Aerodynamics & Hydrodynamics

You probably see planes flying every day, and don't think much about it. But until the 1900's, the only animals flying were birds and insects, certainly not people. How does an airplane get off the ground? How does a rocket send a satellite to explore another planet? How do engineers design better airplanes, helicopters, rockets, and ships? On this page you'll find projects to let your imagination fly.

Winglets in Wind Tunnels

Objective

The goal of this project is to measure the changes in airfoil performance when winglets are added to the airfoil.

Introduction

Photo

The Boeing jet in the picture at right has winglets at the tips of its wings. Why are they there? What do they do?

As an airplane moves through the air, the wings generate lift by creating an area of low pressure above the upper surface of the wing. The higher air pressure beneath the lower surface of the wing lifts the plane. At the tip of the wing, the high and low pressure air meet.

Diagram of wing tip vortices from a passenger jet.
Figure 1. The diagram shows the expanding wing tip vortices generated by a passenger jet. (NASAexplores.com, date unknown)

The air forms miniature tornadoes, called wing tip vortices that spread out behind the plane (see Figure 1, right). Wing tip vortices cause two problems:

  1. the turbulent airflow they create can be strong enough to flip an airplane that encounters it;
  2. they also increase the drag forces on the airplane that generates them, decreasing fuel efficiency.
Winglets break up wing tip vortices, alleviating both of these problems.

The airflow around winglets is complex. Your wind tunnel should include smoke or fog in the airflow so that you can visualize streamlines along the length of the airfoil. Figure 2, below, illustrates some design considerations you may wish to consider for the winglets (Hepperle, 2006). A gradual curve transistioning from airfoil to winglet may help to reduce turbulent flow at the corner region. Translating the winglet toward the trailing edge of the airflow can also promote laminar flow at the trailing edge of the wingtip.

Three different winglet designs. From left to right: no winglet, rounded corner, sharp corner, winglet translated toward trailing edge.
Figure 2. Three different winglet designs. From left to right: no winglet, rounded corner, sharp corner, winglet translated toward trailing edge. (Hepperle, 2006)

In this project, you will test airfoils built both with and without winglets in a wind tunnel. Do you see evidence for wing tip vortices when testing airfoils without winglets? Does the addition of winglets alleviate wing tip vortices? Do the winglets increase lift? For winglet-related project ideas that do not require a wind tunnel, see the Variations section.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • airfoil,
  • chord line,
  • mean camber line,
  • camber,
  • aspect ratio,
  • angle of attack,
  • winglets,
  • drag,
  • lift,
  • wing tip vortices.

Questions

  • What are the forces acting on an airfoil in a wind tunnel?
  • How will the addition of winglets affect these forces?
  • How will the addition of winglets affect flight performance?

Bibliography

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • materials for building model airfoils, e.g.:
    • balsa wood for framework,
    • tissue paper covering,
    • modeling knife,
    • glue,
    • airplane dope.
    • (Alternatively, airfoil sections can be shaped from solid pieces of balsa or other wood.)
  • wind tunnel for testing airfoils (See the Materials and Equipment section of the Aerodynamics & Hydrodynamics page for information on building your own wind tunnel: Wind Tunnel Construction Links.)

Experimental Procedure

  1. Do your background research so that you are knowledgeable about the terms, concepts, and questions above.
  2. Construct two or more airfoils, identical in shape except for the presence/absence of winglets. See Figure 2 in the Introduction for ideas on different winglet designs you might wish to consider.
  3. Test your airfoils in a wind tunnel. The measurements that you are able to make will depend on the instrumentation available. Desirable measurements are:
    1. lift,
    2. drag,
    3. visualization of streamlines at the wing tip (using smoke or fog).

Variations

  • For a much more basic project on winglets using paper airplanes, see the Science Buddies project Why Winglets?.
  • The simple folded airplanes used in the project just mentioned normally lack vertical stabilizers. Vertical stabilizers counteract imbalances in lift between the two wings, and thus resist forces that would tend to make the plane roll. In this simple type of paper airplane, winglets can function as vertical stabilizers. Another type of paper airplane (made with laminated construction methods) generally does include a vertical stabilizer as part of the design. For more details, see the Science Buddies project What Makes a Good Aerodynamic Design? Test Your Ideas with High-Performance Paper Gliders. Do winglets improve the flight characteristics of high-performance paper gliders?

Credits

Andrew Olson, Ph.D., Science Buddies

Efficient Propeller Design

Objective

The goal of this project is to investigate how changes in chord length affect the efficiency of propellers.

Introduction

A propeller, like an airplane wing, is an airfoil: a curved surface that can generate lift when air moves over it. When air moves over the surface of a moving propeller on an airplane, the air pressure in front of the propeller is reduced, and the air pressure behind the propeller is increased. The pressure imbalance tends to push the airplane forward. We say that the propeller is generating thrust.

The same principle applies to helicopter propellers, only now the propeller rotates around the vertical axis. The pressure on top of the propeller is reduced, and the pressure underneath is increased, generating lift.

The illustration below (Figure 1) defines some terms that are used to describe the shape of a propeller. The radius (r) of the propeller is the distance from the center to the tip. The chord length (c) is the straight-line width of the propeller at a given distance along the radius. Depending on the design of the propeller, the chord length may be constant along the entire radius, or it may vary along the radius of the propeller. Another variable is the twist angle (β) of the propeller, which may also vary along the radius of the propeller.

propeller geometry
Figure 1. Illustration of terms used to describe propellers. The radius, r, of the propeller, is the distance from the center to the tip, along the center line. The chord length, c, is the straight-line width of the propeller at a given distance along the radius. The twist angle, β, is the local angle of the blade at a given distance along the radius (Hepperle, 2006).

