Space-trekking muscle tests drugs for microgravity-induced muscle impairment

A gentle rumble ran under Ngan Huang's feet as a rocket carrying her research -- live, human muscle cells grown on scaffolds fixed on tiny chips -- lifted off, climbed, and disappeared into the sky to the International Space Station National Laboratory. These chips would help Huang better understand muscle impairment, often seen in astronauts and older adults, and test drugs to counter the condition.

Now, the results are back. Reporting in a study published July 25 in Stem Cell Reports, Huang's team showed that space-travelling muscle had metabolic changes that indicate impaired muscle regeneration and gene activities associated to age-related muscle loss called sarcopenia. But drug treatment partially prevented microgravity's adverse effects.

"Space is a really unique environment that accelerates qualities associated with aging and also impairs many healthy processes," says Huang, an associate professor at Stanford University. "Astronauts come back with muscle atrophy, or a reduction of muscle function, because the muscle isn't being actively used in the absence of gravity. As space travel becomes more common and available to civilians, it's important to understand what happens to our muscle in microgravity."

To understand the effects of microgravity on muscles, the researchers launched muscle chips -- bioengineered packages of oriented muscle cells on patterned biomaterials that mimic the structure of real muscles -- into space to grow for seven days under astronauts' care.

When the researchers compared muscle cells grown in microgravity to those grown on Earth, they found impaired muscle fiber formation. They also discovered differences in their gene activity and protein profile. Genes related to mitochondrial function, which muscles get their energy from, were compromised, and genes associated with fat formation were boosted. These findings suggest microgravity can lead to dysfunctions in muscle regeneration.

Space-traveled muscles also have gene activities that somewhat resemble muscles with sarcopenia, which most commonly affects people ages 60 and older.

"We think our research on muscle chips in microgravity may have broader implications on sarcopenia," says Huang. "Sarcopenia usually takes decades to develop on Earth, and we think that microgravity may have some ability to accelerate the disease process in orders of days."

In a proof-of-concept experiment to test the muscle chip for drug screening, the astronauts spiked the chips with drugs to treat sarcopenia or enhance muscle regeneration. The treatment partially mitigated some of the negative effects of microgravity on the muscles, preventing a metabolic shift to fat formation. Looking into gene activity patterns, the drug-treated muscle in microgravity is more similar to samples from Earth than untreated samples in microgravity.

Because space research is labor and resource intensive, the current study is a one-time experiment, and a limited number of samples were allowed to board the rocket. The scientists are now deploying equipment that simulates microgravity to overcome some of those limitations and aid their research in space. Huang's muscle chips are scheduled to embark on another space journey in 2025 to continue the research on identifying drugs for treating microgravity-induced impairment in muscle regeneration.

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How to prevent biofilms in space

After exposure in space aboard the International Space Station, a new kind of surface treatment significantly reduced the growth of biofilms, scientists report. Biofilms are mats of microbial or fungal growth that can clog hoses or filters in water processing systems, or potentially cause illness in people.

In the experiment, researchers investigated a variety of surfaces treated in different ways and exposed to a bacteria called Pseudomonas aeruginosa, which is an opportunistic pathogen than can cause infections in humans, especially in hospitals. The surfaces were incubated for three days aboard the space station, starting in 2019. The results show that textured surfaces impregnated with a lubricant were highly successful at preventing biofilm growth during their long exposure in space. The findings are described in a paper in the journal Nature Microgravity, by Samantha McBride PhD '20 and Kripa Varanasi of MIT, Pamela Flores and Luis Zea at the University of Colorado, and Jonathan Galakza at NASA Ames Research Center.

Clogs in water recovery system hoses aboard the ISS have been so severe at times, the hoses had to be sent back to Earth for cleaning and refurbishing. And while it isn't known whether biofilms have directly contributed to astronaut illnesses, on Earth, biofilms are associated with 65 percent of microbial infections, and 80 percent of chronic infections, the researchers say.

One approach to preventing biofilms is to use surfaces coated with certain metals or oxides that kill microbes, but this approach can fail when a layer of dead microbes builds up on the surface and allows biofilm to form above it. But this was not the case with the liquid-infused surface that performed well in the ISS experiments: Rather than killing the microbes, it prevented them from adhering to the surface in the first place.

