Apollo 13's damaged service module, photographed by the crew from the command module after jettisoning it shortly before reentry
|Mission type||Crewed lunar landing attempt|
|Mission duration||5 days, 22 hours, 54 minutes, 41 seconds|
|Launch mass||101,261 pounds (45,931 kg)|
|Landing mass||11,133 pounds (5,050 kg)|
|Start of mission|
|Launch date||April 11, 1970, 19:13:00UTC|
|Rocket||Saturn V SA-508|
|Launch site||Kennedy LC-39A|
|End of mission|
|Recovered by||USS Iwo Jima|
|Landing date||April 17, 1970, 18:07:41UTC|
|Landing site||South Pacific Ocean|
|Flyby of Moon (orbit and landing aborted)|
|Closest approach||April 15, 1970, 00:21:00 UTC|
|Distance||254 kilometers (137 nmi)|
|Docking with LM|
|Docking date||April 11, 1970, 22:32:08 UTC|
|Undocking date||April 17, 1970, 16:43:00 UTC|
Left to right Lovell, Swigert, Haise, 12 days after their return.
Apollo 13 was the seventh crewed mission in the Apollo space program and the third intended to land on the Moon. The craft was launched on April 11, 1970, from Kennedy Space Center (KSC), but the lunar landing was aborted after an oxygen tank in the service module (SM) failed two days into the mission. The crew instead looped around the Moon, and returned safely to Earth on April 17, 1970. The mission was commanded by Jim Lovell with Jack Swigert as command module pilot (CMP) and Fred Haise as lunar module pilot (LMP). Swigert was a late replacement for the original CMP Ken Mattingly, who was grounded after exposure to rubella.
The oxygen tank failure was caused by accidental ignition of damaged wire insulation inside it during a routine tank stirring operation. The SM soon lost all of its oxygen, needed for breathing and for generating electrical power. Command module (CM) power had to be shut down to conserve its remaining resources for reentry, forcing the crew to transfer to the lunar module (LM) as a lifeboat. With the lunar landing cancelled, mission controllers worked feverishly to bring the crew home alive.
Although the LM was designed to support two men on the lunar surface for two days, Mission Control in Houston improvised new procedures so it could support three men for four days. The crew experienced great hardship caused by limited power, loss of cabin heat, shortage of potable water, and the critical need to adapt the carbon dioxide removal system. There was renewed interest in the Apollo program sparked by the astronauts' peril, with tens of millions watching the splashdown in the South Pacific Ocean by television.
An investigative review board found fault with the testing of the oxygen tank and the fact combustible Teflon was placed inside it. The flight passed the far side of the Moon at an altitude of 254 kilometers (137 nautical miles) above the lunar surface, and 400,171 km (248,655 mi) from Earth, a spaceflight record marking the farthest humans have traveled from Earth. The story of Apollo 13 has been dramatized multiple times, most notably in the 1995 film Apollo 13.
Crew and key Mission Control personnel
Fourth and last spaceflight
|Command module pilot||Jack Swigert|
|Lunar module pilot||Fred Haise|
Lovell (42 years old at the time of the mission) was a graduate of the United States Naval Academy and had been a naval aviator and test pilot before being selected for the second group of astronauts in 1962; he flew with Frank Borman in Gemini 7 and Buzz Aldrin in Gemini 12 before flying in Apollo 8 in 1968, the first spacecraft to orbit the Moon. Swigert (38 years old) held a B.S. in mechanical engineering and an M.S. in aerospace science; he had served in the Air Force and in state air national guards, and was an engineering test pilot prior to being selected for the fifth group of astronauts in 1966. Haise (35 years old) held a B.S. in aeronautical engineering, had been a Marine Corps fighter pilot, and was a civilian research pilot for NASA when he was selected as a Group 5 astronaut.
According to the standard crew rotation in place during the Apollo program, the prime crew for Apollo 13 would have been the backup crew for Apollo 10 with Mercury and Gemini veteran Gordon Cooper in command, Donn F. Eisele as command module pilot (CMP) and Edgar Mitchell as lunar module pilot (LMP). Deke Slayton, NASA's Director of Flight Crew Operations, never intended to rotate Cooper and Eisele to another mission, as both were out of favor with NASA management for various reasons (Cooper for his lax attitude towards training, and Eisele for incidents aboard Apollo 7 and an extra-marital affair). He assigned them to the backup crew simply because of a lack of flight-qualified manpower in the Astronaut Office at the time the assignment needed to be made.
Thus, the original assignment Slayton submitted to his superiors for this flight was Commander Alan Shepard, Command Module Pilot Stuart Roosa and Lunar Module Pilot Edgar Mitchell. For the first time ever, Slayton's recommendation was rejected by management, who felt that Shepard needed more time to train properly for a lunar flight, as he had only recently resumed active astronaut status after undergoing experimental surgery to correct an inner ear disorder which had kept him grounded since his Mercury flight in 1961. Thus, Lovell's crew, backup for the historic Apollo 11 mission and therefore slated for Apollo 14, was swapped with Shepard's making the prime crew for Apollo 13:
|Command module pilot||Ken Mattingly|
|Lunar module pilot||Fred Haise|
NASA assigned a backup crew of John Young as commander, Jack Swigert as command module pilot and Charles Duke as lunar module pilot. Seven days before launch, Duke contracted rubella from one of his children. This exposed both the prime and backup crews, who trained together. Mattingly was found to be the only one of the other five who had not had rubella as a child and thus was not immune. Three days before launch, at the insistence of the Flight Surgeon, Swigert was moved to the prime crew. Normally, if a member of the prime crew had to be replaced, the entire backup crew would fly, but Duke's illness ruled this out, leading to the decision that Swigert should fly with Lovell and Haise.
