“Houston, we’ve had a problem,” were the words of Apollo 13 astronaut Jim Lovell when an explosion crippled the spacecraft and threatened the lives of the crew. What started as a terror that threatened their lives and for days gripped the attention of the world became one of the great adventures of manned spaceflight, now 50 years ago this month.

Apollo 13 was to be the third attempt by NASA astronauts to land on the Moon. Apollo missions were manned by three astronauts taking off from Cape Canaveral, Florida. Once they reached the Moon, a lunar module would detach from a command module. The lunar module would reach the surface where two astronauts would then explore the surface, collect rock samples, and conduct experiments. The command module would orbit above, with the lunar module reattaching to the command module after taking off from the lunar surface. Once they returned to Earth, a re-entry capsule would detach from the command module for the descent through the atmosphere to a splashdown in the Pacific Ocean.

The three astronauts for the mission were: Jim Lovell, Fred Haise, and Jack Swigert. Lovell and Haise would be in the lunar module. Lovell was born in Cleveland, Ohio, in 1928 and graduated from the U. S. Naval Academy in 1954. He had previously flown in space twice before, including the Gemini 7 mission in 1965, which set a record of fourteen days in orbit. Haise was born in Mississippi in 1933 and completed a degree at the University of Oklahoma in 1959 before being selected as an astronaut in 1966. Astronaut Ken Mattingly was originally supposed to fly the command module, but NASA flight surgeons grounded him after he was exposed to German measles, replacing him with Swigert. Swigert was born in Denver, Colorado, in 1931. As a teenager, he saved money from a paper route to pay for flying lessons, gaining a pilots license at age 16. After he graduated from the University of Colorado, he joined the air force in 1953.

They launched on April 11, 1970. The astronauts had each spent more than 1,000 hours training for the mission, which had been delayed a month. Two days into the mission, NASA ground controllers noticed a malfunction and asked the crew to activate the stirring fans in the oxygen tanks of the service module within the command module. These tanks were the source of air and electricity for the command module. Investigators later determined that damaged wiring had short-circuited, igniting insulation, and causing an explosion.

NASA ground controllers quickly realized the danger of the situation and scrambled to save the lives of the astronauts. The astronauts had to shut down the command module and move into the lunar module to have enough air to survive. Instead of turning the craft around, NASA decided to let the momentum of the craft carry it to the Moon and slingshot back to Earth, which would take four days.

A team of ground controllers, scientists, and engineers from across the globe worked around the clock to work around the problems of the crippled capsule. Every second and every piece of equipment counted. For what everyone knew, no help could come rescue Apollo 13 – they had to rely on the information supplied from Earth. The smallest miscalculation could be fatal.

Temperatures plunged to 38 degrees inside the module, and the crew had to quickly improvise a device to filter out the building levels of carbon dioxide they were exhaling.

The final challenge was a 21-second engine thrust to put it back on course for a safe re-entry. Though ground controllers supplied all the numbers the crew needed, astronauts had to time the engine burn perfectly and angles themselves properly, using only the growing image of the Earth in a window. The maneuver was successful, and the crew splashed down safely on April 17.

In the process, what initially was a near disaster instead became one of the greatest feats of navigation in history. Apollo 13 astronauts conducted a successful moonshot – only the fifth time ever that had ever been completed with a manned crew – and completed a journey of more than 500,000 miles on an unpowered Apollo capsule using only a couple of small thrusters and line-of-sight navigation.

Lovell credited ground controllers with saving their lives. There would only be four more manned lunar missions, with the last conducted by the Apollo 17 astronauts in December 1972.

Haise piloted the experimental Space Shuttle Enterprise on its Approach and Landing Tests in 1977 before retiring from NASA in 1979 and is still a Texas resident. Swigert left NASA in 1977 and won election to the United States House of Representatives from Colorado shortly before his death from cancer in 1982. Lovell left NASA in 1973 and became a telecommunications executive in the Houston area as well as a popular speaker and author. A small crater on the far side of the Moon is named for him. His 1994 book on the mission, Lost Moon, was the basis of the popular 1995 film Apollo 13. Lovell can briefly be seen in a closing scene of the movie shaking the hand of actor Tom Hanks, who portrayed him.

To date, no astronaut has flown further from Earth than the Apollo 13 crew.