How much g-force endurance average human have?

[Pawelk198604]

I heard that Apollo Astronauts have endured 7 G during reentry phase, it's quite lot, it's probably speed in returning from moon it so high.

I wonder does when space tourism become reality, the scientist find way to reduce Gees on return from Moon trip

[K^2]

Apollo did direct re-entry, which means the ship plummets into the atmosphere at the speed it gained "falling" from the Moon. All that speed has to be bled off in atmosphere, which there isn't a whole lot of. Hence the high G loads.

7G is not the limit of human tolerance, though. 8G+ is not unheard of for fighter pilots. Aircraft carrier take-off is going to be in the 6-8G range. Higher G loads can be pulled for certain maneuvers.

Another factor is duration. Tens of G are entirely survivable if the duration is very short. It takes quite a bit before you start having actual tissue failure. Typically, the first thing that happens is the pilot blacking out due to blood pooling at the extremities. If this condition is maintained for too long, brain damage can occur, followed by death. At higher G loads, you can have blood vessels rupture in even shorter time, which can also lead to severe injuries or fatalities. All depends on how long the acceleration is maintained, what orientation the pilot is in, and whether you have any special seats and/or suits to assist him.

The highest load I've been under is 3G. It's not that uncomfortable, and would be entirely acceptable for space tourism. You might be able to get away with 4 or 5 for a short duration. But anything higher than that, you need special training, special suit, etc., and that doesn't really work for commercial space flight.

As far as ways to reduce the G loads on re-entry, all you have to do is slow down with engines before you drop into atmo. That can be expensive, but presumably, if you are doing commercial space flights, you have the overhead to do that.

[lobsterbark]

I believe the world record was around 400-500gs, but it was for less than a millisecond, and the guy that did it is paralized. The most the average person can survive, provided that there perfectly healthy, and they have the proper suit/seat/harness ect, is 15, for a couple seconds. They would be bruised, and not very happy, but they would survive.

[Awaras]

They had to endure 7G's because they had only one shot at reentry - They could have made a more gradual reentry by aerobraking several times, making a full orbit between the aerobraking maneuvers but each orbit would take several hours and the command module did not have enough power and air to sustain the astronauts for more than a few hours so they had to do it in just one attempt.

Edited May 5, 2013 by Awaras

[SunJumper]

I asked my Physics teacher this last year, but for a period of days (constant acceleration trajectories and whatnot), and he responded as about 2.5.

[Tommygun]

This might be a useful reference:

http://en.wikipedia.org/wiki/John_P._Stapp

John Stapp did a number of rocket sled experiments involving G force.

Edit: The problem isn't really about G forces, but motion sickness for tourism though.

Edited May 5, 2013 by Tommygun

[Pawelk198604]

The highest load I've been under is 3G. It's not that uncomfortable, and would be entirely acceptable for space tourism. You might be able to get away with 4 or 5 for a short duration. But anything higher than that, you need special training, special suit, etc., and that doesn't really work for commercial space flight.

The rollercoaster ir the aeroplane

[tavert]

A few years ago when they were doing the Red Bull Air Races (aerobatic planes), they had to institute a rule for safety that the pilots couldn't exceed 12 G's. The planes are capable of that for reasonably short maneuvers, some of the pilots did get disqualified on a few occasions for breaking that rule.

[K^2]

The rollercoaster ir the aeroplane

Airplane. An old fighter trainer. They only let me do a few simple maneuvers, "high" G turn being one of them. Instructor showed me a few others, though.

Do any roller coasters actually pull 3G? I mean for any significant duration. The fastest linear accelerator one I've been on was the Top Thrill Dragster in Ohio, and that thing only pulls something like 1.3G average over 4 seconds, so maybe peaks at 2G? I suppose, one can do a bit more on the loops, but again, nothing I ever rode felt close to 3G.

Edit: After looking around, it seems that some coasters do pull up to about 4G. I need to find me one of these.

Edited May 5, 2013 by K^2

[Pawelk198604]

Airplane. An old fighter trainer. They only let me do a few simple maneuvers, "high" G turn being one of them. Instructor showed me a few others, though.

Do any roller coasters actually pull 3G? I mean for any significant duration. The fastest linear accelerator one I've been on was the Top Thrill Dragster in Ohio, and that thing only pulls something like 1.3G average over 4 seconds, so maybe peaks at 2G? I suppose, one can do a bit more on the loops, but again, nothing I ever rode felt close to 3G.

Edit: After looking around, it seems that some coasters do pull up to about 4G. I need to find me one of these.

It was probably hard to breathe to you, huh

Did you have pilot license?

If I had the money, I would make the pilot license

[K^2]

It was probably hard to breathe to you, huh

Did you have pilot license?

