Why Does a Rocket Need to Roll Going Into Orbit?

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[@jhgmusic]

I love this, most especially because my father worked for NASA as an engineer during the Apollo era and his responsibility was what we always called the telemetry ring, aka the instrument unit. It's always fun to point to that ring and state that my dad invented some of that. I recall them having trouble with some part of a circuit for several days and it was driving him crazy. He awoke in the middle of the night, sat up, and realized a diode was soldered in backwards. He was so excited that he went on into work, repositioned the diode, and tested the circuit, and it finally worked. That's his favorite story. Mine too!

[@ApolloWasReal]

Other commenters correctly point out that a roll maneuver is not, strictly speaking, essential to fly a given launch azimuth to a certain orbital inclination. The engines are quite capable of steering the rocket in any direction regardless of roll angle. The roll is necessary only if you need a particular side of the rocket to be down (or up) as it tilts towards its launch azimuth. There were three reasons this was required for the Apollo/Saturn stack. First, it kept the astronauts' heads down. They were trained to take over control of the Saturn V should IU guidance fail, and this attitude kept the earth's limb horizontal and visible in the windows. Second, it kept the many antennas on both Apollo and Saturn facing the earth. Some very important radios (such as the range safety destruct command receivers) had multiple antennas so one could always be seen from the ground, but many more telemetry antennas on all stages of the Saturn weren't replicated. Third, the inertial platform in the Saturn IU, like the one in the CM, had only three gimbals, meaning it was susceptible to gimbal lock. At launch time (actually guidance release at T-17 sec), the IU was aligned to the launch site REFSMMAT (the particular inertial coordinate system reference used at launch) so that the IU/IMU's outer gimbal (fixed in alignment with the vehicle +X (roll) axis) was pointing straight up, the middle gimbal was aligned with the +Z (yaw) axis pointed downrange, and the inner gimbal was aligned with the +Y (pitch) axis and completing a right-handed set. This put the three gimbals at right angles to each other, the "neutral" position. But if the vehicle were to yaw (rotate around the Z axis) 90 degrees to the left or right, this would align the outer and inner gimbals such that the IMU could not accommodate any rotation around the inertial X axis. This could tumble the platform and require a realignment, something you definitely don't want during a launch. So by rolling to put the +Z axis downrange, only the inner gimbal would rotate as the vehicle pitched down. The yaw angle remained almost exactly 0, deviating only slightly to steer out high altitude winds and staying as far away as possible from gimbal lock. Because the Saturn was fixed to the pad with the Saturn's +Z axis pointed almost (but not exactly) east, and the launch azimuth was seldom exactly due east, it had to await launch with some non-zero roll angle. For example, at guidance release Apollo 11 was rolled left (counterclockwise as seen from behind) about 18 degrees, so after liftoff it rolled right 18 degrees to make the roll angle zero for its launch azimuth of 72.058o , which is a little north of east. Again, this let it perform a pure pitch maneuver as it flew downrange. BTW, if you look this stuff up keep in mind the body coordinates of the Apollo CSM did *not* match those of the Saturn V. Their +X axes were the same, but the CSM was rotated 180 degrees around the X axis so that the CSM's +Z axis coincided with the Saturn's -Z axis and the CSM's +Y axis coincided with the Saturn's -Y axis. So just after the post-launch roll maneuver the Saturn's +Z axis and the CSM's -Z axis were pointed downrange.

[@bennylofgren3208]

I agree, an absolutely brilliant explanation. I would also like to add to Amy's recommendation in the video about the book "How Apollo flew to the moon". It is an absolutely amazing read and really a must for any space buff. It explains all of this and tons more, in fairly easy to understand exquisite detail.

[@bennylofgren3208]

Carl Charles Mando Atteniese Thanks but I think you're confusing me with ApolloWasReal who wrote the comment starting this thread. My comment was a bit vague, I see that now when rereading it. I didn't refer to Amy (except by +1'ing her book recommendation) but to ApolloWasReal. That dude knows his or her shit. :-) I apologize for the confusion! If you want to know anything about the hardware or software of the Apollo Guidance Computer however, then I can probably give you some input. That's within my special area of interest. Also, low level computer programming has more or less been my profession for the last 30+ years.

[@ApolloWasReal]

Thanks, guys. That's a more positive reaction than I usually get from the Apollo deniers that I sometimes spar with (hence my choice of pseudonym). I thought for a bit about how best to explain the IMU stuff, and I agree you can't really do it well without diagrams. I should have cited the references I used, primarily "Project Apollo Coordinate Systems" but also "Saturn V Launch Vehicle Flight Evaluation Report - AS-506 Apollo 11 Mission" (where I got the launch azimuth and roll parameters). Both are available through the NASA Technical Reports Service (ntrs.nasa.gov) and are probably mirrored elsewhere, so a Google search should also find them. If you're interested I could also find some technical documents showing the many telemetry antennas, mainly on VHF, on each of the Saturn stages to show how they had to face earth. I'm pretty sure they were all on the +Z side of the rocket, which is the side facing down as the rocket pitched down. BTW, that coordinate system (+X forward, +Z down and +Y to the right) seems to be the standard for aircraft navigation. The CSM coordinate system seems based on the terrestrial convention, which has the +Z axis pointed up and the +Y axis pointed left. Not sure why they did this, though. The main diagram to study is figure A-12 in the coordinate reference document. It diagrams the Saturn V inertial reference unit with its stable platform in the center and the three axes aligned at guidance release time as I described earlier. The IMU in the CSM was aligned the same way (probably rolled 180 degrees) in case it had to serve as a backup, but the IBM-built instrument unit (IU) never failed in any Saturn launch. The CSM IMU was periodically realigned to different reference systems (REFSMAAT) as the mission progressed but as far as I know the Saturn IU only ever needed the one launch site coordinate system since its job was over in a few hours.

