FIELD JOURNAL

Touring the Neutral Buoyancy Lab --
Where the astronauts train for spacewalks

by Lori Keith
October 31, 2000

Welcome back! I always get excited when a new school year begins -- new routines, new classes, new teachers, new friends, and new experiences! Speaking of new experiences, several weeks ago I had the opportunity to visit the Neutral Buoyancy Lab, or what is commonly called the NBL. The NBL is where astronauts train in a huge pool to prepare them for many of their EVAs, or space walks. (EVA stands for extra-vehicular activity.) A new Space Team Online volunteer expert, David Hamilton, gave me a wonderful tour that I would like to share with you all.

The day I visited the NBL, the team was performing an engineering evaluation run with Claude Nicollier. The two umbilicals, or lines/hoses, running into the pool are connected to the astronauts -- supplying them with their communication, air, and their cooling. David tells me that the astronauts in the pool wear a suit called a LCVG, a liquid cooling and ventilation garment, which runs 37 degree chilled water through itself to provide automatic thermal control. This garment has little rubber hoses running through it so the cooled water goes across their bodies to extract the heat, preventing the astronauts from getting too hot. This is needed because the gas supplied to them gets rather warm, flowing through the hoses. The coolant running through the suits starts at 15 gallons per hour, but can be increased if the astronaut gets warm in the water. The communication capabilities allow them to talk to each other, the divers and the Test Conductors upstairs. Everyone in the water breathes a gas called Nitrox. Nitrox is a 45 percent oxygen (O2) mixture. The gas that we normally breathe is 21 percent oxygen. David says they mix their own gas (Nitrox), with the BGS system here at the Sonny Carter Training Facility, introducing more oxygen. (BGS stands for Breathing Gas System.) Then it is stored in the scuba tanks and into the big vats that feed the umbilicals. We mix a higher level of oxygen to prevent the divers and astronauts from getting sick while under the water - the bends (decompression sickness), nitrogen narcosis, or subcutaneous emphysema.

When you are in the water, your body is under pressure. As your body takes in gases, sometimes all the gas isn't absorbed and there could be a little bubble left. David explains that as the diver comes back up to the surface, the pressure on the body lessens and the bubble can expand, which causes the bends. This bubble usually locks up in a joint somewhere and is very painful. To try and keep that from happening, your body uses up the oxygen a lot better than it uses up the nitrogen. The nitrogen is usually the bubble with a little bit of oxygen left in it. The more oxygen introduced into the nitrox, the less likely a diver is to have a bubble. NASA's divers can't go down as deep with this higher oxygen percentage mixture, but they can stay down longer. A regular Nitrox mixture allows a diver to go down 100 - 140 feet. At this depth the higher oxygen level used at the NBL pool would cause oxygen toxicity, which would shut a person's body down.

The NBL pool is 40 feet deep, 102 feet wide and 202 feet long. It holds 6.2 million gallons of water and is the largest indoor swimming pool. The pool is built 20 feet below the ground and 20 feet above the ground. The walls of the pool are three feet thick, concrete and steel.

There are about 70 divers who work out of the NBL, three of them women. All are certified divers. David tells me to work at the NBL, you must be open water certified (C-card) in sport diving. Other things NASA is looking for is electrical and mechanical backgrounds. Then once hired, there is more NASA training, too. Divers must pass the NBL swim/certification test (using three strokes -- breaststroke, backstroke, freestyle; and a water-treading test.) Like flight controllers in the Mission Control Center, divers must train and then be certified in each duty station they sit/work. The different duty stations are safety diver, utility diver, camera diver, topside, hoist, crane operator, RMS (Remote Manipulator System) operator, BGS operator, ECS (Environmental Control System) operator, etc.

There are two robotics systems in the pool - the Shuttle Robotics Manipulator System (SRMS) and the Space Station Robotics Manipulator System (SSRMS). Both run on hydraulics. (Picture to the right shows elbow of SSRMS coming out of water) David tells me that this is what he does here -- he is the lead trainer for the robotics systems. He teaches the NBL people and the astronauts how to operate these systems. He points out that the robotic arm they are using in the pool to train with is made of titanium and costs about 16 million dollars to build -- and works exactly like the real one does on the space station.

There were about 15 people in the water, for the test being conducted, while I was visiting. During this time, the 2nd team divers were beginning their shift with the 1st team divers coming up. They change every two hours.

Most all astronauts come here before a flight, whether they are involved in EVA or not, to practice bailout training. Bailout training is needed in the event of an emergency abort right after lift-off where the astronauts need to be ejected out of the shuttle. If this happened, they would land in the ocean using a parachute and inflate a raft. Most of the crews we work with are either involved in operating the robotic arms or performing EVAs.

With quite a smile, and excitement in his voice, David tells me this is, by far, the best and most enjoyable job he has ever had. I think he has a pretty cool job, too. What do you think?

Here is a great place to learn more about spacesuits and EVA: http://quest.arc.nasa.gov/space/teachers/liftoff/eva.html#shuttle