OVER THE HILL
Jack Riley was the Public Affairs Officer in Mission Control. “We’ve just had loss of signal as Apollo 11 passed behind the Moon. At that time we were showing its distance from the Moon as 309 nautical miles and its velocity with respect to the Moon as 7,664 feet per second. Here in the Control Center, two members of the backup crew, Bill Anders and Jim Lovell, have joined Bruce McCandless at the CapCom console. Fred Haise, the third member of the backup crew, just came in, too. And Deke Slayton, Director of Flight Crew Operations, is also present. The viewing room is filling up: among those on the front row are Tom Stafford, John Glenn, Gene Cernan, Dave Scott, Al Worden and Jack Swigert.’’
The inertial attitude of the vehicle was such that at its closest point of approach to the Moon the SPS engine would be facing the direction of motion, to serve as a brake. The CSM had redundant power buses, but in preparation for the burn these were ‘tied’ together to ensure that if one power supply were to fail this would not disrupt the operation of the systems at a critical time.
‘‘I’ve turned the S-Band volume down to get rid of that background noise,’’ Collins announced, ‘‘so don’t forget that we have to turn it back up on the other side!’’
With 2 minutes to go, they emerged from the Moon’s shadow. As they had been flying ‘on instruments’, Collins looked out of the window to visually confirm that they were in the correct attitude. ‘‘Yes, the Moon’s there, in all its splendour.’’
As they raced across the terminator, the deeply shadowed terrain appeared to be extremely rough. ‘‘Man,’’ exclaimed Aldrin, ‘‘look at it!’’
‘‘Don’t look at it!’’ said Armstrong, drawing their attention back inside. ‘‘Here we come up to ignition.’’
At 5 seconds to go, the computer flashed ‘99’ in the Verb display of the DSKY, to ask the crew whether they wished to go ahead with the burn as specified. ‘‘99’’, noted Collins.
‘‘Proceed,’’ commanded Armstrong.
Collins hit the PROCEED key to tell the computer to execute the manoeuvre. ‘‘Stand by for ignition.’’ Armstrong’s heart rate was 106 beats per minute, Collins’s was 66, and Aldrin’s was 70.
Two RCS thrusters fired briefly to settle the propellants in the main tanks, and then at the appointed time the computer ignited the SPS engine.
‘‘Burning!’’ confirmed Armstrong.
‘‘What’s our chamber pressure?’’ Collins asked.
The gauge was below the left FDAI. ‘‘It’s good, 95,’’ confirmed Armstrong.
‘‘The PUGS is oscillating around,’’ noted Aldrin. The Propellant Utilisation Gauging System measured how the engine was drawing fuel and oxidiser. Aldrin was to use a knob to maintain the correct combustion mixture, but this was tricky due to the lag in response.
‘‘Okay, we’re steering,’’ noted Collins. ‘‘The gimbals are a little busier than I’d have expected, but everything’s looking good.’’ The engine gave a load equivalent to one-fifth gravity. ‘‘The g feels sort of pleasant.’’
‘‘Tank pressures are good,’’ Aldrin confirmed.
“The chamber pressure is building up a little bit; 96 now,” Armstrong noted as he monitored the gauge.
“That’s a little more chamber pressure than they were predicting,” pointed out Collins, thinking of the miscalibration.
“Chamber pressure is continuing to rise,’’ added Armstrong a moment later, “it’s up to about 98 psi.’’
“We’re wandering off a little bit in roll, but that’s to be expected,’’ observed Collins. “It’s coming back.’’
The high chamber pressure would reduce the duration of the burn, but that was not the critical issue; what mattered was the change in velocity, and the computer would shut down the engine when the required 2,917.3-foot-per-second change in velocity had been attained. “Cutoff is going to be about 3 seconds early,’’ warned Aldrin.
“Nominal cutoff is at 6 + 02,’’ Collins noted, “so expect it around 6 minutes even, huh?’’
“I’m predicting 5 + 58, 4 seconds early,’’ said Armstrong. “Maybe 5 seconds.’’
“She’s steering like a champ,’’ Collins said. “The rates are wandering, but in all three axes they’re plus or minus 0.1 degree.’’
“Five seconds early, at 5 + 57,’’ Armstrong updated. “The chamber pressure is 100 psi even.’’
