Planning The Apollo Missions, Part 1

good morning I'm Erin Cohen director of the Johnson Space Center and it's my uh pleasure uh to welcome you here this morning for our second uh Symposium of the week we're going to have one as you know each each morning um you might not know or you may know serious studies as how to go to the Moon began even before we did um the first man flight when President Kennedy committed this nation to the lunar Landing we had only 15 minutes a manf flight experience on June 25th through June 27th 1966 this Auditorium was packed with scientists and the technical community interested in the lunar mission in the previous year the program was baselined and a Conference was held to put the total program in perspective so that all the participants could see how all the decisions previously had been made and what the total scenario of the lunar mission was over the following two years there were a number of reviews by the so-called uh president's scientific advisory committee and the NASA advisory committee and many others but they all came back to the this scenario that we had laid out in the final event as the mission was planned is as we uh flew it in developing the Apollo hardware and software we also developed the management practices which still today are how we're implementing our our programs at the Johnson Space Center it left us a very fantastic Legacy and the people you see up here today are the people that uh left us that Legacy Dr Gil Ruth who was the sener director at that time made a particular point when he introduced his Symposium in 1966 it had come about because of his insistence that it' be done he believed that the program needed to get a perspective on itself and this was a way to achieve it so he began by saying and I quote most symposia are held for the benefit of the audience this one is different is being held for the benefit of the presenters and today this abbreviation version you're going to hear the experts that uh that had that carried on that full version is for the benefit of the audience but I can guarantee you even though they haven't told me that they've got a great benefit in preparing for it I would like to uh Joe Loftus is going to be the moderator and Jack SE and they're going to do a full introduction of the panel but I can't uh I've got to mention a few people here and welcome them back because it means an awful lot to have these people back with with us Owen Maynard uh who will be introduced more formly but Owen's here Pete Frank and Chuck Barry and uh Doug broom will be joining us uh soon so I think you're in for a very very interesting uh morning and now I would like to turn it over to uh Joe Loftus who will do the fal introductions to be the moderator thank you very [Applause] much good morning and welcome as Aaron mentioned uh this is an abbreviated version of a symposium that was held in May of 66 or June of 66 and the reason for doing that was is that we had taken the several major systems engineering decisions that were required to decide upon the fundamental structure of the program before we had flown in space when the Army the Navy the Air Force and the NACA were beginning to look at how might one explore space with the technology that came out of World War II there were essentially three proposals as to how one might go to the moon and it's interesting that we were looking at going to the Moon before we were looking at doing a space station or activities in low earth orbit and I think the reason is fairly straightforward uh the Moon is visible it is a place to go to only after we had flown Apollo and began to fly Skylab did we begin to realize what a significant difference there was in the lunar Mission the trajectory to and from the Moon becomes in effect the Clos line on which you hang all other activities when you have a space station in low earth orbit and it essentially has a repeating trajectory then the planning of activities and the scheduling of resources in fact becomes much more complex than it does for a trajectory dominated Mission there were three ways to go to the Moon one was to launch directly from the earth and land directly on the moon and that is essentially the scenario we used for the ranger program in which we launched photographic spacecraft which approached directly to the moon and eventually crashed on its surface that scenario has many advantages in terms of the minimum amount of energy required it has the unfortunate property that if anything goes wrong it is always catastrophic the second proposal was to launch into low earth orbit and rondevo those Elements which were required to conduct the lunar Mission but even with that scheme it was envisioned that one would launch from lowor orbit having assembled the lunar Entourage with one or more Rendevous and then go to a direct landing on the moon that had the virtue that you did not have to have such a large launch vehicle to launch the mass into low earth orbit it had the advantage that that if you failed in the Rendevous you were in low earth orbit and you could Retreat to Earth but it still had the disadvantage of the direct approach to the Moon with its catastrophic failure modes there was at langlay a man by the name of John hubot who was very imaginative and he in effect took the general principle of staging in rockets and pursued it to to its logical consequence with a scheme that became known as lunar orbit rendevu which was that