Read the forum code of contact
By: - 29th December 2014 at 19:27 Permalink - Edited 1st January 1970 at 01:00
also can the missiles such as Sprint , THAAD attack aircraft ?
By: - 29th December 2014 at 20:16 Permalink - Edited 1st January 1970 at 01:00
are you asking a question or providing answers to a question NO ONE had asked?.....by the way, it is because a bullet or artillery shell is confined within an enclosed tube, the expansion of the gasses released in extremely short times by the combusting propellant locks the base of the projectile into the rifling or the sabot into the barrel wall....with this move the gases have no way to escape except to force the bullet or shell out the end of the TAPERED barrel...so as the projectile travels down the tapering to a smaller diameter of the barrel, it is further compressed increasing the velocity the round exits the barrel at.........now any bullet or shell suffers from a degradation of it;s velocity as the distance traveled increases, so it actually slows down and eventually drops to the ground...it's maximum velocity is found directly at the point of exit from the barrel...from there it declines......
A missile or rocket relies on the shear energy of the rocket or missile motor to push the munition through the atmosphere, as such there is a huge waste of available energy that is dissipated into the surrounding atmosphere , out to the sides etc that don;t correlate to the rocket / missile actually getting going any faster..ICBM type rockets / missiles also have to overcome the direct effects of it's own weight AND gravity on the launch of the munition, which also slows the process and reduces the acceleration....now Rockets / missiles however INCREASE in velocity as it's flight time increases, this is because the munition's THRUST is overcoming the physics ( weight, gravity, aerodynamics, drag, friction etc) that hamper it's launch initially......that increase however is governed directly by the availability of fuel being burned to produce the thrust...as soon as the fuel is depleted, the munition begins to slow.... .that is a pretty simplified explanation , but it covers the basics.....
Also...would this NOT have fit in the "MISSILES and MUNITIONS" sub thread better?......this has nothing to do with Military aviation does it?..
By: - 29th December 2014 at 20:30 Permalink - Edited 1st January 1970 at 01:00
are you asking a question or providing answers to a question NO ONE had asked?.....by the way, it is because a bullet or artillery shell is confined within an enclosed tube, the expansion of the gasses released in extremely short times by the combusting propellant locks the base of the projectile into the rifling or the sabot into the barrel wall....with this move the gases have no way to escape except to force the bullet or shell out the end of the TAPERED barrel...so as the projectile travels down the tapering to a smaller diameter of the barrel, it is further compressed increasing the velocity the round exits the barrel at.........now any bullet or shell suffers from a degradation of it;s velocity as the distance traveled increases, so it actually slows down and eventually drops to the ground...it's maximum velocity is found directly at the point of exit from the barrel...from there it declines......A missile or rocket relies on the shear energy of the rocket or missile motor to push the munition through the atmosphere, as such there is a huge waste of available energy that is dissipated into the surrounding atmosphere , out to the sides etc that don;t correlate to the rocket / missile actually getting going any faster..ICBM type rockets / missiles also have to overcome the direct effects of it's own weight AND gravity on the launch of the munition, which also slows the process and reduces the acceleration....now Rockets / missiles however INCREASE in velocity as it's flight time increases, this is because the munition's THRUST is overcoming the physics ( weight, gravity, aerodynamics, drag, friction etc) that hamper it's launch initially......that increase however is governed directly by the availability of fuel being burned to produce the thrust...as soon as the fuel is depleted, the munition begins to slow.... .that is a pretty simplified explanation , but it covers the basics.....
Also...would this NOT have fit in the "MISSILES and MUNITIONS" sub thread better?......this has nothing to do with Military aviation does it?..
i know that bullet and shell waste less energy compared to missile due to the barrels , however 190,000 G is so significantly bigger than 3 G thus i was thinking there may be another reason
and it doesn't really explained how thing like Ball get hit by a bat ( waste energy to environmenttoo ) can still have 12,740 times the acceleration due to gravity http://www.acs.psu.edu/drussell/bats/impulse.htm
By: - 30th December 2014 at 01:19 Permalink - Edited 1st January 1970 at 01:00
why artillery shells and bullet can accelerate so much faster than missile?
I have no solid information but if I were to make an educated guess, there are several reasons;
1-Aerodynamics and energy equations; as an object goes faster, it produces more drag. Higher the drag force, higher the % of propellant simply wasted heating up the airframe. Its much more efficient to accelerate slowly, conserve some fuel for where the atmosphere is thin, and keep accelerating there. Such missile will gain more KE/PE energy and will reach longer range. This is the prime reason longer ranged missiles -generally- have longer burn times, and relatively less acceleration. An artillery shell does not have such luxury, only way to throw an artillery shell further is to give it more kinetic energy right at the end of the muzzle; irrelevant if it is efficient or not. As the muzzle length is limited due to several reasons, high acceleration is a must.
