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Journal of Interdisciplinary Science Topics

Calculating the Power Output of Qui-Gon Jinn’s Lightsaber

Luke Willcocks

The Centre for Interdisciplinary Science, University of Leicester

20/03/2017

Abstract

This paper gives a summary of the power output of the standard green lightsaber wielded by Qui-Gon Jinn

in Star Wars Episode 1: The Phantom Menace. The power output of a lightsaber was found to be 6.96MW,

which dwarfs the output of common construction tools. This power is only two orders of magnitude smaller

than that produced by small nuclear generators, showing that lightsabers are effective weapons.

Introduction

The lightsaber is the iconic weapon of the Jedi Knights

and Sith Lords of the Star Wars universe. The Star

Wars films portray the lightsabers as weapons that

can effortlessly cut through different materials. This

paper will discuss the power output of Qui-Gon Jinn’s

lightsaber, based on a scene in Episode 1 – The

Phantom Menace (apologies to all Star Wars fans that

a prequel film is being used for this model).

Figure 1 - Qui-Gon Jinn cutting through a

metal blast door in the Phantom Menace [1].

The calculations themselves are similar to work done

on a blog post which will be referred to and cited

throughout the paper; however, the accuracy of

these calculations and subsequent conclusions will be

scrutinised.

Application

In the scene in question, when trying to reach the

bridge of the droid battleship, Qui-Gon attempts to

melt a hole in a blast door which blocks his route [2].

The lightsaber successfully melts through door, as can

be seen from the molten metal oozing from the cut in

Figure 1. The energy output of the lightsaber can be

calculated using the equation for heat energy:

=( )++ (1)

This equation relates the heat energy, , to the mass

of material melted, , and the change in

temperature from initial, , to melting point, ,

and from melting point to final temperature, .

Therefore, in order to calculate the energy produced

by the lightsaber the temperature and mass must be

estimated. Rhett Allain used the colour of the metal

to estimate the temperature it reached [3]. He

estimates the temperature to be 5200K (red arrow,

Figure 1) – this is 500K less than the Sun’s surface

temperature, which seems too hot to be reasonable

as this temperature could potentially melt the hilt of

the lightsaber. He also estimated the unmelted metal

temperature to be 2700K (blue arrow, Figure 1), but

it appears that he has estimated the 2700K from the

melted metal that has oozed out of the cut rather

than the unmelted door. Therefore, this is used as the

estimate for final temperature as it is the more

accurate estimate for the temperature of the melted

metal.

The melting point, mass, and associated constants

are all dependant on the metal the door is made of.

In the blog [3], they fabricate a metal because the

Star Wars universe uses metals which are fictional. As

the metal is crucial to the equation, fabricating a

metal will tell little about the lightsaber itself. As this

is occurring on a battleship it is reasonable to assume

that the fictional metal used is Doonium [4] - a heavy

Calculating the Power Output of Qui-Gon Jinn’s Lightsaber, March 20th 2017

grey metal commonly used in battleship construction

in the Star Wars universe. Comparing this to common

Earth metals, it is reasonable to assume that

Doonium is similar to titanium or aluminium, which

are both used in construction in reality. Aluminium

would be used in the calculations if the metal being

melted was on the outer hull. Aluminium is

commonly used in real spacecraft for its ability to

withstand take-off stress as well as being lightweight.

Titanium was used for these calculations as the door

shown in Figure 1 is a heavy blast door designed to

withstand blaster attacks, and thus requires a

tougher construction metal.

The mass of titanium melted in the door can be found

to be the product of the volume and density of the

material. The density of titanium is commonly known

to be approximately 4506kg.m-3 [5]. The volume of

the metal melted is in the shape of a half ring; Figure

2 shows the cross sectional area of the half ring.

Figure 2 - The cross sectional area of the half

ring cut out of the door.

The volume of the melted metal can be calculated

using Equation 2:

= () × =

2

2× (2)

Where depth () is the width of the door, and A is the

cross sectional area of the half ring, as shown by

Figure 2. This area is the difference in area between

two semicircles with radii and respectively (Figure

2). Using the film clip, the width of the door was

assumed to be 0.15m [2]. Estimating that the hole

Qui-Gon is cutting has diameter 1m, this means that

is 0.5m. Since the width of a standard lightsaber is

approximately 0.04m [6], the distance between the

inner edges of the hole is 0.92m, and therefore is

equal to 0.46m. Therefore, substituting these values

into Equation 2 gives a volume of 9.05×10-3 m3. Using

this volume and the density (4506 kg.m-3), the mass

of titanium melted in the scene is shown in Equation

3.

