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19 August 2010
Features - Habitat (Good)
Astronaut Centrifuge Training
A thing of the past...or the future?
by Byron N. Roberts
When you think of manned space flight, what comes to mind? For some, it’s images of astronaut candidates being tested for the “right stuff:” getting poked and prodded in myriad medical exams, climbing in and out of mock space capsules, and undergoing training in jungles and deserts...as well as being strapped into large centrifuges and subjected to crushing g-forces.

However, it turns out that centrifuges—used during the Mercury, Gemini, and Apollo programs—are no longer on the astronaut-training checklist.

According to William Jeffs at the Johnson Space Center in Houston, Mercury and Gemini astronauts underwent g-load training at the Navy’s Aviation Medical Acceleration Laboratory in Johnsville, PA. From 1965 through about 1975, Apollo and other astronauts were trained in a 50-foot radius centrifuge in the Flight Acceleration Facility.

It was a time-honored (and stomach-wrenching) tradition. So why are astronauts no longer being spun like cotton candy?

Previously, the Mercury, Gemini, and Apollo flights subjected astronauts to substantial g-forces: the first two Mercury missions subjected the solo space capsule occupants to forces as extreme as 6.3 g (6.3 times the force normally exerted on a person standing at the Earth’s surface) on launch and 11 g during re-entry, explained Jeffs.

According to Brienna Henwood at the National AeroSpace Training and Research Center (NASTAR), the crushing sensation experienced at these extremes makes it extremely difficult to breathe, among other physiological and psychological effects.

And then came the Space Shuttle.

In the early days of manned missions, the Mercury, Gemini, and Apollo programs had launched astronauts in capsules mounted on top of rockets. But the Space Shuttle, described as a “heavy launch vehicle” by Henwood, subjects astronauts to significantly less intense g-forces.

Jeffs said, “Shuttle crew members are exposed to about 3 g” during launch, and about 2 g during re-entry. These lower g-loads obviated the need for extensive centrifuge training.

In 1979 the centrifuge was replaced with a large pool in NASA's Weightless Environment Training Facility. However, this storied form of astronaut training is still alive and well in other circles, including NASTAR. The NASTAR facility provides suborbital and orbital flight training for crews, researchers, and passengers, whose ranks will grow as the commercial space flight and space tourism industries expand. Commercial space flight vehicles are anticipated to subject passengers to g-forces in the range of 3 g to 7 g, depending on the company and flight profile. In addition, this range could be exceeded in the event of an “off-nominal” flight, according to Henwood.

In addition to military training, NASTAR offers three different space flight training programs. According to Henwood, “These are aimed at the commercial spaceflight industry whose mission is to take tourists, researchers, and academia into space for either point-to-point transportation (New York to Tokyo in two hours) or to the ISS or space habitats” such as Bigelow’s potential space hotel. NASTAR’s standard space training program lasts two days, and trainees are exposed to peak g-forces of 3.5 g along the “head to toe” axis and 6 g along the “chest to back” axis.

With multiple companies preparing to take customers into space, the construction of spaceports, and the likelihood that the barrier to space will become lower as costs decline, proper training for what to expect during space flight, and how to cope, will only become more important. Such training will be even more crucial because commercial space passengers, unlike government program astronauts who are highly screened and chosen from a large pool, will likely have medical conditions that may pose a risk. Given these facts, it seems unlikely that centrifuge training will go the way of the 50-foot radius machine at NASA.

In fact, centrifuge training may even be re-implemented by NASA. When asked about the possible need for such training with the end of the Space Shuttle program and a return to rocket-capsule systems, Jeffs replied, “If piloting during [the] high-g period of launch is determined to be a requirement, then commercial or military centrifuges might be contracted to provide training.”
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19 August 2010
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