@jchigeagl When the explosion happened with Apollo 13 did you guys hear it in mission control, as I've watched videos on both RU-vid and Netflix where I beleive I heard something that sounded like and explosion?
Well done! I worked on SkyLab in crew training & flight simulation in the early seventies. We used the Apollo command module to get back and forth to SkyLab. We (and the back up crew) flew the simulator in parallel with the live mission, and would try out problem fixes before the primary crew to ensure no ugly unforeseen consequences. BTW: flying your girlfriend around the moon on the weekend worked every time! Keep up the good work, great video!!!
I am so glad that I came across your channel!! I am currently a Masters student, Aerospace Engg. And like you'd know, none of this, is taught- I learn more through your videos, than at school, about Aerospace! Thank you so much!! you're doing a wonderful job, and I couldn't be more grateful!!! Wish you the best!!
Nice explanation! Gimbal lock is not just something physical, it can also happen in software simulations, like games, where the rotation is represented with rotations in three dimensions. However, most games these days use what is called quaternions to represent rotation, which is essentially the "fourth wheel" that is shown in this video. :-)
Yup. Quaternions can be represented as four components, with one constraint, and so three independent degrees of freedom. Same information, represented a different way.
Quick note, guys. Frank O'Brien who wrote "The Apollo Guidance Computer" pointed out a little error on my part. Gimbal lock on Apollo was possible with the inner and outer gimbal lying on the same plane, the gimbal mounted on the central platform and the one mounted to the spacecraft. Those are the two you really don't want to line up!
Yes Gimbal lock is a bad thing. I remembered that in Avionics tech school. Thanks for the video. Thanks for the Inertial Measurement Unit and other buzzwords. BTW does your cat knock over your effects that you have to retake a video or scene?
I was an avionics mechanic for a regional airline back in the 2000's. Our "INU" was about thr size of a shoe box and didnt use gimbel exactly. I was at the Space and Rocket Center a few months ago and saw these. It's so cool seeing how the technology started out, and how its matured.
Hey Amy, very well explained. I'm a commercial pilot and during my first steps of my formal training in the aviation, I got noticed about what a gimbal is and importance of understanding what presession force is, etc., but certainly when they in the movie talk about gimbal lock, it comes to mind a number of conclutions. Your explanation is so good. Thank you.
Thank you for your wonderful recommendation on 'How Apollo flew to the Moon!' I love it! Exactly the book I have been looking for, with just the right amount of (technical) detail.. I was 11 years old, watching TV, when Neil Armstrong set his first historical step on the Moon. Keep up the good work!
Your cat jumped off your desk just before mine jumped onto my desk. Really confused the hell out of me. Also... great videos, really enjoying your channel!
I remember some PC flight simulators could get gimbal locked by pitching up to vertical, then rolling 90 degrees. Bingo, you could no longer pitch up or down to return to the horizontal. You could only yaw sideways. Anyway, I gather everyone uses quaternions now for rotations.
Thumbs up for lean content served quickly with zero fluff. Strong eye contact, facts recited clearly, video length cut to fit my attention span. Well done!
I wasn't the lead retrofire officer, because I was 8 but I remember watching the landings on the moon, and I appreciate your videos too ! And your as cute as a bug's ear !
Interestingly enough, it was reading the transcripts from the Apollo 11 mission where Collins asked for the fourth gimbal for Christmas which then lead me to look up “gimbal lock” which lead me to this video. Thank you for your concise explanation.
This video right here, if I remember correctly, was kind of pivotal in my interest in the Apollo program. Here's how: First, it inspired me to watch Apollo 13, this time actually having a better idea of what's going on. Next, it made me research the Apollo guidance and navigation system (because I thought gimbal lock was pretty interesting). Eventually I discovered things like the Apollo Operation handbooks and Apollo flight journal. At the moment I'm reading the journal, Apollo 12 is nearing lunar orbit insertion. Keep doing what you're doing!
