Ballistic Theory, Progress report...Suitable for 5yo Kids
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From: Henri Wilson on 10 Nov 2005 03:31 On Thu, 10 Nov 2005 04:46:05 +0000 (UTC), bz <bz+sp(a)ch100-5.chem.lsu.edu> wrote: >HW@..(Henri Wilson) wrote in >news:h8q4n1d7pqjrp45p9d45dpov1dt1d1nbef(a)4ax.com: > >> On Wed, 9 Nov 2005 14:00:07 +0000 (UTC), bz <bz+sp(a)ch100-5.chem.lsu.edu> >> wrote: >> >>>HW@..(Henri Wilson) wrote in >>>news:1ne3n11h53shhf6rrg39cfbikba5oik65p(a)4ax.com: >>> >> >>>>> >>>>>By the way, modern fighter planes are designed to be UNSTABLE in the >>>>>air. The pilot can NOT possibly fly them without the computer to >>>>>continually compensate for the instabilities. Modern aeroplanes are >>>>>FIRMLY based on theory and data. >>>> >>>> Don't think so Bob. >>>> >>>> >>> >>>so. >>> >>>[quote >>>http://www.centennialofflight.gov/essay/Evolution_of_Technology/Computers >>>/Tec h37.htm] >>>The General Dynamics (now Lockheed-Martin) F-16, which entered service >>>in the late 1970s and has been built in large numbers, was the first >>>operational jet fighter to use an analog flight control system. The >>>pilot steers the rudder pedals and joystick, but these are not directly >>>connected to the control surfaces such as the rudder and ailerons. >>>Instead, they are connected to a "fly-by-wire" flight control system. >>>Three computers on the aircraft constantly adjust the flight controls to >>>maintain the aircraft in flight and reply to the commands from the >>>pilot. The F-16 is inherently unstable by design, meaning that it would >>>fly out of control if the computers failed (which is why there are three >>>of them). The designers made it unstable in order to improve its >>>maneuverability. The computers constantly readjust the flight surfaces >>>to keep the plane flying. Initially, pilots often referred to the F-16 >>>as "the electric jet." But computer control systems have become so >>>common that they are no longer unusual. [unquote] >> >> I think that is probably a little out of context. >> I'm sure the planes would be stable in normal flight. > >As with some of the other things of which you are sure, you are wrong. > >> I think such a servo control system would only apply during fast >> maveuvering. > >Wrong. > >> ...but any remote electronic system must work on the principle of >> sensing and reducing an error. One of the big problems is to find a >> decent compromise between reaction time, senstivity and damping. One >> must prevent the thing from building up an oscillation. > >In this case, the system is designed, on purpose, to REQUIRE inhuman >capabilities in order to control the craft. > >Take a pencil, wrap 25 gms of solder around the eraser end of the pencil. > >Balence the pencil by the point on your finger. That is the way aircraft >used to be designed. > >Now, move the 25 gms of solder downward until it is just above the bottom >end of the pencil. There is now no way a human can react fast enough to >balance the pencil. A computer can, however. Oh well I wont argue. Maybe there are advantages in doing it this way... > >Todays fighter aircraft REQUIRE constant computer control. So does today's astronomy. I have a good program that might be of some use. HW. www.users.bigpond.com/hewn/index.htm see: www.users.bigpond.com/hewn/variablestars.exe "Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong".
