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New poll regarding ARCA stabilization method

Posted by: Bogdan - Tue Sep 29, 2009 11:01 am
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New poll regarding ARCA stabilization method 

What is your opinion about Popescu - Diaconu stabilization method?
It will work 29%  29%  [ 10 ]
There is a stabilization torque but it cannot be used for real rockets 3%  3%  [ 1 ]
It will fail since it's nothing more then the pendulum rocket fallacy 35%  35%  [ 12 ]
It will fail for other reasons 21%  21%  [ 7 ]
Don't know 12%  12%  [ 4 ]
Total votes : 34

New poll regarding ARCA stabilization method 
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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 11:42 am
Monroe wrote:
Ever tie a string to a cats tail with a piece of paper tied to it?

Monroe


Did the cat have ever had a constant accelerated move?

Paul.


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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 1:18 pm
As a matter of fact, yes for about 40ft down the hall. When he discovered he was attached :) snakes and snails and kitty cat tails I guess :) Sorry y'all I couldn't resist.

Monroe

Good Luck, ARCA and congratulations on getting support from your countrymen.
Godspeed

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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 3:46 pm
ARCA is buying time. The team has no intention to launch HELEN rocket which is nothing more than an untested improvisation (see the link).
Even if the weather is good at the end of the week they will invoke something else, a strong reason not to launch, or if their sponsors make so much pressure that they are oblige to launch, ARCA will report a partial success like:
"The balloon worked perfectly climbing to 8000 m instead of 14 000 m and the rocket fell due to a human error, because one suspension cord had not been properly secured"

See also the posts at the bottom of the page from this address:
viewtopic.php?f=45&t=8831&start=30


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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 7:06 pm
Polybaci wrote:
Hi,
...
G2 = force of gravity for the next stages
d2 = distance from the CG and next stages anchor point

It results the longitudinal(y) and the transversal(x) components of the forces which affect the AS rotation.
Fy - G2y is on the CG direction(in void no rotation from that)
Fx it's due to not a perfect alignment of trust to CG

So the rotation of the AS is affected by Fx and G2x using d1 and d2 lever.
At equilibrium:
Fx*d1 = G2x*d2

Fx is constant and G2x will increase with the angle dragging back the AS to the vertical.

For the dynamic analysis I can say that the inertia of the next stages and payload will drag the cord more close to the longitudinal axis of AS. So the (G2x + inertia x component) will decrease but it always be there.
...

In a free fall the gravitational value of G2 will be 0. It is true that the trailing object will have a gravitational force on it equal to F = ma, where"m" is the mass of the object and "a" is the gravitational acceleration. The first stage will also have the same gravitational acceleration, so there will be no net force between the two objects.

If the motor is providing thrust there will be an additional force applied to the second mass through the tether. Depending on how the tether is attached to the rocket this may cause the two objects to align with each other. However, there are no forces that would tend to align them with the gravitational field.

Dave


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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 8:39 pm
DaveHein wrote:
In a free fall the gravitational value of G2 will be 0. It is true that the trailing object will have a gravitational force on it equal to F = ma, where"m" is the mass of the object and "a" is the gravitational acceleration. The first stage will also have the same gravitational acceleration, so there will be no net force between the two objects.

If the motor is providing thrust there will be an additional force applied to the second mass through the tether. Depending on how the tether is attached to the rocket this may cause the two objects to align with each other. However, there are no forces that would tend to align them with the gravitational field.

Dave


You're right. I misjudged that. This is my error.
So all that remain in this setup to control the direction of the first stage is the inertial force of the next stages/payload masses along the tether. This will need a more complex analysis or the experiment itself. I just hope to see it soon.

Thanks!


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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 9:41 pm
I've noticed that there are 4 spokes at the end of the first stage. I think they will be the attaching points of the tether. This make sense if you try to maximize the effect of the force along the tether; you attache it as far as you can from the center of gravity.


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Post Re: New poll regarding ARCA stabilization method   Posted on: Mon Nov 09, 2009 10:10 pm
Polybaci wrote:
I've noticed that there are 4 spokes at the end of the first stage. I think they will be the attaching points of the tether. This make sense if you try to maximize the effect of the force along the tether; you attache it as far as you can from the center of gravity.

A cable is attached to each of the spokes, and they join together at some point between the first stage and the second stage. I believe a single cable is then connected to the nose of the second stage. ARCA's theory is that the tension on the four cables will tend to steer the rocket. Actually, if the cables do not stretch the first stage should just point straight away from the second stage. If the thrust from the first stage is slightly off center there will be no forces to counter the offset thrust. The first stage will just spin around the trailing stages.

Dave


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Post Re: New poll regarding ARCA stabilization method   Posted on: Thu Nov 12, 2009 7:37 pm
From Facebook

ARCA team and Navy Ship 281 Constanta crew are ready for departure. Tomorrow, ARCA will launch the Helen rocket, first Romanian space vehicle

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Post Re: New poll regarding ARCA stabilization method   Posted on: Thu Nov 12, 2009 8:15 pm
Just got the Press Release:

ARCA ready to launch Helen rocket, first romanian space vehicle

ARCA will launch Helen rocket, first Romanian space vehicle.
The launch will take place on the Black Sea shore, with the Navy’s support. The test flight will begin around 10 a.m. Launch procedures will last around three hours.
Article Continued...

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Post Re: New poll regarding ARCA stabilization method   Posted on: Fri Nov 13, 2009 9:48 am
Launch postponed to 14th.
Due to atmospheric conditions.


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Post Re: New poll regarding ARCA stabilization method   Posted on: Fri Nov 13, 2009 10:48 pm
Good, I can watch it live now then :)

One day to go and according to the Poll results over 50% of the Fellowship believe it will fail.... we near the moment of truth! :)

Exciting times! :)

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