[@bennylofgren3208]

ApolloWasReal You have commendable patience with those guys. I've taken on a few as well, but invariably I quickly come to the realization that it actually is less painful for me to bang my head repeatedly on a brick wall than continuing to "debate" with people who just simply refuses to use their brain. I cannot believe that there can be such cognitive disconnect in an individual as to just not get it, which means somewhere in there there must be willful ignorance at play. I guess for some, ignorance really is bliss... I for one would definitely be very interested in any technical documentation you have on the subject, but I know there's a treasure trove I have barely scratched the surface of at the NTRS site. I just wish I had more time, like a few decades, to just dive in there and read everything... :-) I am a software engineer by trade and have always had a fascination with the AGC, but IBM's Instrument Unit intrigues me as well, mostly because there is so little known about it these days. I don't think much of the original schematics, documentation or software has been preserved, for example. Which is a total shame, since while it is of a less technically sophisticated design than the AGC and its peripherals, it was still an awesome piece of engineering. I don't know if there is any truth to it, but I have heard that there is actually original core memory left in the unflown IU that is on display with the Saturn V at Kennedy Space Center, and that it might actually still contain the real guidance software for the unit. I would *love* to see if it is possible to extract whatever is in there, and see if it is possible to reverse engineer it. Unless I'm mistaken and there is relevant documentation on it still in existence of course.

[@ApolloWasReal]

Probably the best way to visualize the IMU gimbals and gimbal lock is the way the astronauts saw it. The "8-ball" on the console showed the orientation of the IMU platform relative to the spacecraft. The 8-ball behaved as if it contained a gyroscope; it stayed fixed in inertial space as the spacecraft rotated around it. (It didn't actually have a gyroscope, but it was driven by the computer to keep the same orientation as the real IMU gyroscope, so it was a "virtual gyroscope".) Pilots are already familiar with gyros in instruments like gyrocompasses and artificial horizons, so the 8-ball just took it to three dimensions. The 8-ball depicts a globe with lines of latitude and longitude. A mark in the center of the display depicts your current pitch and yaw attitude on the globe: pitch as longitude and yaw as latitude. Your roll attitude is shown as a rotation of the ball around your pitch/yaw point, which could be read from a scale around the circumference of the 8-ball. With the IMU in a "neutral" position, all 3 axes perpendicular to each other, the 8-ball has latitude 0, longitude 0 in the center with the poles at 9 and 3 o'clock. Pitching causes the ball to rotate around its polar axis, i.e., your longitude changes and your attitude point moves along the equator of the globe. This rotates the inner IMU gimbal. Rolling simply rotates the ball around some fixed point on its surface; it rotates the outer IMU gimbal. Yawing moves you north or south of the equator, i.e., it changes your "latitude". It rotates the middle gimbal. Note that "pitch" and "yaw" are with respect to the stable platform, so they match the body "pitch" and "yaw" axes only when you're at this neutral point. If you roll 90 degrees to the left, the ball will rotate 90 degrees to the right, with the poles at 12 and 6 o'clock, and what's pitch to you will be yaw to the 8-ball and IMU. It's the latter that counts for gimbal lock. The polar areas of the 8-ball were marked in red; these were the "keep out" areas to avoid gimbal lock, which actually occurred at the poles where all the longitude lines come together. If you yaw close to a pole, then a small change in pitch results in a large change in ball longitude, which corresponds to a large change in IMU inner gimbal angles. The closer you get to the pole, the greater this magnification effect until right at the pole it becomes infinity, and it's impossible to pitch the spacecraft without an instantaneous 180 change in longitude that jerks the platform out of its inertial position. That's gimbal lock. Because there's always some small amount of friction in the gimbal bearings, just getting too close to the pole can disrupt the platform because of that magnification effect. Roll maneuvers, which simply rotate you around the ball at a fixed point on its surface, appear to be safe at any attitude because the roll axis is the outer gimbal in the IMU. Pitch is the problem, and then only at high yaw angles. The coordinate system for the Saturn V IU/IMU was chosen such that after the roll maneuver, the 8-ball was in the neutral position. Then as it gradually pitched over and flew downrange, the attitude point traveled along the equator with the poles staying at 9 and 3 o'clock. If they maintained a local horizontal/local vertical orientation in orbit, i.e., heads down and long axis in direction of motion, the 8-ball continued to rotate around its horizontal polar axis with the attitude point always staying on the equator. All this kept the IMU as far from gimbal lock as you could get.

[@johnc.bojemski1757]

For someone who says she's"NOT a rocket scientist" Amy did great explaining this complex topic!

[@jimbarrofficial]

Too much science. My brain hurts. I just like the loud noises and fire.

[@redcorvetbule7136]

U

[@julian.castro18]

I can relate

[@ckom0007]

It's Only Rocket Roll...But I Like It!

[@homefront3162]

ckom0007 ok..that was good

[@tedgey4286]

Solid!

[@sminstudios]

Like it. Yes I do!

[@billdarby4949]

Bahaha! - Now that's the best comment I've seen in awhile! - Sing it ckom0007!

[@robadams8057]

Respect. *Slow clap.*

[@AmyShiraTeitel]

Hey guys! Lots of you have noticed a little glitch in my editing around the 1:20 mark... Sorry! But I can't make the edit without taking the video down and reuploading the whole thing and, frankly, I'd rather just leave it up. I was at a convention this weekend and was a little pressed for time. I totally didn't see that in my last watch-through. Thanks for understanding I'm human, guys!

[@82ndaa31]

It happens. You still present a top-notch channel with incredible information. Keep up the great work!

[@Slaintemaith]

Except why the pads were oriented north/south and not east/west. Why put them that way in the first place?

