Down in the dust

When President Kennedy gave the United States his lunar challenge, he never stipulated that the crew should go outside. Land on the Moon and return safely to Earth; that was the challenge. Yet it was simply assumed from the outset that extra vehicular activity (EVA) on the surface would be part of the show. Right or wrong, a walk on the Moon would be the climax of the mission. And in the minds of most people, the Apollo 11 moonwalk would climax the entire program.

POSTLANDING

Once on the Moon, it took a while for the LM’s two-man crew to transition from the role of pilots to that of explorers. Their ship was still fully powered and configured for flight. It was particularly important that the crew and mission control be ready for lift-off in case some problem with the spacecraft was identified.

Apollo 11, again riding its luck as the first landing, came astonishingly close to invoking this scenario. As soon as the landing had been achieved and the engine shut down, the flow of fuel through the heat exchanger also stopped. This heat exchanger had been using the warmth in the fuel to heat the extremely cold helium being used to pressurise the propellant tanks. The contents of the supercritical helium tank were then vented, which unintentionally froze a slug of fuel in the fuel line. Engine heat warmed the rest of the line and caused its internal pressure to rise beyond the limit of the sensor. Flight controllers and managers began to confer, working towards a decision to lift-off, or at least to burp the engine before the line could burst and spray hydrazine onto hot components. As they deliberated, the heat eventually worked its way to the frozen slug and melted it. The pressure in the line fell dramatically, and so did the tension in mission control.

As illustrated by this tale, the moments after a landing were tense ones for people in Houston as well as the crew. The final drop to the surface had ended in a minor jolt that, though not seen as serious, had nevertheless applied a deceleration as large as any since the LM had been powered. This was a profound transition between modes. If something were to go wrong – perhaps damage to a tank or an electrical

W. D. Woods, How Apollo Flew to the Moon, Springer Praxis Books,

DOI 10.1007/978-1-4419-7179-1 11. © Springer Science+Business Media. LLC 2011

Jack Schmitt’s view out of Challenger’s, right window at the undisturbed Taurus-Littrow site.

connection shaken loose – then it was more likely to be a problem at that moment, just as on Earth the cheering and plaudits dared to begin.

Go/no-Go decisions had punctuated the flight thus far and now the flight director wanted his controllers to make another, this time on whether the surface phase of the mission should continue – but he wasn’t going to call it ‘Go/no-Go’. It had been pointed out by Bill Tindall that in the heat of an emergency, ‘Go’ could easily be construed as advice to get out of there as much as an instruction to continue with the planned mission and stay on the surface. Therefore this call was ‘Stay/no-Stay’.

Three opportunities were set aside for a possible lift-off soon after landing: T-l was immediate, with the intention to catch up with the CSM on its current orbit. There were only a few minutes available for the Stay/no-Stay decision at T-l to be reached. It would be based on ‘first impressions’. The next opportunity, T-2, would also catch up with the CSM on this orbit but the price of a little more decision time on the surface was a modified rendezvous arrangement. It would be based on a more detailed examination of the telemetry. A third opportunity had to wait two hours while the CSM came back around the Moon so the T-3 decision to Stay/no-Stay could be a little more leisurely. On Apollo 11, the crew began a simulated countdown towards lift-off at T-3 to keep them on top of the procedures, given that they had not practised them for some time. With the operational familiarity gained from Apollo 11, future crews felt such a procedure was not necessary and dispensed with it.

Pete Conrad became a little irritated at the time it was taking for mission control to come up with a decision on T-2. When he prompted them, he raised a little mirth. "Okay, Houston. Are we Go or Stay?”

“Intrepid, Houston," replied Capcom Gerry Carr. “You’re Slay; and if you’d like to recycle and try it again, we’ll talk to Sims."

"No!" laughed Conrad and Bean in unison.

"No, not this time." said Conrad.

The crew and the mission control team had carried out many simulations, usually with difficult problems thrown in. After each shot at simulating a landing, it was common practice to ‘recycle’ and try again immediately. In some respects, their landing had been like a tame simulation but during the launch from Earth, when they had been hil by lightning. Conrad had compared that experience to a particularly tricky simulation. With this in mind, Bean threw a friendly brickbat at the Sim Supervisor. "Yeah. We’re still mad at him for earlier in the week."

Crews did not vent the propellants in the descent stage’s tanks. To do so would have contaminated the surrounding area with noxious chemicals. Only helium was vented to avoid the heal of the lunar day raising the internal pressures of the helium tanks. Then with the LM’s oxygen supply set to feed the cabin instead of the suits, they could remove their helmets and gloves to permit greater freedom to talk and operate the systems.

The next flurry of activity surrounded the guidance system. The platform had to be realigned and to accommodate it, window shades were put in place so their eyes could adapt to view stars through the alignment telescope. The dish of the rendezvous radar, which sat just in front of the telescope’s external optics, was parked face down so it would not obscure the field of view. After the platform had been aligned, the commander would reposition the antenna to face upwards for the remainder of their slay. Rather than use two stars as in a conventional realignment, the crew used the accelerometers in the guidance platform to deduce the direction of gravity. With that vector and a sighting on one star, the alignment of the platform could be restored.

On some missions, after the platform had been aligned, Houston would take control of the guidance system lo perform a little science that would take advantage of their Moon-bound situation. When the spacecraft was in powered flight, the accelerometers in the guidance system measured how much acceleration was being imparted by the engines. But now they were on the Moon, the engines were off, and yet they could still feel acceleration – the gravitational acceleration of the Moon. Without a specialised gravimeter, something that would be added Lo later missions, the accelerometers were a neat means of gaining a local measurement of its strength. Ed Mitchell remembered this from the Apollo 14 flight. "One of the things they did with the platform was to torque [it] to calibrate the accelerometer on each axis in the gravitational field. And, by comparing that with the known calibration of the accelerometers, they could come up with some sort of estimate of the gravitational field. Then they returned the platform to its initial configuration that wc [had] aligned it in as a result of the star sighting."

The next task was to configure the batteries.