Coffee in space: how astronauts drink and the first espresso on the ISS

Why coffee in orbit is a physics problem

Of all the stories about coffee and coffee machines, the most unusual one we know takes place around four hundred kilometres above our heads, aboard the International Space Station.

On Earth it is obvious that coffee stays in the cup, flows into the mouth when the cup is tilted and keeps its crema on top. All of this works because of gravity. In orbit its effects all but disappear, because the station and everything inside it are falling together around the planet.

With no "down", a free liquid gathers into a floating sphere held together by surface tension. It cannot be poured, it does not settle at the bottom, and if the container is tilted it either stays where it is or breaks loose and drifts through the cabin.

What you cannot see changes too: heat no longer spreads by natural convection, bubbles do not float to the surface, and a foam, instead of draining, simply stays put. For anyone who works with espresso, these are exactly the phenomena that decide the crema.

Here we explain how astronauts really drink, how the capillary cup works and how Italian espresso reached orbit in 2015. The story of the espresso machine on Earth is told in our post on the birth of espresso.

How drinking really works on the space station

The astronauts' practical answer is simple: no cups. Drinks, coffee included, arrive on board as powder, sealed in laminated foil pouches fitted with a one-way valve.

When it is time to drink, the pouch is attached to the water dispenser in the station galley, which injects a measured amount of hot or ambient-temperature water through the valve. The contents are mixed, a straw is inserted and the drink is sipped straight from the pouch.

The straw has a clamp that is closed between sips; otherwise the liquid would keep coming out and form free-floating spheres in the cabin.

The system is safe and light, but it removes almost all of the pleasure of the familiar gesture. The two ideas below were born from that gap.

The cup that works by capillary action

The first idea was born on board. In 2008 a NASA astronaut, tired of drinking from pouches, used a sheet of transparent plastic film to build a teardrop-shaped cup with a narrow angle along its wall. The principle is the one that makes water climb a thin tube: capillary action.

In that narrow corner, capillary forces move the liquid up to the rim, where they settle into equilibrium. When the lips take a sip, the equilibrium is broken and more liquid rises from the bottom, until the cup is empty with about as much residue as a ceramic cup leaves on Earth.

The prototype was later refined by American researchers together with NASA, and in 2015 a set of 3D-printed cups went up to the station for an experiment dedicated to beverages, at the same time as the espresso machine. For NASA the subject goes beyond breakfast: the same principles are used to move liquids without pumps in tanks and life-support systems.

ISSpresso: the first espresso in orbit is Italian

The second idea was born in Italy. ISSpresso is the capsule espresso machine designed by Argotec, an Italian aerospace engineering company, together with Lavazza, the Turin roaster, in partnership with the Italian Space Agency.

It was one of the experiments of the ASI's Futura mission, in which ESA astronaut Samantha Cristoforetti took part. The machine was launched in April 2015 aboard a Dragon cargo capsule, which Cristoforetti herself captured with the station's robotic arm.

On 3 May 2015 Samantha Cristoforetti prepared and drank the first espresso in history in weightlessness, a date that entered the official record books.

The way it works resembles a home machine, with a few differences. The water does not come from a tank but from a pouch connected to the machine; the capsule goes into a compartment; the coffee does not flow into a cup but into a standard NASA drink pouch, from which it is sipped through a straw or transferred into the capillary cup.

For safety, the hydraulic circuit is made of steel rather than plastic and rated for pressures far above anything a home machine reaches, and the unit weighs around twenty kilograms. Besides espresso, the capsules can make a long coffee, tea and broth.

ISSpresso stayed in orbit for more than two years. For us, selling machines and capsules every day, it remains a point of pride: the espresso that left Earth speaks Italian.

What it teaches us about espresso at home

Behind the symbol there was also a scientific question: how does a hot liquid under high pressure behave without gravity, and what happens to the foam. For coffee that question has a precise name: crema.

Espresso exists because hot water passes through ground coffee under pressure in a matter of seconds. The pressure extracts oils and aromatic compounds and releases the carbon dioxide trapped in the beans by roasting; those tiny bubbles, dispersed in the liquid, form the crema.

On Earth the crema rises to the surface. In orbit the bubbles have no "up" to move towards and stay distributed through the coffee: one of the reasons the experiment also interested engineers who work with fluids.

A good machine must keep water pressure and temperature stable for the whole extraction; a suitable capsule or grind must offer the right resistance. If one of these conditions is missing, the crema is thin and the taste flat, with or without gravity.

What the crema contains, and why it is not in itself a guarantee of quality, is explained in our post on the chemistry of coffee.

An espresso with its feet on the ground

The coffee you drink at home has an advantage the astronauts do not: gravity works in its favour.

If the story of ISSpresso has caught your interest, the natural starting point is the Lavazza catalogue: original A Modo Mio® capsules, capsules compatible with other systems, ESE pods and coffee beans.

For a compact machine, the Lavazza A Modo Mio® machines section lists the models for Lavazza's own capsule system, while the A Modo Mio® compatible capsules include blends from Maracatú, Borbone, Toraldo and Lollo as well as instant drinks.

If you prefer to grind your own or use a moka pot, the coffee beans and ground coffee department carries blends from several Italian roasters, and the espresso machines section covers capsule and pod systems from various brands.

If you are unsure which machine or blend suits your habits, contact us: the Maracatú team will gladly help you choose, with both feet firmly on the ground.

Image: Italy seen from the International Space Station, NASA.