Tiredness not an issue on Endeavour

December 09, 1993|By Ann LoLordo | Ann LoLordo,Staff Writer

When the space mechanics repairing the Hubble Space Telescope go to work, the flight surgeon at Mission Control knows how fast their hearts are beating.

He knows if they sweat, breathe heavily or laugh.

What he doesn't necessarily know is whether they are tired. And the mechanics don't volunteer much about that.

"Fatigue has to be self-reported," said Dr. Richard T. Jennings, a NASA flight surgeon who has monitored three shuttle flights. "We'll let these guys tell us if this is too much or not."

Mission Control does have its finger on the pulse of America's most experienced -- and tested -- spacewalkers. Late last night, astronauts Story Musgrave and Jeffrey A. Hoffman of the shuttle Endeavour began the fifth and possibly final space walk of the 11-day mission -- a record number in the shuttle program's 12 years.

Before each man steps into his space suit, he attaches two electrodes to his chest that measure the electrical activity of the heart, just as an electrocardiogram does in an intensive care unit, said Dr. Jennings.

A normal heart rate is 70 to 80 beats per minute, he said.

"Most of the astronauts are in such excellent condition we tend to see 50 to 60 when they are at rest," said Dr. Jennings.

But science can't replace the ache, the groan, the verbal and literal language of the body. "We listen for the subtle things, even the breathing rate you can hear on console," said Dr. Jennings.

During the walks, the flight surgeon monitors the heart and can compare the data with a heart rate recorded in practice sessions on the ground, in a special vacuum chamber, and on a treadmill. The flight surgeon monitors the levels of carbon dioxide and pressure in the temperature-controlled space suit.

"So we have great insight on the console on what their work rate is, what the heart rate of the crew is and how they are doing," said Dr. Jennings.

The flight surgeon has a daily medical conference with the crew to discuss their performance. (NASA does not give out medical information on the astronauts unless it affects the mission.) Two crew members also undergo special training "to make them our medical eyes and ears on orbit," Dr. Jennings said.

But shouldn't these celestial grease monkeys be tired by now? Their bodies are running on space time, working while America sleeps (their own sleep cycle is from 11 a.m. to 7 p.m. EST). The spacewalks extend for at least six hours, 360 miles above Earth, in 250 pounds of spacesuit. They undertake tedious tasks in gloves as bulbous as mitts. They haul pieces of equipment that resemble refrigerators -- even if it is in a weightless environment.

It's enough to tire the most Herculean space hero.

But the two teams of spacewalkers (Astronauts Musgrave and Hoffman, Kathryn "KT" Thornton and Air Force Lt. Col. Tom Akers) can't wait to rev up their power tools. The first four spacewalks started about an hour earlier than planned. On Tuesday night, the start of the fourth spacewalk, Colonel Akers and Ms. Thornton beat the lead flight director to work. "That tells me this crew is doing wonderfully," said the lead flight director, Milt Heflin.

"Certainly the guys are going to be pumped for this mission and have their adrenalin pumped," said Dr. Jennings. "I don't think you can read fatigue from the heart rate monitor on Earth. . . . If there is a word you can use to describe astronauts, it is they are professional."

In his years as a space physician, Dr. Jennings said, he has never heard an astronaut say he is tired. "These folks have trained for years to do what they're doing," he said.

Professionalism aside, the Endeavour astronauts have undergone extensive training -- 400 hours in a water tank that simulates weightlessness. An astronaut preparing for a spacewalk usually spends about 20 hours in a similar tank before a flight. The workouts prepared them mentally and physically for the job ahead, Dr. Jennings said.

"They're focused on the game. They're not keeping in mind how tired or fatigued they are," astronaut Mario Runco said of the Endeavour crew. "They're in the seventh game of a world series. The tiredness will come after the work is done."

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