In this project you will investigate how changing the chord length affects the efficiency of the propeller. You will keep the other design features (radius and twist angle) constant, changing only the chord length of the propeller. To measure the efficiency of the propeller, you'll connect the propeller to the shaft of a small DC motor. You will use the breeze from a household fan to make the propeller turn, which will cause the shaft of the motor to spin. In this configuration, the motor will act like a generator. You'll monitor the voltage produced by the motor to determine the efficiency of the propeller.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • propeller terms:
    • chord,
    • radius,
    • pitch,
    • rotational speed (measured in revolutions per minute or RPMs);
  • airfoil,
  • forces on an airplane in flight:
    • thrust,
    • drag,
    • lift,
    • weight.

Questions

  • How do you think increasing the chord length will affect the efficiency of the propeller?

Bibliography

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • four (or more) propellers:
    • You'll need to make these with varying chord lengths (but identical radius and twist angles).
    • One potential source for materials to make these can be found at Freedom Flight Models (scroll down to see the propeller kits).
    • Another potential source for propellers would be a local hobby shop that sells airplane models.
    • If you are handy with tools and experienced with model building, you could also try carving propellers from a soft wood, like pine. It takes quite a bit of skill and patience to keep the twist angle the same for the different propellers!
  • small 1.5-3 V DC motor (e.g., Radio Shack part number 273-223),
  • 1/4 Watt, 4.7 kΩ resistor (e.g., Radio Shack part number 271-1124),
  • jumper leads with alligator clips (e.g., Radio Shack part number 278-1156),
  • digital multimeter (e.g., TM-162 from TechBuys.Net),
  • fan.

Disclaimer: We occasionally provide information (such as part numbers, supplier names, and supplier weblinks) to assist our users in locating specialty items for individual projects. The information is provided solely as a convenience to our users. We do our best to make sure that part numbers and descriptions are accurate when first listed. However, since part numbers do change as items are obsoleted or improved, please send us an email if you run across any parts that are no longer available. We also do our best to make sure that any listed supplier provides prompt, courteous service. We receive no consideration, financial or otherwise, from suppliers for these listings.

Experimental Procedure

  1. Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
  2. First you will need to make four (or more) different propellers, keeping the propeller radius and twist angle (pitch) constant, while systematically varying the chord length.
  3. For testing, attach a propeller securely to the shaft of the DC motor. Depending on the materials used for the propeller, it could be taped on to the motor shaft, or drilled and press-fit.
  4. Connect the 4.7 kΩ resistor across the terminals of the motor, and also connect the terminals to the voltage inputs for the multimeter.
  5. Turn the multimeter to read DC volts, in the range for tens of millivolts.
  6. Starting with the fan on low speed, hold the propeller/motor assembly in front of the fan. You'll want to test in the exact same spot each time.
  7. The propeller may need a small push to start turning in order to overcome the internal friction of the motor. The moving air from the fan should keep the propeller turning after this. If not, turn the fan to the next speed and try again.
  8. Observe and record the reading from the multimeter in a data table in your lab notebook. The reading will fluctuate slightly. You can round the reading to the nearest millivolt. Note that the reading will be quite sensitive to distance from the fan. Make sure that all of your measurements are taken at the same distance from the fan.
  9. The mounting of the propeller to the motor may also affect the reading. If you are taping the propeller in place, you should repeat your measurements after removing and remounting the propeller to see how consistent your results are.
  10. Repeat the measurements for each propeller.
  11. Calculate the average voltage reading from the measurements for each propeller. More advanced students should also calculate the standard deviation.
  12. Make a graph of the voltage produced (y-axis) vs. chord length of the propeller (x-axis). Is there a systematic relationship between chord length and rotational speed of the propeller?

Variations

  • Test different propellers with different chord lengths while holding twist angle and mass of the propeller constant. To keep the mass constant, you will need to reduce the radius somewhat as the chord length increases. Do you find the same results as when the radius was held constant? Why or why not?
  • Test the propellers at different fan speeds and compare the results. Do the same relationships between the propellers hold at all fan speeds?
  • There are a number of possible variations on this project. Instead of examining the effect of the propeller's chord, you could investigate:
    • twist angle (pitch), Freedom Flight sells a handy jig for measuring the twist angle of a propeller (see Figure 2, below), or you could make one of your own.

      propeller pitch gauge
      Figure 2. Propeller pitch gauge from Freedom Flight Models.

    • airfoil shape (camber of the propeller),
    • blade shape,
    • number of blades,
    • sweep (like a swept wing).
  • This project uses an indirect method for measuring the propeller's rotational speed. Devise a way to measure the thrust produced by the propeller directly. For example, you could design a low friction mount for the motor that allows the motor to slide back and forth (along the propeller mount axis). Connect the motor to a gram spring scale to measure the force produced when the motor turns the propeller. How does thrust produced change with voltage applied to the motor? (Increasing voltage increases the rotational speed of the propeller.) How does the thrust measurement compare to the rotational speed measurement from this project?

Credits

Andrew Olson, Ph.D., Science Buddies

Which Wing Design Creates the Greatest Lift?

Objective

In this project, you will discover which wing (airfoil) design would create the greatest aerodynamic lift.

Introduction

This is a project that can be as challenging as you want to make it. There is always more to learn about aerodynamics, so you can keep refining your designs and trying out new ideas as your knowledge grows.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • airfoil,
  • lift,
  • drag,
  • chord line,
  • mean camber line,
  • camber,
  • aspect ratio,
  • angle of attack.

Questions

  • What are the four forces on an airplane in flight?
  • What are the factors that affect the ability of an airfoil to generate lift?

