‘Weaving Up the Freeway’: The Triumph of Apollo 10 (Part 4)

One hundred and sixty thousand kilometres from home, this electrifying view of Earth from Apollo 10 reveals many of the lands around the Mediterranean, from whence “Western” civilisation arose. Photo Credit: NASA

Forty-five years ago this week, three astronauts circled the Moon. Their spacecraft had many of the provisions needed to execute a landing—a command and service module, which they had nicknamed “Charlie Brown,” and a lunar module, “Snoopy”—but on this “F mission,” the crew of Apollo 10 would perform a full dress rehearsal for humanity’s first landfall on alien soil. They would test the descent engine, guidance and navigation systems, and radar of the lunar module, would rendezvous high above the Moon, and in doing so would clear the final hurdle in anticipation of the historic Apollo 11 voyage in July. In doing so, however, Tom Stafford, John Young, and Gene Cernan would come face to face with the immense risk that they were taking and would depart the Moon fully aware that the journey was fraught with danger and complexity.

Early on 20 May 1969, Stafford and Cernan shimmied through the short tunnel from Charlie Brown into Snoopy. Their day began with an irritating problem with a radar gauge, then a communications difficulty, and later an error with the lunar module’s gyroscopic stabilisation platform. Precisely on schedule, Apollo 10 disappeared behind the Moon on its 12th orbit and, when the radio blackout ended 40 minutes later, Stafford jubilantly announced that Charlie Brown and Snoopy had successfully parted company. After the undocking at 2:00:57 p.m. EDT, Young used his thrusters to withdraw from the lander.

“You’ll never know how big this thing gets when there ain’t nobody in here but one guy,” he drawled.

You’ll never know how small it looks when you’re as far away as we are!” countered Cernan.

“Yeah,” continued Stafford. “Don’t get lonesome out there, John.”

As the range opened, it was Young’s task to activate a homing receiver for the lander’s rendezvous radar, and he had to toggle a switch several times to make it work properly. Then a glitch with the orientation of Snoopy’s antennas affected communications with Charlie Brown. Next, the link between Charlie Brown and Houston fell silent. “A quick check of the system,” wrote Stafford, “showed that a breakdown had occurred in the line between Houston and the tracking station in Goldstone, California.” At length, the problems ironed out. For the next eight hours, Young would score a new record: the first man to fly solo in lunar orbit.

Somewhere behind the Moon, during the first of Snoopy’s four independent orbits, Stafford fired the descent engine for the first time to reduce its velocity and begin dropping toward the lunar surface. He started the engine at its minimum thrust level—first 10 percent, waited for a few seconds, then opened the throttle to 40 percent—and, from his vantage point, John Young reported that they were moving noticeably away from him. For the men aboard the lander, on the other hand, the ride seemed relatively slow and established Snoopy in an elliptical orbit with a perilune of 9 miles (15.4 km) above the surface. The two astronauts, broadcasting on “hot-mike” to the whole world, were exultant.

“We is down among ’em, Charlie!” radioed Cernan.

“Rog, I hear you’re weaving your way up the freeway,” replied fellow astronaut Charlie Duke, the capcom in Mission Control.

Twelve miles (20 km) above the Moon, as intended and precisely on cue, the radar detected the looming surface and began feeding rate-of-descent and altitude data into Snoopy’s computer. The lunar mountains, rushing past below, seemed almost close enough to touch, their appearance and texture resembling wet clay. As they approached Mare Tranquillitatis, running along an imaginary “lane” of physiographic features memorised from months of studying maps and charts, the timeless majesty of Earthrise peeked above the horizon. Also astounding was the sheer barrenness of the forbidding terrain. “There are enough boulders around here,” Stafford breathed, “to fill up Galveston Bay.”

Since their assignment to the mission the previous November, Stafford and Cernan had spent hundreds of hours poring over maps and photographs from the unmanned Lunar Orbiters of two of the candidate landing sites for Apollo 11. Both lay in the relatively flat Tranquillitatis region, and the men had even tried to simulate part of their trajectory aboard a T-38 aircraft back on Earth. When the time came to fly over the favoured landing spot, “Site 2,” for real, they knew the craters, mountains, rilles, bumps, hollows, and furrows so well that they literally formed a familiar “road,” guiding them toward the landing zone. To their eyes, it was a virtual lunar highway and they had nicknamed it “U.S. 1.” Along the way, a range of low mountains was called the “Oklahoma Hills,” a rille which split into a pair of craters was dubbed “Diamondback” and “Sidewinder” and one ridge was even named in honour of Stafford’s then-wife, Faye.

