50 years ago: The wild gyration

Snoopy

Fifty years ago today, May 22, 1969:

Snoopy swings low over the moon

 

 

Go/no go?

This is the big day, our second day in lunar orbit.

This is our primary test objective — cut our Lunar Module

Code named Snoopy

from the command ship, Charlie Brown.

Playful names, but appropriate — we’re going to snoop out

the primary landing site for the next mission, Apollo 11,

which is rolling out to the pad on the this very day.

Go/no go?

We’ve got trouble, on our last pass of the nearside

before undocking on the far side.   The Lunar Module

is bending out of line with the Command Module,

probably gummed up by loose insulation, like a snowstorm,

discovered after launch in the tunnel between the two craft.

Go/no go?

We’re 3.5 degrees out of line.  Houston tells us that if it hits 6 degrees,

we cannot undock for fear of shearing off the docking pins.

Approaching LOS, loss of signal as we go behind the moon.

Houston radios that we’re looking good — as long as Snoopy doesn’t slip any further.

It’ll be our call, on our own behind the moon.

Go/no go?

It’s 3.5 degrees . . . and holding.

Release the latches.  We are undocked and ready for a near encounter with the lunar surface.  Stand by for the next orbit.

 

****

 

OK, babe, it’s DOI time.

That’s Descent Orbit Initiation, the burn

to send us down toward the surface, the low point

not much more than ten miles altitude, the place

from which the next flight will descent to the surface.

The orbit in which will will stay, swinging low

over the landing site in the Sea of Tranquility,

observing the landmarks of approach, the surface conditions,

lighting conditions, testing the landing radar

before our elliptical orbit flings us high again.

Like most major burns, DOI occurs on the far side,

out of radio range.

LOS.  We are on our own.

Descent engine on, 10 percent throttle.  We are burning, a 27.4 second burn.

If we burn two seconds too long, we will crash onto the front of the moon.

After 15 seconds, go to 40 percent throttle.

Cut off.  Cut off on time.  We are go.  In one hour we will be low over the landing site.

 

****

 

It doesn’t take long, babe.  We can tell we’re descending fast.  The curve of the horizon flattens out.   That mountain range up ahead?  Those aren’t mountains; it’s the rim of a crater.  We’re that low already.

Coming around to the front side now.  Charlie Brown, out ahead of us in high orbit, comes into radio range first.  He tells the world, They’re rambling down among the boulders.

And we are.  Look at the size of those things.  The size of buildings.

We coming into radio range and report, We is down among ’em.   . . . We just saw earth rise and its got to be magnificent.

It looks like the landing radar is doing real good.

Four minutes to the low point, coming over the last mountains, over Apollo ridge and into the Sea of Tranquility, 270 miles from the landing site.  We pass over the crater Maskelyne.  It has huge boulders around it, inside and falling outside.

We’re into the Sea of Tranquility.   Here it comes.   Pitchover — pitching down for a better view.

We’re right there!  We’re right over the landing site.  There are plenty of holes there — with deep shadows in the early lunar morning.  The surface is actually smooth, like wet clay.

Man, I’ll tell you, we are low.  We are close, babe.   We are 47,400 ft. above the surface.

Gaining altitude, overtaking lunar sunrise, heading toward the dark beyond.   Prepare for another burn of the descent engine, this to pull us ahead of the command ship and set up rendezvous after one more low pass.  We’re burning . . .  Throttling up.

After 39.95 seconds, shutdown.  We report to John Young flying solo in Charlie Brown, The burn is good, John.

 

****

 

Coming around to our second low point, 11 miles above the surface.  Our focus is on our instruments, a simulation of a lunar take-off.  We’ll cut free of the box-like descent stage with its four legs, fire the ascent engine to mimic ascent orbit insertion.  For this, we’ll use the back-up abort guidance system, AGS.

Switching to AGS . . . or so with think.  Snoopy goes into a tumble 60 degrees a second, rolling at the same time, the lunar surface wobbling in and out of the windows — as if we’re going to head into it.

There’s no time — we’ve got to set up to fire the engine in ten minutes.

There’s no time — but Tom Stafford is fast than time.  In just eight seconds, he cuts loose the dead weight of the descent stage, takes manual control, stabilizes Snoopy.

Son of a bitch — what the hell happened?

It would forever be known as the “wild gyration.”  What happened was a wrong switch setting, that sent guidance into a mode where it automatically searches for the command ship.

We’re go, however.  With just seconds to spare, we’re go for the burn.

Engine on ascent . . .

****

Snoopy and Charlie Brown are hugging each other.  After a solo flight of 8 hrs. 10 min. 5 sec., We are docked.  Fifty years ago today, the road was open for a moon landing in July.

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