The specific surface used was made of silicon that was etched to produce a nanoscale forest of pillars. This spiky surface is then infused with a silicon oil, which is drawn into the texture and held in place by capillary action, leaving a smooth and highly slippery surface that significantly reduces the adhesion of microbes and prevents them from forming a biofilm.

Identical experiments were conducted on Earth as well as on the space station to determine the differences produced by the microgravity environment in orbit. To the researchers' surprise, the liquid-infused surface performed even better in space than it did on Earth at preventing microbial adhesion.

On previous and current space stations, including the USSR's Mir station, Salyut 6, and Salyut 7, as well as the International Space Station, "they've seen these biofilms, and they jeopardize a variety of instruments or equipment, including space suits, recycling units, radiators, and water treatment facilities, so it's a very important problem that needed to be understood," says Varanasi, a professor of mechanical engineering and founder of a company called LiquiGlide, which makes liquid-impregnated surfaces for containers to help their contents slide out.

Previous tests on Earth had shown that these treated surfaces could significantly reduce biofilm adhesion. When the samples from the space station were retrieved and tested, "we found that these surfaces are extremely good at preventing biofilm formation in the space station as well," Varanasi says. This is important because past work has found that microgravity can have a significant influence on biofilm morphologies, attachment behavior, and gene expression, according to McBride. Thus, strategies that work well on Earth for biofilm mitigation may not necessarily be applicable to microgravity situations.

Preventing biofilms will be especially important for future long-duration missions, such as to the moon or Mars, where the option of quickly returning fouled equipment or sick astronauts to Earth will not be available, the team says. If further testing confirms its long-term stability and successful biofilm prevention, coatings based on the liquid-treated surface concept could be applied to a variety of critical components that are known to be susceptible to biofilm fouling, such as water treatment hoses and filters, or to parts that come in close contact with astronauts, such as gloves or food preparation surfaces.

In the terrestrial samples, biofilm formation was reduced by about 74 percent, while the space station samples showed a reduction of about 86 percent, says Flores, who did much of the testing of the ISS-exposed samples. "The results we got were surprising," she says, because earlier tests carried out by others had shown biofilm formation was actually greater in space than on Earth. "We actually found the opposite on these samples," she says.

While the tests used a specific and well-studied gram-negative kind of bacteria, she says, the results should apply to any kind of gram-negative bacteria, and likely to gram-positive bacteria as well. They found that the areas of the surface where no bacterial growth took place were covered by a thin layer of nucleic acids, which have a slight negative electric charge that may have helped to prevent microbes from adhering. Both gram-positive and gram-negative bacteria have a slight negative charge, which could repel them from that negatively charged surface, Flores says.

Other types of anti-fouling surfaces, Varanasi says, "work mostly on a biocidal property, which usually only works for a first layer of cells because after those cells die they can form a deposit, and microbes can grow on top of them. So, usually it's been a very hard problem." But with the liquid-impregnated surface, where what is exposed is mostly just the liquid itself, there are very few defects or points where the bacteria can find a footing, he says.

Although the test material was on the space station for more than a year, the actual tests were only performed over a three-day period because they required active participation by the astronauts whose schedules are always very busy. But one recommendation the team has made, based on these initial results, is that longer-duration tests should be carried out on a future mission. In these first tests, Flores says, the results after the third day looked the same as after the first and second days. "We don't know for how long it will be able to keep up this performance, so we definitely recommend a longer time of incubation, and also, if possible, a continuous analysis, and not just end points."

Zea, who initiated the project with NASA, says that this was the first time the agency has conducted tests that involved joint participation by two of its science programs, biology and physical sciences. "I think it stresses the importance of multidisciplinarity because we need to be able to combine these different disciplines to find solutions to real world problems."

Biofilms are also a significant medical issue on Earth, especially on medical devices or implants including catheters, where they can lead to significant disease problems. The same kind of liquid-impregnated surfaces may have a role to play in helping to address these issues, Varanasi says.

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Wobbling droplets in space confirm late professor's theory

At a time when astronomers around the world are reveling in new views of the distant cosmos, an experiment on the International Space Station has given Cornell researchers fresh insight into something a little closer to home: water.

