What Is The Descent Rate To Be Weightless? Options

[colinboyd]

What is the exact descent rate so that you are weightless? Not so that you are pinned to the roof, but weightless.

We've all seen footage of people inside cargo planes, messing around whilst weightless.

Has anyone experienced being weightless?
I have heard of people getting a trip up in an RAF Puma & the loadmaster spinning around the centre pole in the back whilst weightless.

[galaxy]

What is the exact descent rate so that you are weightless?

Zero G-force is the only factor you need to have.
http://en.wikipedia.org/wiki/Zero_g

[glnflwrs]

See this for a complete definition.....


http://en.wikipedia.org/wiki/Weightlessness

[cobzz]

Raise you're hand, then let it fall.

The moments you let if fall, it is in Zero G, however once it stops accelerating (going down), it won't be in Zero G anymore.

Oh and yeah I've been in zero G before. In a Cessna 172 we pitched up to 15degrees nose up then we pushed nose forward.

[Doug J]

Raise you're hand, then let it fall.

The moments you let if fall, it is in Zero G, however once it stops accelerating (going down), it won't be in Zero G anymore.

Oh and yeah I've been in zero G before. In a Cessna 172 we pitched up to 15degrees nose up then we pushed nose forward.

Any airplane will do weightless zero G maneuvers. A J3 will and a B747 will. Try not to do it in a plane with a head or it will get messy. No stress on the airplane and floating around in the cabin is a lot of fun. It doesn't last long or you have to deal with a dive which coulld cause stress. Do it once or twice to get the thrill then go on to more productive ventures. My favorite was in a D18 twin beach with friends in back. Lots of room to float around for a few seconds.

[Archangel]

Alot of it has to do with rate of change. Think of it this way, if you slowly pitch down it doesnt matter how fast you fall you wont become weightless. However if it is somewhat abrupt you will experience zero or negative g's. Its a good thing speed isnt the only factor in gravity, because if it was you would die from flying in a commercial jet. Excess g's are one thing that keeps space travel from becoming efficent even if we can go fast enough. The reason is if you were to accelerate to lets say 200,000mph you would have to do it over a long time period or you would be crushed to death with the g-load. Imagine how long it would take if you could accelerate to light speed in a way that would not kill you.

Ive talked to some C-17 loadmasters and they say you don't go weightless in combat decents because the pilots don't just force the nose down immediatly but let it come down at a reasonable rate, and even at more than 10,000fpm decent you could walk around(not recommended).

[cobzz]

10000feet decent rate is pretty fast

[TAL1440]

The reason is if you were to accelerate to lets say 200,000mph you would have to do it over a long time period or you would be crushed to death with the g-load. Imagine how long it would take if you could accelerate to light speed in a way that would not kill you.

Yeah I read somewhere 20G's will make you bleed from the ears then you will die upon reaching 40.

[charliepapa]

You'll die about 10 G. Most people pass out at around 9, so if your unconcious you wont be doing your special breathing techniques... so yeah. Yead die. Just to add.. doing 5 G blinking hurts (from experience). I don't know how someone could go all the way up to 9.

[Odyssey2001ACC]

On the planet Earth, acceleration due to gravity is -9.8 meters per second per second. What this means is that if you jump off of a bridge (in a vacuum) by the end of the first second you will be traveling 9.8 meters per second, at the end of the second second you will be traveling 19.6 meters per second and so on (exponential growth).. To achieve this in an aircraft it is necessary for the aircraft's descent rate to equal that of gravity (accelerating descent rate). While it is possible to do so by simply nosing over and diving it is possible to sustain the weightlessness much longer by climbing steeply prior to nosing over, doing this causes you to have a positive velocity (altitude above earth increasing) prior to actually being pulled towards Earth. You can think of it as being shot out of a cannon except you are enclosed inside of a tube traveling at your exact same speed and trajectory.
The flight path of an aircraft creating an optimum zero g environment will form a parabola which mathematically speaking is a graph defined by an exponential function simply put y=x^2 or in this case y=-9.8x^2 where x is time in seconds and y is distance traveled.

[Archangel]

You'll die about 10 G. Most people pass out at around 9, so if your unconcious you wont be doing your special breathing techniques... so yeah. Yead die. Just to add.. doing 5 G blinking hurts (from experience). I don't know how someone could go all the way up to 9.

No 10 g's wont kill you. Maybe you should do some reasearch. There have been people who sustained 13 g's in centrifuges. Not only that a crash in nascar can generate 80-100 g's and plenty of people survive that. What affect g's have on your is directly related to how long your being affected by them. You may easily survive 100 g's for 1/00 of a second but easily die at 20 for 10 seconds. It's also a factor of negative vs positive. Positive g's won't usually kill you because its just a lack of oxygen to your brain that causes you to pass out, which is where the death from g's comes from. That is until you get to an amount that causes bodily damage, then the death comes from internal and external damage.

Now when it comes to negative g's its much easier to die because blood is rushing to your brain and blood vessesls will pop quite easily with anything over 7 negative g's if its sustained. I'd say 10 negative would kill most people.

Now the anti G-strain techniqe does give an additional 3-4 g tolerance wich is why pilots can take 9 g's like its nothings(along with the g suit when your above 7 g's). Interestingly enough the blue angels fly with no g suits and they go up to 7.5 g's. The thunderbirds go up to 9 g's so they use g suits which make thier flying a little sloppier(notice how much closer and smoother the angels fly).