[@Feintgames]

Maybe so that when the astronauts looked out the window, or shot a camera out the window, they didn't see a bunch of metal spars and instead saw the moon. Or maybe because the gantry had to be in a certain orientation in relation to the window in order to access the crew door, in this case 90 degrees.

[@DonalLour]

RALPH RENÉ: WORLD FAMED FIZZIZEST, ARTHUR AND INVENSTER told me in a vision (dream) that the Moon itself is a flat, hollow hoax sphere and that the secret Nevada Disney Moon set on Mars is where the Waffle-ϟϟ construct their fleet of invisible breakfast saucers. BTW there are multiple light sources used in your video and I see intermascecting? shadows. That proves your video is a hoax! I wins dis here argument. PAY ME NOW. Money plea$e :) RALPH RENÉ liked boys... :P

[@ApolloWasReal]

Look at the crew access arm. The hatch had to be 90 degrees away from the gantry for it to swing away. That meant the hatch had to be on either the east or west side of the rocket. Since the astronauts would ride into orbit heads-down so they could see the earth and its horizon, then the hatch should face in the direction they would travel. That was always to the east, toward the ocean.

[@calteran]

I can hear Tom Hanks in my head: "Roll complete; we are pitching!"

[@jshepard152]

"We got a wicked shimmy up here!"

[@0mathgaming]

@@jshepard152 That was after the oxygen tank exploded. The roll/pitch was during the launch.

[@jshepard152]

@@0mathgaming Of course. I like the quote and throw it out randomly.

[@0mathgaming]

@@jshepard152 oh ok then lol

[@melikesleepy]

Good content, it always amazes how this entire program was accomplished on so many 'primitive' computers and actual switches/mechanisms. It really shows what ingenuity, spirit, and dedication can accomplish...

[@nickbreen287]

Buy and play Kerbal Space Program and all this stuff becomes very very familiar!

[@Sander_Datema]

Not really, unless you are going to minmus.

[@nickbreen287]

Sander Datema ? Its the same science and physics?

[@Sander_Datema]

Nick Breen It is, though when I go to minmus I just make course corrections when half way there :P

[@Zamolxes77]

Pretty much. In fact with several mods, that implement N - body mechanics, it gets even more complicated than the model Nasa used to send Apollo missions to the Moon.

[@Zamolxes77]

For Minmus is relatively easy, especially since in KSP we deal with small escape velocities. But if you were to play in RSS, with similar escape velocities to Earth, then the delta-V you would have to burn half way there to match the orbit inclination, its significant, possibly even mission critical.

[@CaptJackWolfe]

My dad was one of the engineers on the instrument unit, so it's always been a favourite area of study for me. Amazing what they accomplished.

[@GermanShepherd1983]

I like Amy's hair style here. Best look I've seen of her, especially the bangs.

[@tanzanos]

Thank you Vintage Space. I enjoy all your videos. Live long and prosper!

[@wanderinghistorian]

I always wanted to know what "guidance is internal" meant. Thanks!

[@phishfearme2]

I love rocket roll, put another dime in the juke box baby

[@60viking]

Ha, right on.

[@thomasooms9541]

Buh - Dump -Tsh!

[@tommytwotone8510]

I know this is a few years old but I wanted to say it was great and thank you. I was a kid when this was going on and visited the space center but never got to see a launch. My mom's aunt was friends with John Glenn and although I didn't get to meet him he sent me a signed letter and several autographed books and a 4x6 photo that I still have.

[@OverlandOne]

This woman is a genius! I grew up with the space program and I love this channel.

[@kdmigloo]

She can read a script.

[@tracymiller1149]

@@kdmigloo And write the script, after heavily researching the topic.

[@patrickwall144]

Very nicely done. It was informative. Had enough information to develop a complete understanding without so much that it loses your attention. Given the little that I know about rocket science. I still walk away with a decent understanding if something I find quite fascinating. BTW the hairspray bottle stand-in. Well done, very well done.

[@Smokescale]

The roll would also serve to keep the crew pointed in the right direction, pushing them back into their seats rather than off to the side when they pitched. Rolling before pitching rather than using a combination of pitch and yaw would make sure the crew would be kept in alignment with the direction the vehicle is pitching. That's one reason why the Shuttle flew upside down on ascent rather than right side up. Better to push down into your seat than to be lifted up out of it. Great video by the way, and great job explaining the three axes! I had completely forgotten about the change in inclination of lunar orbit versus Earth's tilt!

[@arttafil6792]

Smokescale Aquatos It's the same reason that fighter aircraft do high g maneuvers with the pilot's feet taking the high g loads instead of their heads. If you don't invert in a high g situation you experience "red out". Your blog is pushed to your head and you don't have g-suit garters around your head. Ask any current or past fighter pilots the same question and we'll all give you a similar answer.

[@SimonAmazingClarke]

Considering that you are neither a Rocket Scientist or an engineer your explanation is awesome. I have been an aerospace engineer for over thirty years and I didn't know that. Well done.

[@Buzzbox3rd]

This girl does a great job explaining everything about Apollo. Well done.

[@whosapickle]

Holy hell you're really good at laying things out and explaining them.

[@schoolhse]

Best book ever! Highly recommend it!

[@DaylightDigital]

For not being a rocket scientist or engineer, you explained this remarkably lucidly. Nice job!

[@CreaseysWorkshop]

I love finding out these details. Also I love that you differentiate between science and engineering.

[@robertkreutzer4107]

Wow. You explained that fantastically. I'd never given the roll program much thought and assumed that it was for aerodynamic purposes...which now seems silly to me. Love all your videos! Keep up the fantastic work!

[@fmonahan]

For a 6-Degree Of Freedom system, rolling to change pitch angle (quaternion rotation) costs less propellant and is less stressful on the system and avoids gimbal lock. It's all about the fact that the moment of inertia around the roll axis is much smaller than around a pure pitch axis. Since then engineers knew they needed to roll the vehicle anyway to get to the desired pitch profile, they could build the launch pads at cardinal directions.

