Basejumper.com - archive

First catapult uses a dummy, second catapult some guy with a BASE rig. Wonder how many Gs he pulled...

http://video.google.ca/...2488&q=catapulte

I read somewhere it was around 9? I have no clue

I like the 'Confidential' watermark on the video.

That's funny.

I'd think the G-load would be some higher than that, although for a very brief interval. Stapp's tests said a human body properly supported (That being the key phrase here) could sustain up to 42 g briefly.
I think I read that the guy at Perris last week showed something like 30 g of acceleration.
If you had the speed from launch to apogee and the altitude attained, the g load could be determined, but it would require a better math whiz than me.

http://fishki.net/...8/video/catapult.3gp


same

I did not look this up BUT I would think
that 42 Gs would make a person brown out!!

There is a bungee slingshot ride located in Panama
City Beach, FL (aka the Redneck Riveria) which
oddly enough is run by Jesus-freaks.

Anyays, during various Spring Breaks visits I have
ridden the bungee slingshot 6 times with different
friends. The force was definitely note worthy but
I highly doubt it was anywhere near 42 Gs.

Maybe some of you hardcore science/math guys can
run the numbers. The two towers were 175 feet tall
and the passengers reached the top within 2 seconds.

Ye, this is quite old.

It's a friend of mine, Jean-Marc Mouligné. He is in Cuba at the moment looking to open some jumps there (his wife is Cuban) and doesn't have reliable connection otherwise I'm sure he would chip in.
I did quite a bit of work with him and the other guy in that vid last year movie set building.

He used steel cables with a counter weight since bungee cord was too unpredictable.
Also, keep in mind that he was lying down and not sitting down, so no black out. Besides, he mentioned that the g's were really negligeable.

Here's an Email I was sending around at the time:

"Hi all,

As most of you know, a friend of mine Jean-Marc Mouligne catapulted
himself 150 metres in the air.
Let me tell you the whole story from the start (again for some of you).
I got a call about a year ago from Karl, one of the senior base jumpers
down here for those of you who don't know him, in fact he is one of the
fathers of base in our country. Any way, he told me there was a french
guy down here looking to do some jumps. I was a little worried because
I had read some of his posts on the french forum and they seemed a bit
dodgy. He was doing special effects for a movie down here and had a
couple of weeks holiday after that. I met up with him and brought him
to my house for supper. He only had one jump so I recommended he go
stay with my friends near the Bloukraans bridge and get some jumps off
there before jumping off our mountains. He did just that and came back
after a couple of weeks or so and stayed with us for a week before
leaving for France. This is when I really got to know him.
The guy is 55 and has had a full, different life. He worked in the
circus, spent some time in the Amazon, worked with explosives in the
army, also did a few jumps there and then got into the movie industry
doing special effects. The guy is nuts. I don't mean this in a bad way
but more in a mad scientist kind of way. For the last couple of years
or so he got it into his head to be the first man catapult himself into
the air and land safely. All of his money went into it. He sold his
house, cumulated loads of debt, etc just to get to his goal. After
loads and loads of testing, he finally got into his catapult and
launched himself. It must be the funniest thing I have ever seen,
unbelievable! He got it right. He went through a lot to get his crazy
idea working. Many people in the base community thought he was going to
kill himself and I must admit that this is why I was a bit worried at
first. We always, with good reason, are weary of this type of thing.
Only once I got to know him did I realize that he is far from being an
idiot.
Jean-Marc recons that the G-force was negligeable and that on the next
shot he could easily get 200 metres up.
Well, at the moment he is looking for sponsors. I know it is a long
shot but I am just putting the word out there. If you or anyone else
hears of some organisation that would be interrested, let me know and I
will put you in touch with him.
Later
Borat"

At the moment it seems the project is out of his hands mainly I think from loss of interest on his part.
A very cool guy though.