you would launch directly from the earth you would launch then into a free return trajectory so that if you fail to enter orbit around the Moon you automatically return to the Earth and you would then land on the moon with a separate module from a lunar orbit and then you would have an Ascent stage which would come off the lunar surface and Rendevous with the Command Module that was a very seriously debated subject as you might anticipate the Marshall people and a lot of people who were in favor of bigger launch Vehicles favored Earth orbit rendevu or direct launch in the end we favored lunar orbit rendevu and I think the deciding voice was that of verer Von braa who said it is the right thing to do because it puts the management of the interfaces between the vehicles which must rondu under the control of a single Center a single engineering organization and that will assure that we have the simplest most efficient interfaces if I could could have the slides please that decision having been taken there were a set of general principles that we were to follow in embodying it and I have tried to summarize these on these two slides the plan of having an open-ended mission was one which came out of the general tradition of flight test which said always be able to back out of any planned commitment so that you don't get yourself in trouble the Moon is retrolective the soil has been eroded by the solar wind over billions of years and so it has a very fine dust kind of property what that means is is that if you're looking directly down Sun you see nothing it's like driving into the fog with your High lamps on in a car that meant that you had to be above the sunline in order to be able to see rocks and craters that then dictated your landing approach and made it very steep about 20° which is about six times as steep as a conventional aircraft because of that your potential Landing site moved Westward across the moon as the Sun moved 15 degrees a day so you had to train for multiple launch sites Landing sites because the site you would land at on the first day would not be available if you had to recycle because you would be under the sunline and not able to see obstructions the network of course is the m space Flight Network and particularly at lunar distance we use the three major systems at at Madrid Goldstone and canaran in Australia I'll not go into the others you can read them but it was because this family of decisions had been taken but taken in a multiplicity of separate actions that Mr Miller the Dr Miller the associate administrator for space flight man space flight and Dr Gil Ruth had wanted to hold a symposium in which the entire story was told from beginning to end so that we could be sure that we were doing all of the things that would be necessary to succeed Mr mayard was at that time the manager of the mission Operations Division in the Apollo spacecraft program office he is now with Ron company in Sudbury Massachusetts he was charged with organizing this symposium and he gave the mission summary and overview paper it took him about three hours then so we're going to have something like a 16 to1 compression ratio [Applause] Owen thank you Joe and good morning yes it is good morning here it's slightly after lunch back in Massachusetts this that I'm going to give is a brief summary of key points made following the introductions Etc during the Apollo Luna Landing Symposium in its first day 25th of June uh 66 it lasted three days and uh as Joe said it took us a year to uh put the thing together by way of introduction this first paper that uh many people helped me prepare but that I gave uh was in four parts the first part talked about plateaus and uh gave a gross Mission description second part talked about planning for launch attempts considering the Looney lighting constraint that Joe spoke of and site selection that had lar largely to do with the completing the mission successfully getting there and being able to uh land at sites that weren't too terribly rough and so forth and science took a secondary position uh in our total scheme of things the third uh part was a detail Mission description where we went through all of the steps in getting from the Earth's surface at the cape into Earth orbit and uh each one of the steps and each one of the of the plateaus along the way we're going into in considerable detail and uh lastly we summarized the velocity budget we referred to it as the Delta velocity budget for each of the uh modules of the uh man spacecraft uh each of the modules that had propulsion systems and uh then we concluded with a question and answer session where uh uh Dr Miller and uh uh Dr Shay had had had charged the audience with uh hey you are a part of this this program and we expect you to ask your question particularly those that are very profound and meaningful here today and we'll have the speakers get the right people to work on the problem to answer your question and we don't want you to walk away from here thinking that you had just been interv entertained you are indeed part of the working Community that's going to do this thing there were three really major questions that that got asked and are recorded in the document that we put together after the Symposium General Phillips uh asked a question about the Saturn 5 recycle time where we had said that uh at one time folks we were thinking about 24-hour recycle so we could kind of have a launch opportunity every