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