Specifically, the space station's microgravity environment illuminated the ways that water droplets oscillate and spread across solid surfaces -- knowledge that could have very earthbound applications in 3D-printing, spray cooling, and manufacturing and coating operations.

The team's paper, "Oscillations of Drops with Mobile Contact Lines on the International Space Station: Elucidation of Terrestrial Inertial Droplet Spreading," published Aug. 16 in Physical Review Letters. The lead author is Joshua McCraney, M.S. '19, Ph.D. '21.

The experiment and its findings, while successful, are also bittersweet. The paper's co-senior author Paul Steen, the Maxwell M. Upson Professor in the Smith School of Chemical and Biomolecular Engineering in the College of Engineering, died in September 2020, just before the experiment was conducted.

"It's sad that Paul didn't get to see the experiments launch into space," said co-senior author Susan Daniel, the Fred H. Rhodes Professor in the Smith School of Chemical and Biomolecular Engineering, and Steen's longtime collaborator. "We hope that we did right by him in the end, and that the paper that we produced from the work would make him proud."

Daniel began collaborating with Steen shortly after she first came to Cornell as an assistant professor in 2007. While her current research is focused on the biological interface of the coronavirus, her graduate work was in chemical interfaces and fluid mechanics -- a field in which Steen was advancing a number of theoretical predictions based upon how droplets resonate when subjected to vibrations. The two researchers instantly connected.

"He knew the theory and made predictions, and I knew how to execute the experiments to test them," Daniel said. "Basically, from the moment I got here in 2007 until he passed away, we worked on trying to understand how liquids and surfaces interact with each other, and how the contact line at the interface between them behaves under different conditions."

Their collaboration resulted in a "photo album" of the dozens of possible shapes that an oscillated drop of water can take. Steen later expanded on that project by cataloging the droplets' energy states as evidenced by those resonant shapes, organizing them into a "periodic table" classification.

In 2016, Steen and Daniel received a four-year grant from the National Science Foundation (NSF) and NASA's Center for the Advancement of Science in Space to conduct fluid dynamics research aboard the International Space Station U.S. National Laboratory.

Space is an ideal place to study the behavior of fluids because of the radical reduction of gravity, which on the ISS is about one-millionth of its terrestrial level. This means that fluid-surface interactions which are so small-scale and speedy on Earth that they are practically invisible can be, in space, nearly 10 times larger -- from microns to centimeters -- and their duration slows nearly 30-fold.

"It's harder to study these drop motions, experimentally and fundamentally, when you have gravity in your way," Daniel said.

Steen and Daniel selected a few resonance shapes from their photo album that they wanted to explore in detail, with a focus on how a water droplet's contact line -- or outer edge -- slides back and forth across a surface, driving the way the liquid will spread, a phenomenon that can be controlled by varying vibration frequencies.

The team prepared meticulous instructions for the astronauts to follow, compressing four years of planning into a several-minute experiment in which every second was tightly choreographed.

With the researchers monitoring and providing feedback in real time on the ground, the astronauts deposited 10 mL water droplets via a syringe onto nine different hydrophobic surfaces with varying degrees of roughness. They also forced pairs of droplets to coalesce together, and placed droplets onto an oscillator and tuned its vibrations to achieve the targeted resonance shapes. The water droplets' wobbling and jiggling movements were filmed, and the researchers spent the next year analyzing the data.

That analysis ultimately confirmed Steen's theories about the way a liquid's density and surface tension control the contact line's mobility, overcoming a surface's roughness.

Daniel credits co-author Joshua Bostwick, Ph.D. '11, a former student of Steen's and now the Stanzione Collaboration associate professor at Clemson University, with ensuring that the experiment results squared with Steen's theoretical predictions.

"Josh was able to carry on with the theoretical side of this work in Paul's absence, which was not something I was ready to step into and do. It was nice to have him rejoin the team and help us make sure that we were able to extract everything we could from the data we collected," Daniel said. "Now we can essentially use the theory that Paul created to make predictions, for example, in processes where you're spraying droplets on surfaces, or in 3D-printing, or where liquids spread across a surface really quickly."

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Brain damage from long stays in space

Spending a long time in space appears to cause brain damage. This is shown by a study of five Russian cosmonauts who had stayed on the International Space Station (ISS). Researchers at the University of Gothenburg are among those now presenting the results.

