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Apollo 11

One hour, four layers: the EVA-prep overrun traced through the full procedural chain

EVA preparation was supposed to take about two hours; from “we are beginning our EVA PREP” to Armstrong on the porch took 3 h 08 m. This analysis traces that missing hour through the four documentary layers the LM onboard checklists concept names as the library’s procedural chain — plan → checklist → transcript → debrief: what was intended, what the crew’s hands were instructed to do, what happened on the loop, and how it felt eleven days later. The schedule frame is the EVA planned-vs-actual concept; checklist pages were read as page images from the raw scan (pdftoppm), and every quotation was verified in the raw transcript, Mission Report, and debriefing files.

Layer 1 — The plan: two tidy hours, after a nap

Section titled “Layer 1 — The plan: two tidy hours, after a nap”

The LSOP and the Flight Plan (nominal timeline) placed EVA prep after a 4-hour rest and an eat period: a STAY/NO-STAY check for EVA prep at ~110:30, PLSS/OPS donning through 111–112, cabin depress (“START EVA”) at 112:30, commander egress at 112:39. The Mission Report (§4.12.2) states the duration assumption and — crucially — the cockpit it was rehearsed in:

“In simulations, 2 hours had been found to be a reasonable allocation; however, everything had also been laid out in an orderly manner in the cockpit, and only those items involved in the extravehicular activity were present.”

Table 11-I’s first row carries the plan’s last increment: “final preparation for egress,” planned 10:00 (min:sec). None of the planning documents carry a contingency for a connector that wouldn’t seat or a cabin that wouldn’t bleed down — those lived below the plan’s resolution.

Layer 2 — The book: SUR-27…SUR-33, with the crew’s own pen marks

Section titled “Layer 2 — The book: SUR-27…SUR-33, with the crew’s own pen marks”

The LM Lunar Surface Checklist (SUR pages, image-only scan) is the as-flown script. Its EVA-prep sequence, read page by page:

  • SUR-27 — “PLSS/OPS DONNING.” Staging: PLSS off the floor and against the forward hatch, OPS checkout (“Verify OPS O2 press 5880±500 psia”), lunar overshoes donned with each other’s assistance, purge valves to the ISA middle pocket, LEVAs and EV gloves staged aft, chronometers onto the right EV gloves, the CSRC into Armstrong’s leg pocket.
  • SUR-28 / SUR-29 — the two donnings, mirrored. Each crewman in turn: “Turn right [left] and back into PLSS… Don PLSS/OPS by securing PLSS upper and lower straps to PGA… Unstow RCU…” — then a boxed WARNING (“Before connecting RCU to PLSS, all elec PLSS cont must be in off position”) and the single printed line the hour would hinge on: “Connect RCU electrical to PLSS.”
  • SUR-30 — “PLSS/EVCS ELECTRICAL CHECKOUT.” First line: “Comm panel — S-band Modulate — FM”; both audio panels to “VOX sens — max increase” (the setting the anomaly register shows was probably sitting low during the EVA, §16.2.8); “Disconnect LM comm cable from PGA… Connect PLSS electrical umbilical to PGA.”
  • SUR-32 — final preps. PLSS warning-tone and O₂ checks, then “FINAL EVA EQUIPMENT PREP FOR EGRESS” (OPS actuator to the RCU) and “FINAL SYSTEMS PREP FOR EGRESS”: “Confirm ‘GO’ for cabin depress with MSFN”, “Des H2O vlv — close,” “Verify Cabin fan 1 C/B — open,” suit-gas diverter and cabin-gas-return valves to EGRESS.
  • SUR-33 — “PREP FOR CABIN DEPRESS.” OPS O₂ hoses to the suits, purge valves retrieved and locked in (“verif clos & lkd pin instl”), anti-fog, and the two-man choreography of the final seal: Armstrong places and locks Aldrin’s helmet, Aldrin places and locks Armstrong’s, LEVAs attached, EV gloves “and ‘lock’” — then “Unstow cue cards: Hang-down, Final EVA Configuration, & EVA Card No. 1… Stow Lunar Surface Checklist in purse.” The book ends here; the depressurization and the moonwalk itself ran from cue cards, and the next page (SUR-42) resumes at “POST EVA.”

The page-level pace record. Three handwritten GET hacks survive on the scanned pages — “106 49” atop SUR-27’s PLSS/OPS DONNING header, “107:31” on SUR-28 beside the RCU warning block, and “108 01” atop SUR-30’s electrical checkout. The crew’s own pen brackets the donning-and-connector block at 1 h 12 m (106:49 → 108:01) — and the last mark matches the loop to the minute (below).

