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Zero-G Flight

04/30/2007 8:28 AM

Zero gravity flight by Stephen Hawking, does it mean fly with an aeroplane to somewhere within no gravity inside like in aerospace? how could? and what's the aeroplane like that can make it possible?

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#1

Re: zero-G flight

04/30/2007 10:03 AM

When you are free falling, you are in zero gravity. It's kind of like the difference between standing against an ocean current (gravity) and drifting with the current (falling). When you're falling you don't feel the gravity. Or, when you go down in an elevator and you feel lighter - due to feeling less gravity. So, the airplane goes up, then dives toward the ground - during the dive you're essentially falling, so there's no gravity.

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#14
In reply to #1

Re: zero-G flight

05/03/2007 5:07 PM

"When you are free falling, you are in zero gravity"

Where did you get this nonsense from? If it is Zero gravity why are you falling?

Which one of your six senses is "feeling" gravity?

A load of bull.

Wangito.

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#15
In reply to #14

Re: zero-G flight

05/03/2007 5:23 PM

Let me rephrase - when you are in free fall, you're not experiencing gravity. You are moving with gravity, and not reacting against it, thus you have no experience of it. On the ground you certainly feel the reaction of your body against the gravity - that thing we call weight.

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#2

Re: Zero-G Flight

04/30/2007 11:42 PM

Here is an article for you to consider. Zero Gravity Flight

fm!

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Anonymous Poster
#3

Re: Zero-G Flight

05/01/2007 6:20 AM

The plane flies a parabolic trajectory (path), as if it were a ball tossed into the air. Everything inside follows that same trajectory.

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#4

Re: Zero-G Flight

05/01/2007 10:58 AM

Google Vomit Comet

It was a KC-135A that NASA used to train new astronauts in zero-g. The aircraft is now retired. Here is a diagram of how maneuver is made to reach zero-g in for 25-30 seconds in flight.

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#5
In reply to #4

Re: Zero-G Flight

05/01/2007 1:06 PM

I would think that the period of perceived zero G would be from the time the plane went nose low until the pilot started the pull-up maneuver. Not during the period of level flight between the climb up and the beginning of nose low.

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#6
In reply to #5

Re: Zero-G Flight

05/01/2007 2:08 PM

I thought so, too - but apparently this diagram is correct.

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#7
In reply to #6

Re: Zero-G Flight

05/01/2007 2:53 PM

If what the diagram says is correct, every body without a seat belt on would float out of their seats once the airplane leveled off. The food and beverage carts wouldn't roll in the aisles, they would float, the flight attendants wouldn't walk down the aisles, they would float pulling themselves along by grabbing onto the seats, they would brake themselves the same way. I wouldn't even want to begin contemplating what might happen in the washrooms. Even eating or drinking could get messy.

The diagram is plain bloody wrong!


While the plane is accelerating downwards at the speed determined by its speed at the top of the climb plus 32ft/sec2, the acceleration due to gravity a person will appear to be suspended in space, or weightless.

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#8
In reply to #7

Re: Zero-G Flight

05/01/2007 3:56 PM

Sorry, but I'm going with NASA on this one:

http://jsc-aircraft-ops.jsc.nasa.gov/Reduced_Gravity/trajectory.html

http://zerog.jsc.nasa.gov/home.html

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#9
In reply to #7

Re: Zero-G Flight

05/01/2007 4:54 PM

The diagram is correct - Try riding a roller coaster holding a glass of water between your legs and let me know when your pants get wet- Unless it happens while you are waiting in line.

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Anonymous Poster
#10
In reply to #9

Re: Zero-G Flight

05/01/2007 5:57 PM

It would happen to me some where on the roller coaster even without the glass of water.

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#16
In reply to #7

Re: Zero-G Flight

05/03/2007 7:31 PM

No Sir, You are bloody wrong!

1. Let's define "Acceleration", It is the change in speed per unit time. Hence, no change in speed, no acceleration. when your cars has a constant speed of 200mph in strait line it has no acceleration. but it's GRAVITY is still 1g.

2.When your car starts moving from 0mph to it's final speed, during all this phase it accelerates. This is called "positive acceleration". Your g is greater than one and you feel as if you are sinking in your seat.

3. When your car slows down from it's final speed to zero it "Decelerates" (This term is really wrong, but nicely demonstrates the idea). your G is still greater than one and you feel as if you are being thrown out of your seat.

There will be g forces greater than one, in any change of trajectory, even if you do not change speeds.

And here comes the airplane. Truth is that the diagram presented is somewhat misleading,

What happens at the left side of the dotted line: A positive g force will be strongly felt on the pull-up, and you will be sinking into your seat. and than, as the speed decreases during the climb, you (may) feel a slight negative g

What happens at the right side of the dotted line: Now the airplanes dives and it accelerates. you (may) feel a positive g. On the pull up at the end of the dive, again you will feel a stronger positive g. All this discussion is for the outside zones of the center dotted lines.