From: bz on 10 Nov 2005 06:16 HW@..(Henri Wilson) wrote in news:5816n15omecnqanctu84jei5rgm60aofli(a)4ax.com: > On Thu, 10 Nov 2005 04:46:05 +0000 (UTC), bz > <bz+sp(a)ch100-5.chem.lsu.edu> wrote: > >>HW@..(Henri Wilson) wrote in >>news:h8q4n1d7pqjrp45p9d45dpov1dt1d1nbef(a)4ax.com: >> >>> On Wed, 9 Nov 2005 14:00:07 +0000 (UTC), bz >>> <bz+sp(a)ch100-5.chem.lsu.edu> wrote: >>> >>>>HW@..(Henri Wilson) wrote in >>>>news:1ne3n11h53shhf6rrg39cfbikba5oik65p(a)4ax.com: >>>> >>> >>>>>> >>>>>>By the way, modern fighter planes are designed to be UNSTABLE in the >>>>>>air. The pilot can NOT possibly fly them without the computer to >>>>>>continually compensate for the instabilities. Modern aeroplanes are >>>>>>FIRMLY based on theory and data. >>>>> >>>>> Don't think so Bob. >>>>> >>>>> >>>> >>>>so. >>>> >>>>[quote >>>>http://www.centennialofflight.gov/essay/Evolution_of_Technology/Compute >>>>rs /Tec h37.htm] >>>>The General Dynamics (now Lockheed-Martin) F-16, which entered service >>>>in the late 1970s and has been built in large numbers, was the first >>>>operational jet fighter to use an analog flight control system. The >>>>pilot steers the rudder pedals and joystick, but these are not >>>>directly connected to the control surfaces such as the rudder and >>>>ailerons. Instead, they are connected to a "fly-by-wire" flight >>>>control system. Three computers on the aircraft constantly adjust the >>>>flight controls to maintain the aircraft in flight and reply to the >>>>commands from the pilot. The F-16 is inherently unstable by design, >>>>meaning that it would fly out of control if the computers failed >>>>(which is why there are three of them). The designers made it unstable >>>>in order to improve its maneuverability. The computers constantly >>>>readjust the flight surfaces to keep the plane flying. Initially, >>>>pilots often referred to the F-16 as "the electric jet." But computer >>>>control systems have become so common that they are no longer unusual. >>>>[unquote] >>> >>> I think that is probably a little out of context. >>> I'm sure the planes would be stable in normal flight. >> >>As with some of the other things of which you are sure, you are wrong. >> >>> I think such a servo control system would only apply during fast >>> maveuvering. >> >>Wrong. >> >>> ...but any remote electronic system must work on the principle of >>> sensing and reducing an error. One of the big problems is to find a >>> decent compromise between reaction time, senstivity and damping. One >>> must prevent the thing from building up an oscillation. >> >>In this case, the system is designed, on purpose, to REQUIRE inhuman >>capabilities in order to control the craft. >> >>Take a pencil, wrap 25 gms of solder around the eraser end of the >>pencil. >> >>Balence the pencil by the point on your finger. That is the way aircraft >>used to be designed. >> >>Now, move the 25 gms of solder downward until it is just above the >>bottom end of the pencil. There is now no way a human can react fast >>enough to balance the pencil. A computer can, however. > > Oh well I wont argue. > Maybe there are advantages in doing it this way... > >> >>Todays fighter aircraft REQUIRE constant computer control. > > So does today's astronomy. Constant computer CONTROL? The computer is to the mind as the lever is to the muscles. One can use a lever to move a rock or to bash someone in the head. When properly used, a computer is very useful. > I have a good program that might be of some use. Everyone and everything is of some use. Some of us serve mankind by providing examples of what NOT to do. Your program(s) provide{s} some interesting pictures and allows one to explore what might be seen in a certain kind(s) of universe{s}. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. bz+sp(a)ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
From: Henri Wilson on 10 Nov 2005 15:31 On Wed, 9 Nov 2005 22:36:36 -0000, "George Dishman" <george(a)briar.demon.co.uk> wrote: > >"Henri Wilson" <HW@..> wrote in message >news:1ft4n1d2j2esvvn9th4gg4iiefpvvk9rv9(a)4ax.com... >> On 9 Nov 2005 13:25:38 -0800, "George Dishman" <george(a)briar.demon.co.uk> >> wrote: >>>> > >>>I thought we had agreed that several times before. Perhaps >>>> > >>>I wasn't clear so I'll go through it again in more detail. >>>> > >>>In Ritzian theory, the light is emitted at some speed greater >>>> > >>>than c from the source. The speed can be found by taking the >>>> > >>>magnitude of the vector sum of the mirror velocity and a >>>> > >>>vector of magnitude c whose direction is such that the light >>>> > >>>eventually reaches the detector. >>>> > > >>>> > >I agree what you say next, do you agree what I say above? >>>> >>>> Henri, can you confirm the above please, I didn't think it >>>> was contentious but you seem to be avoiding it. >>> >>>Can you say if you agree with my statement of the behaviour. > >So do you agree Henri? Consider this. You are driving along a road at v and your passenger wants to shoot a duck that is sitting on the ground 500 metres to your left. Where does he aim? Where does he aim if the duck appears at 45 degree forward? Where does he aim if the duck flies off at v and exactly 90 degrees away from the road ? ____________v<-car /gun | | | \/ v Duck HW. www.users.bigpond.com/hewn/index.htm see: www.users.bigpond.com/hewn/variablestars.exe "Sometimes I feel like a complete failure. The most useful thing I have ever done is prove Einstein wrong".