Great post, informative as always. I followed the space program closely growing up and I'll never forget that week, when Apollo 13 was in trouble. It was like a miracle when they splashed down.
What a great channel! Can't believe I haven't stumbled across you before. You really have a gift for being able to explain complex concepts in a way that's easy for the non-engineer to understand. Keep up the brilliant work.
Owen Garriott was Capcom when Michael Collins made his request for a fourth gimbal. I asked Owen a few years ago if he remembered the exchange, and he didn't. He was unaware that the exchange had been so widely quoted in explanations of gimbal lock!
I know this sounds weird and you have heard it before but you are not only really smart but beautiful too. You are a gifted teacher and I love watching your videos. Thanks Vintage Space girl!
Thanks for that explanation Amy. If I recall correctly, ultimately their efforts to avoid gimball lock (essentially messing up the calibrated settings) were moot when they shut down the command module to save the battery. The lack of power would have allowed the gyros to spool down and the settings were lost anyway. At least that's what I remember, it's been a while since I read the book. Also if I recall recalibrating the IMU during the CM powerup was difficult because the window with calibrated markings that the crew would use to align the spacecraft with certain stars was frosted over from the O2 tank explosion making vision difficult.
Don't have time to read through all of the comments but just throwing this out- the inertial system measured not only angular displacement but angular (or axial) acceleration. I'm a sleepy retired Delta Captain but I did do (on loan from Delta) consulting work for NASA. It was the MLS business back in the '80's at Ames Research Center. Thanks for your work.
Thank you for this. I knew how gimbals were an important part of their navigation but was having a hard time visualizing how they registered outside until you showed with the model CM/LM. Also kinda thought gimbal lock for 13 would immediately make the ship look like when you’d shoot down the helicopter in GTA III in 2002. So yes, that’s a big help. Thanks!
+Amy Shira Teitel (Vintage Space) I know this is off topic a bit but I've noticed on some videos of the base of a rocket before it takes off that a bunch of sparks are shot underneath the rocket before it lights up....why is that?
Petey Wheatstraw While waiting for her reply, I'll give my response, if you don't mind. If I'm not mistaken, I was under the impression the sparks were used to initiated the combustion of the fuel. Again, I am only offering conjecture.
+The Dude the sparks are there to remove any excess hydrogen before the liquid rocket ignites, in order to prevent any accidents. not, as I used to think, to ignite the rocket ( there's a programme called secret space escapes that explains it in more detail)
I got the gist of it. Mostly the video was like "if a 4th gimbal.....OMG she's gorgeous........yaw and pitch....OMG she's gorgeous". Human beings can't be this well spoken, this gorgeous and this smart. She should be tested for alien DNA. She might be one of the moon people. No but seriously, good stuff. First saw you on one of those aliens on the moon things on Netflix and ended up here. Your videos are fantastic. Russian photos of the surface of Venus? Mind blown.
You are beautiful and a brainiac! I've had the honor of having lunch with Jim Lovell right after the film was released. He said the film was quite accurate - with the exception of the hollywood-portrayed tension with Jack Swigert - Lovell said there was complete faith in all the crew.
Sutterjack Not to mention other tensions and extended burns not present on the flight. Swigert wrote the emergency procedures for the CM, so he was the best possible CMP to have on that flight. Good thing T.K. "Ken" Mattingly got exposed to (but never got) measles. ;)
Wow! thanks so much for that... really great delivery without losing me technically speaking in such a technologically intensive topic! Look forward to more interesting stuff from you!
Ironically, Gemini (Apollo's predecessor) had a 4th gimbal to avoid lock (as was referred to in the post). In Mike Collins wonderful book "Carrying the Fire", Collins laments that the McDonnell's learning from Gemini was not adopted by North American Aviation Apollo design. He laments this fact that there was a bit of 'not invented here' attitude (NIH) or "we don't do it that way in Apollo".
