Yep, there are a couple of catches in the system. First,
today is really cold for this area. It is under 32 degrees
Celsius. A cold wave, complete with thunderstorms. We
watch a wall of water cross mountains and sheet across
desert valleys. Lightning is seen from miles away. Yes,
we were told we were coming to one of the hottest and
driest places on Earth and I am in a long sleeve shirt
under my rain jacket.
The weather is affecting our challenge. The plastic
tubing we have is pretty stiff in this temperature.
Yesterday, when it was warmer, the tubing was quite
malleable. In this “cold”, our motorized
pump isn’t strong enough to smush the plastic
tubing sufficiently to squeeze the water through it.
When we heat the tubing briefly over Mike B's fire,
the system pumps the water just fine… it better
be warm tomorrow!
We also needed to test to see if the pump was strong
enough to force water through a long system of tubing.
This is where things get fuzzy - my botany and ecology
training don’t provide much insight. (I run into
these types of situations regularly, so I have been
taking physics-related courses on things like light,
sound, electricity, magnetism, and astronomy for the
past couple years in order to better understand how
the world works. I still didn’t know how to think
about this situation, though.)
Does the length of tubing, thus the length of the water
column, affect the amount of force needed to make the
What matters more, the total volume of water in the
loop or the length of the water column?
Is there a critical tube diameter for which water adhering
to the tube will over take cohesion of water molecules,
thus keeping the water from moving?
Does the system need “priming”? In other
words, is an exceptional amount of force needed to start
the water circulating, compared with the amount of force
needed to maintain the system once it is started?
How many air bubbles are too many? How much air in the
system is too much?
Unless someone just knows the answers to questions
like these while we are doing the project, we have to
experiment to find out. We dealt with question 1, which
quickly lead to others...
We didn’t know if the pump could circulate water
through a long length of tube, so we mocked up a long
tube, about 10 m, and tried to completely fill it with
water. With Kate at our side we turned the pump on.
Nothing. The pump wheel went around, but the water didn’t
move. There were lots of air bubbles, however. Some
were quite large. Jonathan wondered if an airlock was
preventing water movement. We took the connecting piece
out of the loop. It was easy to suck water through the
tube, but quite hard to get the water moving by blowing
into the tube. Our pump was equivalent to blowing into
We refilled the tube, this time ensuring as few air
spaces as possible by keeping the funnel feeding water
into the tube constantly full and having one of us sucking
on the other end of the tube. (Don’t ever put
your mouth on something unless you are sure of what
it is and where it’s been. In this case, we were
using tubing we had washed. We were filling it will
drinking water and food colouring, so we felt it was
safe.) We basically flushed water through the tubing
until the person sucking on the tube encountered no
more air spaces. We also inspected the tubing, which
was intentionally transparent, for air bubbles. We ended
up with one air bubble about two centimetres long. Good
enough. Having one relatively small air bubble allowed
us to easily determine if water was moving through the
system when the pump was on. Yes, indeed, with a full
tube of water and a warm tube, the pump circulated water
without issue. So we learned if we minimised the amount
of air in the tube, our pump was forceful enough to
pump water through a long tube (about 10 meters of tubing).
We then tested to see if tight coils restricted water
circulation—they didn’t as long as flow
was restricted. We also tested to see if the pump could
pump water upwards against gravity. The water would,
after all, have to travel against gravity at least a
couple of feet as I am 6 feet tall before heading back
down into the fridge. No problem.
As we ended up with a working system, we didn’t
delve much farther into our questions or try to tease
out the different components. There just wasn’t
With extra screwdriver batteries recharging, we went
on to design the actual tubing system for the fridge
and spacesuit. We ended up with a long series of copper
tubing coils in the fridge, so the water would have
lots of time to cool. We connected this by short sections
of clear plastic tubing covered by a second plastic
tube wrapped in aluminium foil to a set of zigzagging
copper tubing designed to cool the astronaut’s
body core - the trunk. We chose the core of the body
because the extremities have a lot of surface area and
thus release heat to the atmosphere quite quickly anyway.
Plus, it is the body core that really needs to function
effectively to keep the astronaut alive and well. If
you take a look at how we positioned the zigzags, we
avoided areas of fat and concentrated contact between
lean parts of my body core and the cooling system. This
should make the cooling system more efficient, because
fat is a great insulator and that’s not what we
want in this situation.
Also, if the fridge had been likely to produce freezing
temperatures, we would have probably set the system
up differently and cooled the core slowly by reducing
the heat in the body extremities first. But since the
fridge wasn’t working at all as a fridge at the
end of day two, we weren’t particularly worried
about shocking the astronaut’s system or causing
hypothermia. Though Kathy, Iain, and Mike had a good
vacuum seal and honest-to-goodness zeolite, no real
cooling is taking place in the fridge.
(I was chosen as the astronaut to test the spacesuit
and cooling apparatus merely because I fit into the
spacesuit materials we were given. Who planned this?
Thus, I am wondering if I should be slightly concerned
about keeling over with heat stroke in Death Valley
tomorrow. I am counting on K, I, and M to figure out