- Gene Kranz – White team; (lead)
- Glynn Lunney – Black team;
- Milt Windler – Maroon team;
- Gerry Griffin – Gold team.
The CAPCOMs were Kerwin, Brand, Lousma, Young and Mattingly.
Mission insignia and call signs
The Apollo 13 mission insignia depicts the Greek god of the Sun, Apollo, with three horses pulling his chariot across the face of the Moon, and the Earth seen in the distance. This is meant to symbolize the Apollo flights bringing the light of knowledge to all people. The motto, Ex luna, scientia means "From the Moon, knowledge"; Lovell adapted the motto of his alma mater, the Naval Academy, Ex scientia, trident (From knowledge, sea power).
On the patch, the mission number appeared in Roman numerals as Apollo XIII. It did not have to be modified after Mattingly's replacement by Swigert since it is one of only two Apollo mission insignia—the other being Apollo 11—not to include the names of the crew. It was designed by artist Lumen Martin Winter, who based it on a mural he had painted for The St. Regis Hotel in New York City. 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 near Chicago owned by Lovell's son. That representation shows four horses, deemed to be one for each member of the crew who flew, and the fourth for Mattingly.
The motto was in Lovell's mind when he chose the call sign Aquarius for the lunar module, taken from Aquarius, the bringer of water. Some from the media erroneously reported that the call sign was taken from a song by that name from the musical Hair. The command module's call sign, Odyssey, was chosen not only for its Homeric association but to refer to the recent movie, 2001: A Space Odyssey, based on a short story by science fiction author Arthur C. Clarke. In his book, Lovell indicated he chose the name Odyssey because he liked the word and its definition: a long voyage with many changes of fortune.
Hardware and mission preparation
Launch vehicle and spacecraft
The Saturn V used to carry Apollo 13 to the Moon was numbered SA-508, and was almost identical to those used on Apollo 8 through 12. Including the spacecraft, the rocket was 25,600 pounds (11,600 kg) heavier than Apollo 12's. The S1-C engines were rated at 100,000 pounds (45,000 kg) less total thrust than Apollo 12's, though they remained within specifications. Extra fuel was carried; the reason for this was in part as a preliminary to the future J missions to the Moon that would carry heavier payloads. This made the vehicle the heaviest yet flown by NASA and made Apollo 13 visibly slower to clear the launch tower than earlier missions.
On previous missions, a burn had been performed to send the S-IVB third stage into solar orbit once the spacecraft detached from it. At the First Lunar Science Conference in January 1970, it was revealed that while the seismometer left by Apollo 12 had detected almost daily impacts of objects onto the Moon, none had been as large as that of Apollo 12's LM, Intrepid, which had been deorbited after being jettisoned. In the hope larger impacts would allow scientists on Earth to probe the structure of the Moon's crust, it was decided that beginning with Apollo 13, the launch vehicle's S-IVB stage would be crashed into the Moon.
The Apollo 13 spacecraft consisted of Command Module 109 and Service Module 109 (together CSM-109), called Odyssey, and Lunar Module 7 (LM–7), called Aquarius. Also considered part of the spacecraft were the Launch Escape System which would propel the CM to safety in the event of a problem during launch, and the Spacecraft–LM Adapter, numbered as SLA–16, which housed the LM during the first hours of the mission.
Concerned about how close Apollo 11's LM, Eagle, had come to running out of fuel during its lunar descent, mission planners decided that beginning with Apollo 13, the CSM would bring the LM to the low orbit from which the landing attempt would commence. This was a change from Apollo 11 and 12, on which the LM made the burn to bring it to the lower orbit. The change was part of an effort to increase the amount of hover time available to the astronauts as the missions headed into rougher terrain.
ALSEP and other equipment
Apollo 11 had left a seismometer on the Moon, but the solar-powered unit did not survive its first two-week-long lunar night. The Apollo 12 astronauts also left one as part of its ALSEP installation of nuclear-powered scientific instruments. Apollo 13 carried a seismometer (known as the Passive Seismic Experiment, or PSE) similar to Apollo 12's as part of its ALSEP package, which was carried in the LM descent stage's scientific equipment bay. That seismometer was to be calibrated by the impact, after jettison, of the ascent stage of Apollo 13's LM, an object of known mass and velocity impacting at a known location.
Other ALSEP experiments included a Heat Flow Experiment (HFE), which would involve the drilling of two holes 10 feet (3.0 m) deep. This was Haise's responsibility; he was also to drill a third hole of that depth for a core sample. A Charged Particle Lunar Environment Experiment (CPLEE) measured the protons and electrons of solar origin reaching the Moon. The package also included a Lunar Atmosphere Detector (LAD) and a Dust Detector, to measure the accumulation of debris on the ALSEP. The Heat Flow Experiment and the CPLEE were flown for the first time on Apollo 13; the other experiments had been flown before.
To power the ALSEP, the SNAP-27 radioisotope thermoelectric generator was flown. Developed by the U.S. Atomic Energy Commission, SNAP-27 was first flown on Apollo 12. The fuel capsule contained about 8.36 pounds (3.79 kg) of plutonium oxide. The cask placed around the capsule for transport to the Moon was built with heat shields of graphite and of beryllium, with structural parts of titanium and of Inconel materials. Thus, it was built to withstand the heat of reentry into the Earth's atmosphere in the event of an aborted mission.
Like Apollo 11 and 12, Apollo 13 flew the Solar Wind Composition Experiment, a windowshade-like device that would be deployed on the lunar surface and then be folded up and brought back by the astronauts. It also flew the Lunar Stereo Closeup Camera, intended to show the fine structure of lunar rocks and soil. A United States flag was also taken, to be erected on the Moon's surface. For Apollo 11 and 12, the flag had been placed in a heat-resistant tube on the front landing leg; it was moved for Apollo 13 to the Modularized Equipment Stowage Assembly (MESA) in the LM descent stage. The structure to fly the flag on the airless Moon was improved from Apollo 12's.
