Fifty years ago: Apollo 17 enters lunar orbit

Destination Taurus-Littrow: A view of the valley Apollo 17 aimed to explore, taken as it passed over the site. The South Massif mountain is at the top left.

*****

“It’s LOI day,” Houston says at wake-up, the day we enter lunar orbit — December 10, 1972.  They’ve let us sleep in an extra half hour, but we’re already awake.  LOI — that’s Lunar Orbit Insertion, the first of two burns we’ll make today.  It will put us into a high elliptical orbit; the second burn will pull us closer.  We’ve got a busy day on hand, although not as busy as tomorrow, landing day, followed in four hours by our first moonwalk.  That is, if LOI goes as smoothly as the outbound journey has.

We’re Eugene Cernan, Ron Evans, and Harrison “Jack” Schmitt.  We’re at the end of an 86 hr. transit to the Moon.  We departed Earth, just after midnight on the morning of December 7, after a launch delay of 2 hr. 40 min.   Flight day 2 actually began on December 7 at 3:30 p.m. EST.  Many of our activities will take place when it is evening and night over North America.  Of course that doesn’t mean anything where we are in the eternal day between Earth and moon.

Always the scientist, Jack, you are fascinated observing weather patterns on Earth and right away gave one of many weather observations to Houston.  “Looks like you’ve got cloud cover from somewhere where then coast bends around Corpus right north into the Great Lakes and completely out into the Atlantic.”

Indeed, Houston joked that you, Jack Schmitt, are “a human weather satellite.”

On Flight Day 3, December 8, we were up at 9:30 a.m. EST.  Two-and-a-half hours later, we performed the only “MCC” — Midcourse correction — a burn of our big engine, the Service Propulsion System engine at the aft of the Service Module of our command ship, “America.”  We fire it just 1.7 sec., increasing our velocity by 10.5 ft. per sec.  That’s all that’s needed to catch us up to where we’d be if we’d launched on time.  It’s as if the launch delay never happened.

You and I entered our Lunar Module, Challenger, just to make sure everything came through the rigors of launch.  We spend two-and-a-half hours checking her over.  The only problem, some poor communications with Houston, turned out to be a ground fault.

We started flight day 4, December 9, with our only mishap, if you can call it that.  We overslept!  You can give Ron Evans the blame.  He was designated to monitor for any calls from Houston — in charge of our alarm clock, if you will, wearing a communication headset as we slept.  Somehow the communications line got switched off.  We sleep for 65 min. through nine wake-up calls and a buzzer!  

When Houston finally rouses us, I gave a drowsy, “Hey, we were asleep.”

“That’s an understatement.” 

I joked to the ground, “Ron was supposed to be on watch but claims he fell asleep after a big party.”

“It was some party last night,” we claimed.

Two hours later, you and I entered the LM for a second time, a kind of dress rehearsal.  We put on our suits, enter Challenger and powered up many of the systems, checking the condition of the batteries and communications.  “It’s looking good onboard.  I think we’re pretty well squared away,” I reported. 

*

We’re ready for the moon, which is about 7 hrs. away when we wake.  The day’s first big task occurs about 5 hrs. before LOI.  We must jettison the panel over the Scientific Instrument Module, the suite of sensors and cameras Ron –“Captain America” — will use to study the moon from orbit.  Capcom Gordon Fullerton calls, “You’re Go to jett the door, and you can do it early, if you wish.

“Okay, Gordo. We’ll do it on – on Ron’s mark . . .”

Ron calls, “SIM door jett 5, 4, 3, 2, 1. . .”  

We hear a loud bang as the pyrotechnics push the door off.  There it goes — I can see it through the hatch window, really rolling along the long axis, doing a revolution about every 5 sec.  “It looks like it was a very clean – clean separation.”

As we are drawn in to the moon, we are treated to a thrilling sight, something no other Apollo experienced.  All other Apollos approached through the moon’s shadow and so were unable to see anything of the surface until after reaching orbit.  Due to the geometry of the high-inclination orbit we will enter, we fly out of the shadow.  And there it is — a blade-thin crescent moon, 10,000 mi. away when it appears.  An epic view, difficult to comprehend in its immensity, as it steadily grows in size.

“I’ll tell you, when you get out here, it’s a big mamou.”  That’s just about all I can say!

Details grow as we accelerate toward the moon, pulled in by it’s gravity.   When still 5,700 mi. away, we’re amazed as the sun illuminates the high peaks and craters at the limb. 

And with less than 2 hrs. to go, we gain the sensation than we’re falling right into the moon.  “Boy, it’s big.  We’re coming right down on top of it,” I tell Capcom Gordon Fullerton.

You joke, “Gordy, we’re considering putting the window covers up.”

“You’re chickens, huh?”

The moon takes on three dimensions.  To the point that we can feel the bulk of the dark body below the thin sunlit swath.

. . . About hour to go.  “The limb has much more three-dimensional relief now. Towards us, you can – you can get the feeling that the horizon – the lighted portion of the horizon definitely does flow in our direction.”   It’s spectacular!

We maneuver to LOI attitude, which brings the Earth over the top of the LM, our SPS engine now leading the way, in position for the braking maneuver.   We’re 40 min. from LOI.

Ten minutes later, Fullerton gives us the word, “Apollo 17, Houston. If – if you three are interested in sticking around awhile, you have our Go for LOI.”

“Roger, Houston. Understand. America is Go for LOI. And let it be known that the crew of America is Go for LOI.”

All eyes on the instruments, on the computer that will command the big engine.  We’re in the hands of Captain America.  Ron is in the left seat, in charge, sets us up for the burn, watches over the engine,   Can you believe he’s humming?!  You know he’s in his element when he hums.

Fullerton calls, “Okay, Gene. About 1 Minute left until LOS. You have our wishes for a good burn.”

“Thank you, sir. We shall have one.”

LOS, loss of signal, communications blocked by the moon.  As with every flight, we fire the engine when behind the moon.  We’re about 10 min. from the engine burn.  

Ron is humming and the engine is humming — here it comes, ignition at 2:47 p.m. EST.  We endure the suspense of a 6.5-min. burn.  We scan the instrument panels, urge the engine on, second upon second.  But not too many — if it fires just a few seconds too long, we’ll crash into that big mamou.

Shutdown on time, after a burn of precisely 6 min. 33.16 sec.  Here come the vital numbers:  Our orbit is 194 by 60.6 mi.  On the money.  We’re here, babe.  Now wait for that earth to appear on the horizon.  There she come, and with it communications with Earth, 35 min. after the burn.

We hear Gordy Fullerton’s distant voice:  “Hello, America. How do you read Houston? Over.”

I reply, “America – Houston, this is America. You can breathe easier. America has arrived on station for the challenge ahead.”

At the high point of our orbit, we pass over the landing site, which is still in darkness.  It with be bathed in the long shadows of post-dawn when we land in 24 hrs.

On our first orbit, you describe the surface, the terraced walls of Copernicus — they show up clearly in the brightness of Earthshine.   Beyond it, you see something — a flash? — over the crater Grimaldi.  “It was a bright little flash.  There was just a pinprick of light.”  It could have been a small meteoroid striking the surface, you speculate.

After two orbits, at 7:04 p.m., we fire the SPS engine again, the first descent orbit burn, just a 22 sec. blip that puts enter a 68 by 16.5 mi. orbit.  Ah, I’ve been this low before — on Apollo 10 in 1969 when we descended to within 10 miles of the surface in the dress rehearsal for the first landing.  Echoing my words then, I say, “We is getting back down among ’em where us plain folks belong.”  

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