Home in triumph

LIFTOFF AND RENDEZVOUS

Flight day 6, Monday, 21 July, started at 121 hours elapsed time with Ron Evans making his wake-up call to Columbia. In fact, Collins was already awake and was having his breakfast. Because Columbia was only a few minutes from going ‘over the hill’, Evans launched straight into updates to the flight plan which promised to keep Collins ‘‘a little busy’’: while in the Moon’s shadow he was to perform a P52 to align the inertial platform, and then, on starting the near-side pass of revolution 23, he was to track crater 130-prime in order to measure the plane of his orbit accurately prior to rendezvous.

Meanwhile, Evans called Eagle, ‘‘Tranquility Base, Houston.’’

‘‘Good morning,’’ replied Armstrong promptly.

When Evans asked how they had spent the night in the cramped cabin, Aldrin replied, ‘‘Neil rigged himself a really good hammock with a waist tether, and he’s been lying on the ascent engine cover. I curled up on the floor.’’ For breakfast they had bacon squares, peaches, sugar cookie cubes, and a drink made from pineapple and grapefruit.

In view of the program alarms during the descent indicating that the computer had been overloaded, and the fact that the ‘duty cycle’ would be 15 per cent greater during the ascent, Mission Control had decided to leave the rendezvous radar off until they reached orbit. As Columbia flew overhead on revolution 24, Eagle tested its rendezvous radar by tracking the CSM’s transponder. The inertial platform of the PGNS, which had lost its reference when powered down at the ‘T3’ milestone following landing, was aligned by taking star sightings with the telescope.

‘‘Eagle and Columbia, this is the backup crew,’’ announced Jim Lovell. ‘‘Our congratulations for yesterday’s performance, and our prayers are with you for the rendezvous.’’

‘‘Thank you kindly, Jim,’’ replied Armstrong.

‘‘Thank you, Jim,’’ Aldrin concurred.

‘‘We’re glad to have y’all looking over our shoulders,’’ Collins added.

As they waited for the appointed time to lift off, Armstrong called, ‘‘Houston, Tranquility Base is going to give you a few comments with regard to the geology

question of last night. We landed in a relatively smooth field of secondary craters, most of which have raised rims irrespective of their size, but that’s not universally true because a few of the smaller craters don’t have a discernible rim. The ground mass throughout the area is a very fine sand to a silt. I’d say the thing that would be most like it on Earth is powdered graphite. Immersed in this ground mass are a wide variety of rock shapes, sizes, textures, rounded and angular, and many with varying consistencies. As I said, I have seen what appeared to be plain basalt and vesicular basalt, others with no crystals, and some with small white phenocrysts of maybe 1 to less than 5 per cent. And we are in a boulder field where the boulders range up to 2 feet, with a few larger than that. Some of the boulders are lying on top of the surface, some are partially exposed and some are just barely exposed. In our traverse around on the surface, and particularly working with the scoop, we ran into boulders below the surface – probably buried under several inches of the ground mass. I suspect this boulder field may have some of its origin with this large sharp-edged rocky-rim crater that we passed over in the final descent. Yesterday I said that was about the size of a football field. I have to admit it was a little hard to measure, coming in, but I thought it might just fit into the Astrodome as we came by it. The rocks in the vicinity of this rocky-rim crater are much larger than those in this area. Some are 10 feet or so and perhaps bigger, and they are very thickly populated out to about one crater diameter beyond the crater rim. Beyond that, there is some diminishing. Even out in this area the blocks seem to run in rows with irregular patterns, and then there are paths between them with considerably less surface evidence of hard rocks.’’

“Thank you, very much,’’ acknowledged Evans.

As they ran through the checklist for liftoff, Aldrin used his pen to push in the damaged circuit breaker.

“For your information,” Evans reported, “the circuitry looks real fine on that ascent engine arm circuit breaker.’’ With this confirmed, Armstrong set the switch on the Engine Selector to Ascent.1

Glynn Lunney polled his Black Team on Eagle’s status, and Evans relayed the result, “Eagle’s looking real fine to us.’’

When Columbia appeared on revolution 25, Evans called Collins with another estimate for the position of the landing site, this time the one determined by Gene Shoemaker’s team of geologists, but as there was less than half an hour remaining to liftoff Collins was too busy to look.

