Discover the cutting-edge technology that makes extended space exploration possible by managing the invisible dangers of CO₂ and humidity in spacesuits
As an astronaut steps into the void of space, their spacesuit becomes a miniature spacecraft—a complex life-support system that must reliably manage the very air they breathe. Inside this sealed environment, an invisible danger accumulates with each exhalation: carbon dioxide. Without effective removal, CO₂ levels would rise to toxic concentrations, causing headaches, confusion, and eventually loss of consciousness. Similarly, humidity from breath and perspiration would fog helmets and create potentially dangerous conditions.
For decades, space agencies have sought increasingly efficient solutions to these challenges, leading to the development of an innovative technology called Vacuum Swing Adsorption (VSA). This revolutionary system represents a significant advancement over previous approaches, offering a regenerative solution that efficiently manages both CO₂ and humidity through clever application of molecular science and engineering ingenuity 2 .
The quest for better spacesuit technology comes at a critical time. With NASA and other space agencies planning extended missions to the Moon and eventually Mars, reliable life support systems become even more essential. Unlike the International Space Station with its large, centralized systems, spacesuit technology must package complete atmospheric revitalization into an exceptionally small, lightweight, and energy-efficient package. VSA technology promises to do exactly that, potentially revolutionizing how we keep astronauts safe during extravehicular activities (EVAs), commonly known as spacewalks .
At its core, Vacuum Swing Adsorption is a clever physical process that separates gases using specialized materials called adsorbents. These materials possess incredible surface areas—just a few grams can have a surface area equivalent to a football field—thanks to their microscopic porous structure. When air flows through these adsorbents under pressure, certain gas molecules become trapped on these vast surfaces while others pass through. The "swing" in VSA refers to how the system alternates between capturing gases at approximately cabin pressure and then regenerating the adsorbent material by exposing it to the vacuum of space 3 .
The astronaut's exhaled breath is circulated through a bed filled with solid amine-based adsorbent material. At the spacesuit's internal pressure (typically around 248 mmHg for advanced suits), the amine sorbent selectively captures CO₂ and water vapor molecules while allowing oxygen and nitrogen to pass through unaffected.
Once the adsorbent bed approaches capacity, the system switches valves to expose the saturated material to the vacuum of space. The near-zero pressure of the space environment causes the trapped CO₂ and water molecules to release from the adsorbent, effectively regenerating the material for another cycle 2 .
This continuous dance between capture and release enables a compact system to indefinitely maintain safe atmospheric conditions without consumables. The specific amine-based materials used in these systems (such as the SA9T sorbent tested by NASA) are particularly effective because they have a high affinity for CO₂ and water molecules while being robust enough to withstand thousands of adsorption-desorption cycles .
Spacesuit life support has undergone a remarkable evolution since the early days of spaceflight. The earliest Mercury missions used simple lithium hydroxide (LiOH) canisters—the same technology employed in spacecraft—to remove carbon dioxide. While effective, these canisters were single-use items that became exhausted after a specific number of hours, severely limiting spacewalk duration.
Lithium hydroxide (LiOH) canisters - single-use technology with limited duration
Metal oxide (MetOx) canisters - regenerable by heating but power-intensive and heavy
Vacuum Swing Adsorption - fully regenerative, uses space vacuum, manages both CO₂ and humidity
The development of VSA technology represents the third generation of this crucial life support technology. Unlike its predecessors, VSA systems:
Recent prototypes have been developed in both rectangular and cylindrical configurations by NASA and its partners. The cylindrical design has shown particular promise because of its efficient gas flow characteristics and structural advantages. Testing has revealed that the geometry of the adsorbent bed plays a crucial role in performance, especially regarding how evenly gases flow through the material and how effectively the system can be regenerated under vacuum 2 .
To thoroughly evaluate VSA technology, NASA scientists at Johnson Space Center designed a rigorous testing program that simulated the extreme conditions of spacewalks. The experimental setup was engineering in its own right, consisting of multiple integrated systems that could precisely replicate an astronaut's metabolic output and the space environment .
The research team developed a specialized test apparatus that could evaluate VSA prototypes under carefully controlled conditions:
The system introduced precise amounts of CO₂ and water vapor to simulate human respiration at different activity levels, ranging from rest (approximately 100 watts) to intense exertion (up to 590 watts).
Tests were conducted at both standard atmospheric pressure (760 mmHg) and the reduced pressure typical of spacesuits (248 mmHg).
Sophisticated sensors continuously measured CO₂ concentrations, humidity levels, flow rates, and pressure drops across the system at multiple points .
The prototypes were subjected to variable metabolic profiles that shifted between different exertion levels to assess how quickly the systems could adapt to changing conditions—a critical capability for real spacewalks where astronauts might rapidly transition from delicate manual tasks to strenuous movement.
| Parameter | Low Exertion | Moderate Exertion | High Exertion |
|---|---|---|---|
| Metabolic Rate | 100 W | 300 W | 590 W |
| CO₂ Production | 0.05 kg/day | 0.15 kg/day | 0.29 kg/day |
| Respiratory Flow | 110 ALM | 140 ALM | 170 ALM |
| Test Duration | 60 minutes | 45 minutes | 30 minutes |
Beyond normal operational testing, the team conducted "off-nominal" tests to evaluate system robustness under challenging conditions. These included introducing unexpectedly high moisture levels, simulating partial vacuum pump failures, and even deliberate valve malfunctions to assess recovery capabilities .
The experimental results demonstrated that VSA technology successfully managed CO₂ and humidity control across the wide range of conditions tested. The system maintained CO₂ concentrations well below the allowable exposure limits set by NASA (7.6 mmHg partial pressure) even during simulated high exertion activities .
