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A felt-tipped pen helped Buzz Aldrin close a damaged Lunar Module circuit breaker so Apollo 11 could continue its ascent preparations. The problem was not a broken engine: the engine-arm breaker’s plastic knob had come off, leaving the recessed switch difficult to operate by hand. Aldrin used the pen to press the mechanism, and Mission Control confirmed the circuit was complete.
What broke on the Apollo 11 lunar module?
During preparations to leave the Moon, Aldrin noticed that one circuit breaker was out of position. The missing part was the plastic knob on the Lunar Module’s engine-arm circuit breaker—not the ascent engine itself. NASA’s mission-report finding, quoted in its post-EVA commentary, says the breaker was successfully closed when required for ascent, but the lost knob would not allow manual opening. NASA’s post-EVA commentary
The breaker mattered because it was part of the ascent-engine arming sequence. In his later account, Aldrin described seeing the broken plastic piece on the floor, tracing the abnormal breaker position to the “engine arm” label, and recognizing that the normal procedure could not be completed. Aldrin’s account in the Apollo Lunar Surface Journal
How did the felt-tip pen work?
The recessed mechanism remained reachable through the opening in the panel. Aldrin considered pushing it with a finger, but worried about contact with the live electrical point; a metal ballpoint pen seemed unsafe for the same reason. The felt-tip pen had a narrow tip that could reach the mechanism without presenting a metal point. NASA’s journal records the practical result: “Luckily, a felt-tipped pen fit into the slot.” NASA’s post-EVA commentary
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Aldrin later recalled, “But I did have a felt tip pen, push it in, and Houston says, ‘Hey, we got power. Let’s go.’” Mission Control’s confirmation that the circuit was complete allowed the countdown to proceed. Aldrin’s account in the Apollo Lunar Surface Journal
The technical transcript captures the crew’s concise report: “We just had one circuit breaker out of position.” NASA’s Apollo 11 air-to-ground transcript
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Could the astronauts have taken off without it?
The sources establish that the breaker was needed for the ascent-engine arming sequence and that the knob’s loss prevented normal manual operation. They do not establish that the pen itself was the only conceivable way to leave the Moon. Mission Control asked the crew to rest while engineers considered a workaround; Aldrin’s account says no alternate repair was found, so the engine-arm action was moved earlier in the countdown. In the event, the pen let Aldrin press the breaker and Houston verified the circuit before the countdown continued. Aldrin’s account in the Apollo Lunar Surface Journal
Was it really a felt-tip pen?
Yes. ABC News identifies the flown object as a Duro Marker felt-tip pen and reports that it and the broken circuit breaker are displayed at Seattle’s Museum of Flight. ABC also reports that the pen used a pressurized ink cartridge and could work in weightlessness, underwater, and extreme temperatures; those are details from ABC’s account, not NASA performance specifications. ABC News on the Apollo 11 pen
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- BRIGHT, VIVID COLORS: Add a blast of fun to all your writing
- MEDIUM POINT PENS: 0.7mm felt tip produces bold, expressive lines to match your personality
- SMEAR-PROOF AND FADE-RESISTANT: Secure your work from smudging or fading away
- WON'T BLEED THROUGH PAPER: Specially designed water-based ink
- DURABLE POINT GUARD: Prevents the tip from fraying so lines stay clean and the party never stops
What changed after Apollo 11?
NASA’s archival journal says guards were placed over the breakers on later flights and additional checklist checks were added. The Apollo 11 Mission Report search record specifies that guards were fitted on Apollo 12 and subsequent vehicles to help prevent impacts from the oxygen-purge system from damaging the controls. NASA’s post-EVA commentary Apollo 11 Mission Report record
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- SMEAR-PROOF AND FADE-RESISTANT: Secure your work from smudging or fading away
- WON'T BLEED THROUGH PAPER: Specially designed water-based ink
- DURABLE POINT GUARD: Prevents the tip from fraying so lines stay clean and the party never stops
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