Descent Orbit Insertion

During Eagle's near-side pass on revolution 13, Gene Kranz polled his team on the descent orbit insertion (DOI) manoeuvre. After studying their telemetry, the flight controllers pronounced Eagle to be in excellent condition, and 10 minutes before it went 'over the hill' Duke relayed the decision to proceed.

Kranz recalled of this loss of signal, ''the adrenaline, no matter how you tried to hide it, was really starting to pump''. He instructed his team to ''take five'', thereby prompting an exodus to the toilets. ''You're standing in line, and for once there isn't the normal banter - no joking. The preoccupation is the first thing that hits you. Today is different.'' This was no simulation! ''This is the day we're either going to land, abort or crash - the only three alternatives." While Apollo 11 was behind the Moon, the flight control team was rearranged to handle Columbia and Eagle in parallel, using independent communications links and telemetry - although the same CapCom. Spencer Gardner, monitoring the flight plan, ensured that this transition was done in an orderly manner.

The glassed-in viewing room of the Mission Operations Control Room had 74 seats, but it was a case of turn up early or stand in the aisles. As Douglas K. Ward, the Public Affairs Officer for the White Team, observed: ''I believe in the viewing room we probably have one of the largest assemblages of space officials ever seen in one place.'' They included Thomas O. Paine, NASA Administrator; Abraham Silverstein, Director of NASA's Lewis Research Center; James C. Elms, Director of the Electronics Research Center in Massachusetts; Kurt H. Debus, Director of the Kennedy Space Center; Rocco A. Petrone, Director of Launch Operations; Edgar M. Cortright, Director of the Langley Research Center; Wernher von Braun, Director of the Marshall Space Center; Eberhard F.M. Rees, von Braun's deputy; John C. Houbolt, who championed the use of the lunar orbit rendezvous mission mode; and Charles Stark Draper, Director of the Instrumentation Laboratory at the Massachusetts Institute of Technology. A large number of astronauts including Tom Stafford, Gene Cernan and Jim McDivitt were in the viewing room, together with former astronaut John Glenn. On Management Row of the main floor, were Robert R. Gilruth, Director of the Manned Spacecraft Center; Samuel C. Phillips, Apollo

Program Director; Robert C. Seamans, formerly Deputy Administrator of NASA, now Secretary of the Air Force; Christopher C. Kraft, Director of Flight Operations; and George M. Low, Apollo Spacecraft Program Manager.

The control room was considerably smaller than it appeared on television and, being in constant use, reeked of smoke, pizza, stale sandwiches and coffee burned onto hot plates. It comprised four rows of consoles, rising successively to the rear. Each console had one or two display units which, while there was telemetry from the spacecraft, presented alpha-numerical data on a television screen that refreshed once per second. All of the flight controllers were male. Each wore a headset with an earpiece and microphone plugged into his console, and needed to monitor several intercom loops simultaneously, with his principal loop at a higher volume.

Irrespective of their seniority in NASA, at this point the VIPs had the status of observers; the same applied to Management Row. The flight director had absolute authority and, with it, total responsibility. He, in turn, relied on his team of flight controllers. The average age of the White Team for this mission was 26 years; Kranz was 35 years of age and Kraft was 45. Although America's manned space program was barely a decade old, the people on the control room floor this day, 20 July 1969, represented three generations in the flight control business.

As chief of the flight dynamics branch, Jerry C. Bostick supervised the team in the 'Trench', as the front row was informally known. Knowing Kranz to be 'weak' on trajectories, Bostick assigned Jay H. Greene as his flight dynamics officer (call sign 'FIDO'). A pipe-smoker with a heavy Brooklyn accent, Greene was thoroughly knowledgeable on trajectory issues. During the powered descent his job would be to monitor the Manned Space Flight Network's tracking of Eagle. To his left was the retrofire officer (call sign 'Retro'), Charles F. 'Chuck' Deiterich, who wore a large moustache and had a Texas drawl. To Greene's right sat Steven G. Bales (call sign 'Guidance'), whose job was to monitor Eagle's guidance systems, particularly the computer and landing radar. As one of the first generation of computer graduates hired by the agency straight out of college, Bales had more in common with the 'systems' people in the row behind. He wore dark-rimmed glasses, spoke rapidly, and the inflection in his voice was an indicator to his state of mind. Today was his 27th birthday. Granville E. Paules was to assist Bales to monitor Eagle's systems. Tall, blond and taciturn, Paules had the unusual habit of turning to face his interlocutor on the intercom; like Bales, he was young and systems minded.1