Collins counted down the seconds to the predicted cutoff.
“Shutdown!’’ confirmed Armstrong.
As they ran through the post-burn checklist, Collins prompted the computer to display the discrepancies between the desired and achieved velocity as measured in the three-coordinate system. “Minus 1, minus 1, plus 1; Jesus!’’ The ‘residuals’ were only 0.1 foot per second; the burn was essentially perfect. ‘‘I take back any bad things I ever said about MIT – which, of course, I never have.’’
Aldrin glanced out at the Moon. They were now well past the terminator and the terrain was well lit. ‘‘I have to vote with the Apollo 10 crew that the surface is brown.’’
‘‘It sure is,’’ agreed Collins.
‘‘It looks tan to me,’’ said Armstrong.
‘‘But when I first saw it, at the other Sun angle it looked grey,’’ Aldrin noted, referring to just prior to the burn. ‘‘It got more brown with increasing Sun angle.’’
Armstrong again drew his colleagues’ attention inside, ‘‘Alright, now we’ve got some things to do.’’
As they continued through the checklist, Collins said, ‘‘Well, I don’t know if we’re 60 miles or not, but at least we haven’t hit that mother.’’
The computer displayed the parameters of their orbit. ‘‘Look at that!’’ Aldrin exclaimed, ‘‘169.6 by 60.9.’’
‘‘Beautiful, beautiful, beautiful, beautiful!’’ enthused Collins. ‘‘Write it down just for the hell of it: 170 by 60, like gangbusters.’’
‘‘We only missed [apolune] by a couple of tenths of a mile,’’ Aldrin added in amazement.
It is not possible to orbit Earth at an altitude of 60 nautical miles, as this would be subject to the drag of the upper atmosphere. However, the Moon is airless. It is also smaller and less massive and, since its gravity is weaker, a spacecraft in orbit is not required to travel so fast. On the other hand, because the orbit is smaller, the period – at about 2 hours in this case – is only marginally longer than for a low orbit around Earth.
“Hello, Moon,” Collins greeted. “How’s the old back side?”
“Now,” said Armstrong, “the flight plan says we roll 180 degrees and pitch down 70 degrees.’’
“What are we pitching down for?’’ Collins asked. Then he laughed. “I don’t know what we’re doing.’’
Armstrong enlightened his CMP, “We’re going to roll over and pitch down so that we can look out the front windows down at the Moon!’’
“Oh, yes, okay,’’ Collins acknowledged.
As the spacecraft slowly executed the 180-degree roll, Collins asked, “Can we see the Earth on the horizon from here?’’
“We should be able to,’’ Armstrong replied.
Collins decided they should take a picture of their first Earthrise. “Big lens or small one?’’
“For the Earth coming up, we want the 250-millimetre,’’ decided Aldrin, as he started to assemble the Hasselblad. “Infinity, at f/11 and 1/250th, huh?’’
“Is it loaded with black-and-white, or colour?’’ asked Collins.
“Alrighty!’’ said Collins, satisfied.
“We ought to wash this window,’’ Aldrin said. “Anybody got a Kleenex?’’
Both Armstrong and Collins offered towels.
“Well, one more SPS burn,’’ Collins mused, thinking of completing the lunar orbit insertion sequence.
“Two more!’’ corrected Aldrin, remembering that the engine would also have to make the transearth injection burn if they were to get home.
Meanwhile, at home
Jan Armstrong had Barbara Young over for lunch. Having been through lunar orbit insertion on Apollo 10, Barbara described how she had had an anxious wait when her husband’s flight had reported back fully two minutes later than expected, raising the prospect of the burn having slowed that vehicle so much that it would crash. However, Jan was more concerned that AOS might be early, indicating that the burn had not occurred and the spacecraft was heading back to Earth on the free-return trajectory, because she knew that to lose the opportunity to attempt to land would be devastating for the crew’s morale. “Don’t you dare come around,’’ she muttered as the no-burn time approached. “Don’t you dare!’’ When that moment passed with no signal, she delightedly exclaimed “Yippee!’’
Back in space
“Look at those craters in a row. Something really peppered that one,’’ Collins said, drawing attention to the lunar surface. “There’s a lot less variation in colour than I would have thought, you know, looking down?’’
