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Rocket flight principles

Rocket flight principles. Newton’s Laws of Motion. Objects at rest will stay at rest, and objects in motion will stay in motion in a straight line, unless acted upon by an unbalanced force. Newton’s Laws of Motion. Force is equal to mass times acceleration. F = ma

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Rocket flight principles

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  1. Rocket flight principles

  2. Newton’s Laws of Motion • Objects at rest will stay at rest, and objects in motion will stay in motion in a straight line, unless acted upon by an unbalanced force.

  3. Newton’s Laws of Motion • Force is equal to mass times acceleration. F = ma • i.e. Higher the force, higher the acceleration. With the same force, heavier objects will have a lower acceleration.

  4. Newton’s Laws of Motion • For every action (force), there is always an opposite and equal reaction (force).

  5. Newton’s Laws of Motion

  6. Newton’s Laws of Motion

  7. Newton’s Laws of Motion

  8. Motion of Objects

  9. How Does the Rocket Move?

  10. Newton’s Laws of Motion

  11. Important Points of a Rocket • Center of Mass (CM or CG) • Center of Pressure (CP)

  12. Center of Mass / Gravity (CM) • the exact spot where all of the mass of that object is perfectly balanced. • the rocket will rotate about this point.

  13. Center of Pressure • The exact spot where surface area is the same on one side as the other. It exists when the air is moving past an object.

  14. Example: Center of Pressure • Which way does the weather vane arrow point? Which way is air moving?

  15. Example: Center of Pressure • The area towards the tail is higher so air imparts much more force on the tail end than the arrow end. More Surface Area Higher force than arrow end

  16. Example: Center of Pressure • The CP needs to be behind CM so that it moves only at the tail end. • You need to put CP behind CM in a similar manner to stabilize your rocket.

  17. Forces on the Rocket

  18. Forces on the Rocket • Thrust: the force that moves the rocket up in the air. • Drag: the force which resists the motion of an object as it moves through a fluid (e.g. air).

  19. Forces on the Rocket • Lift: the force that is perpendicular to the direction of drag and depends on the density of the air • Weight: the force which pulls the an object down due to gravity.

  20. Which forces can you control and how? • Decrease Weight • Increase Thrust • Decrease Drag by improving aerodynamics

  21. Aeorodynamics

  22. Aeorodynamics • Refers to motion of fluids (liquid, gas, air) and their effects on the motion of a moving object. • Aerodynamic Forces: drag, lift • The shape of the object can be changed to improve aerodynamic forces.

  23. Improving Aerodynamics

  24. Improving Aerodynamics

  25. Which one has better aerodynamics?

  26. Which one has better aerodynamics?

  27. Which one has better aerodynamics?

  28. Which one has better aerodynamics?

  29. Effect of Shape on Drag

  30. Improving Rocket Aerodynamics Mass at the top moves the center of mass closer to the nose Nose makes the air flow around the rocket Water produces a sustained thrust but also moves the CM down. Fins increase surface area and move the center of pressure towards the bottom.

  31. Tasks • Run the first simulator with different amounts of water. • Record Volume and Height • Draw a Volume vs. Height (line) graph • What volume of water gives the best height?

  32. Tasks • Run the second simulator with different number of fins, placement of fins, nose, and different rocket weights. • Explain what happens to the height when you change each of the above variables. How does mass of rocket, # of fins and their placement, and shape of nose affect the height?

  33. Force Calculations • If the mass of a rocket is 1.0 kg and a pressure of 100 psi is applied to it. Calculate its acceleration in m/s2 if there is no drag. • Diameter of bottle = 1 inch • psi = pounds per square inch • 1 psi = 6 894.75729 Pascals • 1 pound of force = 4.448 Newtons • 1 Newton = 1 kg. m /s2

  34. Steps • Measure total force using area and pressure in pounds • Convert pounds (of force) into “Newtons” • Take away the gravity force (m x g) • Use force (F) in Newtons, mass (m) in kilograms, and Newton’s second law to calculate the acceleration (a ) in m/s2.

  35. Total Area = 1 inc x 3.14 = 3.14 square inch • Total Thrust Force = 100 psi x 3.14 sq.inch = 314 pound = 314 pound x 4.448 Newtons/ pound = 1397.38 Newtons

  36. Gravity Force = 1 kg x 9.8 m/s2 = 9.8 Newtons • Net Force = 1397.38 – 9.8 = 1387.58 Newtons

  37. Maximum acceleration The rocket’s speed would increase to 1387.58 m/s within a second! Due to the drag force the acceleration is much much lower. Drag increases as the rocket increases its speed!

  38. Estimating Height • y = maximum height of the rocket • t = time for the rocket to fall to the ground from its maximum height . • Measure t on a step watch. Start it when the rocket flips it direction.

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