50 years ago: Turning toward home

Jim Lovell in the Lunar Module, Aquarius.

*

            We enter April 14, earth time.  For us aboard Apollo 13, days and dates have ceased.  There is only the track of our spacecraft, still outbound to the Moon, the march of GET — Ground Elapse Time since launch — strung with milestones to draw us back to earth.  Step by step. The first step, returning the spacecraft to the free-return trajectory that will slingshot us around the moon and on course for Earth.  

            We prepare for that burn, that will use the Lunar Module’s Descent Propulsion System, slotted to take place about 5 hrs. 25 min. after the accident.  For two hours, we struggle to control the spacecraft’s attitude, which keeps jumping around.   Are we still venting something?   And it’s more than that.  We’ve never practiced flying our LM, Aquarius, with the heavy command ship attached, it throws of the center of gravity, meaning the stack pivots in odd directions. As our Commander, Jim Lovell says, it’s like learning to fly all over again.  

            Yet he does, and wrestles the spacecraft in position for the short burn, 30.7 seconds.   Ignition, at 10 percent throttle for 10 seconds. Then 40 percent for 21 seconds. Shutdown, on time.  Perfect, no residual errors.  We’re now on course to loop the moon and splashdown in the Indian Ocean after 74 hours.

            The LM is designed to support two men for 45 hours.  Can it sustain three for three days?   Oxygen isn’t a problem — it has enough for perhaps eight days.  Will the batteries hold?  With an extreme power-down, it appears so.  Water is the problem — not just for drinking, it is used as coolant for the LM systems.  Water looks to be short.

            However, once we swing around the moon, we can do a speed-up burn to return us sooner. Cutting loose the dead Service Module and burning all our DPS fuel will kick us home fast.  But that’s dangerous, leaving no fuel for course corrections and exposing the Command Module’s heat shield to the cold of space.  Controller give us a less severe plan.  At PC + 2 (Pericynthian, closest approach to the moon, plus two hours) a burn would speed us by 600 mph and bring us home in 63 hours. And land us in the prime splashdown area in the Pacific Ocean, 600 miles southeast of Samoa.  The burn will last must longer than the previous one, 4 min. 24 sec. 

            First, we swing around the moon at an altitude of 158 miles, instead of the 70 miles when a spacecraft enters orbit.  This gives us a record — we’ll have traveled the farthest from Earth of any humans. And it gives up a unique view of the lunar surface.  Despite the emergency, despite the PC+2 burn just ahead, we have our cameras out, our one opportunity to look at the moon.

            We report, “We are in the shadow of the moon now.  The sun is just about to set . . . and the stars are coming out.”

            We pass out of radio contact around the back of the moon for 25 minutes, our unique view the rugged far side continues as we emerge, cameras clicking away.

            Our veteran, Jim Lovell, points out, “Hey, if you want to use the 250 [millimeter lens], there’s a beautiful shot of Tsiolkovsky which we very seldom see.”

            We’re pulling away now, and finally Lovell says, “Let’s get the cameras squared away. Let’s get set to burn.  We got one chance now.”

            With all the bright points of debris floating around us, we can’t make navigation sightings on stars. Instead, we verify our attitude by the position of the sun.  On earth, it’s approaching 9:41 p.m. EST., April 14.

            Capcom:  “Jim, you are go for the burn.”

            Lovell: “Roger.  I understand.”

            Lovell: “We’re burning, 40 percent [throttle].”

            Capcom: “Houston copies.”

            Lovell: “One-hundred percent.”

            Capcom: “Roger.”

            Silence as the seconds melt into minutes, the engine purring along nicely.  Four minutes and still go . . .  “Shutdown.”

            “Roger, Shutdown. . . . Good burn, Aquarius.”

            And right away we say, “And now we want to power down as soon as possible.”  That means we turn off the power-hungry guidance and navigation system.  If we have to make an course corrections, we won’t have use of it.  Let’s hope our course stays true.

            The capcom radios, “Everybody down here is 100 percent optimistic.  Looks like we’re on the upside of the whole thing now.”

            Yes, with a long, long way yet to go.

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