“But you’d say it’s brownish?” Aldrin asked.
“Oh, golly, there’s a huge, magnificent crater over here,’’ exclaimed Aldrin. “I wish I had the other lens on. God, that’s a big beauty. You should look at that guy, Neil.’’
“I see him,’’ Armstrong said.
“Well,” said Collins, “there’s really no doubt that the Moon is a little smaller than the Earth; look at that curvature.’’
Aldrin suggested that as they still had about 10 minutes to AOS, they ought to switch the Hasselblad to a ‘wider’ lens in order to shoot the lunar landscape.
“Just don’t miss that first one,’’ urged Collins, eager that they should record their first Earthrise.
The landscape passing below was fascinating.
‘‘What a spectacular view!’’ remarked Armstrong.
‘‘There’s a hole down here you just wouldn’t believe,’’ Collins pointed out. ‘‘And there’s the biggest one yet. God, it’s huge! It’s enormous! It’s so damned big I can’t even get it in the window! You want to look at that? That’s the biggest one you ever seen in your life. Neil? God, look at this central mountain peak.’’
Meanwhile in Houston, Jack Riley, continuing his public commentary, noted, ‘‘It’s very quiet here in Mission Control. Most of the controllers are seated at their consoles, several are standing up. We’re now 7 minutes from the acquisition time for the nominal burn. If Apollo 11 attained only a partial burn, we could receive a signal at any time.’’
‘‘Isn’t that a huge one?’’ Collins exclaimed, indicating another crater as they continued around the Moon’s far side. ‘‘It’s fantastic! Oh, boy, you could spend a lifetime just geologising that one crater alone!’’ After pausing to reflect, he added, ‘‘Although that’s not how I would like to spend my lifetime!’’
‘‘There’s a big mother over here, too,’’ Aldrin pointed out.
‘‘Come on now, Buzz,’’ Collins chastised, ‘‘don’t refer to them as ‘big mothers’ – give them some scientific names.’’
‘‘It sure looks like a lot of them have slumped down,’’ noted Aldrin, referring to the terraced rims of the craters, which had indeed slumped into the pit.
‘‘A slumping big mother!’’ exclaimed Collins. ‘‘Well, you see those every once in a while.’’
‘‘Most of them are slumping,’’ continued Aldrin, ignoring Collins. ‘‘The bigger they are, the more they slump.’’
‘‘We’re at 180 degrees,’’ announced Armstrong as he terminated the roll, ‘‘and now we start a slow pitch down about 70 degrees.’’
‘‘We’ve got 4 minutes to get pitched down before AOS,’’ pointed out Aldrin. ‘‘We’ll never make it.’’
‘‘Goddamn, a geologist up here would just go crazy,’’ suggested Collins. ‘‘We shouldn’t take any more pictures on this roll until we get Earth.’’
‘‘We might make it in time,’’ said Armstrong, referring to the timing of their pitch manoeuvre.
‘‘There it is,’’ exclaimed Aldrin. ‘‘It’s coming up!’’
“What is?” Collins asked.
“The Earth!” explained Aldrin. “See it?”
“It’s halfway up already,” Aldrin noted. He snapped a picture, but not having changed back to the 250-millimetre lens it was not the close up Collins desired. “We ought to have AOS now,’’ Armstrong pointed out.
The antenna in Madrid acquired the carrier signal right on time, indicating a good burn.
“AOS!” Riley announced to the public.
“Apollo 11, this is Houston. Do you read?’’ prompted McCandless. Although Armstrong replied with a full burn report, the high-gain antenna had yet to lock on and the transmission by omnidirectional antenna was so noisy that he was mostly unintelligible. “Could you repeat your burn status report?’’ McCandless requested. “It was perfect!’’ Armstrong replied simply.
Once the high-gain link had been established, the flight controllers examined the telemetry. Going ‘over the hill’, the combined mass of the two spacecraft was 96,012 pounds. The LOI-1 burn had consumed 24,008 pounds of propellant.
Meanwhile, at home
Joan Aldrin, who was at the hair-dresser, was listening to the radio coverage of the mission. In her house, Rusty Schweickart was explaining to the assembled crowd that the manoeuvre had gone to plan.