after a certain amount of time of constant orientation/angular velocity, your vestibular system no longer senses any input. Imagine sitting on a chair with your eyes closed and rotating at a constant speed. After a while you won't be able to tell you're rotating. This means that we must still need an external reference (e.g., eyes, or in the video - a gyroscope) to figure out our true orientation. Sorry if I misunderstood your comment, have a good one!
Well you got the explanation about the ship's 'log' a little backward. They didn't time how long it took for a certain number of knots to be pulled over the side, they did the opposite. They threw the end of the rope over and turned an hourglass. Then counted the number of knots that went over the side in a fixed amount of time. (that is, the time was always the same and the ship's speed would determine how many knots were paid out.
P.S. The end of the rope had a small triangular piece of wood that was rigged to be pulled facing into the water to keep that end more or less stationary. After the measurement, a sharp 'tug' would pop a little peg out and let the wood turn edgewise to the direction of movement so it was easier to pull the 'log line' back in again. :)
That was so well explained, knowing nothing about this type of system, I now have a solid basic understanding.
Thank you very much sir.
Thank you!
I’m studying for my ATPL exams and this really helped me. Thankyou!
When I started work on my first job (aquiring data from oil boreholes), we had an instrument in our toolstring that used accelerometers and magnometers to determine the deviation and azimuth of the toolstring. Then, once the data aquisition, is complete, we could process the data into a true vertical depth format, instead of measured depth.
@07:30 no, wrong. you can tell if you are going on flat road or hill, because the CG changes with direction of gravity force, thus your senses in ear and body sense change in acceleration wrt CG.
One of mankind's greatest problems solving inventions. Made many travels possible!
Ive always been amazed by this technology, requires no external help or signal of any kind. Certainly not nearly as accurate as newer technology but its SUPER reliable and ingenius.
I worked on spinning mass gyro INS systems on F4s. It amazing what we do today compared to back then. Except ours was a two gyro system that stabilized the platform. The accelerometers measured the movement of the aircraft and the separate analog computer did the navigation calculations.
Later after college I was a naval engineer and I worked on fiber optic gyros that do the same basic thing that lasers do now. But you can wrap many layers of fiber optic cable around the optic path such that the light goes much further and the phase difference is more accurate. Then I worked on EGI embedded GPS and a INS in the same system. Lots of stuff going on.
One problem that is not touched upon is gimbal lock. This will basically occur when gyros axis start to align.
Excellent video! I was worried that you made a fundamental mistake by stating that the stable platform would always remain level with the horizon early on in the video, but you’ve covered that wonderfully in the last chapter.
The inertial measurement units used on the Apollo lunar modules had issues caused by apparent drift when after they were shut down to save power on the surface. The moon would rotate during the few days spent on the surface and caused the IMUs to not know which way was up when they were restarted. The engineers solved this by detecting the acceleration caused by gravity and a star sighting to correct for any errors caused by uneven terrain.
Thank you! I didn't know that about the Apollo IMU's, thanks for sharing :)
Excellent video for those who are not experts in this field, great to watch and really well explained.
Thank you so much, means a lot.
02:30 I have to tell you exactly where your Dutch sailor is - and he’s not leaving Amsterdam……
Your inset is a schooner departing Portsmouth Harbour (that’s Hampshire, England) about five miles from whee I am typing this and it’s heading south with the Isle of Wight in the distance and Spit Sand Fort some 500 metres off the vessel’s starboard bow. The three masts that you see slightly closer are part of a navigation system for our Queen Elizabeth class aircraft carriers and they hark back to an even early method of navigation using “transits”.
That is one of the greatest inventions mechanical over software I have ever seen. It might be one of the most important inventions in the future. Amazing true amazing!
Best and simplest explanation of INS/IRS,outstanding
Thank you!
We used to call it; the missile knows where it is by knowing where it isn't. Great video, thank you!
Wonderful article. Complex enough to understand things but not so complex that it confuses things. However, there are a couple of things I'd like to comment on.
As remarked by several others, I am sure that this INS was not on the F-104; that plane was much too early for this type of system. As stated by others, it was used on the F-4C and later versions of that plane. I think it was the first widely used airborne INS.
In the mid to late 60's I taught the ASN-48 and ASN-46 navigation system at the Air Force technical school at Keesler Air Force Base in Biloxi Mississippi. At that time I knew a lot about how the thing worded, but alas a lot of that knowledge has disappeared with time. One thing I do remember is that the gyros and gimbals communicated their positions to the rest of the aircraft's avionics by using resolvers, which were analog predecessors of our current digital encoders. As stated in the video, the accelerometer outputs were integrated in analog electronics. These signals were then used to move motors which turned shafts that provided mechanical analogs of N and E velocities. Subsequently the velocities were fed to an additional stage of integrators (and motors and shafts) which produced position readouts.
One question that I saw several times in the comments was about gyrocompassing. That was part of the system startup and calibration. I have forgotten the exact method, but it worked something like this. If the stable platform was not exactly aligned to N, then one of the corrections sent to the azimuth axis would cause the platform to slowly tip. This error was detected by one of the accelerometers and was fed back to the azimuth axis to rotate it to North. When the azimuth was closer to N, then there would no longer be a tip and the correction would be stopped and the system would switch out of gyrocompass mode and into the normal operating mode. (or something kinda like that!)
Keep up the good work!
Nice! Just to emphasise, the accelerometers measure a change in velocity or speed in a particular direction, not the velocity. The velocity is determined from the initialization of a zero point along with the additions (and subtractions) of accelerations in three directions along the route. The gyroscopes keep track of the direction changes made during the route. The computer keeps track of all the data and gives the location at any point along the route. Thanks for this great video!!!
Thanks!
