Translunar coast

RETRIEVING EAGLE

Immediately after the TLI manoeuvre, the S-IVB adopted an orientation calculated to yield favourable illumination for the separation of the CSM and its subsequent transposition, docking and extraction (TD&E) of the LM. Armstrong yielded the left-hand couch to Collins who, as CMP, had trained for this delicate operation. The reaction control system (RCS) comprised four units at 90-degree intervals on the side of the service module, each with a cluster of four rocket thrusters that could be fired separately or in various combinations to control roll, pitch and yaw motions. During the climb through the atmosphere, the conical adapter mounted on top the S-IVB was allowed to vent to ensure that there would be no sudden release of air when the spacecraft separated.

“You’re Go for separation,” called Bruce McCandless, 3 hours 15 minutes into the mission.

After using the left-hand translational controller to start the aft-facing thrusters, Collins threw a switch to detonate pyrotechnic charges around the rear rim of the service module to detach that module from the adapter. Once a display indicated that he was moving at about 1 foot per second, he ceased to thrust. Meanwhile, the four panels of the adapter hinged open like petals and then detached to drift away. After 15 seconds, he used the right-hand rotational controller to initiate a 2-degree-per-second pitch motion. When so instructed, the digital autopilot was to maintain this angular rate but, to his frustration, it cancelled the rotation and adopted a fixed attitude. He had to repeat the procedure several times before the autopilot accepted the rotation. In consequence, the rotation used rather more propellant than planned. The issue was later determined to be procedural in nature. Once the spacecraft was facing the S-IVB, Collins terminated the rotation and fired the aft-facing thrusters again, this time to halt 100 feet out, whereupon he fired them a third time in order to move back in.

“I hope you’re getting some pictures, Buzz,’’ Armstrong said.

“I’ve got the 16-millimetre going at 16 frames per second,’’ confirmed Aldrin, referring to the Maurer camera he had mounted in window 4. The LM was clearly visible, supported within the annular ring near the base of the adapter by fixtures on its folded legs.

“Be sure that your RCS is working,” Armstrong prompted Collins, to confirm that the forward-facing thrusters to be used for braking were functional, because if they failed the CSM would smash into the LM. When Collins did so, he noted that the efflux rippled the aluminium thermal shielding of the ascent stage, and hoped he wouldn’t damage it.

The extended probe on the apex of the spacecraft was not visible through the small forward-facing window, but Collins did not need to see it as there was a ‘stand off target on the roof of the LM which, when correctly viewed, meant that the probe was centred on the conical drogue. With the Sun over his shoulder, the roof of the LM was nicely illuminated. In easing the probe into the drogue, Collins was conscious that his vehicle had a mass of 65,000 pounds, and that the 33,000-pound LM was attached to the ‘dead weight’ of the spent S-IVB. As the probe penetrated the socket at the apex of the cone, three small capture latches around the tip of the probe automatically engaged for a ‘soft docking’. When he was sure that the vehicles were lined up, Collins threw a switch and a discharge of nitrogen gas pneumatically retracted the probe, in the process drawing the two collars together and triggering 12 spring-loaded latches that established a rigid connection, or ‘hard docking’.

Although the docking was accomplished, Collins was dissatisfied. ‘‘That wasn’t the smoothest docking I’ve ever done.’’

‘‘Well, it felt good from here,’’ Armstrong complimented.

‘‘I mean the gas consumption,” explained Collins. He had used rather more fuel during the transposition manoeuvre than expected.[19]

While manoeuvring, the quality of signal using the omnidirectional antennas had degraded to the point at which communication became impractical. Aldrin operated the controls to slew the high-gain antenna mounted on a boom on the rear of the service module to point its beam towards Earth to restore communications; once locked on, the system would steer itself to maintain maximum signal strength as the line of sight evolved.

The 30-inch-diameter tunnel to the LM ran through the apex of the command module. As per the plan, an open valve in the LM’s overhead hatch had allowed its cabin to vent. Having already raised the pressure in the command module, Collins opened a valve to allow oxygen to pressurise the tunnel, and thence the LM. On opening his hatch, he noted an odour reminiscent of charred electrical insulation, but all the exposed wiring in the tunnel appeared to be factory fresh and he pressed on with his checklist, jiggling each of the docking latches by hand to confirm that it was properly engaged.