day and we discovered that you couldn't do that uh that it really took 48 hours to even recycle a person's way of thinking to get them to be able to uh uh go through the the routine of a of a of a scrub and then count the vehicle down and count it back up again get your act together and be at a reasonably high peak to be able to to do the uh the second attempt and third attempt and so forth so we concluded that that you couldn't do things in less than 48 hours and general Phillips had the basic question can we even do it then with respect to the Saturn 5 the launch complex and so forth and and uh we did go back and ask very pointed questions uh to both the people at Marshal space flight center and and and at the cape and uh resolved that and we did indeed continue to plan the 48 Hours Dr hosman uh asked questions about the direct asent versus uh direct accent uh and doing the translunar insertion immediately after you've done all the other earlier uh parts of the burn rather than going into Earth orbit and using the whole Plateau concept that we're going to talk about today so we Revisited that and and uh gave the uh the the definitive answers as to why we were con now committed to uh the plateauing concept Mr or Nicks uh asked about the s4b stage where we going to let it land on the moon uh there were lots of controversies where people said hey we ought not to go around polluting the moon and and uh other people had the notion that hey you a lot to let land on the moon so the scientific experiment on the moon could use it as a known Mass known velocity impact and come to understand some of the uh uh physics of the Moon uh with having this known object impacting it at a known time and so forth and so it became there were groups of people that were interested in a letting it impact and other people be hey don't let that thing come close to it and uh we concluded that we ought not to worry that much about it for this first mission let it impact if you if if you want actually they're wearing any experiments that I know of at the time that could have taken advantage of it and subsequently we did indeed let an impact now today we will compress the uh uh the the several hours into 15 minutes as Joe said uh we'll present just the key points made regarding the concept of the missions being partitioned into a series of plateaus the notion of the plateaus goes something like this that uh when uh one thinks about climbing a large mountain uh in an energetic series of climbs uh I haven't done too many of these but my children have and they tell me about these things we pause if we're smart at at the stable convenient places or plateaus in climbing the mountain Mountain uh and we do this on the way up as frequently as as uh seems prudent and we pause again at the summit when we get there and reflect in what we've done and so forth and a again on the way back down or if you go down the other side of the moon you may even be on a different route entirely it sometimes can be as difficult and risky or even more so coming down uh than it was going up so again the plateauing concept applies coming down and sometimes it takes strangely enough energy to bring you back down again and it's a different set of muscles in our case a different set of engines the visual aids being used today are the first three I'm only going to use three visual aids of 60 some that I used in 1966 um so they're taken from the plateau portion of the Symposium and they are completely documented along with all the words that got said and that documentation is available for you I'm sure somewhere around here the key points are also taken from that portion with some embellishments uh from the other parts of the of the first paper my intent then well my intent at that time as it is now today is to help Orient us all and was no one needed more orientation than I and people like Joel and the other people here uh we work together teaching each other how to do this thing for the first time and we began to get oriented I'm not saying we were complete instant Geniuses at the time and we certainly weren't and so we were in a very low in the learning curve at the time we made this Symposium uh but it stuck fairly largely and uh we're all terribly thrilled with that okay so this is to help Orient us all so we can begin to comprehend the mission in understandable steps it is a little mindboggling if you just sort of sit back and think about it but if you go through it in steps it kind of does help now the precise words that got said at the Symposium I'm going to use I'm going to going to read now from the from uh the we taped it and then we then we typed it out and we used we we we spoke in this funny kind of language 20 years ago it said it is useful to think of the lunar Landing Mission as being planned in a series of steps or decision points separated by Mission plateaus may I have the first figure please the there are nine plateaus listed here and uh in my going back through it uh in the last few weeks I uh thought you know I really ought to have listed a tenth one that was sitting on the on the earth's surface in the ocean waiting for the recovery ship to come and uh pick the crew and the and the spacecraft The Command Module up and so there is really a tenth one there in my mind today uh we certainly were aware of that at the time and uh but I guess that people put a lot of pressure on me to be brief once in a while so they made me cut it down