[@anhedonianepiphany5588]

True, but this has been pointed out in multiple posts dated prior to yours!

[@BarDownBoys]

sounds like BS

[@michealtaylor1297]

Why is that Hey.

[@loslosbaby]

I just appreciate the effort; complaining about problems is not part of being appreciative :)

[@4exgold]

damn, how is she not a rocket scientist? She seems totally at ease with the technical explanations.

[@seanflahockey]

Makes you realize how smart these NASA engineers were. And with very few computers at the time.

[@mramius3834]

This is actually exactly why there's a roll program. A rocket flies in 3D space, which means you have to worry about calculating 3 axis of movement. However, with the roll program, you remove one axis of movement and simplify it into a 2 axis/2D movement during launch. Much easier to calculate.

[@pkuras]

Thanks, Amy, I really appreciate your clear explanation of this - and I learned a lot from the video. I think a simple way of boiling this down (and correct me if I’m wrong) is to say that the roll maneuver is necessary to put the rocket’s pitch control apparatus (engine gimbals) into the right orientation so that the pitchover maneuver points the rocket in the right direction to get the spacecraft into the correct orbital inclination - because the rocket’s attitude can’t be controlled around arbitrary axes, but only around the three cardinal axes of control, so you have to control the rocket’s attitude around one axis at a time. Does that sound right to you?

[@Jeff034]

Really well explained. Thanks!

[@bendeleted9155]

Amy, You do a great job of presenting just the right amount of information for the geek like me to get the concepts and enjoy learning them. Thank you for making time to obtain the relevant details and pass them along to us. I hope you know you are providing a truly valuable service. Thank you!

[@tessierashpoolmg7776]

What a brilliant and inspiring young person!

[@mic7able]

I'm starting a 'Flat moon theory' just to be different. Anyone interested?

[@KC9UDX]

Mick G. What will we have to recycle to save the moon?

[@mic7able]

Cheese.

[@kmcleod78]

Mick G. and 11 months later some people actually believe that the moon is inside our atmosphere. Bet you didn't see that coming.

[@OrangeBroom]

LaCervetaMasFina They actually believe both Sun and the Moon are about 3000 miles up and inside the "firmament", yet proceed to say rockets hit the dome before reaching space (some 20 miles up) because "nothing can leave Earth". Pretty contradictory, eh?

[@redcorvetbule7136]

How about a cold sun theory

[@LetreJete]

Nice explanation. I used to build things like that for my kids using duck tape and paper towel tubes. LoL. My son's now smashing through rocket science at one of the top engineering schools in America. I'll bet about half your subscribers are his friends. See? You don't have to build to scale to illustrate your point. Thanks for your videos. They're really great.

[@MrBungledB]

Outstanding explanation. Thank you.

[@vegasspaceprogram6623]

Love the hairspray rocket😅🚀

[@shevek2384]

