The Apollo 13 Disaster

As the successful Apollo 11 mission had fulfilled the promise of the 1961's President Kennedy promise in July 1969 and that another mission of the Apollo program had reached Moon in November 1969, a third Moon mission, the Apollo 13, launched to our satellite on April 11th, 1970 aboard its Saturn V from the KSC (Complex 39-A). James Lovell Jr, John Swigert Jr, Fred Haise Jr were the crew as mission target was the Fra Mauro area

Emergency

As the mission was on its translunar journey, and moments after they finished a TV broadcast late on April 13, 1970, a spark ignited one of the oxygen tanks on the Apollo 13 spacecraft. The resulting explosion was the beginning to a anxious three-and-a-half day drama followed worldwide. The explosion had caused both oxygen tanks to fail and also led to a loss of electrical power. 'Houston, we’ve had a problem here,' astronaut Jack Swigert told mission control in Houston at what was then NASA’s Manned Spacecraft Center (now Johnson Space Center). “We’ve had a main B bus undervolt,” Mission Commander James Lovell said. A 'main B bus undervolt' indicated there had been an abrupt power loss from one of the command-service module's two main electrical systems. 'Roger, main B undervolt,'said capsule communicator. 'OK, stand by, 13. We’re looking at it.' The communications loops were chaotic for about 60 seconds as seven caution and warning lights were on in the command module. Never until now a failure in one system had gone across so many different systems. A crew looked out the window and saw the oxygen escaping from the remaining tank at the spacecraft rear end, and they took conscience that the mission was now in serious trouble. A fault in the electrical system of the Service Module's oxygen tank No. 2 produced an explosion that caused both oxygen tanks to fail. the command module's supply of power, light and water was lost

Rescue

Less than two hours after the emergency message was transmitted to Houston, mission control pronounced the command module mortally wounded. With only 15 minutes of power left, astronauts Swigert, Jim Lovell and Fred Haise escaped to the 'ife boat' of the lunar module and shut down the Command Module. The Command Module remained functional on its own batteries and oxygen tank, but these were usable only during the last hours of the mission. At that moment the crew was 200,000 miles (320,000 km) from the Earth. NASA eventually came up with five return-to-Earth options. The one chosen was to perform a 30.7-second firing of the LM's descent engine to put the spacecraft on a return trajectory, looping around the Moon and gaining a boost from the lunar gravity. The descent engine was used again two hours after the closest approach to the moon's surface. But reorienting the lunar module to a return-to-Earth trajectory from a lunar landing course proved to be one of the most difficult and important obstacles to hurdle. Navigation and targeting functions were unavailable. Debris from the explosion made it impossible for the crew to navigate by the stars using the on-board sextant. In a nail-biting maneuver, the astronauts improvised by using the limb of Earth, or the horizon where Earth meets the atmosphere, as a reference point. They were then able to perform a controlled fuel burn to shorten the time until splashdown on Earth. President Richard Nixon learned of the crisis shortly after the explosion

Challenges

The crew spent in all three-and-a-half grueling days in the lunar module. They rationed food and water, which mission designers had only intended to last two men a day and a half -or the duration of sojourn at Moon's surface- not three men three days. Carbon dioxide was eventually to reach dangerous levels in the lunar module. When the crew shut the instruments off to conserve power, the inside temperature reached an icy 38 F. With the support from contractors and universities, the flight control team demonstrated considerable ingenuity under pressure, overcoming the challenges of low power, limited water and lack of other consumables as they created workarounds for each challenge. The question of limited breathable air was the following. Lithium hydroxide (LiOH) canisters in the LEM were used for removing carbon dioxide from the air as they were not sufficient to support the three-person crew during the four-day return as the lunar lander was designed to support two crew members only, those actually landing on the Moon. They were canisters enough in the Command Module but these were cube-shaped with the LM's canisters cylindrical. The team of engineers improvised a way to join the CM canisters to the LM's cylindrical canister-sockets by drawing air through a space suit hose

On April 17, 1970, the crew successfully splashed down in the Pacific Ocean near Samoa, by 1:07 p.m. EST. The day after the splashdown, President Richard Nixon awarded the Presidential Medal of Freedom to the crew and the Apollo 13 Mission Operations Team for their unyielding efforts during the mission

Causes

In 1965, the command module had undergone many improvements that 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 had not been modified to suit the change. During one final test on the Apollo 13 launch pad, the heaters were on for a long period of time, which subjected the wiring in the vicinity of the heaters to very high temperatures (1,000 degrees F), which were subsequently shown to have severely degraded the Teflon insulation. The thermostatic switches started to open while powered by 65 volts DC and were thus probably welded shut. Furthermore, other warning signs during testing went unheeded and the tank, damaged from eight hours of overheating had become a potential bomb the next time it was filled with oxygen. One of two fuel cell oxygen tanks in the service module had exploded. Damaged Teflon insulation on the wires to the stirring fan inside oxygen tank 2 allowed the wires to short-circuit and ignite the insulation. The fuel cells generated the command-service module's electrical power by combining oxygen and hydrogen. When the oxygen tank ran dry, the remaining fuel cell shut down, leaving only the CM's limited-duration battery power