Apollo 13 (29)
"Houston, we have a problem..."
Pad 39-A (7)
Saturn-V AS-508 ()
High Bay 1
Firing Room 1
Apollo 13 was supposed to land in the Fra Mauro area. An explosion on board forced
Apollo 13 to circle the moon without landing. The Fra Mauro site was reassigned to
Saturday, April 11, 1970 at 13:13
At five and a half minutes after liftoff,
Lovell felt a little vibration. Then the center
engine of the S-II stage shut down two minutes early. This
caused the remaining four engines to burn 34 seconds longer
than planned, and the S-IVB third stage had to burn nine seconds
longer to put Apollo 13 in orbit.
Days before the mission, backup LM pilot
Charlie Duke inadvertently exposed the crew to
German measles. Command module pilot,
Ken Mattingly, turned out to have no immunity to
measles and was replaced by backup command module pilot
Ground tests before launch, indicated the possibility of a
poorly insulated supercritical helium tank in the LM's descent
stage so the flight plan was modified to enter the LM three
hours early in order to obtain an onboard readout of helium
The No. 2 oxygen tank, serial number 10024X-TA0009 had been
previously installed in the service module of
Apollo 10, but was removed
for modification (and was damaged in the process of removal).
The tank was fixed, tested at the factory, installed in the
Apollo 13 service module, and tested again during the Countdown
Demonstration Test (CDT) at the Kennedy Space Center beginning
March 16, 1970. The tanks normally are emptied to about half
full, and No. 1 behaved all right. But No. 2 dropped to only
92 percent of capacity. Gaseous oxygen at 80 psi was applied
through the vent line to expel the liquid oxygen, but to no
avail. An interim discrepancy report was written, and on March
27, two weeks before launch, detanking operations were resumed.
No. 1 again emptied normally, but No. 2 did not. After a conference
with contractor and NASA personnel, the test director decided
to "boil off" the remaining oxygen in No. 2 by using the electrical
heater within the tank. The technique worked, but it took
eight hours of 65-volt DC power from the ground support equipment
to dissipate the oxygen. Due to an oversight in replacing
an underrated component during a design modification, this
turned out to severely damage the internal heating elements
of the tank.
Altitude: xxx miles
Inclination: xxx degrees
Earth Orbits: 1.5
Duration: 5 Days, 22 hours, 54 min, 41 seconds
Lunar Location: None
Lunar Coordinates: None
April 17, 1970, Pacific Ocean.
Recovery Ship: USS Iwo Jima
Third lunar landing
attempt. Mission was aborted after rupture of service module
oxygen tank. Classed as "successful failure" because of experience
in rescuing crew. Spent upper stage successfully impacted
on the Moon.
The first two days the crew ran into a couple of minor surprises,
but generally Apollo 13 was looking like the smoothest flight
of the program. At 46 hours, 43 minutes
Joe Kerwin, the CapCom on duty, said, "The spacecraft
is in real good shape as far as we are concerned. We're bored
to tears down here." It was the last time anyone would mention
boredom for a long time.
At 55 hours, 46 minutes, as the crew finished a 49-minute
TV broadcast showing how comfortably they lived and worked
Lovell stated,"This is the crew of Apollo 13 wishing
everybody there a nice evening, and we're just about ready
to close out our inspection of Aquarius (the LM) and get back
for a pleasant evening in Odyssey (the CM). Good night."
Nine minutes later, oxygen tank No. 2 blew up, causing the
No. 1 tank also to fail. The Apollo 13 command modules normal
supply of electricity, light, and water was lost, and they
were about 200,000 miles from Earth.
The message came in the form of a sharp bang and vibration.
Jack Swigert saw a warning light that accompanied
the bang, and said,
"Houston, we've had a problem here."
Lovell came on and told the ground that it was
a main B bus undervolt. The time was 21:08 hours on April
Next, the warning lights indicated the loss of two of Apollo
13's three fuel cells, which were the spacecrafts prime source
of electricity. With warning lights blinking on, one oxygen
tank appeared to be completely empty, and there were indications
that the oxygen in the second tank was rapidly being depleted.
Thirteen minutes after the explosion,
Lovell happened to look out of the left-hand window,
and saw the final evidence pointing toward potential catastrophe.