For the first time, red stripes were placed on the helmet, arms and legs of the commander's A7L spacesuit. This was done as after Apollo 11, those reviewing the images taken had trouble distinguishing Armstrong from Aldrin, but the change was approved too late for Apollo 12. The Apollo 12 moon walkers had gotten thirsty during their lunar surface activities; the new drink bags that could be placed inside the helmets and sipped from as the astronauts explored were demonstrated by Haise during Apollo 13's final television broadcast before the accident.
Landing site selection; astronaut training
Apollo 12 had shown that lunar astronauts could perform a precision landing. Thus, mission planners for Apollo 13 were able to seek a smaller landing target someplace other than the lunar mares, or seas, upon which Apollo 11 and 12 had set down. Apollo 11 and 12 each had a backup site for landing in case of launch delays; this requirement also was deleted for Apollo 13. This did not open up the whole Moon to planners—sites still had to be in the equatorial region of the near side —but they could be more flexible and could seek a site of greater scientific interest.
In anticipation of successful lunar landings, the Site Selection Board met in June 1969 to plan Apollo 13, and a site near Fra Mauro crater gained consensus. The Fra Mauro formation was believed to contain much material spattered by the impact that had filled the Imbrium basin, early in the Moon's history. Dating it would provide information not only about the Moon, but about the Earth's early history. The landing site was about 26 miles (42 km) north of Fra Mauro crater itself, near what was dubbed Cone crater, a site where an impact was believed to have drilled deep into the lunar regolith. Due to the roughness of the terrain, the selected landing site was over a mile (two kilometers) from Cone crater, but Lovell, who as commander was to perform the landing, had the option of setting down closer if he believed he could do so safely. NASA initially had few high-quality photographs of that location, but after Dick Gordon, CMP of Apollo 12, took more from orbit in November 1969, Fra Mauro was confirmed as Apollo 13's landing site.
The astronauts of Apollo 11 had minimal time for geology training, with only six months between crew assignment and launch; higher priorities took much of their time. Apollo 12 saw more training, including practice traverses, using a Capcom and a simulated backroom of scientists, to whom the astronauts had to describe what they saw. Scientist-astronaut Harrison Schmitt saw that there was limited enthusiasm for geology field trips, and arranged for Lovell and Haise to meet his old professor, Caltech's Lee Silver. The two astronauts, and backups Young and Duke, went on their own time and expense on a field trip with Silver. At the end of their week together, Lovell made Silver their geology mentor, who would be extensively involved in the geology planning for Apollo 13. Farouk El-Baz oversaw the training of Mattingly and his backup, Swigert, which involved describing and photographing simulated lunar landmarks from airplanes. El-Baz had all three prime crew astronauts describe geologic features they saw during their flights between Houston and Kennedy Space Center (KSC); Mattingly's enthusiasm caused other astronauts, such as Apollo 14's CMP, Stu Roosa, to seek out El-Baz as a teacher.
A month before the planned landing, Lovell and Haise undertook a mock EVA at Arizona's Verde Valley, over a landscape made to look as much like the lunar surface as possible. The Apollo 13 prime crew undertook over 1,000 hours of mission-specific training, more than five hours for every hour of the mission's ten-day planned duration. Each member of the prime crew spent over 400 hours in simulators of the CM and of the LM at KSC and at Houston, some of which involved the flight controllers at Mission Control. Specialized simulators at other locations were also used.
The plan was to devote the first of the two four-hour lunar surface EVAs to setting up the ALSEP; during the second, Aquarius's crew would investigate Cone crater. Lovell and Haise wore their spacesuits for some 20 walk-throughs of EVA procedures, including sample gathering and use of tools and other equipment. The astronauts flew in the "Vomit Comet" in simulated microgravity or lunar gravity, including practice in donning and doffing spacesuits. To prepare for the descent to the Moon's surface, Lovell flew the Lunar Landing Training Vehicle (LLTV). Despite the fact that four of the five LLTVs and similar Lunar Landing Research Vehicles crashed during the course of the Apollo program, mission commanders considered flying them invaluable experience.
Preparation and objectives
The LM stages, CM and SM were received at KSC in June 1969; the portions of the Saturn V were received in June and July. Thereafter, testing and assembly proceeded, culminating with the rollout of the launch vehicle, with the spacecraft atop it, on December 15, 1969. Apollo 13 was originally scheduled for launch on March 12, 1970; in January of that year NASA announced the mission would be postponed until April 11, both to allow additional time for planning and to spread out the Apollo missions over a longer period of time.
Apollo 13's primary mission objectives were to: "Perform selenological inspection, survey, and sampling of materials in a preselected region of the Fra Mauro Formation. Deploy and activate an Apollo Lunar Surface Experiments Package. Develop man's capability to work in the lunar environment. Obtain photographs of candidate exploration sites." The astronauts were also to accomplish other photographic objectives, including of the Gegenschein from lunar orbit, and of the Moon itself on the journey back to Earth. Some of this photography was to be performed by Swigert as Lovell and Haise walked on the Moon. The command module pilot was also to take photographs of the Lagrangian points of the Earth-Moon system. Apollo 13 had twelve cameras on board, including those for television and moving pictures. The crew was also to downlink bistatic radar observations of the Moon. None of these goals could be attempted because of the accident that damaged the spacecraft.