My own question is more of a comment. As I understand it it is not strictly necessary to launch from a parking orbit to the Moon that is in exactly the same plane as the Moon's orbit. This is most efficient and simple, but in principle one could launch from any low Earth orbit no matter what inclination and reach the Moon. There would be drawbacks, mainly a matter of a higher encounter speed with the Moon (meaning you need more delta-V, hence more rocket propellant mass, to put into a given Lunar orbit). Also the angle is off. If you did a transfer maneuver from an orbit that exactly matched the plane of the lunar orbit, when you approach the moon that approach is also in that same plane, whereas if you were to launch from let us say a polar orbit (relative to Earth) your approach to the Moon can be in any plane, depending on the details of one's aim. Also of course if one does not change the plane during the TLI burn, the polar orbit plane can only intersect the Lunar path at two points so your timing better be perfect, whereas the exact timing of a TLI burn from within the Moon's own orbital plane can be very relaxed. This is a major reason we bother with parking orbits at all after all! Another technical point that VS may have mentioned somewhere or might want to talk about someday is the "free return orbit" strategy NASA used (strictly only for Apollos 8, 10, 11 and 12 but their modified non-free return alternatives they used later were close to free return too). At first it might seem that any orbit around Earth is automatically "free return;" you do the TLI burn and then coast, and get a very elongated high eccentricity ellipse that eventually returns to the perigee where you did the burn. This would be fine if the Moon didn't mass much, like say Mars's moon Deimos. But the Moon masses about 1/81 what Earth does, meaning that it slightly perturbs orbits all over the Earth-Moon system, and when you come close to it it changes the orbits a lot. A minimum energy Hohmann orbit would not be free return, because the close encounter with the Moon would change its parameters and either the new perigee would be much too high and the crew stranded in space forever, or much too low and they'd burn up on entry. Instead of using these minimum energy orbits then, NASA boosted the Apollos to a moderately higher speed--moderately higher at TLI near Earth that is, but the more distant from Earth the higher energy orbit took a craft the faster it would be going compared to minimum. Were such an orbit aimed to miss the Moon, the spacecraft would loop out into deep space well past the Moon's orbit. As a result, when approaching the Moon when aimed correctly, if the astronauts did nothing the craft would find its course changed by the Moon in a sort of hairpin curve (if you looked at it in a frame where the Moon is moving that is) and get tossed back on another very similar elliptical orbit to the one they came out on, but now headed back to Earth. These kinds of free return orbits are not possible if you approach the Moon out of its own orbital plane! This is why NASA was restricted to low latitude, "tropical" landing sites; to head for the poles would result in no free return being possible and also higher maneuvering costs. Therefore it made good sense for NASA to start from a parking orbit closely matching the Lunar orbital plane. The Soviets on the other hand simply did not have the option of doing that. All USSR launch sites were in the Soviet Union which does not reach nearly as far south as the USA does. On paper I could suggest some alternative launch sites the Soviets might have thought to develop, such as North Vietnam or Cuba, but the geopolitical reasons they never considered that seriously are painfully obvious! Nor are these great launch sites despite low latitude; too much clutter of other inhabited lands to the east (which in both cases tended to be Western allied and the US Navy would find it all too easy to intrude or interfere, and would have the excellent pretext of concern for safety of non-Soviet allies downrange to do so. So practically speaking, Russians launch from Russia, or nowadays independent Kazakhstan. And if they don't want to risk launching over China, which generally bad relations since the late 50s and early 60s pretty much prevent them from daring to do, they have to launch to 57 degrees or higher inclinations. They just can't aim directly for the ideal Lunar orbital plane orbit, or come anywhere near it. And the cost of changing the inclination of an orbit is very high, at least in low orbits. Yet the Russians launched a number of probes to the Moon, including the first to see the far side and send back images, and had some serious plans to attempt manned Moon missions, flybys and a possible landing as well. How could they do it? This illustrates that although there are excellent reasons to launch from the same plane as the Moon orbits in, it remains possible, at a price to be sure, to get there other ways. All the details of any Soviet lunar mission plans I've ever seen seem to assume they'd use minimum energy Hohmann transfers, and when you realize that the Soviets would be forced to rely on their manned ships (or any sample returners) maneuvering at their close Lunar encounters to adjust their courses to return to Earth anyway, it is clearer how they could use quite differently inclined orbits instead. It still meant they'd suffer higher encounter velocities, but that would just be an unfortunate drawback of their being forced to use high latitude launch sites fundamentally. Given they were stuck with it, every mission plan I've seen attributed to them involves more maneuverable vehicles with higher delta-V reserves making the trip, and in some cases with a high level of redundancy Apollo planners could only envy! At a stiff price of course, and one the Russians who had no highly developed hydrogen engines, and were forced to use less efficient ker-lox ones (or worse, hypergolic--though both were developed, at some possible additional risk of failure, to pumped performance superior to equivalent role engines of similar type developed in the USA) these higher performance demands would be met by lower performance engines resulting in lower masses going to the Moon on higher launch mass vehicles. But I do think they could have done it, maybe not before Apollo 11 but with a different mission design and better luck and an earlier commitment, perhaps in the same year or in that case even beating the Americans. --------------------------- I've suggested other topics then, but in the context of this video, I would ask, just how different was the ideal Lunar orbital plane parking orbit from the easiest orbit for Apollo Saturns to launch to from Canaveral? I frankly thought the Moon orbited pretty close to the plane of the ecliptic anyway, within a small fraction of a degree I thought, whereas strictly speaking Canaveral is too far north to easily reach the tropical inclination. The saving factor is that because rockets burn over considerable time, it is possible to go a bit closer to the equator than one's launch site at moderate cost, though this cost mounts very steeply as I understand it. (Whereas it is very easy to launch to an orbit of higher inclination than one's launch latitude; an equatorial launch can go over the poles without too much extra cost). But some of the comments seemed to imply that Apollo Ii for one was aiming for an orbit of slightly higher inclination than Canaveral's latitude; surely the Moon is not tipped seven or more degrees relative to the plane of Solar System ecliptic? I looked it up--the Moon's orbit is inclined relative to the ecliptic by 5.14 degrees, which is a lot more than I figured! As a practical matter of Earthbound life, we humans are generally concerned with where the Sun appears to be in the sky and the Tropics are defined as the limits of the Sun's apparent migrations north and south above and below the celestial equator. I still don't see how the orbit in the Lunar orbital plane can have an inclination higher than Cape Canaveral's latitude but I think I might understand how come a launch almost due east from Canaveral can come pretty close to it, and require only minor "doglegging" to hit it dead on. I still wonder though whether Apollo missions all aimed to launch from exactly that plane, or compromised with other considerations for a different plane close to it that would require some small inclination changes to reach the Moon from with slight inefficiencies.

[@brianorca]

I think I heard somewhere that the Apollo missions did not actually match the moon's inclination, they used a higher inclination which allowed them to miss the bulk of the Van Allen Radiation Belts, but still achieve a lunar transfer orbit.

[@randyt60]

See, all you Hoaxards, this is what "Intelligence" sounds like. Thanks Shevek23.

[@johnp139]

Shevek23 Shut up Wesley!

[@Markomyt1]

Great job! Answered a long standing question for me.

[@mdmjeremiah]

How have I just now found this channel and this video? This answers a myriad of questions that I had since the first time I watched Apollo 13! Awesome!

[@carabela125]

The real reason for the roll program is that it looks cool. In fact, that is the reason for the whole space program.

[@andysedgley]

1:25 it's déjà vu all over again

[@neogator26]

You did a fine job explaining the roll. 👍🏼

[@justabigbaby]

Very informative, awesome and revealing. Another mystery solved for the few and far between.

[@mjl1966y]

So, short vesion: to align the pitch axis with the launch azimuth. I always wondered about the roll before pitch. Great explanation.

[@larrytroxler7017]

ha nice complete explanation in a short sentence! I guess a lot of the video was background info, explaining spacecraft axes and non equatorial orbits.

[@mjl1966y]

Larry Troxler The fact that I was able to state it so clearly is a testament to her ability to explain these things. I really wish she'd do one on the eight ball.

[@ironcito1101]

That doesn't answer the question of why wasn't the rocket properly aligned on the pad in the first place. I'm assuming that it's because it's much easier to rotate the rocket a few degrees in flight than to modify the pad and rotate the rocket on the ground for the correct orientation, especially because the required angle changed with each launch and when there were postponements and so on.