The flight surgeon for this shift, John F. Zieglschmid, had a console on the far left of the second row. To his right sat Charlie Duke, a South Carolinan with an associated drawl. Duke became an astronaut in 1966 but had yet to be assigned a specific mission. Kranz considered him to be unique among the astronauts, in that he would have made an excellent flight director. His assignment to the White Team was no fluke. ''To be a good CapCom,'' Duke would later explain, ''you've got to know the procedures used by the crew, the software, and the flow of information to the

1 The character sketches of the White Team are courtesy of Gene Kranz.

Gene Kranz

The White Team formed for the Apollo 11 lunar landing. Left to right (front row) Don Puddy, Bob Carlton, Gene Kranz, Charlie Duke, John Zieglschmid, Captain George Ojalehto, Spencer Gardner, Frank Edelin, Arnie Aldrich and Buck Willoughby; (back row) John Aaron, Dick Brown, Chuck Lewis, Larry Armstrong, Bill Blair, Ed Fendell, Jim Hannigan, Jerry Bostick, Jay Greene, Gran Paules, Steve Bales, Chuck Deiterich and Doug Wilson. (Courtesy of Gene Kranz)

The White Team formed for the Apollo 11 lunar landing. Left to right (front row) Don Puddy, Bob Carlton, Gene Kranz, Charlie Duke, John Zieglschmid, Captain George Ojalehto, Spencer Gardner, Frank Edelin, Arnie Aldrich and Buck Willoughby; (back row) John Aaron, Dick Brown, Chuck Lewis, Larry Armstrong, Bill Blair, Ed Fendell, Jim Hannigan, Jerry Bostick, Jay Greene, Gran Paules, Steve Bales, Chuck Deiterich and Doug Wilson. (Courtesy of Gene Kranz)

crew." As his astronaut specialism, Duke had monitored the development of the LM propulsion systems. On Apollo 10, Tom Stafford had asked Duke to be prime CapCom, and Duke had helped to develop the time line for checking out the LM. Armstrong had asked Slayton to have Duke do the same for Apollo 11, and then follow through with the powered descent. Duke joked that he had been given the job for the simple reason that he was the astronaut most knowledgeable of the LM who wasn't already on a crew! The systems controllers occupied a set of consoles on the right of the second row. Looking after Columbia were John W. Aaron, the electrical, environmental and communications officer (call sign 'EECOM') and Briggs W. 'Buck' Willoughby, the guidance, navigation and control officer (call sign 'GNC'). The equivalent of EECOM for Eagle was Donald R. Puddy (call sign 'TELCOM'). A tall, intense Oklahoman who never wasted a word, Puddy joined NASA from college. On the far right was Eagle's equivalent of GNC, Robert Carlton (call sign 'Control'). Dubbed the 'Silver Fox' owing to his prematurely greying hair, Carlton was dry, deliberate and unperturbable. To Kranz's left on the third row was Charles R. 'Chuck' Lewis, a college graduate who had initially been a remote-site CapCom for the Gemini flights. As assistant flight director (call sign 'AFD') Lewis was, in effect, Kranz's 'wing man', monitoring, and ready to deal with issues that occurred while Kranz was busy. At Lewis's left, Edward I. Fendell (call sign 'INCO') was working to consolidate instrumentation and communications into a single console, although at the time of Apollo 11 some of these tasks were still with EECOM and TELCOM. The 'core' of the team for the powered descent was Bales, Paules, Greene and Deiterich in the front row, Puddy, Carlton and Duke in the second row, and Kranz in the third row.