The study is published in the scientific journal JAMA Neurology. Its co-authors at the University, scientists from the Institute of Neuroscience and Physiology at Sahlgrenska Academy, wrote it jointly with colleagues in Moscow and Munich.

The scientists followed five male Russian cosmonauts working on the permanently manned International Space Station (ISS), which is in orbit 400 km from Earth's surface.

The adverse effects on the body of long periods in space have been known for some time. The negative changes include atrophic muscles, decreasing bone mass, deteriorating vision and altered bacterial flora in the gut.

Evidence of brain damage

Blood samples were taken from the cosmonauts 20 days before their departure to the ISS. On average, they then stayed in space for 169 days (approximately five and a half months). The participants' mean age was 49.

After their return to Earth, follow-up blood samples were taken on three occasions: one day, one week, and about three weeks respectively after landing. Five biomarkers for brain damage were analyzed. They were neurofilament light (NFL), glial fibrillary acidic protein (GFAP), total tau (T-tau), and two amyloid beta proteins.

For three of the biomarkers -- NFL, GFAP and the amyloid beta protein Aβ40 -- the concentrations were significantly elevated after the space sojourn. The peak readings did not occur simultaneously after the men's return to Earth, but their biomarker trends nonetheless broadly tallied over time.

"This is the first time that concrete proof of brain-cell damage has been documented in blood tests following space flights. This must be explored further and prevented if space travel is to become more common in the future," says Henrik Zetterberg, professor of neuroscience and one of the study's two senior coauthors.

Several studies underway

"To get there, we must help one another to find out why the damage arises. Is it being weightless, changes in brain fluid, or stressors associated with launch and landing, or is it caused by something else? Here, loads of exciting experimental studies on humans can be done on Earth," he continues.

The notion that the changes concerned may have a bearing on brain function is substantiated by changes also seen in magnetic resonance imaging (MRI) of the brain after space travel. Further support is provided by clinical tests of the men's brain function that show deviations linked to their assignments in space. However, the present study was too small to investigate these associations in detail.

Zetterberg and his coauthors at the University, scientist Nicholas Ashton and Professor Kaj Blennow, are currently discussing follow-up studies with their other fellow researchers involved in the study, and also with national and international space research institutes.

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NASA's SpaceX Crew-1 astronauts headed to International Space Station

 

A SpaceX Falcon 9 rocket carrying the company's Crew Dragon spacecraft is launched on NASA's SpaceX Crew-1 mission to the International Space Station with NASA astronauts Mike Hopkins, Victor Glover, Shannon Walker, and Japan Aerospace Exploration Agency astronaut Soichi Noguchi onboard, Sunday, Nov. 15, 2020, at NASA's Kennedy Space Center in Florida. NASA's SpaceX Crew-1 mission is the first crew rotation mission of the SpaceX Crew Dragon spacecraft and Falcon 9 rocket to the International Space Station as part of the agency's Commercial Crew Program. Hopkins, Glover, Walker, and Noguchi launched at 7:27 p.m. EST from Launch Complex 39A at the Kennedy Space Center to begin a six month mission onboard the orbital outpost.

An international crew of astronauts is en route to the International Space Station following a successful launch on the first NASA-certified commercial human spacecraft system in history. NASA's SpaceX Crew-1 mission lifted off at 7:27 p.m. EST Sunday from Launch Complex 39A at the agency's Kennedy Space Center in Florida.

The SpaceX Falcon 9 rocket propelled the Crew Dragon spacecraft with NASA astronauts Michael Hopkins, Victor Glover, and Shannon Walker, along with Soichi Noguchi of the Japan Aerospace Exploration Agency (JAXA), into orbit to begin a six-month science mission aboard the space station.

"NASA is delivering on its commitment to the American people and our international partners to provide safe, reliable, and cost-effective missions to the International Space Station using American private industry," said NASA Administrator Jim Bridenstine. "This is an important mission for NASA, SpaceX and our partners at JAXA, and we look forward to watching this crew arrive at station to carry on our partnership for all of humanity."

