50 years ago today: “Ten is go”

Apollo10launch

The launch of Apollo 10 on May 18, 1969

 

Synch your straps tight, perform status checks.

We’re going to the moon again.

Again? — every flight is a first flight.

And Apollo 10 is go for the moon.

Not just traveling the path hewn by Apollo 8

Not just combining the flights of Eight and Nine

on only the fourth manned Apollo in seven months,

only the third Saturn V to carry human life,

only the second piloted Lunar Module,

only the second Apollo to the moon

and already in the shadow

of Armstrong, Collins and Aldrin

and the summer ahead.

We’re following a full flight plan for a lunar landing,

exactly the same 31 orbits of the moon,

the same eight-day flight duration,

flying the LM through DOI —

Decent Orbit Initiation —

to within 50,000 feet of the surface.

 

Why go all that way and not land?

The main reason, our LM, the fourth built, is too heavy.

We have enough to do, testing the landing radar for the first time,

reconnoitering and photographing the landing site,

feeling out the effects on our orbital path produced by mascons,

mass concentrations, dense lumps, below the lunar surface

that product a gravity tug

that can pull a spacecraft off course.

Not to mention that the flight control teams needed more experience flying to the moon.

 

If we prove out the flight plan, everything but landing,

then Armstrong, Collins and Aldrin can concentrate on that.

And with the world watching in shadowless July,

their chances of success are much greater.

 

Feel the Saturn V below us come to life, groaning,

moaning fuel and oxidizer flows like blood.

We are counting down toward.

Apollo 10 is go: all systems go.

Two minutes and counting.  Tanks in all three stages now pressurized.

Fifty seconds — power is internal.

We are go for a mission to the moon at this time.

Seventeen seconds — guidance is internal.

T minus ten . . . We have ignition sequence start.

All engines running.

Launch commit.

And liftoff, liftoff at 12:49 a.m. EDT, only seven-tenths of a second late.

And eleven ponderous seconds later, the tower is clear.

“What a ride, what a ride!”  Ten is go.

We’re the leading edge of the wing reaching to July and beyond

The Eagle can’t fly without us flying first.

Second stage ignition and there’s the vibration,

the pogo-stick shaking

worse on this flight because the skin of S-II stage has been metal shaved,

thin and flexing, to save weight.

Inboard engine out on schedule, shut down early as programmed to ease the stress.

Staging, we’re on the S-IV-B stage.  Ten is still go.

We’re go all the way to earth orbit in 11 minutes 45 seconds.  Go for two orbits checking out the spacecraft before the S-IV-B restarts, burns for five minutes and 44 seconds to send us TLI:  Translunar Insertion.

Two orbits and no way of knowing . . .

 

“Ten, you are go for TLI.  The S-IV-B is looking as planned”

Sure it is.

Ignition.  “We’re burning” the stage’s single J-2 engine.

Houston reports, “One minute and everything is looking good.”

“Two minutes and you’re looking good.”

What a kick — we rise out of orbital night into dawn over the Pacific, and exclaim, “What a way to watch a sunrise!”

And then at three minutes, we call, “Everything is looking good.”   And then it isn’t.  Vibration — not the kind we recognize, not pogo — it’s like an aerodynamic flutter.  This thing is shaking apart, screeching as it does.  We keep a hand on the abort handle that would shut down the engine.  But we haven’t come this far to stop.  We’ll continue until planned cutoff or the thing blows.  Whichever comes first.  The vibration is so strong we can barely read our instruments.

Is Ten go?   Our mission commander, Tom Stafford, fakes it, his heart racing, he calmly calls to the ground, “OK, we’re getting a little bit of high-frequency vibrations in the cabin.  Nothing to worry about.”

Five minutes . . . Coming up on SECO, sustainer engine cutoff.

“SECO” and the violent ride is over, and amazingly, our trajectory is spot-on perfect.

 

Later, they will determine that the vibration was due to a defect in a third-stage pressure-relief value.

Showing again why Ten is so vital.

Ten is go, all right.  Ten is going to the moon.

 

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