Preparing Eagle

After breakfast Aldrin went into the lower equipment bay, removed his constant-wear garment, reinstalled his urine-collection and fecal-containment utilities and put on his liquid-cooled garment, the fishnet fabric of which had a network of narrow flexible plastic tubes sewn into it through which cold water would be pumped to manage the heat generated by the exertion of the moonwalk. It had to be donned now, since they were to remain suited while in the LM. Aldrin then went into the LM, vacating the lower equipment bay to Armstrong, who suited up with Collins assisting with the zippers and checking fixtures - a process that took 30 minutes. When Armstrong went into the LM, Aldrin returned to suit up. Collins also suited up as a precaution against inadvertent decompression during undocking, or the need for an early abort in which Eagle's crew would conduct an external transfer using the side hatch.4

At AOS on revolution 11, Aldrin was well into powering up Eagle's systems. When Duke requested a status report, it became evident that Aldrin was running about 30 minutes ahead of the flight plan. When the steerable high-gain antenna mounted on a boom on the right-hand side of the roof was pointed to Earth, the LM flight controllers received their first significant telemetry of the mission.

The two crews worked independently in their preparations, but certain events required coordination. One item was setting Eagle's clock, which was to be done by synchronising it with its counterpart in Columbia.

Collins counted down, ''15 seconds to go. 10, 5, 4, 3, 2, 1. MARK.''

''Got it,'' confirmed Armstrong.

Another task, some time later, was to coarsely align the platform of Eagle's

4 Only once Eagle was safely on the surface would Collins remove his suit, and he would don it again shortly prior to liftoff.

inertial navigation system. In essence, two humans acted as an interface between two machines.

''I'm ready to start on a docked IMU coarse-align,'' Armstrong said. ''When you're ready, go to Attitude Hold with Minimum Deadband.'' Once Collins had confirmed that he was holding the docked vehicles steady, Armstrong said, ''I need your Noun 20.''

''I've got Verb 06, Noun 20. Give me a Mark on it,'' Collins replied. ''MARK!'' called Armstrong. ''Register 1, plus 11202, plus 20741, plus 00211,'' said Collins, reading the display on his DSKY. The numbers represented the CSM's attitude with respect to the current REFSMMAT.

Armstrong gave a read-back for confirmation, ''11202, 20741, 00211.'' ''That's correct,'' Collins agreed. After performing an arithmetical transformation to allow for the fact that the designers of the vehicles had specified their Cartesian axes differently, Armstrong keyed the attitude into his DSKY.

The alignment showed up in the telemetry, and Duke reported, ''That coarse align looks good to us.''

''Okay, Mike,'' said Armstrong. ''Your Attitude Hold is no longer required.''

If necessary, Eagle would later make star sightings for its equivalent of a P52 to refine the alignment.

Once he had installed the probe and drogue assemblies in the tunnel and fully extended the probe, Collins called to Eagle, ''The capture latches are engaged in the drogue. Would you like to check them from your side?''

''Stand by,'' Armstrong replied. He looked up through the open hatch to verify that the tip of the probe projected through the hole in the centre of the drogue and the three small latches, each no larger than a finger nail, were engaged. ''Mike, the capture latches look good.'' Armstrong then closed the upper hatch to make Eagle air-tight.

At this point, Apollo 11 passed around the far side of the Moon. They were to continue with the preparations during revolution 12, and undock prior to AOS on revolution 13.

Collins slowly retracted the probe until the latches established a firm grip of the drogue. The next task was to release the main latches in the docking units. To guard against the possibility of depressurisation, he donned his helmet and gloves.

The Liquid Cooled Garment to be worn inside the Extravehicular Mobility Unit.

Five minutes later, Aldrin called, ''Mike, let us know how you're coming up there, now and then.''

''I'm doing just fine,'' Collins replied. He was physically priming the latches, imparting the stored energy they would need to re-engage on the redocking. ''I've cocked eight latches, and everything is going nominally.'' And then a minute later, ''All 12 docking latches are cocked.''

''Okay,'' acknowledged Aldrin.

''I'm ready to button up the hatch,'' Collins announced.

Although the vehicles were now held together only by the capture latches, these were able to maintain the hermetic seal in the tunnel because the interface had been compressed by the hard docking. ''Mike, have you got to the Tunnel Vent step yet?'' Aldrin asked.

''I'm just coming to that,'' replied Collins. ''What can I do for you?''

''Well, we're waiting on you,'' Aldrin noted. Although ahead of schedule, the LM crew had to wait for Collins to vent the tunnel before they could proceed.

Two minutes later, Collins reported, ''I'm ready to go to LM Tunnel Vent.'' He opened the valve to space. The process was expected to take about 8 minutes.

''How're you doing, Mike?'' Armstrong asked several minutes after that time had elapsed.

''Stand by, and I'll give you the delta-P reading,'' replied Collins. He reset the valve to enable a nearby gauge to measure the difference in pressure between the tunnel and the command module, which was at about 5 psi. ''It's 3.0 psi.'' There was still a significant amount of air remaining in the tunnel.

In Eagle, Armstrong and Aldrin donned their helmets and gloves to check the hermetic integrity of their suits.

Meanwhile, Collins started to manoeuvre into the attitude required for the next P22 landmark tracking, which would be Site 130-prime, a crater inside Crater 130 in the Foaming Sea. Because this had been selected as a reference by John Young on Apollo 10 for the reason that it was both readily identified and small enough to be accurately marked using the sextant, it was also referred to as John Young's crater. The sightings were to be used to update Houston's knowledge of the orbit, and where the spacecraft was in that orbit, in order to calculate the precise time at which to initiate Eagle's powered descent.