from 10 to 9 even then uh we haven't returned safely from and return the crew safely to the Earth as President Kennedy asked us to do until we have done that recovery so I thought today we ought to emphasize that a little bit the decision to continue to the next Plateau as you go down the list 1 through nine there uh is made only after assessment of the spacecraft actually in the early the first plateau the going up from the first to the second Plateau it's the launch vehicle uh is involved here as well but after that it's entirely the spacecraft set of problems so we had to come to understand whether we had the ability to function properly on the next and subsequent plateaus and that's why we went to the plateau concept it wasn't to Simply get there and rest and take it easy it was to deliberate in great depth to understand were we ready to proceed to the next one if after such an assessment it is determined that the spacecraft will not be able to function properly then the decision may be made to proceed with an alternate Mission alternate missions therefore will be planned essentially from each Plateau similarly on certain of the plateaus including lunar stay the decision may be made to delay proceeding uh to the next mission Plateau for a period of time in this respect the mission is open-ended and that's one of the buzzwords of the day we had to be open-ended the flexibility that results would will be discussed in some detail throughout the rest of the Symposium here today I'm sure as it was back in ' 66 we went on to say that it will be convenient for purposes of overall mission description quickly to go through the mission plateaus and decision points following this gross description the operations for each Plateau were examined H in Greater detail however today we will forgo the detail the end points of these plateaus uh 1 through n is shown there represent major commit points in the uh uh lunar Landing Mission and uh they're characterized by propulsive Maneuvers the way way you got from one Plateau to the next was by using some propulsion system usually except in the case of the of the uh transar Coast to the surface of the ocean uh that was done largely by the energy being taken out by the heat shield on the Command Module which wasn't really a propulsive system it was an ablative cool system it lost a little weight coming down and in the normal way of thinking about specific impulse uh it was a terribly high specific impulse piece of the of the mission now this in in take taking out the this spacecraft energy or putting it in uh it's usually kinetic energy that we speak of here and if you remember a little piece of your physics uh kinetic energy is a half mv^ squ and you can kind of add your V squs up uh and your MV squs up uh whether velocity is plus or minus when you square it it's plus so it it costs you whether you're taking it in or you're putting it out now these commit points and Mission plateaus can both be represented schematically on a single chart is shown in the next figure maybe have figure two please figure two illustrates the major Maneuvers uh and the the tall do we have a this is it boy we got new scientific ways of doing things here oh there it is okay there we are okay now there it says 5.6 * 10 6 pounds that's how much propellant it took in the F to go from pre-launch to to Earth parking orbit and it's off the map it's a way up here because that's uh over here on the other the side this is a much much less than that so that we just couldn't even get it on the scale so this is is the big energy consumer and the little the little shaded things are the velocity increments that it took and they're the numbers for them are over here and the and the dark ones are the are the masses of propellants that it took and the quantities on the scale are over there and each of these this one here is what it took to go from there to there this one here is what it took to go from there to there and so forth okay okay now getting away from the exact words that were used in the uh in in the uh Symposium in ' 66 uh we'll go back and think a little bit here we we we now have a little familiarity with the idea of plateauing and the associated energy step to climb the first and most energetic Hill to Earth orbit we also have a little familiarity with what we have to do rather than just resting and waiting on the second plateau uh Earth orbit before uh committing further let us now go brief briefly and somewhat freely through the rest of the mission using just figure two uh on the right slot side and if we may have figure three on the left slide and we'll try to scope out and begin to understand the remaining plateaus now we may have to sit a long uh time on Plateau one the pre-launch on the p or at earlier points in in the pre-launch rather than just on the pad and it's kind of buried way down here in the bottom left hand corner now I will I'll walk you through without referring to my notes uh through the entire uh sequence of of plateaus and the transitions between them so you can't hardly see it we we launch off the Earth's surface into into Earth orbit and we sit there for up to uh 4 and a half uh orbits I believe it was now and then we decide that we are ready to go to the Moon we've got a good set of spacecraft equipment largely propulsion and guidance equipment and the consumables for the life support and so forth and we if we don't really think we have it we can abort and we