Weight and added slop, however small, of yet another gimbal. Gemini was just orbiting the earth, but Apollo couldn't afford the precision loss of one added gimbal. And the weight.
+Andrew Gwilliam *" Why would a 4th gimbal mean the instrument was less precise?"* The gimbal assembly is a series of gimbals, one inside the other. Granted, they obviously use very high quality bearings but are not _perfect_. Since all the gimbals are one inside the other, whatever slop or backlash each bearing has is added to the next gimbal, so the total play is the sum of all the bearings' individual backlash or play. Adding a fourth gimbal will add to the total play or backslash, making the gimbal that much less precise.
thnxx for this vid.. me,living in the netherlands watch it and learning each time i watch a video from you.. i became facinated by the apollo program ofcourse thru the motion picture apollo 13 but also by de docu moon machine.. with a special episode about the saturn 5.. its amazing piece of machinery made in the usa... good luck and work and me,enyoying your vids .. 😊
I LOVE that AGC book! The computer architecture bits are a little thick, even though I like that sort of thing, but you can skip them if your eyes start to cross. The best part is the program-by-program description of a trip to the moon and back. It gives you a really good look at all the steps of a flight and explains what's going on outside the computer along the way.
You did a good job explaining the concept, but trying to imagine what it would be like to someone who doesn't understand this already it's not clear that some people are not going to remain confused. You might need a whiteboard and some drawings to get everyone up to speed. By the way, how does your cat NOT knock everything over?
USWaterRockets That's true, and if I had a setup for something like Minute Physics does it would be great for this kind of topic. Alas, all I have are my models. And sadly couldn't find any good vintage NASA animation to go along with it!
Amy Shira Teitel WaterRockets does make a good point, the presentation was fast paced and information packed. However, I'd rather watch your kind of video and be slammed with data than other science documentaries where info is s-l-o-w in coming and dumbed down to boot.
In a more mundane application, also from the sixties, they used a partial, 4 gimbal system. The Litton LN3-2A Inertial Navigation platform as used in the F-104 Starfighter and F-4 Phantom used 4 gimbals: - Outer Roll Gimbal (rotates over 360 degrees) - Pitch Gimbal (rotates over 360 degrees) - Inner Rol Gimbal (Can only rotate left and right over a limited range) - Azimuth Gimbal (rotates over 360 degrees) A bit more complicated, but it could prevent gimbal lock.
Thank you! Thank you! Concise and to the point PLUS reference material - FANTASTIC! - now that IS a proper RU-vid channel! Keep up the FAB work! And cheers from the U.K.! X! Subscribed!
Amy, this video made a lot of sense to the sailors and IMU users (like stabilized video camera operators and pilots), but I suspect many have watched it and tried to figure out what the heck a gimbal *is*. I learned the word in the kitchen of sailboat, where items that must stay upright when the ship rolls (like stovetops) are often on gimbals.
Ive popped in on your videos from time to time and found them interesting and informative. Ive been enthralled with the early space program as a kid. Im now a subscriber! Looking forward to more!
Excellent explanation. Thank you.. Oh and thanks for the book recommendations too. PS: I think I spotted Pete talking a stroll around your Saturn V :-)
here's an interesting one you may want to sink your teeth into," mercury 13"...the subject is becoming very relevant on long duration missions..nice little tidbit of vintage space
you can illustrate the phenomena with a simple compass. - hold the compass base (plate) horizontal to ground. the needle shows (magnetic) North and you can read your bearing in degrees due to North. OK OK we all know this :) - then hold the compass base vertical (i.e. pitch the compass 90 up in Apollo terms). the needle will struggle to show North and you cannot get a reading. - at this point the needle is LOCKED. you can roll the compass as much as you want.... everywhere is North.
I m not sure if I understood you correcly... three gimbals on three axes (x, y, z or roll, pitch, yaw) will lock at some position as well as one gimbal on one axis at some position. thats not multiple gimbals in three dimensions. solution is a fourth gimbal (properly positioned of course). perhaps you were saying this...