= =40.77 (3)

Assuming the door is initially at room temperature,

then the variables are as shown below:

(K)

(K)

(K)

(kg)

298

1941

2700

40.77

(J.kg-1.K-1)

(J.kg-1.K-1)

(J.kg-1)

523

790

419000

Table 1 - Showing, from left to right and up

to down; Initial temperature, melting point,

final temperature, mass, solid specific heat

capacity [5], liquid specific heat capacity [7]

and latent heat of fusion [8].

Substituting the values from Table 1 directly into

Equation 1, the heat energy is found to be 76.56MJ.

The power output of the lightsaber is the ratio of this

heat energy to the time it takes to melt through the

metal. Allowing for continuity errors in filming it was

estimated from the clip [2], that Qui-Gon took 11s to

melt through the blast door, therefore:

=

= 76.56

11= 6.96 (4)

This means that the power of the standard green

lightsaber that Qui-Gon uses is 6.96MW. This is a

large power output for a small tool compared to

mundane tools; for example, a circular saw requires

just 2kW to start [9]. Small nuclear generators have a

power output of 500MW [10]; this is only two orders

of magnitude greater than the power of a lightsaber.

This suggests the lightsaber has an efficient power

source in the fictional Star Wars Universe in

comparison to real world power sources, as it

produces an exceptionally large amount of power

from a comparatively small source.

Conclusion

The lightsaber is a highly efficient weapon in the Star

Wars Universe, with a power output of 6.96MW. This

dwarfs the power output of common construction

tools, and is only two orders of magnitude smaller

than the power output of small nuclear power

generators. This high power output means that there

is a lot of energy being pumped into the material in a

short space of time. This high output from such a

small source is what makes the lightsaber such an

efficient tool for cutting through dense materials and

battling droids.

Calculating the Power Output of Qui-Gon Jinn’s Lightsaber, March 20th 2017

References

[1] StarWarsAnon (2014) Scene it on Friday - TPM Scene #8. wirdpress.com, 21 February 2014. [Online].

Available: https://starwarsanon.wordpress.com/tag/blast-door/. [Accessed 10 February 2017].

[2] Zuniga, M. (2015) Jedi vs Trade Federation Droids - The Phantom Menace, Youtube, 11 January 2015.

[Online]. Available: https://www.youtube.com/watch?v=pUbXyd-fK8Q. [Accessed 10 February 2017].

[3] Allain, R. (2010) Power Source of a lightsaber, Science Blogs, 2 February 2010. [Online]. Available:

http://scienceblogs.com/dotphysics/2010/02/02/power-source-for-a-lightsaber/. [Accessed 10

February 2017].

[4] Jedipedia (2015) Doonium, 23 November 2015. [Online]. Available:

https://www.jedipedia.net/wiki/Doonium. [Accessed 10 February 2017].

[5] Haynes, W. M. (2016) Handbook of Chemistry and Physics, CRC.

[6] Wikipedia (2014) Lightsaber, 12 June 2014. [Online]. Available:

https://en.wikipedia.org/wiki/Lightsaber. [Accessed 10 February 2017].

[7] The Engineering Toolbox (2015) Metals - as Liquids, 12 June 2015. [Online]. Available:

http://www.engineeringtoolbox.com/liquid-metal-boiling-points-specific-heat-d_1893.html. [Accessed

10 February 2017].

[8] The Engineering Toolbox (2015) Metals - Latent Heat of Fusion, 12 June 2015. [Online]. Available:

http://www.engineeringtoolbox.com/fusion-heat-metals-d_1266.html. [Accessed 10 February 2017].

[9] Diesel Servicing and Supply (2015) Power Consumption Chart, 20 March 2015. [Online]. Available:

http://www.dieselserviceandsupply.com/Power_Consumption_Chart.aspx. [Accessed 17 February

2017].

[10] American Geosciences Institute (2016) How much electricity does a typical nuclear power plant

generate, 1 December 2016. [Online]. Available: https://www.americangeosciences.org/critical-

issues/faq/how-much-electricity-does-typical-nuclear-power-plant-generate. [Accessed 17 February

2017].