[@jongroubert4203]

Yup, that's basically it, Diego. I asked this same question a few weeks ago in a FB Apollo group, and they told me that was the reason. That gigantic crawler reaches the launch pad only one way. The tower only connects to the rocket one way. They were launching a lot of different rockets a lot of different ways, so yes, it's easier to rotate the rocket than to somehow get that gigantic, heavy crawler to rotate.

[@elvis3571]

short and clear is always good but one point: by definition pitch axis was brought to normal (perpendicular not parallel) to the desired bearing (launch azimuth as you call it or I would say ''the orbital plane'')

[@WurstWasser617]

Just plan a maneuverer node. Jesus... noobs

[@catherinemyers7763]

Black Thunder i

[@LABoh122]

is that the name of your adult paraphernalia or your rocket in kerbal space?

[@eltmg7135]

On ascent? Ain't nobody got time for that, I've got a rocket to steer here

[@ZFuli]

Instal MechJeb.

[@LABoh122]

ZFuli noooooo

[@tombombadil1535]

fantastic video! thank you!

[@w5cdt]

Great treatment of the subject!

[@mikaellauring5025]

So nice to know. I've often wondered about the roll. I've just come across your channel. Thumbs up. Give my regards to Pete :)

[@AmyShiraTeitel]

Cheers! So glad you're enjoying Vintage Space, and Pete just slow blinked at me when I passed on your regards... I think he likes you!

[@mikaellauring5025]

Loving it. Slow blinked... He definetly likes me😊.

[@gonebabygone4116]

Slow blinks are a sign of acceptance and calm. We're glad Pete approves :-)

[@Kikilang60]

I have to say, love the dacore. Very sixty'ish.

[@LordCarpenter]

Fascinating! Thanks for the explanation. :)

[@MikeAnn193]

0:34 - "So I made a little stand-in Saturn V out of a can of hairspray." Hahaha, that's _adorable!._ Reminds me of a couple of the model rockets I built in my teens and twenties, especially one whose body was a toilet paper roll. (That particular creation proved to be just slightly more aerodynamic than yours appears to be.) The cutest thing is that you went to the trouble of adding a little bit of Saturn-V-esque coloring to it. 😄 Good job.🖒 Good explanation, too. I'll check out your channel.

[@BCaldwell]

You had me at "zed"

[@EtzEchad]

I'm not sure if your explanation for the roll program is correct. I know that the reason for the Shuttle roll program is to turn the vehicle so that the pilot can see the horizon and to expose the antenna. (The shuttle normally flys upside down on ascent.) I read that Apollo did it for the same reason.

[@AmyShiraTeitel]

Nope. It was about flight azimuth. I had the guy who wrote the book on it go through this with me before I recorded this video!

[@retrofan42]

The Shuttle had to roll for the same reason, to get the orbit inclination correct, especially if they were going to a space station (like Mir or the ISS) or to the Hubbell. Changing orbital inclination can take a lot of energy. I believe the Soyuz does it too when they launch to ensure there is no energy wasted getting to the ISS.

[@EtzEchad]

+retrofan42 Rolling does nothing to change the orbit. The only reason to do it would be an engineering reason, such as making the inertial reference system work better. Apollo didn't have a very capable computer, so aligning on a single axis could make it simpler. Modern rockets don't seem to use a roll program. At least I haven't heard a call-out for it in SpaceX or ULA launches.

[@Pottery4Life]

Read this paper to find out why the Shuttle roll program was used. www.aiaa.org/uploadedFiles/About-AIAA/History_and_Heritage/Final_Space_Shuttle_Launches/Why_the_Wings_Stay_On.pdf

[@queenofyeay]

Great video, I always learn so much, and for a fan of the space program for many years that's amazing... It didn't bother me but it SEEMS like there is a double of a clip you used at around 1:30 where you say "So because the Apollo missions were eventually going to the moon they had to enter orbit into the earth that was inclined relative to the earth's equator" and right after that you say something remarkably similar, but I can't get my head around if it is an editing mistake or not! I thought I'd point it out in case.

[@cparedes2302]

Many thanks! I really enjoy your channel AND LEARN!

[@hgr4255]

A true child of the space program in it's glory, my father worked at Rocketdyne in Los ANgeles, the rockets that powered us to the moon. It provided the riches of suburban living in the 60's for us and tens of thousands of others. When the program folded after we went to the moon, those tens of thousands were out of a job. It was a dark time then, many suicides, shattered dreams, foreclosed properties and we fled it all after the program closed and moved to Germany.

[@naughtyUphillboy]

So Sorry, but governments take bad decisions sometimes.........

[@seansullivan3718]

"It was my understanding that Math wouldn't be a part of this video explanation"

[@josephegleston8834]

I have a story for you, Amy! I was talking to one of my my friends the other day, and we were exchanging weird stories about our families. Her great uncle apparently knew all of the Mercury astronauts because it was his job to fly parabolas for them to train for 0-G. He thought that John Glenn was full of himself, so he purposely flew as steep as he could on one of Glenn's training sessions trying (and succeeding) to make John Glenn throw up repeatedly.

[@jeffcorsiglia5379]

Sounds like her great uncle was a dick.

[@chadcastagana9181]

Don't tell us, her great uncle was a homosexual

[@cat637d]

Glenn turned out to be a leftist liberal democrat butt wipe!

[@jimlaymon6021]

Great explanation. I love David's book and you both explained it clearly. Thanks!

[@ripilot17]

That's absolutely best explanation as to how this worked!! Thanks so much!!

[@gwyn.]

How does a rocket decoupler work? (Because they looks like they're fit on with no bolts, and yet still holds the stages together.) 0-0

[@taylor1038]

Based on my limited knowledge and reading that book ;"How Apollo Flew to the Moon" I've gathered that the rocket stages are solidly afixed together and controlled explosions by detonation cords separate stages. Then small rockets on the spent stage fire to give distance for the next stage. Good video topic!.

