Moonport: A History of Apollo Launch Facilities and Operations

The Slowest Part of the Trip

Apollo 9, like every Apollo-Saturn V, started its epochal journey with the trip from the assembly building to launch pad 39. Eventually astronauts would travel at speeds in excess of 40,000 kilometers per hour, but l.1 was about as fast as the crawler crew dared move the transporter with the Apollo-Saturn on its mobile launcher - an unwieldy 5,715 metric tons rising 137.5 meters above the ground. "You can't imagine the difference between 0.7 and 0.9 miles per hour with this weight," one of the hydraulic engineers said. "At 0.3 the ride is very smooth, at 0.8 the vibrations may be noticeable but tolerable, and at 0.9 it might be difficult."7

Fred Renaud, a crewman on the crawler, had called it a "Texas tractor" in conversation with Representative Robert Price of Texas.8 But a local newspaper was to refer to it as "one of the strongest, slowest, biggest, strangest, and noisiest land vehicles ever devised by man." With pardonable exaggeration, the newspaper spoke of the 5.6-kilometer trip as "nearly as important as the 500,000 miles [870,000 kilometers] to and from the moon."9

Each transporter had two cabs containing the usual controls found in an automobile: an accelerator, foot and parking brakes, speedometer, air conditioner, adjustable seat, and windshield wiper, plus radio for two-way communications. While the accelerator on the family car controls a single engine rated at around 250 horsepower, the crawler's accelerator controlled 16 motors with a capacity of more than 6,000 horsepower. But starting a car, even on a winter morning, was easy compared to getting the crawler-transporter ready to move. It took an hour and a half for the crew of 14 to warm up the six diesel engines, energize several dozen electrical circuits, start up three hydraulic systems, one pneumatic system, a fuel system, and two lubricating systems, and make a series of checks called for by the 39-page "Start-Up Procedure Manual."

Handling such a monster required a cool head, extreme patience, and much teamwork, especially while loading and unloading at either end of the trip. Inside the assembly building, the crew had to steer the transporter with the aid of gauges, guidelines, and the judgement of technicians stationed at strategic points with walkie-talkie radios; and to bring it to within 5 centimeters of a set of pedestals ranging across the 45.7-meter width of the mobile launcher, so that the load could be firmly bolted down.

"When a man stands next to the crawler, the crawler looks big," Bruce Dunmeyer, supervisor of the transporter team, said, "but when you see the crawler under the mobile launcher, the crawler looks incapable of lifting such a big load." Spectators, and sometimes the crewmen themselves, were to feel that at any moment spacecraft and launcher could tip over and crash to the ground. Renaud described a typical run down the level part of the crawlerway:

This part of the move is not particularly hard. . . . the main concern is just staying on the road, and if you have to stop quickly, don't lean on the brake. The small jolts and jerks down here are sledge hammers at the top. One of the hazards is you tend to over-control the machine because it takes things so long to happen. You come up to a curve, put in a steering signal, and about 25 minutes later you come out of the curve. The tendency is to put all the steering on at once.10
The transporter had a crew of as many as 30, most of them with walkie-talkie radios, to monitor the last stage of the trip, the 365-meter incline with a grade of about 5%. The control room engineers and the head engineer supervised the critical task of keeping the Apollo-Saturn on an even keel while ascending the grade. This meant an endless chain of orders to systems of the transporter, including the cab engineers. William Clemens, one of the control engineers, felt that negotiating the grade was easier on the way up because there was so much excess power. But coming down, the driver could not allow the crawler to move too fast. "She wants to free wheel and coast," he stated, "and if you overspeed too far the diesel engines will shut off - which spells trouble! You must keep the speed under control."11

In Supervisor Bruce Dunmeyer's view, connecting the mobile service structure to the Saturn V at the pad was the trickiest and most delicate maneuver of all. The service structure towered 122.5 meters above the ground and provided access platforms for final checking of the Apollo spacecraft and the booster stages. "You have only a few inches of clearance when you are mating the structure to the pad," said one of the hydraulic engineer chiefs. "There are clamshelled doors that hinge and close around the bird, and if you run into it, there will be no shot. It is as simple as that."12 Just before launching, the crawler-transporter would take the mobile service structure back to its parking area. The crawler crew's work represented hours of extreme tension between days of routine. In spite of this, the original crew was to see little turnover, with only two men leaving over the years.