Bibliography

  • NASA's Glenn Research Center has a wealth of information on Aeronautics. We recommend that you take some time to explore this site, there's a lot of good stuff here. The "Guided Tours" are an excellent way to navigate through the material.
    Benson, T., 2005. "Beginner's Guide to Aeronautics," NASA Glenn Research Center [accessed January 16, 2006] http://www.grc.nasa.gov/WWW/K-12/airplane/index.html.
  • This page has links to several sources of information on aerodynamics:
    O'Sullivan, J., 2001. "Aerodynamics Information," Aerospaceweb.org [accessed January 16, 2006] http://www.aerospaceweb.org/question/aerodynamics/q0020.shtml.
  • Here are links to two different online airfoil simulation programs (both require a Java-enabled Web browser). You can test and refine your design ideas on the computer before building the actual models. Both simulators have instructions on how to use them.

Materials and Equipment

This project requires access to a wind tunnel for testing the airfoil designs that you make. Please refer to the "Materials and Equipment" section of the Aerodynamics & Hydrodynamics home page for information on building a wind tunnel.

  • airfoils,
  • wooden supports,
  • weights.

Experimental Procedure

  • Six wing (airfoil) designs were created to be of equal length. Three designs were conventional and three were experimental.
  • Thin wooden supports of equal weight and length were created for each side of each wing and attached to allow the wing to pivot on the side supports.
  • A wind tunnel was created with a one speed motor. Within the tunnel a grid was created to produce a more smooth (laminar) air flow.
  • Each wing was flown at both a level position and at a 30 degree angle from a level position. Equal amounts of weight were added progressively to each side of the wing being tested until the wing could no longer hold a level or 30 degrees above level position.
  • After failure, the last successful amount lifted (wing, supports and weights were weighed) was recorded in grams.

Variations

  • If building a wind tunnel is not an option for you, it doesn't mean that you can't do an aerodynamics project. For example, kites are a great way to learn about aerodynamics. The Wright brothers used kites to test many of their design ideas for their airplane. For more information, see: The Wright Stuff: Using Kites to Study Aerodynamics.

Why Winglets?

Objective

The goal of this project is to measure the effects on flight performance when winglets are added to a paper airplane design.

Introduction

Photo

The Boeing jet in the picture at right has winglets at the tips of its wings. Why are they there? What do they do?

As an airplane moves through the air, the wings generate lift by creating an area of low pressure above the upper surface of the wing. The higher air pressure beneath the lower surface of the wing lifts the plane. At the tip of the wing, the high and low pressure air meet.

Diagram of wing tip vortices from a passenger jet.
Figure 1. The diagram shows the expanding wing tip vortices generated by a passenger jet. (NASAexplores.com, date unknown)

The air forms miniature tornadoes, called wing tip vortices that spread out behind the plane (see Figure 1, right). Wing tip vortices cause two problems:

  1. the turbulent airflow they create can be strong enough to flip an airplane that encounters it;
  2. they also increase the drag forces on the airplane that generates them, decreasing fuel efficiency.
Winglets break up wing tip vortices, alleviating both of these problems.

In this project, you will test paper airplanes built both with and without winglets and measure the effect on flight performance. When doing your background research, you should also study vertical stabilizers. In the simple designs used in this project, winglets will also function as vertical stabilizers.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • fuselage,
  • airfoil,
  • winglets,
  • vertical stabilizer,
  • horizontal stabilizer,
  • drag,
  • lift,
  • center of lift,
  • center of gravity,
  • wing tip vortices.

Questions

  • What are the three forces acting on a glider in flight?
  • What relationship between these forces is needed for stable flight?
  • How will the addition of winglets affect these forces?
  • How will the addition of winglets affect flight performance?

Bibliography

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • paper for making airplanes,
  • tape measure to measure flight distance,
  • an indoor location with open space to test-fly the planes.
  • Optional: stop watch to measure flight time.

Experimental Procedure

  1. Do your background research so that you are knowledgeable about the terms, concepts, and questions above.
  2. Start with your favorite paper airplane design. Figure 2, below, shows one popular model (see the first suggestion in the Variations section, below, for ideas on optimizing the design). This NASA link has another design you can try: http://www.grc.nasa.gov/WWW/K-12/WindTunnel/Activities/foldairplane.html.

    Plan for simple folded paper airplane.
    Figure 2. The simple, classic folded paper airplane.

  3. Using your chosen design, build several identical paper planes.
  4. Test-fly each plane at least 5 times, and measure the distance flown. Be careful to launch the planes at the same angle, and with the same amount of force each time. Note any instabilities in the flight characteristics (nose dives, rolling, turning). Optional: you can also use a stop watch to measure the flight duration. Keep track of the data in your lab notebook.
  5. Fold a small portion of each wing tip up to create equal-sized winglets on each wing, and repeat the test flights.
  6. Calculate the average flight distance for each plane, both with and without winglets.
  7. Did flight distance improve with winglets? Were there improvements in other flight characteristics?

Variations

  • Experiment with the design of the simple folded airplane to optimize the flight characteristics before trying winglets. For example, you can shorten the plane by folding back a portion of the nose before folding up the wings (step 3 in Figure 2, above). (What effect does this have on the center of gravity? What effect does this have on the center of lift?) You can alter the surface area of the wings slightly by experimenting with exactly where to place the fold in step 4 of Figure 2. Test your designs with multiple flight tests and keep track of the results in your lab notebook. Then use your best design to see if winglets improve performance even further.
  • Experiment to find the optimal size for winglets.
  • Does it matter if you fold the winglets down or up?
  • The simple folded airplanes used in this project normally lack vertical stabilizers. Vertical stabilizers resist forces that would tend to make the plane yaw (nose moving from side to side). In this simple type of paper airplane, winglets can function as vertical stabilizers. Another type of paper airplane (made with laminated construction methods) generally does include a vertical stabilizer as part of the design. For more details, see the Science Buddies project What Makes a Good Aerodynamic Design? Test Your Ideas with High-Performance Paper Gliders. Do winglets improve the flight characteristics of high-performance paper gliders?
  • For a more advanced project on winglets using a wind tunnel, see the Science Buddies project Winglets in Wind Tunnels.

