50 years ago: Launch of Apollo 15, the first great expedition to the moon

Saturn #510 leans away from the launch tower.


            Dawn, July 26, 1971: Look at it out there, Saturn V #510. Our Saturn V.  Looks just like the nine that have preceded.  We know better.  If we can pull this off, it’s gonna give a new face to the Apollo program, this Apollo 15, this first extended “J Series” mission, a true scientific expedition to the moon.   If we can pull this off.   The “we” is you and me and our man in the command module, Al Worden.   

            Dawn, July 26, 1971: With a last wave, we leave for the pad. It’s time to start finding out if we can pull this off.  If we can make a difficult landing, coming in over 15,000-ft.-tall lunar mountains, descending steep, an angle of 26 degrees, twice that of previous landings.  If our maps are correct — we’re headed north of equatorial landing zone mapped in detail for the first landings.  Our site has only been mapped in medium-resolution photos made by the Lunar Orbiters; our site a spit of lunar mare boxed in on three sides by mountains.  And on the fourth?  Hadley Rille, a sinuous gorge, a mile across and 1,200 ft. deep, likely a collapsed lava tube, one of our many goals to probe its origins.   

            If we can pull all this off, we’ll spend nearly 67 hours on the moon, twice the time of Apollo 14. We’ll made three moonwalks — or rather rides — aboard the new Lunar Rover.  The rover, if it doesn’t fail in the lunar dust, will extend our exploration range as far as three miles from our lander.  We’ll work on the surface for up to 7 hrs. each day.  In all, we’ll drive about 20 miles, collect more geological samples than all the previous missions combined.  

            Indeed, we are like three missions in one.  If we can pull it off.  We’ll explore an area the size of Manhattan — compared to about half of Central Park covered by Apollo 14.  In addition to Hadley Rille, we’ll sample mare terrain to compare with Apollos 11 and 12 which landed on these lava “seas,” ride up the slopes of the Apennine Front seeking to sample the original lunar crust and seek the youngest rocks in an area we call the North Complex that looks volcanic in origin.

            To pull it off, all our capacities and capabilities have been beefed up and stretched out.  We’re pushing Apollo far beyond the systems designed to land on the moon by the end of the sixties.  

             The command ship, Endeavour, has been transformed into an orbiting science base.  In the cylindrical Service Module, equipment has been moved to free up one of the pie-shaped bays in which now houses the Scientific Instrument Module containing a suite of eight instruments, including two sophisticated camera systems to map and make high-resolution photos of the surface.  Those camera will produce more than a mile of film which then must be transferred into the Command Module, the only section of the spacecraft that returns to Earth.  Al Worden will make the world’s first spacewalk in deep space, 196,000 miles from Earth on the homeward journey, to bring home the film cassettes. 

            The weight of the science payload aboard the Command/Service Modules has increased from 250 lbs. to 1,050 lbs.  And the Service module holds fifty percent more cryogenic hydrogen and oxygen for the electricity-producing fuel cells. 

            The Lunar Module, named Falcon, looks like previous ones, if you fail to notice the neat package, the folded Lunar Rover, slung against the left side of the box-shaped descent stage.  Our LM weighs about a ton more than older versions.  A fifth battery added in that descent stage, and additional tank of breathing oxygen.  The height of propellant tanks have been lengthened, yielding a 6.3 percent increase in fuel for landing.  In addition, the Descent Propulsion System (DPS) combustion chamber has modified and the skirt of the engine bell extended.  All this allows us to carry the Rover, weighing 455 lbs. on Earth, and more than double the weight of science instruments, from 510 lb. to about 1,200 lb.

            To compliment the spacecraft capabilities, we will wear improved spacesuits, with new bellow-like joints for increased range of movement.  We’ll be able to actually bend over and pick up items off the surface. We carry a larger bag of drinking water, accessed through a straw — and even a fruit bar in the helmet we can bite off. The backpacks carrying an increased supply of oxygen and coolant water, allowing the longer moonwalks.  And these suits are designed to be taken off in the confines of the LM cabin.  That’s very important as we’ll be the first not just to briefly visit but live on the moon. 

            All these changes mean Apollo 15 will be the heaviest payload ever placed into earth orbit — 107,500 lbs. — beyond the capability of previous Saturn Vs.  And so our beast has been modified on the basis of experience. Four of the eight first-stage retro-rockets which ensure the spent stage is pushed down and away from us, are deemed unnecessary.  Four will do the job.  Other small rockets to settle to propellants in the tanks have been removed, found not to be needed.   The weight savings equates to increased payload.  And the first-stage F-1 engines have been modified to accept a slightly higher propellant flow — more kick — and propellant margins at cutoff will be less.  

            Yes, margins will be tight.  Our trajectory also has been reshaped for more performance, putting us in a lower initial parking orbit of 105 mi. altitude.  And our TLI — Translunar Insertion — burn by the third stage will push us directly into our target trajectory, rather than going into the safer free-return trajectory initially then adjusting course with our spacecraft’s SPS engine, thus saving fuel for extensive maneuvers during our six days in lunar orbit.

