RANDOLPH AIR FORCE BASE, Texas –
At first glance the large steel box looks like the enlarged and possibly exaggerated part of an action figure toy from the 1980s, but a closer look reveals it's more complicated and much more simple.
The steel box, commonly called a hypobaric chamber, can produce the effects of flight up to about 25,000 feet without ever leaving the ground. The physics governing how the large machine works are simple and similar to a common vacuum cleaner--only on a much larger scale.
From both inside and outside the chamber, Airmen from the 359th Aerospace Medicine Squadron watch over the students in the chamber.
Airman 1st Class Kristen Coffey, 359th AMDS, aerospace operations physiology, said the chamber is for training personnel and aircrew for the effects altitude has on the human body, whether it's unpressurized aircraft, rapid decompression or other situations with lower than normal air pressure.
In aircraft and in the chamber, the air pilots and aircrew breathe contains none of the nitrogen found in air at lower elevations. Breathing pure oxygen reduces the risk of decompression sickness.
Staff Sgt. Vikas Kumar, 359th AMDS, NCO in charge of maintenance. "We train them for hypoxia, or the lack of oxygen" in their system.
The symptoms of hypoxia become more acute at about 10,000 feet and can include mental confusion, nausea, passing out, lack of visual acuity and cyanosis, or the bluing of finger tips and lips. The time of useful consciousness diminishes with altitude, to about three to five minutes at 25,000 feet for an average person.
He said they have different types of training for different airframes and the training for first-time students is different than the refresher training pilots receive every five years.
During the flights, students sit along the long sides of the chamber facing each other. In front of each seat is a small control panel with three different types of oxygen mask connectors for different aircraft and applications, including the connector for an ejection seat.
"We put them in a working environment like in the aircraft," Airman Coffey said. "They're not just sitting around."
She said in an actual flight, the aircrew isn't sitting idle; they're busy working on the things that keep the aircraft aloft. To keep the students' minds churning and to test for hypoxia, they do worksheets with basic arithmetic and other exercises. Sergeant Kumar referred to the worksheets as "brain bubblegum" because of their simplicity.
One end of the chamber has a steel door which leads to a small air lock compartment, similar to what one may see in a science-fiction movie. Beyond the air lock is the main part of chamber. On the opposite end is a reinforced window, through which the controls for the chamber are visible.
Three Airmen from the 359th AMDS sit outside the chamber on elevated chairs keeping watch as well as controlling the flights. One observer listens and takes notes about what happens in the chamber during a flight while another speaks with the inside observers, who keep an eye on the flight from inside the chamber. All of the observers were in communication with each other.
The control panel has lights, levers and dials to control and monitor the atmosphere in the chamber.
Below the panel between two of the seats is a long, red lever attached to an emergency dump valve.
Sergeant Kumar said the valve almost immediately regulates the pressure in the chamber with the atmosphere outside in case of an emergency.