Hypatia Rille, nicknamed “U.S. 1” by the Apollo 10 crew, is the snaking, linear feature in the top left of this image, leading toward the Site 2 region in the top right. Photo Credit: NASA

Attempting to shoot a photograph every three seconds as Snoopy passed over Site 2, Stafford was annoyed when the “goddamn” Hasselblad issued an ominous puff of smoke and jammed. (He later apologized to Victor Hasselblad upon his return to Earth.) It was the first of a number of unfortunate outbursts from Snoopy’s cabin. Deprived of his camera, Stafford resorted to verbal reports, comparing the inhospitable appearance of the site to the high desert near Edwards Air Force Base in California. If Neil Armstrong and Buzz Aldrin were to find themselves heading for the “near” end of the target ellipse, then they would have a smooth landing; but he advised that a landing at the “far” end would demand additional fuel to find a spot free of boulders. Just beyond Tranquillitatis, and an hour after the first burn, Stafford again fired Snoopy’s descent engine, this time using full throttle to accelerate them by almost 125 mph (200 km/h) and enter an eccentric orbit that simulated an ascent from the surface.

When the time came to jettison the descent stage and return to redock with Young, Stafford oriented the vehicle correctly but noted a slight yaw rate on his attitude indicators. “Telemetry suggested we might have an electrical anomaly,” he wrote, “so I started to troubleshoot the problem.” Shortly thereafter, Cernan, thumbing through his checklist, switched control from the Primary Navigation, Guidance and Control System (PNGS) to the Abort Guidance System (AGS). The former provided an exact navigational reading, whereas the latter would “get us the hell out of there if unexpected trouble cropped up.” In case Armstrong and Aldrin needed to abort in a hurry—punching their ascent stage away if their descent went awry—a test of the AGS in lunar orbit was critical. Stafford and Cernan had rehearsed it a hundred times in the simulator. Clad in their bulky suits, however, high above the Moon, both men found it difficult to hit the right switches. An instant after Cernan set the control mode of the AGS to “attitude hold,” Stafford reached across and inadvertently changed it to “auto.”

Seconds later, they were ready to blow the four explosive bolts to separate the ascent stage from the descent stage and begin to trek back to Charlie Brown. Suddenly, and without warning, Snoopy went berserk, lurching wildly in both pitch and yaw axes. “Gimbal Lock!” shouted Stafford urgently, believing the lander’s gyros to have frozen. Then, Cernan, over hot-mike and with the whole world listening in, yelled with unfortunately crystalline clarity: “Son-of-a-bitch! What the hell happened?” As the menacing lunar terrain, the black sky, and the grim line of the horizon alternately flashed in Snoopy’s windows, both men knew they had just seconds to resolve whatever was wrong.

By activating the AGS and mistakenly setting it to “auto,” Stafford had in effect instructed Snoopy’s radar to begin searching for Charlie Brown and the abort guidance system was now causing the lander to flip wildly around its center of mass. Quickly, he pushed the button to jettison the descent stage and steadily regained control of the gyrating ascent stage. Fearing that the inertial measurement unit was close to gimbal lock, Stafford executed a pitch maneuver, started working the attitude switches and finally calmed the ascent stage down. From Cernan’s initial shout to Stafford’s final report to Houston that Snoopy was back under control, three minutes elapsed. Those minutes were unnerving not only for Stafford and Cernan, but also for John Young, listening helplessly from Charlie Brown. “I don’t know what you guys are doing,” he drawled in his typically understated manner, “but knock it off. You’re scaring me!”

With the descent stage gone and an ascent stage finally under full control, Tom Stafford and Gene Cernan guide Snoopy back toward Charlie Brown. Photo Credit: NASA

Years later, Cernan and Stafford would both say that it was a classic piloting error. “Neither Tom or I can be sure,” Cernan related, “but when it came time to stage … there was some switch that had to be changed, and I changed it. And I’d be willing to bet that … I put the switch in the new position and Tom went ahead and moved it back to the old one. His action was to move the switch. I’d already done it for him. But he didn’t know that and, when he moved the switch, he just moved it back to where it was. In effect, we created the problem!”

Although the cause of the glitch was easily solvable in time for Apollo 11, the episode highlighted that nothing could be taken for granted on a lunar expedition. Charlie Duke, helpless to assist, had warned them from his data that they were close to gimbal lock, but things were moving far too quickly for him or anyone else in Mission Control to help. By contrast, the return to Charlie Brown was perfect; Stafford found Snoopy’s ascent stage a little difficult to hold steady, but Young had no problem docking and all three men were greeted by the welcome “ripple-bang” of a dozen capture latches snapping shut. “Snoopy and Charlie Brown are hugging each other,” chortled Stafford. A few minutes later, at 11:25 p.m. EDT, back in the command module, Young received a couple of hugs, too.

