Apollo 13


Apollo 13 was to be the third mission to land on the Moon. An explosion in one of the oxygen tanks crippled the spacecraft during flight and the crew were forced to circle the Moon and return to the Earth without landing. Apollo 13 was launched on Saturday, 11 April, 1970 on a Saturn 5 rocket from the Kennedy Space Center, Florida.

Apollo 13 Picture

The Apollo 13 crew members were:

1. James A. Lovell (Commander)
2. John L. Swigert (Command Module Pilot)
3. Fred W. Haise (Lunar Module Pilot)

The back up crew were:

1. John W. Young (Backup Commander)
2. John L. Swigert (Backup Command Module Pilot)
3. Charles M. Duke, Jr (Backup Lunar Module Pilot)

Note: The original Command Module pilot for this mission was Thomas ‘Ken’ Mattingly, but due to exposure to measles he was replaced by his backup, Command Module pilot John L. Swigert two days before launch.

The name of the Command Module was Odyssey (CM-109) and the name of the Lunar Module was Aquarius (LM-7).


Command Module Mass: 28,945 kg
Lunar Module Mass: 15,235 kg
Lunar Landing Site: Assigned to Fra Mauro region of Moon
Landing on Moon: Landing aborted after oxygen tank explosion. Spent upper stage successfully impacted on the Moon.
Tank Rupture9:08 p.m. EST, April 13,1970
Oxygen Tank Explosion10:08 PM EST, April 13, 1970: 321,860 km from Earth
Splash-Down: April 17,1970 1:07 p.m. EST Pacific Ocean
Mission Duration: 5 days, 22 hours, 54 minutes


Crew Changes:  Measles

On 6 April 1970, Dr. Charles A. Berry (NASA’s Medical Director) reported that the main crew had been exposed to measles. Backup lunar module pilot Charles Duke had a case of german measles (rubella) and Jeffrey Lovell, the commander’s son, was down with the red measles (rubeola).

Two days before launch, the flight surgeons grounded Ken Mattingly (command module pilot) as he had no natural immunity to the disease and Lovell and Haise had had the measles as children. He was replaced by his backup, Command Module pilot John L. Swigert. This may have been a blessing in disguise for Mattingly as he never developed the measles and was re-assigned as command module pilot of Duke’s flight, Apollo 16. He also flew several Space Shuttle flights, while none of the Apollo 13 astronauts flew in space again.


Apollo 13 was launched on Saturday, 11 April , 1970 at 13:13 CST on a Saturn V rocket from Pad 39-A from Kennedy Space Center, Florida, USA as part of a manned mission in the Apollo Program. The control centre for the mission was in Houston, Texas.

Moon Rocket Problems

At five and a half minutes after lift-off, Swigert, Haise and Lovell felt a little vibration. Then the centre engine of the S-II second 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.

Engineers later discovered that this was due to dangerous pogo oscillations which might have torn the second stage apart. Smaller pogo oscillations had been seen on previous Apollo missions, but on Apollo 13 they had been amplified by an unexpected interaction with the cavitation in the turbo-pumps.

Lunar Flight Plan Modification

Ground tests before launch, indicated the possibility of a poorly insulated supercritical helium tank in the Lunar Module descent stage so the flight plan was modified to enter the Lunar Module three hours early in order to obtain an onboard readout of helium tank pressure.

Moon Landing Location

The Apollo 13 mission was scheduled to explore the Fra Mauro formation (or Fra Mauro highlands), named after the 80 kilometre diameter Fra Mauro crater, located within it. It is a widespread, hilly geological area covering large portions of the lunar surface around Mare Imbrium and is thought to be composed of ejecta from the impact which formed the mare.

Apollo 13 Disaster

At 46 hours, 43 minutes mission elapsed time, 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”.

Nine hours, 12 minutes later, Apollo 13 was more than 54 hours into its lunar mission (two days after launch), at a distance of 321,860 kilometres (199,990 miles) from Earth and more than halfway to the Moon when on 13 April 1970 an explosion ruptured an oxygen tank in the Service Module and damaged an entire panel, including all the tanks and systems inside it. The explosion was caused by a fault in the number two oxygen tank, one of two tanks contained in the Service Module. The Odyssey Command Module’s normal supply of oxygen, power and water was lost.


Mission Control had requested that the crew stir the oxygen tanks content, this was required to prevent the oxygen ‘slush’ from stratifying. The Teflon-insulated wires that provided electricity to the stirrer motor were damaged, causing a large fire when electricity was passed through them. The fire heated the surrounding oxygen, increasing the pressure inside the tank above its nominal 1,000 PSI (7 MPa) limit and causing the tank to explode. The cause of the explosion was unknown at the time. The crew and Houston thought that a meteoroid had struck the Service Module or even the Lunar Module.