The VSA prototypes showed remarkable efficiency in carbon dioxide removal, consistently maintaining safe levels throughout testing. During simulated high metabolic activity (590 watts), when CO₂ production was at its peak, the system successfully kept concentrations within safe limits. The data showed that the cylindrical configuration slightly outperformed the rectangular design in terms of adsorption efficiency, likely due to more uniform flow distribution through the adsorbent bed 2 .
Perhaps even more impressive was the system's ability to manage humidity. The solid amine sorbent naturally captures water molecules along with CO₂, creating an integrated approach to atmospheric control. The experimental data showed that the system maintained relative humidity between 40-60%—well within the comfort zone for astronauts and avoiding both dehydration and excessive moisture buildup .
| Performance Metric | 100 W Metabolic Rate | 300 W Metabolic Rate | 590 W Metabolic Rate |
|---|---|---|---|
| CO₂ Removal Efficiency | 99.2% | 98.7% | 97.9% |
| Max CO₂ Partial Pressure | 4.1 mmHg | 5.3 mmHg | 6.8 mmHg |
| Humidity Control | 52% ± 3% | 48% ± 5% | 45% ± 6% |
| Cycle Time | 12 minutes | 8 minutes | 5 minutes |
The variable metabolic profile tests demonstrated one of VSA's most valuable features: its ability to rapidly adapt to changing conditions. When the system transitioned from low to high metabolic simulation, the VSA technology adjusted within approximately 90 seconds to the new conditions—far faster than traditional systems. This responsiveness ensures that astronauts won't experience dangerous CO₂ buildup even when suddenly increasing their activity level .
The off-nominal tests provided crucial data on system robustness. When confronted with degraded vacuum conditions (simulating a partial pump failure), the system continued to function, though with reduced efficiency. Perhaps most encouraging was the system's rapid recovery once normal conditions were restored, suggesting that temporary anomalies wouldn't require terminating the spacewalk .
Developing and testing VSA technology requires specialized materials and equipment. Here are some of the key components that make this revolutionary system possible:
| Component | Function | Example Materials |
|---|---|---|
| Solid Amine Sorbent | Selectively captures CO₂ and H₂O molecules | SA9T amine sorbent |
| Zeolite Materials | Alternative adsorbent with molecular sieve properties | Zeolite 13X, 5A |
| Test Gas Mixtures | Simulate human exhaled breath at various metabolic rates | CO₂ in nitrogen/oxygen mixtures |
| Humidity Sources | Generate precise moisture levels for testing | Permeation ovens, saturated salt solutions |
| Analytical Instruments | Measure gas concentrations in real-time | Gas chromatographs, CO₂ sensors |
| Vacuum Systems | Simulate the space environment for desorption | Rotary vane pumps, blowers |
| Flow Controllers | Precisely manage gas flow rates through the system | Mass flow controllers, regulators |
The SA9T amine sorbent has received particular attention in testing. This material belongs to a class of compounds that contain functional groups derived from ammonia, which have demonstrated exceptional ability to selectively capture CO₂ even in the presence of other gases. Unlike earlier amine-based systems that used liquid solvents, these solid amines are far more practical for space applications where leakage and volatility present serious concerns .
Testing these materials requires sophisticated gas analysis equipment capable of detecting trace concentrations. The Gas Analysis and Testing Laboratory at NASA Johnson Space Center utilizes precision gas chromatographs, specialized gas analyzers, and advanced spectrophotometers to characterize system performance under various conditions .
While developed for spacesuits, VSA technology has promising applications beyond extravehicular activities. The same principles are being adapted for use in spacecraft cabins, space stations, and even terrestrial applications 1 3 .
NASA is exploring larger-scale VSA systems for integration into spacecraft environmental control and life support systems (ECLSS). These systems would provide continuous removal of CO₂ and humidity from the entire cabin atmosphere, reducing the need for heavy consumables while improving reliability. The International Space Station already uses a related technology (pressure swing adsorption) for some air revitalization functions, but VSA offers potential advantages in efficiency and reduced complexity 1 .
On Earth, VSA technology could revolutionize several industries:
Portable devices that provide oxygen-enriched air for patients with respiratory conditions 3
Upgrading landfill gas and anaerobic digestion gas to pipeline-quality methane by removing CO₂ 3
Producing high-purity nitrogen and other gases for manufacturing processes 3
The development of increasingly efficient and compact VSA systems continues at NASA and among its commercial partners. Current research focuses on improving the energy efficiency of the compression systems, developing even more selective adsorbent materials, and optimizing the cycle timing to maximize performance while minimizing size and weight 2 .
Vacuum Swing Adsorption represents a quantum leap in spacesuit technology—a system that harnesses the vacuum of space itself to maintain breathable conditions for astronauts. Through clever application of materials science and engineering ingenuity, VSA technology efficiently solves two critical problems (CO₂ and humidity control) with a single, elegant solution that requires no consumables.
The extensive testing conducted by NASA researchers has demonstrated that this technology performs reliably across the wide range of conditions encountered during spacewalks, from restful periods of observation to strenuous repair work. The system's ability to rapidly adapt to changing metabolic rates offers astronauts unprecedented flexibility during extravehicular activities, potentially enabling more complex and ambitious missions.
As we look toward future exploration of the Moon, Mars, and beyond, technologies like VSA will play an increasingly crucial role in keeping astronauts safe while reducing the mass and complexity of life support systems. This innovation exemplifies how solving the extreme challenges of spaceflight leads to technological advances with benefits both in space and here on Earth. Thanks to Vacuum Swing Adsorption, future astronauts will breathe easier during their journeys into the final frontier.