“Our guidance recommendation is PGNS,’’ Evans advised Eagle, “and you’re cleared for takeoff.’’

“Roger. Understand,’’ replied Aldrin. “We’re number one on the runway.’’

Armstrong and Aldrin once again harnessed themselves to the floor to enable them to ‘stand’ upright while in flight.

The ascent propulsion system (APS) of Eagle was built by Bell Aerosystems, using

The options were, in turn, Descent, Off and Ascent.

an injector plate that was supplied by the Rocketdyne division of North American Rockwell. In all, the engine stood 4 feet 6 inches tall. Its combustion chamber was actually located inside the cabin, within a cylindrical cover that rose up from the floor, and its short nozzle sat on top of the central part of the descent stage. The only moving parts were the ball valves to allow propellants to flow to the injector. For redundancy, the primary valve was supplemented by a backup with a bypass line. It was required only that the valves open, since the hypergolic propellants would ignite on coming into contact in the chamber. If the computer command did not reach the valves, the circuit could be bypassed. Armstrong had suggested adding an option for manually operating the valves, but there had been no time. And, of course, the engine would require to burn long enough to enable the spacecraft to achieve some kind of orbit. If liftoff were delayed, Eagle would have to adopt a lower orbit in order to catch up with Columbia more rapidly, but if liftoff were to be so delayed that this would be impracticable, it was to climb to a high altitude and go passive, while Collins lowered Columbia in order to complete an ‘extra’ orbit to get into position to chase Eagle. There were many variations on this theme, depending on the circumstances, and Collins had a book detailing the procedures for each – all of which had been rehearsed in simulations. However, because Collins was allowed to descend to no lower than 50,000 feet, all of his options presumed that Eagle managed to attain at least this altitude. In a simulation in mid-June, the APS had shut down during ascent and Eagle had made up the velocity shortfall using a lengthy firing of all four of its downward-facing 100-pound-thrust RCS thrusters which, although nominally independent of the primary propulsion system, in an emergency could be fed from the main tanks to produce a sustained burn. On the possibility of the APS not igniting, Armstrong pointed out before the mission, ‘‘When pilots really get worried, is when they run out of options and run out of time simultaneously.’’ If it failed to fire, there were various procedures to try. Although Columbia would be able to remain in orbit for two more days before it had to set off for home, the issue would by then have been resolved, as Eagle’s power and oxygen would last no longer than 24 hours. Collins would later admit that his ‘‘secret terror’’ was that he would have to leave his colleagues on the Moon. As he told a reporter, ‘‘They know, and I know, and Mission Control knows, that there are certain categories of malfunction where I just simply light my engine and come home without them.’’

The White House had prepared a speech for President Nixon in case this were to occur: ‘‘Fate has ordained that the men who went to the Moon to explore in peace will stay on the Moon in peace. These brave men, Neil Armstrong and Edwin Aldrin, know that there is no hope for their recovery. But they also know that there is hope for mankind in their sacrifice. These two men are laying down their lives in mankind’s most noble goal: the search for truth and understanding. They will be mourned by their families and friends; they will be mourned by their nation; they will be mourned by the people of the world; they will be mourned by a Mother Earth that dared send two of her sons into the unknown. In their exploration, they stirred the people of the world to feel as one; in their sacrifice, they bind more tightly the brotherhood of man. In ancient days, men looked at stars and saw their heroes in the constellations. In modern times, we do much the same, but our heroes are epic men
of flesh and blood. Others will follow, and surely find their way home. Man’s search will not be denied. But these men were the first, and they will remain the foremost in our hearts. For every human being who looks up at the Moon in the nights to come will know that there is some corner of another world that is forever mankind.’’ Prior to making this speech, the President was to have telephoned the wives of Eagle’s crew. When it was evident that communications were nearing their conclusion, a clergyman was to have commended their souls in the manner of a burial at sea. Although macabre, it was only right and proper that such plans should be drawn up.

As the final minute ticked away, Armstrong issued a final reminder, “At five seconds to go I’m going to get Abort Stage and Engine Arm, and you’re going to hit Proceed.’’

“Right,” confirmed Aldrin.

