Method Article

High-Speed Optical Diagnostics of a Supersonic Ping-Pong Cannon

DOI:

10.3791/64996

⸱

March 24th, 2023

 , 
1Department of Physics and Engineering, Bethel University

In This Article

Summary

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We describe a method for the construction of a supersonic ping-pong cannon (SSPPC) along with optical diagnostic techniques for the measurement of ball velocities and the characterization of propagating shock waves during the firing of the cannon.

Abstract

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The traditional ping-pong cannon (PPC) is an educational apparatus that launches a ping-pong ball down an evacuated pipe to nearly sonic speeds using atmospheric pressure alone. The SSPPC, an augmented version of the PPC, achieves supersonic speeds by accelerating the ball with greater than atmospheric pressure. We provide instructions for the construction and utilization of an optimized PPC and SSPPC.

Optical diagnostics are implemented for the purpose of investigating the cannon dynamics. A HeNe laser that is sent through two acrylic windows near the exit of the pipe is terminated on a photoreceiver sensor. A microprocessor measures the time that the beam is obstructed by the ping-pong ball to automatically calculate the ball's velocity. The results are immediately presented on an LCD display.

An optical knife-edge setup provides a highly sensitive means of detecting shock waves by cutting off a fraction of the HeNe beam at the sensor. Shock waves cause refraction-induced deflections of the beam, which are observed as small voltage spikes in the electrical signal from the photoreceiver.

The methods presented are highly reproducible and offer the opportunity for further investigation in a laboratory setting.

Introduction

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The PPC is a popular physics demonstration used to show the immense air pressure to which people are continually exposed1,2,3,4,5. The demonstration involves the placement of a ping-pong ball in a section of pipe that has an inner diameter that is approximately equal to the diameter of the ball. The pipe is sealed off on each end with tape and evacuated to an internal pressure of less than 2 Torr. The tape on one end of the pipe is punctured, which allows air to enter the cannon and causes the ball to exper....

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Protocol

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1. Building and assembly of the ping-pong cannon (PPC)

  1. Assemble all the components of the PPC according to Figure 1.
  2. Insert two high-clarity acrylic windows in the sides of the cannon to allow for optical probing across the interior of the cannon.
    1. Drill two 1/2 in holes through opposite sides of the PVC near the cannon's exit.
    2. Prepare two 1/8 in thick acrylic windows using a laser engraver. Download the three supplementary svg files.
      NOTE: There are three files labeled "JoVE_AcrylicWindows_Step1_Engrave.svg"
      (Supplementary File 1), &....

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Results

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Here, we provide instructions for the construction and utilization of a PPC and an SSPPC, along with the implementation of the optical diagnostics for shock characterization and velocity measurements. Representative experimental results are also provided. The completed systems of the PPC and SSPPC, along with necessary accessories, are shown in Figure 1 and Figure 2. The SSPPC is an augmented version of the PPC, where a driving, pressurized section of pipe is co.......

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Discussion

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We have presented a method for the construction of a PPC and an SSPPC along with optical diagnostics for the measurement of ball velocities and for the characterization of shock propagation near the exit of the cannon. The standard PPC is constructed with a 2 m section of 1.5 in schedule 80 PVC pipe. The pipe is fitted with flanges at each end, quick-connect vacuum fittings, and acrylic windows near the exit for laser diagnostics. A detailed schematic of the PPC is shown in Figure 1. Prior t.......

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Disclosures

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The authors have nothing to disclose.

Acknowledgements

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This work is supported by the NSF Division of Undergraduate Education (award # 2021157) as part of the IUSE: EHR program

....