The Crew Dragon spacecraft, named Resilience, will dock autonomously to the forward port of the station's Harmony module about 11 p.m. Monday, Nov. 16. NASA Television and the agency's website are providing ongoing live coverage through docking, hatch opening, and the ceremony to welcome the crew aboard the orbiting laboratory.

"I could not be more proud of the work we've done here today," said Gwynne Shotwell, president and chief operating officer of SpaceX. "Falcon 9 looked great, Dragon was dropped off into a beautiful orbit about 12 minutes into the mission, and we'll get more data as we go."

The Crew-1 mission is the first of six crewed missions NASA and SpaceX will fly as part of the agency's Commercial Crew Program. This mission has several firsts, including:
 

• The first flight of the NASA-certified commercial system designed for crew transportation, which moves the system from development into regular flights;
• The first international crew of four to launch on an American commercial spacecraft;
• The first time the space station's long duration expedition crew size will increase from six to seven crew members, which will add to the crew time available for research; and
• The first time the Federal Aviation Administration has licensed a human orbital spaceflight launch.

The astronauts named the Crew Dragon spacecraft Resilience, highlighting the dedication teams involved with the mission have displayed and to demonstrate that when we work together, there is no limit to what we can achieve. They named it in honor of their families, colleagues, and fellow citizens.

"Watching this mission launch is a special moment for NASA and our SpaceX team," said Steve Stich, manager of NASA's Commercial Crew Program. "We are looking forward to getting this crew to station to continue our important work, and I want to thank the teams for the amazing effort to make the next generation of human space transportation possible."

During flight, SpaceX commands the spacecraft from its mission control center in Hawthorne, California, and NASA teams monitor space station operations throughout the flight from the Mission Control Center at the agency's Johnson Space Center in Houston.

Hopkins, Glover, Walker, and Noguchi will join the Expedition 64 crew of Commander Sergey Ryzhikov and Flight Engineer Sergey Kud-Sverchkov, both of the Russian space agency Roscosmos, and Flight Engineer Kate Rubins of NASA.

"It is an honor to have our Japanese astronaut launch on this Crew-1 Dragon as the first astronaut of the International Partner participating in the ISS program," said Hiroshi Sasaki, JAXA vice president. "We look forward to having him conduct lots of science and demonstrate the technology, for here on Earth and for the future. I would also like to thank NASA and SpaceX for their tremendous effort to make this happen."

Rubins, Hopkins, Glover, Walker, and Noguchi will participate in a live crew news conference from orbit at 9:55 a.m. Thursday, Nov. 19, on NASA TV and the agency's website.

Crew-1 Astronauts

Michael Hopkins is commander of the Crew Dragon spacecraft and the Crew-1 mission. Hopkins is responsible for all phases of flight, from launch to re-entry. He also will serve as an Expedition 64 flight engineer aboard the station. Selected as a NASA astronaut in 2009, Hopkins spent 166 days in space as a long-duration crew member of Expeditions 37 and 38 and completed two spacewalks totaling 12 hours and 58 minutes. Born in Lebanon, Missouri, Hopkins grew up on a farm outside Richland, Missouri. He has a bachelor's degree in aerospace engineering from the University of Illinois, and a master's degree in aerospace engineering from Stanford University. Before joining NASA, Hopkins was a flight test engineer with the U.S. Air Force.

Victor Glover is the pilot of the Crew Dragon spacecraft and second-in-command for the mission. Glover is responsible for spacecraft systems and performance. He also will be a long-duration space station crew member. Selected as an astronaut in 2013, this is his first spaceflight.

The California native holds a Bachelor of Science degree in general engineering from California Polytechnic State University, a Master of Science degree in flight test engineering and a master's degree military operational art and science from Air University, and a Master of Science degree in systems engineering from Naval Postgraduate School. Glover is a naval aviator and was a test pilot in the F/A‐18 Hornet, Super Hornet, and EA‐18G Growler aircraft.

Shannon Walker is a mission specialist for Crew-1. As a mission specialist, she works closely with the commander and pilot to monitor the vehicle during the dynamic launch and re-entry phases of flight. She also is responsible for monitoring timelines, telemetry, and consumables. Once aboard the station, Walker will become a flight engineer for Expedition 64. Selected as a NASA astronaut in 2004, Walker launched to the International Space Station aboard the Russian Soyuz TMA-19 spacecraft as the co-pilot, and spent 161 days aboard the orbiting laboratory. More than 130 microgravity experiments were conducted during her stay in areas such as human research, biology, and materials science. A Houston native, Walker received a Bachelor of Arts degree in physics from Rice University, as well as a Master of Science degree and a doctorate in space physics, both from Rice University, in 1992 and 1993, respectively.