In 1958 America’s first satellite, Explorer 1, discovered that there is an intense belt of charged-particle radiation present within the Earth’s magnetic field. In fact, as subsequent satellites revealed, there is an inner belt of high-energy protons and an outer belt of electrons. These ‘radiation belts’ were named after the scientist who

A depiction of the inner and outer van Allen radiation belts.

supplied the instrument that made the initial discovery – James van Allen of Iowa University. The proton belt would pose a severe health risk to any astronaut unwise enough to linger within it, but fortunately it was concentrated above the equatorial zone and extended out only a few thousand miles, and because the Moon orbits Earth at an angle to the equator Apollo 11 was able to avoid the most intense part of this belt. Also, as with any object that is thrown upwards in Earth’s gravity, as soon as the S-IVB shut down its engine it began to slow as it pursued a ballistic trajectory. At that time it was at an altitude of 177 nautical miles and was climbing at 21,345 nautical miles per hour. When Collins separated the CSM from the S-IVB, their altitude was over 3,000 nautical miles, and this distance had doubled by the time he completed the transposition and docking 10 minutes later. The radiation received was therefore no worse than that involved in having a chest X-ray. The radiation within the Earth’s magnetic field originates from the ‘solar wind’, which is a flow of charged particles emanating from the Sun. This was discovered in 1962 by Mariner 2, the first spacecraft to report on conditions beyond the realm dominated by the Earth’s magnetic field. Cislunar space – the environment between Earth and the Moon – is comparatively benign, unless a ‘solar flare’ directs a blast of charged-particle radiation in our direction. In terms of sun spots, the intensity of solar activity varies with an 11-year periodicity and, in fact, 1969 was a risky time to be heading for the Moon!

Looking back at Earth, which was rapidly shrinking, Armstrong displayed his keen sense of geography – a childhood passion. Their departure trajectory offered a better view of the northern hemisphere than of southern latitudes. ‘‘Houston,’’ he called, ‘‘you might be interested that out of my left-hand window right now, I can observe the entire continent of North America, Alaska and over the pole, down to the Yucatan peninsula, Cuba, the northern part of South America – and then I run out of window.’’

The number of sunspots follows a roughly 11-year cycle.

Meanwhile, Collins had inserted electrical plugs to feed power through to the LM’s heaters and to pyrotechnics in the adapter. McCandless gave them the go – ahead to retrieve the LM. Precisely one hour after initiating the transposition and docking sequence, and now 12,600 nautical miles from Earth, Collins fired the charges to release the LM, and springs eased the 98,000-pound docked spacecraft away from the spent stage. If the charges had failed, the CSM would have undocked and gone on to fly an Apollo-8-style mission in lunar orbit, but this would have been a poor consolation.

The next task, some 20 minutes later, was to perform a manoeuvre to increase the rate of separation from the spent S-IVB. The cutoff velocity at TLI had been set marginally faster than that of the ideal trajectory, with the intention of using the service propulsion system (SPS) of the CSM to cancel the excess. This engine had been designed in such a manner that it was unlikely not to fire, but it was wise to test it early on. Delivering 20,500 pounds of thrust, it would be able to impart the desired velocity change (delta-V) of 19.7 feet per second in 3 seconds, which was just long enough for the telemetry to verify the propellant supply, the combustion chamber pressure and the stability of the gimbal. There was no need for an igniter because the hydrazine-based fuel and nitrogen tetroxide, being hypergolic, ignited immediately on coming into contact after being fed through a pattern of holes in the injector into the combustion chamber.

After running through the post-burn checklist, Armstrong returned to the view of Earth. “We didn’t have much time to talk about the view out the window when we were preparing for LM ejection, but up to that time we had the entire northern part of the day hemisphere visible – including North America, the North Atlantic, and Europe and the northern region of Africa. There was a cyclonic depression over northern Canada, east of Athabasca. Greenland was clear, and it appeared that we were seeing just the icecap. All of the North Atlantic was pretty good. And Europe and northern Africa seemed to be clear. Most of the United States was clear. There was a low, it looked like a front, stretching from the centre of the country, up north of the Great Lakes and on into Newfoundland.’’

“I didn’t know what I was looking at,’’ added Collins, “but I sure did like it!’’

“The view must be pretty good from up there,’’ McCandless agreed. “We show you about 19,000 nautical miles out now.’’ Although this was the altitude at which satellites in geostationary orbits reside, Apollo 11 was far above the plane in which such satellites operate.

If the S-IVB were to pursue the trajectory established by TLI, then it, like the spacecraft, would pass just in front of the leading limb of the Moon. To eliminate any possibility of a collision in transit, once Apollo 11 was clear of it, the ground commanded the S-IVB to execute a venting process designed to deflect its path to pass close by the trailing limb for a gravitational ‘sling shot’ into solar orbit. This venting would involve several phases over the period of about 40 minutes, and the planners had worked out how the spacecraft should be oriented to enable the crew to observe it.

‘‘We’ve completed our manoeuvre to observe-the-slingshot attitude,’’ Collins reported, ‘‘but we don’t see anything – no Earth, and no S-IVB.’’ Houston provided a revised attitude, and Collins started the manoeuvre, but because he had not only used more propellant than expected during the transposition and docking, but had also undertaken a fruitless manoeuvre, he initiated this new manoeuvre at a slow rate.

