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  • - This is the Royal Air Force training centrifuge at Farnborough.

  • And the team here are going to push me

  • as far as they're allowed to push a civilian.

  • - The centrifuge has been here since 1955.

  • The device was originally installed for research purposes,

  • although these days it's used for training as much as it is for research.

  • What it does is recreate the forces that you feel in an aircraft.

  • For our routine pilot training, the first time pilots go on the centrifuge,

  • we expect them to get up to 5g without a g-suit,

  • and then up to 7g with an anti-g-suit.

  • - Now I'm not taking a significant risk here.

  • I'm healthy, I've pulled a few gs before.

  • And the human body can take this.

  • And the reason we know that is because in the 1950s,

  • the US Air Force used rocket sleds to push volunteers to incredible speeds.

  • But that rocket-powered acceleration wasn't the dangerous,

  • or even the really high-g part of the test.

  • See, high-g acceleration takes a lot of incredibly expensive rockets

  • or a big ol' centrifuge like this.

  • But high-g deceleration?

  • All you need for that is a wall.

  • Or for something less destructive, like the rocket sleds,

  • you use scoops dropped down into a water trough.

  • USAF flight surgeon John Stapp,

  • aboard the rocket sled Sonic Wind Number One,

  • holds the record for the highest sustained g-force

  • anyone has ever voluntarily endured,

  • 25g for 1.1 seconds, with a brief peak over 46g.

  • And he was badly injured, but he survived

  • and he recovered and he lived to the age of 89.

  • The human body is an incredible thing

  • particularly because we didn't evolve for this.

  • - G-tolerance is something that's innate in all of us.

  • Some of us have high G-tolerance. Some of us have low G-tolerance.

  • Over the years, people's g-tolerance doesn't really adapt.

  • Any shortfall in g-tolerance has really got to be made up

  • by physical exertion and the g-straining manoeuvre.

  • - What this centrifuge doesn't have is much jerk.

  • And jerk is a technical term.

  • In the same way that acceleration is the rate of change of speed,

  • jerk is the rate of change of acceleration.

  • And because it takes time to spin up and spin down...

  • Oh, here we go! Even though the acceleration is high,

  • the jerk here is relatively low, about 1g per second.

  • Jerk is the difference between a rocket to space

  • which might take a couple of minutes to reach peak acceleration

  • and a fighter jet, where manoeuvres might change the G force acting on you

  • in a fraction of a second.

  • And it can go further than that.

  • You can measure the rate of change of jerk which is called snap or jounce.

  • The two derivatives after that are called crackle and pop but

  • they're not all that useful in the real world.

  • - As we increase the G that Tom is exposed to,

  • the blood's going to be pushed down into his feet,

  • and he's going to have to work really hard to push that blood back up

  • to feed oxygen to his brain to keep him conscious.

  • And in real life, we would be expecting that person to be flying an aircraft whilst doing that.

  • - I'm getting a little bit of grey-out.

  • I can't quite see. Agh.

  • - We teach the anti-g straining manoeuvre which composes of two separate parts.

  • First of all, muscle tensing,

  • so both the buttocks and legs squeezing the blood vessels

  • to try and get the blood back up into the chest and the head.

  • But also the second part is a breathing manoeuvre

  • which increases the strain in the chest

  • directly increasing the blood pressure to the great vessels in the chest

  • and keeping him conscious.

  • And when you lose blood pressure to your head,

  • you could even lose consciousness.

  • And we term that g-induced loss of consciousness or G-LOC.

  • [gasping]

  • - Blimey!

  • I lost everything there.

  • Wow.

  • - G-LOC in itself is not dangerous.

  • But the real point is when you G-LOC you're flying an aircraft.

  • So if you're not able to fly that aircraft,

  • I'm sure you can appreciate that that is a real problem.

  • - Because of John Stapp and all the volunteers like him

  • that rode the rocket sleds,

  • there is a lot of research

  • into acceleration on the human body.

  • How many gs can be withstood for minutes at a time?

  • How many gs can be withstood for brief moments?

  • And how many can be withstood with training that I clearly don't have.

  • Rocket scientists and roller coaster designers use that data.

  • But there's not much research into jerk

  • because how do you test it without also testing acceleration?

  • Over on the Starrship channel, I am not passing out

  • pulling gs with the Blades aerobatic team(!)

  • And as for this video, thank you so much

  • to all the team at the RAF Centre of Aviation Medicine,

  • to the team at Qinetiq, and to the team at Starrship.

- This is the Royal Air Force training centrifuge at Farnborough.

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G-Force、Jerk和在離心機中暈倒 (G-Force, Jerk, and Passing Out In A Centrifuge)

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    林宜悉 發佈於 2021 年 01 月 14 日
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