Applications of the LIght Gas Gun in the High School Science Curriculum

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Center for Astrophysics, Space Physics and Engineering Research2008 Baylor University RET Program

Application of the Light Gas Gun in the High School Science CurriculumDr. Steve Rapp

Linwood Holton Governors SchoolP.O. Box 1987Abingdon, VA [email protected]

AbstractThe light gas gun (LGG) has been used inhypervelocity and low velocity impact studies for several years inthe research labs of the Center for Astrophysics, Space Physics, andEngineering Research (CASPER) at Baylor University. The physics ofthe gas gun is fascinating and could have many practical andrelevant applications in the high school science curriculum. Some of

those applications will be explored in this paper: Safety, Gas Laws,Optics, Projectile Speed, Kinetic Energy, Momentum, and NewtonsThird Law of Motion. This paper is designed to show how using theLight Gas Gun (LGG) in high and low velocity impact studies relatesto the physics being taught in the high school classroom. It is hopedthat the practical application of physics can be seen in the use ofthe LGG.

Introduction

What is a Light Gas Gun anyway?

The Light Gas Gun (LGG) is used to simulate hyper-velocity impacts

from space debris that may occur in space.Helium or Nitrogen is used as

propellant. The LGG works by releasing high pressure gas behind a projectile

into a very low pressure chamber. The low pressure area of about 100 mTorr

is created by a vacuum system. This practically eliminates air resistance for

the projectile. One thousand psi Helium produces projectile velocities up to

760-790 m/s. An image of the LGG at the Center for Astrophysics, Space

Physics & Engineering Research is shown on the next page (Image 1).
mailto:[email protected]:[email protected]


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The degree of damage to the target material depends on the type of

material, the material thickness, how fast the particle is moving, and the size

of the particle. The impactor will puncture the target or cut through it if the

target material is relatively thin. Usually if the impactor is larger than about a

third of the target material thickness the target will be punctured [1].

Image 2: Hypervelocity Impacts Caused by Meteoroids


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How Much Space Debris is There in Space?

According to a June 2007 article in Physics Today, an estimated

151,000,000 pieces of space debris of various sizes and altitudes exist.

Debris of .1-1 cm size make up about 150,000,000 of the total, while debris

of 1-10 cm size come in at approximately 650,000 pieces, and 22,000 debris

pieces of 10 cm or greater abounds. [2]. Graphic 3 below shows the

distribution of space debris around the Earth. Earth is developing a ring

similar to Saturn!

Image 3: Distribution of Space Debris Orbiting the Earth


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About 40,000 metric tons of micrometeoroids enter the Earths

atmosphere each year. The mass of all this space debris is approximately

2,000,000 kg [3]. This space debris is found at many different altitudes but it

seems that much of it clusters at about 700 km to 1000 km (see Image 4 on

the next page). Space debris impacts may cut tethers, cables, or cause

electrical short circuits that may endanger a mission. If the impacts occur in

a charged environment, the possibility of plasmas being produced is great.

This may cause electrical interference, disrupt current flow, or trigger

electrostatic discharges [3].

Image 4: Distribution of Catalogued Debris for Low-Earth Orbit: Thedifferences

between the 10 January (blue) and 31 March (red) curves are due to thetracked debris (green) from Chinas Fen Yun-1C satellite, destroyed in ananti-satellite test in January 2007. (adapted from ref. 2)


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Major Light Gas Gun Components

Barrel: barrels are interchangeable depending on the size of the

projectile. The particle travels down the barrel to the target chamber.

Roughing Pump: maintains vacuum within the barrel; Laser Fans: are used to

determine velocity of the projectile; Target Chamber: plate to be impacted is

placed here; Firing Chamber: area in which the projectile is placed (see

Image 5).

Image 5: Major LGG Components

Topics of Interest for the High School Science Curriculum

PZTPZT

BarrelBarrel

Roughing PumpRoughing Pump

Laser FanLaser Fan

Target Chamber

Firing Chamber


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Safety:The LGG works on the same principle as a paint ball gun; they both

use high pressure which can pose a danger. The CO2 canister used to charge

the paint ball gun can become a rocket if the valve is not in the proper

position! Loading the LGG can be dangerous; one must be sure the gun is not

under pressure when trying to load the projectile (see images 6 and 7 on the

next page).

Gas Laws: Since the LGG operates via changes in pressure this is an

excellent way to introduce the Ideal Gas Law: PV=nRT where P = pressure; V

= volume; n = no. of moles; R = universal gas constant (8.3145 J/mol K), and

T = temperature in Kelvin. Visit this website for further explanations about

Gas Laws:

http://www.hgs.k12.va.us/Physics/PowerPoint_Slides/PHY%20chp10_files/fram

e.htm.

Image 6: The CO2 canister that is used to charge the paint ball gun canbecome a dangerous projectile. The brass or nickel-plated valve must remainconnected to the CO2 canister when removed from the gun.
http://www.hgs.k12.va.us/Physics/PowerPoint_Slides/PHY%20chp10_files/frame.htmhttp://www.hgs.k12.va.us/Physics/PowerPoint_Slides/PHY%20chp10_files/frame.htmhttp://www.hgs.k12.va.us/Physics/PowerPoint_Slides/PHY%20chp10_files/frame.htmhttp://www.hgs.k12.va.us/Physics/PowerPoint_Slides/PHY%20chp10_files/frame.htm


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Image 7: One must make sure the LLG is not under pressure when trying to

load the projectile into the firing chamber.

