In 1962, NASA packed 22,900 gallons of water into a Saturn I rocket and deliberately released it 65 miles above Earth to see how water behaved in the upper atmosphere

For humans to travel deep into space and remain there for months or even years, powerful rockets alone will not be enough. Astronauts will need reliable supplies of oxygen, water and food, while carbon dioxide and waste will have to be continuously removed or recycled.

On short missions, many of these necessities can be carried from Earth. But as spacecraft travel farther and missions last longer, transporting everything astronauts need becomes increasingly difficult and expensive. That has led NASA scientists for decades to investigate a fundamental question: could humans one day live in space using systems that recycle and regenerate the resources they consume?

NASA explored this problem long before plans for lunar bases and crewed missions to Mars became part of today's space agenda.


In 1962, for instance, the agency launched 22,900 gallons of water aboard a Saturn I test rocket and deliberately released the water-filled upper stage at an altitude of about 65 miles. The experiment, known as Project Highwater, was designed to study how a sudden release of a large quantity of water behaved at high altitude and affected the upper atmosphere.

Other research focused on a much bigger challenge — creating controlled environments capable of supporting human life for extended periods beyond Earth.

Historical reports available through NASA's Technical Reports Server show that researchers examined concepts involving closed environments, biological life-support systems and resource recycling. The broader goal was to determine whether living organisms and engineered systems could work together to reduce astronauts' dependence on supplies launched from Earth.

What would it take to live inside a closed space habitat?

Life on Earth is supported by interconnected cycles. Plants take in carbon dioxide and release oxygen, water moves continuously through the environment, and microorganisms help break down organic material.

A spacecraft or planetary habitat would not have access to these vast natural systems. Instead, almost every resource would have to be monitored, recovered and reused.

Astronauts would consume oxygen and produce carbon dioxide. They would use water and generate wastewater. Food would eventually become waste, while equipment and other materials would need to be managed within a confined environment.

For missions far from Earth, simply replacing these resources would become increasingly impractical.

This is why researchers began exploring closed-loop systems in which materials normally treated as waste could instead become inputs for another part of the system.

The objective was not necessarily to create a completely artificial version of Earth, but to reproduce selected natural cycles using a combination of mechanical, chemical and biological technologies.

Could plants become part of a spacecraft's life-support system?

Plants were among the most promising biological components researchers considered.

Through photosynthesis, plants consume carbon dioxide and produce oxygen. They can also provide food, making them potentially useful for more than one requirement of a long-duration mission.

In a carefully controlled habitat, astronauts could provide carbon dioxide and organic waste, while plants and microorganisms could help process some of these materials. Water and nutrients could potentially be recovered and reused, creating a more interconnected system.

Such a setup could eventually allow some of the resources consumed by astronauts to be regenerated rather than continuously replaced.

But researchers did not view plants as a simple replacement for machines.

A spacecraft would still need mechanical and chemical systems to maintain atmospheric conditions, purify water and handle waste. Biological components could instead complement those systems and reduce the overall amount of material that has to be transported from Earth.

The biggest problem: keeping the system in balance

Building a biological life-support system is far more complicated than simply growing plants inside a spacecraft.

Plants need appropriate levels of light, water, nutrients and temperature. Their growth can change over time and can be disrupted by disease or changes in environmental conditions.

Microorganisms could help break down waste and recycle nutrients, but they too would have to be carefully controlled.

The result would be a tightly interconnected system involving astronauts, plants, microorganisms and machines.

A change in one part could affect the others. If plants failed to grow properly, for example, the system could lose a potential source of oxygen and food. If a waste-processing system failed, nutrients and other materials could accumulate or become unusable.

Reliability would therefore be critical.

An astronaut travelling to Mars could not simply wait for a replacement system to arrive from Earth. This means biological life-support systems would need to operate alongside highly reliable mechanical and chemical systems, with enough redundancy to protect the crew if one component failed.

Why recycling resources could change space missions

Every kilogram launched into space comes with a cost.

Carrying large quantities of water, food and oxygen increases the mass of a spacecraft and therefore the resources required to launch it. Recycling some of those resources could reduce the amount that needs to be transported from Earth.

The benefits would become even greater as missions grow longer.

A journey to Mars, for example, could last years when travel time, surface operations and the return journey are taken into account. A future settlement would face an even greater challenge: it would need to produce or recycle resources locally rather than depend entirely on regular deliveries from Earth.

A closed or partially closed life-support system could therefore become a fundamental technology for long-duration exploration.

The idea is still being tested today

The technology available to space agencies has changed enormously since NASA's early research, but the basic problem has not.

The International Space Station already uses systems that recover and recycle water, while astronauts and researchers continue to study how crops can be grown in space and how biological processes could contribute to future life-support systems.

However, a completely self-sustaining ecosystem capable of supporting humans indefinitely remains far beyond current capabilities.

Biological systems are inherently complex and can be difficult to predict, while space habitats must operate with extremely high reliability.

The likely future may therefore involve a hybrid approach in which mechanical, chemical and biological systems work together rather than one technology doing everything.

From carrying supplies to creating resources

NASA's early research into closed environments reflected a shift in how scientists thought about human spaceflight.

The challenge was no longer simply how to send people into orbit, but how to keep them alive when they could no longer depend on Earth for every resource.

That question has become even more important as space agencies look towards long-duration lunar missions and eventual human exploration of Mars.

The spacecraft of the future may therefore need to function less like a vehicle carrying a large stockpile of supplies and more like a small, carefully managed ecosystem.

The fundamental goal remains simple: use less, waste less and regenerate more.

For humans hoping to live far beyond Earth, the ability to recycle air, water, nutrients and other resources could ultimately be just as important as the rockets that take them there.