Soichi Noguchi also is a mission specialist for Crew-1, working with the commander and pilot to monitor the vehicle during the dynamic launch and re-entry phases of flight, and keeping watch on timelines, telemetry and consumables. Noguchi also will become a long-duration crew member aboard the space station. He was selected as an astronaut candidate by the National Space Development Agency of Japan (NASDA, currently the Japan Aerospace Exploration Agency) in May 1996. Noguchi is a veteran of two spaceflights. During STS-114 in 2005, Noguchi became the first Japanese astronaut to perform a spacewalk outside the space station. He performed a total of three spacewalks during the mission, accumulating 20 hours and 5 minutes of spacewalking time. He launched aboard a Soyuz spacecraft in 2009, to return to the station as a long-duration crew member. The Crew Dragon will be the third spacecraft Noguchi has flown to the orbiting laboratory.

Mission Objectives

The crew will conduct science and maintenance during a six-month stay aboard the orbiting laboratory and will return in spring 2021. It is scheduled to be the longest human space mission launched from the United States. The Crew Dragon spacecraft is capable of staying in orbit for at least 210 days, as a NASA requirement.

Crew Dragon also is delivering more than 500 pounds of cargo, new science hardware and experiments inside, including Food Physiology, a study of the effects of an optimized diet on crew health and, Genes in Space-7, a student-designed experiment that aims to better understand how spaceflight affects brain function, enabling scientists to keep astronauts healthy as they prepare for long-duration missions in low-Earth orbit and beyond.

Among the science and research investigations the crew will support during its six-month mission are a study using chips with tissue that mimics the structure and function of human organs to understand the role of microgravity on human health and diseases and translate those findings to improve human health on Earth, growing radishes in different types of light and soils as part of ongoing efforts to produce food in space, and testing a new system to remove heat from NASA's next generation spacesuit, the Exploration Extravehicular Mobility Unit (xEMU).

During their stay on the orbiting laboratory, Crew-1 astronauts expect to see a range of uncrewed spacecraft including the next generation of SpaceX cargo Dragon spacecraft, the Northrop Grumman Cygnus, and the Boeing CST-100 Starliner on its uncrewed flight test to the station. They also will conduct a variety of spacewalks and welcome crews of the Russian Soyuz vehicle and the next SpaceX Crew Dragon in 2021.

At the conclusion of the mission, the Crew-1 astronauts will board Crew Dragon, which will then autonomously undock, depart the space station, and re-enter Earth's atmosphere. Crew Dragon also will return to Earth important and time-sensitive research. NASA and SpaceX are capable of supporting seven splashdown sites located off Florida's east coast and in the Gulf of Mexico. Upon splashdown, the SpaceX recovery ship will pick up the crew and return to shore.

NASA's Commercial Crew Program is delivering on its goal of safe, reliable, and cost-effective transportation to and from the International Space Station from the United States through a partnership with American private industry. This partnership is changing the arc of human spaceflight history by opening access to low-Earth orbit and the International Space Station to more people, more science, and more commercial opportunities.

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NASA astronauts safely splash down after first commercial crew flight to space station

A SpaceX fast boat races toward the SpaceX Crew Dragon spacecraft moments before it splashed down in the Gulf of Mexico with NASA astronauts Bob Behnken and Doug Hurley aboard.

Two NASA astronauts splashed down safely in the Gulf of Mexico Sunday for the first time in a commercially built and operated American crew spacecraft, returning from the International Space Station to complete a test flight that marks a new era in human spaceflight.

SpaceX's Crew Dragon, carrying Robert Behnken and Douglas Hurley, splashed down under parachutes in the Gulf of Mexico off the coast of Pensacola, Florida at 2:48 p.m. EDT Sunday and was successfully recovered by SpaceX. After returning to shore, the astronauts immediately will fly back to Houston.

