Nowadays, the attention of the world’s population and the press are focussed on the COVID-19 pandemic. In a similar way, 50 years ago, the world was riveted to the drama of Apollo 13 when an oxygen tank exploded in the spacecraft carrying three astronauts to the moon.

It was President John F. Kennedy who challenged the US to put a man on the Moon. On May 25, 1961 Kennedy addressed a joint session of congress proposing that America “should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the earth”.

Man first reached the moon at Christmas 1968 when three astronauts, Borman, Lovell and Anders orbited around the moon. This was followed by Apollo 9 where tests were carried out in earth’s orbit. Apollo 10 was crewed by astronauts Stafford, Young and Cernan. This was a ‘dress rehearsal’ of a lunar landing with the lunar module descending to 15 kilometres above the moon surface with two astronauts aboard.

The Apollo flight was the first in which men landed and walked on the moon. The Apollo spacecraft was launched into space by the massive Saturn V rocket. The Saturn V was made up of three stages and it was 111 metres tall (18 metres taller than the Statue of Liberty) and weighed three million kilograms.

The Apollo spacecraft consisted of four separate parts. The command module (CM) houses the astronauts on their journey and is the only part that returns to Earth. It is attached to the service module (SM) which has a large engine and stores fuel, fuel cells and consumables.

The lunar module (LM) is the part that actually takes astronauts down to the moon and it consists of a descent stage which houses fuel and carries a rocket engine which brakes the descent of the craft against lunar gravity. The ascent module carries two astronauts and it has an engine which carries it up from the lunar surface to rendezvous with the orbiting command/service modules (CSM).

Michael Collins orbited around the moon in the CSM while Neil Armstrong and Buzz Aldrin were in the LM as it separated from the CSM to fall towards the moon. This first lunar landing was problematic because of computer alarms and, as they moved towards the landing site, Armstrong realised that they were headed for a field of boulders. He took manual control of the spacecraft to land safely with only seconds of fuel in reserve. Armstrong stepped on the moon on July 20, 1969 as he said: “That’s one small step for (a) man, one giant leap for mankind”.

The astronauts safely on the deck of the recovery ship USS Iwo Jima.

It has been called NASA’s ‘finest hour’ and the ‘successful failure’

Apollo 11 was followed by a successful Apollo 12 lunar landing and Apollo 13 was slated to be the third. Apollo 13 launched on April 11, 1970 with three astronauts on board.

James (Jim) Lovell was the commander. This was his fourth flight which included Apollo 10 mentioned above. He was the most experienced NASA astronaut at the time with 572 hours in space. Jack Swigert and Fred Haise were on their first flight. Swigert was part of the backup crew and he replaced Ken Mattingly at a late stage because Mattingly was exposed to measles and there was concern that he would be sick during the flight.

The first two days of the Apollo 13 flight were routine apart from one of the booster engines switching off early; however other engines burnt for a longer time to make up for this.

As they were coasting to the moon on April 13, 1970, an oxygen tank exploded. The astronauts felt a jolt and their instruments went haywire, showing that the pressure was decreasing in the oxygen tanks and the voltage of the fuel cells was dropping. Fuel cells generated electricity from the oxygen and hydrogen fuel stored in the service module. NASA flight controllers wondered whether there was instrument failure but shortly after Swigert reported: “Okay, Houston, we’ve had a problem”.

Lovell looked out of a window and reported “a gas of some sort” venting out into space and everyone quickly realised how serious the problem was. The CSM was dying and the astronauts quickly switched everything off and moved into the lunar module for safety.

The lunar module did not have enough resources to sustain three astronauts for four days until they returned to earth. Also, it did not have a heat shield and the astronauts would have to use the CM for re-entry. However, together with Mission Control, they worked on the problem.

A crude adapter was made to match canisters which absorbed carbon dioxide from the air from the CM to work in the LM. While there was enough oxygen and food, there was not enough water or electricity. The astronauts switched off most of the equipment. As they approached the moon and orbited it, they fired the LM rocket engine to leave the moon’s gravity to steer a course to earth.

There were also further firings to refine the trajectory. As they coasted back to earth, the astronauts were very cold and one of them developed a urinary tract infection.

Close to the earth, the exhausted astronauts jettisoned the LM and the SM as they switched on the instruments and warmed up the CM.

As they saw the SM floating away, the astronauts saw the magnitude of the damage and there were concerns that the heat shield was damaged and that the astronauts would burn up as they descended through the atmosphere. Fortunately, they landed safely on April 17, 1970.

The world’s population was gripped by the drama of this flight. Although the flight was a failure because it did not achieve a moon landing, it has been called NASA’s “finest hour” and the “successful failure” because of the way the crew and Mission Control battled through the many problems to bring the crew back home safely.

Gordon Caruana Dingli is chairman of the Department of Surgery at Mater Dei Hospital. He has had an interest in space flight for more than 50 years.