Sources

Buoyancy of Floating Cylinders

Objective

The goal of this project is to measure how the tilt angle of cylinders floating in water depends on the aspect ratio (length/diameter) of the cylinder.

Introduction

If you place a wooden disk in water, it floats 'face up,' i.e., with the circular cross-section parallel to the surface of the water. However, if you place a long wooden cylinder in water, it floats with the circular cross-section perpendicular to the surface of the water (see Figure 1).

floating disk and floating cylinder
Figure 1. Illustration of a floating disk (A) and a floating cylinder (B).

If you think about it, a disk is a cylinder, too. A disk is just a very short cylinder, and 'disk' is just a special name for this type of cylinder. How short does a cylinder need to be before we call it a disk, or is there something more to it? A coaster for a hot cup of coffee certainly fits our concept of a disk. A ceramic coaster might be almost a centimeter tall and ten centimeters in diameter. However, we wouldn't call a one-centimeter length of pencil lead a disk, we'd call it a cylinder. That's because the diameter of the pencil lead is only 0.05 cm (0.5 mm). So apparently we consider both the length and the diameter of a cylinder when we're deciding whether or not it's a disk.

A handy way to consider both numbers at once is to use a ratio. For example, if we can use the ratio:

The aspect ratio of a cylinder is the cylinder's length divided by its diameter.

The coaster has an aspect ratio of 1/10, and the pencil lead has an aspect ratio of 1/0.05 or 20. So perhaps what we mean by a disk is a cylinder with an aspect ratio <>

Does the way a cylinder floats also depend on its aspect ratio? Since the disk floats face-up, but a longer cylinder floats with the circular faces perpendicular to the surface, does that mean that there are cylinders with intermediate aspect ratios that would float at intermediate angles? Do an experiment to find out!

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • aspect ratio.

More advanced students should also study:

  • buoyancy,
  • volume,
  • mass,
  • density,
  • center of gravity,
  • center of buoyancy,
  • righting moment.

Questions

  • What is the difference between the center of gravity of the cylinder and its center of buoyancy?

Bibliography

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • wood dowels,
  • small handsaw for cutting dowels to various lengths, notes:
    • You may even want to visit a hobby store to purchase a small aluminum miter box with a razor saw to go along with it. With a miter box to hold the dowel in place, it is easier to make perpendicular cuts.
    • X-acto and Zona are two quality brand names to look for. Both companies offer miter boxes and saws.
  • dish pan or large plastic box,
  • water,
  • food coloring,
  • metric ruler,
  • protractor,
  • pencil,
  • blank paper,
  • graph paper,
  • calculator.

Experimental Procedure

  1. Use a hand saw to cut cylinders of various lengths from a long piece of dowel. You'll need to experiment and figure out what range of lengths you need in order to see different tilt angles in water!
  2. Measuring the aspect ratio of your cylinders is easy. Just measure the length (in cm) and the diameter (in cm), then divide the length by the diameter.
  3. Measuring the tilt angle of the floating cylinders is a bit trickier. Here's how:
    • Carefully float the cylinders in water with food coloring added.
    • Allow the cylinders to float, undisturbed, for several hours.
    • The dye from the food coloring will stain the underwater portion of each cylinder. After a few hours, there will be a distinct line of dye marking the water line on each cylinder.
    • Remove the cylinders from the water and allow them to dry.
    • Note: if you like, you can also float the cylinders in colored liquid Jello, then allow it to set in the refrigerator. (You may need to occasionally nudge the cylinders away from the edge of the dish.) The food coloring in the Jello will stain the submerged portion of each cylinder.
  4. Use the following steps to measure the tilt angle of each cylinder:
    1. Using a pencil and ruler, draw a straight line on a piece of paper.
    2. Place the dyed cylinder over the straight line, and tilt it until the dye line on the cylinder is parallel with the line on the paper (Figure 2A).
    3. Holding the cylinder in place, place a ruler against the cylinder at the same angle. (Figure 2A).
    4. Move the cylinder out of the way and use the ruler to draw a straight line that intersects with the original line on the paper.
    5. Use your protractor to measure the angle between the two lines (Figure 2B).
    6. To keep track of your measurements, we suggest that you use a separate sheet of paper for each cylinder. Label each angle drawing with the length, diameter, and aspect ratio of the cylinder.

      measuring the tilt angle from the dyed dowel
      Figure 2. Measuring the tilt angle of the dyed dowel.

  5. Make a table of your results like the one below:
    Length
    (cm)
    Diameter
    (cm)
    Aspect Ratio
    (length/diameter)
    Tilt Angle
    (°)
  6. Make a graph of your results by plotting tilt angle (y-axis) vs. aspect ratio. Over what range of aspect ratios does the tilt angle change?

Variations

  • Try dowels of different diameters, but with the same density. For each diameter, cut dowels of various lengths and measure their flotation angles. Make a graph of flotation angle (y-axis) vs. length of the cylinder (x-axis). Use a distinct symbol for each diameter. How do the graphs compare for each cylinder diameter? Now make a graph of flotation angle (y-axis) vs. aspect ratio of the cylinder (length/diameter). Use the same symbols as before. How do these graphs compare?
  • Try cylinders with different densities. Is the relationship between flotation angle and aspect ratio the same or different? Can you find cylinders made of different materials but with the same density? Do they have the same relationship between flotation angle and aspect ratio?
  • For more advanced students: can you come up with an explanation of the physics behind the tilt angle vs. aspect ratio relationship? Can you figure out an equation that describes the relationship between tilt angle and aspect ratio? The following article will be a useful reference: Gilbert, E.N., 1991. "How Things Float," The American Mathematical Monthly, 98 (3, March): 201–216.

Sources

  • "How Things Float," The American Mathematical Monthly, 98 (3, March): 201–216.

Rocket Aerodynamics

Objective

The objective of this project is to measure the change in rocket performance based on selected differences in the rocket's design.