[@juan120535]

I think they do have bolts and in between have something that expands and breaks them off, causing the separation.

[@TheErilaz]

explosive bolts (shaped charges)cuts it loose,then small rockets are fired to clear it.

[@markholm7050]

I have read of a few different systems for stage separation. Pyrotechnic devices feature in nearly all of them, but the details vary quite a bit. Explosive bolts exist, and are used, but the overall function of the systems can be much more subtle than simply imagining a bolted together structure whose bolts are explosively failed. I understand it is still a subject of active development.

[@AmyShiraTeitel]

I did a video/blog on that a while ago: kzbin.info/www/bejne/lXzUZ2qImMuGptk

[@photonman54]

you need to do that in kerbal space program too.

[@mizzyroro]

What is everyone's fuss with Kerbal? Orbiter is way better.

[@intentionallyleftblank3380]

Eagle Lander 3D is also very good for just the lunar landing.

[@mizzyroro]

+AvengingNarwhal With Orbiter you have to get the Apollo addon and the sound package.

[@photonman54]

KSP is great if you are the creative type because you can build your own rockets, planes, stations, bases... ect. and you get contracts so you have to think creatively to solve them or get to the right planet and be able to get home safely.

[@retrofan42]

Orbiter has a ton of add-ons for real and imaginary rockets and spacecraft. It does have somewhat of a learning curve. I still have not perfected docking with the ISS or Mir (yes it has Mir in the basic program).

[@raymondknoll]

Your presentations are excellent. They are concise, quick, knowledgeable, with enthusiasm, and a pleasant voice. Keep it up and leave any competition in the dust! 😊

[@robertgardner7470]

Excellent presentation by Amy. It is understood that the roll program axes differ from the axis of the rocket sitting on the launch pad. On the launch pad the z axis is vertical, the x axis is e/w and the y axis aligns n/s through the flame trench. Flight efficiency is maximized by using earth's gravity to tilt the rocket's flight in an eastward and nearly horizontal path.

[@martythemartian99]

I assume a "Pete Based Incident" is your version of the term "Sudden Unplanned Disassembly" (used when a rocket blows up).

[@Sander_Datema]

rapid*

[@martythemartian99]

whoops :-(

[@anodynemathematician4194]

Marty theMartian I thought it was Rapid Unsechduled Disassembly?

[@jamesbaxter5081]

ROFL...I love tec double speak referring to explosive decompression as " a change in cabin preasure

[@JoelHudson]

Except a "Pete Based" incidence is feline initiated

[@artwdog]

Love this stuff, Amy. Amazing stuff!

[@pcox8600]

Thank you so much. Awesome vid!

[@PV1230]

your paper rocket looks more like a V2 than a Saturn V ;)

[@davidlafleche1142]

What, you never heard of Rocket Roll Music???

[@noddynoble9391]

Did you write titles for rocky & bullwinkle episodes??

[@davidlafleche1142]

No, but I liked the bad puns.

[@noddynoble9391]

I better get another hat.

[@davidlafleche1142]

"We're in REAL trouble now, Bullwinkle!" "Well, good! I hate that make-believe kind!"

[@kurtreber9813]

David Lafleche lol. im guilty of having thought it, but ur guilty of having said it ;)

[@whoanelly737-8]

Great explanation!

[@richardkaberry8790]

Wow! Thank you. Really enjoyed that!

[@steverodgers8425]

"It's been a long time since I rocket rolled"

[@JCDealy]

Everyone can use a little Rock[et] and Roll! Sorry, incredibly bad pun...

[@daffidavit]

Actually, it wasn't an "incredibly bad" pun. It was just bad. But I'm an Abbott and Costello and a Three Stooges fan since I was a kid, so, I'm a tough critic. LOL

[@peterkierst2744]

Excellent. I have had that question myself, and appreciate the answer. Carry on!

[@georgiahall9064]

Very detailed and complicated but I do have a better understanding of the procedure now, thank you. I took ALOT of notes.

[@doggonemess1]

Why did a sentence repeat at 1:30? Or am I losing my mind? Wouldn't be the first time...

[@davidhoffman5789]

It did repeat. Could be an error in the uploaded file.

[@TheAssenholm]

Nah, just the code of the Matrix being altered.

[@davidhoffman5789]

N|O.C.A., Amy, Vintage Space, Pete, and the Matrix mixed together. Somehow I think that is a good recipe for troubled times.

[@theartist124]

Rough editing.

[@Psittac20]

that was one part that threw me off, I don't know exactly which plane everything lines up on, but I figured out the overall reason for the roll non-the less.

[@richhoule3462]

I've watched this a few times. I still don't get it.

[@xyz.ijk.]

Neither did I. Read the explanation by the commenter ApolloWasReal. He fills in the blanks.

[@sgn4899]

Yes the roll and the need for it was not clear. She seemed to mix up the x and y axis too since y is vertical only.

[@thehoodedhorntail6749]

@@xyz.ijk. essentially, it is easier go control the rocket in just 2 axis instead of 3 so it rolls at the beginning of the flight to be on the same orbital plane as the moon and then has 1less axis to deal with

[@xyz.ijk.]

@@thehoodedhorntail6749 Thank you for your very clear reply, though I think you should post it as a main comment and not a reply that will be hidden in a thread. It will reach a wider audience -- and I'm not sure why you replied to me as I am clear on the details and the math: I was replying to the main commenter about the unclarity of the video and offering another commenter who provided clarification.

[@ChristopherLamke]

Great explanation. Thanks!

[@richardsisk1770]

Great explanation. Thank you!

[@aliensoup2420]

You forgot to explain to the Flat Earthers how we got through the firmament dome.

