As part of the preparation for future Lunar and Martian missions, NASA has selected COMEX to conduct a series of hypobaric tests dedicated to astronaut denitrogenation prior to planetary extravehicular activities (xEVA). This strategic partnership confirms COMEX’s position as a global reference player in the simulation of extreme environments and the conduct of human subject testing.
A critical challenge for future space missions
Before any extravehicular activity (EVA), astronauts must eliminate dissolved nitrogen from their bodies in order to prevent the risk of decompression sickness. This denitrogenation phase currently relies on long and demanding protocols, requiring several hours of uninterrupted breathing of pure oxygen.
While these procedures have proven effective aboard the International Space Station, they reveal their limitations in the context of future Lunar and Martian exploration missions, where EVAs will be more frequent and available resources more constrained. NASA is therefore working on the development of new denitrogenation protocols, notably based on reduced-pressure, high-oxygen atmospheres, with the aim of improving both the safety and efficiency of extravehicular activities.
Why NASA selected COMEX
To validate these new protocols, NASA conducted a benchmark of European test centers capable of carrying out complex hypobaric experiments involving multiple subjects simultaneously. COMEX stood out as the only laboratory combining all of the following capabilities:
- ✓a large-volume hypobaric chamber capable of accommodating up to five people,
- ✓highly qualified teams specializing in hyperbaric and aerospace medicine,
- ✓regulatory approval from health authorities to conduct human subject testing.
These unique capabilities led NASA to select COMEX to replicate and complement the tests conducted at the Johnson Space Center in the United States.
Hypobaric testing closely replicating real xEVA conditions
The tests conducted at COMEX consist of a six-hour denitrogenation phase during which participants breathe 100% oxygen, followed by physical exercise sessions performed in a hypobaric chamber simulating an altitude of 9,200 meters (approximately 30,200 feet), still under pure oxygen, corresponding to the operating pressure typically used in the Extravehicular Mobility Unit (EVA) suit, approximately 4.3 psi (0.3 atm).
Volunteers perform a range of effort scenarios representative of extravehicular activity constraints, including stair climbing at varying paces, arm ergometer exercises, object handling, and fine motor skills tasks. An ultrasound station is also used to detect in real time the possible formation of nitrogen bubbles within the body.
Numerous parameters are continuously monitored, including pressure (altitude), breathing gas composition and concentration levels, phase durations, temperature, and humidity, in order to collect essential biomedical data for protocol validation.
Close collaboration with NASA teams
The collaboration between COMEX and NASA was built on a foundation of transparency and scientific rigor. NASA teams visited the COMEX site on multiple occasions to prepare the test campaigns and ensure that the protocols applied were strictly identical to those used at the Johnson Space Center.
In parallel, COMEX teams were trained on-site at the Johnson Space Center in Houston in both equipment operations and test protocol implementation.
Data are shared with NASA in real time and subsequently analyzed jointly. At the end of each test campaign, a detailed report is delivered within short timeframes, contributing to the rapid advancement of ongoing research efforts.
International recognition and strategic perspectives
This first series of tests enabled NASA to officially validate COMEX as a test laboratory for xEVA simulation. COMEX is also the first of the selected centers to have successfully completed this campaign in its entirety, demonstrating its ability to meet the requirements of such a prestigious and demanding client.
Building on these results, NASA has already scheduled a second large-scale test campaign, with several dozen tests planned for 2026, aimed at identifying the most suitable denitrogenation protocol for astronauts involved in future exploration missions.
Profiles selection that meets spatial requirements
The conduct of these hypobaric trials relies on the participation of volunteers whose physiological characteristics are comparable to those of astronauts involved in NASA’s human spaceflight programs. The medical criteria applied are particularly stringent and include, in particular, excellent cardiovascular fitness, high aerobic capacity, the absence of cardiac or respiratory contraindications, and proven tolerance to confined environments.
These scientific requirements, which are essential to ensuring both the safety of the trials and the validity of the data collected, naturally limit the number of suitable profiles and represent one of the major challenges of this type of research involving human subjects. The trials are carried out within a rigorous ethical and regulatory framework, with continuous medical monitoring and real-time measurement of key physiological parameters such as pressure and respiratory gases.
COMEX continues its research activities in this field and remains available to respond to any institutional or scientific requests for information.
An exceptional scientific and human adventure
Beyond its scientific outcomes, this project is a great source of pride for COMEX teams. The mobilization of physicians, engineers, technicians, and project managers with a shared passion for space exploration made it possible to meet a complex challenge within tight timelines, in service of human space exploration.
Through this strategic partnership, COMEX once again confirms its ability to leverage its longstanding expertise in extreme environments to address the most ambitious challenges of international research.