Any questions?

[AName]

Alot of it has to do with rate of change. Think of it this way, if you slowly pitch down it doesnt matter how fast you fall you wont become weightless. However if it is somewhat abrupt you will experience zero or negative g's.

Actually, you don't even need to pitch down as hard as you think. The first time I tried it out, i pushed to hard and everything in the right seat started heading up towards the ceiling. With a high pitch attitude, you'd be supressed how slowly you push down for 0g. It really depends on how high your original pitch is.

[cobzz]

In 1954, Colonel John Paul Stapp Ph.D., M.D., a US Air Force flight surgeon
and researcher, sustained the highest voluntary g-accelerations of 45 times
gravity. This work was done to determine the design standards for safety
harnesses and ejector seats being developed at the time to cope with the
newest generation of supersonic jets. Dr. Stapp achieved this by riding a
rocket sled to 634 miles per hour and accelerating to a halt in 1.4 seconds.

After the test, he had burst capilarries in his eyes, and many other affects.

Some others:
* on 13 July 1977 British racing driver David Purley survived a deceleration from 173 km/h to zero in a distance of about 0.66 m, enduring 180 g (*)
* the beak of the red-headed woodpecker hits the bark of a tree with an impact velocity of over 21 km/h, subjecting the bird's brain to a deceleration of approximately 10 g when its head snaps back (*)
* when 'jack-knifing' into the air to escape predators, the click beetle averages 400 g (*)

[Ranger]

In 1954, Colonel John Paul Stapp Ph.D., M.D., a US Air Force flight surgeon
and researcher, sustained the highest voluntary g-accelerations of 45 times
gravity. This work was done to determine the design standards for safety
harnesses and ejector seats being developed at the time to cope with the
newest generation of supersonic jets. Dr. Stapp achieved this by riding a
rocket sled to 634 miles per hour and accelerating to a halt in 1.4 seconds.

After the test, he had burst capilarries in his eyes, and many other affects.

Some others:
* on 13 July 1977 British racing driver David Purley survived a deceleration from 173 km/h to zero in a distance of about 0.66 m, enduring 180 g (*)
* the beak of the red-headed woodpecker hits the bark of a tree with an impact velocity of over 21 km/h, subjecting the bird's brain to a deceleration of approximately 10 g when its head snaps back (*)
* when 'jack-knifing' into the air to escape predators, the click beetle averages 400 g (*)

Interesting post. I think I remember reading an article in "Air & Space" about Col. Stapp. Could you even imagine abusing yourself like that so scientists could poke around on you afterward?

[charliepapa]

No 10 g's wont kill you. Maybe you should do some reasearch. There have been people who sustained 13 g's in centrifuges. Not only that a crash in nascar can generate 80-100 g's and plenty of people survive that. What affect g's have on your is directly related to how long your being affected by them. You may easily survive 100 g's for 1/00 of a second but easily die at 20 for 10 seconds. It's also a factor of negative vs positive. Positive g's won't usually kill you because its just a lack of oxygen to your brain that causes you to pass out, which is where the death from g's comes from. That is until you get to an amount that causes bodily damage, then the death comes from internal and external damage.

Now when it comes to negative g's its much easier to die because blood is rushing to your brain and blood vessesls will pop quite easily with anything over 7 negative g's if its sustained. I'd say 10 negative would kill most people.

Now the anti G-strain techniqe does give an additional 3-4 g tolerance wich is why pilots can take 9 g's like its nothings(along with the g suit when your above 7 g's). Interestingly enough the blue angels fly with no g suits and they go up to 7.5 g's. The thunderbirds go up to 9 g's so they use g suits which make thier flying a little sloppier(notice how much closer and smoother the angels fly).

Any questions?

Yeah, I meant a sustained period and with no G-Suits. Also, its negative G that pushes blood TO the brain, its positive that draws it AWAY. Thats gonna starve your brain...

[Archangel]

Yeah, I meant a sustained period and with no G-Suits. Also, its negative G that pushes blood TO the brain, its positive that draws it AWAY. Thats gonna starve your brain...

Now when it comes to negative g's its much easier to die because blood is rushing to your brain and blood vessesls will pop quite easily with anything over 7 negative g's if its sustained. I'd say 10 negative would kill most people.

That was in my post. Aint it amazing how many g's people can take under extreme circumstances.

[TAL1440]

Are G's from acceleration considered negative or positive?? I'd only assume positive?

[bernoulli]

Are G's from acceleration considered negative or positive?? I'd only assume positive?

A good rule of thumb:

Blood forced towards feet, positive G. Blood forced towards head, negative G. It all depends on the direction of the acceleration forces relative to the individual.

[Jorge]

You'll die about 10 G. Most people pass out at around 9, so if your unconcious you wont be doing your special breathing techniques... so yeah. Yead die. Just to add.. doing 5 G blinking hurts (from experience). I don't know how someone could go all the way up to 9.

You can't die from only 10 G's! Fighter pilots routinely pull more than this. Pilots at the red bull air race were pulling 13 G's at some points.
Also you have to be careful doing zero G maneuvers in a plane like a cessna 172 with a gravity fed fuel system. No gravity=no fuel going to the engine=bad day. ;)

[mpeterson]

I probably shouldn't spout this since talldude is on these forums and hes a nark, but the arrow makes great for getting and staying 0G