How Missile ballast stability works?

1. Apr 26, 2017

Zahid

launching a missile from the water, how the ballast stability works?

2. Apr 26, 2017

Mech_Engineer

Have you considered trying a simple internet search for "ship ballast stabilization"?

3. Apr 26, 2017

Zahid

yes, i m working on that, but i feel like ship have big ballast system compare to missile which is 1m diameter, also i would need some exact work on, missile stability

4. Apr 26, 2017

Staff: Mentor

Welcome to the PF.

Your question does not make sense as you have asked it. Could you please provide a lot more detail and some sketches of what you are asking?

Missiles do not carry ballast. And ships that launch missiles would generally not need to do anything with their ballast when launching missiles, since the reaction forces involved in the launch are a tiny fraction of the weight of the ship.

https://s-media-cache-ak0.pinimg.com/originals/59/d9/29/59d9293c7f45df8e0c5a0951f2f8d0cb.jpg

5. Apr 26, 2017

Zahid

yes, you are right but what i m working on is totally different thing, have you heard about sea dragon or seabee or if you could visit to www.rippleaerospace.com
here you will see the missile launch. what i want to work is on the Missile control system and ballast stability

thank you very much.

Last edited: Apr 26, 2017
6. Apr 26, 2017

Staff: Mentor

Are you designing a weapon to attack the USA?

The reference you provided says that the missile is underwater only 2 seconds after launch.

Inertia will be an important factor, perhaps the dominant factor. You need a dynamic model, including the spatial distribution of buoyancy, and including the hydrodynamics of the water passing over the outside shell at a pretty good speed. That is not simple. The data you need from real missiles is probably classified.

Do you have access to the missile data and dynamic computer models?

7. Apr 26, 2017

Zahid

Haha, No access to any data. just working on a university project.

8. Apr 26, 2017

Staff: Mentor

I only read a little at the link. Why do they use that technique to launch the missile? It seems like it would be much easier to just launch it from a small boat that is towed by the ship. What advantage is there to having it in the water held upright by a ballast before launch?

9. Apr 26, 2017

Staff: Mentor

That's a question for a sailor.

For many consecutive days, seas can be too rough to have a rocket free standing vertically without toppling and /or spoiling the launch angle.

If you bolt it to the deck, it could capsize the boat because the c.g. is too high.

10. Apr 26, 2017

Staff: Mentor

If you have no data, then make a computer model and run a range of cases covering a range of assumptions about ballast distribution.

With only 2 seconds underwater, even an unstable ballast distribution may not tip enough to ruin the launch. It takes time to tip.

11. Apr 27, 2017

Zahid

its not important that i have to do all what is in that website, but that is just an example.

12. Apr 27, 2017

Zahid

my focus area is Dynamics of Missile ballast`, not the whole System.

13. Apr 29, 2017

JBA

It appears that they intend for the rocket to be buoyant for towing to the launch site and if it is to be towed then the longitudinal buoyancy cg must be in the center of the rocket length so they require a ballast to hold it vertical for launch.

At the same time I have rarely seen so much technobabble to promote a concept that is not very different from the method used for launching rockets and ICBM's from submarines, where the rockets are ejected vertically from the submarines before firing.

14. May 27, 2017

Zahid

can any body help me? im in critical condition

15. May 27, 2017

Staff: Mentor

16. May 27, 2017

Staff: Mentor

17. May 28, 2017

Zahid

the rocket is layed in th water, we fill the ballast with water to upheld(stand) the rocket.
Rocket Specifications:
Length: 7m
Weight: 602 kg
Diameter: 0.52 m
the length of the ballast is 2m
the rocket is two stage rocket.
the Ballast have 5 chambers for water to fill in.
how much water is need in the ballast to make the rocket stand?
what is rocket stability calculations during standing and launch?
how much pressure is released during the launch?
and other specification related to the dynamics of the ballast system
thank you in advance, any body can give detail.

18. May 28, 2017

Staff: Mentor

You don't expect us to do the whole project for you, do you?

Please show us what calculations you have done so far.

19. May 28, 2017

Zahid

i have completed the theory part
now need to work on the calculations, also did design and simulations.
but not yet how to calculate the stability in the water, the behaviour of the surounding(wind and water wave) during tilting an standing( the angle of heel).

20. May 28, 2017

Staff: Mentor

Show us your work or this schoolwork project thread or it will be closed. Do the work please and show us.

Last edited: May 30, 2017