I didnt say all 3 gimbals are locked into each other, srry if it sounded that way, an INS with 3 gimbals at 3 axis will lock at some position, solution is a fourth gimbal, thats what I was saying,
You show the AGC display flashing digits and the keypad beneath, called the DISKY (display keypad). Well, it was my own dear dad who came up with the wiring harness to make the DISKEY work. Andrew Sullivan worked for Raytheon corp who had a contract with the space program, and they could not make a wiring harness that could withstand the rigors of space flight. The story goes that Andy Sullivan believed he could design such a harness and took a weekend to work on it. Monday morning Sullivan presented the wiring harness to his boss by slinging it over his shoulder and plopping it on his desk, fully intact and operational. Just a bit more arcane knowledge that is certainly more than anyone wanted to know :-)
Most of the time gimbal lock would not have been a disaster on Apollo, just a major hassle as the crew would have to realign the platform from scratch using the stars as a reference. It *would* have been a disaster (or at least a very serious problem) during a time-critical mission phase like powered flight, and it would also have been a big problem during Apollo 13 since there was too much debris around the spacecraft to sight any stars.
The Gimbal Lock Warning light told the astronauts they needed to rethink the way they should reorient the space craft when preparing to fire the main engine of the CM or LM (called a Delta V burn). They would have to rearrange the sequence of vehicle rotation using pitch, roll and yaw commands. As the comment above indicated. if they entered gimbal lock they would lose knowledge of the stable platform orientation in the IMU and they would be required to take sightings off known stars (and/or the earth, moon or sun) in order to reestablish that orientation. (The stable platform was the ONLY way they could tell what was "up", "down" or "sideways". That was required in order to point the vehicle in the right direction to make course corrections...So knowing the orientation of the stable platform was EXTREMELY IMPORTANT.)
You are an amazing space nerd Amy. i've seen apollo 13 what 4 times and i have always wondered about gimbles.....and to think about it a 4th gimble makes so much common sense. Yes those were the times that sometimes common sense juat got tossed out the nearest airlock.
its silly i know, and i'm sure everyone says it, but YOU are an awesome woman. thank you for a very cool and informative addition to this occasionally very crappy internet. it soo does NOT suck. hahaha!!!! love the cat. make him a star too!
Thanks for such a simple explanation, i was wondering about this whilst trying to figure out how to make a working 1/6 scale attitude indicator for a project. I think mine will only indicate roll.
we had gimbals on the BIAS system. We could detect a hiccup, flat spots, and even weigh the train while it was crossing the bridge. Those were the funnest days of my life, other than as a little kid watching all of the Apollo missions back in the 60s. I would give almost anything to be there again. All of the family was alive and healthy. train sets, microscopes, telescopes, brothers, sisters, mom , dad. life was a hoot!!!!! Then I turned 13 and everything went to absolute hell!!!!! I had no idea that life as a disabled vet would be like this. The family games of keep-away, the water fights, the giant innertube fights, out milkin' the cows in the snow at Christmas. My mother could decorate Christmas like no other, goin' for rides in my dads new cop car at 130 MPH chasing drunk drivers. I ache to be with them all again sitting there watching them land on the moon during the dog days of summer. That was a hell of a good life!!!!!!!!!!!!!
+David W Each ring in the apparatus is itself a separate gimbal. The navigational device is an apparatus comprised of 3 (in Apollo 13) or 4 (as described to avoid gimbal lock) connected gimbals, and navigational equipment mounted to the inner-most gimbal. A gyroscope is a spinning core (important for gyroscopic actuation) mounted to the inner-most gimbal of a multi-gimbal apparatus. The relationship between a gyroscope and a gimbal is akin to the relationship between a doorway and one of its hinges.
