Space Sports – Sailing in Space
Maria Sundin
, Lars Larsson
and Christian Finnsgård
Centre for Sports Technology, Chalmers University of Technology, Gothenburg, Sweden
Dept. of Physics, University of Gothenburg, Gothenburg, Sweden
Dept. of Shipping and Marine Technology, Chalmers University of Technology, Gothenburg, Sweden
SSPA Sweden AB, Research, Gothenburg, Sweden
Keywords: Space, Titan, Sports, Sailing, Hydrodynamics.
Abstract: Titan is the largest moon of Saturn, and apart from the Earth it is the only body in our solar system where a
liquid exists on the surface. Within the last ten years a system of lakes and rivers have been discovered. The
climate and seasonal cycles of Titan are still not very well known, but the composition and pressure are fairly
well established. Perhaps in the future boats will sail the lakes of Titan for research purposes or even sport.
The purpose of this paper is to give an overview of the concept of space sports, the conditions of Titan and to
calculate important parameters of sailing such as floatability, stability, hull resistance and sail forces. This
paper shows that if a sailing yacht on Titan will have twice as large displacement as on Earth, it will be 2.6
times less stable for the same beam. Since friction will be smaller, it will be faster than on Earth at low speed,
but significantly slower at high speeds due to the wave generation. The same sail area is required to get the
same sail forces if the average wind is 3 m/s, while a 9 times larger sail area is required for if the wind speed
is only 1 m/s.
Today the International Space Station has been
manned since the year 2000. Serious plans of sending
humans to Mars in the near future exist. The
European Space Agency is discussing having a
manned base on the Moon by 2030. Perhaps humanity
one day will colonize a large part of our solar system.
The idea of sports then being practiced in space is
probably not too strange. Space Sports would be
performed under very different conditions than Earth
Sports, and completely new possibilities would arise.
Sports research indicate new records being harder
and harder to obtain in some sports. Possibly, the
limits of human capability for certain sports will soon
be reached. But, one could argue, only on this planet!
On other planets it might be possible to jump higher
and patterns of locomotion and the motion of objects
will differ. Earth Sports could be adapted and new
sports could be created. Could interplanetary
championships exist? Could an athlete from Earth
compete against an athlete from Mars? How, and on
which planet in that case?
There are a large number of sports that could be
investigated using physics and technology. How high
could a horse jump on Mars? Can you sail on the lakes
of Titan, the largest moon of Saturn? How large
would a goal in soccer have to be on the moon? Can
you fly using muscular power on Pluto? What is the
pattern of locomotion when running in a different
gravity? Is The Jovian moon Europa the perfect place
for skating? How do you play ball in zero gravity?
Can you ski on Olympus Mons, the highest mountain
in the solar system?
The number of possible questions about space
sports are almost endless. This paper introduces one
concept study of space sports by looking at sailing on
Our sun is a medium sized yellow star, one of the
approximately 200 billion stars in the Milky Way
galaxy. Around the sun there are eight planets and
minor bodies such as dwarf planets, moons, asteroids
and comets.
The planets are usually divided into two separate
categories; terrestrial planets and gas giants. The
terrestrial planets are Mercury, Venus, Earth and
Mars in order from the sun and outwards. The gas
Sundin, M., Larsson, L. and Finnsgård, C.
Space Sports Sailing in Space.
DOI: 10.5220/0006086701410146
In Proceedings of the 4th International Congress on Sport Sciences Research and Technology Support (icSPORTS 2016), pages 141-146
ISBN: 978-989-758-205-9
2016 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
giants are Jupiter, Saturn, Uranus and Neptune.
Terrestrial planets are substantially smaller than the
gas giants with the diameter of Jupiter being 22 times
larger than the diameter of the Earth. Rocks and
metals are the main constituents of the terrestrial
planets, while the gas giants have large layers of
hydrogen, helium, ices and hydrocarbons in different
states surrounding rocky cores.
The distance between the Earth and the sun is
some 150 million km, and this distance is usually
referred to as 1 Astronomical Unit (1AU). Mars is
located at 1.5 AU, so the four terrestrial planets are
fairly close together when it comes to astronomical
distances. Jupiter is at 5.2 AU from the sun and the
outmost planet Neptune is at 30 AU.
Most of the bodies of the solar system orbit the
sun in the same plane, the only exception being the
large spherical cloud of comets surrounding the
the outskirts of our solar system.
Oceanus Procellarum – Sea of Storms, Mare Crisium
– Sea of Crises, Mare Tranquillitatis – Sea of
Tranquillity and Mare Imbrium – Sea of Rains
The names of the dark areas on the moon are most
likely exciting for any sailor. Indeed, their names
reflect a time when they were mistaken for being
oceans and seas instead of the dry lava plains we now
know them to be. No liquid water can exist on the
surface of the moon primarily due to the absence of
an atmosphere.