            An ambitious mission? You bet.  It’s like beginning a brand new space program.  T-zero, launch is set for 9:34 a.m. EDT.  It’s been the smoothest count ever.  Even the weather has cooperated, humid Florida morning with just a few scattered clouds.

            With 2 hr. 40 min. until launch we’re strapped elbow-to-elbow in the Command Module confines Not much to do, damn near could doze off.  Twenty minutes before launch the swing arm pulls the white room back and sunlight through the hatch window floods the cabin — like stage light signally the play is about to begin.   Everything is proceeding super-smooth, even ahead of schedule.    

            Three minutes to go, Paul Donnelly, the launch manager, wishes us, “Godspeed.”   T minus 50 sec., we go on internal power.  In the cabin, we make final checks of the guidance system.  We’re go.

            Coming up on engine start, the five F-1 engines at the rocket’s base 363 ft. below us.  We hear the wine of fuel turbines spinning up. Hear valves groan open, fuel gurgle down the lines.   Ignition — just a muffled, faraway roar.  Ignition and liftoff.  Feel the motion, the low-amplitude, lateral vibration.  Always tense we might collide with the launch tower.  We feel the engines swivel, leaning the stack away from the tower for a bit of added clearance.  It seems forever until we tilt and slide by it — actually just 11 – 12 seconds after liftoff, we hear, “Tower clear.”  

            And just 1 min. 20 sec. after launch we reach Max-Q, the maximum air pressure on the vehicle, imparting stronger forces on our tricked-out bird than with past vehicles. Noisy through Max-Q, but smooth, forces building to 4 Gs.  Very smooth. That is, until staging.

            After 2 min. 40 sec., first stage cutoff, and — pow — we’re thrown forward as if hurtling through the instrument panel.  After a breath, the second-stage engines ignite and — wham — we’re tossed back into our couches.  Just as expected.

            And fly on smoothly again, unaware of how close we came.  Literally.  The thrust from the first stage didn’t tail away as fast as predicted, and removing four retro-rockets from the first stage cut margins a wee bit too much.  Before the second stage could ignite, we almost collided.  That’s the risk whenever you change anything.

            The capcom, veteran astronaut Dick Gordon, calls, “Good thrust of the S-2” stage. The second stage provides a comfortable ride.

            “Apollo 15, Houston. Five minutes.  Everything looks nominal.”

            We reply, “Everything looks nominal up here.”

            The second stage shutdown, not as violent as the first separation, and we’re riding the single engine of the third stage, the trusty S-IVB, 9 min. 10 sec. since launch.

            “You have good thrust on the S-IVB”

            Approaching shutdown, Gordon calls, “Everything is looking perfect.”  And there it is — shutdown of the S-IVB, 11 min. 34 sec. since launch.   “Good show,” we call, “That was a smooth ride all the way.”  And look at that — the moon shining through the window.   

            We check all our systems during our brief stay — less than two orbits — and receive the good word: Go for TLI.   The S-IVB reignites and to kick us out of Earth orbit in a burn of nearly six minutes, the start of a 72-hr. transit to the moon.  The engine is “hot” — a bit higher thrust than nominal reaches translunar speed four seconds earlier than predicted.  

            Our long day is not over yet.  About a half hour after TLI, we pull free of the third stage for the now familiar transposition and docking, where we pull our Falconfrom its “garage” atop the stage.  Only such things are never routine, on the previous flight they had trouble docking. Al Worden does the piloting, tells Houston, “We’re almost there.”

            With a slight bump, our probe slips into the funnel-like drogue atop the LM.  Latches engage.  “We have capture.”   And hard dock.    

            And 40 min. after TLI, we’re already 4,000 mi. from Earth.   On our way — maybe.  We have a problem, already.  A square-shaped little event light.  Glowing red. Holy crap — it’s the “Delta-V Thrust A” switch.  It’s showing that our main engine is preparing to fire.  We safe the circuit, but what’s going on?  

            Recycle the electronics — the light goes out.  But when we tap the panel, it flickers on.  Obviously a short somewhere in the system.  

            We have two redundant circuits to fire the engine, “A” and “B.”   We always maintain a backup, can’t proceed with just one circuit operable.  That’s a firm mission rule.  So if “A” has failed, our mission to the moon is a no-go.

            Houston quickly determines the short could be located in three places.  If at the panel, we can bypass it, usual manual control on controller A.  Same at a second point, a bit further in the system.  Ah — but the third point, a failure there means the controller A cannot be used.  And our mission exploration of the moon will have ended before it even began.  We’ll head on home, empty handed, our magnificent Rover destine to burn up in the atmosphere.

            Houston sounds reassuring.  “The short seems to be, and all of us down here are convinced . . .  it’s either in that switch or physically very near that switch.”  But we must prove we can use controller A.  Houston devises a brief correction burn for the morning to prove our bypass procedures work. 

            Until then, we carry on as normal.  We end the long day at 12:14 a.m., Eastern time, the dawn of July 27, fourteen-and-a-half hours since launch.  We’re already 75,000 mi. from Earth.  But are we going anywhere? 

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