At the left side of the dotted line: At the end of the climb, the pilot will push over to fly a parabolic curve. and will keep pushing the stick until he reaches the right side of the dotted line where the airplane will start it's nose down dive without the pilot pushing the stick any more. All along the parabolic curve your pull-out force (from the seat,) and the pull-in force (into your seat) will be equal, and you will be in a state of suspension. or ZERO GRAVITY. Yes, you will be floating sir. And the diagram is bloody correct!

This is a simplification of a much complex movement, but I hope it does explain it in the simplest form.

Wangito.

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#11

Re: Zero-G Flight

05/02/2007 9:31 AM

I agree the sketch is correct. I experienced a short weightless experience once. It was during a fast landing maneuver.

The reason why the experience does not last all the way down is because the plane has to be placed in a recoverable trajectory. That is it must leave the free fall parabolic trajectory and continue in a straight line very soon after the diving starts.

Any strong sturdy craft should withstand the forces working on it while leveling of.

Some people may need more than a glass of water as an excuse.

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#12
In reply to #11

Re: Zero-G Flight

05/02/2007 4:47 PM

we actually don't feel gravity..we feel the reaction of the materials that we apply gravity by our body weight...so if you don't want to feel gravity you must not apply it..neither to air nor to ground...

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#19
In reply to #12

Re: Zero-G Flight

05/10/2007 7:30 AM

Ok i will rephrase: I did not apply any pressure to seat below me but pressed against the safety belt without my feet touching the floor or pressing against the arm rest.

I really cant remember if my back pressed against the seat at the back.

Through the window i could see that we were in a dive and could clearly detect (feel) the moment when we started to move in a straight line.

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#13

Re: Zero-G Flight

05/03/2007 1:21 PM

The diagram is correct. As a son of a KC-135 Boom Operator for 20+ years I may know something about the famous Vomit Comet an the parabolic vertical flight path. The way it works is on the up flight, the aircraft is at Positive G-force. On the downward flight the aircraft is at Negative G-force. The top hump is Zero G.

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Anonymous Poster
#17
In reply to #13

Re: Zero-G Flight

05/04/2007 10:41 AM

When you are going up the curve, the only value that matters is the Y axis component. Y has 1G when standing still or moving along X at variable speeds. As long as you fly at same altitude. Your body is pulled into the seat, in 1G, as the plane floats due to its speed and lift. But when the plane falls to the earth at a free fall, both your body and the plan are pulled down but since the plane is falling too, you body is trying to sit on a seat, but the seat is falling away from you with the same acceleration, so you never meet until the plan begins to pull up.

Another way you can think of it is to watch a motor cycle stunt person jump a ramp. Leave his bike in mid air and do some kind of body twist, and then return back to his bike. At the peak of his arc, he and his bike are both done traveling in the positive Y direction and both he and his bike begin to fall together. He cannot do the trick on the way UP the arc, cause his body weight appearst to be heavier as his bike goes UP, but as he approaches the top of the arc, his body weigth begins to drop, even before he reaches the top of the arc, and when his is at the top of the arc, his body weight is zero along with the bike. So getting back to the plane, as the people in the plan approach the arc from the left hand side, they slowly begin to feel lighter until they feel weightless relative to the plane, at the top of the arc. If the plane leveled off, everyone would feel their own weight again and be in their seats. But since the plane continues the arc, the weightless effect continues as both your body and the plane are falling together. The diagram is correct. Relative to a spectator on the ground watching the experiment. The plan or motor bike has no velocity in the Y direction at the top of the arc. Hence it must be floating, although instantaneous, before it begins to fall and pick up speed. But relative to each other both masses travel and accelerate at the same speed and same direction, and YES they are both feeling the effect of 1G again, but to relative to them selves, their plane the remain weightless. However, throughout the entire experiment, I assure you, that Gravity is still there. It does not go away. It is relative. Like Albert said.

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Anonymous Poster
#18

Re: Zero-G Flight

05/04/2007 11:36 AM

Using the previous automobile analogy, consider what happens when you drive your car up a 45 degree ramp at a high rate of speed. The car's vector is 45 degrees up, but the moment it leaves the ramp, both the car and the passenger begin a free fall accelleration. You will remain weightless until the vehicle recontacts the earth, though in this case with devestating results. The key point is that the passenger will begin to experience weightlessness the moment the vehicle leaves the end of the ramp, as both the vehicle and it's contents begin their freefall. In the case of the aircraft, using the upward vector of the flight path roughly doubles the time available for free fall as compared to simply nosing over from straight and level flight.

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