From: Black Knight on 10 Nov 2005 23:25 "Henri Wilson" <HW@..> wrote in message news:6ua7n15d9rn5rld9rco5lrfa752igqbdvs(a)4ax.com... > On Wed, 9 Nov 2005 22:36:36 -0000, "George Dishman" > <george(a)briar.demon.co.uk> > wrote: > >> >>"Henri Wilson" <HW@..> wrote in message >>news:1ft4n1d2j2esvvn9th4gg4iiefpvvk9rv9(a)4ax.com... >>> On 9 Nov 2005 13:25:38 -0800, "George Dishman" >>> <george(a)briar.demon.co.uk> >>> wrote: > >>>>> > >>>I thought we had agreed that several times before. Perhaps >>>>> > >>>I wasn't clear so I'll go through it again in more detail. >>>>> > >>>In Ritzian theory, the light is emitted at some speed greater >>>>> > >>>than c from the source. The speed can be found by taking the >>>>> > >>>magnitude of the vector sum of the mirror velocity and a >>>>> > >>>vector of magnitude c whose direction is such that the light >>>>> > >>>eventually reaches the detector. >>>>> > > >>>>> > >I agree what you say next, do you agree what I say above? >>>>> >>>>> Henri, can you confirm the above please, I didn't think it >>>>> was contentious but you seem to be avoiding it. >>>> >>>>Can you say if you agree with my statement of the behaviour. >> >>So do you agree Henri? > > Consider this. > > You are driving along a road at v and your passenger wants to shoot a duck > that > is sitting on the ground 500 metres to your left. Where does he aim? > Where does he aim if the duck appears at 45 degree forward? > > Where does he aim if the duck flies off at v and exactly 90 degrees away > from > the road ? > > ____________v<-car > /gun > > > > > > | > | > | > \/ v > Duck > > > HW. Message rating several casks. Androcles.
From: Paul B. Andersen on 11 Nov 2005 04:49
Henri Wilson wrote: > On Wed, 09 Nov 2005 23:50:03 +0100, "Paul B. Andersen" > <paul.b.andersen(a)deletethishia.no> wrote: > > >>Henri Wilson wrote: >> >>>On Wed, 9 Nov 2005 14:00:07 +0000 (UTC), bz <bz+sp(a)ch100-5.chem.lsu.edu> wrote: >>> >>> > > >>>>[quote >>>>http://www.centennialofflight.gov/essay/Evolution_of_Technology/Computers/Tec >>>>h37.htm] >>>>The General Dynamics (now Lockheed-Martin) F-16, which entered service in the >>>>late 1970s and has been built in large numbers, was the first operational jet >>>>fighter to use an analog flight control system. The pilot steers the rudder >>>>pedals and joystick, but these are not directly connected to the control >>>>surfaces such as the rudder and ailerons. Instead, they are connected to a >>>>"fly-by-wire" flight control system. Three computers on the aircraft >>>>constantly adjust the flight controls to maintain the aircraft in flight and >>>>reply to the commands from the pilot. The F-16 is inherently unstable by >>>>design, meaning that it would fly out of control if the computers failed >>>>(which is why there are three of them). The designers made it unstable in >>>>order to improve its maneuverability. The computers constantly readjust the >>>>flight surfaces to keep the plane flying. Initially, pilots often referred to >>>>the F-16 as "the electric jet." But computer control systems have become so >>>>common that they are no longer unusual. >>>>[unquote] >>> >>> >>>I think that is probably a little out of context. >>>I'm sure the planes would be stable in normal flight. >> >>But then you are very wrong. > > >>http://www.f16falcon.com/facts/f16_5.html >>" The F-16A/B employed an all-electronic fly-by-wire (FBW) >> flight control system instead of the traditional hydromechanical >> systems with linkages and cables. The system is a four-channel >> analog system, the F-16A/B having been designed too early to >> accommodate the quadruplexed digital system that was provided >> on the Space Shuttle and on the F/A-18 Hornet. The FBW system >> makes it possible for the F-16 to fly safely with its center >> of gravity behind the center of pressure, thus providing >> the aircraft with an inherent instability that makes it highly >> responsive to the controls and to use relatively modest amounts >> of tail deflection during high-g maneuvers. The use of relaxed >> stability enabled a smaller tail to be used, since less force >> was needed to alter aircraft attitude. The General Dynamics >> team was the first to take the bold step of eliminating mechanical >> backups to the FBW system, trusting the