Perhaps Stafford might not have been quite so welcoming had he realised that Young had used some of his relatively private time, alone in Charlie Brown, performing his very first “bowel movement” in almost five days aboard Apollo 10. Consequently, when Snoopy’s ascent stage was jettisoned a few hours later, into permanent solar orbit, it carried with it a UN flag, a small flag from each state of the Union, the command module’s now-unneeded docking probe, a pile of empty food packets … and Young’s bag of faecal goodies. “We joked that Snoopy would have food, water, oxygen, organic material, all the ingredients for the creation of life,” Stafford later wrote with glee. “Maybe a few billion years from now, some kind of Snoopy monster, distantly related to John Young, will emerge from somewhere in the Solar System … ”

At 6:25 a.m. EDT on 24 May, a perfect engine burn sent Charlie Brown hurtling home. Two days later, they hit Earth’s atmosphere at a lunar-return velocity of close to 25,000 mph (40,000 km/h). Cernan remembered an enormous white and violet “ball” of flame, literally sweeping up the command module like a glove. “It grew in intensity,” he wrote, “and flew out behind us like the train of a bride’s gown, stretching a hundred yards, then a thousand, then for miles … and the whole time we were being savagely slammed around inside the cabin.”

Charlie Brown descends toward splashdown on 26 May 1969. Photo Credit: NASA

To some people, the fire and brimstone nature of re-entry illustrated God’s wrath with this foul-mouthed team of space fliers. One man who was not happy, was an over-zealous Christian minister named Larry Poland. He was vocal in complaining that Stafford’s crew had taken “the language of the street” with them to the Moon, and urged them to apologize for their “profanity, vulgarity and blasphemy.” However, recognizing the reality that its men were in a life-or-death situation, NASA managers stood by the crew, saying they had “acted like human beings.” After splashdown, they were greeted with tongue-in-cheek notices, one of which read: The Flight of Apollo 10: For Adult Audiences Only. Bob Gilruth, the head of the Manned Spacecraft Center in Houston, had burst out laughing when he heard the swearing, and veteran flight director Chris Kraft was philosophical in his autobiography, Flight. “They were out there doing man’s work at the Moon,” Kraft wrote. “If a cuss word or three slipped out, well, who the hell cared anyway?”

Larry Poland cared greatly and laughing it off was not good enough. In the days and weeks after the mission, hundreds of letters and telegrams flooded into NASA’s Washington headquarters, some tolerating the language, others condemning it. John Young was not involved and Tom Stafford (famously nicknamed “Mumbles”) had uttered his profanities under his breath. Gene Cernan, though, was well and truly in Reverend Poland’s firing line. His words could neither be misconstrued nor explained away. At a news conference, Cernan apologized to the people he had offended and thanked those who understood how he came to say what he did. Privately, though, he was furious. It made no difference, he wrote, that Poland accepted his apology and forgave him, for Cernan “never got around to forgiving that self-righteous prig!”

It was the only unfortunate incident to blight a mission which had otherwise proved enormously successful; by verifying the performance of the entire Apollo spacecraft in orbit around the Moon, Apollo 10 had cleared virtually every remaining hurdle in the path to the first lunar landing. By the end of May 1969, humanity’s date with destiny was less than seven weeks away.


This is part of a series of history articles, which will appear each weekend, barring any major news stories. Next week’s article will focus on STS-77, a May 1996 mission which showcased virtually all of the shuttle’s capabilities … and even unfolded an inflatable antenna to boot.


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  1. Ben – Thank you so VERY MUCH for the generous gift of an ABSOLUTELY MARVELOUS article. You are an exceptional writer Ben, giving “the eager audience an unprecedented sense of ‘being there'”. (Yeah, thanks Ben, after reading about Cernan and the snowstorm of fiberglass from the command module tunnel that “itched like hell” and “stuck to hair, eyebrows and lashes”, I still can feel the itch). This series is without doubt the result of a great deal of effort, and I will enjoy re-reading it so as to absorb as much of the invaluable information as possible. Certainly there are many of your readers who also thoroughly enjoyed this work. Your article also re-affirms why Cmdr. Eugene Cernan is one of my favorite astronauts for whom I have the utmost respect and admiration. I do have a matter that only someone possessed of your depth of knowledge could resolve. I have heard that faced with a crew of hyper-motivated, extremely intelligent, over-achievers flying to within “spitting distance” of the lunar surface, NASA managers made it known that the ascent stage had been “short-fueled” which would have made an unscheduled descent to the lunar surface a one way trip. Now this may be just a myth told by old spacers around the campfire, but it does make one think “hmmm, I wonder …” Again, thank you Ben for the great work which provided so much enjoyment!

  2. In a word, magnificent! Ben, you have written an extremely important series on what is often overlooked as a vital mission leading the ultimate human triumph of landing human beings on another world. Stafford, Young and Cernan deserve a special status in the historical annals of manned spaceflight and will forever remain true American heroes. Thank you, Ben!

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