Introduction

Photo

Model rockets utilize small, commercially-manufactured rocket engines to enable speeds of up to several hundred miles per hour, while reaching altitudes as high as several thousand feet. By following the National Association of Rocketry, Model Rocket Safety Code, you can experiment with the aerodynamics of these rockets with almost complete safety. And, there are many possible experiments you can undertake (see "Variations" below).

Model rockets can make for an extremely fun and exciting science fair project!

Terms, Concepts and Questions to Start Background Research

To do an experiment in this area, you should do research that enables you to understand the following terms and concepts:

  • The four forces in flight: weight, thrust, drag, and lift
  • The equation for drag
  • Rocket stability: center of gravity, center of pressure

In addition, study the Model Rocket Safety Code and the proper means to construct a rocket.

Bibliography

Be sure to study the model rocketry sections (among others) of NASA's Beginner's Guide to Aeronautics. This excellent NASA Web site includes a rocket simulator called RocketModeler. http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm

Stine, G. Harry, and Stine, Bill. Handbook of Model Rocketry, 7th Edition. John Wiley & Sons, 2004. This book is the bible of model rocketry, containing a wealth of information on rocket design, construction, and competition.

You can find a wealth of general information at these sites:

Altitude tracking is important for many experiments in rocketry. These links contain excellent information about how to measure your rocket's altitude:

Materials and Equipment

Model rocketry supplies can be purchased at many hobby stores. Two of the primary manufacturers are:

Experimental Procedure

The National Association of Rocketry offers these tips for experimentation(1):

  • Plan to do at least three flights of identical rockets with identical engines for each variable that you want to test. There is a lot of "scatter" in the data from rocket-based experiments, and you will get much better results if you use the average of three or more flights for a data point rather than a single flight. This scatter is the result of a combination of experimental error (such as in measuring altitude), weather-based variations (such as in measuring parachute flight duration), and/or slight differences in the construction of the rocket or the motor. If you understand statistics, having multiple data averaged into a single point gives you the opportunity to impress the judges with an analysis of standard deviations and confidence intervals in your data.
  • Measuring a rocket's maximum altitude accurately is not easy, but is generally the best way to show conclusively how differences in rocket characteristics affect performance. Altitude measurement should be done using data from at least two trackers who look at the flight from different directions but about the same distance, and who communicate by radio to make their measurements at the same moment in the rocket's trajectory. This is generally either at the exact highest point or "apogee" or (this is easier) at the moment of parachute ejection. Using the more complex tripod-mounted trackers that measure both horizontal "azimuth" angle as well as vertical "elevation" angle gives far more accurate results than simple hand-held elevation-only trackers.
  • Measuring a rocket's flight duration is fairly easy, but the data is generally only useful for demonstrating differences in the performance of recovery systems (such as parachutes of various sizes) rather than the rocket. Because wind and thermal lift can have a significant and unpredictable effect on duration, you need to either do several flight tests and use averaged values for each duration data point, or you need to do all your tests in absolutely identical weather conditions. It is best to use two people with stopwatches to collect each duration data point, in case one loses sight of the model or has a stopwatch malfunction. If your hypothesis has to do with measuring the performance of recovery systems, you will get less scatter in the data if you can do "drop tests" of the rocket and recovery system from a roof or tower 30 feet or more in the air, rather than flight tests.
  • Make sure that you vary only one variable between flights. The height a rocket reaches depends on the engine type and delay time; the smoothness of the surface finish on the rocket; the weight of the rocket; and the shape/size/alignment of the rocket and all its parts (fins, launch lug, nose, etc.). How long it stays up depends on how high it goes, plus on the type and size of the recovery system, the weather conditions, and whether the recovery device deploys fully and properly. If your hypothesis is that rockets with one shape of nose go higher than with another shape, for example, make sure the rockets you test are identical in design, liftoff weight, and surface finish and fly them in the same weather conditions off the same launcher. Make sure that the nose cone difference is the only difference. And use identical motors (preferably from the same pack or with the same date-of-manufacture code on the casing) in all your tests of the two different rockets.

Variations

Tim Van Milligan, an aeronautical engineer and the president of rocket manufacturer Apogee Components suggests, "The most common science fair project tries to find the best fin shape that yields the highest altitude. This project is useless, and doesn't yield any valuable data."(2) See the original source for why this is the case.

Instead, the National Association of Rocketry suggests these possible experiments(1):

  • Predicted rocket altitude vs actual altitude achieved. How good are your theoretical predictions vs tracked altitude, what are the factors that go into making an accurate prediction?
  • Rocket fin size and location vs stability. How big must fins be to make a rocket stable, and why? What difference does it make where the fins are located, and why?
  • Effects of spin on rocket performance. What change occurs in the tracked height that a rocket reaches or the straightness of its boost if the fins are placed at a slight angle so that the rocket spins in flight, compared to an identical rocket whose fins are not angled?
  • Parachute shape and size vs performance. Which performs better, a round parachute with many shroud lines or a polygon shape of the same area with only a few shroud lines? How about a round chute with a spill hole in the middle vs a slightly smaller round chute with no spill hole and thus the same total chute area?
  • Streamer shape and size vs performance. Fly the same rocket design with a series of streamers of different lengths and widths but the same total area. Or use a series of streamers of identical size and shape but different materials. Which stays up longest and why?
  • Rocket surface finish or shape vs altitude performance. What difference does a smooth surface finish vs a coarse one make to the drag of the rocket, and thus to its altitude performance? Or compare the effect of nose cones of different shapes [be sure to include flat and hemispherical shapes among those you select], or of identical fins with and without airfoil streamlining. [How does the diameter of the rocket (keeping the weight and shape equal) affect performance?]

Credits

(1) Barber, Trip. "Model Rocketry in Science Fairs." National Association of Rocketry. http://nar.org/pdf/science_fair_rocketry.pdf, accessed October 2, 2004.

