July 29: Apollo 15 enters orbit

The Apollo 15 command ship, showing the open Scientific Instrument Module


            Are you ready?  Are you ready, my friend, for the moon? We’re almost there — let’s kick the door open on this thing.  Literally. It’s July 29, 1971.  We’re 78 hrs. into the flight of our Apollo 15, about 1.5 hrs. from Lunar Orbit Insertion.  It’s time to jettison the panel over the Scientific Instrument Module (SIM) behind us in one bay of the Service Module, unveiling eight instruments which will study the moon from orbit, map twenty percent of its surface in detail as never before.  Jettisoning the door is like firing a starter’s pistol on our complex mission of scientific exploration.

            We’ve made it this far, three days out from Earth.  We made it despite that red warning light that came on as we left low orbit, indicating our main engine, the one that in one-and-a-half hours will fire to place us into lunar orbit, was malfunctioning.   The morning after launch, we tested it — by isolating the circuit, on manual control, set to fire the engine for the briefest of durations — an 85-hundredths of a second.

            “OK, here we go.”

            The engine blipped; the numbers looked good.  Capcom Joe Allen called, “That burn was exactly what we wanted to see.  We’ll proceed with a normal mission.”

            “Let’s go to Hadley!”  That’s the 11,000-ft.-tall mountain called Hadley-delta in The Apennine range at the edge of Mare Imbrium.

            Outbound, we experienced one other moment when the mission appeared about to go under water — literally.  During a routine task.  We were 61 hrs. into the flight, adding chlorine to our drinking water supply, and the damn system began leaking around the connection.  A ball of water ballooning around it, the way fluids act in weightlessness, forming a sphere from surface tension.  If the leak was coming from a broken water line, that was it for the mission.  Even if not, we were leaking a serious amount of water.  We tell Houston:  Quick come up with something.  They ask how many drips per minute it’s producing.  Water doesn’t drip in weightlessness!

            Give them credit — they came up with a solution within minutes, having seen the same problem crop up on the pad.  We tightened the connection and that ends that.  Except for all the clean up.  We soaked up the water with towels.  What to do with the towels?  We hung them to dry on the seat struts.  “Looks like somebody’s laundry.”  Not exactly a sporty image of spaceflight.

            During our transit to the moon, we’ve twice checked out our Lunar Module, Falcon.  The only anomaly apparent the first time we enter — glass floating around.  The outer pane over a meter which will show our distance and descent rate (and closing rate during rendezvous) somehow shattered.  An inner pane still protects the meter and it still works.  But that floating glass, which could pose a danger, was a pain to clean up.  We snagged the bigger pieces onto duct tape.  Vacuumed up as much of the rest as possible.  Seems like we’re perpetually vacuuming it up.  Again, not quite the image of moon travel.

            Now — 11:35 a.m. EDT back on Earth, it’s time to do something more than take in the laundry. We fire the bolts that kick away the science-bay door, rid of it before entering orbit.  We feel a slight bump as it goes, enough to signal that we’re ready for science.

            Welcome to the moon, which dresses itself a thin crescent wrapped around a dark bulk.  Huge, gaining personality.   At 4:05 p.m. Eastern, it’s LOI time — Lunar Orbit Insertion — Al Worden in command of the burn behind the moon, a big burn of 6 min. 32 sec. — the SPS engine very smooth.  Absolutely perfect — no residual errors in our orbit, an elliptical path 196 by 66 mi. that we will trace for two orbits.  We break into sunlight, above a farside choked with craters, each a creature of full fury and dimension.

            After a half hour on the backside, we come back into radio range and call, “Hello, Houston. Endeavour‘s on station.”

            Four hours later, behind the moon, we fire the engine again to lower us into the staging orbit for landing tomorrow.  As we come around, we call, “The Falconis on its perch.”  

            We fly as low as 56,000 ft. above the surface, the mountains rising almost within reach, peeking over the horizon as we approach them.  We tell Houston, “I’ll tell you.  It’s really spectacular when you can see the central peak coming up over the horizon before you see the rim” of a crater.

            No words to describe skimming above the wide curving expanses, features rising up, rolling by, a tumble of craters, crags and mountains, colors shifting in sunlight from white to gray to tan and brown.   “Absolutely overwhelming.”   

            “Oh, this is really profound.” 

            We’re so low, we can see individual boulders.  It looks like we’re barely passing over some of the mountains, like they’re going to reach up to grab us.  We joke, “We’ve got our eyes closed; we’re pulling our feet up.” 

            Look at it all — observe with our geologist eyes.  The moon a planet — that’s it, the moon has become a planet to us, filled with a variety of forms, formations and mysteries.  We tell Houston, “I don’t think we’ll have any trouble finding new things for you in six days.”  

            On the third orbit, we begin waking up the instruments in the SIM bay, Al Worden’s workshop.  He’s got a load of instruments and tasks, as much as we will on the surface.  He’s got, in that bay, a 24-in. panorama camera — actually an obsolete, declassified reconnaissance one — for high-resolution photos of the surface. He’s got a 3-in. mapping camera that is tied to a stellar camera to determine the precise location of the features photographed in strips.  He’s got a laser altimeter that will correlate height data with the mapping camera. He’s got a mass spectrometer that will measure the very tenuous lunar atmosphere.  He’s got three more spectrometers that will measure the composition of the surface and the solar interaction with it.  And, before we leave orbit, he will release a tiny subsatellite, weighting 78.5 lbs., that will spend a year measuring the moon’s magnetic and gravity fields.

            It’s time to get to work. Tomorrow, you and I land in the mountains of the moon.   

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