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
15 V Current Limited Power SupplyNew Focus0901Quantity: 1
2" x 6" PlankHome DepotBTR KD-HT SQuantity: 1
5.0" 40-pin 800 x 480 TFT DisplayAdafruit1680Quantity: 1
Absolute Pressure GaugeMcMaster-Carr1791T30–20 Torr | Quantity: 1
Air CompressorPorter CableC20026 gallon | Quantity: 1
Arduino UNO Rev3ArduinoA000066Quantity: 1
ASME-Code Fast-Acting Pressure-Relief Valve
for Air		McMaster-Carr5784T13Nickel-Plated, 3/8 NPT, 125 PSI Set Pressure | Quantity: 1
Black Electrical TapeMcMaster-Carr76455A21Quantity: 1
BNC CableDigikey Number115-095-850-277M050-NDQuantity: 2
Broadband Dielectric MirrorTHORLABSBB05-E02400–750 nm, Ø1/2" | Quantity: 1
C-ClampMcMaster-Carr5133A153" opening, 2" reach | Quantity: 6
Cam ClampRockler58252Size: 5/16"-18 | Quantity: 2 (2 pack)
Digital Pressure GaugeOmega Engineering, Inc.DPG104S0–100 Psi Absolute Pressure, With Output and Alarms | Quantity: 1
Digital Pressure GaugeOmega Engineering, Inc.DPG104S0–100 Psi Absolute Pressure, With Output and Alarms | Quantity: 1
Draw LatchMcMaster-Carr1889A37Size: 3 3/4" x 7/8" | Quantity: 4
Driver Board for 40-pin TFT Touch DisplaysAdafruit1590Quantity: 1
Full Faced EPDM GasketPVC Fittings Online155G125125FF150Quantity: 2
Gasket MaterialMcMaster-Carr9470K4115" x 15", 1/8" thick | Quantity: 1
Glowforge PlusGlowforgeGlowforge PlusQuantity: 1
HeNe LaserUniphase1108Class 2 | Quantity: 1
High Tack Box Sealing TapeScotch5334472 mm wide 
Laser Power SupplyUniphase1201-1115 V .12 A | Quantity: 1
LM311 ComparatorDigikey Electronics296-1389-5-NDQuantity: 1
Mirror MountTHORLABSFMP05Fixed Ø1/2", 8–32 Tap | Quantity: 1
Moisture-Resistant Polyester FilmMcMaster-Carr8567K10210' x 0.0005" x 27" | Quantity: 1
Moisture-Resistant Polyester FilmMcMaster-Carr8567K1210' x 0.001" x 40" | Quantity: 1
Moisture-Resistant Polyester FilmMcMaster-Carr8567K2210' x 0.002" x 40" | Quantity: 1
Mourtise-Mount Hinge with HolesMcMaster-Carr1598A52Size: 1" x 1/2" | Quantity: 4
Needle ValveRobbins Aviation IncINSG103-1PQuantity: 1
Non-Polarizing Cube BeamsplittersTHORLABSBS037Size: 10 mm | Quantity: 2
Nonmetallic PVC Schedule 40CantexA52BE12Quantity: 2.5 m 
Oatey PVC Cement and PrimerPVC Fittings Online30246Quantity: 1
Oil-Resistant Compressible Buna-N Gasket with Holes and AdhesiveMcMaster-Carr8516T4541-1/2 Pipe Size, ANSI 150, 1/16" Thick | Quantity: 1
OscilliscopeTektronixTBS2102Quantity: 1
PhotoreceiverNew Focus1801125-MHz | Quantity: 2
Ping Pong BallsMAPOLFBA_MP-001Three Star
Platform Mount for 10mm Beamsplitter and Right-Angle PrismsTHORLABSBSH104-40 Tap | Quantity: 1
Proofgrade High Clarity Clear AcrylicGlowforgeNAThickness: 1/8" | Quantity: 1
Sch 80 PVC CapPVC Fittings Online847-040Size: 4" | Quantity: 1
Sch 80 PVC PipePVC Fittings Online8008-040AB-5Quantity: 5 ft
Sch 80 PVC Reducer CouplingPVC Fittings Online829-419Size: 4" x 1-1/2" | Quantity: 1
Sch 80 PVC Slip FlangePVC Fittings Online851-015Size: 1 1/2" | Quantity: 3
Silicone Sealant Dow CorningMcMaster-Carr7587A23 oz. Tube, Clear | Quantity: 1
Steel Corner BracketMcMaster-Carr1556A42Size: 1 1/2" x 1 1/2" x 1/2" | Quantity: 16
Vacuum PumpMastercool MSC-90059-MD1 Stage, 1.5 CFM, 1/6HP, 115V/60HZ

References

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  1. Peterson, R. W., Pulford, B. N., Stein, K. R. The ping-pong cannon: A closer look. The Physics Teacher. 43 (1), 22-25 (2005).
  2. Olson, G., et al. The role of shock waves in expansion tube accelerators. American Journal of Physics. 74 (12), 1071-1076 (2006).
  3. ....

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Tags

Supersonic Ping Pong CannonOptical DiagnosticsShock Wave DetectionKnife Edge SetupBall Velocity MeasurementPhotoreceiver SensorOscilloscope TracesPressure DifferentialMach NumberVacuum Pipe

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