This is part 2 of a special Space Sunday series, celebrating the 50th anniversary of Apollo 11 landing on the Moon, and follows on directly from Part 1: “Lift-off! We Have Lift-off!” It was published on Saturday, July 20th, 2019, as a Space Sunday special to mark the actual date of that historic landing.
Part 2: “The Eagle Has landed”
Once the combined Command and Service Module (CSM) and Apollo Lunar Module (CM) were free of the Saturn V’s S-IVB stage, they were in constant sunlight, so to help better regulate their internal and external temperatures, the reaction control system on the CSM was used to set both vehicles spinning very gently along their longitudinal axis in what was called the “Apollo barbecue roll”.
During this “cruise phase” of the flight, the three men aboard Apollo 11 – Armstrong, Collins and Aldrin – had to perform a range of activities from keeping an eye on their spacecraft through to making broadcasts back to Earth. It was here that their curious relationship came a little to the fore.
While all three men got along very well, they were observed not to bond in the manner of other crews; all three were somewhat quiet men, with Collins and Aldrin particularly coming to refer to their relationships with one to the others as that of “amiable strangers”.
Which is not to say the three men didn’t get along; almost all of the on-board conversations were recorded by NASA, even if they weren’t broadcast, and these “off-air” conversations reveal the three men shared jokes – such as Aldrin and Collins gently teasing Armstrong about his “rookie” status in having clocked the fewest number of hours in space. However, when it came to talking for the benefit of the television audience, Mission Control sometimes had to coax words out of the crew.
The first time we saw the Moon up close, it was a magnificent spectacle. It was huge. The Sun was coming around it, cascading and making a golden halo and filled out entire window. [But] as impressive as the view was of this alien Moon seen up close was, it was nothing compared to the sight of the tiny Earth. The Earth was the main show. The Earth was it.
– Michael Collins, 50th anniversary of the Moon landing
Apollo 11 reached the Moon on July 19th, 1969, after a single mid-course corrections using the single motor of the Service Module (out of 4 planned for the flight).
Now Collins again took the controls to gently pivot the vehicles around in their own length, so that single large motor was pointing forward along their line of flight. Then, at 17:21:50 UTC, as they passed around the Moon’s far side, the engine was fired in the first of two orbital insertion burns.
This first engine burn slowed the vehicles so they they were snagged by the Moon’s gravity and placed in an elliptical orbit. A second burn of the engine followed 4 hours and 22 minutes later, circularising the vehicle’s orbit in readiness for Armstrong and Aldrin to make their historic descent.
In all thirty orbits of the Moon were performed as the Lunar Module was prepared for its descent and landing. These orbits frequently passed over the Mare Tranquillitatis, a large basalt plain on the Moon selected as the location for the first manned landing by the United States as it appeared from orbital imaging as being relatively smooth, and had already seen a successful landing by the automated Surveyor 5 mission, which arrived on the Moon on September 11th, 1967.
Shortly after Apollo 11 dropped into orbit around the moon, Frank Borman got a message from the Soviet Union that said, “Congratulations on reaching lunar orbit. We have Luna 15 also in orbit around the moon and its orbital parameters are such and such. If it presents any problem, please advise and we will move it.” We didn’t need Luna 16 moved, but I thought it was a noble gesture in those days of the Cold War.
– Bruce McCandless, Capsule Communicator (CapCom),
Apollo 11 Mission Control Green Team
At 12:52:00 UTC on July 20th, Aldrin and Armstrong entered Eagle, and began the final preparations for lunar descent, Five hours later, all was set and they undocked from the Command Module Columbia. With Michael Collins in the Command Module, Armstrong gently eased Eagle away from the CSM, then used its reaction control system to perform a slow pirouette. This allowed Collins to carry out a visual inspection of the LM, confirm its legs were deployed and that it was generally looked OK to make its decent.
