Apollo 17: TLI-ing through sunrise

Fifty years ago: The Apollo 17 photo of the full Earth, showing the Middle East (at top), Africa and Antarctica.


We’re Apollo 17 — three hours after launch, on our second and final Earth orbit, entering darkness, approaching the U.S.  It’s the early morning of December 7, 1972,  You call down, “Comm check, Bob.”

You are Dr. Rock, geologist Jack Schmitt, our Lunar Module pilot. Our capcom is Bob Overmyer, who radios, “Houston.  Go ahead.”

“I was just checking with you; you’re so quiet down there, we almost forgot you were there.”

“Roger. Don’t want to forget me. We’re just watching everything; we can’t find anything wrong,” so we’re just trying to keep quiet here.

We’re approaching the big moment — TLI — The TransLunar Injection.   I’m Mission Commander Gene Cernan.  Beside me is our Command Module Pilot Ron “Captain America” Evans, our nickname for him since he will pilot the command ship America most of the time.  

You tell Overmyer, “You ought to look for the good things rather than the bad.”

“Well, that’s good when we don’t find anything wrong.”

“Can’t agree more.”

I call, “OK, Bob. We’re watching the S-IVB tanks pressurize.”  That’s our third stage, still attached, ready to send us in minutes on our way to the moon.  TLI.  This will be the last TLI in a long, long time.  The third stage will fire a few seconds short of 6. min. to lift us out of the 112-mi.-high orbit we’re in.  When the burn is complete, we’ll already be at an altitude of 172 mi. and pulling away fast, about 24,000 mph.  Yet already losing velocity in the Earth’s relentless gravity.  

Small “ullage” engines fire to settle the propellants in the tanks.  We’re 53 seconds from ignition.

Overmyer calls, “Seventeen, you’re looking great on the final status check here, and you’re go for TLI.”

I call, “The light’s on, and we have ignition.”  We’re precisely 3 hr. 12 min. 37 sec. into the flight.

“Seventeen, Houston. You’re looking good, and the thrust is go.”   

“. . .We’re Go onboard at 20 seconds.”

A minute into it.  The Propellant Utilization (PU) valve on the third stage’s single J-2 engine adjusts the fuel/oxidizer mixture ratio for most efficient use of the propellants.  Thrust increases by 13 percent, and we feel the surge.  That third stage makes waves as it rolls along, a nice reassuring pulse.

I call, “Confirm a PU shift, and go at 1:45.”

“Seventeen, Houston, We can confirm PU shift, and you are go.”

. . . Coming up on 3 min. into the burn.  I call, “And it’s a good ride, although it’s rumbling around a little bit.  . . . We are go.”  Halfway there — and moving out of darkness.  Sunrise surprises us in its suddenness.

Keep going, S-IVB.  We’re getting there, now 5 min. into the burn.  “And we’re still go here, and we’re TLI-ing right through sunrise.”

A minute to go!  Come on, come on . . .

“Seventeen, Houston. Your burn time is nominal.”

“Roger. Understand burn time, nominal.”

From the righthand seat, you call, “Cut-off at 52.”  That’s 5 min. 52 sec. after ignition.

I call it:  “And it was an auto cut-off – auto cut-off on time.”

Overmyer replies, “Understand a guided cut-off on time. Looking great.”


Moon-bound, yet it won’t mean much without what happens in the next half hour.  It’s called Transposition and Docking.  Right now our lunar lander, named Challenger, is tucked inside a shell (the “Saturn Lunar Adapter”) atop the third stage behind us.  We have to pull the command ship — the conical Command Module containing the crew cabin and the cylindrical Service Module housing supplies and maneuvering engines — away from the third stage.  Drift out a bit, turn around — as four panels around the upper part of Challenger split like flower petals and are pushed away by springs.  We will slowly ease in and dock the nose of the Command Module to the LM.  Then pull it free.  I say we, but Ron is in charge of this task, and so Captain America holds the lefthand pilot’s seat.

It’s now 3 hr. 33 min. 58 sec. since launch.  Overmyer calls, “And Booster engineer reports from telemetry data that the booster has begun maneuvering into the proper attitude for spacecraft separation.”

“Okay. We are maneuvering, Houston.”

