By Don Vaughan

An eclectic array of animals was sent into space during the early years of the American and Soviet aerospace programs. Beginning in the late 1940s, the United States flew various monkeys and mice to high altitudes aboard V-2 rockets to test the effects of weightlessness and other extremes. The earliest space-faring animals did not survive the return to Earth, though later candidates did, with much fanfare.

The Soviet Union closely monitored these preliminary efforts, and conducted their own early space experiments using mice, rats, and rabbits.¹ Later, dogs were also sent into space by Soviet scientists, who preferred those to monkeys because they thought dogs would fidget less during a flight.

In the United States, civilian veterinarians attended to the basic care of the animals prior to launch. The experiments themselves were conducted by astrophysicists and other scientists whose primary intent was determining the safest way to send humans into space. The animals were essentially living cargo whose telemetry was essential to understanding the physical rigors of space flight.

Life before NASA

A credentialed veterinarian would not complete astronaut training and formally become a member of the NASA Astronaut Corps until Richard M. Linnehan, DVM, MPA, joined the agency in 1992. Dr. Linnehan would go on to participate in four shuttle missions and six space walks, and continues to work for NASA today.

Linnehan attended the University of New Hampshire in Durham, graduating in 1980 with a bachelor of science degree in animal sciences and a minor in microbiology. He received his DVM degree from the Ohio State University College of Veterinary Medicine in 1985 and received an MPA from the Kennedy School of Government at Harvard University in 2009.

Linnehan developed an interest in veterinary medicine after shadowing a veterinarian in his hometown while in high school.

"He did a lot of large animal procedures, equine, small ruminants, things of that nature, and I really enjoyed it. It was something I thought I could do as a profession," Linnehan told Veterinary Practice News.

After receiving his DVM, Linnehan entered private veterinary practice and was later accepted to a two-year joint internship in Zoo Animal Medicine and Comparative Pathology at the Baltimore Zoo and Johns Hopkins University. Upon completion, he was commissioned as a captain in the U.S. Army Veterinary Corps and reported for duty in early 1989 at the Naval Ocean Systems Center in San Diego, as chief clinical veterinarian for the U.S. Navy's Marine Mammal Program. During his assignment there, Linnehan initiated and supervised research in the areas of cetacean and pinniped anesthesia, orthopedics, drug pharmacokinetics, and reproduction.

Launching in space

Eager to explore new horizons, Linnehan was selected by NASA in March 1992 and completed a year of astronaut candidate training, which qualified him for space shuttle flight assignments as a mission specialist. "I watched all of the shuttle launches and saw that the mission specialists they were hiring were doctors, physiologists, physicists, geologists, all of the different sides of the life sciences," Linnehan explains. "I decided they needed a veterinarian—they just didn't know it yet."

At the time, Linnehan says, NASA was pondering the construction of Space Station Freedom, which would have been larger and more complex than the International Space Station. "I think the doctors and physiologists convinced NASA management that they needed a veterinarian because the plan was to fly a large centrifuge with probably primates and rodents on board and they needed someone with animal expertise," Linnehan says. "Things changed dramatically for NASA with initial space station plans after I was accepted, but that was probably one of the reasons, in addition to doing well in the interview and tests, I was accepted by NASA for astronaut training."

Linnehan is quick to note that while he is the first veterinarian to complete astronaut candidate training and join the NASA Astronaut Corps, he was not the first veterinarian in space. That honor goes to Martin Fettman, BS, DVM, MS, PhD, DACVP, who flew aboard STS-58 in October 1993 as a payload specialist for Spacelab Life Sciences-2.

Getting to work

The year-long training Linnehan received was rigorous and intense. "It was like drinking from a firehose," he says. "They just throw a ton of stuff at you—everything about how the shuttle works, the computers, the electronics, the life support systems, how to do spacewalks. For the first year you're an astronaut candidate so they can release you if you don't cut the mustard. Luckily, I made it through. It was like the first or second year of veterinary school in terms of 70- and 80-hour weeks, studying every night. It was very intense and very busy."

Linnehan first flew as a mission specialist in 1996 on STS-78, the Life Sciences and Microgravity Spacelab mission (LMS), one of two life sciences missions in which he was involved. His other two missions took him to the Hubble Space Telescope and the International Space Station.

"The first mission was half life sciences and half microgravity physical sciences," Linnehan says. "We flew a few rodent cages, but they were mostly along for the ride, we just monitored them. Most of the LMS life sciences experiments were performed on us the payload crew, the four large primates on board. We performed muscle biopsies, strength tests, eye/inner ear central nervous system decoupling, things of that nature, along with other physical science experiments that studied combustion in space and fluid dynamics. There were a lot of things going on. The second flight, STS 90, was Neurolab, an NIH-sponsored flight that was by far the most rigorous life sciences flight NASA has ever flown."

Animals in space

Adapting to life in microgravity can take some time, though the animals onboard seemed to get used to it fairly quickly, Linnehan says. "The rats and mice reacted and adapted to space, in my opinion, much faster than we did," he adds. "They just accepted the environment they were in and learned how to glide around their cages, get food, and hold on to the tiny spheres of water and drink those. It was pretty impressive in terms of how fast they adapted."

Fish were also interesting to observe. "Water acts differently in space," Linnehan explains. "It will form a sphere due to microgravity unless it is confined in a tank. The fish would swim into a bubble and adhere to the inside of the bubble via surface tension and pop themselves off and into the water again like it was no big deal. Like the other animals, they had issues with balance for a few days because their swim bladders weren't functioning in the normal one gravity environment of earth. But they adapted."

During STS-90/Neurolab in 1998, Linnehan presented a lecture to the North Carolina State University College of Veterinary Medicine in Raleigh, where he is an adjunct professor. During the downlink he discussed the central nervous system and how microgravity affects the inner ear, central nervous system, visual acuity, and more. "I think it was interesting for all involved," Linnehan says. "We had a few questions back and forth. I was in space, and they were on the ground, so it was tough to perceive the audience."

Staying grounded

Though he no longer travels into space, Linnehan is still very active within NASA. Currently, he is jointly assigned to the Astronaut Office Exploration and Integration branches and the NASA Institutional Review Board (IRB) and JSC and Flight Institutional Animal Care and Use Committees (IACUC).

Looking back, Linnehan has found much to be thankful for. "I've met a lot of good people," he says of his time with NASA. "I've gotten to travel and trained with multinational astronauts and support personnel. I participated in four shuttle missions and completed six spacewalks, as well as rendezvousing with the Hubble Space Telescope and the International Space Station. I've had a pretty good career. Another space flight would have been fun, but you need to make room for the next generation."

Don Vaughan is an award-winning writer who frequently writes about veterinary-related topics.

References

1. NASA report titled "A Brief History of Animals in Space." https://history.nasa.gov/animals.html
2. Richard M. Linnehan, DVM, MPA. Telephone interview arranged by NASA PAO Daniel G. Huot. Email: Daniel.g.huot@nasa.gov. Tel: 281-786-9287.
3. https://www.nasa.gov/sites/default/files/atoms/files/linnehan_richard.pdf (NASA bio)
4. https://en.wikipedia.org/wiki/Richard_M._Linnehan
5. https://en.wikipedia.org/wiki/Martin_J._Fettman
6. https://news.ncsu.edu/2019/07/richard-linnehan-veterinary-astronaut