On this slide we compare and contrast real rockets and model rockets. A model rocket is subjected to four forces during flight ; weight, thrust, and lift and drag. The same forces operate on a full scale rocket as it moves through the atmosphere. The flight trajectory of a full scale rocket takes it out of the atmosphere as quickly as possible. Therefore, the aerodynamic lift and drag are less important for a full scale rocket relative to a model rocket.
The magnitude of the aerodynamic forces depend on the air density and air density decreases to near zero at the edge of the atmosphere. For model rockets, the entire flight is conducted in the lower atmosphere and the aerodynamic effects are very important. During powered flight both model rockets and full scale rockets use a rocket propulsion system. Model rockets employ a variety of small solid rocket engines. There are some larger "amateur" rockets which use liquid or hybrid engines, but these are intended for older, more experienced rocket builders and are not discussed at this site.
Full scale rockets may employ either solid or liquid rocket engines. The purpose of the launch rod is to guide the rocket until it reaches sufficient speed where the fins take over and keep the rocket moving in a straight path.
This is approximately 30 miles per hour. By the way, the reason the Space Shuttle, and other large rockets don't have launch rods is because they have rocket engines that are steerable.
In other words, the direction the rocket engine pushes controls the path of the rocket. Our model rockets have a fixed nozzle. They will only move in one direction. So we need a rod to keep the rocket moving in the "upward" direction. Without a rod, the model can easily tip over at lift-off, and come screaming right at you.
So for safety, we have a launch rod that keeps the rocket pointed up. The actual device that starts the motor burning is the "starter. These wires are hooked up to the launch controller that we discussed earlier. When the electrical current passes through the starter, it heats it up and causes it to burst into flame. This flame is what actually starts the propellant burning in the rocket motor.
How do you hook them up? It's pretty simple. Check them out! Once the motor ignites, it begins to generate thrust. It is this thrust force that pushes the rocket into the air.
While the motor is making thrust, you'll normally see a flame coming out the back of the motor. Sometime it is hard to see because the rocket moves so fast. At the same time, the rocket motor is making a loud roar and a lot of thick dark smoke.
The propellant inside the motor burns quickly. In most motors, the propellant is consumed in less than three seconds, at which point "burnout" occurs.
This means the motor is no longer producing a thrust force. By the time the motor burns out, the rocket has already reached its top speed. It cannot go any faster from this point on. Most people are surprised that burnout occurs at a very low altitude.
While the rocket may reach hundreds or thousands of feet in the air, the burnout location on most rockets is about feet in the air. If you want to predict when the burnout occurs during the flight, you can do this with the RockSim software. When the motor burns out, the rocket may be traveling hundreds of miles per hour. We don't want the parachute to come out of the model while it is going this fast. Otherwise, it will be ripped to shreds. We want the model to coast upward and bleed off some speed.
The period of time that starts at engine burnout, and ends when the parachute is ejected out of the rocket is called the "Coast Phase. Even though the rocket motor isn't making thrust, there is something happening inside of it. The special composition called the delay element or delay grain is burning at a slow rate. See how model rockets work! It is obvious that something is going on, because there is still smoke coming out of the rocket motor.
Maybe this is what causes confusion among new modelers that they think the motor keeps burning all the way until it reaches apogee the highest point in the flight. The smoke serves a purpose though. It allows us to track the rocket -- in other words, to follow its progress into the air. Sometimes the rocket moves so fast, that it is hard to follow with our eyes. So the smoke gives us a visual indication where the model is.
There is something worth mentioning. The smoke produced by the delay grain is not as dark or as thick as the smoke produced by the motor while it is producing thrust. The delay smoke is whiter, and wispy. When the delay composition is done burning, it starts the "ejection charge" that is also built into the motor.
This ejection charge burns quickly, and is directed inside the rocket. It's goal is to push off the nose cone, and eject the parachute out of the rocket. Typically, we desire the ejection to occur right at apogee the highest point in the trajectory of the rocket.
It is at this point the rocket has slowed down to its minimum velocity. Here is what a motor can do with extra fuel. Some model rockets made out of paper and plastic can break the sound barrier and create a sonic boom.
Of course, that sonic boom is hard to hear as the rock is already likely to be over feet in the air and the boom is relatively small. It is still an amazing feat. In order to break the sound barrier and create a sonic boom, a rocket must be traveling at over miles per hour.
The motors used to do this are also restricted to those 18 years of age and older. But how do they manage it? The Apogee Aspire link to read reviews and check pricing on Amazon can fly over a mile high using and F motor, and it can break the sound barrier when using a G motor. It accomplishes this feat by being incredibly lightweight.
The rocket is 29 inches long and it only weighs 1. All the components of the rocket are extremely lightweight. The body it made out of thin paper tubes, the nose is thin plastic and the fins are made out of super light balsa wood. According to altitude predictions generated using a simulator called RockSim, when paired with the Estes E , the Apogee Aspire can reach an altitude of 2, feet in somewhere around 10 seconds estimated from the burn time plus delay time.
This is about feet per second or miles per hour on average. With a stronger motor like the Apogee F, the Apogee Aspire reached a height of 5, feet in about 16 seconds in the simulator. This is an approximate average of feet per second or mph. With an even stronger motor like the Aerotech 29mm G78G, the Apogee Aspire reached a height of 4, feet in about 11 seconds.
This is approximately feet per second or miles per hour. The slower motor actually resulted in a higher altitude, while the faster motor had a faster burn time and so could not go as high. Now none of these numbers show that the rocket broke the sound barrier, but these are a just estimates of the speed based on the information I have and b only reflect the average speed, not the top speed.
However Apogee does report that with a G motor the rocket will in fact cross the miles per hour mark to break the sound barrier albeit momentarily. In addition, because the delay usually activates the recovery after the rocket has stopped gaining altitude, these speeds are probably a little slower than they should be.
You can ditch the stock controllers and confidently build your own from scratch using our step-by-step instructions and exact materials list! Hi, I'm Charlie. I've been enjoying model rocketry since I was a kid. I am an avid enthusiast of aviation and space exploration, and I firmly believe model rocketry is one of the few hobbies that bridges the gap of being educational, engaging, and creative.
I hope to further attention and access to this fun hobby in some small way! We buy and assemble model rockets to launch them time and again, but is each component of the rocket itself built for this?
Are model rockets reusable? Most model rocket components are reusable Any time you see a model rocket launch, you'll usually see a launch pad, and any serious model rocket enthusiast wouldn't dream of launching without one.
So, what is the use of a launch pad Are you still using the standard Estes controllers for your launches? How Thrust Affects Speed Thrust is the force which moves a rocket through the air.
Here is a chart that shows the total impulse for different model rocket motors. Average Thrust The number that follows the letter in the code refers to the average thrust of the motor.
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