My dad worked on the 2nd stage of every Saturn V that went up and taught me all about it. That said, the one thing that made me laugh about Apollo 13 was that Tom Hanks went through 1st staging and then jettisoned the tower as per procedure. After this, a center engine cutoff occurred and, while he's waiting for Houston to tell him what to do, he's looking down at the abort handle. When he did this, I began laughing and my wife asked me what's funny. I told her that I don't know why he's looking down at the abort handle because he has already jettisoned the tower so if anything happens now he's screwed.
Ya'll are making a gimbal lock event out to be much more dramatic than what it really is. If the spacecraft is coasting (i.e not under powered flight) NOTHING is going to happen, except that they obviously will not know where they are pointing in space. That is easily rectifiable by performing a P52 IMU alignment, (although it was a little bit time consuming) which they routinely did, during the mission. A gimbal lock occuring during TLI/TEI, MCC, DOI is obviously something that you wouldn't want to happen, but if it were to happen during a coasting phase, it wouldn't be critical.
It was dramatic because if they went into gimbal lock while they were trying to correct after the oxygen tank exploded, they would end up flailing around wildly and without the information they'd need to fix the problem.
Apollo 13 was venting into space, so it was as if they had an engine running with no way to turn it off. If they went into Gimbal lock then it would have been terrible.
They can and did realign the guidance computer during 13, but they found it intensely difficult because, if I recall correctly: - they were venting stuff that obscured the stars they were trying to align to - the LM had a fixed sextant, so they needed to align the spacecraft to the stars, and LM wasn't designed to maneuver the command and service module -- they kept coming close to gimbal lock while trying to do this - the astronauts were frozen and exhausted
Not just that they were venting into space, they were venting on an unknown axis, at an unknown and non-constant rate (and thus thrust). Maybe it wasn't "critical" because the SM engine didn't rocket them thousands of miles off course, but if they weren't able to stabilize the spacecraft, they would have tumbled off into oblivion, or into the surface of the moon. The net effect is the same here regardless.
I think you are talking about the RCS (Reaction control system) nozzles. Several engineers at the Cape had rejected ones on their desk as pencil holders. I was to able to get one.
"Gimbal" is another word for a powered, motorized gyroscope- a specialized metal disc or ring spinning very fast. In short, any object (alive and not, big and small) moving in our Universe _must_ do so along three invisible lines running perpendicular to each other, the so-called X, Y and Z-Axis (aka "pitch", "roll" and "yaw"). The _Apollo_ guidance system uses the IMU to detect the slightest movements to the spacecraft. (I promise I won't use any big scientific words in the following, since I am neither scientist nor engineer.) Here on Earth, we humans (and many other animals) have our inner ear, which has three very tiny hollow tubes with fluid that freely moves through them. When you turn your head specifically, the liquid in those tiny rings moves, and even-tinier hairs inside of each tube detects the motion and then tell your brain "Yo! You're movin', dude!" Well, things get significantly more complicated when you move into outer space, away from the influence of gravity. While inertia alone still can move the fluid in your inner ear, the loss of gravity disorients you and the signals coming from your inner ear _don't_ match up with what your eyes, skin, nose and other senses are telling you; your body has not evolved to understand movement _without_ gravity. (NOTE: there are a number of movement-sensory disorders out there- among them seasickness, airsickness and vertigo- so this does not work perfectly in everyone nor all the time.) The same thing applies to a spacecraft. How does it know which way is the correct direction to point, since there is no "up" or "down" in space, and the distances between anything are stupidly, unimaginably huge!? The _Apollo_ IMU used three high-speed gyroscopes ("gimbals") which were deliberately pointed in different directions, just like those inner-ear loops inside your head. You know how when you have a single spinning gyroscope in your hand, and you feel resistance anytime you try to move it? The IMU does _exactly the same thing-_ it detects those tiniest of changes to the directions of _all three_ gimbals at the same time. So, for example, if the spacecraft turns slightly to the right, one of the three dedicated IMU gimbals will notice the change and inform the navigational computer of such. The IMU is setup to begin measuring motion just before launch, and will continue to do such until either the end of the mission or the spacecraft is discarded. So, with all of this said, what Amy is trying to tell us in the video above is that there was a very real risk that if _Apollo 13_ turned in more than one direction too quickly, the gimbals would _unintentionally_ line-up with each other ("gimbal lock"), thus losing their unique settings and the ability to tell the navigation computer which direction the spacecraft was pointing. On _Apollo 13_ in 1970, this was especially hazardous because _Odyssey_ (the Command/Service Module) and _Aquarius_ (the Lunar Excursion Module) were tumbling out of control for a significant amount of time, and if the astronauts were not _very_ careful, the three gimbals would IMproperly line up with each other and "lock", and the onboard computer would not be able to keep them pointed in the right direction. Once gimbal lock happened, there was absolutely no way for the astronauts to reset it while they were in space.
