2 Mass Scissors Helicopter for High Jerk Missile Evasion

A three mass helicopter could evade fire from all directions with out turning, maybe with a simpler linkage.
The first obvious constraints to the problem:
1. the center of lift needs to be above the center of mass at all times. This means each section will need it's own rotor. To avoid a lot of transmission shafts and U joints each rotor will need its own engine.
2. the linkage mechanism must be long enough to give missiles a wide berth. It must also be light weight so bending moments should be as low as possible. This probably means the center of lift from each rotor must be over the center of mass of each respective section.
3. the torque balance must be more or less controllable if they don't want to get dizzy from spinning. On the 3 body this means one large rotor and two smaller counter rotating rotors.
A 2 body craft might always be vulnerable in one direction. Even if it could spin 90 degrees fast enough it may have problems when receiving fire from several directions.
Unless there is some elegant solution to the 2 body linkage, the 3 body craft may be the way to go.
Bret Cahill
Reply to
Bret Cahill
Loading thread data ...
Dear Bret Cahill:
Three (or more) body systems are inherently chaotic in *this* Universe. You are fooling yourself.
David A. Smith
Reply to
dlzc
All you need to do is write out the equations of motion for each mass and the controller will do the rest.
Bret Cahill
Reply to
Bret Cahill
All you need to do is write out the equations of motion for each mass and the controller will do the rest.
Bret Cahill ======================================= All you need do is write out the exact value of pi and the controller's digital program will compute the equations of motion exactly. Analogue computers know the exact value of pi but the components have tolerances and are subject to noise. Until then you are stuck with chaos and are fooling yourself.
Reply to
Androcles
Andcorcles wrote: wherein | == JP said: I like to be crass and offend in retribution for | == JP said: a career of arse-kissing politeness in pursuit | == JP said: of the almighty buck, & where better than usenet?]
... ahahahaha....
Reply to
hanson
This could have been done on some basis 80 years ago.
Water craft would be a simpler problem because they stay at one "altitude" and don't have the lift requirements of a helicopter. One engine could handle a multi hull vessel.
Reply to
Bret Cahill
Same lock on radar technology they've been using for decades.
A controller can't update with corrections?
. . .
Same as you move anything with servos.
Bret Cahill
Reply to
Bret Cahill
But, the reason or that, is because the vast majority of aircraft are designed by military, and the only thing many of know them about aircraft at all is WWI radar. So the people who actually know how WWI trenches work have already buillt ICBMs. The people who know how WWI machine guns work have already built laser-guided bombs and supercomputers. The people who know how WWI radio works have built artificial satellites. The people who know how WWI tanks work have already built shoulder-fired AA and DU stockpiles.
Reply to
jim
Whether or not it's necessary the military is always hauling troops around in easy to hit targets.
That'll soon be 3-D if it isn't already. There's no good reason to be in harm's way.
Trick them into thinking they are at war yet not have any actual casualties on either side.
Bret Cahill
"You tell me it is the great cause that hallows even war. I tell you it is the great war that hallows any cause."
-- Nietzsche
Reply to
Bret Cahill
Dear Bret Cahill:
Not at the duration of a ground-fired missile, a couple of seconds away. Not even discernable to radar due to size, and not until it clears buildings and such.
Your concept *entirely* fails if the ordinance has correction capability. If you lose 1/2 or 1/3 the craft, you lose it all. Separate vehicles does not have that problem.
You apparently missed "multi-ton", and superstructure, and the everpresent "keeping an operator at the controls" when you accelerate masses at 10g or better.
David A. Smith
Reply to
dlzc
The goal here isn't to prevent the killing of troops point blank on or near the ground. That may never be possible to prevent.
The goal here is to keep the aircraft from getting hit when they are up in the air where everyone can see them and take aim.
The U. S. military spends a great deal of its time in low tech military [RPG-only] countries.
It's a farce of high tech to let low tech weaponry take out high tech aircraft.
Two single body aircraft are as just about as easy to shoot down as one.
A helicopter is limited to two - 3 sections because of size and practicality.
A vessel could be supported by dozens, hundreds or thousands of computer controlled in-water pontoons/hydro foil skis, each very nimble and light weight.
How fast are these torpedoes going?
Bret Cahill
Reply to
Bret Cahill
Dear Bret Cahill:
...
This is what stated this "explosion" of yours.
No difference, Bret. They don't fire at helicopters from tens of miles away. And if they did, and they did not die laughing at seeing a two-humped camel flying, then the rest of the craft hits the dirt too.
Ooh, the Pentagon is so embarrassed by your opinion. Bullets are low tech, and we still make them, and they still bring down aircraft. Grow up.
More than twice as hard as your brainfart. Because the second pilot will try to be elsewhere.
You started on ships here. See above. A helicopter is limited to one section, since your idea will not work on helicopters.
You know nothing of the Navy. The lightest they ever built was the PT boat, and haven't since then.
Faster than 240mph, in some cases. And capable of being dropped hours away, and home on the sound of a particular propellor, jump out of the water to avoid submarine nets (which it is capable of detecting), and repeat at need until that specific piece of hardware is struck. Including circling back.
David A. Smith
Reply to
dlzc
Using the 2 conventional [independent] helicopter test stand mentioned above, the linkages could be designed to passively snap or actively release if one side gets hit.
2 X 0 =3D 0.
That's why so many helicopters get shot down.
Unless the bird is soaring a duck hunter would have a more difficult target even if the goose was 20 m long.
. . .
Which takes forever because propulsion is low acceleration / low jerk.
Single body helicopters have no real evasive capability whatsoever.
. . .
That would be easy to disprove with 2 toy helicopters.
. . .
That doesn't mean they will always want to be easy targets.
If the sonar tracks the torpedo from just 1 km -- a very short distance considering the weapons are designed to go an order of magnitude further -- they still have 10 seconds to move the pontoons out of the path.
For a 1000 metric ton / 100 pontoon water craft where each pontoon weighs one ton, displaces 10 tons and draws 3 m, the diameter of the pontoon is about 2 meters so each pontoon in the path of the torpedo only needs to be moved 1 m to avoid being hit.
That's 0.002 g.
You were off by almost FOUR (4) orders of magnitude!
With forces that small they could use compressed air from a shop compressor and skinny air cylinders.
Multi or mili hull water craft should have been considered before now for another reason: Even if a torpedo blows up several of the pontoons it's not a big deal.
The high specific drag of the pontoon array could be eliminated during cruising either by retracting the pontoon array or by lowering its geometric compliment.
Bret Cahill
Reply to
Bret Cahill
If most fire tends to come in at less than a 45 degree angle with the ground as epidemological studies as well as anecdotal accounts may bear out, the two mass version should be double decker, one section above the other with both moving vertically in opposite directions. A linkage or pulley system accelerates each section up and down when avoiding fire.
The extension of a cable system could be several times the fuselage height adding very little weight to the system yet still move both bodies apart at accelerations up to 1 g / zero jerk and back together at higher accelerations / high jerk. Dodging mode defult position may need to be be 1/2 full extension so that if dropping the lower section isn't fast enough the two sections can be yanked back together.
"Yank" here is occasionally used to mean the first derivative of force and equals mass X the first derivative of accelleration, "jerk."
Another advantage with vertical movement is the analysis of the rotor stresses doesn't get messy as might be the case with a horizontal yanking movement. The new design would at worst, call for a strengthened rotor.
Bret Cahill
Reply to
Bret Cahill
That often happens when a poster is off by four orders of magnitude.
Three orders?
OK.
Four orders?
That's stepping over the line.
Reply to
Bret Cahill

Site Timeline

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.