I think it might be time for the holy hand grenade.
I think it might be time for the holy hand grenade.
Andrew can take it. 'Tis but a scratch!.
Imagine if you will that scene rewritten with Andrew as the black knight.
I was wondering...
At what point is it nearly impossible to hold a rocket together made of paper, plastic, and wood? J? K? L?
I've been in the hobby since 1973. I grew up on Estes and Centuri. Back then it was all paper, plastic, and wood.
But the last few kits I bought were fiberglass, carbon fiber, and metal tipped nosecones. Some of these "indestructible" kits are even designed for short-thrust E, F, and G motors.
I was wondering...
At what point is it nearly impossible to hold a rocket together made of paper, plastic, and wood? J? K? L?
Why I'm asking...
I've seen too many over-engineered and under-executed, "indestructible" rockets plant themselves balls-deep into the ground. I have to think that if that same lawn-dart hit an RV, car, or person it wouldn't be pretty.
And I've been thinking...
Why use "deadly force" instead of "reasonable force"? Why use a gun when you could use a taser? Why use fiberglass instead of paper tubing? Why use a metal-tipped nosecone instead of a plastic cone?
Then again...
I have to admit that I have no data behind my thoughts. I mean, if you jump into water from a meter it's fun. If you jump into water from 18 stories up, it's deadly. Maybe a balsa nosecone with an "E" bounces off your car... but with a "K" it pierces the roof. I don't know.
What are your thoughts?
[video=youtube;M_FCQ550770]https://www.youtube.com/watch?v=M_FCQ550770[/video]
Let the flutter do the talking.
always dangerous after four pages of replies but going back to original post which has been partially answered
1. At what point is it nearly impossible to hold a rocket together made of paper, plastic, and wood? J? K? L?
Has nothing directly due to engine size. Has everything to do with rocket velocity, of which the factors include rocket size, rocket mass, rocket aerodynamics (drag coefficient), and not just motor size but also motor output and burn time. An improperly built rocket can shred on an A motor. A balsa finned Rocket can break Mach if built right (may need to paper fins.). At some point in fin size and rocket velocity wood fins without fiberglass become impractical, but not directly dependent on motor choice.
2. Why I'm asking...
I've seen too many over-engineered and under-executed, "indestructible" rockets plant themselves balls-deep into the ground. I have to think that if that same lawn-dart hit an RV, car, or person it wouldn't be pretty.
Major misconception here. No rocket under the safety code can nor should be engineered to survive a ballistic recovery. Not high power, not mid power, not low power. This is one reason high power qualification flights require the rocket after recovery to be re-fly-able.
3. And I've been thinking...
Why use "deadly force" instead of "reasonable force"? Why use a gun when you could use a taser? Why use fiberglass instead of paper tubing? Why use a metal-tipped nosecone instead of a plastic cone?
Fiberglassing is used for strength to handle higher velocities and for cosmetic reasons. Metal tipping of nose cones (and some fancy ablative materials on fins) is used to help rocket survive higher velocities. Neither fiberglass nor metal nose cones are used to help a rocket survive a bad landing, in fact one of the key points in model Rocketry is to AVOID bad landings.
4..Maybe a balsa nosecone with an "E" bounces off your car... but with a "K" it pierces the roof. I don't know.
Carelessness and stupidity in combination with model Rocketry is dangerous with any motor size. You can poke your eye out bending over a launch pad prepping a A4-3T motor rocket. As mentioned, a relatively recent death was caused by a non high power rocket. While the safety code forbids trying to catch a high power rocket on descent (kind of a Darwin Award IMO) otherwise the rules are fairly similar.
Model Rocketry remains safe because those who practice it (for the most part) continue to emphasize safety in all aspects of the hobby from MicroMaxx to 3/4 scale Mercury Redstone rockets.
Why I'm asking...
I've seen too many over-engineered and under-executed, "indestructible" rockets plant themselves balls-deep into the ground. I have to think that if that same lawn-dart hit an RV, car, or person it wouldn't be pretty.
Major misconception here. No rocket under the safety code can nor should be engineered to survive a ballistic recovery. Not high power, not mid power, not low power. This is one reason high power qualification flights require the rocket after recovery to be re-fly-able.
. . . Why use fiberglass instead of paper tubing? . . .
After getting a big zipper on the first flight of a cardboard rocket that I spent many weeks building and painting, I no longer build cardboard rockets.
E=MC^2.... the speed, not the weight, is the major component of the rockets "potential" to do serious damage.
Please don’t take this the wrong way, but you may be making the point for the original poster. By building using fiberglass you avoid the end result of opening a parachute at high speed (zippering) but you may not have figured out how to prevent the root problem, high speed deployments.
I'm a little late to this party, but I'm always particularly fascinated by the level of response loaded question threads such as the OP's receive.
E=MC^2.... the speed, not the weight, is the major component of the rockets "potential" to do serious damage.
Equally as intriguing is why hobby level rocket fliers are debating Einstein's field equations and relativity as they apply to the related field of the physics of a vehicle in flight when the more relevant equation F=ma by Newton, the guy whom without we would not have rocket science is not instead discussed by those (and those certified to presumably have a fundamental knowledge of his three laws as they apply to rocketry) seeking answers concerning the amount of destruction said vehicle has the potential to create?
You’re correct that the kinetic energy is proportional to the square of the velocity, but the equation for kinetic energy at any of the velocities we’ll ever achieve is e = 1/2 m * v^2.
Conservation of energy and conservation of momentum must both be considered when analyzing the potential for damage.
It was a dual deploy cardboard Der Red Max with altimeter apogee deployment and a Jolly Logic Chute Release. It zippered when the JLCR released.
I'm a retired M.E. / CWI, never implied I was a rocket scientist, and certification as such isn’t a pre-requisite on this forum.
And for the record.. we would still have "rocket science" even if Newton had never been born.
:eyeroll: Somebody's been watching to much CNNCWI? Товарищ!
Last edited by rhildinger; Today at 04:52 PM. Reason: snarky reply was unnecessary
I'm a little late to this party, but I'm always particularly fascinated by the level of response loaded question threads such as the OP's receive.
Equally as intriguing is why hobby level rocket fliers are debating Einstein's field equations and relativity as they apply to the related field of the physics of a vehicle in flight when the more relevant equation F=ma by Newton, the guy whom without we would not have rocket science is not instead discussed by those (and those certified to presumably have a fundamental knowledge of his three laws as they apply to rocketry) seeking answers concerning the amount of destruction said vehicle has the potential to create?
Probably because f=ma is no more relevant to this question than e=mc^2. Neither is the correct equation. F=ma tells you how fast your rocket will accelerate with given net force, it doesn't tell you how hard it will hit you on the head on the way down.
Actually it does. Your head causes the rocket to decelerate rather quickly.
Probably because f=ma is no more relevant to this question than e=mc^2. Neither is the correct equation. F=ma tells you how fast your rocket will accelerate with given net force, it doesn't tell you how hard it will hit you on the head on the way down.
I'm no mathematician, in fact, I'm math retarded, but I'm pretty sure if you want to solve for "a" then a=F/m. Isn't the "Force" of an impact is the solution to F=ma?
No. I think what you're getting at is momentum, which is mass * velocity. Momentum and kinetic energy are the two things that matter in a collision.
F = ma describes the force required to accelerate the specified mass.
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