Several of the experiments for Apollo 13 were completed despite the aborted mission. An experiment to measure the amount of atmospheric electrical phenomena during the ascent to orbit had been added after Apollo 12 was struck by lightning; it returned data indicating a heightened risk during marginal weather. A series of photographs of Earth was taken to test whether a determination of cloud height could be made from synchronous satellites; this achieved the desired results. The third successful experiment, Seismic Detection of Third-Stage Lunar Impact, was the Apollo 12 seismometer's detection of the S-IVB's impact when it hit the Moon.
Flight of Apollo 13
Launch and translunar injection
The mission was launched at the planned time, 02:13:00 PM EST (19:13:00 UTC) on April 11. An anomaly occurred when the second-stage, center (inboard) engine shut down about two minutes early. The four outboard engines and the third-stage engine burned longer to compensate, and the vehicle achieved very close to the planned circular 100-nautical-mile (190 km) parking orbit, followed by a normal translunar injection about two hours later. The engine shutdown was determined to be caused by severe pogo oscillations measured at a strength of 68 g and a frequency of 16 hertz, causing the thrust frame to flex by 3 inches (76 mm). The vehicle's guidance system shut the engine down in response to sensed thrust chamber pressure fluctuations. Pogo oscillations had been seen on previous Titan rockets, and also on the Saturn V during the uncrewed Apollo 6 mission, but on Apollo 13, they were amplified by an unexpected interaction with turbopump cavitation, caused by pressure that was low, but within specifications, inside the S-II's liquid oxygen system. Fixes for pogo were already under development by NASA, but time did not permit their inclusion for Apollo 13.
Swigert performed the separation and transposition maneuvers before docking the CSM Odyssey to the LM Aquarius, and the spacecraft pulled away from the third stage, which ground controllers then sent on a course to impact the Moon in range of the Apollo 12 seismometer. The impact occurred at 77:56:40 into the mission, about 22 hours after the accident, and produced such strong signals in the Moon that the gain on that seismometer, 73 miles (117 km) from the impact, had to be turned down.
The crew settled in for the three-day trip to Fra Mauro. At 30:40:50 into the mission, with the TV camera running, the crew performed a burn to place Apollo 13 on a hybrid trajectory. This was a quicker way to reach Fra Mauro, and allowed for more propellant on the lunar descent burn, but the departure from a free return trajectory meant that if no further burns were performed, Apollo 13 would miss Earth on its return trajectory, rather than intercept it, as with a free return. Communications were enlivened when Swigert realized that in the last-minute rush, he had omitted to file his federal income tax return (due April 15), and amid laughter from mission controllers, asked how he could get an extension. He was found to be entitled to a 60-day extension for being out of the country at the deadline.
Entry into the LM to test its systems had been scheduled for 58:00:00; when the crew awoke on the third day of the mission, they were informed it had been moved up three hours and was later moved up again by another hour. A television broadcast was scheduled for 55:00:00; Lovell, acting as emcee, showed the audience the interiors of Odyssey and Aquarius. The audience was limited by the fact that none of the television networks were carrying the broadcast, forcing Marilyn Lovell (Jim Lovell's wife) to go to the VIP room at Mission Control if she wanted to watch her husband and his crewmates.
Approaching 56 hours into the mission, Apollo 13 was approximately 180,000 nautical miles (210,000 mi; 330,000 km) from Earth. To that point there had been minor glitches, similar to those on earlier Apollo missions; they had been satisfactorily resolved. Approximately six and a half minutes after the end of the TV broadcast, Haise was closing out the LM while Lovell stowed the TV camera. Jack Lousma, the CAPCOM, sent a number of minor instructions to Swigert, including changing the attitude of the craft to facilitate photography of Comet Bennett.
Sy Liebergot, the EECOM, in charge of monitoring the CSM's electrical system, was concerned that the sensor that read the pressure in the SM's Oxygen Tank 2 had earlier appeared to be malfunctioning and requested that the crew be asked to turn on the hydrogen and oxygen tank stirring fans in the SM. Normally, this would only have been done once daily, after crew wakeup, but Liebergot wanted an additional stir to destratify the cryogenic contents of the two oxygen tanks and make the readings more accurate. The Flight Director, Gene Kranz, had Liebergot wait a few minutes to allow the crew to settle down after the telecast, then Lousma passed up the request to Swigert, who activated the fans.
Ninety-five seconds after Swigert flipped those switches, the astronauts heard a "pretty large bang", accompanied by fluctuations in electrical power and the firing of the attitude control thrusters. Communications and telemetry to Earth were lost for 1.8 seconds, until the system automatically corrected by switching the high-gain S-band antenna, used for translunar communications, from narrow-beam to wide-beam mode.
The accident happened at 55:54:53; Swigert reported 26 seconds later, "Okay, Houston, we've had a problem here," echoed at 55:55:42 by Lovell, "Houston, we've had a problem. We've had a Main B Bus undervolt." Lovell's initial thought on hearing the noise was that Haise had activated the LM's cabin-repressurization valve, which also produced a bang (Haise enjoyed doing so to startle his crewmates) but Lovell could see that Haise had no idea what had happened. Swigert initially thought that a meteoroid might have struck the LM, but he and Lovell quickly realized there was no leak. The Main Bus B undervolt meant that there was insufficient current flowing from the SM's power cells (fueled by hydrogen and oxygen piped from their respective tanks) to the second of the SM's two power distribution systems. Almost everything in the CSM required power. Although the bus momentarily returned to normal status, soon both buses A and B were showing insufficient voltage. Haise checked the status of the three fuel cells, and found that two of the three were dead. Mission rules forbade entering lunar orbit unless all three fuel cells were operational.