If I had the money, I would make the pilot license

Like I said, there wasn't a lot of discomfort at 3G. I mean, if I had to move about significantly, that'd probably be tough. But as far as just maintaining control of the aircraft and breathing, it wasn't bad at all.

And no, I don't have a license. I don't have enough hours at the moment, and just now I can't afford to get more flight hours. So getting the license will have to wait. I've completed the ground part of the flight classes at my university, however, back when I was able to take classes for free. All of my paperwork is out of date, of course, so I'll have to take the exam again, but I shouldn't need to sit through ground school again.

[Moach]

i hear 4~5g's is considered among roller coaster designers to be a good general 'design ceiling' for such loads...

remember, those things are designed for some the broadest definitions of the 'general public' you'll find in engineering, so that should give you a good guess of how much force you can put a 'normal' person through and still have them willing to pay to go again

3 g's is really not bad, you can get that on an average theme park ride - you'll feel it, no doubt - and you might find that it takes a non-trivial amount of effort to keep your head facing up straight... but breathing is still largely unaffected at this point

now, airline pilots are expected to try their best to avoid going out of a 0~2g 'window' -- anything outside of that range is considered rather extreme flying conditions

and remember, fighter pilots can reach 9g's and still maintain control because of some VERY intense training and the use of G-suits which inflate when high loads are detected by the aircraft (those compress one's legs to keep blood pumping to the head, rather than pushed down to one's feet)

astronauts undergoing 7g's have that force directed mainly along their Z axis (that's the direction they're sitting towards - aka 'up' for someone watching the launch from the ground)

now, direction is quite important for how much G's a person will take before becoming less productive than what his/her boss would require - astronauts sitting 'towards' the forces general direction wouldn't have to worry about blood rushing to their feet... nor race car drivers worry suchwise during high performance turns

fighter pilots in dogfights put their loads on the Y axis - and that indeed can be bad for, you know... staying alive

[Nao]

High g's aren't problem in roller coaters as its only for a second or two, and the short straights between turns are enough to make blood return where it should be.

The problems start when the duration of high acceleration increases.

I flew gliders some years ago and almost experienced a blackout (it was a greyout into almost not seeing the instrument's) in a long spiral, flying only 3,5 - 4g. I didn't had accelerometer installed but deduced it from bank angle. It didn't felt more than what's on a roller coaster but it the duration was more than 30s. It felt like if i continued i could lost vision completely (although it could be me tightening the turn).

Here's some info from nasa's pages.

With todays launching and return methods i think it would be perfectly possible to keep acceleration below 3-4g so most people could go to space. Especially if they would be lying perpendicular to acceleration force as Moach mentioned.

[WestAir]

now, airline pilots are expected to try their best to avoid going out of a 0~2g 'window' -- anything outside of that range is considered rather extreme flying conditions

In the aircraft I fly, I believe the limits were 2.5 positive G's, -1.0 negative G's in a clean configuration (no flaps). Honestly, it's extremely extremely easy to pull higher G's the heavier an aircraft becomes.

That said, I absolutely hate G forces. At something as low as 2 G's I already feel like I want to curl up into a ball. Those Red Bull pilots pulling 12+ G's earn my utmost respect.

[Tech_Spec]

That said, I absolutely hate G forces. At something as low as 2 G's I already feel like I want to curl up into a ball. Those Red Bull pilots pulling 12+ G's earn my utmost respect.

I agree, the worst I've ever experienced was a particularly nasty 3.something g turn in a little Cessna 182. Made worse by the fact I was kneeling on the floor of the bloody thing at the time (no seats - skydiving plane).

[tavert]

Hey look, G numbers for roller coasters: http://physicsbuzz.physicscentral.com/2013/04/roller-coaster-g-forces-weve-got-data.html

[lyndonguitar]

This might be a useful reference:

http://en.wikipedia.org/wiki/John_P._Stapp

John Stapp did a number of rocket sled experiments involving G force.

Edit: The problem isn't really about G forces, but motion sickness for tourism though.

"Stapp" oh man the name really fits, a.k.a. an Aptronym

[jason0735]

I believe the world record was around 400-500gs, but it was for less than a millisecond, and the guy that did it is paralized. The most the average person can survive, provided that there perfectly healthy, and they have the proper suit/seat/harness ect, is 15, for a couple seconds. They would be bruised, and not very happy, but they would survive.

Lob that would kill anyone even if it was for just picosecond (10 to the power of -12 of a second) so unless you have proof then I don't believe you NecroThreadMancer

[Gniuz]

World Record: 82.6g for 0.04 seconds by American Eli L. Beeding Jr. in 1958. He spent 3 days in the hospital afterwards.