“With Neil trying to sleep leaning back on the ascent engine cover, I curled up on the bottom of the LM, where I noticed some of the moon dust on the floor. It had a gritty, charcoal-like texture to it, and a pungent metallic smell, something like gunpowder or the smell in the air after a firecracker has gone off. Neil described it as having a ‘wet ashes’ smell.

In my fatigue, I was still thinking about the dust when I noticed something lying on the floor that really did not belong there. I looked closer, and my heart jolted a bit. There in the dust on the floor on the right side of the cabin, lay a circuit breaker switch that had broken off. I wondered what circuit breaker that was, so I looked up at the numerous rows of breakers on the instrument panel without any guard protectors, and gulped hard. The broken switch had snapped off from the engine-arm circuit breaker, the one vital breaker needed to send electrical power to the ascent engine that would lift Neil and me off the moon. During our powered descent, this same engine-arm circuit breaker had been in the closed position, pushed in to engage the descent engine for our landing, and once we touched down we pulled it back out, in the open position, to disengage the circuitry and disarm the engine. Somehow, one of us must have bumped it accidentally with our cumbersome backpacks as we moved around in the cramped space preparing to get out of the LM, or as we came back in. Regardless of how the circuit breaker switch had broken off, the circuit breaker had to be pushed back in again for the ascent engine to ignite to get us back home We reported it to Mission Control and then tried to sleep and forget about it — as if that were possible. But we knew Mission Control would help figure out a solution, and if we could not get that circuit breaker pushed in the next morning when we were ready to lift off, we would have to do something else. For now, they wanted us to leave the circuit breaker out. So, while Neil and I tried to rest, the guys in Houston debated how we could work around that circuit, in case it had to be left open.

When we received our wake-up call from Houston, the question of how to handle the broken circuit breaker had still not been solved. After examining it more closely, I thought that if I could find something in the LM to push into the circuit, it might hold. But since it was electrical, I decided not to put my finger in, or use anything that had metal on the end. I had a felt-tipped pen in the shoulder pocket of my suit that might do the job. After moving the countdown procedure up by a couple of hours in case it didn’t work, I inserted the pen into the small opening where the circuit breaker switch should have been, and pushed it in; sure enough, the circuit breaker held. We were going to get off the moon, after all. To this day I still have the broken circuit breaker switch and the felt-tipped pen I used to ignite our engines.

Astronaut Ron Evans had taken over as Capcom at Mission Control the morning we were preparing to lift off. Ron instructed us to make sure the rendezvous radar was turned off at the beginning of our ascent. I wasn’t too happy about that, as I preferred having it on, just in case, but at the time I hadn’t learned that it was the rendezvous radar that had overloaded our computers during our landing on the moon. I acquiesced to Mission Control and turned the radar off. We performed an intricate series of star-sightings through our telescope, ascertaining our position vis-à-vis several different stars including Rigel, Navi, and Capella, to align our guidance platform prior to liftoff. By averaging our readings, we would know what kind of orbit we needed to rendezvous with Mike again.

How US was nearly pipped to first moon rock samples

Sir Bernard Lovell tells Erica Wagner how he listened from Jodrell Bank to the drama, with the original audio from 1969

BACKGROUND

• DIY on the Moon: how Buzz saved the launch back to Earth

• Moon rock of ages

• Apollo Gadgets: Can you guess what they were for?

• The Moon: Gods, myths and legends

Related Internet Links

• Moon landing 40th anniversary special supplement

• The 21 best space toys

The liftoff from the moon was intrinsically a tense time . The ascent stage simply had to work. The engines had to fire, propelling us upward, leaving the descent stage of the LM still sitting on the moon. We had no margin for error, no second chances, no rescue plans if the liftoff failed. There would be no way for Mike up in Columbia to retrieve us. We had no provision for another team to race from Earth to pick us up if the Eagle did not soar. Nor did we have food, water, or oxygen for more than a few hours.

As we completed all the liftoff procedures, Ron Evans gave me one last bit of instruction. “Roger, Eagle. Our guidance recommendation is PGNS [preliminary guidance navigation system], and you’re cleared for takeoff.”

Knowing the pressure everyone felt, I spontaneously injected a touch of humor into the situation. Maintaining a steady, serious tone to my voice, I responded, “Roger. Understand. We’re number one on the runway.” Unfamiliar with my sardonic sense of humor, Evans paused for a few seconds as he processed my remark, and then simply replied, “Roger.”

The computer continued to count down the seconds to liftoff. Standing side by side again, Neil and I looked at each other, took one more furtive glance at that impaired circuit breaker, threw the switches, and held our breath. The LM engine fired, belching a plume of flame and blasting lunar dust as we rose off the surface. The liftoff went smoothly. I wanted to cast a last look back at the surface, but our attentions were focused on navigating the spacecraft. The ascent of the Eagle was strikingly swift compared with the liftoff of the huge Saturn V rocket from Cape Canaveral. For the Eagle’s liftoff, we had no atmosphere resisting us, and only one-sixth gravity to overcome, so even though we had worked on this aspect of the flight in simulators, the Eagle’s speed in whisking us into space was almost surprising. Nothing we had ever practiced in simulators could compare with our swift swoop upward. Within seconds we were streaking high above the moon’s surface.”

Magnificent Desolation: The Long Journey Home from the Moon by Buzz Aldrin with Ken Abraham is published by Bloomsbury on July 9, £16.99

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