Liebergot initially missed the worrying signs from tank 2 during the stir, as he was focusing on tank 1, believing that its reading would be a good guide to what was present in tank 2; so did controllers supporting him in the "back room". In the minutes after the accident, there were a number of unusual readings, showing that tank 2 was empty and tank 1's pressure slowly falling, that the computer on the spacecraft had reset, and that the high-gain antenna was not working. When Kranz questioned Liebergot on this he initially responded that there might be an instrumentation problem; he was often teased about that in the years to come. Lovell reported seeing out the window that the craft was venting "a gas of some sort" into space, making it clear that the issue was not simply false readings from instrumentation. The venting convinced Kranz that there was a serious problem with the spacecraft.
Since the fuel cells needed oxygen to run, when Oxygen Tank 1 ran dry, the remaining fuel cell would shut down, meaning the only significant oxygen and power remaining from the CSM's resources would be the oxygen "surge tank" in the CM and its reentry batteries. These consumables would be needed for the final hours of the mission, but the remaining fuel cell, already starved for oxygen, was tapping the surge tank to keep generating power. Kranz ordered the surge tank isolated, saving its oxygen, but this meant that the remaining fuel cell would die once most of the oxygen in tank 1 was gone, either consumed or leaked away, within two hours. The lunar module had charged batteries and full oxygen tanks for use on the lunar surface, and Kranz directed that the astronauts be told to power up the LM and use it as a "lifeboat". Using the LM in this manner had been discussed following a simulation, but had not been considered a situation likely to occur. Had the accident occurred when no LM was available (for example, on the return voyage), the astronauts would have died.
Looping around the Moon
As a lunar landing was no longer feasible, mission controllers discussed how to bring the astronauts home safely. Some wanted the astronauts to attempt a direct abort with the SM's main engine, the service propulsion system (SPS), effectively turning around without reaching the Moon. Kranz decided not to use the SPS as it took considerable power (the fuel cells would have had to last at least another hour to run the SPS) and it was uncertain whether it had been damaged in the accident. Instead, Kranz decided to let the spacecraft swing around the Moon and head back towards Earth, though this would take longer than a successful direct abort. Apollo 13 was still on a hybrid trajectory and needed to be brought back to a free return. The LM's Descent Propulsion System (DPS), although not as powerful as the SPS, would suffice for this burn, which required new software to be written by the IBM technicians assigned to Mission Control's computer bank. As the CM was being shut down around him, Lovell copied down the guidance system's orientation information and made manual calculations to transfer it to the LM's system; at his request, Mission Control checked his figures. The DPS burn of 34.23 seconds at mission time 61:29:43.49 took Apollo 13 back to a free return trajectory.
The change would get Apollo 13 back to Earth in about four days' time, with splashdown in the Indian Ocean, a place where NASA had few recovery forces. Jerry Bostick and other Flight Dynamics Officers (FIDOs) were anxious both to shorten the time, and to get Apollo 13 down in the Pacific Ocean, where the main recovery forces were located. There was a relatively quick option that would shave 36 hours off the return time, but it would involve jettisoning the SM, which would expose the CM's heat shield to space for the return journey, something it had not been designed to endure. The FIDOs also proposed other solutions. After a meeting involving a number of NASA officials and engineers, the senior individual present, Manned Spaceflight Center director Robert R. Gilruth decided on a burn that would save 12 hours and land Apollo 13 in the Pacific. This burn would take place with the DPS two hours after the point of closest approach to the Moon, or pericynthion, and was given the shorthand of PC+2 burn. Kranz's White Team of mission controllers spent most of their time in support of other teams and developing procedures, but took their consoles for the crucial PC+2 burn. As the crew prepared for the burn, they were informed that the S-IVB had impacted the Moon as planned, leading Lovell to quip, "Well, at least something worked on this flight."
Normally, the accuracy of such a burn could be assured by checking the alignment Lovell had transferred to the LM's computer against the position of one of the stars astronauts used for navigation, but the light glinting off the many pieces of debris accompanying the spacecraft made that impractical. The astronauts used the one star available whose position could not be obscured–the Sun. Houston also informed them that the Moon would be centered in the commander's window of the LM as they made the burn, which was almost perfect – less than a foot (.3 meters) per second off. The burn took place at 79:27:38.95 into the mission and lasted four minutes, 23 seconds. With Apollo 13 headed towards a splashdown in the Pacific, the crew turned its attention to shutting down most LM systems to conserve consumables.
Survival and return journey
Aquarius was designed to accommodate two astronauts during a lunar surface mission of at most 45 hours; now it would have to sustain three people for 77 to 100 hours, depending on the trajectory taken. The LM carried sufficient oxygen, but unlike the command and service module (CSM), which was powered by fuel cells that produced water as a byproduct, the LM was powered by silver-zinc batteries, so conservation of electrical power and water (used for equipment cooling as well as drinking) would be imperative. Thus, LM power consumption was reduced to the lowest levels possible; Swigert filled some drinking bags with water from the CM's water tap, but even assuming rationing of personal consumption Haise initially calculated they would run out of water for cooling about five hours before reentry. This did not present a major hazard because Haise knew that Apollo 11's LM, Eagle, once jettisoned in lunar orbit, had its systems continue to operate for 7–8 hours even with the water cut off. In the end, Apollo 13 returned to Earth with 28.2 pounds (12.8 kg) of water remaining. Their daily ration of .2 liters of water each may have been inadequate, given that the three astronauts lost a total of 31 pounds (14 kg) among them and Haise fell ill with an infection.