2-Structural concerns; Speaking of ICBMs, it will never need to withstand severe G forces due to "ballistic" flight. If it were to withstand 3 times more Gs, its structure will need to be 3 times heavier. As explained above, accelerating quickly serve no purpose for range, so there are no gains either way. Same will apply to all missiles to a certain degree.
3-All missiles carry some kind of electronics equipment inside. While those CAN be made to with stand 10000+Gs, this would make them more expensive and heavy.
By: - 30th December 2014 at 06:27 Permalink - Edited 1st January 1970 at 01:00
Chamber pressures in guns can run as high as 75,000 psi and the chamber walls have to be stressed to withstand those pressures. Depending on the chamber diameter, this can result in chamber walls several inches thick. The weight of a thick-walled chamber is heavy too. Maximum velocity for a gun projectile is at the gun's muzzle. So ideally, all the propellant should be consumed within the length of the barrel to accelerate the projectile. Long barrels are also heavy.
The chamber pressure in a rocket motor is typically 3,000 psi. The lower chamber pressure allows the chamber walls to be thinner and weigh less, which is handy for a flying vehicle. Maximum velocity for a missile is when thrust = drag and is altitude dependent since drag is altitude dependent.
By: - 30th December 2014 at 06:55 Permalink - Edited 1st January 1970 at 01:00
IANAPOEOB but there is an intuitive relationship between size/mass and ability to withstand acceleration. Many insects and small animals can withstand g-forces that would kill a person. I doubt it's a coincidence that the highest acceleration listed amongst your examples is that of the smallest object, and lowest that of the largest.
By: - 30th December 2014 at 15:20 Permalink - Edited 1st January 1970 at 01:00
I have no solid information but if I were to make an educated guess, there are several reasons;1-Aerodynamics and energy equations; as an object goes faster, it produces more drag. Higher the drag force, higher the % of propellant simply wasted heating up the airframe. Its much more efficient to accelerate slowly, conserve some fuel for where the atmosphere is thin, and keep accelerating there. Such missile will gain more KE/PE energy and will reach longer range. This is the prime reason longer ranged missiles -generally- have longer burn times, and relatively less acceleration. An artillery shell does not have such luxury, only way to throw an artillery shell further is to give it more kinetic energy right at the end of the muzzle; irrelevant if it is efficient or not. As the muzzle length is limited due to several reasons, high acceleration is a must.
2-Structural concerns; Speaking of ICBMs, it will never need to withstand severe G forces due to "ballistic" flight. If it were to withstand 3 times more Gs, its structure will need to be 3 times heavier. As explained above, accelerating quickly serve no purpose for range, so there are no gains either way. Same will apply to all missiles to a certain degree.
3-All missiles carry some kind of electronics equipment inside. While those CAN be made to with stand 10000+Gs, this would make them more expensive and heavy.
seem reasonable, still, doesnt the missile will reach target sooner if it accelerate faster?
By: - 30th December 2014 at 15:29 Permalink - Edited 1st January 1970 at 01:00
Chamber pressures in guns can run as high as 75,000 psi and the chamber walls have to be stressed to withstand those pressures. Depending on the chamber diameter, this can result in chamber walls several inches thick. The weight of a thick-walled chamber is heavy too. Maximum velocity for a gun projectile is at the gun's muzzle. So ideally, all the propellant should be consumed within the length of the barrel to accelerate the projectile. Long barrels are also heavy.The chamber pressure in a rocket motor is typically 3,000 psi. The lower chamber pressure allows the chamber walls to be thinner and weigh less, which is handy for a flying vehicle. Maximum velocity for a missile is when thrust = drag and is altitude dependent since drag is altitude dependent.
oh i see, so that why, i have always wonder why space shuttle and ICBM look really slow right after launch despite their very high maximum speed while it always impossible for me to see a bullet or a shell comming out of barrel despite their slow speed, used to think that only because they are too small
oh by the way, does anyone know how fast Aim-120, aim-9 accelerate?
By: - 30th December 2014 at 16:14 Permalink - Edited 1st January 1970 at 01:00
IANAPOEOB?
Not seen that one before!
I Am Not A Physicist Or Engineer Or Bull****ter ?!
By: - 30th December 2014 at 17:36 Permalink - Edited 1st January 1970 at 01:00
Biologist. ;)
Posts: 2,014
By: mig-31bm - 29th December 2014 at 19:05
why artillery shells and bullet can accelerate so much faster than missile? they dont really have much more fuel , powder
Sprint missile have much higher acceleration rate compared to other SAM today , at 100 G
HIBEX missile have the highest acceleration rate of all missiles ever at 400 G
ICBM missiles and spacecraft can accelerate at 3G
whereas
artillery shell can accelerate at 15 500 G
9 × 19 Parabellum handgun bullet can accelerate at 190,000 G
http://en.wikipedia.org/wiki/Orders_of_magnitude_%28acceleration%29
bullet and shell are not anymore aerodynamic than missiles so what is the reason ?
also Pilobolus fungi can accelerate spores at 20,000 Gs
https://www.youtube.com/watch?v=TrKJAojmB1Y