For the first part of the decent, Eagle was effectively “face down” giving Armstrong and Aldrin a view of the Moon. Then the descent engine fired and the vehicle slowly moved to an upright position, and Armstrong voiced a slight concern.
We’re about a minute, maybe 2 minutes, into powered descent, face-down, and Neil says to me, and the Earth, “I think we’re gonna be a little long.” I said to myself, how in the world can he really, at this point, tell that we’re gonna be a little long? But sure enough, we were. I’ve learned that whenever Neil says anything, you’d better pay attention because there’s good meaning to it.
– Buzz Aldrin commenting on the Eagle’s descent to its landing
Armstrong had actually been using the angular rate the LM passed over the craters they could see to mentally calculate the Eagle’s altitude, and by the time the decent motor fired – timed to occur at a specific altitude – he realised the LM was further west than its landing track indicated should be the case. But this turned out to be the least of the men’s immediate worries: they were about to hit the infamous “1202 alarm”.
Essentially, the LM’s flight computer had a limited amount of data it could store (essentially 12 “words” at a time. The “1202” alarm indicated an “executive overflow” – the computer was receiving more data than it could handle, and could not complete all its tasks in real time, so had to postpone some of them – with error code 1202. The problem was, no-one actually knew the root cause of a “1202” error and whether it indicated a landing aboard was required.
Fortunately, Jack Garman, a computer engineer at Mission Control, did recall reading computer could recover from a “1202” and its sister “1201” error, providing it didn’t become a continuous error. Thus, the order was given to press on with landing. Several more 1202s and a 1201 followed, allowing Aldrin to correlate them with the computer’s attempts to provide data on the LM’s range to the landing site and its velocity. Solution: stop the computer from trying to provide this information, and request it directly from Mission Control. (Subsequent investigations later revealed the problem was the result of a hardware design error causing data to be repeatedly sent to the guidance computer from a power bus, filling the data cores the range and velocity data was also trying to access.)
With that excitement dealt with, Armstrong’s prediction that the LM was going to go “long” and overshoot the landing zone proved correct: the computer was steering Eagle to a landing in a boulder field well beyond the planned landing area.
Taking full control, and with Aldrin relaying flight data, Armstrong steered Eagle towards what seemed to be clear ground – only to discover it contained a shadowed crater that might contain harmful boulders. A second landing spot was identified, but as Armstrong descended over it, only for dust kicked up by the descent motor to obscure his view. Fortunately, he’d identified three large boulders on the edges of the new landing area and as their tops remained visible above the dust, he used them to guide himself in for landing.
Then a light informed Aldrin that at least one of the 67-inch (170 cm) probes hanging from Eagle‘s footpads had touched the surface. “Contact light!” he announced, the command for Armstrong to cut the motors. Such was his concentration, Armstrong either didn’t hear Aldrin or simply forgot: he didn’t react to shutting the motor off for a full three seconds, by which time all four landing pads were on the surface. The Eagle had landed at 20:17:40 UTC on Sunday July 20th, 1969, with fuel for just 50 seconds of flight power left in the descent engine tanks (although the instruments indicated only 30 seconds).
Shortly after landing the all-clear (“T1”) was given for the two men to stay on the lunar surface, and with all post-landing checks completed, Aldrin, a devout Presbyterian, took communion, giving thanks for their safe arrival on the Moon. It had been agreed that Aldrin wouldn’t reference the fact he was doing so directly, but would instead say a few simple words. At the time NASA was fighting a lawsuit brought by atheist Madalyn Murray O’Hair, in the wake of the Apollo 8 crew marking Christmas 1968 by reading a passage from Genesis as they flew around the Moon. However, lawsuit concerns didn’t stop CBS News anchor Walter Cronkite spilling the beans on US national TV as Aldrin made his simple statement!
This is the LM pilot. I’d like to take this opportunity to ask every person listening in, whoever and wherever they may be, to pause for a moment and contemplate the events of the past few hours and to give thanks in his or her own way.