can come back home but we have to take advantage of the tremendous risk we have taken to get there and we have to proceed as aggressively as we can so we do a translunar in injection on the opposite side of the Earth from the Moon and Pete Franks enlightened lightened me back in ' 66 as to why you had to do that and I'm sure he'll cover that later so we throw a big piece of velocity using the last stage last part of the upper stage of the Saturn launch vehicle s4b stage to put us almost on Escape trajectory and it comes out and it goes around the front of the Moon and coming in behind the back of the Moon we are going at almost escape velocity from the moon so that if we didn't do something we we would come whipping back here on what is referred to as the free return trajectory and we would nominally come back and enter the atmosphere and land safely now we probably need some midcourse corrections and so forth to make all that happen to go from that free return trajectory then the next so that this is the this is the plateau of that's it's called Uh uh trans lunar Coast over here it's written there there it is PL lunar Coast so then we get here and we have deliberated all the way out here we've even gotten the lunar module to be sure it's all set to do its Burns and so forth do its thing when we get to the moon and and uh so back here the service module uh retr fires actually has to slow down otherwise we will escape so he has to actually slow us down take the energy out and put us into orbit around the moon in the meantime when we launched the moon was way down here and this is 24 hours later 24 hours later so that when we were down here there's where the moon was and as we proceeded along this path the moon whipped up here and lo and behold we LED it like you would lead shooting birds with a shotgun uh and we had to get there at the same time so here we are in in lunar orbit and we think about are we ready to land and we transfer again into the lunar module and we and we decide yeah we're going to land and we go through the landing routine which is takes a long time to discuss so I'm not going to go into that in a lot of detail here but it uses The Descent stage of the lunar module to do it it was a very complicated stage because it had to be throttleable gimble and uh multiple start capability and a good many of the that's more than was asked of of any other stage in this uh total operation and and so we do our do the things that we have to do in the lunar surface we get out we put our foot in the moon and we say uh uh we have we have landed and that's what President Kennedy want us to do was go to the moon now we have to get off again having done our thing on the moon uh get back up into lunar orbit with the ascent stage come back on this Plateau transar Co Coast which is really the same sort of thing as as as this dotted part of the free return trajectory come back enter the enter the atmosphere at almost escape velocity man will probably never have to come back and enter the Earth's atmosphere at much higher velocity than that again ever and uh uh the Command Module with his heat shield and so forth dissipates the energy we come down we land on the lunar surface and and uh that's we have now completed the mission wait for the for the recovery ship to pick us up and the part and return him safely to the Earth has been completed we have been successful hopefully in doing this the first time and uh but we are suspicious we won't and so we did a lot of hoping from then on now that concludes what I what I wanted to say and I hope to have a lot more time to to go a lot of the detail with you but I'm I'm I'm sure we can't so I'd like to conclude it now and if there's any questions I could take them now or maybe you want to wait till after uh we've got time for one question is there any uh General Phillips or Warner Von bronze in the area that would like to ask the kinds of questions we got last time or we have one question here well the question is there has been much written about Marshall's advocacy of Earth orbit Rendevous and jsc's advocacy of lunar orbit rendevu what were the thoughts of the people at the Kennedy Space Center I think well I I I'll have a have a go at it Joe in the actual Symposium if I couldn't handle the problem I invariably said well Joel lus will cover that in his part but I will uh I will attempt that here one of the reasons as a matter of fact the question that was asked by uh uh Marshall space flight center people where why don't you go directly after we made the entire Symposium why don't you go directly rather than going to Earth orbit that was really a question in a couple of the of the modes that we might have of undertaking um and the answer that we gave was we want to have as many plateaus as we can where we can for instance sit in lunar orbit or launch early and then sit in Earth orbit first and let time catch up with us or sit in lunar orbit later let time catch up with us and if we have problems of getting off the path uh either due to weather or the launch vehicle or the launch complexes problems give us as much opportunity as we can to recycle as as many times as we can both in an hourly sense and in a daily sense and uh give us a chance folks to uh uh baby our our uh our facilities and our launch Vehicles along and I think that the lunar orbit rendevu mode maximized that it gave you much better flexibility from both the mar the uh uh Kennedy Space