***

“Good morning, Apollo 16,” the capcom calls.  It’s April 27, 1972.

Most of our mission, step by step, is behind us.  Yet the most vital step is just ahead.  It’s splashdown day.   And there’s still plenty of room for something to go wrong — just ask the Apollo 15 crew, who had one parachute collapse in the final moments.  The corrosive fuel they jettisoned ate through the chute’s riser lines.  Turns outs, in certain conditions the propellant can get caught in a vortex at the apex of the Command Module and hit the parachute lines.  We will not dump the fuel, even though should it leak on impact, it is highly toxic.   Such are the risk tradeoffs of space flight.

Yes, there’s still plenty that can go wrong.  We encounter a glitch as we configure for reentry.  A little light comes on the instrument panel indicating a malfunction in the inertial stabilization subsystem of the autopilot that is supposed to guide us through the narrow reentry corridor.  We must thread a tiny 2-degree window on atmospheric entry.  Too high, and we’ll skip off the atmosphere like stone.  Too low, and we’ll burn up.  When we rap on the panel, the light goes out, indicating a short in it and no problem with the subsystem itself.  Still, Houston makes sure we’re ready to fly a manual reentry, as T.K. Mattingly is trained to do, if we should have to.  

The pull of the Earth’s gravity grows exponentially as we approach.  About 5 hrs. before splash, we’re still 46,000 mi. from Earth, traveling at a leisurely 6,680 mph.   Just two-and-a-half hours later, we’re 29,000 mi. away and have accelerated to 8,397 mph.   Amazingly when we hit the atmosphere a couple hours later, we’ll be speeding at 24,700 mph.  And we will splashdown just 13 min. after that, hitting the water at 20 mph.  

Events begin to occur rapidly in the final half hour.  It’s now 2:15 p.m. EST.  We call, “OK, we’re a minute-and-a-half from CM/SM sep.”  That’s the jettisoning of our cylindrical Service Module with its big engine that did its job after all.  

“Separation, Houston.”  Just our cone-shaped Command Module remains.  We maneuver to entry attitude.  We’re right in the middle of the reentry corridor.  Our splashdown point is 1,500 mi. south of Hawaii and 215 mi. southeast of Christmas Island.  Our recovery carrier is the USS Ticonderoga. 

Capcom Henry Hartsfield radios, “Apollo 16, you’re still looking good.”   

At 2:31 p.m. EST, just 15 min. after jettisoning the Service Module and at an altitude of 400,000 ft., we hit Entry Interface, the first touches of atmosphere.  A faint glow licks the windows at first and build rapidly in intensity.  Radio blackout commences as the fires of reentry wrap a fist around the capsule and stream out behind us.  We’re pushed into our couches with the force of 7 G’s.  

The capsules offset center of gravity provides a bit of lift which allows the computer to fly upwards a bit to reduce the G forces and heating.  Then we roll 180 degrees and dive back into the depths of the atmosphere.  We watch the clock — the maneuvers come right on the predicted time, proof that we’re right on course.  And through the flames, we see the blue of the ocean below us.  

We emerge from the fires, hear Houston calling, “Apollo 16, Houston.”

“Roger, loud and clear.”

“How’s it going?”

“Everything looks good,” we report.

It’s parachute time.  At 23,000 ft., the apex cover at the tip is blown away and mortars deploy two drogue chutes, each 16.5 ft. in diameter.  Man, we’re bouncing around on those small drogues, whipping back and forth.  And these are the chutes that are supposed to stabilize us.

At 10,000 ft., the drogues are jettisoned, and we feel a momentary drop.  Followed immediately by deployment of the three main chutes, with 83.5-ft. diameters, reefed in at first to lessen the shock.  Then they blossom fully.  We’re flowing through clear skies, calm waters below.  Are we home free?

Bam!  Our Command Module, weighing 11,995 lbs., hits the water, hits hard.  Musta hit flat to the surface, a belly slam.  Wow.  The spacecraft flips over, nose into the water — Stable 2 , the position is called.    It’s 2:45 p.m EDT; our flight of 265 hrs. 51 min. 5 sec. is over.  

We inflate three airbags to right the capsule — one does not fully inflate, yet the others are enough to turn us over on our back.  We report that we’re in outstanding shape.  And we are.  We’ve done it.  It takes about a half hour before we’re hoisted into the recovery helicopter.  Just 37 min. after splash, we take our first Earthly steps onto the deck of the Ticonderoga.

We are John Young, Cdr., T.K. “Ken” Mattingly, Command Module Pilot, and Charlie Duke, Lunar Module Pilot.

On deck, we give a little speech in which we say, “There are secrets in that vehicle now.  There’s some basic knowledge and understanding in that vehicle right now.”

And that it true.  No mission, I believe, changed the image of the moon more than Apollo 16.  Before our flight, the geologists, thinking the formations on the moon mirrored those on Earth, saw Descartes and Cayley as volcanic flows.  Instead we found four types of breccias, rocks formed of material fused during the shock of meteor impacts.  No volcanoes.  And T.K., the first Apollo pilot to carry binoculars, could see it from orbit — that the Descartes region appeared no different than other areas of the moon sculpted by impacts.

That shows how little we really knew.  And we have just one more lunar mission to learn once again how little we know.