Once the flight controllers had resumed their consoles, Kranz directed them to switch to the assistant flight director's intercom loop, which was not available to the viewing gallery, in order to speak to them privately. Unfortunately, his speech was not recorded. On one occasion Kranz recalled, ''I had to tell these kids how proud I was of the work that they'd done; that on this day, from the time that they were born, they were destined to be here and destined to do this job; they were the best team ever assembled and today, without a doubt, they were going to write the history books by being the team that took an American to the Moon.'' On another occasion he recalled saying, ''Okay, all flight controllers, listen up. Today is our day, and the hopes and dreams of the entire world are with us. This is our time and our place, and we will remember this day and what we will do here always. In the next hour we will do something that has never been done before - we will land an American on the Moon! The risks are high, but that is the nature of our work. We have worked long hours and had some tough times, but we've mastered our work. Now we are going to make that pay off. You are a hell of a good team; one that I feel privileged to lead. Whatever happens, I'll stand behind every call you make. Good luck, and God bless us today!'' As a management interface between the flight controllers and the industrial community, Thomas J. Kelly, who led the Grumman team that developed Eagle, Dale D. Myers, his counterpart at North American Rockwell for Columbia, and senior executives of other hardware suppliers, sat at consoles in the Spacecraft Analysis Room along the corridor from the Mission Operations Control Room. Each company had engineers in other support rooms at the Manned Spacecraft Center, as well as at their own plants, and their key engineers were 'on call' to receive telephone messages wherever they might be.

With acquisition of signal imminent, Kranz ordered the doors of the MOCR locked, which was standard procedure for critical phases of a mission. He also ordered ''battle short'', in which the main circuit breakers for Building 30 were physically jammed in position to prevent an inadvertently tripped breaker from cutting the power. In fact, Building 30 comprised a pair of interlinked structures, one of conventional design housing offices and the other, a windowless concrete box, housing the control facilities. As Kranz put it, if a fire were to break out in one of the offices he would rather let it burn than have the automatic protective systems cut the power.2 The display on the front wall was set to compare Eagle's onboard guidance

2 The ground level of Mission Control held the Real-Time Computer Complex, and each of the two upper levels held a Mission Operations Control Room. Apollo 11 was managed from the top level.

Descent Orbit Insertion

systems with tracking provided by the Manned Space Flight Network. Although headphone sockets were at a premium, Deke Slayton was with Duke at the CapCom console. Jim Lovell and Fred Haise of the backup crew were nearby, as were Pete Conrad, who was to command the next mission, and Dave Scott, his backup. The simulation room was packed with people who were unable to find a socket on the main floor. As Kranz later expressed it, being in the Control Room during a flight was second best only to being in the spacecraft. Mission Control's photographer, Andrew Patnesky, was snapping away from a position just behind the CapCom's console, from where he had a good view across the room. In addition, artist Bob McCall was unobtrusively sketching with pencil on paper.

Observing the growing sense of apprehension, George Low said to Chris Kraft, ''I've never seen things so tense around here.''

At undocking, Columbia's mass was 36,651 pounds, and Eagle's was 33,627 pounds. In terms of dry mass, the ascent stage, at 4,804 pounds, was 321 pounds heavier than the descent stage. The descent propulsion system had 18,000 pounds of propellants. The ascent stage had 5,214 pounds of propellant for its main engine and an initial load of 604 pounds of propellant for the attitude control system.

