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Surviving the transonic barrier.

 
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  #1  
Old 01-30-2010, 04:09 AM
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Surviving the transonic barrier.


Everyone knows what it takes to make a good long range bullet. Its got to be long and sleek. With low air resistance.

Now that's fine but these long skinny things seem to go nuts when they hit the sound barrier.

So my question is :- What attributes are needed to help make a bullet survive the transonic barrier while maintaining an acceptable level of accuracy.
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Old 01-30-2010, 09:16 AM
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Re: Surviving the transonic barrier.

Quote:
Originally Posted by Topshot View Post
Everyone knows what it takes to make a good long range bullet. Its got to be long and sleek. With low air resistance.

Now that's fine but these long skinny things seem to go nuts when they hit the sound barrier.

So my question is :- What attributes are needed to help make a bullet survive the transonic barrier while maintaining an acceptable level of accuracy.
I am not an expert in this area but I think it is shape and weight. (The more weight the
less effect as long as the BCs are good for that weight).

All Bullets pass through the Transonic barrier and the heaver they are the less they seem
to be effected by it.

J E CUSTOM
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Old 01-30-2010, 10:47 AM
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Re: Surviving the transonic barrier.

one of the problems is that air pressure builds behind the bullet during supersonic flight. when the bullet transitions from super to subsonic the air pressure from behind the bullet is released and causes the bullet to loose stability.
there is no shock wave when transitioning from super to sub as there is in super sonic flight
for a bullet to survive the transition it needs to have a shape that no air pressure can build behind of or of a shape that could handle the sudden high pressure release of air.......kindof like a football
next problem how do you get a football shaped bullet to shoot well out of a gun?
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Old 01-30-2010, 12:31 PM
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Re: Surviving the transonic barrier.

It's more dynamic stability(Sd) than gyroscopic(Sg).
Sg climbs downrange, whereas Sd can decay.
I don't know that it can be predicted..

It may very well be how the BC was reached. For instance if shape was used over weight, there might be dynamic stability issues not observed if weight were used over shape. There are bullets marketed that are known to have dynamic stability issues(like the 168 SMK's), but perform well for intended use/ranges.
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Old 01-30-2010, 03:18 PM
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Re: Surviving the transonic barrier.

There's a good discussion in the similar threads section at the bottom of the page....

When the bullet goes transonic/subsonic

MY thoughts..... if you go with a round ball your stability problems will be over
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Old 01-30-2010, 03:29 PM
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Re: Surviving the transonic barrier.

In addition to things already mentioned, I believe the ratio of the weight FORWARD also helps.........Rich
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Old 01-30-2010, 05:37 PM
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Re: Surviving the transonic barrier.

nah its all about aerodynamics, back in the early days when aircraft were just beginning to push into the realms of supersonic flight, they found all sorts of problems crossing the sound barrier, particlarly with regard to the complete loss of pitch control- the control surfaces (elevators) no longer had any effect on the attitude of the aircraft during this transonic speed and above.

The problem was in the design of the control surfaces. Previously, the control surfaces (the part that moves) were on the trailing edge of the tailplane and worked fine up to the speed of sound. They found that when flying at supersonic speeds, these control surfaces became buffeted in the shockwave of the aircraft fuselage, wings, and tail etc and were stalled in this turbulent airflow to the aft of the aircraft so therefore no longer were effective. To solve the issue, they changed the design of the tail, and all supersonic aircraft share this design today.... The entire horizontal stabiliser now moves instead of just a strip at trailing edge. Problem solved.

So i believe the stability of a transonic bullet has to do with aerodynamics and therefore the shape of the bullet.
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