I had a heated discussion about this with Gunnar when we were having dinner in Twin a while back. He's a race car driver and argued that he had been subjected to incredible G-forces. I thought he was exaggerating but he made me consider that Gs are a vector (duh, they're a force, I should have realized this), so without a time-component you can't say much about the physical experience. Remember, the human body experiences Gs because different parts of your body (blood, organs, etcetera) are displaced at different velocities. In other words, 42 Gs for only one nanosecond would be unnoticable for everybody, whereas 6 Gs for ten seconds would be mildly uncomfortable for most.

That said, 42 Gs sounds a little high to me for another reason. I'm too lazy to do the math, but to generate 42 Gs for even a short amount of time you'd need a lot of energy stored. My intuition tells me you wouldn't get that from those elastics. But again, I haven't done the math.

Btw, Gunnar; so I believe you now...

Edited to fix grammar.

Absolutely. Compare two people: Person 1 walks into a wall at a brisk walking pace of 2 m/s, his head slowing to zero in a matter of millimeters; person 2 is slowed to a stop from 150 km/h (41 m/s) over a foot or two.

Assuming constant acceleration, they will experience comparable accelerations, on the order of a few hundred g's. The first will feel it for milliseconds. The second will feel it for tens of milliseconds. My experience has been that being person 1 is a lot more fun than being person 2.

Edit to add: Equations, for those who care:
a = v^2 / 2d
t = 2d / v

Oh, and I'll call BS on the 42 g's. To reach a maximum altitude of 150 m, one needs to leave the catapult at about 55 m/s. To accelerate to that speed at 42 g's would take less than 4 m. Admittedly, the acceleration isn't constant, but given that the towers were ~50 m tall, the average acceleration would be about 3 g.

Another edit... Better estimate: if we assume the bungees act as Hooke's-law springs (we could do worse), then the numbers above give an initial (ie, maximum) acceleration of about 6 g.

Hey Fellas,

Still too lazy to do the math myself BUT
not so lazy that I can't do a few searches.
According to the websites below brown and
black outs usually occurs between 4 & 8 Gs.

http://en.wikipedia.org/wiki/G-LOC

http://hypertextbook.com/facts/1998/PhillipAndriyevsky.shtml

Most interesting piece found was this excerpt:

The most G-force that a human being can withstand and survive is around 9G. An exact G amount cannot be determined because everyone's body is different, and the combination of weight, height, and build has an influence on the way the force reacts and the amount of G's that body can withstand. 9G means that a pilot is undergoing a force 9 times that of Earth's gravity. If he weighs 175 pounds, he will suddenly feel as if he weighs 1,575 pounds.

http://library.thinkquest.org/C002926/science/gforce.html

Jean-Marc has not told me he knows any Kazachs.

no bungees, just steel cable; big disfference aparntly.

....so now you kno

Think more. Black-outs occur when blood drains from your brain for long enough that your brain stops working. Direction matters. When the force goes from your face to the back of your head, there's no where for the blood to go. He was laying down.

Also, the Red Bull Air Race was reporting that on some courses the pilots where experiencing up to 14 g's for periods of up to 4 to 5 seconds. And they don't wear g suits.

Formula 1 crash tests require that the structure subjects the driver to no more than 90 some g's for a period of no longer than somenumber of milliseconds. Time matters. Instantaneous g's is way different than sustaned.

My bad. Replace "bungees" in the above with "thing that does the work". By any name, unless the thing that does the work does all or nearly all of it in the first four metres, 42 g's is out of the question. If one assumes that the 50-metre cranes aren't merely for show, so that the work is done more-or-less evenly over most of that distance, then the ~5 g estimate holds.

That's an expensive jump ticket, but must have been very naiis.

About the g's, motorcycle helmets have about 300 g's as peak limit in tests. That's right, 300!
For example, for the Snell M2000 test standard, the impact speed is 7.75m/s which is the end speed after about 3m free fall.
The DOT standard even allows 400 g's peak, but _only_ 200 g's over 2/1000 of a second.

