Keeping the Pressure On
While pressure is essential to astronaut survival, the pressure exerted
by a spacesuit does not have to match sea level pressure on Earth. If
the atmosphere inside a spacesuit is pure oxygen, a pressure equal to
about one third sea level pressure (about 33 kilopascals) is sufficient.
However, such low pressures require a several hour oxygen prebreathing
period to eliminate nitrogen from the spacewalkers blood stream.
If a higher suit operating pressure can be achieved, an astronaut can
don a suit and immediately exit the spacecraft for a spacewalk.
Operating pressures inside spacesuits are achieved by creating some sort
of pressure shell around the astronaut. The shell can be made of rigid
materials or a combination of fabrics provided they are nearly leakproof.
The pressure layer of the Space Shuttle spacesuit encase the astronaut
inside a human-shaped bag which has an inner layer of rubber and an outer
layer of nylon. The rubber contains the atmosphere and the nylon prevents
the rubber from inflating beyond a predetermined size and shape. Once
the suit is fully inflated, additional gas pressure supplied to the suit
pushes inward on the astronaut providing a livable pressure environment.
To demonstrate one method for creating a workable pressure
inside a spacesuit.
Materials and Tools Checklist
- 0.5 m ripstop nylon (available in fabric stores)
- Sewing machine
- Long balloon
- Bicycle pump with pressure gauge
- Small adjustable screw type, hose clamp
- Tire valve
Step 1. Using two pieces of ripstop nylon, stitch a bag as shown
in the pattern on the next page. The pattern should be doubled in
size. For extra strength, stitch the bag twice. Turn the stitched
Step 2. Slip the nozzle of a long balloon over the fat end
of the tire valve. Slide the other end of the balloon inside the
bag so the neck of the tire valve is aligned with the neck of the
Step 3. Slide the adjustable hose clamp over the bag and
tire valve necks. Tighten the clamp until the balloon and bag are
firmly pressed against the tire valve neck. This will seal the balloon
and bag to the valve.
Step 4. Connect the tire valve to the bicycle pump and inflate
the balloon. The balloon will inflate until it is restrained by
the bag. Additional pumping will raise the pressure inside the balloon.
Check the tire pressure gauge on the pump (use separate gauge if
necessary) and pressurize the bag to about 35 kilopascals (five
pounds per square inch). The tire valve can be separated from the
pump so that the bag can be passed around among the students.
Step 5. Discuss student observations of the stiffness of
the pressurized bag. What problems might an astronaut have wearing
a pressurized spacesuit?
Compare the technology for pressurizing spacesuits to
the technology for pressurizing automobile tires.
go to next page /
return to contents