Availability of lithium hydroxide (LiOH) for removing carbon dioxide presented a serious problem. The LM's internal stock of LiOH canisters was not sufficient to support the crew until return, and the remainder was stored in the descent stage, out of reach. The CM had an adequate supply of canisters, but these were incompatible with the LM. Engineers on the ground improvised a way to join the cube-shaped CM canisters to the LM's cylindrical canister-sockets by drawing air through them with a suit return hose. NASA engineers referred to the improvised device as "the mailbox." The procedure to build the device was read up to the crew by CAPCOM Joe Kerwin over the course of an hour, and it was built by Swigert and Haise. Once built and installed, the device allowed the CM's canisters to work, leading to a sharp drop in the carbon dioxide level. Lovell later described the solution to the carbon dioxide problem as "a great improvisation—and a fine example of cooperation between ground and space".
Inside the darkened spacecraft, the temperature dropped to as low as 38 °F (3 °C). Lovell considered having the crew don their spacesuits, but decided this would be too hot. Instead, Lovell and Haise wore their lunar EVA boots and Swigert put on an extra coverall. All three astronauts were cold, especially Swigert who got his feet wet and had no lunar overshoes to insulate them. As they had been asked not to make any waste dumps, they had to find ways to store their urine in bags. The lack of power caused water to condense on the walls of the spacecraft, and, the crew feared, under the panels where there was electrical wiring. This turned out not to be a problem, partly because of the extensive electrical insulation improvements instituted after the Apollo 1 fire. Despite the difficult conditions, the crew voiced few complaints.
Another problem to be solved for a safe return was accomplishing a complete power-up from scratch of the completely shut-down command module, something never intended to be done in-flight. Flight controller John Aaron, with the support of grounded astronaut Mattingly and many engineers and designers, had to invent a new procedure to do this with the ship's limited power supply and time factor.
Reentry and splashdown
Despite the accuracy of the transearth injection, the spacecraft slowly drifted off course, necessitating a midcourse correction. As the LM's guidance system had been shut down following the PC+2 burn, the crew was called upon to use the terminator line between night and day on the Earth to guide them, a technique used on NASA's earth-orbit missions but never on the way back from the Moon. This burn was done using the DPS at 105:18:42 for 14 seconds, bringing the projected entry flight path angle back within safe limits. Nevertheless, an additional burn needed to be made, using the LM's reaction control system (RCS) thrusters, for 21.5 seconds at 137:40:13. The SM was jettisoned less than half an hour later, allowing the crew to see the damage for the first time, and photograph it. They reported that an entire panel was missing from the SM's exterior, the fuel cells above the oxygen tank shelf were tilted, that the high-gain antenna was damaged, and there was a considerable amount of debris elsewhere. Haise could see damage to the SM's engine bell, validating Kranz's decision not to use the SPS.
The last problem to be solved was how to separate the lunar module a safe distance away from the command module just before reentry. The normal procedure was to use the service module's RCS to pull the CSM away after releasing the LM along with the command module's docking ring, but the SM would be released before the LM, and was in any event inoperative. Grumman, the manufacturer of the LM, called a team of six University of Toronto engineers, led by senior scientist Bernard Etkin, to solve the problem within a day. The team concluded that pressurizing the tunnel connecting the lunar module to the command module just before separation would provide the force necessary to push the two modules a safe distance away from each other just prior to reentry. The team had 6 hours to accurately compute the pressure required, using slide rules. Too high a pressure could damage the hatch and its seal, endangering the astronauts on reentry; too low and the lunar module would not be sufficiently separated. Grumman relayed their calculation to NASA, and from there in turn to the astronauts, who used it successfully.
The reentry on a lunar mission was typically accompanied by about four minutes of communications blackout caused by ionization of the air around the command module. The blackout in Apollo 13's reentry lasted six minutes, which was 87 seconds longer than had been expected, attributed to the spacecraft's shallow reentry path. The possibility of heat-shield damage heightened the tension of the blackout period. Odyssey regained radio contact and splashed down safely in the South Pacific Ocean, , southeast of American Samoa and 6.5 km (3.5 nmi) from the recovery ship, USS Iwo Jima. They were on the recovery ship within 45 minutes after splashdown. Although fatigued, the crew was in good condition except for Haise, who was suffering from a serious urinary tract infection because of insufficient water intake. The crew stayed overnight on the ship and flew to Pago Pago, Samoa, the next day. They flew to Hawaii, where President Nixon awarded them the Presidential Medal of Freedom, the highest civilian honor. They stayed overnight, and then were flown back to Houston.
Prior to his trip to Honolulu, President Nixon flew to Houston to award the Apollo 13 Mission Operations Team the Presidential Medal of Freedom. He originally planned to give NASA administrator Dr. Thomas Paine the award, but Paine recommended the mission operations team.
Public and media reaction
Worldwide interest in the Apollo program was reawakened by the incident; television coverage of which was seen by millions. Four Soviet ships headed toward the landing area to assist if needed, and other nations offered assistance should the craft have to splash down elsewhere. President Richard Nixon cancelled his appointments, phoned the astronauts' families, and drove to NASA's Goddard Space Flight Center in Greenbelt, Maryland, where Apollo's tracking and communications were coordinated.
The rescue received more public attention than most spaceflights to that point, other than the first Moon landing on Apollo 11. There were worldwide headlines, and people surrounded television sets to get the latest developments, offered by networks who interrupted their regular programming for bulletins. Pope Paul VI led a congregation of 10,000 people in praying for the astronauts' safe return; ten times that number also offered prayers at a religious festival in India. The United States Senate on April 14 passed a resolution urging businesses to pause at 9 pm local time that evening to allow for employee prayer.
An estimated 40 million Americans watched Apollo 13's splashdown, carried live on all three networks, with another 30 million watching some portion of the six and one-half hour telecast. Even more outside the U.S. watched. Jack Gould of The New York Times stated that Apollo 13, "which came so close to tragic disaster, in all probability united the world in mutual concern more fully than another successful landing on the moon would have".
