Detailed Chronology of Events Surrounding the Apollo 13 accident
Events from 2.5 minutes before the accident to about 5 minutes after
Times given are in Ground Elapsed Time (G.E.T.), that is, the time elapsed since
liftoff of Apollo 13 on 11 April 1970 at 19:13 UT (2:13 PM EST).
55:52:00 G.E.T. is equal to 03:05:00 UT 14 April 1970 (10:05 PM April 13 EST).
55:52:31 - Master caution and warning triggered by low hydrogen
pressure in tank no. 1
55:52:58 - CapCom (Charlie Duke): "13, we've got one more item
for you, when you get a chance. We'd like you to stir up
the cryo tanks. In addition, I have shaft and trunnion .....
55:53:06 - Swigert: "Okay."
55:53:07 - CapCom: ".... for looking at Comet Bennett, if you
need it."
55:53:12 - Swigert: "Okay. Stand by."
55:53:18 - Oxygen tank No. 1 fans on.
55:53:19 - Oxygen tank No. 2 pressure decreases 8 psi.
55:53:20 - Oxygen tank No. 2 fans turned on.
55:53:20 - Stabilization control system electrical disturbance
indicates a power transient.
55:53:21 - Oxygen tank No. 2 pressure decreases 4 psi.
55:53:22.718 - Stabilization control system electrical
disturbance indicates a power transient.
55:53:22.757 - 1.2 Volt decrease in ac bus 2 voltage.
55:53:22.772 - 11.1 amp rise in fuel cell 3 current for one
sample
55:53:26 - Oxygen tank No. 2 pressure begins rise lasting for
24 seconds.
55:53:38.057 - 11 volt decrease in ac bus 2 voltage for one
sample.
55:53:38.085 - Stabilization control system electrical
disturbance indicates a power transient.
55:53:41.172 - 22.9 amp rise in fuel cell 3 current for one
sample
55:53:41.192 - Stabilization control system electrical
disturbance indicates a power transient.
55:54:00 - Oxygen tank No. 2 pressure rise ends at a pressure
of 953.8 psia.
55:54:15 - Oxygen tank No. 2 pressure begins to rise.
55:54:30 - Oxygen tank No. 2 quantity drops from full scale for
2 seconds and then reads 75.3 percent.
55:54:31 - Oxygen tank No. 2 temperature begins to rise rapidly.
55:54:43 - Flow rate of oxygen to all three fuel cells begins
to decrease.
55:54:45 - Oxygen tank No. 2 pressure reaches maximum value of
1008.3 psia.
55:54:51 - Oxygen tank No. 2 quantity jumps to off-scale high
and then begins to drop until the time of telemetry loss,
indicating failed sensor.
55:54:52 - Oxygen tank No. 2 temperature sensor reads -151.3 F.
55:54:52.703 - Oxygen tank No. 2 temperature suddenly goes
off-scale low, indicating failed sensor.
55:54:52.763 - Last telemetered pressure from oxygen tank
No. 2 before telemetry loss is 995.7 psia.
55:54:53.182 - Sudden accelerometer activity on X, Y, Z axes.
55:54:53.220 - Stabilization control system rate changes begin.
55:54:53.323 - Oxygen tank No. 1 pressure drops 4.2 psi.
55:54:53.500 - 2.8 amp rise in total fuel cell current.
55:54:53.542 - X, Y, and Z accelerations in CM indicate 1.17g,
0.65g, and 0.65g.
55:54:53.555 - Master caution and warning triggered by DC main
bus B undervoltage. Alarm is turned off in 6 seconds. All
indications are that the cryogenic oxygen tank No. 2 lost
pressure in this time period and the panel separated.
55:54:54.741 - Nitrogen pressure in fuel cell 1 is off-scale
low indicating failed sensor.
55:54:55.350 - Telemetry recovered.
