Zero G Brew Dynamics

The Italian Space Agency has collaborated with engineers and coffee makers to create an expresso machine for astronauts on the International Space Station, the ISSpresso. Although not a lot...
ISSpresso. Photo from NASA
ISSpresso. Photo from NASA

The Italian Space Agency has collaborated with engineers and coffee makers to create an expresso machine for astronauts on the International Space Station, the ISSpresso.

Although not a lot bigger than a normal capsule espresso machine, the ISSpresso weighs more than 20 kilos. This is in part because stainless steel has replaced plastic tubing so the equipment can operate at 400 bars of pressure (5800 pounds per square inch). In contrast, home capsule machines on terra firma operate at up to 20 bars. It is also water tight so the crew will not be endangered by drops of beverage floating in microgravity.

NASA estimates the cost to get something into earth orbit at around US$22,000 a kilo (US$10,000 a pound) although they are trying to get these costs down to hundreds per kilo/pound by 2040 and tens of dollars by 2055. In the meantime, this means a delivery cost of more than US$500,000 for the packaged ISSpresso. The cost for an individual capsule of around US$100 is at least less than its weight in gold.

However as ISS researcher Mike Weislogel has explained, it is also part of ongoing fluid dynamics research. On Earth it is taken for granted that bubbles rise and liquids fall. But without gravity this does not happen and surface tension becomes dominant in fluid behaviour. On the ISS this means liquids can be floating anywhere in their container and affects many aspects such as fuel systems, cooling systems and water processing. Astronauts need to suck liquids from a pouch with a straw to ensure all contents are consumed which is hardly conducive to the enjoyment of a good espresso.

Recent research has resulted in a ‘Zero-G coffee cup’. This is a curved pouch without any straight lines. Rather than sipping or pouring coffee into the mouth, it works when its opening is placed on the lips. The liquid then moves by capillary action, such as when water is soaked up by a paper towel. Pictured here, courtesy of NASA, is the the ISSpresso’s installer, Italian Air Force Captain Samantha Christoforetti, enjoying a brew with a zero g cup in the ISS cupola. A Star Trek uniform is entirely optional for those enjoying a freshly brewed espresso after a hard day spacewalking.

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Annabelle is a sci fi aficionada living in Brisbane, Australia whose favourite outdoor activity is taking a book outside to read.
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