Investigation and response
- NASA Langley Research Center Director Edgar M. Cortright, chairman
- Robert F. Allnutt (Assistant to the Administrator, NASA Hqs.);
- Neil Armstrong (Astronaut, Manned Spacecraft Center);
- Dr. John F. Clark (Director, Goddard Space Flight Center);
- Brig. General Walter R. Hedrick Jr. (Director of Space, DCS/RED, Hqs., USAF);
- Vincent L. Johnson (Deputy Associate Administrator-Engineering, Office of Space Science and Applications);
- Milton Klein (Manager, AEC-NASA Space Nuclear Propulsion Office);
- Dr. Hans M. Mark (Director, Ames Research Center).
The board’s final report, sent to Paine on June 15, found that the failure began in the service module's number 2 oxygen tank. Damaged Teflon insulation on the wires to the stirring fan inside Oxygen Tank 2 allowed the wires to short-circuit and ignite this insulation. The resulting fire rapidly increased pressure inside the tank and the tank dome failed, filling the fuel cell bay (SM Sector 4) with rapidly expanding gaseous oxygen and combustion products. The escaping gas was probably enough by itself to blow out the aluminum exterior panel to Sector 4, but there may also have been combustion products generated as nearby insulation may have briefly burned until the departure of the panel exposed the sector to space, snuffing out the fire. As it went, the panel probably hit the nearby high-gain antenna, disrupting communications to Earth for 1.8 seconds. The report questioned the use of Teflon and other materials shown to be flammable in supercritical oxygen, such as aluminum, within the tank. The board found no evidence pointing to any other theory of the accident.
Mechanical shock forced the oxygen valves closed on the number 1 and number 3 fuel cells, putting them out of commission. The sudden failure of Oxygen Tank 2 compromised Oxygen Tank 1, causing its contents to leak out, possibly through a damaged line or valve, over the next 130 minutes, entirely depleting the SM's oxygen supply. With both SM oxygen tanks emptying, and with other damage to the SM, the mission had to be aborted.
Oxygen Tank 2 was manufactured by the Beech Aircraft Company of Boulder, Colorado, as subcontractor to North American Rockwell (NAR) of Downey, California, prime contractor for the CSM. It contained two thermostatic switches, originally designed for the command module's 28-volt DC power, but which could fail if subjected to the 65 volts used during ground testing at KSC. Under the original 1962 specifications, the switches would be rated for 28 volts, but revised specifications issued in 1965 called for 65 volts to allow for quicker tank pressurization at KSC. Nonetheless, the switches Beech used were not rated for 65 volts.
At NAR's facility, Oxygen Tank 2 had been originally installed in an oxygen shelf placed in the Apollo 10 service module, SM-106, but was removed to fix a potential electromagnetic interference problem and another shelf substituded. During removal, the shelf was accidentally dropped at least 2 inches (5 cm) because a retaining bolt had not been removed. The probability of damage from this was low, but it is possible that there was a loosely-fitting fill line whose fit was made worse by the fall. After some retesting (which did not include filling the tank with liquid oxygen), in November 1968 the shelf was re-installed in SM-109, intended for Apollo 13, which was shipped to KSC in June 1969.
After the tank was filled during the Countdown Demonstration Test, which began on March 16, 1970, it could not be emptied through the normal drain line, and a report was written. After discussion among NASA and the contractors, attempts to empty the tank resumed on March 27. When it would not empty normally, the heaters in the tank were turned on to boil off the oxygen. The thermostatic switch was designed to prevent the heaters from raising the temperature higher than 80 °F (27 °C), but it failed under the 65V power supply applied. Temperatures on the heater tube within the tank may have reached 1,000 °F (538 °C), most likely damaging the Teflon insulation. The temperature gauge was not designed to read higher than 85 °F (29 °C), so the technician monitoring the procedure detected nothing unusual. This heating had been approved by Lovell and Mattingly of the prime crew, as well as by NASA managers and engineers. But once the tank was refilled with oxygen prior to the launch of Apollo 13, and electric power was connected to it, it was in a hazardous condition. The board found that Swigert's activation of the Oxygen Tank 2 fan at the request of Mission Control caused an electrical arc that set the tank on fire.
The board conducted a test of an oxygen tank rigged with hot-wire ignitors that caused a rapid rise in temperature within the tank, after which it failed, producing telemetry similar to that seen with the Apollo 13 Oxygen Tank 2. Tests with panels similar to the one that was seen to be missing on SM sector 4 caused separation of the panel in the test apparatus.
For Apollo 14, the oxygen tank was redesigned, with the thermostats upgraded to handle the proper voltage. The heaters were retained since they were necessary to maintain oxygen pressure. The stirring fans, with their unsealed motors, were removed, which meant the oxygen quantity gauge was no longer accurate. This required adding a third tank so that no tank would go below half full. The quantity probe was upgraded from aluminum to stainless steel. The third tank was placed in Bay 1 of the SM, on the side opposite the other two, and was given an isolation valve that could isolate it from the fuel cells and from the other two oxygen tanks in an emergency, and allow it to feed the CM's environmental system only.
All electrical wiring in Bay 4 was sheathed in stainless steel. The fuel cell oxygen supply valves were redesigned to isolate the Teflon-coated wiring from the oxygen. The spacecraft and Mission Control monitoring systems were modified to give more immediate and visible warnings of anomalies. An emergency supply of 5 US gallons (19 l; 4.2 imp gal) of water was stored in the CM, and an emergency battery, identical to those that powered the LM's descent stage, was placed in the SM. The LM was modified to make easier transfer of power from LM to CM. Devices were placed in the S-II second stage to counteract pogo vibrations.
