Newton's Laws Relating to our Rocket's Motion

Launch to Powered ascent – what is

happening to the rocket? Is its motion changing? How is it changing? Which and how do the laws explain this motion? How is thrust generated? Which law and how does it explain thrust?

Newton's first law is an object in motion and will stay in motion, and an object at rest will stay at rest until acted on by an unbalanced force. Before the launch, the rocket is at rest. Demonstrating Newton’s third law, every action has an equal and opposite reaction. The weight of the rocket is balanced by the reaction of the earth to the weight. When the rocket is launched, Weight and Thrust act upon each other until the thrust becomes greater than the weight, and the net force is positive upward. The rocket then accelerates upward and the velocity increases. Exhibiting Newton’s third law, the exhaust flow is pushed backward, and the engine is pushed forward as a reaction. More specifically, through the combustion of fuel, hot exhaust gas is produced and accelerates at the rear of the rocket. The reaction is the thrusting force on the engine mount.

Coasting flight – why does the rocket

continue to ascend? Which law and how does it explain this?

 During the coasting flight Newton’s third law is in action. The force of weight and the thrust from the engine oppose each other equally, so the rocket continues to ascend. As the weight begins to increase, the forces are unbalanced and negative net force causes the rocket begins to move at a downward slope.

Slow Descent to Landing – what is happening to the rocket? What is responsible for this? Which law and how does it explain this motion?

During the slow descent and landing there is no longer the force of the thrust, so weight pulls the rocket downwards. Air resistance pushes up against the descending rocket but is only strong enough to slow it down a little bit. There is an unbalanced force and a negative net force that acts upon the rocket. Weight continues to act upon the rocket and the parachute opens up and causes more air resistance, slowing the rocket further until it finally reaches the ground.

Once the rocket has landed, it is at rest with no unbalanced forces act upon it. The weight of the rocket pushes down on the ground and the ground pushes back up against it with an equal and opposite force.

Constructing Our Rocket's Fins

Steps:

1) First, we decided on the fin’s shape. We did a little research, looking up different images of rockets to inspire us. Our first thought was to do a simple fin, like a triangle but with a slight hook on the end, but then we decided that it had to look “cooler”.  While applying this to our fin, we kept in mind that the three fins should be professional-looking and efficient.

2) Then, we cut out the fins from a piece of a manila folder, measuring accurately so that all three fins were the exact size.

3) Finally, we attached the fins to our rocket, folding out tabs so that it will be firmly glued on the body tube.  We made sure to glue the fins to the body symmetrically.

Rocket's Components and Engine

Model Rocket Components

Fins: provide stability during flight.

Engine mount: What the thrust of the engine is transmitted through.

Recovery Wadding: prevents hot gas from ejection charge from damaging the recovery system.

Engine Mount (Fixed): What the thrust of the engine is transmitted to the body through.

Parachute Lines: Connects the parachute to the nose cone.

Parachute: also called a streamer, part of the recovery system.

Nose Cone: is put into the body tube before flight.

Shock Cord: keeps all of the parts of the rocket together during recovery.

Launch Lugs: small tubes the launch rail is put into to stabilize the rocket while it launches. 

Model Rocket Engine:

Engine Casing: a cylinder made up of heavy cardboard, contains the nozzle, propellant, and other explosive charges.

Engine Mount: has ejection of hot gas from engine.

Ejection Charge: is ignited with the delay charge is completed burned through. 

Delay Charge: begins to burn with the flame front reaches the far left of the propellant.

Nozzle: a device used to accelerate hot gases and produce thrust.

Propellant: ejected from the rocket engine to produce thrust, packed into a solid cylinder.

NAR Safety Code

What does NAR stand for?

“NAR” stands for “the National Association of Rocketry”.

What do you think are the top 3 safety rules we must keep in mind

for our launch?

1.   Launch Safety: I will use a countdown before launch, and will ensure that everyone is paying attention and is a safe distance of at least 15 feet away when I launch rockets with D motors or smaller, and 30 feet when I launch larger rockets. If I am uncertain about the safety or stability of an untested rocket, I will check the stability before flight and will fly it only after warning spectators and clearing them away to a safe distance.

2.   Flight Safety: I will not launch my rocket at targets, into clouds, or near airplanes, and will not put any flammable or explosive payload in my rocket.

3.   Launch Site: I will launch my rocket outdoors, in an open area at least as large as shown in the accompanying table, and in safe weather conditions with wind speeds no greater than 20 miles per hour. I will ensure that there is no dry grass close to the launch pad, and that the launch site does not present risk of grass fires.

Describe the limits on the construction of a model rocket in your

own words.

The rocket should not weigh more than 1,500 grams (53 ounces) at liftoff.

It will not hold more than 125 grams (4.4 ounces) of propellant or 320 N-sec of total impulse.

Flight Path Diagram

This is our rocket's flight path diagram to illustrate the forces during each phrase.