(2) Van Milligan, Tim. "What Type of Fin Shape is Best?" Apogee Components. http://www.apogeerockets.com/technical_publication_16.asp, accessed October 2, 2004.

What Makes a Good Aerodynamic Design? Test Your Ideas with High-Performance Paper Gliders

Objective

The goal of this project is to measure the change in flight characteristics of gliders resulting from changes in glider design.

Introduction

Photo

When you think "paper airplanes," your first thought is probably of the garden-variety glider quickly folded from a sheet of paper. This project will introduce you to an entirely different construction technique for building paper gliders. Instead of using a single sheet of ordinary paper, the parts for these gliders are built up (laminated) in several layers, cut from thicker, stiffer paper stock. With this method, you can make paper gliders that are much more like the real thing than a simple folded paper airplane. The laminated construction technique is not difficult to learn, and the materials are inexpensive. There are even commercial kits available to help you get started but, with a little experience, you'll be ready and able to try your own designs.

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • fuselage,
  • airfoil,
  • camber,
  • dihedral,
  • aileron,
  • vertical stabilizer,
  • horizontal stabilizer,
  • elevator,
  • rudder,
  • center of lift,
  • center of gravity.

Questions

  • What are the three forces acting on a glider in flight?
  • What relationship between these forces holds for stable flight?

Bibliography

  • You'll definitely want to check out the Gliders section (among others) of NASA's Beginner's Guide to Aeronautics. This site is packed with useful information on the science of flight:
    http://www.grc.nasa.gov/WWW/K-12/airplane/guided.htm.
  • This is a really good book, with pictures of many different airplane designs and information about how well they flew in the contest. The book also has chapters on paper glider design and construction, and tips for adjusting ("trimming") gliders for best flying:
    Editors of Science 86, 1985. THE Paper Airplane Book: The Official Book of the Second Great International Paper Airplane Contest. New York, NY: Vintage Books.
  • The Whitewings website has tips on laminated paper glider construction, adjustment and flying (click on the link for "Assembly/Tuning/Piloting" and step through the list of topics):
    AG Industries, 2004. "Assembly/Tuning/Piloting Whitewings," AG Industries. http://www.whitewings.com/what/index.html.
  • This website has a plan for a simple glider built with laminated construction methods. You can print the plan on cardstock or smooth Bristol board and then build the plane: Ivey, M., 2004. "Airplane Tuneup and Flying," Zovirl Industries, Mark Ivey's Weblog [accessed November 14, 2006] http://zovirl.com/2006/tags/paper-airplanes/.

Materials and Equipment

  • The materials for this project are simple: paper and glue. However, the paper needs to be chosen carefully. Ordinary copier or notebook paper is not stiff enough. The paper used for the Whitewings kits is Japanese Kent paper, which you may be able to find at your local stationery store. Alternatively, ask for sheets of cardstock. Smooth bristol board, available at art stores, is a little heavier, but still useable. As for glue, ordinary white glue, Itoya O-Glue or PentelRoll are all fine choices.
  • The easiest way to learn the construction methods for laminated gliders is to buy and build one of the available "Whitewings" kits. Kits are available for single or multiple gliders. They are available in many hobby shops, and also online http://www.whitewings.com/.
  • Remember that each model will need to be properly adjusted ("trimmed") in order to achieve its best possible flying. See the Bibliography for more information.
  • For timing your flights, you'll need a stopwatch, or a watch with a second hand.
  • For measuring the distance of your flights, you can use yard markers on a football field, or you can use a tape measure to set up your own set of distance markers in the open area where you are flying your gliders.

Experimental Procedure

There are many possible experiments you can try with paper gliders (for some specific examples, see the Variations section, below). Here are some suggested measurements for quantifying your experiments:

  • flight distance,
  • time aloft,
  • flight maneuvers (i.e., descriptions of the flight: did the glider stall, dive, flip over, turn right, turn left, etc.).

With regard to experimental methods, here are some things to keep in mind:

  • There will be variations in performance from flight to flight for the same glider, so you should make sure to perform repeated trials for each condition. We suggest at least five trials for each condition (more trials won't hurt).
  • To minimize variability, make all of your test flights under the same conditions.
  • Change only one variable at a time when testing. If you are interested in more than one variable, that's great! (You'll just have to make more planes.)

Variations

Here is a sample of project ideas for experimenting with paper gliders. As your knowledge and experience grow, you will be able to add to this list on your own. The variations are arranged in order of increasing difficulty.

  • How Do Stabilizers Affect Glider Flight? As you are building the glider, leave off either the vertical or horizontal stabilizer (or build multiple gliders, with and without these parts). Test-fly the glider(s) with and without each type of stabilizer. What effect does each type of stabilizer have on flight?
  • What is the Optimal Size for a Stabilizer? Use the same basic design for a series of four or more planes, but vary the size of one of the stabilizers (vertical or horizontal) from smaller to larger than normal. Measure the flight performance of each glider. Think about how might you control for the difference in weight distribution.
  • Design for distance. Do your background research and develop a hypothesis about what type of glider will fly the furthest. Build a series of 4 (or more) gliders with one variable element changing systematically through the series to test your hypothesis.
  • Design for Time Aloft. Do your background research and develop a hypothesis about what type of glider will fly the longest. Build a series of 4 (or more) gliders with one variable element changing systematically through the series to test your hypothesis.
  • Investigating More Than One Design Element. Your hypothesis may involve more than one design element. For example, you may be interested in investigating both dihedral angle and camber. In order to compare planes with only one variable changing, you would need to build two (or more) planes for each dihedral angle you want to test, each with varying wing camber. Then you can make pair-comparisons where only dihedral angle was changed, or pair-wise comparisons where only wing camber was changed.

