Apollo 13 - Lithium hydroxide saves the day

Note: these articles have been published in InfoChem, the supliment to Education in Chemistry produced by The Royal Society of Chemistry.

1970 and Apollo 13 blasts-off successfully on the third mission to land on the Moon. Two days out and 200,000 miles from Earth, however an oxygen tank ruptures, damaging other tanks and the spacecraft's electrical system in the Command Module (CM) ... prompting the crews immortal lines "Houston we've had a problem". For the three spaceman the mission now is to save their lives and get back to Earth safely. You can follow the Hollywood telling of the story in Apollo 13, Tom Hanks plays commander Jim Lovell [1].

It appears that a heater and stirrer in the oxygen tank did not turn off correctly creating explosive pressures leading to the accident. Fortunately it exploded out into space rather than into the spaceship but it meant the astronauts were now in a critical situation. The crew moved into the Lunar Module (LM) and used these resources as a 'lifeboat'. Without this option they would almost certainly have died.

After considering all the possible return paths they fired the available engines to get the correct trajectory - it would take four days to get home. The LM was designed for two people for two days not three people for a four day trip home, so they had very limited electrical power, heating and drinking water. They had enough oxygen for the trip but the critical issue was carbon dioxide.

Normally about 0.04 % of air is CO2. As it rises it causes our respiratory rate to increase but high levels can lead to headaches, confusion and eventually loss of consciousness [2]. About 3% of expired air is CO2, so in a small space such as the LM, the levels will quickly rise. The LM used cylindrical canisters of Lithium hydroxide (anhydrous) in the air circulating system to remove carbon dioxide (lithium carbonate is produced):

2 LiOH + CO2 → Li2CO3 + H2O

However, they did not have enough canisters to support the crew for four days. The CM had adequate supply but unfortunately these units didn't fit the equipment in the LM, they were the wrong shape. The crew had to 'lash-up' a device to solve this problem using a space suit hose, cardboard, tape and the extra canisters. After a nail biting blackout period as the lunar module re-entered the Earth's atmosphere, the LM and her crew splashed-down safely in the Pacific. Despite all the complex trajectory calculations, engine firing and computer 'reboots' on the way home, the crew ultimately survived due to the little canisters of LiOH.

References and Links
[1] Apollo 13, Columbia, 1995.
[2] Life at the Extremes, Frances Ashcroft, Flamingo, 2001


How teachers can use these articles in a lesson

Why Hollywood Science

Open University Hollywood Science web site

Call for clips - do you have a film clip that needs investigating?


Dr Jonathan Hare, The University of Sussex
Brighton, East Sussex. BN1 9QJ.

home | diary | whats on | CSC summary | latest news