Center Point of View and everybody else's point of view that's kind of why everybody in the end decided that that was a good thing to do I think thank you ow uh I think there's another facet of that and that is is that it was only about this time that the Kennedy Space flight center was established as an independent entity prior to that time the operations at the cape had been done by contingents assigned there from Marshall and JSC it was only at that time that it became an independent organization our next speaker is Pete Frank Pete at the time of the Symposium was in charge of the mission analysis branch in the mission planning and Analysis division he subsequently was one of our flight directors for some of the lunar missions and he is now with Ford Aerospace Corporation Pete will speak to us on Mission planning I I've got to say a couple of words about how good it is to see some of these uh I start say old faces faces of people that I haven't seen in 20 years or so Owen hasn't changed uh a bit he looks just the same and he still takes twice as long to give a presentation as he's allowed good go uh Mission planning for the lunar missions was really uh almost totally dominated by trajectory considerations as as Owen has pointed out uh the plateaus and the and the trajectory characteristics uh throughout the mission varied considerably from the earth launch to the Earth orbit insertion and so on through that whole series of plateaus that he talked about each one had its own peculiarities and its its own implications on how the mission planners were to were to put a uh an overall mission profile together so uh trajectory considerations really dominated uh our mission planning activity uh I'm not going to try to uh give a brief uh summary of the whole talk that uh that we went through that day uh I'm just going to pick out one little aspect of it and and probably give you a little insight into that and it has to do with the uh launch window determination it sort of fits in with with what we're talking about here uh and let me start off by uh starting with that picture of the uh lunar trajectory geometry can I have the first slide please as was uh pointed out the injection uh onto the uh trajectory out to the Moon occurred at a position about like this on on on this side of the earth and I learned a new word in getting ready for this and it was called the antipode and uh the antipode is that point here on the surface of the Earth that if you take a line from the Moon and draw it through the Earth and where it pierces this side of the earth that is the Moon's antipode well we found out that the way to get to the moon on a fairly uh inexpensive trajectory was to do the the the Homan type transfer or make a a burn at a Pary position uh the actual trajectory that we uh left Earth on was really a very highly eccentric ellipse and its semi- major axis uh was on a line that was close to this antipo of the Moon uh so that our our first uh plan or or problem on the lunar missions was to get to this antipode position so that we could make our injection and and head out toward the moon uh and as as is Illustrated here when we got in the vicinity of the lunar gravity where the the lunar uh the moon's gravity started becoming the dominant force it actually pulled the spacecraft off of this elliptic trajectory and sent it in what was a hyperbolic trajectory around the moon and so that if we did not make a a maneuver here we would have escaped and and gone right on past the Moon I was uh was really delighted to find out uh when I did find out that there was a class of trajectories that uh would not let you go sailing off here into outer space where you would never never get connect uh back to the Earth uh you would stay in some very large peculiar Earth orbit if uh if you were on this kind of trajectory now as as Owen pointed out we had to lead the moon because when we made this Moon maneuver it was down here and it it was a very good analogy to ski shooting or maybe the quarterback throwing the the uh long pass of the wide receiver and the ball meeting up at the same place around the goaline so that uh this this characteristic here is one I'm going to talk about of how it affected our launch Windows can I have the next slide please uh we we've already discussed the free return trajectory and and I I just want to make the comment that that theoretically that is a uh a result of injecting here at exactly the right conditions but when you're adding something like 10,000 ft per second to your velocity and you need to make that accurate to within a very small fraction of a foot per second in order to achieve this from a practical standpoint it was it just couldn't be done or you couldn't guarantee it so uh there was theoretically this free return trajectory but in actual practice uh it it wasn't something that we could count on however because uh it was such a sensitive trajectory it took very small midcourse Corrections out here to bring it back into the free return and that freed us up from having to guarantee that the service propulsion system uh would work because that was the main engine that was used from here on out and in Earth orbit we had no way of checking that engine out as far as firing it to see that it worked we could check the uh all the system gauges and that sort of thing but you couldn't demonstrate that it was working and it was a real Comfort to know that uh we could send the crew and this