aircraft completely >> to electronics. >> >> Experience with a triplex digital system on the AFTI/F-16 gave GD >> the confidence to abandon the proven analog FBW system of the earlier >> Fighting Falcon and adopt the quadruplex digital FBW system for >> the Block 25 and beyond F-16C/D." > > > All right, I'll partly believe you. > I just hope I never have to fly in one. > > >>It is a long time since fighters were stable. >>They cannot be flown without a computer. >>Not even close. >>With traditional control, a man would simply not be fast enough >>to keep control of the plane. > > > Yes that is pretty obvious. Is it? I am not convinced you have grasped the point. A traditional aircraft - say like a small Cessna - is stable. That means that if the pilot leaves the aircraft to itself, it will keep going straight ahead (provided that trim tabs etc. are set properly). That means that if the plane by some reason veers a little around one of its axes, it will automatically correct itself. A non R/C model aircraft flies itself. It can do that because it is inherently stable. Real aircrafts are traditionally built after the same principles. But modern fighters are inherently unstable. That means that if it veers a little around one of its axes, forces will be induced which make it veer more in the same direction, unless it is corrected - fast! It could be compared to driving with a trailer. While driving forward the trailer will automatically follow the car. It is a stable system. But backing is another story. If the trailer has a small angle to the car, this angle will increase unless the driver corrects it. It is impossible to back along a given curve without continuous corrections on the steering wheel. It is an unstable system. A modern fighter is like that. It can't go straight ahead without continuous corrections. A man is fast enough to back with a trailer - if he drives slowly. But try to back at 100 km/h (60 mph)! It can't be done. But a computer could. >>And it probably isn't possible even if he were. >>The control panels don't move as you would expect them to. >>For example, the right and left elevator may move in opposite >>direction. And the ailerons may move in the same direction. >>And then there are those two extra control panels underneath >>the plane. >> >> >>>I think such a servo control system would only apply during fast maveuvering. >> >>It's much more than a servo control. >>The pilot tells the plane what he want it to do, and the computer >>figure out how to do it. For example, if you pull the stick hard, >>it means up as fast as possible. The plane will then pull up as >>fast as it can without structural damage. (The pilot may pass out, >>but the plane will stay in one piece.) > > > The pilot still has to think fast enough to make the plane do what he wants. Obviously. :-) > The electronics just carries out his instructions. No, it does much more than that. Even with no input from the pilot, it must continuously correct for the plane's tendency to veer off course. It is so bad that if it didn't, the plane would after a short time go into spin. >>>...but any remote electronic system must work on the principle of sensing and >>>reducing an error. One of the big problems is to find a decent compromise >>>between reaction time, senstivity and damping. One must prevent the thing from >>>building up an oscillation. >> >>It's very different from traditional servo loops. > > > Well its a bit like electronic power steering of a car(which hasn't been > introduced yet) but the basic problems remain. "A bit like" maybe, but just a very small bit. :-) It is a multi variable control system. That means that a number of inputs (rotations around and accelerations along the different axes) affects a number of outputs (the angle of the different control panels). It can not be divided into a number of one input - one output control loops. It's a beast of a control system. Which (- to a Norwegian's malicious pleasure -) was demonstrated by the Swedish JAS fighter. It crashed twice because the control system didn't work properly. http://www.nearlygood.com/video/crashlanding.html The pilot survived - and crashed a second time at an air show! He ejected, and survived again. He is probably getting used to it! :-) Paul |