A movie of the hair-raising Apollo 13 Moon-shot is premiered next week. Commander
Jim Lovell tells of the most daring space rescue ever If we missed, we were at risk of sailing on in Sun orbit, for ever
A SHORT, muffled blast echoed through the spacecraft. It rocked for a few brief seconds, then settled down and quiet again prevailed. I could tell by Fred Haise's expression that he didn't know what had happened. A quick glance over to Jack Swigert told me the same. Jack's eyes were as wide as saucers.
A red light flashed on our warning panel: low voltage on Main B electrical bus. Then two
more lights blinked on: two of our three fuel cells had just died - our major source of
electrical energy. One fuel cell would take us around the Moon and back home, but without all three operating, our mission rules prevented a lunar landing. Endless months of training, my second flight to the Moon, and now I can't land? I scanned gauges that monitored our oxygen tanks behind us in the service module: one read zero, and I could actually see the needle going down in the second one.
I looked out the side window. The gaseous substance I saw escaping at a high speed from the rear of the spacecraft confirmed my suspicions. Soon we would be completely out of oxygen, and our third and last fuel cell would die, as would all our environmental control and electrical power.
Inside Odyssey we did have a small battery and oxygen tank to use after we jettisoned our service module. But they were designed to last only five hours during the final plunge into Earth's atmosphere. At the time of the explosion, we were 90 hours away from home: 200,000 miles from Earth and heading away.
We began our four-day struggle to return to Earth and to stay alive. Our situation in the
command module became critical. Houston called: "We figure you've got about 15 minutes' worth of power left in the command module, so we want you to start getting over in the lunar module and getting some power on that."
When that call came through, Fred and I were already threading our way through the tunnel into the lunar module Aquarius. We knew our only chance for survival was to convert Aquarius into a lifeboat and use its systems to get home.
Our first task was time critical. We had to transfer the alignment from Odyssey's inertial guidance system to the guidance system in Aquarius before the power failed. The guidance system, coupled with the computers, gave us spacecraft attitude, position and velocity information, that was essential for performing the necessary course corrections. We completed the transfer just before Odyssey's power died.
The course we were on would take us around the Moon - but not back to Earth. We had to
get back on a free return trajectory. All systems were turned on in Aquarius, and at 61 hours and 30 minutes since we left Cape Kennedy, we fired Aquarius's descent engine for about 30 seconds.
Battery power in the lunar module was the problem. Aquarius was designed to last just 45 hours, half of what we needed. The obvious solution was to speed up our return. Our present course could put us in the Indian Ocean and required a total mission time of approximately 152 hours - too long.
Mission control had an idea. We would light Aquarius's descent engine a second time, about two hours after we passed the far side of the Moon. It would have to be a long burn, but we might just increase our velocity enough to make a successful re-entry prior to running out of oxygen and other consumables. Besides, this manoeuvre would put our landing near our recovery force in the Pacific Ocean.
Houston started to develop the procedures and our back-up crew was called in to test the plan in the simulator. We didn't have much time - the Moon was less than 40,000 miles away, we were rapidly accelerating towards it and, upon arrival, the lunar gravity would quickly sling us around to the far side and out of communication with Earth.
On Tuesday night at 19.21 hours, Apollo 13 swung behind the Moon, lost contact with Earth and passed 164 nautical miles above the lunar surface.I noticed that both Fred and Jack were not paying too much attention to the upcoming critical manoeuvre. Instead, they had cameras in their hands.
"Gentlemen, what are your intentions?"
"We want to get some pictures of the far side of the Moon."
"If we don't get home, you won't get them developed."
We finally got our act together and, at the correct time, began the four-and-a-half minute burn. Once back in contact with Houston, mission control closely monitored us.
We shut down on time. It looked good. Houston confirmed it.
We called: "Now we want to power down as soon as possible."
"We have a procedure ready," Houston replied.
Powering down meant everything. The only items left operating were the radio to talk to Earth and a fan to circulate the atmosphere in the spacecraft. We were flying by the seat of our pants. But again we ran into problems.
The altitude control rockets were never designed to control the altitude of the lunar module with a dead 60,000 lb command and service module attached to it, so, without
the autopilot, I had to fly it manually. Pushing forward on the controller did not result in a pitch-down motion but some wild gyration in another direction. I had to learn to 'fly' all over again.
We had lost our internal source of heat and were radiating more heat into space than we
were getting from the sun. To try to heat up our spacecraft, we manually rotated it perpendicular to the sun, a manoeuvre we called the "barbecue mode".
Yet all the metal fixtures felt cold and clammy, as moisture formed on everything.
Even the windows began to frost over.