At 101:36, some 180 degrees after the separation manoeuvre, and about 2 pm in Houston, Eagle fired its thrusters for 7 seconds to slow down and impart a force to settle the propellants in the main tanks. The first 15 seconds of the DOI burn were made with the DPS throttle at 10 per cent of its designed power of 10,500 pounds of thrust, during which time the engine was gimballed to aim the thrust through the centre of mass of the vehicle, then the computer opened the throttle to 40 per cent until it had accomplished the requisite 76.4-foot-per second retrograde manoeuvre -nominally after a total duration of 29.6 seconds. Since there was no sound or vibration from the engine at the 10 per cent level, the instruments gave the only indication that Armstrong and Aldrin had to confirm ignition, but when it throttled up they felt a sagging in their knees. To restrain them while 'standing' during manoeuvres, the soles of the boots of their suits had velcro to engage with strips on the floor, and they secured themselves by spring-loaded harnesses affixed to loops at their waists. If they needed to brace themselves, they had wall bars, and there were armrests for the hand controllers. The descent orbit had its apolune at 57.2 nautical miles, and its perilune at 8.5 nautical miles or, as the crew thought of it, 50,000 feet. Because the manoeuvre was made 7 minutes after going 'over the hill', the perilune would be above the Sea of Tranquility, some 16 degrees (260 nautical miles) east of the landing site, whereupon, if all was well, Eagle would initiate the powered descent. Until that moment Armstrong and Aldrin would be retracing the trail blazed by Apollo 10.

As Eagle lost altitude in the descent orbit, it speeded up and drew ahead. As it continued downhill, its primary guidance and navigation system (PGNS) was told to manoeuvre the vehicle into an attitude calculated to place the Sun in the field of view of the navigational telescope. If the cross hair was centred on the solar disk (which spanned half a degree of arc) this would confirm that the platform had not drifted from the alignment lifted from Columbia as part of the pre-undocking procedure. If it had drifted significantly, the platform would have to be realigned by making star sightings, which would take time. As long as the cross hair was well onto the solar disk Armstrong would accept the alignment; and this proved to be the case. Aldrin then verified that the abort guidance system (AGS), which utilised body-mounted gyroscopes instead of an inertial platform, was in satisfactory agreement with the PGNS. Meanwhile, Collins used his sextant to monitor Eagle as it drew away, to verify that he would be able to make accurate long-range sightings should he have to rescue the LM. At the time of the DOI burn the vehicles were about 1,100 feet apart, and although Eagle drew ahead as it descended towards perilune, Columbia, orbiting higher, was first to acquire a line of sight to Earth. By design, there was redundancy in coverage, because although the Moon would soon set for Madrid it had already risen at Goldstone.

''Columbia, Houston,'' called Duke. ''We're standing by.'' ''Reading you loud and clear,'' replied Collins. ''How me?'' ''Five-by-five, Mike,'' responded Duke, using radio code for 'loud and clear'. ''How did it go?''

''Everything's going just swimmingly. Beautiful.'' ''Great. We're standing by for Eagle,'' said Duke. ''He's coming along.''

''We expect to lose your high-gain some time during the powered descent.'' ''You don't much care, do you?'' observed Collins. ''No, sir.''

Because Collins was tracking Eagle using his sextant, his attitude relative to Earth was changing, and although the boom-mounted high-gain antenna was gimballed, at some stage during the manoeuvre its field of view would be blocked and Columbia would have to switch to omnidirectional antennas, at which time telemetry would be impaired.

Almost 2 minutes after Columbia appeared, Eagle, now down to 18 nautical miles, reported in.

''We're standing by for your burn report,'' Duke prompted. ''The burn was on time,'' replied Aldrin.

''We're off to a good start,'' Kranz told his team. ''Play it cool.'' At AOS, Joan Aldrin left the couch to stand by the fire place, laid her forearms on the mantelpiece and rested her head on her hands. Clare Schweickart made her husband, Rusty, promise to alert everyone if he heard anything untoward over the squawk box. Rusty sat with Gerry Carr, flight plan open. Aldrin's son, Mike, was upstairs, watching on another television on his own.

Communications with Eagle were poor, with static on the voice downlink and the telemetry becoming intermittent, or 'ratty' in the parlance of the flight controllers. ''Columbia, Houston,'' Duke called. ''We've lost all data with Eagle. Please have him reacquire on the high-gain.''