“And that’s all,’’ Armstrong added wryly.

There was a ‘thud’ as pyrotechnics cut the structural and electrical connections between the two stages, and then the engine lit.

‘‘We’re off!’’ Armstrong announced.2

The television camera drew its power from the descent stage, but after the moonwalk Aldrin had pulled the circuit breaker to end its transmission through the high-gain antenna on the ascent stage. If they had erected the large self-standing antenna on the surface, it would have been possible to televise the liftoff. As they departed, Aldrin started the 16-millimetre Maurer camera that was mounted in his window in order to document their ascent to orbit.

It was just before 1 pm in Houston. Joan Aldrin was on the floor in front of the television. When Gerry Carr said Eagle had lifted off, she rolled onto her back and kicked her legs in the air (as she was wont to do), then stood up and leaned against the wall. ‘‘It’s strange,’’ she said, ‘‘from the beginning I have worried more about liftoff than touchdown.’’ This was perhaps because she had confidence in the astronauts’ ability to fly the vehicle, but at liftoff they were at the mercy of the hardware. ‘‘They’re on their way home!’’

After a prayer, Herman Clark, the Grumman quality control inspector who had checked out the APS of LM-5, had held his breath literally as well as figuratively as he waited for news; on hearing that the engine had lit he told himself, ‘‘Job well done, QC-wise’’, then resumed work checking another LM on the production line.

The APS plume shredded the foil that had covered the descent stage, sending fragments radially outwards. ‘‘Look at that stuff go all over the place,’’ exclaimed Armstrong. The plume did not stir up any dust, but Aldrin saw it blow the flag to the ground. The engine delivered just 3,500 pounds of thrust, but the ascent stage was light and it climbed rapidly, imposing a load of about 0.5 g. As it ascended, Aldrin remarked on its shadow, which raced over the surface. After 10 seconds of vertical rise, Eagle pitched over 45 degrees in order to begin to build a horizontal component to its velocity.

‘‘One minute and you’re looking good,’’ Evans advised.

Eagle had been on the surface for 21 hours 36 minutes.

The LM normally controlled its pitch and roll by using opposed upward – and downward-aimed thrusters to rotate the vehicle. However, as the upward-aimed thrusters would reduce the effect of the APS, it had been decided that during the ascent only the downward-aimed thrusters would be used, and firing the fore and aft thrusters in pairs to implement the progressive pitch-over produced a pronounced oscillation. “It’s a very quiet ride,” Aldrin noted. “There’s just a little bit of slow wallowing back and forth; not very much thruster activity.’’

“You’re looking good at 2 minutes,’’ Evans continued. “PGNS, AGS, and the MSFN all agree.’’

“We’re within 1 foot per second, AGS to PGNS,’’ Aldrin pointed out. If the PGNS navigation were to falter, the AGS would take over.

“Go at 3 minutes. Everything’s looking good,’’ called Evans.

“We’re going right down US One,’’ Armstrong pointed out. US Highway One was the main north-south route running between New York and Florida, and the astronauts had borrowed the name for a distinctive linear valley that astronomers knew as Hypatia Rille.

“We’ve got Sabine off to our right,’’ Aldrin announced. And a moment later, “There’s Ritter.’’ These were two large craters just beyond the western shore of the Sea of Tranquility. “And there’s Schmidt. Man, that’s impressive looking, isn’t it?’’ During their earlier orbital sightseeing, these craters had been in darkness.

The APS burned for the planned 7 minutes and inserted the spacecraft into orbit 166 nautical miles west of Tranquility Base. Its progress towards and across the terminator into darkness was monitored by the Madrid station of the Manned Space Flight Network. This showed a perilune of 9.4 nautical miles, an apolune of 46.7 nautical miles and a velocity of about 5,537 feet per second. The PGNS gave 9.5 by 47.3, and the AGS gave 9.5 by 46.6 – indicating that, all things considered, the redundant systems were in excellent agreement. Such a low orbit would readily be perturbed by the mascons, but this did not matter because the initial perilune would be raised during the rendezvous. The ascent had halved the 10,837-pound mass of the ascent stage, reducing it to 5,885 pounds.