spacecraft out here without uh having to guarantee that that we had a way around the problem so uh remembering now that that once we get into Earth orbit we want to go to this antipode position to to uh send the space spacecraft on its way to the Moon can I have the next slide want to talk briefly describe you the motion of this antipode because that's what we were trying to Rond rondevo with first was to to get to that point and there were two uh two types of motion the first one is that uh in the moon's orbit around the Earth the antipode of course then just traced a path like this around the earth uh and then every 28 days or so it would complete that and it's uh the latitude of this antipode would follow that kind of a a sine wave over the 28 days now the next slide this is the short period motion of the antio and really what it is in inertial uh in semi inertial uh conditions it's the the Earth spinning and the antipode pretty much staying the same uh but this is the the Earth's rotation and on the Earth to anyone on the earth it looked like the antio then was traveling at at a a retrograde Direction here at that a speed of about 15 Dees per hour so our problem then was to get off of the pad at the cape and Rond with this antipode and that was another reason why Earth orbits were were a big help because they helped uh give us a a a launch opportunity a launch window have the next slide okay this puts those two motions together and looks at at the geometry of the problem of Rend deing with that antipode and uh this is the track of the antipode around the Sur around the Earth in a inertial sense and that it moves in this direction at U fairly slow rate about a little over half degree per hour this is the latitude of the cape and the launch pad then is rotating around here with the Earth's Earth's rotation uh and at launching at a different times you can see that we would took different launch asmos to pass over uh the antipode so that we could do the trans lunar injection uh constraints on the launch asouth due to rain safety considerations kept us from launching any further north of du East than 72 degrees and any further south of du east of 108 degrees so we had about a 36 degree spread of launch asmos uh that we could use in order to provide us with a launch window as we were uh targeting or tracking this antipode and the Earth's rotation the next slide please okay this looks at at that uh situation in a on a Mercator projector projection map and I have the uh antio Trace moving across here uh as the Earth rotates uh this shows the ground track of of a 72° uh asouth launch and it picks up uh over here and then the 180 degree asouth launch here and picks up over here now as the antipode moves across then we as it approaches this point then we could launch and and meet up with it here uh if we had some problem that we were holding on the pad and and we could not get the launch off on time then we could still uh sit there in a whole condition and trace this targeting across here until it had got to this point in which point the window closed because we couldn't couldn't launch on an asmith down in here uh this was on the order of a 4-Hour uh time span here well you can see that the same situation occurred over here if we missed this window and then we could uh track the antio across here and pick it up again and another approximately 4H hour launch window for that day so that if if you just looked at this uh that the constraints of trying to get the uh High uh highly efficient trajectory to the Moon we had a two opportunities a day of each of about four hours in order to uh uh have a a launch window can have the next slide okay this this summarizes what that looks like throughout the year of 1969 the shaded areas are the times when we could not launch and the the open areas here are the launch opportunities see the time going from Midnight to midnight on any given day and the Atlantic uh ocean in uh window was the one that was over there in the Atlantic Ocean and then the P stands for the Pacific Ocean windows so if you look up through here on any one day you can see that there are two opportunities uh that occur throughout the year so that sounds really good uh but that's only the first constraint that we were dealing with but so now our 24-hour day is shrunk to a couple of 4-Hour periods can I have the next slide please Owen mentioned uh or maybe it was Joe mentioned this uh Sun elevation constraint of 7° to 20° and for angles less than 7° uh the Shadows across the lunar surface would be too long and uh and would hide some of the uh the the smaller craters and the boulders that we wanted the crew to be able to see and and not land on so we uh we were given a constraint of that the sun angle must be above 7° or it's it's going to have too much too many Shadows for good visibility above an angle of 20° however there was too much wash out there weren't enough shadows and they would not be able to see the undulations and and could possibly uh touch down in a very awkwardly sloping part of the surface so uh a 7 to 20° elevation at any given point at any given time says that this band around the Moon is the only place you can land on and see those characteristics meet those conditions uh and this uh Sunrise Terminator here this uh this is the uh the the shadow of the dark side and the sun being over here it moves across the lunar surface at this rate of about 15° per day so it says you