"Welcome home, Bob and Doug! Congratulations to the NASA and SpaceX teams for the incredible work to make this test flight possible," said NASA Administrator Jim Bridenstine. "It's a testament to what we can accomplish when we work together to do something once thought impossible. Partners are key to how we go farther than ever before and take the next steps on daring missions to the Moon and Mars."

Behnken and Hurley's return was the first splashdown for American astronauts since Thomas Stafford, Vance Brand, and Donald "Deke" Slayton landed in the Pacific Ocean off the coast of Hawaii on July 24, 1975, at the end of the Apollo-Soyuz Test Project.

NASA's SpaceX Demo-2 test flight launched May 30 from the Kennedy Space Center in Florida. After reaching orbit, Behnken and Hurley named their Crew Dragon spacecraft "Endeavour" as a tribute to the first space shuttle each astronaut had flown aboard.

Nearly 19 hours later, Crew Dragon docked to the forward port of the International Space Station's Harmony module May 31.

"On behalf of all SpaceX employees, thank you to NASA for the opportunity to return human spaceflight to the United States by flying NASA astronauts Bob Behnken and Doug Hurley," said SpaceX President and Chief Operating Officer Gwynne Shotwell. "Congratulations to the entire SpaceX and NASA team on such an extraordinary mission. We could not be more proud to see Bob and Doug safely back home -- we all appreciate their dedication to this mission and helping us start the journey towards carrying people regularly to low Earth orbit and on to the Moon and Mars. And I really hope they enjoyed the ride!"

Behnken and Hurley participated in a number of scientific experiments, spacewalks and public engagement events during their 62 days aboard station. Overall, the astronaut duo spent 64 days in orbit, completed 1,024 orbits around Earth and traveled 27,147,284 statute miles.

The astronauts contributed more than 100 hours of time to supporting the orbiting laboratory's investigations. Hurley conducted the Droplet Formation Study inside of the Microgravity Science Glovebox (MSG), which evaluates water droplet formation and water flow. Hurley also conducted the Capillary Structures investigation, which studies the use of different structures and containers to manage fluids and gases.

Hurley and Behnken worked on numerous sample switch outs for the Electrolysis Measurement (EM) experiment, which looks at bubbles created using electrolysis and has implications for numerous electrochemical reactions and devices. Both crew members also contributed images to the Crew Earth Observations (CEO) study. CEO images help record how our planet is changing over time, from human-caused changes -- such as urban growth and reservoir construction -- to natural dynamic events, including hurricanes, floods, and volcanic eruptions.

Behnken conducted four spacewalks while on board the space station with Expedition 63 Commander and NASA colleague Chris Cassidy. The duo upgraded two power channels on the far starboard side of the station's truss with new lithium-ion batteries. They also routed power and Ethernet cables, removed H-fixtures that were used for ground processing of the solar arrays prior to their launch, installed a protective storage unit for robotic operations, and removed shields and coverings in preparation for the arrival later this year of the Nanoracks commercial airlock on a SpaceX cargo delivery mission.

Behnken now is tied for most spacewalks by an American astronaut with Michael Lopez-Alegria, Peggy Whitson, and Chris Cassidy, each of whom has completed 10 spacewalks. Behnken now has spent a total of 61 hours and 10 minutes spacewalking, which makes him the U.S. astronaut with the third most total time spacewalking, behind Lopez-Alegria and Andrew Feustel, and the fourth most overall.

The Demo-2 test flight is part of NASA's Commercial Crew Program, which has worked with the U.S. aerospace industry to launch astronauts on American rockets and spacecraft from American soil to the space station for the first time since 2011. This is SpaceX's final test flight and is providing data on the performance of the Falcon 9 rocket, Crew Dragon spacecraft and ground systems, as well as in-orbit, docking, splashdown, and recovery operations.

Crew Dragon Endeavour will return back to SpaceX's Dragon Lair in Florida for inspection and processing. Teams will examine the spacecraft's data and performance from throughout the test flight. The completion of Demo-2 and the review of the mission and spacecraft pave the way for NASA to certify SpaceX's crew transportation system for regular flights carrying astronauts to and from the space station. SpaceX is readying the hardware for the first rotational mission, called Crew-1, later this year. This mission would occur after NASA certification, which is expected to take about six weeks.

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