When the manoeuvre was finished, Armstrong called Collins, ''We're going to put our gear down.''

''Master Arm,'' said Aldrin on intercom, reading the checklist. ''Landing Gear Deploy, Fire.''

''Here we go, Mike,'' Armstrong warned before detonating the pyrotechnics to release the spring-loaded legs.

''Bam, it's out. There ain't no doubt about that,'' Aldrin mused. ''Master Arm, Off.''

''The gear went down okay, Mike,'' Armstrong called. There were redundant circuits, but the primary had successfully fired the pyrotechnics to deploy the legs. The 67-inch-long probes, whose tips had been latched against the inner parts of the legs, hinged on the undersides of the lateral and rear foot pads to project 'straight down'. For Apollo 5 in February 1968, a Saturn IB had launched LM-1 absent its legs for an unmanned test. LM-3 had demonstrated the deployment of the legs on Apollo 9 in March 1969. At that time the design had included a probe on each of the pads but, at Armstrong's request, it had been decided to delete the probe from the forward leg lest it be bent on touchdown in such a manner as to cause him to slip (or worse, puncture his suit) as he jumped backwards down off the ladder.

As Apollo 11 appeared around the trailing limb on revolution 12, Duke made them aware that communications had been restored. ''Apollo 11, Houston. We're standing by.'' There was a lot of static on the downlinks. With no response, in all likelihood owing to the fact that he had not directed his call to a specific vehicle, Duke persisted. ''Columbia, Houston. Do you read?''

''Loud and clear,'' Collins acknowledged.

''Eagle, do you read Columbia?'' asked Collins.

''Yes,'' acknowledged Aldrin. ''I'm working on the high-gain right now.'' He slewed the steerable dish as per the flight plan, but could not establish contact with Earth. ''Are you in the right attitude, Mike?''

''Columbia, Houston,'' called Duke.

''Houston, Columbia. You're loud and clear.''

''Eagle, Houston. Will you verify you are on the forward omni?'' No response. ''Columbia, Houston. We have no voice with Eagle. Would you please verify that Eagle is on the forward omni.''

''Buzz,'' Collins called. ''Are you on the forward omni?'' When there was no response, he repeated the call.

''Houston, Columbia. Eagle is on the forward omni.''

Duke tried again, ''Eagle, Houston.''

''Roger, I've got you now,'' acknowledged Aldrin. ''I fed in those angles for the S-Band, and couldn't get a lock-on. It appears as though the antenna would have to be looking through the LM in order to reach the Earth.''

Because the docked vehicles were oriented to facilitate P22 landmark tracking shortly after flying around the limb, it was difficult for the boom-mounted S-Band antenna cluster on Columbia to point at Earth, and the body of the LM blocked the line of sight of its steerable dish. In this attitude the vehicles would have to rely on their respective omnidirectional antennas.

''Eagle, Houston. Could you give us an idea where you are in the activation?''

''We're just sitting around waiting for something to do,'' Aldrin replied. ''We need a state vector and a REFSMMAT before we can proceed to the AGS calibration, and we need you to watch our digital autopilot data load, the gimbal drive check and the throttle test.''

Although Armstrong and Aldrin were well ahead in their LM activation, they were again obliged to wait until Houston was able to upload information and monitor their telemetry, which could not be done until they could use their high-gain antenna, which in turn meant waiting until Collins had performed his landmark tracking. While getting ahead created a margin against encountering a problem that might slip them behind schedule, the need to do certain tasks at given times meant that being ahead early on did not in itself enable the process to be completed ahead of the flight plan.

''It'll be about another 10 minutes or so before we get the P22 and manoeuvre to an attitude for the high-gain,'' Duke pointed out.

Armstrong and Aldrin proceeded with those items that could be done using the low data-rate provided by an omnidirectional antenna. ''We're ready to pressurise the RCS,'' Aldrin announced.

''You can go ahead with RCS pressurisation,'' Duke agreed, ''but we'd like to hold off on the RCS hot-fire checks until we get the high bit-rate.''

''Eagle, Columbia. My P22 is complete,'' Collins reported. He manoeuvred to let the high-gain antennas on both of the vehicles see Earth, and communications markedly improved. With high data-rates on both its uplink and downlink, Eagle was able to complete data uploading and checkout.

''Houston, Eagle,'' Aldrin called. ''Both RCS helium pressures are 2,900 psi.'' ''Let me know when you come to your RCS hot-fire checks,'' said Collins, ''so I can disable my roll thrusters.''

Fifteen seconds later, Aldrin announced that they were ready. ''Columbia,'' he called, ''We'd like Attitude Hold with Wide Deadband.''

''You got it,'' Collins replied. A wide deadband on the Attitude Hold would allow the testing of Eagle's thrusters to disturb the attitude of the docked vehicles without prompting Columbia's control system to waste propellant in attempting to intervene. ''My roll is disabled. Give me a call as soon as your hot-fire is complete, please.''

''Houston, Eagle,'' Aldrin called several minutes later. ''The RCS hot-fire test is complete. How did you observe it?''

''It looked super to us,'' Duke confirmed.

''I've got my roll jets back on now,'' Collins announced.

At this point, Kranz polled his flight controllers, and Duke relayed the result, ''Apollo 11 Houston. You're Go for undocking.'' ''Understand,'' replied Aldrin.

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