The duration is really the key when talking about g's. 200 g's during 2 ms gives a displacement of about 4 mm (~0.16 inches).
So that's about how much your brain will be compressed against the inside of your forehead if you put on a DOT helmet and jump head first from 3m onto a concrete floor...

And a reference for non-believers:
http://www.smf.org/...ds/pdf/mstds_cmp.pdf

you're right, it's about 5g.

i'll try get hold of him again see if he could chime in. but as i said he very difficlt to get hold of these days.

5g it was:
http://www.dropzone.com/...post=2034882#2034882

I can do the calculations when I get a free moment. I am in my last semester of collge to working on my Bachelor's of Science in Mechanical Engineering.


Bernt is 100% right about motorcycle helmets. I had to do a project on them lats semester. But as he posted, the impact time is only 7.75 ms. That is 0.00775 seconds! Our teacher told us that head trama occurs the most in the first 200 ms or 0.200 seconds.

In another note, he is laying down teh propper way. You would not be able to sit upright as in a chair and do this. The spine cannot take the loading along its axis. This is why the astronauts lay back when being launched into space. Does anyone know how many g's the space shuttle pulls? It would be up there!

DAVE

all i know bout g's is what i read here and seen on tv...
but i would think the catapult g's are similar to when jets take off from ships. no?

WHAT DOES ALL THAT MEAN IN INGLISH

Newton's secnd law is F = m * a. That is the sum of forces equals mass times acceleration. So if you were to calculate your weight, you would use your mass times gravity. Every single day, every one of us experiences one g, the force of gravity. So when you experience say two times the force of gravity, you are experiencing 2 g's. It is a way of expressing acceleration in terms of gravity. In teh formula above, just plus in (n*gravity). The "n" represents the number of g's. Gravity is equal to 9.806 m/s^2 or 32.174 ft/s^2. Acceleration is also defined as the change in velocity divided by time. So say you were at a stand still like the catapult guy and then reached a speed of 100 ft/s in 10 seconds, you acceleration would be 10 ft/s^2.

That's a real basic explanation. You should also consider that if you're doing 90ft/s after 1 second, and then doing 100ft/s after 10 seconds, your acceleration isn't a constant 10ft/s^2 over that 10 seconds.

Basically what I'm getting at is since it's a curving scale not a straight line, you'd need more info to figure out the initial and peak acceleration, and you'd need that to figure out the peak g's.

According to my vague memories of math from
grad school....To find the rate of change at a given point
along a non-linear function requires taking a derivative.

After a little more research I found that my opinions
expressed in my earlier post about the max G-Force
the body could withstand was wrong.


____________________________________________
Strongest g-forces survived by humans

Voluntarily: Colonel John Stapp in 1954 sustained 46.2 g in a rocket
sled, while conducting research on the effects of human deceleration.
See Martin Voshell (2004), 'High Acceleration and the Human Body'.

Involuntarily: Formula One racing car driver David Purley survived
an estimated 178 g in 1977 when he decelerated from 108 mph to
0 in a distance of 66 cm (26 inches) after his throttle got stuck wide
open and he hit a wall.

Yeah you are right. To find the min or max of any mathematical function, you must take the first derrivative of the mathematical formula and then set that first derrivative equal to zero. Then solve for the varible you took the derrivative of.

d-gold, I was just giving the deffinition of Newton's second law and how "g's" were determined. I didn't go into the mathematical formula of acceleration.

What you are talking about is whether that formula is either linear or nonlinear. The basic deffinition of acceleration is the change in velocity devide by time. Remember the deffinition of velocity is the change in position divided by time.

Here is a good website:

http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

I heard average is like 8G's and the highest point was 13G after 0.2sec.

Right!
We measured some 4.5 G for some 40 meters.
They apply perpendicular to the body, and don't drain the brain dry.

hehehe
you're back from Cuba.