Grade 6-8 | 10 (45 min) Classes
There had been strange lights in the sky before 1947, but never like this. In June of that year, an experienced civilian pilot reported “saucer-like discs” over Mount Rainier. By July, the papers were running stories about a rancher who discovered strange wreckage in the desert near Roswell. Accounts of mystery “aircraft” and other unknown aerial phenomena were gaining public attention. Something strange was going on and the people in charge wanted answers.
In 1949, a clandestine group of government scientists met at a secret airbase in Nevada to form Project Star Hopper. The goal was to produce a fast and maneuverable piloted vehicle to compete with the unidentified objects commonly referred to as “flying saucers.” With the nation’s best engineers on the task, plans were drawn up for a sleek and functional atomic-powered vessel that could be launched quickly to intercept the aggressors. The result was the Star Hopper – the world’s first interplanetary spacecraft. A small fleet was constructed and tested, and by 1955, they were ready to protect the skies from alien invaders. Or so we were told…
It was absolutely crucial that the Star Hoppers were able to land accurately on the stars if they were to be successful in identifying the aliens. The engineers at Project Star Hopper need your help to determine how to make the rocket land accurately for the pilots navigating space. The focus of your research will be on the recovery system and adjusting the length of the streamer
Targeted Performance Expectation(s):
Next Generation Science Standards (NGSS)
Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
Common Core Standards - Math
Solve problems involving measurement and conversion of measurements.
CCSS.MATH.CONTENT.4.MD.B.4 and CCSS.MATH.CONTENT.5.MD.B.2
Represent and interpret data.
Convert like measurement units within a given measurement system.
The aerodynamic force that opposes an aircraft’s motion through the air.
A push or pull upon an object resulting from the object’s interaction with another object.
Force that pulls everything down toward the center of the Earth.
The force that directly opposes the weight of an aircraft and holds an aircraft in the air.
A device incorporated into a model rocket for the purpose of returning it to the ground in a safe manner. All model rockets must employ a recovery system (such as a parachute).
A type of recovery system composed of a narrow piece of nylon or mylar. Once ejected from the rocket, it whips back and forth in the wind to create drag to slow the descent.
The propulsive force that moves something forward.
How does a Rocket Fly?
Students should be familiar with how a model rocket launches and all safety procedures that should be followed. The safety requirements can be found in the Model Rocket Safety Code of the National Association of Rocketry (NAR).
A Typical Model Rocket Flight
Thrust is the upward force that makes a rocket move off the launch pad. This is a demonstration of Newton’s Third Law of Motion: “For every action there is an equal and opposite reaction.” The action of the gas escaping through the engine nozzle leads to the reaction of the rocket moving in the opposite direction. The casing of a model rocket engine contains the propellant. At the base of the engine is the nozzle which is made of a heat-resistant, rigid material. The igniter in the rocket engine nozzle is heated by an electric current supplied by a battery-powered launch controller.
The hot igniter ignites the solid rocket propellant inside the engine which produces gas while it is being consumed. This gas causes pressure inside the rocket engine, which must escape through the nozzle. The gas escapes at a high speed and produces thrust. Located above the propellant is the smoke-tracking and delay element. Once the propellant is used up, the engine’s time delay is activated.
The engine’s time delay produces a visible smoke trail used in tracking, but no thrust. The fast-moving rocket now begins to decelerate (slow down) as it coasts upward toward peak altitude (apogee). The rocket slows down due to the pull of gravity and the friction created as it moves through the atmosphere. The effect of this atmospheric friction is called drag. When the rocket has slowed enough, it will stop going up and begin to arc over and head downward. This high point or peak altitude is the apogee. At this point the engine’s time delay is used up and the ejection charge is activated. The ejection charge is above the delay element. It produces hot gases that expand and blow away the cap at the top of the engine. The ejection charge generates a large volume of gas that expands forward and pushes the recovery system (parachute, streamer, helicopter blades) out of the top of the rocket. The recovery system is activated and provides a slow, gentle and soft landing. The rocket can now be prepared for another launch.
To summarize, the steps of the Flight Sequence of a Model Rocket are:
- Electrically ignited model rocket engines provide rocket liftoff.
- Model rocket accelerates and gains altitude.
- Engine burns out and the rocket continues to climb during the coast phase.
- Engine generates tracking smoke during the delay/coast phase.
- Rocket reaches peak altitude (apogee). Model rocket ejection charge activates the recovery system.
- Recovery systems are deployed. Parachutes and streamers are the most popular recovery systems used.
- Rocket returns to Earth.
- Rocket touchdown! Replace the engine, igniter, igniter plug and recovery wadding. Rocket is ready to launch again!
Various recovery systems are used depending on rocket size and weight. While this lesson focuses on the streamer as a recovery system, the systems used in Estes model rockets include:
- Break-Apart – Recovery is accomplished by the rocket separating in the middle and free falling back to the ground.
- Featherweight – Used strictly for light rockets. When the ejection charge activates, the engine is ejected, and the rocket falls lightly to the ground.
- Glide – The engine’s ejection charge converts the rocket into a glider by separating the glider from the booster rocket. The glider’s wings then generate lift, allowing it to settle slowly to the ground.
- Helicopter – Vanes on the rocket are activated when the ejection charge fires. Lift is created when the vanes rotate and the rocket settles slowly to the ground.
- Tumble – The center of gravity is shifted behind the center of pressure. (The center of gravity is the point where the rocket balances evenly. The center of pressure is the point where the aerodynamic forces are evenly distributed.) Tumble can be accomplished by allowing the ejection charge to push the engine casing backwards, but not out of the rocket. The rocket is unstable and tumbles end over end producing high drag which slows the rocket as it falls. This method is often used for recovering lower stages of multi-stage rockets.
- Parachute – The parachute is the most common form of recovery. Drag is produced by the parachute to slow the rocket. The parachute is attached to both the nose cone and the body tube. Flame-resistant recovery wadding must be placed between the engine and the parachute. If wadding is not placed in the rocket, the engine could melt or burn holes into the parachute.
- Streamer – A streamer is attached to the rocket and ejected by the ejection charge. It whips through the air causing drag to slow the rocket. The larger the streamer, the slower the rocket descends.
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