NASA Contractor Explains Why Space Shuttles Smelled Bad After Landing

Unpleasant odors inside NASA's Space Shuttle cabins became a problem for ground crews boarding the vehicles after landing to clean them and unload equipment. Dave Mohr, a NASA contractor, explained the cause in a Quora response, pointing to reduced environmental control performance, deteriorating stored food and waste, and stagnant air after the spacecraft returned to Earth.

According to Mohr, the shuttle's environmental control system became less effective at conditioning cabin air and removing odors once the vehicle was no longer operating in a vacuum. The situation worsened as the spacecraft remained on the runway and onboard systems gradually shut down.

Mohr gave an emphatic assessment of the odor problem in his explanation.

"The answer to this question is a 'YES!' in all capital letters!" said Dave Mohr, a NASA contractor.

The Space Transportation System, NASA's formal designation for the Space Shuttle, consisted of an orbiter, two solid rocket boosters and a large external fuel tank. The orbiter carried the crew, while the boosters supplied most of the lift during the first two minutes of flight.

Mohr identified the environmental control system's reduced effectiveness after landing as a key reason cabin odors accumulated. The system's ability to condition the air and remove unpleasant smells declined when the shuttle was no longer in its spaceflight environment.

"After landing, the operating capacity of the Environmental Control System was somewhat reduced by virtue of the vehicle no longer being in a vacuum. This reduced the effectiveness of the conditioning (and odor removal) of the cabin air." said Dave Mohr, a NASA contractor.

Stored food and waste added to the problem as time passed. Mohr explained that perishable supplies and other materials inside the vehicle could produce increasingly unpleasant smells while the cabin remained closed.

"All 'fresh food' and 'wet trash' stored in the vehicle (as well as other things) began to get pretty rank after a while." said Dave Mohr, a NASA contractor.

The shuttle's onboard systems also had a limited operating window after touchdown. Mohr said the vehicles he knew about were typically powered down between 45 minutes and one hour after landing because their onboard ammonia coolant was depleted.

He noted that the environmental system continued operating until the available ammonia was exhausted. A typical landing left approximately half an hour of ammonia remaining after the shuttle came to a stop, according to his account.

Mohr also addressed the relationship between the ammonia-based cooling system and checks for hazardous hydrazine. He explained that ground crews detected hydrazine by inserting a probe into the throat of each thruster, a process he said would not have been affected by the ammonia boiler.

"The stagnant air in the crew module was in really bad shape before very long." said Dave Mohr, a NASA contractor.

The Space Shuttle program used several orbiters, including Columbia, Challenger, Discovery, Atlantis and Endeavour. Columbia was delivered to NASA's Kennedy Space Center in March 1979, while Discovery arrived in November 1983 and Atlantis in April 1985. Enterprise was used for approach and landing tests but never flew in space.

NASA lost Challenger during ascent in January 1986 and Columbia during re-entry on February 1, 2003. Endeavour was built as a replacement following the Challenger accident and was delivered to Florida in May 1991.