XROOTS Environmental System: Delivering Sustainability in Space

timeline-Sierra Space XROOTS

At Sierra Space, we are building a platform in space to benefit life on Earth. One aspect of that mission is our dedication to creating the next generation of bio-agricultural products through system and service solutions that increase plant productivity in space. Our long history in plant growth systems stem from 20 years of research and development in environmental control and life support systems for NASA. We believe the research conducted in microgravity could not only aide in future space missions but have other potential uses when implemented on Earth. The technology could positively affect commercial greenhouses and increase the understanding of plant physiology and genetics, leading to evolutionary applications for medicine, agriculture, biotechnology and environmental management.

Thomas Marshburn

NASA astronaut and Crew-3 member Tom Marshburn looks at chiles growing inside of the Advanced Plant Habitat. Crew-3 performed the second harvest of chiles aboard the International Space Station for the Plant Habitat-04 experiment. Photo Credit: NASA

Our plant growth system developments date back to the original NASA Space Shuttle missions with the biomass production system testing wheat and Brassica.

Even though scientists and astronauts have been studying space farming for decades, plants were seen as points of research and not considered a point of sustainability for astronauts until technology advanced sufficiently to consider the possibility of deep space exploration, opening the door to increased mission studies.

Today we continue to address the challenges of space farming.

In March of 2014, Veggie, a modularly designed vegetable production plant growth unit, developed and built in partnership with Sierra Space and Kennedy Space Center, was integrated by NASA aboard the International Space Station (ISS). This system provided sufficient lighting for plant growth making it possible for to successfully grow red romaine lettuce. After a safety analysis in 2015, U.S. astronauts were able to eat fresh produce for the first time on-orbit.

A variety of consumable vegetables including Chinese cabbage, mizuna mustard, lettuce, wasabi mustard and bok choy have since been successfully grown in space. Today, as the ISS circles in low-Earth orbit there are two Veggie systems in use.

Astronauts aboard the ISS have grown over nine different types of plants in space using our systems with researchers at Kennedy Space Center who have tested more than 100 crops on the ground. NASA astronauts even made space tacos after harvesting red and green chile peppers as a part of the Plant Habitat-04 study.

“Growing plants in space involves complex lighting and adequate nutrient supply to roots. Due to these conditions, successful plant growth had been limited until the mid-nineties,” said Robert Morrow, Principal Scientist for Sierra Space Environmental Systems. According to Morrow, experiments involving space-based plant production will eventually provide nutrition, oxygen, carbon dioxide removal, and water purification for astronauts to support extended duration space travel and exploration.

ROOTS team reviewing Astro Garden plant growth testing in a laboratory facility at the Sierra Space Madison WI location (left to right: John Wetzel, Dan Wyman, Bob Morrow, Gil Tellez)

XROOTS team reviewing Astro Garden plant growth testing in a laboratory facility at the Sierra Space Madison WI location (left to right: John Wetzel, Dan Wyman, Bob Morrow, Gil Tellez).

As modern day space exploration points towards interplanetary space missions beyond the Moon life support systems must be expanded. “While Veggie is still in use today aboard the ISS, it lacks the scalability required for routine salad crop production in space,” says John Wetzel, Sierra Space’s Environmental Systems Program Manager. The team at Sierra Space determined that hydroponic type growth systems would need to make larger scale crop production in space feasible. “That is why we developed the eXposed Root On-Orbit Test System known as XROOTS,” added Wetzel.

XROOTS® launched aboard an Antares Cygnus CRS-2 rocket, named S.S. Piers Sellers after the U.S. astronaut and climate scientist, from NASA’s Wallops Flight Facility on Wallops Island, Virginia, on Saturday, Feb. 19, 2022. The launch was a part of the NG-17 cargo resupply mission, with supplies aboard the Antares rocket including various hardware, research, and science experiments.

“After the NG-17 supply mission arrived at the ISS, XROOTS was integrated with Veggie. The base plate and bellows were removed from the Veggie Facility and the XROOTS module was mounted below Veggie,” said Morrow. “Following a thorough review of the system, seed cartridges were placed in the XROOTS chambers, a nutrient solution was mixed and placed in the system reservoir, and the XROOTS module was powered up and initiated to begin testing.”

With XROOTS onboard the ISS, the system began testing aeroponic and hydroponic techniques and nutrient delivery systems to continue to develop advanced subsystems that significantly reduce mass, power, and volume of microgravity plant production.

To be effective aboard the ISS, hydroponic type systems must provide sufficient water and nutrients to support crop growth, maintain good root zone aeration, and accommodate a variety of plant types including rooting, fruiting and leafy green crops while thriving in microgravity conditions. “XROOTS is mounted below Veggie, so Veggie provides the lighting while XROOTS provides the place for the plants to grow,” explains Wetzel. “We have seed cartridges and a volume below where the roots grow suspended in water obtaining  their nutrients through a delivery system which combines  a nutrient and water solution that goes into the plants – they’ll use some of the nutrients but the rest will be recycled, returned, and reused.”


The eXposed Root On-Orbit Test System (XROOTS) investigation uses hydroponic and aeroponic techniques to grow plants without soil or other growth media.

Sierra Space has helped monitor and control payload operations from our Payload Operations Center (POC) located in Madison, Wisconsin. The study runs  over six months with tests lasting around 40 days.

“Since it’s completely hydroponic and aeroponic that means there’s no soil media. This is because the soil weighs more than water and is hard to reuse for multiple plant growth cycles. You can save mass by having a lighter more efficient way to grow crops. This also minimizes the hazard of particulate particles in microgravity which could affect crew health.” says Wetzel. “We spray the plants with nutrient solution and the remainder of the fluid gets captured in our root modules.”

Soilless technologies can sustain high production rates on Earth and consistently deliver configuration flexibility that is relatively simple to maintain in commercial settings. This is not the case when trying to adapt these technologies for operating in microgravity. By studying hydroponic and aeroponic techniques in a microgravity environment, Sierra Space aims to provide a scalable alternative to enable plant growth systems of adequate size to contribute to future deep space exploration missions.

“Since this is an experiment to test out the growth part of the system, samples of the roots and leaves will be returned to Kennedy Space Center for evaluation.” Says Wetzel. “We hope to identify suitable methods to produce crops on a larger scale for Astro Garden to enable habitats for extended space operations.”

Studying plants in space will provide the scientific information necessary for development of a life support system.

Bob and Watti with Radish and Mizuna XROOTS on ISS

NASA astronauts Jessica Watkins and Bob Hines review XROOTS growth. Photo Credit: NASA

“By using the XROOTS system scientists can study the entire life cycle, from seed germination through maturity, with multiple independent growth chambers,” says Morrow. “This makes it possible to observe root development and the interaction of fluid with roots at different growth stages.”

For the last few months, data has been collected by the crew aboard the ISS and the sensors located within the XROOTS system. These studies will inform suitable methods of crop production on a larger scale for future space missions and support a variety of plant species that can be cultivated for educational outreach, fresh food and even recreation for crew on long-duration missions.

Results of the XROOTS experiment will be available after the conclusion of the mission in November. Once available, the information will inform upgrades to the Astro Garden® nutrient and water delivery system for the development of fully scalable space gardens and a sustainable future in space will be a step closer.

Subscribe to Updates

"*" indicates required fields