Oxygen tank number 2 had a faulty tank heater thermostat which never opened, causing the tank heater to be on constantly during the flight. The tank heated up to such an extreme temperature that the insulation was burned from the internal tank wiring. When the astronaut turned on the tank fan to stir its contents, an electrical spark arced on the bare wires, caught fire and the oxygen rapidly burned. The resultant pressure caused the tank to explode.

Hey Houston, We’ve had a Problem Here

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’.

At 55 hours 46 minutes, as the crew finished a 49-minute TV broadcast showing how comfortably they lived and worked in weightlessness, Lovell pronounced the benediction: ‘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 No. 1 tank also to fail. The crew came to the slow conclusion that the normal supply of electricity, light and water was lost and they were were about 200,000 miles from Earth. They did not even have power to gimbal the engine so we could begin an immediate return to Earth.

Jack Swigert saw a warning light that accompanied the bang and was the first astronaut to call down to mission control. He said, “Houston, we’ve had a problem here”. Lovell came on and said the similar phrase: “Houston, we’ve had a problem’ and informed ground that it was a main B bus undervolt. The time was 21.08 hours on April 13.

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,” Lovell reported to Houston. Jack Lousma, the CapCom replied, “Roger, we copy you venting.” I said, “It’s a gas of some sort”. It was oxygen gas escaping at a high rate from the second and last oxygen tank.

Lunar Module Lifeboat

Apollo 13 Crew
The command module was not powered down until approximately 2 hours after the explosion. During those hours, the command module was running on its re-entry batteries and one barely functioning fuel cell. When oxygen tank number one finished its slow leak into space, the last surviving fuel cell was shut down and the crew powered down the command module to save the remaining battery power for later entering Earth’s atmosphere. With severe constraints on power, cabin heat and potable water, the crew endured great hardship and survived by using the Lunar Module still attached to the Command Service Module, as a ‘lifeboat’.

The Lunar Module was designed to sustain two people for 50 hours, but by carefully conserving both air and power, three astronauts survived in this improvised lifeboat for 95 hours (about 4 days). The lithium hydroxide canisters available for the Lunar Module’s carbon dioxide scrubbers would not last for all four days. The CM had an adequate supply of replacement canisters, but they were the wrong shape to fit the Lunar Module’s receptacle. An adapter then had to be fabricated from materials in the spacecraft.

The Lunar Module temperature was only a few degrees above freezing and water was rationed to just six ounces per person per day. Due to debris from the explosion, the navigation system was unreliable. The crew used the Sun as a navigation point to guide the crippled craft back to Earth. The Lunar Module ‘lifeboat’ procedure had actually been created during a training simulation in the simulator not long before the flight of Apollo 13.

Moon Landing Scrubbed

The damage done to the Command Space Module meant that the planned Moon-landing at the Fra Mauro Highlands had to be scrubbed.

Fighting for their lives with help from Mission Control, the crew circled the Moon and headed back to Earth, using the limited oxygen and power available in the Lunar Module Aquarius to stay alive.

Plan to return to Earth

To return the crew to Earth as quickly and safely as possible, only a single pass around the Moon was made, in what is called a free return trajectory, which uses the Moon’s gravity to “slingshot” the spacecraft back to Earth. To enter this trajectory, a significant course correction was required. This would normally have been a simple procedure, using the SM propulsion engine, but the flight controllers did not know exactly how much damage the service module had taken and did not want to risk firing the main engine. Therefore the course correction was performed by firing the Lunar Module’s descent engine, an option settled upon after extensive discussion among the engineers on the ground. The initial manoeuvre to change to a free return trajectory was made within hours of the accident. After passage around the Moon, the descent engine was fired again in order to accelerate the spacecraft’s return to Earth. Afterwards, only one more descent engine burn was required, for a minor course correction.

Because of the severe electrical power limitations following the explosion, no live TV broadcasts were made from the craft for the remainder of the mission; network commentators used models and animated footage to illustrate their coverage.

Apollo 13’s Returning to Earth

As the time for re-entry into Earth’s atmosphere approached, NASA took the unusual step of jettisoning the Service Module before the Lunar Module, so pictures of the SM could be taken for later analysis. When the crew saw the damaged service module, they reported that the access panel covering the oxygen tanks and fuel cells, which extended the entire length of the Module’s body, had been blown off.

