Coca-Cola and Pepsi test soda in space

In 1985, Coca-Cola and Pepsi sent specially designed cans of their beverages into space aboard the Challenger shuttle during the STS-51F mission, also known as Spacelab 2. The experiment aimed to test whether astronauts could drink carbonated beverages in microgravity.

Space soda experiment fails due to physics

The mission failed not due to taste or astronaut preferences, but because of a fundamental physical principle: in the absence of gravity, carbon dioxide does not separate from the liquid, creating an unstable foam that made the drinks undrinkable. The drinks also became warm because the shuttle lacked refrigeration.

Companies invest in different can designs

Coca-Cola invested about $250,000 in a sophisticated can design featuring a plastic laminate pouch containing the soda, coupled with a pressurized carbon dioxide bladder designed to expel the liquid through a metal valve and a spout. Pepsi, on the other hand, adapted an existing container, which would have initially cost $14 million to develop.

Soda tasting was not the mission’s main focus

The two systems were eventually placed aboard the Challenger shuttle for the STS-51F mission, launched from the Kennedy Space Center. However, the experiment was a secondary attraction compared to the scientific module Spacelab 2, the primary purpose of the mission.

Astronauts found the soda unpalatable

Mission pilot Roy D. Bridges Jr. described the experience as disappointing, noting that the soda was warm and "neither was very good." The astronauts eventually opted for Tang, a powder that could be mixed with cold water, which was easier to consume. Not all astronauts participated in the tasting; John-David Bartoe, a payload specialist, refused to take part, considering the operation frivolous and contrary to the scientific rigor expected of the mission.

Launch delay highlights spaceflight challenges

The initial launch of the Challenger was interrupted at T-3 seconds due to a failed cooling valve on engine number two, causing an emergency stop of the three main engines. This setback highlighted the extreme precision required for space flights.

Carbonated drinks banned on the ISS

The failure of the experiment led to the prohibition of carbonated beverages aboard the International Space Station, due to the risk of damaging equipment and causing digestive issues. NASA justifies this prohibition with two main arguments: the potential damage to onboard equipment and the risk of serious digestive problems caused by the inability of liquid and gas to separate in microgravity.