55:54:56 - Service propulsion system engine valve body
temperature begins a rise of 1.65 F in 7 seconds. DC main
bus A decreases 0.9 volts to 28.5 volts and DC main bus B
0.9 volts to 29.0 volts. Total fuel cell current is 15
amps higher than the final value before telemetry loss.
High current continues for 19 seconds. Oxygen tank No. 2
temperature reads off-scale high after telemetry recovery,
probably indicating failed sensors. Oxygen tank No. 2
pressure reads off-scale low following telemetry recovery,
indicating a broken supply line, a tank pressure below
19 psi, or a failed sensor. Oxygen tank No. 1 pressure
reads 781.9 psia and begins to drop.
55:54:57 - Oxygen tank No. 2 quantity reads off-scale high
following telemetry recovery indicating failed sensor.
55:55:01 - Oxygen flow rates to fuel cells 1 and 3 approached
zero after decreasing for 7 seconds.
55:55:02 - The surface temperature of the service module
oxidizer tank in bay 3 begins a 3.8 F increase in a 15
second period. The service propulsion system helium tank
temperature begins a 3.8 F increase in a 32 second period.
55:55:09 - DC main bus A voltage recovers to 29.0 volts, DC
main bus B recovers to 28.8.
55:55:20 - Swigert: "Okay, Houston, we've had a problem here."
55:55:28 - Duke: "This is Houston. Say again please."
55:55:35 - Lovell: "Houston, we've had a problem. We've had a
main B bus undervolt."
55:55:42 - Duke: "Roger. Main B undervolt"
55:55:49 - Oxygen tank No. 2 temperature begins steady drop
lasting 59 seconds indicating a failed sensor.
55:56:10 - Haise: "Okay. Right now, Houston, the voltage is --
is looking good. And we had a pretty large bang associated
with the caution and warning there. And as I recall, main B
was the one that had an amp spike on it once before.
55:56:30 - Duke: "Roger, Fred"
55:56:38 - Oxygen tank No. 2 quantity becomes erratic for 69
seconds before assuming an off-scale low state, indicating a
failed sensor.
55:56:54 - Haise: "In the interim here, we're starting to go
ahead and button up the tunnel again."
55:57:04 - Haise: "That jolt must have rocked the sensor on -
see now - oxygen quantity 2. It was oscillating down
around 20 to 60 percent. Now it's full-scale high."
55:57:39 - Master caution and warning triggered by DC main
bus B undervoltage. Alarm is turned off in 6 seconds.
55:57:40 - DC main bus B drops below 26.25 volts and continues
to fall rapidly.
55:57:44 - Lovell: "Okay. And we're looking at our service
module RCS helium 1. We have -- B is barber poled and D
is barber poled, helium 2, D is barber pole, and secondary
propellants, I have A and C barber pole."
AC bus fails within 2 seconds.
55:57:45 - Fuel cell 3 fails.
55:57:59 - Fuel cell current begins to decrease.
55:58:02 - Master caution and warning caused by AC bus 2 being
reset.
55:58:06 - Master caution and warning triggered by DC main bus
undervoltage.
55:58:07 - DC main bus A drops below 26.25 volts and in the
next few seconds levels off at 25.5 volts.
55:58:07 - Haise: "AC 2 is showing zip."
55:58:25 - Haise: "Yes, we got a main bus A undervolt now,
too, showing. It's reading about 25 and a half. Main B is
reading zip right now."
56:00:06 - Master caution and warning triggered by high
hydrogen flow rate to fuel cell 2.
Apollo 13 Accident Page
Apollo 13 Home Page
Questions and comments about this page should be addressed to:
Dr. David R. Williams, dwilliam@nssdc.gsfc.nasa.gov, (301) 286-1258
NSSDC, Mail Code 633, NASA/Goddard Space Flight Center, Greenbelt, MD 20771
NASA Official: J. H. King, king@nssdca.gsfc.nasa.gov
Last Updated: 08 January 1997, DRW