Grappling with controls at the door of a full-size mock-up of the Space Shuttle's cargo bay, a NASA astronaut is supported by a team of standby divers in the Neutral Buoyancy Simulator, a very big training pool, at Marshall, Alabama. Mike Seares went to Marshall to film trials of a mixed gas rebreather (worn by the diver in the foreground) which NASA may adopt for its tank work.
The current in-word in diving has to be 'Tek'. Diving is changing and, used sensibly, mixed gases and rebreathers will enhance the enjoyment, safety and capability of sport divers. With this in mind, I am producing a documentary for The Discovery Channel on the development of the Phibian rebreather, which uses a highly developed gas control system. For filming we've looked at numerous applications, from commercial diving to cave diving, marine archaeology and underwater photography. But one of the most spectacular uses of the Phibian to date has to be in trials by NASA for training astronauts, who practise tasks underwater for many hours, to simulate the weightlessness of space.
I visited NASA's Marshall Space Flight Centre in Alabama, where its Neutral Buoyancy Simulator (NBS) is based, and for several days filmed Stuart Clough of Carmellan Research, developer of the Phibian, training astronaut support divers in the use of the rebreather.
Housed in a large, grey building, the NBS is a huge circular tank, 23m wide and 12m deep, with gantries at three levels and viewing ports all round. It is capable of housing full-size mock-ups of the Shuttle cargo bay and satellites that may require maintenance in space. For instance, training takes place soon for servicing the Hubble Space Telescope.
The water is of gin-like clarity and heated to the temperature of a hot bath. Cylinder filling posts are placed all around the tank - and a fully manned recompression chamber sits just metres away. Every club should train like this!
Before we could join NASA's divers in the tank, we faced a Class 3 US Airforce medical - like an HSE Part IV medical with a few bells and whistles - conducted by the worryingly named Dr Dye. And if the medical seemed a bit over the top, we were also told to visit paramedics each morning for computer blood-pressure analysis!
Safety is of paramount concern to NASA for obvious reasons, and since the Challenger disaster a regime of safety has been more fervently instilled in all employees at every level.
After marvelling at the tank's technology and obvious lack of financial restraint, we filled our cylinders, signed our names into a dive log and signalled to the control room by intercom that we were about to dive.
Despite a rule banning buoyancy compensators - on the grounds that a rescue diver with an over-inflated BC could lose grip on, and drop, an astronaut - I was allowed to enter the tank wearing my own, well travelled and loved BC.
Peering down, I was stunned by the water, so clear that it might not have been there at all, and the enormous proportions of the tank around me. Below lay the full-size mock-up of the Space Shuttle cargo bay, together with a remotely-controllable manipulator arm, extending above the cargo deck like a mechanical snake.
Finning out across the tank and just submerging, I floated down on to the end of the arm, placing fins where space suit boots would go, and imagined how it must feel to be up there in space, the Shuttle below me and the Earth beyond.
Suddenly the Shuttle didn't seem that big after all. In the vastness of space it must seem like a tiny protective haven, your only connection to what you know and understand.
I moved off the arm and descended to film the Phibians in action. Although bulky, the Phibian is easy to swim with, the main difference from scuba being the fact that there is no change in buoyancy during the breathing cycle. As I filmed, the rebreather-clad standby divers seemed to enhance the tank's simulation of outer space, the absence of bubbles eliminating any close reference point, while the background seemed so far off.
From NASA's point of view, rebreathers would allow the stand-by divers to stay down as long as the "suited subjects", as the astronauts are called, which can be as long as 6 hours. In addition, the lack of bubbles would enable clearer filming by the 14 cameras mounted on the tank walls or held by the divers. If trials go well, there is also the possibility that rebreathers could be installed in astronauts' underwater backpacks, to replace umbilicals.