Meanwhile, at home

Jan Armstrong listened to the ascent on her squawk box alone, while having a late breakfast. When she heard her husband call shutdown right on time she knew that, with Eagle in orbit, if it were to encounter any difficulties Columbia would be able to rescue it.

Back in space

In weightlessness, Armstrong and Aldrin expected the specks of dust which had settled on the floor of the cabin to float around and pose a health hazard, but most of it remained in place, seemingly because it had developed an electrostatic charge and become ‘clingy’. Free of the risk of inhalation or eye contamination, they were safely able to remove their helmets. The first in-orbit task was to do a P52 to check the inertial platform prior to initiating the rendezvous.

Columbia was oriented to point its radar transponder towards Eagle. Its VHF – ranging apparatus acquired Eagle at a range of 250 nautical miles, but the lock was intermittent. However, when Collins spotted the flashing beacon in the darkness he centred the cross hair of his sextant on it and instructed the computer to note the sighting. Eagle was to be the active partner in the rendezvous but if at any time it was unable to make a manoeuvre, Collins was ready to perform the ‘mirror image’ manoeuvre approximately one minute later, and take over the active role. The first rendezvous manoeuvre was calculated by Houston. The apolune of the initial orbit was on the far side. On nearing apolune, Eagle was to use its RCS thrusters to add 51.5 feet per second to lift the perilune. This coelliptic sequence initiation (CSI) manoeuvre gave an orbit of 46.1 by 49.5 nautical miles. On emerging from behind the Moon on revolution 26, the separation between the vehicles was 100 nautical miles and, since Eagle was lower and travelling faster, this was reducing at 99 feet per second. As a result of the perturbations by the mascons, Columbia’s orbit was 56.8 by 63.2 nautical miles. About one hour after CSI, the constant differential height (CDH) manoeuvre was a radial burn of 45 seconds for a delta-V of 9.2 feet per second to make the orbit coelliptical with and ideally 15 nautical miles below the orbit of Columbia. As Eagle caught up, Columbia ‘rose’ progressively above the horizon. About 40 minutes after CDH, with the separation at 38 nautical miles, the elevation reached 27 degrees and Eagle made the terminal phase initiation (TPI) manoeuvre, a 25-foot-per-second burn designed to set up an interception. Eagle had been tracking Columbia by radar, but now Armstrong was to track it visually and make lateral adjustments in order to hold his target ‘fixed’ against the stars, thereby ensuring that although the vehicles were tracing different arcs around the Moon, he made a straight-line (i. e. inertial) approach to Columbia. Shortly after the burn, Eagle passed ‘over the hill’. If things went to plan, by AOS on revolution 27 it would be station-keeping alongside Columbia.

The terminal phase finalisation (TPF) manoeuvre involved a series of small burns to refine the line of approach and, when the range was down to a few thousand feet, to brake in order to come to a halt within 100 feet of Columbia. It was a procedure perfected by the Gemini missions. The timing had been set to enable the terminal phase to occur in darkness, with Armstrong visually observing the flashing beacon on Columbia against the stars. The braking phase would occur just after emerging from the Moon’s shadow, to enable him to see and manoeuvre towards his target. This is the reason that this part of the mission, like so many other critical events, had to occur out of communication on the far side of the Moon.

Thus far, Columbia had been oriented to face its lower equipment bay towards the approaching spacecraft to enable Collins to use the sextant, but now he turned to point his apex towards the newcomer, and watched it from the left couch using the optical reticle in window 2, with the 16-millimetre Maurer camera in window 4 to document the remainder of the approach. He was delighted to see that Eagle remained centred in his reticle. Early in mission planning, Aldrin had noted that if the ascent stage was oriented ‘upside down’ as it finished the approach, this would obviate solar glare. As Eagle drew to a halt about 50 feet from Columbia, Collins took a series of Hasselblad photographs to document the state of the ascent stage.

During the terminal phase, Eagle had drawn ahead of Columbia, and therefore as the vehicles jointly flew around the limb he was able to snap his companion with Earth on the lunar horizon.

“Eagle and Columbia, Houston. Standing by,” Evans called to announce that communications had been restored.

“We’re station-keeping,” Armstrong replied, prompting sustained applause in the Mission Operations Control Room.