[@bugsy9069]

There's a button under the president's desk that opens the door, ya gotta know somebody important.

[@StefanMArndt]

The moon is still inside that dome, duh!

[@gaiawillis]

@Claudia Juarez we refers to us as a species

[@lynnbrown4687]

Your globe head is swelling.

[@TheCorrectionist1984]

Isn't it amazing all the details NASA went through to trick us. Even a "guidance internal" call and roll program. They must've known some brilliant flatard would figure out it was all fake without that. Lol

[@Mossyz.]

How did they get through the dome ??

[@theravedaddy]

They clicked on the garage keyfob thingy and the catflap opened

[@nescio03]

What dome?

[@prof.hectorholbrook4692]

Very informative. Many thanks.

[@pm9601]

Loved your demonstration of the x-axis, particularly the down stroke at 2:22 .

[@ishyab011]

Beauty, Brains, and a great personality !!! Yup, I'm in love. :) :) :)

[@astrosasha]

Cringe

[@pomegranitejason]

Come to my quarters, I would like to show you the "Captains Log"

[@fjon4060]

Wow! Thank you, for the explanation.

[@12longbow]

I wish you were still doing the Vintage Space videos, i thought you always explained things really good.

[@GumballAstronaut7206]

Thumbs up who already knows this stuff but just wants to hear it again! 😋

[@bkearns34]

yes!

[@TitoRigatoni]

Play enough KSP, it becomes second nature ;-)

[@fistpunder]

I am nowhere near being a scientist or engineer, so having someone explain it or "dumb it down" for me is appreciated. I wish I understood more. I guess that is exactly why I like watching science shows, I keep hoping to understand more.

[@spacewatcher215]

Yes.. You've gotta trust us.. All of you who came here wishing to be like us. KSP is the way. ;-D

[@Observ45er]

+Clessandra Pippenschnott Unfortunately, that same brain that can imagine truely great things is also capable of imagining more than the worst....We are in what I call "The Sound Bite Age" where full knowledge about a subject is believed to be obtained in 15 seconds or less, thus allowing one to 'teach' others the 'truth'. [Dunning-Kruger part 1....There realy is intelligent life on Earth, it just doesn't jump in your face on major media. You have to look for it.-- Cheers

[@crashk1955]

So the world isn't a flat disk. Some will be disappointed

[@kaiserschnitzel89]

TRUMP 2020

[@HelloKittyFanMan.]

Yeah, some... IDIOTS!

[@HelloKittyFanMan.]

Kaiser, what should that have to do with anything CrashK said?

[@theteddychannel8529]

No, the tweet was "The Flat Earth Society has members all around the globe", I doesn't make sense the way you said it. Also, the FES is a joke.

[@vikj1255]

Good work. Nice and simple

[@guyjones1876]

Superb job of answering a complex question! You really are a good teacher ~

[@Dirtbug473]

Wow...I only followed about half of your explaining...I am 60...what a wonderful time it was when I was about 13 we were watching the first moon landing and more later...My generation grew up believing we could do great things. Sad...now we hitch rides with the russians...?

[@WG-tt6hk]

Shane , SpaceX is restoring the greatness back.

[@vapenation7061]

Shane vanWinkle our millennial generation lives their lives through phones and can only believe conspiracies shitting on your generation’s success.

[@egidijuskuprusevicius4225]

you was watching a hoax...even a daughter of the first cosmonaut Gagarin said that her father didn't fly to the orbit at all...it was a fake and only after some 5 years the first man was sent to orbit Earth...around the time nasa sent astronauts to orbit it too

[@vapenation7061]

Egidijus Kuprusevicius yeah, because the words of small children are a valid source of truth.

[@egidijuskuprusevicius4225]

she is now 50+ years old...you can find it on youtube in russian language

[@callanhutchison1871]

Hot + smart = even hotter

[@stegervill1]

Callan Hutchison that's how I feel about myself...

[@chadcastagana9181]

Without makeup, she is just a plain jane

[@Raz.C]

How did you know I'm hot?

[@yiwanye1221]

even hotter in person

[@peterhart9872]

Oh! I don't know about that, I'm not into the heavy make up scene, I wouldn't kick her out of bed just because she farted.

[@ben31tube]

Good explanation! Thanks!

[@chrishampton4749]

Very nicely done!!

[@crazedvole]

I wish there were more women who liked to talk about space & science

[@AdrianJayeOnline]

no you don't you mean you wish there where more women who gave oral and did 3 somes

[@nikkitytom]

AdrianJayeOnline You are embarrassing. There are lots of us who love to talk about science, but we’re smart enough to scope out idiots like you. And we avoid them like the plague.

[@albertbatfinder5240]

I have a suspicion that if you were a rocket scientist, you would not have explained it so well.

[@andrebartels1690]

That was understandable. Thank you for that very good explanation.

[@rcastrope]

nice explanation. Thanks!

[@tacobell6826]

In other words, the departure angle doesn't align with the target approach angle and the roll compensates. One sentence. Engineer.

[@anhedonianepiphany5588]

Perhaps a first year Engineering drop out - impressing nobody! Your description is imprecise and requires far more definition. _FAIL,_ sorry. (I wonder how bad it was pre-edit?!?)

[@tacobell6826]

@@anhedonianepiphany5588 Nope. Masters Electrical Engineering; currently a Project Manager for Bosch. In what sense is the description "imprecise"? I merely condensed her long-winded blather (I forgot to add, British engineer).

[@Jimothyp]

WOW. PRETENTIOUS AND ENGLISH? GOOD SPORT!

[@065Tim]

This is why there never was a British moonlanding. They consider precise instructions to be long-winded blather.

[@billparrish6113]

@@065Tim Sure. These guys were flying supersonic jets across the Atlantic while we were still using 747's. Yeah, they're hopeless at engineering. 😂