"We are venting something out into the.. into space," he reported
Jack Lousma, the CapCom replied, "Roger, we copy
Lovell said, "It's a gas of some sort." It was
oxygen gas escaping at a high rate from the second, and last,
(by James A. Lovell, from
Apollo Expeditions to the Moon, edited by Edgar
M. Cortright, NASA SP 350, Washington, DC, 1975 )
The first thing the crew did, even before discovering the
oxygen leak, was to try to close the hatch between the CM
and the LM. They reacted spontaneously, like submarine crews,
closing the hatches to limit the amount of flooding. First
Jack and then
Lovell tried to lock the reluctant hatch, but the
stubborn lid wouldn't stay shut. Exasperated, and realizing
that there wasn't a cabin leak, they strapped the hatch to
the CM couch.
The pressure in the No. 1 oxygen tank continued to drift downward;
passing 300 psi, now heading toward 200 psi. Months later,
after the accident investigation was complete, it was determined
that, when No. 2 tank blew up, it either ruptured a line on
the No. 1 tank, or caused one of the valves to leak. When
the pressure reached 200 psi, the crew and ground controllers
knew that they would lose all oxygen, which meant that the
last fuel cell would also die.
At 1 hour and 29 seconds after the bang,
Jack Lousma, then CapCom, said after instructions
from Flight Director Glynn Lunney, "It is slowly going to
zero, and we are
starting to think about the LM lifeboat."
Swigert replied, "That's what we have been thinking
Ground controllers in Houston faced a formidable task. Completely
new procedures had to be written and tested in the simulator
before being passed up to the crew. The navigation problem
had to be solved; essentially how, when, and in what attitude
to burn the LM descent engine to provide a quick return home.
With only 15 minutes of power left in the CM, CapCom told
the crew to make their way into the LM.
Lovell quickly floated through the tunnel, leaving
Jack to perform the last chores in the Command
Module. The first concern was to determine if there were enough
consumables to get home? The LM was built for only a 45-hour
lifetime, and it needed to be stretch to 90. Oxygen wasn't
a problem. The full LM descent tank alone would suffice, and
in addition, there were two ascent-engine oxygen tanks, and
two backpacks whose oxygen supply would never be used on the
lunar surface. Two emergency
bottles on top of those packs had six or seven pounds each
in them. (At LM jettison, just before reentry, 28.5 pounds
of oxygen remained, more than half of what was available after
Power was also a concern. There were 2,181 ampere hours in
the LM batteries, Ground controllers carefully worked out
a procedure where the CM batteries were charged with LM power.
All non-critical systems were turned off and energy consumption
was reduced to a fifth of normal, which resulted in having
20 percent of our LM electrical power left when Aquarius was
jettisoned. There was one electrical close call during the
mission. One of the CM batteries vented with such force that
it momentarily dropped off the line. Had the battery failed,
there would be insufficient power to return the ship to Earth.
Water was the main consumable concern. It was estimated that
the crew would run out of water about five hours before Earth
reentry, which was calculated at around 151 hours. However,
Apollo 11 (which had not sent its LM ascent stage
crashing into the Moon as in subsequent missions) showed that
its mechanisms could survive seven or eight hours in space
without water cooling. The crew conserved water. They cut
down to six ounces each per day, a fifth of normal intake,
and used fruit juices; they ate hot dogs and other wet-pack
foods when they ate at all. The crew became dehydrated throughout
the flight and set a record that stood up throughout Apollo:
Lovell lost fourteen pounds, and the crew lost
a total of 31.5 pounds, nearly 50 percent more than any other
crew. Those stringent measures resulted in the crew finishing
with 28.2 pounds of water, about 9 percent of the total.
Removal of Carbon Dioxide was also a concern. There were enough
lithium hydroxide canisters, which remove carbon dioxide from
the spacecraft, but the square canisters from the Command
Module were not compatible with the round openings in the
Lunar Module environmental system. There were four cartridge
from the LM, and four from the backpacks, counting backups.
However, the LM was designed to support two men for two days
and was being asked to care for three men nearly four days.
After a day and a half in the LM a warning light showed that
the carbon dioxide had built up to a dangerous level. Mission
Control devised a way to attach the CM canisters to the LM
system by using plastic bags, cardboard, and tape all materials
carried on board.
One of the big questions was, "How to get back safely to Earth?"