subtract that you got 13° so on any any one Landing site is probably or guaranteed to only be available to you one day a month so now it's starting to really tighten down on what our launch opportunities were there the next slide and and this just uh shows that or summarizes that across the surface we got the the longitude uh this is the point that's pointing directly at the Earth the Zero longitude point and uh the trace of the 7° and the 20° Sun angles across that Laing uh those longitudes at a given for a given dates and uh so that on on in this time period here anything between these two longitudes was available as a landing site and as you look across there you can see that you'll only get one site a site available for for one particular day I can I have the next slide please well there was a lot of a a great deal of activity uh involved in selecting uh the lunar sites for a given Mission and it was involved uh the the geologists as well as the as the trajectory uh uh and Mission planning people and there was a lot of discussions in in uh even to the point of calling negotiations about how to come up uh with an accepted site there were certain things that that the uh the geologists and other scientists really wanted to uh to see and to do and uh it seemed like the trajectory of the mission planners were always the bad guys are trying to say we can't do that we can't get here it it doesn't give us enough launch opportunities and and there was just that a tremendous amount of of working together to come up with something that was acceptable as far as sites of interest to go to and and available uh launch opportunities uh this summarizes the launch opportunities for a a set of sites that were were just called Orbiter B sites there was another set that gave a different uh launch opportunity characteristics for the Year this is uh for the year 1969 and it's uh goes from uh January to the end of end of the year and December and for three selected sites out of the Orbiter B uh Suite of sites it shows one the uh the launch opportunities occurred throughout this year the solid lines are for the Pacific injections and the dotted lines are for Atlantic injections uh Dr craft threw another constraint in on us that he didn't want us launching uh Before Sunrise or after dark at the cape so that Drew a a line uh here that cut off anything outside of those periods so in January we really had no opportunities at all there was uh some amount coming in in February and then throughout the rest of the year we had three days until you get into December again uh in which we could uh launch and it just so happens that in 1969 uh these opportunities were all in the Pacific Ocean the Pacific Ocean window other years it worked out that they would all be in the Atlantic Ocean uh I think that's the last slide is is there one more ah okay that that's that's okay that was a different uh different subject that's that's all of the uh the launch window discussion uh and you can just take that kind of activity and the considerations that went into that very briefly discussed and apply that that uh throughout the mission every every Mission phase you got into and Everywhere You turned there was some significant amount of trajectory impact on what you could do and when you could do it we have time for a question don't see I think you've overwhelmed them Pete our next speaker will discuss the mission constraints and software compatibility he is Ron Barry who is now our director of the mission support directorate and who at the time of this Symposium was in the mission planning and Analysis division uh responsible for Mission constraints Ron thanks thanks Joe uh like uh like Pete I'm also happy to be here today and see all these familiar slightly older faces um and I'm pleased to be able to to help recreate the 66 Symposium I had the the privilege during that Symposium of being one of the presenters um it's quite a thrill for me believe me I was a kid just four years out of college I was not just uh wet behind the ears I was soggy and uh but here I was uh briefing uh this Auditorium uh pack to the gills with the uh best space mins in the country the managers scientists engineers and on this front row here were the Space Giants of the time you know we had Von braw Rees uh Gil Ruth Miller Shay and the whole bunch and so I was scared to death um but U I did manage to get through it and I even managed to answer a few of the questions that even the couple of the Space Giants threw at me and uh uh which it which in in in fact taught me one thing that uh uh you know Space Giants don't necessarily come equipped with all the answers but they are generally pretty good at asking the questions uh the but but that was an exhilarating time in one that I'll always remember um The Briefing Joe asked me to give today is was not the one that I gave that day it was it was uh the one that a gentleman by the name of Mars Jenkins gave who was one of my bosses at the time uh on on as Joe said the software considerations and constraints excuse me uh relative to the mission um the one I gave that day was on the return to Earth aboard analysis and planning and if time permits I might try to sneak a chart or two at the end of this from my briefing um to U make this is as faithful a recreation as possible I'll try to or I'll at least attempt to use present and future tenses instead of slipping into the past tense thing which is difficult to do and uh um