Suds in Space
|Tweet|Suds in Space Bubbly, frothing and ticklish -- soft drinks and
beer promise a welcome taste of home to faraway space travelers.
September 21, 2001: People can endure many discomforts in exchange for the thrill of living in space. The nausea of space sickness, fitful sleep without the familiar pressure of a bed, tasteless meals eaten from plastic bags -- it's all fine as long as the novelty of being in space lasts.
But after a while, the blush of excitement inevitably fades,
and astronauts will begin to long for the comforts of home. For
example, the nose-tickling bubbles of a refreshing soft drink
or a frothy beer after work -- these simple pleasures that we
take for granted on Earth could do wonders for morale among long-term
Above: A fizzy Coca-Cola droplet floats aboard the Space Shuttle in August 1985. In a weightless environment, bubbles of carbon dioxide ("carbonation") aren't buoyant, so they remain randomly distributed in the fluid. The result can be a foamy mess!
For the tradition of beer and its fizzy cousins to continue
as people begin settling space, a few questions must first be
Will fermentation work the same in weightlessness? What happens to carbonation when there's no buoyancy to bring the bubbles to the top? Can space beer form a proper head? Scientists who study the physics of gas-liquid mixtures would love to know!
Two separate space shuttle experiments tackled these questions. Both were engineered and mediated by BioServe Space Technologies, a NASA-sponsored Commercial Space Center at the University of Colorado at Boulder. NASA's Space Product Development (SPD) program encourages the commercialization of space by industry through 17 such CSCs.
Left: Probably the oldest carbonated
beverage still consumed today, beer has a long and rich tradition.
Kirsten Sterrett, recently a University of Colorado graduate student, first became interested in how beer would brew in space while working at the Coors Brewing Company. Having studied aerospace engineering as an undergraduate, she began to wonder: How would yeast that perform fermentation fare in orbital free fall? The answer would not only shed light on the possible makings of space-beer, but also provide valuable information to pharmaceutical companies with a keen interest in the biology of orbiting microbes.
When she returned to CU-Boulder for her master's work, she
chose the topic for her thesis. Her experiments
were sponsored by Coors and flown on the shuttle with the help
"I always said I wouldn't do an experiment that I couldn't eat or drink in the end," she jokes.
"Actually, after the experiment was all done, I gave (the space-beer) a little taste." The sample was only about 1 ml, which wasn't really enough to savor, she says, "but why throw something like that away?"
Along with her taste test, Sterrett performed a protein analysis on the beer and the yeast, measured the beer's specific gravity (the force exerted on it by gravity per unit volume), and "repitched" the yeast by brewing subsequent batches of beer with it. By all of these measures, the space-beer appeared to be essentially the same as beer brewed on Earth.
Below: A far cry from the copper vats used to brew beer here on Earth, this Fluid Processing Apparatus was used by Sterrett to ferment a tiny batch of space-brew. [more information]
The behavior of the yeast was somewhat puzzling, though. The
total cell count in space-borne samples was lower that of "control"
samples brewed on the ground, and the percentage of live cells
was also lower. One of the yeast's proteins also existed in greater
amounts in the space-brew.
Sterrett's experiment couldn't suggest reasons for these changes, but the overly abundant protein bears some resemblance to a general stress protein.
The low cell count was particularly surprising, says Sterrett. In space, yeast cells remain evenly dispersed within the "wort" -- a brewers' term for the pre-fermentation mixture of water, barley, hops, and yeast. Ideally, this would give the yeast cells better access to nutrients in the wort compared to similar mixtures on Earth, where the weight of the cells causes them to pile at the bottom one on top of the other.
"It's the same question that we're asking on the pharmaceutical side," says Louis Stodieck, director of BioServe. "We know from subsequent space experiments sponsored by Bristol-Myers Squibb Pharmaceutical Research Institute that the efficiency of producing fermentation products increases [in a weightless environment], in fact quite significantly." Some of those experiments produced as much as three times the fermentation products as control samples on the ground.
Pharmaceutical companies frequently use genetically-engineered microbes -- usually bacteria -- to produce medicinally-valuable proteins such as antibiotics through fermentation. By introducing the gene that codes for the protein into the bacteria's DNA, scientists convert the microbes into inexpensive, self-replicating medicine micro-factories.