The LM navigation system wasn't designed to help us in this
situation. Before the explosion, at 30 hours and 40 minutes,
Apollo 13 had made the normal midcourse correction, which
would take it out of a free-return-to-Earth trajectory and
put it on a lunar landing course. Now the task was to get
back on a free-return course. The ground computed a 35-second
burn and fired it 5 hours after the explosion. As they approached
the Moon, another burn was computed; this time a long 5-minute
burn to speed up the return home. It took place 2 hours after
rounding the far
side of the Moon,
The Command Module navigational platform alignment was transferred
to the LM but verifying alignment was difficult. Ordinarily
the alignment procedure uses an onboard sextant device, called
the Alignment Optical Telescope, to find a suitable navigation
star. Then with the help of the onboard computer verify the
guidance platform's alignment. However, due to the explosion,
a swarm of debris from the ruptured service module made it
impossible to sight real stars. An alternate procedure was
developed to use the sun as an alignment star. Lovell
rotated the spacecraft to the attitude Houston had requested
and when he looked through the AOT, the Sun was just where
it was expected. The alignment with the Sun proved to be less
than a half a degree off. The ground and crew then knew they
could do the 5-minute P.C. + 2 burn with assurance, and that
would cut the total time of our voyage to about 142 hours.
At 73:46 hours the air-to-ground transcript describes the
Lovell: O.K. We got it. I think we got it. What diameter
Haise: Yes. It's coming back in. Just a second.
Lovell: Yes, yaw's coming back in. Just about it.
Haise: Yaw is in....
Lovell: What have you got?
Haise: Upper right corner of the Sun....
Lovell: We've got it! If we raised our voices,
I submit it was justified.
"I'm told the cheer of the year went up in Mission Control.
Flight Director Gerald Griffin, a man not easily shaken, recalls:
"Some years later I went back to the log and looked up that
mission. My writing was almost illegible I was so damned nervous.
And I remember the exhilaration running through me: My God,
that's kinds the last hurdle -- if we can do that, I know
we can make it. It was funny, because only the people involved
knew how important it was to have that platform properly aligned."
Yet Gerry Griffin barely mentioned the alignment in his change-of-shift
briefing -- "That check turned out real well" is all he said
an hour after his penmanship failed him.
James A. Lovell ( Apollo
Expeditions to the Moon, edited by Edgar M. Cortright,
NASA SP; 350, Washington, DC, 1975 )
The trip was marked by discomfort beyond the lack of food
and water. Sleep was almost impossible because of the cold.
When the electrical systems were turned off, the spacecraft
lost and important source of heat. The temperature dropped
to 38 F and condensation formed on all the walls.
A most remarkable achievement of Mission Control was quickly
developing procedures for powering up the CM after its long
cold sleep. Flight controllers wrote the documents for this
innovation in three days, instead of the usual three months.
The Command Module was cold and clammy at the start of power
up. The walls, ceiling, floor, wire harnesses, and panels
were all covered with droplets of water. It was suspected
conditions were the same behind
the panels. The chances of short circuits caused apprehension,
but thanks to the safeguards built into the command module
after the disastrous Apollo
1 fire in January 1967, no arcing took place. The
droplets furnished one sensation as we decelerated in the
rained inside the CM.
Four hours before landing, the crew shed the service module;
Mission Control had insisted on retaining it until then because
everyone feared what the cold of space might do to the unsheltered
CM heat shield. Photos of the Service Module showed one whole
panel missing, and wreckage hanging out, it was a sorry mess
as it drifted away. Three hours later the crew left the Lunar
Module Aquarius and then splashed down gently in the Pacific
Ocean near Samoa.
After an intensive investigation, the Apollo 13 Accident Review
Board identified the cause of the explosion. In 1965 the CM
had undergone many improvements, which included raising the
permissible voltage to the heaters in the oxygen tanks from
28 to 65 volts DC. Unfortunately, the thermostatic switches
on these heaters weren't modified to suit the change. During
one final test on the launch pad, the heaters were on for
a long period of time. "This subjected the wiring in the vicinity
of the heaters to very high temperatures (1000 F), which have
been subsequently shown to severely degrade teflon insulation.
The thermostatic switches started to open while powered by
65 volts DC and were probably welded shut." Furthermore, other
warning signs during testing went unheeded and the tank, damaged
from 8 hours overheating, was a potential bomb the next time
it was filled with oxygen. That bomb exploded on April 13,
1970 -- 200,000 miles from Earth.