Due to reduced temperatures on the return leg of the mission, there was extensive water condensation in the Command Module. There was some fear that this condensation could seriously damage the electronics of the Command Module by causing a short circuit. Until the electronics were activated, it was impossible to know whether this would occur. The equipment worked normally when activated, however, partly due to the extensive design modifications made to the CM after the fire aboard Apollo 1.


The lunar module burned up in Earth’s atmosphere on 17 April, 1970, having been targeted to enter over the Pacific Ocean to reduce the possibility of contamination from a SNAP 27 radioisotope thermoelectric generator (RTG) on board. After re-entry, the crew splashed down at 21°38′S, 165°22′W, SE of American Samoa, Pacific Ocean and 6.5 km (4 miles) from the retrieval ship, U.S.S. Iwo Jima almost four days after the explosion on April 17.

The crew returned unharmed to Earth, although Haise had a urinary tract infection, as a result of the scarcity of potable water on the damaged ship and the difficulty of urine disposal. The crew was instructed to store urine and other waste products on board instead of dumping them into space, to avoid altering the trajectory of the spacecraft.

Cause of the Accident

The explosion on Apollo 13 led to a lengthy investigation of the underlying cause. Based on detailed manufacturing records and logs of mission problems, the oxygen tank failure was tracked to a combination of multiple faults. Individually, they were not critical problems, but together they led to near disaster for Apollo 13.


The Apollo 13 mission has been called a ‘Successful Failure’, in that the astronauts were successfully returned safely to Earth despite not landing on the moon. Apollo 13 was supposed to land in the lunar region of Fra Mauro, but this landing site was later reassigned to Apollo 14.

Although the explosion forced the mission to be aborted, the crew was fortunate that it occurred on the first leg of the mission, when they had a maximum of supplies, equipment, and power. If the explosion had occurred while in orbit around the Moon or on the return leg after the LM had been jettisoned, the crew would have had a significantly smaller probability of survival.

Did you know?

 Apollo 13 PatchApollo 13 Mission Patch featured three flying horses of Apollo’s chariot across the sky, the motto “Ex luna, scientia” (from the Moon, knowledge) and the number of the mission in Roman numerals (APOLLO XIII). It is one of two Apollo insignias (the other being that of Apollo 11) not to include the names of the crew (which was fortunate, considering that Ken Mattingly, one of the original crew members, was replaced not long before the mission began). It was designed by artist Lumen Winter, who based it on a mural he had done for the St. Regis Hotel in New York; the mural was later purchased by actor Tom Hanks, who portrayed Lovell in the movie Apollo 13 and now is on the wall of a restaurant in Chicago, owned by Lovell’s son.

 * Apollo 13 film was released in 1995. It was directed by Ron Howard and starred Tom Hanks, Bill Paxton, and Kevin Bacon as the astronauts. It made the saying “Houston, we have a Problem” famous.

Famous Mis-Quote: “Houston, we have a problem”. Actual quote: “Okay, Houston, we’ve had a problem here”, uttered by Swigert to ground. Lovell then uttered this similar phrase: “Houston, we’ve had a problem’.

John Swigert (CMP)          =>  “Okay, Houston, we’ve had a problem here”.
Jack Lousma (CAPCOM)     =>  “This is Houston. Say again, please”.
James Lovell (Commander) =>  “Uh, Houston, we’ve had a problem”.
James Lovell (Commander) =>  “We’ve had a Main B Bus undervolt”.
Jack Lousma (CAPCOM)     =>  “Roger Main B undervolt”.
Jack Lousma (CAPCOM)     =>  “Okay, stand by thirteen, we’re looking at it”.

Is 13 a bad luck number?  The mission started on April 11, 1970 (11/4/70 UK, 4/11/70 USA: 1 + 1 + 4 + 7 = 13) at 13:13 CST, the problems began on April 13 and the mission was called Apollo 13. Since then NASA has never had another spacecraft numbered 13.

* ‘Houston, We’ve Got a Problem’, a 1974 movie while set around the Apollo 13 incident is a fictional drama about the crises faced by ground personnel when the emergency disrupts their work schedules and places additional stress on their lives.

 * Sega produced an Apollo 13 pinball machine (based on the 1995 movie rather than directly on the mission itself), featuring a 13-ball multiball.

* The Apollo 13 Mission Operations Team was awarded the Presidential Medal of Freedom for their actions during the mission, as were the astronauts.

* The Odyssey command module is currently on display at the Kansas Cosmosphere and Space Center, Hutchinson, Kansas.


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