After a 12 hour cross pacific flight, my INS position was over 100 NM off, about 3.5x over allowable limits. All depends on how well calibrated the system is though
Thank you for taking the trouble to create this truly excellent video.
I can't begin to imagine how much time and effort it must have taken, but perhaps not quite as long as it took to develop the LN3-2A itself!
Would it be fair to say that the gimbals solve the trigonometry equations which could not be solved using computers and data acquisition available at the time?
As a previous comment notes, laser ring gyros and modern microprocessors allow a strapdown solution with no moving parts, like motors, slip rings and synchro resolvers.
Far more reliable and accurate and (relatively) lower cost I'm sure, but now there is nothing to see - no inspiration. Like electric motors vs steam engines!
I believe that there was an even bigger, heavier control system attached to the platform and this comprised gears and electronics to process the signals for presentation to the pilot / navigator.
I have some pictures and diagrams if anyone would like to PM me.
Amazing explanation! Now, how to calculate Pitch, Roll, Yaw in a simple Trig example. 🥳 Thank you.
Of interest to watchers of this video is that three people were formally recognized for their contributions to basic science leading to success of the Apollo program and moon landing. They were Wernher von Braun for rocketry, Dr Robert Cannon for development of the inertial navigation system for Apollo, and Margaret Hamilton for the computer system that controlled the flight. In 1969, I was an undergraduate at Stanford and took Engineering 104, “Dynamics of Physical Systems,” a course taught by Cannon. In fact, he authored the textbook used in the class. He announced at the beginning of the course that he would give anyone a dollar for each typo we found in the book. I think I found the most. We developed a nice friendship, and he even invited me to his home for study help. What a great guy!
The feedback part was neatly glossed over as basically "magic".
I didn't even know about the problem before and an actual explanation on how the feedback works would have been nice(I suspect it's just a filter -- very low frequency signals come from the Earth's rotation as the Earth is rotating "slowly" relative to the aircraft's movements).
The fact that somebody took the time to make a video on the subject alone not to mention actually getting everything correct showing that they have the understanding of what they’re talking about not to mention the presentation alone pretty much to me I feel like would aid in educating somebody whether they were looking for this subject or had an interest in aerospace engineering or engineering alone this video was to me a combination of a documentary as well as a “How to” I know how to video really isn’t what I’m trying to explain but overall just gives a clear understanding therefore you got yourself a new subscriber! I look forward to seeing what else you cover on top of that I wouldn’t be shocked if you reach 10,000 subscribers either on or before the first of the year and hopefully sooner but 100 K by the end of next year!
Thanks!
The guidance system knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation. The guidance system uses deviations to generate corrective commands to drive the missile from a position where it is to a position where it isn't, and arriving at a position where it wasn't, it now is. Consequently, the position where it is, is now the position that it wasn't, and it follows that the position that it was, is now the position that it isn't.
In the event that the position that it is in is not the position that it wasn't, the system has acquired a variation, the variation being the difference between where the missile is, and where it wasn't. If variation is considered to be a significant factor, it too may be corrected by the GEA. However, the guidance system must also know where it was.
I think these explanations are an attempt at (not bad) humor. You say, "By subtracting where it is . . ." If you know where it is so that you can do the subtraction, why bother? You already know where it is.
New to this channel and i can say it is going to grow rapidly thanks to this great content
Thanks!
So much wrong here. We (mariners and pilots) still use knots (Nautical miles per hour) because a nautical mile is 1/60th of a degree of latitude. This makes it easy to estimate things using the formula 60D/ST. Early ship crews tied knots into the speed log line to do the measuring, so Nautical Miles per hour got shortened to Knots. Early explorers made ocean travel navigation using early versions of the sextant (a tool to measure angles) to keep themselves on a latitude line. Each day at apparent noon the navigator would do a noon sight of the sun at its apogee. This angle of the sun off the horizon plus some simple addition and subtraction would give the navigator their latitude. If during the previous day they drifted off course from wind or current, they could correct over the next 24 hours. A good navigator could keep the ship within a few miles of a latitude line on a weeks long crossing. A trip east or west would start with the ship travelling north or south along a coastline until they reached a specific latitude across from their intended target across the sea, then the east or west travel would begin, using a chronograph to keep time, plus the speed log and DED Reckoning (means Deductive) to estimate position. Folks who don't know any better call it dead reckoning. All of these errors and misconceptions in the first 4 minutes make me wonder how much of the rest of your video is in error... Read "Carry on Mr. Bowditch" and "Longitude" "Celestial Navigation" and "The American Practical Navigator" "Chapmans" is good too for more basic and comprehensive boating knowledge. Now-a-days all this is computerized, but we still have a compass, chronograph and Sextant aboard, along with the tables to make it all work.
The best explanation over internet.
Used to work on older INS gyros. I can't count how many times they wouldn't spool up and the fix was to literally remove the box from the frame, drop it about 12 inches on the ground and reinstall. There was a tech fix involving a rubber mallet but dropping it did the trick 95% of the time. This saved the US taxpayers untold fortunes in back-shop repairs.
There needs to be more videos about the INS because it is such a revolutionary system!
When aligning, that is the ONLY time you need outside input so it’ll work in conjunction with stuff like synthetic vision and EGPWS. But that’s it.
You can lose all VOR and VFR stations, all GPS satellites, and all your comms and still be able to go wherever you want without an issue.
Extremely interesting video.
As other peoples said, modern ins uses either laser gyros, based on the sagnac effect, discovered before restrained relativity, but easily explained now thanks to it, or a new technology is based on the oscillating deformation of a glass cup, initially caused by piezzo electricity, the cup acts as a pendulum which oscillating planes doesn't change despite the rotation of the support (Foucault's pendulum)
Excellent video! The graphic demonstrations were fantastic! Thanks for posting.