– Buzz Aldrin, July 20th, 1969, from the surface of the Moon
Originally, the mission called for Aldrin and Armstrong to get some 5 hours sleep before attempting an EVA – extra vehicular activity – on the surface of the Moon. But Aldrin and Armstrong were just too excited, so Mission Control relented and gave the order for the two men to start their EVA preparations.
Preparations for the EVA took longer than expected: 3.5 hours rather than the planned two, with the two men helping one another into their EVA equipment and then checking one another carefully. However, with everything ready, the two men prepared to de-pressurise the LM’s cabin – there was no airlock, only a hatch – so the hatch could be opened in readiness for Armstrong’s descent to the Moon’s surface.
It was this part of the mission that might have given rise to some of the coolness that existed between Aldrin and Armstrong. Under normal NASA mission protocols, the commander of a mission – Armstrong in this case – was expected to remain within the vehicle while any initial EVA was carried out by the pilot – Aldrin. However, ahead of the mission, the decision was made to have Armstrong be the first out of the LM.
Aldrin did not take the news well, and tried to get the other LM pilots to stand with him and get the decision reversed. They declined, believing his attempts as a lobbying exercise for his own benefit. His views were also not welcomed by future Apollo lunar mission commanders, who would benefit from the “commander first” decision in their turn.
Donald “Deke” Slayton, Chief of the Astronaut Office tried to prevent the rift from spreading by taking both Aldrin and Armstrong aside to formally tell them Armstrong would be the first out of the LM ahead of a press conference on April 14th, 1969, but in many respects. the damage had been done.
Buzz resents not being first on the moon more than he appreciates being second.
– Michael Collins, Carrying the Fire: An Astronaut’s Journeys, 1974
The official reason for the switch was that the interior design of the LM made it easier for the man to the left of the egress hatch – the commander – to get out first. Indeed, during simulations on Earth, Aldrin had damaged the hatch on the LM trying to egress ahead of Armstrong. However, in his 2001 autobiography, Chris Kraft revealed that he and his boss Robert Gilruth (respectively the then Deputy Director and Director of the Manned Spacecraft Centre, now the Johnson Space Centre, and the two most powerful men in NASA manned spaceflight programme) insisted Armstrong be the first man to set foot on the Moon, as they deemed his persona to be more in keeping with that of pioneering aviator Charles Lindbergh.
There were some genuine concerns as to what might happen when the Eagle’s hatch was opened: was the lunar dust pyrophoric and liable to explode if it came in contact with trace oxygen within the LM? Might the LM actually settled some way into the dust after landing, preventing a safe EVA? And so on. However, the only way to find out was to get out of the LM.
Eagle‘s hatch was opened at 02:39:33 UTC, on Monday, July 21st, 1969 (still Sunday, July 20th in the United States), and Armstrong initially had some difficulties squeezing through the hatch with his portable life support system (PLSS) backpack – so much so that he didn’t start his descent down the ladder affixed to the LM’s landing leg strut directly under the hatch until 11 minutes later.
Reaching the bottom of the ladder, Armstrong faced a slight problem. As it had been assumed the Lunar Module would sink somewhat in the lunar dust on landing, the ladder ended a little high on the LM’s leg. As it was, the Lunar Module barely settled into the dust before coming to rest on a solid surface, leaving a sizeable gap between the ladder’s lowest rung and the LM’s footpad Armstrong had to jump down. Such was the distance, he decided to check how easy it was to jump back onto the ladder, reporting it to be “adequate to get back up”.
For a moment he stood on the pad, giving an almost clinical description of his surroundings. Then with a pause, he announced, “OK I’m going to step off the LEM now…” before gingerly placing a boot on the surface of the Moon.
That’s one small step for [a] man. One giant leap for mankind.
– Neil A. Armstrong, from the surface of the Moon,
July 20th/21st, 1969