Optics:The laser fans found in the LGG can be used to introduce students to

refraction, diverging lens, converging lens (see Image 8), and the lens

equation. The web site at

http://www.glenbrook.k12.il.us/gbssci/phys/Class/refrn/refrntoc.html provides

a tutorial and sample problems dealing with optics. This site

http://www.pageout.net/user/www/s/t/steverapp/Lab%2022.1.htm has a lab

activity involving real images and virtual images.

Firing Chamber
http://www.glenbrook.k12.il.us/gbssci/phys/Class/refrn/refrntoc.htmlhttp://www.pageout.net/user/www/s/t/steverapp/Lab%2022.1.htmhttp://www.glenbrook.k12.il.us/gbssci/phys/Class/refrn/refrntoc.htmlhttp://www.pageout.net/user/www/s/t/steverapp/Lab%2022.1.htm


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Image 8: Left, a converging lens; Right a diverging lens

Projectile Speed: In the LGG, speed of the projectile can be determined

since the laser fans can be used to help determine the time it takes for the

projectile to travel a certain distance. Students can be introduced to the

equation d = v/t. Problems calculating speed of an automobile would be

appropriate for high school students. The

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/vectors/u3l2d.html

website has an excellent tutorial with sample problems.

Kinetic Energy: Kinetic Energy can be calculated since the mass and speed

of the projectile is known. K.E. = mv2 can be introduced to students (see

Image 9). A tutorial and problems on K.E. can be found at this site:

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/energy/u5l1c.html . A lab
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/vectors/u3l2d.htmlhttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/energy/u5l1c.htmlhttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/vectors/u3l2d.htmlhttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/energy/u5l1c.html


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activity is at this site:

http://steverapp.pageout.net/user/www/s/t/steverapp/Lab%206.1.htm .

Image 9: Projectile is in motion as it moves toward the target and thereforehas Kinetic Energy.

Momentum: Momentum = mass x speed or P = mv; Momentum is a vector

quantity with magnitude and direction. When projectiles strike the target

they have momentum and create craters in the piece of stainless steel

shown in Image 10. The following

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/momentum/u4l1a.html

website has sample problems and a tutorial. A lab activity can be found at:

http://steverapp.pageout.net/user/www/s/t/steverapp/Lab%206.1.htm .

Projectile
http://steverapp.pageout.net/user/www/s/t/steverapp/Lab%206.1.htmhttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/momentum/u4l1a.htmlhttp://steverapp.pageout.net/user/www/s/t/steverapp/Lab%206.1.htmhttp://steverapp.pageout.net/user/www/s/t/steverapp/Lab%206.1.htmhttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/momentum/u4l1a.htmlhttp://steverapp.pageout.net/user/www/s/t/steverapp/Lab%206.1.htm


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Image 10: Projectiles create craters in stainless steel plate; Projectiles have

Momentum.

Newtons Third Law of Motion: During firing of the projectile Newtons

Third Law is illustrated; for every action there is an equal and opposite

reaction. See this site for a tutorial, sample problems and a quiz:

http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l4a.html .

Check out this site for a lab:

http://www.pageout.net/user/www/s/t/steverapp/Lab%204.2.pdf. Image 11

shows a schematic of the LGG firing a projectile.
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l4a.htmlhttp://www.pageout.net/user/www/s/t/steverapp/Lab%204.2.pdfhttp://www.glenbrook.k12.il.us/GBSSCI/PHYS/CLASS/newtlaws/u2l4a.htmlhttp://www.pageout.net/user/www/s/t/steverapp/Lab%204.2.pdf


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Image 11: Schematic of LGG

Conclusion:The Baylor LGG is being used to study the effects of

hypervelocity and low velocity impacts on various space materials used for

the shielding of spacecraft. The hope is that a network of sensors can be

developed to alert astronauts to any impacts that may cause damage to the

outer skin of their spacecraft. The plan is to use this sensor network in the

skin of the new Orion spacecraft. In this study many applications can be

utilized in the high school science curriculum, especially in physics.


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References

[1] European Space Agency. (2005, April). What are hypervelocity impacts?

Technical and Quality Management Portal. Available:

http://www.esa.int/techresources/ESTEC-Article-fullArticle_par-

28_1112600510257.html.

[2] Wright, David. (2007, October). Space Debris. Physics Today.

[3] C. A. Belk, J. H. Robinson, M. B. Alexander, W. J. Cooke, and S. D. Pavelitz.

(1997, August). Meteoroids and Orbital Debris: Effects on Spacecraft.

NASA Reference Publication 1408. Available: http://www.knowledgenetwork.

ca/space/articles/meteoroids.pdf
http://www.esa.int/techresources/ESTEC-Article-fullArticle_par-28_1112600510257.htmlhttp://www.esa.int/techresources/ESTEC-Article-fullArticle_par-28_1112600510257.htmlhttp://www.esa.int/techresources/ESTEC-Article-fullArticle_par-28_1112600510257.htmlhttp://www.esa.int/techresources/ESTEC-Article-fullArticle_par-28_1112600510257.html

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Applications of the LIght Gas Gun in the High School Science Curriculum