Shallow-Water Nitrox Diving, the NASA Experience - NASA Technical Reports Server (NTRS) ## NTRS ## NTRS - NASA Technical Reports Server Search Collections About News Help Login Back to Results Shallow-Water Nitrox Diving, the NASA ExperienceNASA s Neutral Buoyancy Laboratory (NBL) contains a 6.2 million gallon, 12-meter deep pool where astronauts prepare for space missions involving space walks (extravehicular activity EVA). Training is conducted in a space suit (extravehicular mobility unit EMU) pressurized to 4.0 - 4.3 PSI for up to 6.5 hours while breathing a 46% NITROX mix. Since the facility opened in 1997, over 30,000 hours of suited training has been completed with no occurrence of decompression sickness (DCS) or oxygen toxicity. This study examines the last 5 years of astronaut suited training runs. All suited runs are computer monitored and data is recorded in the Environmental Control System (ECS) database. Astronaut training runs from 2004 - 2008 were reviewed and specific data including total run time, maximum depth and average depth were analyzed. One hundred twenty seven astronauts and cosmonauts completed 2,231 training runs totaling 12,880 exposure hours. Data

# Are suits in the NBL pressurized differently than during flight? Tags: spacesuits, eva - Score: 17 - Views: 1676 - Answers: 2 - Answered: yes - Asked by: Erin Anne (21262 rep) - Asked: 2024-01-31 - Site: space ## Question I don't know why I've been in a spacesuit mood lately, but the following crossed my mind recently: the flexible portions of NASA'S EMU suits are inflated by the interior pressure the suits in the National Buoyancy Lab (NBL) are underwater water pressure exceeds the nominal flight pressure of 4.3 psi at a relatively shallow depth, yet the NBL suits stay inflated Is the atmosphere in a suit in the NBL different than it would be in space? The closest post I found while looking here was Are the EVA suits used in the ISS and in the NBL same or different? ## Answers ### Answer by Erin Anne (score: 20) I managed to stumble across the answer while trying to decide how to ask this question, and I thought it was interesting, so Oxygen exposures at NASA's Neutral Buoyancy Lab: a 20-year experience, Walker et al, 2018 states that the NBL suits run "a 46% nitrox mixture" at "pressures exceeding 2 atmospheres absolute (ATA)". The entire abstract is fairly interesting

# Are the EVA suits used in the ISS and in the NBL same or different? Tags: iss, spacesuits, eva - Score: 16 - Views: 2141 - Answers: 1 - Answered: yes - Asked by: Vishnu (3386 rep) - Asked: 2019-11-06 - Site: space ## Question Are the space suits used in the International Space Station (ISS) and in the Neutral Buoyancy Lab (NBL) same or different? They look similar, but they are used in two different media - one in a vacuum environment and the other underwater. Is the one used in NBL waterproof, or the EVA suits are generally waterproof by design (especially the electronics, since water and electronics are bad friends)? ## Answers ### Answer by Organic Marble (score: 27 [ACCEPTED]) The suits used in the NBL are Class III "training only". The Display and Control Module (control panel on the chest), the life support backpack, and the SAFER self-rescue unit are mocked-up. Breathing air is supplied via an umbilical and bouyancy weigh-outs are added to the exterior of the suit. So: the soft goods (arms, legs, gloves, boots), the helmet, and the Hard Upper Torso are flight-like, but not the working parts. Source: https://www.semanticscholar.org/paper/Extravehicular-Mobility-U

Astronauts training for extravehicular activity (EVA) operations can spend many hours submerged underwater in a pressurized suit, called an extravehicular mobility unit (EMU), exposed to pressures exceeding 2 atmospheres absolute (ATA). To minimize the risk of decompression sickness (DCS) a 46% nitrox mixture is used. This limits the nitrogen partial pressure, decreasing the risk of DCS. The trade-off with using a 46% nitrox mixture is the increased potential for oxygen toxicity, which can lead to severe neurologic symptoms including seizures. Suited runs, which typically expose astronauts of 0.9-1.1 ATA for longer than six hours, routinely exceed the recommendation for central nervous system oxygen toxicity limits (CNSOTL) published by the National Oceanic and Atmospheric Administration (NOAA). Fortunately, in over 50,000 hours of suited training dives spanning 20 years of EVA training operations at NASA's Neutral Buoyancy Laboratory (NBL) there has never been an occurrence of oxygen toxicity. This lends support to anecdotal sentiment among certain members of the hyperbaric community that the NOAA CNSOTL recommendations might be overly conservative, at least for the oxygen pressure and time regime in which NBL operates. The NOAA CNSOTL recommendations are the result of expert consensus with a focus on safety and do not necessarily reflect rigorous experimental evidence. The data from the NBL suited dive operations provide a foundation of evidence that can help inform the expert discussion on dive-related neurologic oxygen toxicity performance and overnight recovery in young, healthy males.