Gimble is a fancy word for not turning on the cameras inside the Command Module or LEM to show Jim Lovells great piloting skills in outerspace with no restraints to keep him from moving relative to the studio LEM because it was a a gigantic hoax.
I am practicing telemedicine during the 2020 pandemic. My cats are allowed into my home office otherwise they would tear down the door. Patients have said they are a calming influence. They do help me.
Somehow stumbled upon your channel here just now, Will need to see more, but you've got my gimbal locked. Drove down to Florida to see some launches, Four falcon nine night launches since christmas, And the falcon heavy which was spectacular. Just saw Axiom send four european astronauts to ISS the other day. Keep that cadence , SpaceX !
As a youth I spent hours in front of my remarkably small black-and-white television, and I was constantly barraged by Walter Cronkite who would hold up a basketball as if it was the earth, and then a piece of paper turned sideways, as thin as possible, while he warned us that that thin paper represented the margin of error and a tiny amount of space that was the target of incoming spacecraft which if missed would send the crew crashing to earth or spiraling off into another galaxy. Gotta raise the anticipation to keep the people watching. But of course Walter would never lie. :-) However the mention here of Apollo 13 brings to my mind the story or explanation of how the crew put up a target, or a cross in the window facing Earth, and used back-and-forth communications to fire the engines and properly align the ship so that it would be sure to hit the Earth at the precise, do or die proper angle, inclination, etc. Why do I have trouble believing that someone with basically a joystick, and another " reciting a countdown" was able to bring that spacecraft into perfect alignment so that it would hit that "paper thin target" dead on, from 100,000 miles away. :-) I'm not one who thinks it was all fake, but if I was a conspiracy theorist and I wanted some curious proof that it was fake, I might be harping on two men aiming a spacecraft accurately at Earth from so far away, by saying "go" "okay three, two, one" "stop!" It's a ludicrous notion and I think anyone who can think would laugh out loud at that part of the rescue. It worked. but also made a mockery of every reentry ever discussed or described by news reporters and NASA, in previous missions. perhaps take a moment and explain how the crew was able to hit that minuscule, critical reentry attitude, by guessing. I'm not saying I don't believe it, but you like to explain such things to people, so please expand on this point?it may not be as critical as we are led to believe, which doesn't make me think anything bad about NASA, but it was always a frighteningly critical point for me because so much effort was made to emphasize how easily the crew could be killed and the catastrophe that might follow. I never have thought that what we accomplished was that big of a technical deal. (I really am a design engineer, but that doesn't make me special)but I still don't think it's that impressive. I look upon NASA as utilizing the "use the biggest hammer you have, so even if you miss it will be okay, which is frighteningly expensive and misleading" as you have mentioned before the shuttle was stupidly over sized, and it's impossible for me to accept that after all the years and all those flights NASA was never able to convince oversight how ignorant it was to send a New York City Subway car into orbit every time. Keep up the good work I enjoy it :-)
Oh Gimbal Lock... And all this time I was thinking it was Gimbel lock, which was when the closed the department store for good. That clears up a lot of confusion :)