Layer 3 — The loop: long silences, then the book read aloud

Section titled “Layer 3 — The loop: long silences, then the book read aloud”

The air-to-ground record carries the prep as sparse status calls between long off-loop stretches of two men working in a phone-booth-sized cabin:

106:11:14 CDR: “Houston, this is Tranquility Base. We are beginning our EVA PREP.” — CC: “Roger. Copy. You’re beginning EVA PREP.” (the Mission Report’s 106:11:00 anchor, live)

108:01:03 LMP: “Houston, Tranquility. We’re ready to start with the electrical checkout. We’re going to S band modulate FM.” (the pen mark “108 01” on SUR-30, whose first printed line is exactly “S-band Modulate — FM” — pen, page, and loop agree to the minute)

108:22:01 CDR: “Houston, this is Tranquility. We’re standing by for a GO for cabin DEPRESS.” — CC: “Tranquility Base, this is Houston. You are GO for cabin depressurization. GO for cabin depressurization.” (SUR-32’s “Confirm ‘GO’ for cabin depress with MSFN,” executed verbatim — and the next calls are the checklist read aloud: “And the descent water valve is closed” = “Des H2O vlv — close”; “Verify cabin fan number 1 circuit breaker open” = “Verify Cabin fan 1 C/B — open”)

108:56:22 CDR: “Okay. Cabin pressure going towards zero… Ready to open the hatch when we get to zero.”

109:06:22 CDR (to Houston’s status query): “Everything is GO here. We’re just waiting for the cabin pressure to bleed… It’s about 0.1 on our gage now.”

109:07:33 CDR: “The hatch is coming open.”

109:19:16 CDR: “Okay. Houston, I’m on the porch.”

Layer 4 — The debrief: where the time actually went

Section titled “Layer 4 — The debrief: where the time actually went”

Eleven days later (Vol. 1 §10), the crew named the sinks. The connector (the register’s anomaly 16.3.2):

Aldrin: “We had problems with this one particular electrical connector, the one that joins the RCU to the PLSS, ever since the first time we’d ever seen it.” — Armstrong: “It’s about a 50-pin Bendix connector.” — Aldrin: “It’s just very difficult to get the thing positioned properly so that the three pins on the outside… will engage in the ramp so that, when you then twist, it’ll cinch on in. That must have taken at least 10 minutes. The problem was not with mine, but in hooking up Neil’s.” — Armstrong: “This is not because we didn’t understand the problem. We had had trouble with that connector for 2 years or more. We’d always complained about it. It had never been redesigned.”

(Note the agreement with the pen marks: the “107:31” hack sits at the RCU step of the donning sequence — inside the block the pen brackets at 72 minutes.)

The clutter — the simulator assumption failing (Mission Report §4.12.2, the report’s own words, fed by this debrief):

“In fact, there were checklists, food packets, monoculars, and other miscellaneous items that interfered with an orderly preparation. All these items required some thought as to their possible interference or use… This interference resulted in exceeding the timeline estimate by a considerable amount.”

The depressurization (Armstrong) — the sequence “never completely performed on the ground”:

“It took a very long time to depressurize the LM through the bacteria filter… [we] weren’t familiar with how long it would take to start a sublimator in this condition. It seemed to take a very long time to get through this sequence of getting the cabin pressure down to the point where we could open the hatch, getting the water turned on in the PLSS, getting the ice cake to form on the sublimator, and getting the water alarm flag to clear… It seemed like it took us about a half hour to get through this depressurization sequence. And it was one that we had never duplicated on the ground.”

And the crew’s verdict on the book itself — matching the Mission Report’s “the extravehicular activity preparation checklist was adequate and was closely followed”:

Armstrong: “We shouldn’t imply that the EVA preparation checklist wasn’t good and adequate. We did, in fact, follow it pretty much to the letter just the way we had done during training exercises.”

The hour, reconstructed

Section titled “The hour, reconstructed”
GETEventLayer
106:11:14”We are beginning our EVA PREP”loop (Mission Report: 106:11:00)
106:49pen mark — PLSS/OPS DONNING page (SUR-27)book
107:31pen mark — donning page, at the RCU warning block (SUR-28)book
108:01:03pen mark (SUR-30) and loop — “ready to start with the electrical checkout”book + loop
108:22:01–06”Standing by for a GO for cabin DEPRESS” → “You are GO”loop (= SUR-32 step)
108:56:22”Cabin pressure going towards zero”loop
109:07:33”The hatch is coming open”loop
109:19:16”I’m on the porch”loop
(109:24:48)(the first step — EVA timeline)

The increments: 38 m from prep start to donning start (equipment staging in a cluttered cabin); 1 h 12 m for the donning-and-connector block the pen brackets (with “at least 10 minutes” on one connector alone); 21 m of checkout and final systems prep; 45 m from the GO to a hatch actually open (the cabin bleeding through the bacteria filter to a gauge floor of 0.1 psi — Table 11-I books “final preparation for egress” at 20:45 against 10:00 planned, with ~8½ minutes from a 0.2-psia reading to hatch opening); 12 m from hatch to porch. Total 3 h 08 m against the simulations’ 2-hour allocation — the missing hour, fully accounted for by the connector, the clutter, the never-rehearsed depress, and a pace that was deliberate by intent (the Mission Report: prep “was conducted slowly, carefully, and deliberately, and future missions should be planned and conducted with the same philosophy”).

Two codas. The overrun cost the mission nothing: because the crew had swapped the EVA ahead of the rest period (decision 104:40:00), Armstrong was on the porch ~3 h 20 m before the plan’s 112:39 egress moment. And the fixes went to Apollo 12 via the anomaly register: a redesigned RCU connector with a captive lock ring (§16.3.2) and no bacteria filter — final decompression cut “from about 5 minutes to less than 2” (§16.2.6).

Sources

Section titled “Sources”