The venting could not be postponed because, once commanded, the Instrument Unit could not be interrupted. ‘‘It doesn’t look to us like you will be able to make it around to the observation attitude in time,’’ McCandless warned. ‘‘We recommend that you save the fuel.’’

‘‘Our manoeuvre has already begun,’’ pointed out Collins, ‘‘so it’s going to cost us about the same amount of fuel to stop it no matter where we stop it, and we may as well keep going.’’

‘‘We’ve got the S-IVB in sight at what I would estimate to be a couple of miles away,’’ announced Aldrin several minutes later. ‘‘The dump appears to be coming out at radially opposite directions.’’ As this preliminary part of the sequence was to be non-propulsive, the stage was venting oxidiser from opposite sides at the rear. About 25 minutes later, the venting was switched to occur through the J-2 engine, but by then the S-IVB was no longer visible. Finally, the two auxiliary propulsion system modules on the rear of the stage were fired to complete the manoeuvre.

As McCandless read up instructions to reconfigure the fuel cells that generated electrical power, the astronauts started their first meal. ‘‘If we’re late in answering you,’’ Collins apologised, ‘‘it’s because we’re munching sandwiches.’’

‘‘I wish I could do the same here,’’ said McCandless.

‘‘No. Don’t leave the console!’’ Collins warned. ‘‘Flight doesn’t like it. How is he today?’’ The flight director was Clifford Charlesworth, and Collins had served as his CapCom during the Apollo 8 mission.

‘‘Oh, he’s doing quite well,’’ McCandless laughed.

‘‘I think today is the birthday of California,’’ Armstrong called. ‘‘I believe they are 200 years old, and we send them a happy birthday. I think it is also Dr George Mueller’s birthday, but I don’t think he’s that old!’’ George E. Mueller, Director of the Office of Manned Space Flight, was celebrating his 51st birthday.

Six hours into the mission, Charlesworth’s Green Team handed over to Gene Kranz’s White Team, and Charlie Duke took over as CapCom. After crossing the road to brief the press in the News Center, Charlesworth joined his controllers in the ‘Singing Wheel’, a red-painted wooden barn of a building that housed the bar that served as a ‘watering hole’ for off-shift flight controllers heading home.

Having taken sextant sightings to realign the inertial platform, Collins initiated a deep-space navigation test. This P23 exercise required him to measure the angles of five stars relative to Earth’s horizon. In each case, the computer was to orient the vehicle to enable the sextant to measure from the ‘substellar point’. However, the system was not aligning properly, and a measurement along a line that was not perpendicular to the horizon would yield an inaccurate result. The technique was valid, it was simply that something had gone amiss in planning. But he persevered because the data would help the engineers to determine the problem. The test was scheduled at this time in order to confirm the ability to make such measurements before the spacecraft was so far away that Houston could not provide a check. This technique was intended primarily for navigating the approach to re-entry, in order to provide a contingency against loss of communications on the way home.

Meanwhile, first Aldrin and then Armstrong doffed their pressure suits. It was a dynamic process involving a colleague unzipping the rear of one man’s suit and holding him stable while he squeezed out. After finishing his navigation exercise, Collins joined them. With the various parts of the three suits adrift, there was, as Aldrin later put it, ‘‘a great deal of confusion, with parts and pieces floating about the cabin as we tried to keep the logistics under control’’. The suits were carefully folded, stuffed into storage bags and stowed beneath a couch. It was a great relief to remove the urine-collection and fecal-containment devices, which were stowed in a locker in the lower equipment bay. There was no toilet. Urination would be through a tube into a plastic bag that would be periodically vented overboard into vacuum. Defecation would involve the use of a plastic bag, part of which fitted over the hand like a glove. When finished, a germicide pill would be inserted into the bag to prevent bacteria generating gas. This ‘glove bag’ had proved effective on Gemini flights, when, because of the pill, it was euphemistically referred to as a ‘blue bag’. Used bags were stowed in a special container in the lower equipment bay. It typically took 45 minutes to defecate. The use of the bags did not obviate the associated odours, however.[20] Over their constant-wear garments the men wore two-piece teflon-fabric flight suits. With the crew in ‘shirt sleeves’ and the centre couch removed, the cabin appeared considerably larger. The decor was ‘battleship grey’. At an early stage a psychologist had recommended that, in order not to cause disorientation, there ought to be a two-colour scheme with brown below a certain horizontal level and blue above it, which sounded very reasonable until it was pointed out that in weightlessness there was no unique sense of ‘up’, and, by the psychologist’s own logic, if the colour scheme really did matter, then an inappropriate one would be upsetting! Aldrin, who had mastered weightlessness spacewalking on Gemini 12, found the freedom of movement in the command module enjoyable because, as he put it, he was spacewalking indoors! Fortunately, due to the care taken during their first few hours in space, none of the Apollo 11 crew developed any symptoms of ‘space sickness’.