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#21
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aircraft as weapons platform
On Sep 13, 8:00 am, Eunometic wrote:
On Sep 13, 1:55 am, "Ken S. Tucker" wrote: On Sep 11, 4:08 pm, WaltBJ wrote: I was attending the Air Defense Command's Interceptor Weapons School back in 1963 and one of our lectures was "Future Developments' by a team from Wright Pat Air Development Center. In the course of events the 'suits' mentioned chaff rockets - folding-fin 70mm rockets fired from a bomber that dispensed spaced bundles of chaff to mask the bomber and draw off radar-homing missiles. The 'suits' complained that they had tried firing them sideways out of a special turret mounted on a B29 but the rockets insisted on going straight ahead. We looked at each other incredulously and finally one of our group asked "Did you ever consider that there was a 300 mile an hour wind blowing past the rocket launch tube?" No, they hadn't . . . Yeah rockets are designed to point into the wind, that's why the fin's are at the back! Indeed, prior to development of the R4M "Orkan" (Hurricane) folding fin rocket (this was the grand daddy of all such rockets) German researches put a great deal of effort into pure spin stabilized rockets that could easily be fired from tubes and 'revolver' style magazines eg RZ65 and RZ73. Although they worked their dispersion was simply to great to make them particularly effective Air to Air or even Air to Ground weapon that could engage point targets and as a result the folding fin rocket was born. Admittedly the R4/M may just have also had the advantage of a more powerful rocket motor to give it speed. Having said that the pure spin stabilized rocket would surely be far superior and possible totally effective in lateral launches with enormous cross winds, which on a B-29 would approximate 150ms. Assuming a 100G acceleration to 500m/s over a 0.5s boost the bulk of the acceleration is within the cross wind and one would expect the rocket to expend most of its acceleration heading into the direction of flight. In the 500G case things would be only a little better but not that much. Fins will quickly orient the rocket in the direction of airflow. A flat plate has a Cd of about 1 so assuming a pair of fins on a 70mm rocket has a total area A of 10cm x 10cm (0.01sqm) the force in Newtons will be F = 0.5Cd x p x A v^2 where v = velocity in m/s and p = air density in kg/cubic meter. Assume 330mph or 150m/s later launch at about 5000ft where air density is about 1kg/cubic meter F = 0.5 x 1.0 x 1.0 x 0.01 x 150^2 = 112N or about 12Kg. A missile weighing a few kilograms will very quickly orient in the direction of flow. A 2 kg mass at the tail will accelerate at 112/2 = 56m/s more than at the nose. In 0.1 sec during the boost phase seconds it would move 27cm relative to the nose section of the rocket which is enough to orient it about 45 degrees. If the burn was 0.5 seconds it would more or less end up flying with the bomber. That's agreeable, however the initial correction could impart enough yaw - via inertial moment - into the missile to blast it into the cockpit! Bullets obviously don't change direction and they don't have fins. Only the relatively lighter weight of the tail would induce it to accelerate faster than the warhead nose section. Modern MEMS inertial guidence technology combined with finless thrust vectoring nozzles would make it easy to accurately launch and guide missiles from aircraft at almost any angle. Take a look at the guidence system of the MBT LAWhttp://en.wikipedia.org/wiki/MBT_LAWhttp://www.army-technology.com/projects/mbt_law/ We launched a small experimental rocket in a 20-30 knot stiff breeze and decided to point the launcher into the wind, that was a mistake. What we should have done is pointed with the wind, because it get's twisted at lift-off. We wrote up a "sim" to confirm that. I believe it is also known by bazooka launchers that the missile has to be fired 'with the wind' rather than against it to compensate. Interesting to know. Ken |
#22
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aircraft as weapons platform
"Ken S. Tucker" wrote in message ... On Sep 13, 8:00 am, Eunometic wrote: On Sep 13, 1:55 am, "Ken S. Tucker" wrote: I believe it is also known by bazooka launchers that the missile has to be fired 'with the wind' rather than against it to compensate. Interesting to know. Ken Unfortunately the enemy rarely checks the wind direction is in your favour before attacking. Keith |
#23
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aircraft as weapons platform
On Sep 13, 2:40 pm, "Keith Willshaw" wrote:
"Ken S. Tucker" wrote in ... On Sep 13, 8:00 am, Eunometic wrote: On Sep 13, 1:55 am, "Ken S. Tucker" wrote: I believe it is also known by bazooka launchers that the missile has to be fired 'with the wind' rather than against it to compensate. Interesting to know. Ken Unfortunately the enemy rarely checks the wind direction is in your favour before attacking. Keith The problem is like launching a rocket in a 300-400 knot cross wind. I watched Eastwood's "Firefox" and he was doing Mach-mucho and fired a missile backward. so I guess it's possible ;-). Ken |
#24
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aircraft as weapons platform
On Sep 14, 1:32*am, "Keith Willshaw" wrote:
"Eunometic" wrote in message ... On Sep 13, 1:55 am, "Ken S. Tucker" wrote: On Sep 11, 4:08 pm, WaltBJ wrote: Yeah rockets are designed to point into the wind, that's why the fin's are at the back! Indeed, *prior to development of the R4M "Orkan" (Hurricane) folding fin rocket (this was the grand daddy of all such rockets) The Le-Prieur rockets were used by British and French aircraft against Zeppelins in WW1. Keith The photograph of Le-Prieur rockets on Wikipedia shows that they were 'stick' rockets. Basically a long somewhat ungainly stabilizing stick attached in the manner of fire works rockets when they were legal and therefore not "Folding Fin" rockets. It was the folding fin (with a touch of spin stabilization) that gave these rockets exceptional accuracy (for a rocket) while also making them relatively easy to carry. (Low drag, compact). I believe they remain the only style of unguided air launched rocket in service. |
#25
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aircraft as weapons platform
In article ,
grasshopper wrote: Has any military experimented with vertically launching missiles from the back of an aircraft for 360 degree targets? Think missile sub concept...... In WWII the Germans launched rockets (or maybe cannon) pretty much straight up from interceptors. The fighter would "park" under a bomber, and then fire upwards. It was called Schrage Musik. |
#26
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aircraft as weapons platform
On Sat, 20 Sep 2008 19:46:42 -0700, Julian Gomez
wrote: In article , grasshopper wrote: Has any military experimented with vertically launching missiles from the back of an aircraft for 360 degree targets? Think missile sub concept...... In WWII the Germans launched rockets (or maybe cannon) pretty much straight up from interceptors. The fighter would "park" under a bomber, and then fire upwards. It was called Schrage Musik. Cannon, not rockets. http://en.wikipedia.org/wiki/Schrage_Musik Ron Wanttaja |
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