Space research with microbe fermentation might help improve this process.
Above: Yeast are tiny single-celled fungi important
for brewing beer and baking bread. Understanding the puzzling
behavior of such cells in space will benefit pharmaceutical research
here on Earth.
"What we're trying to do now is to find the specific mechanism of that (increased fermentation efficiency in space), and then we can ask whether we can modify the fermentation process on Earth to take advantage of that -- or is it possible that we could genetically engineer an organism to mimic what it does in space," Stodieck says.
A more efficient fermentation process, even by a small percentage, could potentially save millions of dollars in production costs.
Below: "Sitting down to dinner" as these astronauts are doing on the International Space Station can mean floating above the table while snacking on unfamiliar foods. Small pleasures like a soda or a beer might be a welcome taste of the ordinary for out-of-this-world diners.
For beer, of course, increased fermentation
efficiency means a more alcoholic brew -- not necessarily good
news for crew members who need to remain sober in the dangerous
environment of space. The alcohol content of space-brews would
need to be adjusted accordingly and, of course, consumed in moderation.
But for alcohol content to even matter, future space residents will first have to get the beer into a drinking container -- a trickier feat than it may seem.
"How do you dispense a beverage and keep the carbonation in solution until the person is ready to drink?" Stodieck asks. "That's the challenge."
Changes in temperature and pressure, or even physical agitation of the beverage as it's dispensed, can cause carbonation to come out of solution prematurely. Because bubbles don't rise in free-fall the result can be a foamy mass.
This problem was addressed by experiments flown on the shuttle by The Coca-Cola Company, again with the help of BioServe. "They (The Coca-Cola Company) have a lot of technology that they develop for future ways of providing their drinks anywhere and everywhere," Stodieck notes. And indeed, their dispensing device flown on the shuttle managed to serve a drinkable cola. It controlled the temperature of the beverage during mixing and dispensing with computer accuracy, and minimized agitation.
Above: By dispensing the drink into a collapsible bag inside the bottle, the pressure around the fluid can be constantly controlled, thus preventing the carbonation from coming out of solution too quickly. The image on the right shows the dispenser being used aboard the space shuttle. Note the tape stuck to the top-right corner of the dispenser that reads "50¢" -- astronaut humor. Image courtesy BioServe.
Similar technology should prove effective for carbonated space
beers. Unfortunately it doesn't lend itself to the traditional
frosty glass mug! Instead, beverages are dispensed into a special
bottle (pictured above) that screws onto the dispenser. The bottle
itself, which contains a collapsible bag, is internally pressurized.
The pressure around the bag is slowly released as the beverage
enters, maintaining the drink under constant pressure and producing
a palatable soda or beer.
So maybe it's not exactly like having a beer on Earth, but astronauts might nevertheless welcome a sip from the strange contraption. Bubbly, frothing, and ticklish -- it's a welcome taste of home.
Space Product Development -- The commercial development of the space frontier is one of the greatest opportunities facing America. NASA is encouraging businesses to seize this opportunity through the Space Product Development Program and its Commercial Space Centers, to help ensure the continued economic growth of the U.S. and to bring the opportunities for new advances, technological understanding, products and jobs to the public.
NASA Space Commercialization -- learn more about NASA's efforts to increase the utilization of space for commercial product research
Commercial Space Center experiments aboard the ISS -- (MSFC press release) Three new commercial experiments are underway on the International Space Station, marking a major milestone for NASAs Commercial Space Centers.
History of Beer -- A website with information about the history of beer in society
In space, no one can hear you belch -- by science writer Dave Dooling.
Results Summary from 3rd Student Parabolic Flight Campaign 2000 -- (ESA) includes an experiment on beer tapping in free fall.
Beer balls -- (New Scientist) Future residents of the International Space Station could be toasting Christmas with a draught beer.
Making Antibiotics in Space -- Science@NASA article about experiments on the shuttle that looked into how micro-gravity affects the production of antibiotics by microbes.
Bizarre Boiling -- Science@NASA article about another shuttle experiment that examined liquid-gas mixtures in space.
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