WEBVTT
Kind: captions
Language: en

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

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And the team here are
going to push me

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

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- The centrifuge has been here since 1955.

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The device was originally installed
for research purposes,

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

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

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

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

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

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

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

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And the human body can take this.

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

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

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

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

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

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or a big ol' centrifuge like this.

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But high-g deceleration?

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All you need for that is a wall.

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Or for something less destructive,
like the rocket sleds,

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you use scoops
dropped down into a water trough.

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USAF flight surgeon John Stapp,

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aboard the rocket sled
Sonic Wind Number One,

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holds the record for the
highest sustained g-force

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anyone has ever voluntarily endured,

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

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And he was badly injured,
but he survived

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

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The human body is an incredible thing

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particularly because
we didn't evolve for this.

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

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

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

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

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by physical exertion
and the g-straining manoeuvre.

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

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And jerk is a technical term.

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

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jerk is the rate of change
of acceleration.

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

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

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

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Jerk is the difference
between a rocket to space

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which might take a couple of minutes
to reach peak acceleration

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

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in a fraction of a second.

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And it can go further than that.

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

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The two derivatives after that are called
crackle and pop but

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

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

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

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

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to feed oxygen to his brain
to keep him conscious.

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

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

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I can't quite see. Agh.

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

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First of all, muscle tensing,

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so both the buttocks and legs
squeezing the blood vessels

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

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But also the second part
is a breathing manoeuvre

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which increases the strain in the chest

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

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and keeping him conscious.

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And when you lose
blood pressure to your head,

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you could even lose consciousness.

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

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[gasping]

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- Blimey!

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I lost everything there.

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Wow.

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- G-LOC in itself is not dangerous.

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

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

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

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- Because of John Stapp
and all the volunteers like him

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that rode the rocket sleds,

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there is a lot of research

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into acceleration on the human body.

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

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How many gs can be
withstood for brief moments?

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

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Rocket scientists and
roller coaster designers use that data.

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But there's not much research into jerk

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because how do you test it without
also testing acceleration?

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Over on the Starrship channel,
I am not passing out

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pulling gs with the
Blades aerobatic team(!)

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And as for this video, thank you so much

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

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