午夜福利1000集合

IN LATE October, the European Space Agency beat NASA to a crucial objective.
Just a week before the first long-term inhabitants of the International Space
Station blasted off to begin their dry stretch 400 kilometres above the surface
of the Earth, ESA got to grips with the properties of beer in a zero-gravity
environment.

Europe鈥檚 scholars seem to have a firm grasp on the serious issues of space.
Five years ago, a team from Delft University of Technology in the Netherlands
invented and tested a zero-gravity pizza table, based on the action of a
domestic vacuum cleaner. Space station engineers watched closely: they were
considering it as a solution to the problem of sitting down to a meal in
space.

Now a group of aerospace students from the same institution have plugged
another gap in the catering arrangements. Just in time for Christmas,
they have answered a crucial question: can you wash down your
pepperoni-and-mushroom with a draught beer? After all, it鈥檚 going to be
difficult for space station staff to get home for the holidays, and a cold beer
might just help ease the pain.

But how do you pour a beer in zero gravity, where there is no 鈥渦p鈥�? And even
if you can overcome this challenge, will it stay gassy鈥攅ssential for the
taste鈥攐r will the bubbles float out and leave the beer flat? Will you get
a smooth head of foam? Most importantly, how do you get the beer into your
mouth?

The first stage of the project was to find a suitable delivery system.
Conventional technology forces the beer out by injecting a gas鈥攗sually
carbon dioxide鈥攊nto the barrel. But in zero gravity the liquid would float
around inside the barrel, so what comes out of the tap might be as much gas as
beer. The researchers also realised that at the low pressure prevailing on the
space station, the perfect gas pressure would be hard to find. As terrestrial
bar staff know very well, too much or too little carbon dioxide can whisk the
beer into an undrinkable foam.

Fortunately, three and a half years of research at Delft, in collaboration
with Dutch company ENL, has now produced the ideal barrel. 鈥淚t has a flexible
membrane, which contains the beer, inside the barrel,鈥� says Kajsa van Overbeek,
the project supervisor. 鈥淣ormal air is pumped between the barrel wall and the
membrane to force the beer out.鈥� Pressurise the container, open the tap, and out
pours the nectar of the gods. So far, so good.

The next thing the students needed was a zero-gravity party venue. So Veele
Sterken, the Delft project leader, and her colleagues took their barrel up on
ESA鈥檚 鈥渧omit comet鈥�. This is a plane that flies in a series of controlled
parabolas, giving 30 seconds of free fall each time. So as not to leave the
plane smelling like a beer cellar, the students kept their keg in a 鈥済lovebox鈥�,
a sealed, transparent plastic box with gloved hand-holes for manipulating the
equipment inside.

Of course, this meant that they couldn鈥檛 drink the beer, but that didn鈥檛 stop
them from succumbing to a common party ailment. There were 30 parabolas in each
flight, and on her turn Sterken was throwing up for 25 of them. With hindsight,
warm beer might have been a relatively pleasant aroma.

All the upset was worth it, though. The results couldn鈥檛 have been better.
The team didn鈥檛 even have to pump extra air into the barrel, because the
pressure in the plane was lower than that down on Earth, where they set the
equipment up. They simply opened the tap and the beer poured itself.

It came out in balls, almost identical in size, each as big as a ping-pong
ball. That鈥檚 about a mouthful. You couldn鈥檛 ask for a better measure. 鈥淲e didn鈥檛
catch it in a glass or anything, we just let it sit in microgravity,鈥� Sterken
says. It鈥檚 a poetic image: spheres of beer floating in space, just waiting to be
drunk. All an astronaut has to do is grab a straw and suck.

There was just one thing which disappointed the students. They didn鈥檛 get
their two fingers of foam on top of the beer. 鈥淭he bubbles stayed inside the
ball of beer: they didn鈥檛 move at all,鈥� says Sterken. No big surprise, says
Ramaswamy Balasubramaniam, of NASA鈥檚 Glenn National Center for Microgravity
Research on Fluids and Combustion: 鈥淚t would be difficult to form a foam because
the bubbles don鈥檛 rise.鈥�

But there鈥檚 a silver lining. The very fact that the bubbles stayed in the
beer should be great for the taste, Sterken claims. The carbon dioxide fizz
helps swirl the beer around the taste buds, and lifts the volatile scents and
flavours to the back of the throat, enhancing the taste experience. Its acidity
also cleans the bitter taste of the beer from the tongue.

On the other hand, if you could somehow encourage a frothy head to
form鈥攑erhaps by careful use of a centrifuge鈥攊t would last longer
than ever. On Earth, gravity drains the liquid from the foam, causing the
bubbles to dry out and burst. This wouldn鈥檛 happen in zero-gravity, so your beer
would be frothy to the last drop.

There might be one small problem: the internal effects of the carbon dioxide
bubbles. They can balloon inside the stomach if the external pressure changes,
and belching is not easy in zero gravity: the gas just sits in the stomach
(New Scientist, 25 January 1997, p 24).
But astronauts have drunk Coca-Cola
on board Mir without doing themselves any harm, so how bad can it be? And NASA
has already tested Alka-Seltzer in zero-gravity, so there鈥檚 no need to worry
about your hangover.

So there鈥檚 no reason at all why there shouldn鈥檛 be a great party atmosphere
on the space station next Christmas. In fact, why wait? Get talking to the
breweries, Houston. With a shuttle on the launch pad, surely there鈥檚 room to
stow a small keg under the commander鈥檚 seat?