After our first manoeuvre, our trajectory was now on a free return course home and within the narrow 2O pie-shaped entry corridor. We would enter the atmosphere at over 24,000mph and the entry angle could not be less than 5.5O or greater than 7.5O with respect to Earth's horizon. If we came in at too shallow an angle, we would skip off the atmosphere like a stone off water. If we came in too steeply, we would burn up in seconds like a meteor.
Houston knew exactly where we were headed - and sent an ominous message. Perhaps we were still venting gas and it applied force on the spacecraft. Or maybe our guidance system alignment had been a little off. Whatever happened, we were no longer on the free return course. If we continued on the present trajectory, we would miss Earth's atmosphere by 99 miles and sail on in Sun orbit - for ever.
"Great," I said. "Just great. What are we going to do? We powered down our guidance system so we've lost any accurate altitude reference. Our computer is dead. The autopilot inoperative. Why, even the burst disk in the super critical helium tank, that pressurises the descent engine fuel tanks, is about to blow. And when that happens, we will lose our descent engine." Mission control radioed that they thought they had a solution, but we would have to work fast.
They reminded me of the emergency procedures we had tucked away in the back of Apollo 8's flight manual, last-ditch procedures to be used if both the navigation and communications systems failed. Unfortunately, we had removed those procedures from the flight manual after Apollo 8. We never thought they would be used.
Houston's reply was: "You will have to use them now!"
The procedures called for manually rotating the spacecraft, using our newly acquired
"flying skills", to put Earth in the lunar module window. In that window I had mounted
a crosshair "gunsight". If I could line up the terminator on Earth, the line between daylight and darkness, with the horizontal line of my gunsight, then the lunar module's descent engine would be properly positioned to correct our angle of entry into the atmosphere. We had only one chance to make the manoeuvre: at the point in our flight home when we had just left the sphere of influence of the Moon and had the least forward velocity.
Aquarius's clock had failed, so I told Jack to time the burn with his Omega wristwatch. I had two three-axis attitude controllers in Aquarius, the primary and a back-up. I told Fred to use the back-up controller to maintain yaw control. I would control pitch and roll with the primary controller. Two emergency electrical buttons were located on the left side of the console. One was labelled "Start" and the other "Stop".
They were direct electrical links from the batteries to the descent engine. This was the one and only time they were ever used on an Apollo flight.
At the proper time, I pushed Start. The engine came on full blast. Fred and I jockeyed Earth in the window. Fourteen seconds later, Jack yelled "Stop!" and I pushed the button.
Mission control monitored the burn via telemetry: "Ignition!... Thrust looks good... It shut down... Nice work."
"Let's hope it was," we replied.
Space network radars soon confirmed that Apollo 13 was comfortably back within the entry corridor. During the rest of the flight, we just hung on. The temperature kept dropping. Fred and I pulled on our lunar boots. We tried to get some sleep, but the cold, damp environment made it almost impossible. The food was cold and tasteless. Finally, on Thursday evening, Jack began receiving procedures from mission control on how to power up the dormant Odyssey with the entry battery.
By Friday morning, the conclusion of the flight of Apollo 13 was only hours away. Jack
looked out the window and noted that "Earth is whistling in like a freight train" - our velocity was approaching 24,000 miles per hour.
By that time, all systems in the command module were operating. With a sigh of relief, he noted that the condensation did not short out the electrical equipment.
At approximately 138 hours elapsed time, we received permission to jettison our service module. This module contained our two large liquid oxygen tanks, the suspected location of the explosion.
I was in Aquarius, straining to get a glimpse and photograph the service module as it drifted by: "OK, I've got her... There's one whole side of that spacecraft missing: right by the high gain antenna, the whole panel is blown out, almost to the base of the engine - it's a mess."
At about 141 hours elapsed time, Fred and I joined Jack back in Odyssey. The hatch between the two spacecraft was closed and we prepared to jettison Aquarius. She had been a good ship that supported three stranded astronauts for over 84 hours and provided the propulsion to get us home. We jettisoned Aquarius with less than four and a half hours of electrical power remaining.
At 142 hours 40 minutes elapsed time, Odyssey slammed into the thin upper air at about 400,000ft. A pink glow came through our windows, when the atmosphere started to decelerate the spacecraft, and the temperature on the heat shield rose to 5,000OF. When we reached 40,000ft, the drogue chutes popped out followed by three beautiful main parachutes.
Odyssey splashed into the Pacific Ocean just a mile or so from the USS Iwo Jima on Friday, April 17, after a flight lasting 142 hours, 54 minutes and 41 seconds.
The film Apollo 13 will be premiered in London on Sept 6 and will be released nationally from Sept 22. Jim Lovell and Jeffrey Kluger have also written a Coronet paperback.