Sources

  • Editors of Science 86, 1985. THE Paper Airplane Book: The Official Book of the Second Great International Paper Airplane Contest. New York, NY: Vintage Books.
  • AG Industries, 2003. "Whitewings Science of Flight Lesson Plan," AG Industries. [accessed January 24, 2006] http://www.whitewings.com/edu/WWLessonPDF.pdf.

How Much Weight Can Your Boat Float?

Objective

The goal of this project is to determine how much weight can be supported by boat hulls of various volumes.

Introduction

You know from experience that if you drop a steel bolt in a bucket of water that it will sink like a rock to the bottom. On the other hand, you know that ships made of steel can float. How does it work?

What determines whether an object floats or sinks? It's the density (mass per unit volume) of the object compared to the density of the liquid. If the object is more dense than the fluid, it will sink. If the object is less dense than the fluid, it will float. If the object has the same density as the fluid it will neither sink nor float.

With a steel-hulled ship, it is the shape of the ship's hull that matters. The hull encloses a volume of air, so that the total density, defined as:

(mass of steel hull + mass of enclosed air) / volume,

is less than that of water.

Archimedes discovered that an object immersed in water displaces a volume of water equal to the volume of the object (see Junior Engineering, 1997, for the whole story). The displaced water creates an upward force on the object. If the weight of the displaced water is greater than the weight of the object, the object will float.

In this project you will make some boat hulls of various shapes and sizes using simple materials (like aluminum foil and tape). Can you predict how many pennies each of your boats will support without sinking?

Terms, Concepts and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

  • weight,
  • volume,
  • density,
  • buoyancy,
  • displacement.

Bibliography

Materials and Equipment

For building the boats you can use:

  • cellophane tape (e.g. "Scotch" tape), and
  • aluminum foil.

For measuring the volume of the boats, you will need either:

  • a ruler (for measuring the dimensions of the boat in order to calculate its volume), or
  • dry rice kernels and
  • a glass measuring cup with metric markings (or a graduated cylinder).

For testing the buoyancy of the boats you will need:

  • a container (e.g., sink, tub, bucket, dishpan) with water,
  • pennies.

Experimental Procedure

  1. Use the foil and tape to construct boat hulls with different shapes.
    1. You can fold or even cut the aluminum foil if you wish to obtain the desired shape.
    2. It is important to insure that there are no leaks!
    3. Try building several different boats using the same amount of aluminum foil for each.
    4. Also try building several different boats using different amounts of aluminum foil.
  2. Calculate the volume of each boat hull. Below are two alternative methods you could use. (Or, you could use both methods, and compare your results. Which method is more accurate?)
    1. Ruler Method
      • Use the ruler to measure the length, width, and height of your boat hull.
      • Volume (in cm3 equals length × width × height (each measured in cm).
      • If parts of the hull have an irregular shape, measure the volume piece-wise. Use triangles to approximate any areas of the hull that are curved or angled. Use rectangular prisms for regular areas of the hull. Calculate the volume of each (imagined) subsection. Add up the volumes of the individual regions to get the total volume for each hull.
    2. Dry Rice Method
      • Carefully fill the boat hull with dry rice. The rice should be level with the top of the hull.
      • Being careful not to damage the hull, pour the dry rice into the measuring cup (or graduated cylinder).
      • Gently shake the cup (or cylinder) to level the rice.
      • Read the volume of the dry rice, in mL. This is the volume of your boat hull.
  3. Measure the buoyancy of each boat hull.
    1. Carefully float the hull in the container of water.
    2. Gently add one penny at a time. Note that some boat shapes will be "tippier" than others. For these you will have to pay careful attention to balancing the load (left to right, front and back—or port to starboard, fore and aft, if you're feeling nautical) as you add pennies.
    3. Keep adding pennies until the boat finally sinks. Count how many pennies each boat could support before sinking (i.e., the penny that sank the boat does not count.
  4. Make a graph of buoyancy, measured in number of pennies supported (y-axis) vs. boat hull volume, in cm3 (x-axis). What do your results tell you about the relationship between buoyancy (amount of weight a boat can support) and volume of the boat hull?

Variations

  • By measuring the average weight of a penny, you can convert your buoyancy measurement from number of pennies to grams. If you don't have a scale at school or home, you can probably find a scale to use at the post office. Find out how much 10 or 20 pennies weigh (together). Calculate the average weight of a penny by dividing the total weight by the number of pennies. Now for each boat, you can multiply the number of pennies it could support by the average weight of a penny to convert your buoyancy measure to grams. Thinking about what you learned about displacement, how do think the buoyancy in grams will compare to the boat hull volume in cm3?
  • It would be difficult to bring a bathtub to the science fair in order to demonstrate your project, but there is a nice demonstration of buoyancy which you can show in a clear plastic soda bottle: a Cartesian Diver (Terrific Science Press, 2005).
  • Use other materials for building the boat hulls. For example, waxed half-gallon cartons (for milk or juice) can be cut open and unfolded to produce sheets of waterproof material. To make folds to create the desired hull shape, first score the material with a blunt stylus—the classic Bic pens with the blue plastic caps have a great shape for this. Keep the cap on and use it to score the waxed paperboard before folding.
  • Here's a "thought experiment" for more advanced students to try. NASA's Cassini spacecraft sent the European Space Agency's Huygens probe to the surface of Saturn's moon, Titan, where it found evidence that the surface contains large bodies of liquid methane (Phillips, 2005). On Earth, methane (CH4) is typically not liquid at all, and is known most commonly as 'natural gas.' On Titan, where the surface temperature is −179°C, water would be solid and methane is a flowing liquid. What is the density of liquid methane? How does the density of liquid methane compare to the density of water? If your boat could float 100 pennies in water, how many pennies would it support (on Earth) in a container filled with liquid methane? An actual experiment you could do would be to re-do the experiment with a liquid that has a density different than that of water. Cooking oil would be a good choice. Though the difference in density is not nearly as dramatic as for liquid methane, it's a lot easier to obtain and safer to work with! How does the buoyancy of each boat hull in vegetable oil (measured by the number of pennies it can support) compare to its buoyancy in water?