''Eagle, this is Columbia. Houston would like you to reacquire on the high-gain. They've lost data.'' No response. ''Eagle, did you copy Columbia?''

Aldrin adjusted the system that was to steer the antenna in order to maintain the strongest signal strength, and the static cleared. ''How do you read us now?'' ''Five-by,'' replied Duke.

The manoeuvres required to enable Eagle to land on the Moon.

There were 13 minutes remaining to powered descent initiation (PDI). The crew of Eagle were now flying 'feet first' and 'windows down' to enable Armstrong to check the landmarks surveyed by previous missions. This not only confirmed their ground track, but also provided an estimate of their altitude as a perilune check. That is, by using a stop watch to measure the intervals taken by a series of landmarks to pass between the angular reference marks inscribed on his window, reading their speed from the computer, and referring to a chart prepared by Floyd Bennett, a guidance engineer in Houston, he could estimate their current altitude and, by extrapolating, estimate what it would be at perilune. This manual technique could measure this vital parameter more accurately than Manned Space Flight Network tracking. Meanwhile, Aldrin was using the rendezvous radar to measure the range to Columbia in order to calculate their altitude relative to that spacecraft's orbit. If they were to initiate the descent from too high a point, then Eagle would run out of fuel before it could finish the descent. It was concluded that perilune would occur at an altitude of 51,000 feet and just prior to the PDI point, which was about as good as anyone could have hoped. If the perilune had been too high, Eagle would have had to forgo PDI on this pass and perform a manoeuvre at apolune to trim the perilune in order to try again on the next pass. Collins had been tracking Eagle using his sextant, but in the run up to PDI, with the separation now 100 nautical miles and the LM just a tiny dot moving rapidly against the backdrop of the sunlit lunar landscape, he lost it.

The Go/No-Go decision for PDI was scheduled for 5 minutes after coming around the limb, during which interval the flight controllers were to make a final check of Eagle's systems. However, with the decision imminent, communications deteriorated again. ''Columbia, Houston,'' Duke called. ''We've lost Eagle again. Have him try the high-gain.''

''Eagle, this is Columbia. Houston has lost you again. They're requesting another try at the high-gain.'' The signal improved.

''I don't know what the problem was there,'' Aldrin said. There was a display on board to indicate how the antenna was steering to maintain the strongest possible signal. ''The steerable just started oscillating around in yaw.'' ''We'll work on it,'' promised Duke.

The intermittent communications were worrying. In view of the high number of crashes during simulations, Kranz had added a mission rule that there must be adequate telemetry to enable an investigation to determine the reason for a crash. He added another rule that it would be up to the flight director to decide whether this condition was satisfied. As with the voice link, the telemetry was 'dropping out' and the flight controllers' screens were freezing, and without their telemetry the flight controllers could not reach a judgement. Power constraints permitted PDI only on two consecutive perilune passes after DOI. One option (in the absence of other concerns) was to proceed with the descent and re-evaluate after 5 minutes whether to push on or to abort. Kranz faced having to decide whether it would be better to pursue this option and possibly end up aborting, or to 'wave off in the hope that communications might have improved by the next pass.

Reasoning that with Eagle 'windows down', the steerable antenna on a boom on the right-hand side of the vehicle might have difficulty seeing around the body of the spacecraft to gain a clear line of sight to Earth, Pete Conrad suggested to Duke that Eagle make a slight yaw manoeuvre to improve the geometry.3,4 Duke passed this on to Kranz, who asked Puddy, who agreed. Duke then called, ''Eagle, Houston. We recommend you yaw 10 degrees right in order to help us on the high-gain signal strength.'' There was no response from Eagle, and the static continued. Kranz gave his team another 30 seconds to inspect the most recent telemetry, then announced, ''Okay all flight controllers, Go/No-Go for powered descent. Retro?"

Go!'' replied



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