From your righthand window, you observe, “Now we’ve got a few very bright particles or fragments or something that go drifting by as we maneuver.”  It’s probably ice particles from the third stage.

Ron adds, “There’s a whole bunch of big ones on my window down there – just bright.”

You say, “Yeah. Now you can see some of them in shape. They’re very jagged, angular fragments that are tumbling.”

Overmyer asks, “Roger. They look like fluid of some sort?”

We want to make sure it’s not a fuel or oxygen leak.  We keep a close eye on it. It sure looks like frost/ice from super-cold skin of the third stage’s forward dome. 

Overmyer gives us the word.  “Seventeen, Houston. You have a Go for T&D.”  Transposition and Docking.

“Okay. A go for T&D.”

Ron says, “OK. We’ll arm the pyros.”   The pyrotechnic charge that will separate us from the top of the Saturn “SLA” adapter.

We hear a loud bang.  I call, “Separation, Houston.”

Now there really is a lot of stuff flying around out there.  “Houston, we’re right in the middle of a snowstorm.”   And I see one of the curved SLA panels tumble away slowly.

Ron, taking it slow to conserve fuel, says, “We’re not there yet. Long ways to go yet.”

I observe, “There goes another SLA panel, Houston, going the other way.”

And you exclaim, “Hey, there’s the booster!”   It comes into view as we slowly swing our nose toward it.

“We’ve got the booster and is she pretty. Challenger’s just sitting in her nest.”

Captain America, taking stock of his ship, notes, “OK, it’s flying pretty good.” 

I tell Overmyer, “I can’t tell you too much, Bob, from the center seat other than Captain America is very intent on getting Challenger at the moment.”

It’s just 6 min. since we separated from the booster.  Ron says, “I’m coming in a little slow, but we’ve got plenty of time.”

You observe, “So far, LM looks very clean. Can’t see anything abnormal from this view yet.”

Ron comments as we inch closer, “That thing is really stable out there.”

And you glimpse the folded Rover attached to the side of Challenger’s box-like descent stage  “Rover looks in good shape, so far.”   The delicate creature seems to have come through the rigors of launch, as has the equally fragile Lunar Module.  “All the antennas look good; thruster quads all look great. I could see all four of them a minute ago.”

Now 13 min. since we separated, getting close.  Ron says, “Okay, about 10 ft. there, Gene.”

Less than a minute later, he says, “All right; in good shape.”  The tip of the three-pronged probe at the tip of the Command Module slides into the funnel-shaped drogue of the LM, right toward a hole in the center.  Three “capture latches.” in the probe’s tip will engage, holding us in a loose docking as vibrations dampen out.

Captain America calls, “About now.”

“Capture, Houston.”

“Roger. We copy.”

Little movement between the two spacecraft.  Ron says, “Rates look pretty good.”  Then “Let’s lock it together.”  That means retract the probe so that the cylindrical docking tunnel makes contact with the LM.  Twelve latches in its rim will fire, firmly sealing the tunnel against the LM.

You call, “OK. You ready?”

Ron replies, “Ready. She’s lined up not bad.”

I say, “OK . . . Mark it. Stand by.”

Ron flips the switch.  “Here she comes.”   It’s only 15 min. since we separated from the third stage.  We hear a ripple bang as the latches engage.  

Ron exclaims, “Ka-chunk. By gosh!”

“Okay, Houston, ripple fire; but we still have number A barber pole.”

An indicator in the middle of our instrument panel displays the status of the latches.  They consist of a small window that shows one of two squares — one is gray, meaning engage; the other indication has black and white striped like a barber pole, indicating the latches are not engages.  Three of the latches have failed to fully connect.  Still nine latches is enough to give us a firm lock.  Later, we will be able to reset the two of the three.  And that’s enough for a solid seal.

Forty-eight minutes after docking, we pull Challenger away from the third stage.  Already we can see the whole Earth.  And I mean whole — it’s a full Earth, which has never been seen from an Apollo spacecraft.  You take a photograph which will become famous of that big, blue marble.


We have our first meal, but eat little.  Our stomachs need time to adjust to weightlessness.  And finally 9 hrs. since launch, go to sleep — or try to, after such a day (or, I should say, night).  We’d been awake for 22 hrs.

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