On February 5, 1971, Apollo 14's LM, Antares, landed on the Moon with astronauts Alan Shepard and Ed Mitchell aboard, near Fra Mauro, the site Apollo 13 had been intended to explore. The Lunar Atmosphere Detector, also called the Cold Cathode Gauge Experiment (CCGE), which was part of the ALSEP on Apollo 13, was not flown again. It was a version of the Cold Cathode Ion Gauge (CCIG) which featured on Apollo 12, Apollo 14, and Apollo 15. The CCGE was designed as a standalone version of the CCIG. On other missions, the CCIG was connected as part of the Suprathermal Ion Detector (SIDE). Because of the aborted landing, this experiment was never deployed.
Because Apollo 13 followed a free return trajectory, its altitude over the lunar far side was approximately 100 km (60 mi) greater than the orbital altitude on the remaining Apollo lunar missions. The Moon was almost at apogee during the mission (as it also was during the flights of Apollo 10 and Apollo 15), which also increased the distance from the Earth. The combination of the two effects ensures that Apollo 13 holds the absolute altitude record for a crewed spacecraft, reaching a distance of 400,171 kilometers (248,655 mi) from Earth at 7:21 pm EST, April 14, 1970 (00:21:00 UTC April 15).
As a joke following Apollo 13's successful splashdown, Grumman Aerospace Corporation pilot Sam Greenberg (who had helped with the strategy for re-routing power from the LM to the crippled CM) issued a tongue-in-cheek invoice for $400,540.05 to North American Rockwell, Pratt and Whitney, and Beech Aircraft, prime and subcontractors for the CSM, for "towing" the crippled ship most of the way to the Moon and back. The figure was based on an estimated 400,001 miles (643,739 km) at $1.00 per mile, plus $4.00 for the first mile. An extra $536.05 was included for battery charging, oxygen, and an "additional guest in room" (Swigert). A 20% "commercial discount," as well as a further 2% discount if North American were to pay in cash, reduced the total to $312,421.24. North American declined payment, noting that it had ferried three previous Grumman LMs to the Moon (Apollo 10, Apollo 11 and Apollo 12) with no such reciprocal charges.
The command module shell was formerly at the Musée de l'air et de l'espace, in Paris. The interior components were removed during the investigation of the accident and reassembled into boilerplate BP-1102A, the water egress training module; and were subsequently on display at the Museum of Natural History and Science in Louisville, Kentucky, until 2000. The command module and the internal components were reassembled, and Odyssey is currently on display at the Cosmosphere in Hutchinson, Kansas.
The lunar module Aquarius re-entered Earth's atmosphere on April 17, 1970. Any surviving pieces fell into the deep ocean off the coast of New Zealand. Apollo 13's final midcourse correction had addressed the concerns of the Atomic Energy Commission, who wanted the cask containing the plutonium oxide intended for the SNAP-27 reactor to impact in a safe place. The LM's remains fell to Earth over the Tonga Trench in the Pacific, one of its deepest points, and sank 10 kilometers to the bottom. Later helicopter surveys found no radioactive leakage.
Popular culture and media
The 1974 movie Houston, We've Got a Problem, 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; only a couple of news clips and a narrator's solemn voice deal with the actual crisis. Lovell publicly complained about the movie, saying it was "fictitious and in poor taste."
"Houston ... We've Got a Problem" was the title of an episode of the BBC documentary series A Life At Stake, broadcast in March 1978. This was an accurate, if simplified, reconstruction of the events. In 1994, during the 25th anniversary of Apollo 11, PBS released a 90-minute documentary titled Apollo 13: To the Edge and Back.
Following the flight, the crew planned to write a book, but they all left NASA without starting it. After Lovell retired in 1991, he was approached by journalist Jeffrey Kluger about writing a non-fiction account of the mission. Swigert died in 1982 and Haise was no longer interested in collaborating on a book. The resultant book, Lost Moon: The Perilous Voyage of Apollo 13, was published in 1994.
The next year, in 1995, a film adaptation of the book, Apollo 13, was released, directed by Ron Howard and starring Tom Hanks as Lovell, Bill Paxton as Haise, Kevin Bacon as Swigert, Gary Sinise as Mattingly, Ed Harris as flight director Gene Kranz, and Kathleen Quinlan as Marilyn Lovell. James Lovell, Eugene Kranz, and other principals have stated that this film depicted the events of the mission with reasonable accuracy, given that some dramatic license was taken. For example, the film changes the tense of Lovell's famous follow-up to Swigert's original words from, "Houston, we've had a problem" to "Houston, we have a problem". The film also invented the phrase "Failure is not an option", uttered by Harris as Kranz in the film; the phrase became so closely associated with Kranz that he used it for the title of his 2000 autobiography. The film won two of the nine Academy Awards it was nominated for, Best Film Editing and Best Sound.
In the 1998 miniseries From the Earth to the Moon, co-produced by Hanks and Howard, the mission is dramatized in the episode "We Interrupt This Program". Rather than showing the incident from the crew's perspective as in the Apollo 13 feature film, it is instead presented from an Earth-bound perspective of television reporters competing for coverage of the event.
In 2008, an interactive theatrical show titled Apollo 13: Mission Control premiered at BATS Theatre in Wellington, New Zealand. The production faithfully recreated the mission control consoles and audience members became part of the storyline. The show also featured a "guest" astronaut each night: a member of the public who suited up and amongst other duties, stirred the oxygen tanks and said the line "Houston, we've had a problem." This "replacement" astronaut was a nod to Jack Swigert, who replaced Ken Mattingly shortly before launch. The production toured to other cities extensively in New Zealand and Australia in 2010–2011. The production traveled to the US and performed 45 shows in 2012.
The "mailbox" at Mission Control during the Apollo 13 mission
The crew on board the USS Iwo Jima following splashdown
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