Lab5: Rocket Optimization & VenturiGroup Number: _______ Section Number: _______ TA Initials: _______

Name ___________________________________

Other team members ___________________________________________________________________

Safety: When completing this lab, or when around people launching rockets, be aware of flying film canisters and stay clear of the landing zone to prevent disrupting science and hurting yourself. In order to protect from rogue rockets, safety glasses and lab coats, as always, are required. When working with the Bernoulli gripper, exercise appropriate caution with electrical devices and pressurized air devices.

Background: Engineers make decisions to maximize the performance or return on investment of their designs, within constraints of safety, ethics, available materials, etc. This principle is known as optimization and requires understanding competing needs or tradeoffs in particular design decisions. For instance, the engineers who designed the Cowboys Stadium in Arlington, Texas used optimization when they installed the largest operable glass roof in the world. The glass is coated with a photocatalytic titanium dioxide coating that uses sunlight to break down contaminants that obstruct the light. This required more capital cost, but lowered operating costs by keeping the glass clean without having to pay workers to manually clean the glass. As another example, an airline’s engineers calculate the amount of fuel needed to get a plane from one city to another. Too much fuel means a heavier plane that uses even more fuel, whereas too little fuel will not allow the plane to reach its destination or, in cases of emergency, not allow landing someplace else. Thus, there is an optimal amount of fuel.

Objective: The object of this lab is to optimize the amount of water you put into a 35 mm film canister rocket to maximize the horizontal distance the rocket goes. Water acts as a reaction mass that permits efficient thrust, but also takes up volume that would otherwise be occupied by energy-containing pressurized gas. These two factors lead to an optimal amount of water.

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Procedure: You have available a 35mm film canister with attached payload (a penny) and a snap-on lid, a graduated cylinder launcher with a 45-degree angle bracket, 2 Alka-Seltzer tablets, water, a syringe (for measuring water), and a measuring tape.

1. Break each Alka-Seltzer tablet into 4 pieces.2. To launch the rocket you must first set the cylinder on its base at a 45-degree

angle to the floor. 3. Fill the 35mm canister with desired amount of water, drop ¼ tablet in, put

the cap on, and then drop the canister lid- down into the cylinder. 4. It will take about 30 seconds for CO2 pressure to

build up sufficiently to pop the lid off, sending the rocket flying. Make sure the launcher is pointed in a safe direction.

5. Have two team members stand down range to see where on the floor the rocket first hits. Measure the distance from the launch point.

6. After every launch, be sure to rinse out the canister and lid, especially the lip where the lid is put on. Dry completely. This is important to maintain the seal.

7. Repeat this process for at least 6 trials at different amounts of water. Empty the water from the column each time. Choose amounts that are evenly spaced and cover a wide volume range. If you have extra time, you can collect additional points.

8. After you have gathered the data, make an Excel graph of water volume (mL) vs. distance (m). Right-click on the data series in the plot and select “Add Trendline” to make a second-order polynomial fit to the data. This will smooth out some of your experimental noise (uncertainties). The peak of the trendline will represent a more reliable optimum. If you select “Display Equation on chart” and

y=a x2+bx+c is your polynomial fit, then the x value where y is maximized is xopt=−b2a .

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Trial Vol water (mL) Distance (m)

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9. PRINT AND ATTACH YOUR GRAPH TO THIS REPORT. Make sure it is “pretty”—labeled axes, no lines in the background, etc. The figure above is an example (the data is simulated and not from actual measurements).

What is the optimal amount of water (include units) to maximize distance?

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The Venturi EffectBackground: Venturis are devices that use flow constriction to speed up the flow. This in turn lowers the pressure, and can even lead to a partial vacuum even though the flow upstream is at high pressure. Today you will experiment with a Venturi-type device also known as a Bernoulli gripper. Using flow of water or air, you can levitate a plastic disk underneath the flow device.

Equipment: The required equipment is set up on a lab bench for you to use. There is a water version and an air version of the experiment. You may choose to do either or both.

1. Water version: aquarium pump connected to the Bernoulli gripper device, and a set of numbered plastic disks to levitate.

2. Air version: adjustable air nozzle connected to the Bernoulli gripper device, and a set of numbered plastic disks to levitate.

Procedure: (This is for the water version; the air version operates similarly.)

1. Turn the pump on and lift the gripper about 10 cm above the water surface. Water should be streaming down into the basin.

2. Use the handle on the side of the gripper. Try to hold the device as level as possible.

3. Select a plastic disk (knob-side up) and press it against the underside of the gripper in an attempt to get it to stick.

4. Try all of the different-numbered disks. Attempt to detect the trend of how well they levitate under the gripper.

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Flow of water

Gripper device

Analysis:

1. Which experiment did you do: water or air? Which disks were you able to levitate for an extended period of time?

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Grading Rubric (to be completed by TAs)

Points MaxReasonable set of vol vs. dist measurements 4Excel plot is pretty 5Optimal vol consistent with measurements 5Bernoulli gripper completed 5Safety and cleanliness TA initial:______ 1

Total 20

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