Underwater EVA // Neutral Buoyancy EVA Simulation 2006, 2010
Edwin "Buzz" Aldrin's interest in scuba diving inspired the use of underwater EVA training to simulate weightlessness, which has been used ever since to allow cosmonauts, spationauts, astronauts, and taikonauts to practice techniques of avoiding wasted muscle energy.
Extra-vehicular activity (EVA) is work done by an astronaut away from the Earth, and outside of a spacecraft. The term most commonly applies to an EVA made outside a craft orbiting Earth (a spacewalk), but also applies to an EVA made on the surface of the Moon (a moonwalk). It can be tethered or untethered. On November 13, 1966, Edwin "Buzz" Aldrin became the first to successfully work in space without tiring, on the Gemini 12 last flight. Aldrin worked outside the spacecraft for 2 hours and 6 minutes, in addition to two stand-up EVA's in the spacecraft hatch for an additional 3 hours and 24 minutes. Aldrin's interest in scuba diving inspired the use of underwater EVA training to simulate weightlessness, which has been used ever since to allow astronauts to practice techniques of avoiding wasted muscle energy.
"Weightlessness" Analogue or Simulation underwater?
Weightlessness (or zero-g) is the condition that exists for an object or person when they experience little or no acceleration away from the acceleration that defines an inertial trajectory, or the trajectory of pure free-fall. An astronaut inside an orbiting vehicle has the experience of "zero-g," because the action and acceleration due to gravity by itself does not cause a sensation of weight, and all of the other types of forces that do cause such sensations (such as mechanical pushes from the floor or other surfaces that cause g-force acceleration) are absent. Weightlessness can thus be realised for short periods of time in an airplane following a specific parabolic flight path. It is simulated poorly, with many differences, in neutral buoyancy conditions, such as immersion in a tank of water.
Neutral buoyancy is a condition in which a physical body's mass equals the mass it displaces in a surrounding medium. This offsets the force of gravity that would otherwise cause the object to sink. An object that has neutral buoyancy will neither sink nor rise. The principle of neutral buoyancy is used to simulate the weightless environment of space. Astronauts experience no buoyant force and no rotational moment about their center of mass. One downside of using neutral buoyancy to simulate microgravity is the significant amount of drag presented by water. Generally, drag effects are minimized by doing tasks slowly in the water. Another downside of neutral buoyancy simulation is that astronauts are not weightless within their suits, thus, precise suit sizing is critical.
Tethered EVA Workshop
Extra-vehicluar activity protocol training in the lab with Canadian Astronaut Robert Thirsk
VA Tethering Workshop Dr. Sarah Jane Pell (AU), Dr. Robert Thirsk (CA), Tim Roediger (DE) and Xavier Giralt (ES); ISU SSP06 Life Sciences Practical Laboratory: Strasbourg, France 2006. Photos Ed Chester.
Movement, interaction and safety in neutral buoyancy is comparable to some extent to handling objects in microgravity and during EVA.
NASA Ames Pool, California 2010
SCUBA Tethered EVA simulation Crews egress outside the shuttle "airlock" and traverse along to repair a Blivet underwater on SCUBA while tethered and neutrally buoyant to demonstrate space walk training and experience some of the challenges of working outdoors in space. We found that tether useful for limiting his distance from the spacecraft, but difficult to use for moving around, and a significant entanglement hazard! Through-water communications and direct line of sight were also issues that teams had to work through.
EVA Lead & Space & Physical Space Science Co-Chair: Dan Barry, PhD, MD., President, Denbar Robotics, former NASA astronaut. Teaching Fellow: Tasha McCauley.
SCUBA Zero-G GSP10 Crew: Robert Denning, Jason Dunn, David Hutchison, Jan Jungclaus, Claudia Olsson, Dr. Sarah Jane Pell, Fabio Teixeira, Diva Tommei
Alcase Fire Dept Training Centre, France 2006
SCUBA Un-tethered EVA simulation Simulated requirements particular to a Hubble Repair mission were planned. Various astronaut crews ventured into the aqueous weightless environment to "fix the problem" to which a number of unplanned challenges occurred requiring effective communication, problem solving and teamwork to ensure the EVA was successfully completed and 'with in good time'. Our team won!
Life Science Dept activity led by Sheryl Bishop, Ph.D. (Assoc. Prof, Social Psychologist, University of Texas Medical Branch Galveston & Curriculum Director, Life Sciences faculty ISU) at the Summer Session Program at the International Space University, Strasbourg 2006. Teaching Associate Dr. Jessica Scott.