Sources

This project is based on:

Parachutes: Does Size Matter?

Objective

In this experiment you will test different sized parachutes to see how changes in the size of the parachute affect flight.

Introduction

In the sport of skydiving, a person jumps out of an airplane from a very high altitude, flies through the air, and releases a parachute to help them fall safely to the ground. The parachute slows down the skydiver's fall so that they can land on the ground at a safe speed. How does the parachute do this?

As the skydiver is falling, the force of gravity is pulling them towards the earth. The force of gravity can make an object fall very fast! The parachute slows the skydiver down because it causes air resistance, or drag. The air pushes the parachute back up, and creates a force opposite to the force of gravity, slowing the skydiver down. As the skydiver falls slowly to the earth, these "push and pull" forces are nearly in balance. The drag force from the parachute is slightly less than the force of gravity, so the skydiver floats slowly to the ground.

In this experiment, you will test whether the size of the parachute is important for slowing down the speed of the fall. You will make a series of parachutes from small to large and test how quickly they fall from the same height. Will the large parachutes fall more slowly than the small parachutes?


As the skydiver falls, the
forces of gravity and drag
are in balance
(SEED, 2006b).


Terms, Concepts and Questions to Start Background Research

To do this type of experiment you should know what the following terms mean. Have an adult help you search the internet, or take you to your local library to find out more!

  • parachute
  • air resistance
  • drag
  • load
  • gravity
  • surface area

Questions

  • How does a parachute work?
  • Do bigger parachutes work better than smaller parachutes?
  • How will increasing the diameter of the parachute increase it's size?

Bibliography

  • This project was based on two projects from the NASA Explores Program and one from the SEED program at Schlumberger:
  • Read all about parachuting at this web site developed by the SEED program at Schlumberger. You can read about how parachuting works, the equipment that is used, and the forces of gravity and drag. You can even read about the real life experiences of people who have tried skydiving:
    SEED, 2006b. "Adventures in Skydiving," Schlumberger Excellence in Educational Development (SEED). [accessed November 3, 2006] http://www.seed.slb.com/en/scictr/watch/skydiving/index.htm
  • At this site you can read about how parachutes can be used to rescue an aircraft. If you are an early reader, just click on the K-4 button at the top of the page. If you are a more advanced reader, click on the 5-8 button to read a more in-depth article:
    NASA, 2003c. "Safe Landing," NASA Explores: National Aeronautics and Space Administration (NASA). [accessed November 3, 2006] http://nasaexplores.com/show2_articlea.php?id=03-035

Materials and Equipment

  • heavy weight garbage bags
  • metric ruler
  • scissors
  • washers
  • twist ties
  • light weight string
  • stopwatch

Experimental Procedure

  1. Each parachute will be made out of the garbage bag material, so first cut open the garbage bags to make a flat sheet of plastic.
  2. You will make a series of parachutes of different sizes, from large to small. Each parachute will be square in shape, so the four sides will each be of the same length. A list of sizes to try are shown in the data table below:

    ParachuteLength of Each Side (cm)Surface Area (cm2)
    120400
    230900
    3401600
    4502500

  3. Cut out each of the four differently sized parachutes from the garbage bag material. One trick is to fold the plastic sheet in half twice so that it is four layers thick. Then cut the two edges (opposite the folded sides) down to half of the length you want your square to be. When you unfold it, you will have your square!
  4. Tie a knot in each of the four corners of your square. The knots will be used to anchor your string.
  5. Cut out four pieces of string for each parachute. Each piece of string should be 40 cm long.
  6. Tie one end of each piece of string around one of the four knots, positioning the string right above the knot.
  7. Hold the center of the plastic sheet in one hand and pull all strings with the other to collect them. Tie the free end of the strings together with an overhand knot:
    overhand knot
  8. Attach 4 washers to the bundle of strings with a twist tie. Be sure that each parachute has the same number of washers attached, or this will alter your results!
  9. Bring a stopwatch and the parachutes to a safe, high surface for your tests, about 2 meters from the ground. A good place for your test might be a secure balcony, deck or playground platform.
  10. Using your stopwatch, time how long it takes in seconds for each parachute to fall to the ground. If the parachute does not open during a trial, just do that trial over so that when you are finished you have three trials which all worked. Test each parachute three times, and make an average of your data. Calculate the average by adding together your three times, and then dividing your answer by three. You can also increase the number of trials above three to get better data and organize your data table accordingly. You should keep your data in a table, and here is an example for an experiment with three trials:

    Parachute

    #

    Trial 1

    (seconds)

    Trial 2

    (seconds)

    Trial 3

    (seconds)

    Average Time

    (seconds)

    1
    2
    3
    4

  11. Now make a graph of your data. Make a line graph of surface area vs. time by creating a scale of surface area in square cm on the left side of the graph (y-axis) and a time scale in seconds on the bottom of the graph (x-axis). Then make a dot each place where your data intersect. After you connect the dots, you line may slope up or down. What does this tell you about this relationship? How does it relate to your hypothesis?

Variations

In this experiment you tested one variable, the surface area of the parachute. What other variables could be tested? Try an experiment to test these other variables:

  • Load - change the number of washers to change the weight of the load
  • Height - drop the parachute from different heights
  • String Length - change the length of the supporting strings from short to long
  • String Weight - change the type of string from thin to thick
  • Material - use different material for the parachute (nylon, cotton, tissue paper, etc.)
  • Shape - try making parachutes of different shapes (circle, rectangle, triangle, etc.)

Credits

Sara Agee, Ph.D., Science Buddies

Sources

  • This project was based on two projects from the NASA Explores Program and one from the SEED program at Schlumberger:
  • Engineering News

    Central Board of Secondary Education

    Architecture News

    Management News

    Medical News

    Journalism News

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