Ramil Sitdikov / AFP - Getty Images

NASA astronaut Christopher Cassidy gets his spacesuit checked prior to Thursday's launch to the International Space Station. Straps bind Cassidy's knees close to his chest, in the position he'll have to maintain during most of the six-hour trip.

By James Oberg, NBC News Space Analyst

The speedier ride that three spacefliers are taking into orbit on Thursday will get them aboard the roomy International Space Station a lot sooner than on previous Soyuz space missions. It will lower the demand on expensive support teams back on Earth. But there's also an uncomfortable aspect to the shorter flight plan.

That aspect has to do with the Russian-made emergency pressure suits that crew members wear for launch aboard the Soyuz spacecraft. In the past, spacefliers put on the suits several hours before launch, and wore them for about three hours in flight long enough to perform the early rocket maneuvers. Then they took off the suits and put them away until docking, two days later. During most of the trip, the travelers could stretch out in the orbital module, a roomier area of the Soyuz spacecraft.

The situation is different for NASA astronaut Chris Cassidy and Russian cosmonauts Alexander Misurkin and Pavel Vinogradov, the newest crew members to head for the space station. Their trip is taking six hours rather than two days, thanks to a more exacting strategy for orbital navigation. The Soyuz launch from Russia's Baikonur Cosmodrome in Kazakhstan is scheduled for 4:43 p.m. ET, and arrival at the station is set for 10:31 p.m. ET.

Mike Suffredini, NASA's space station manager, said the flight plan has the benefit of reducing the "amount of time the crew has to spend in a small environment before they get to the ISS." But that six-hour trip will be more intense.

Long stretch in the suits The trio will be wearing their Sokol pressure suits as an essential safety measure, to ensure against the kind of catastrophe that killed three unprotected cosmonauts in 1971 when their cabin suffered an air leak. But the suits are notoriously uncomfortable: They're designedto fit snugly into the tight crew seats, where knees are shoved halfway up to the chest. Arm mobility is restricted to being able to hold a stick to poke critical controls. Oxygen is fed into the suits via short hoses from a nearby console.

It takes hours to remove the suits and clean them, and at least an hour to put them back on and verify pressurization. There's not time for all that during a six-hour trip. As a result, the crew members will have to wear the suits for a much longer period that begins before launch and doesn't end until after docking.

"They are definitely going to have to go to a very tolerant mental system to do this," one former NASA astronaut told NBC News. The spaceflier, who has experience with Soyuz hardware and the Sokol spacesuit, spoke on condition of anonymity because he wasn't authorized to speak out publicly.

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Revised ride to space station may be faster – but it's also less comfortable