Large amounts of liquids on the surface of a
planet or a moon is in fact extremely rare in our solar
system. Titan, the largest moon of Saturn, is probably
the only place excepting our own Earth. The seas,
lakes and rivers of Titan are however not filled with
water but the hydrocarbons methane and ethane in
liquid state.
Since Titan then is the only other body in our solar
system with a liquid on the surface, it is also the only
other place where we could practice sailing. Will we
ever do that, and why in that case?
Most likely the first expeditions to Titan would be
for scientific purposes much like the way we are
exploring Mars today. The exploration of Mars is
partly being done using robotic rovers, and on Titan
robotic boats could be an option. A great advantage
of sailing is it being a form of transport without the
need of extra energy sources. In space exploration,
energy is always one of the limiting and costly
The research on autonomous vehicles on the Earth
is evolving rapidly, and autonomous boats on Titan
would be an enormous advantage since the
communication time between the earth and Titan is
an approximate hour. NASA is currently discussing
the possibility of sending a submarine to Titan.
Of course, the possibility exists of Titan being
colonized in the future. Manned sailing boats could
then become reality and apart from transport perhaps
even sailing could become a recreational pleasure as
well as a sport.
Why then are the Earth and Titan the only bodies
in our solar system with liquids on their surfaces? The
uniqueness of Titan is the conditions being right for
the existence of a relatively thick atmosphere. A
certain atmospheric pressure is necessary for the
existence of liquids instead of having a substance in
solid or gaseous state. The surface pressure on Titan
is larger than on the Earth, and the atmosphere of
Titan consisting mainly of nitrogen.
Our neighbor planet Mars has such a thin
atmosphere that liquid water can hardly exist on the
surface anymore. Large amounts of water are present
on Mars, but almost all the water is in solid state (ice)
with the transition to water vapour being very quick
when heated. The lack of atmosphere on Mars is due
to a weak gravity and no shielding magnetic field.
The solar wind is a stream of electrons and protons
from the sun, and it exerts a pressure on the Martian
atmosphere. On Earth our atmosphere is partly
shielded by our magnetic field. The weak Martian
gravity has not been able to hold on to the originally
much thicker atmosphere when battered by the solar
Jupiter and Saturn are our two largest planets and
they are called gas giants. Both have more than 60
moons each. Several of these moons are exciting
worlds in different sizes and with varied surfaces. A
few of the moons are actually larger than the planet
Mercury. A planet moves around the sun, and a moon
moves around a planet but planets and moons can be
of equal sizes. Titan is the second largest moon in our
solar system, but it is smaller than Mars in both radii
and mass. Why then has Titan not lost its atmosphere
when Mars has? The reason is it being much colder
out by Saturn at 9.5 AU than at Mars at 1.5 AU. The
average temperature on Titan is around -180 degrees.
This will lead to the velocities of the molecules in the
atmosphere not being as high. It is easier for the
gravity to hold on to a cooler gas than a hot one, since
fewer of the molecules reach the escape velocity.
Titan is also shielded from the solar wind by the
magnetic field of Saturn.
Already in the 1980’s the speculations of lakes on
icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support
Titan began triggered by data from the Voyager space
crafts. When the Cassini space craft arrived after a ten
year long journey in 2004 hopes were high of a rapid
detection of the lakes. But it took three more years
until the lakes were finally proved to exist in 2007.
Today we know that the largest lake of Titan Kraken
Mare has a surface of 400 000 square kilometers and
a depth of 160 m. Its surface is probably just a little
bit smaller than the surface area of Sweden and
possibly larger than the Caspian Sea. Titan has
several other lakes and rivers of different sizes and
depths and shows an intriguing landscape. Measure-
ments so far indicate flat lakes and low velocities of
the winds, but modelling of Titans climate shows
possibilities of strong winds and even hurricanes.
This has received support by other studies of the
Saturn orbits the sun with a period of approxima-
tely 29 years. The seasons are therefore some 7 years
each. When Cassini reached Saturn in 2004 the
northern hemisphere of Titan was in deep winter.
Now, twelve years later the northern hemisphere is
approaching the summer solstice. This means that we
have not as yet had the opportunity to study the
climate of Titan during a whole “Titan-year”.
Therefore it is quite uncertain how valid the weather
observations are when it comes to average conditions.
So, what are the possibilities of sailing on Titan, and
how different would it be from sailing on Earth?
Would it be at all possible, and what would the boats
look like? To assess the possibilities we need to
consider aspects like floatability, stability, hull resis-
tance and sail forces. These properties are in turn
dependent on physical constants like the density and
viscosity of the atmosphere and the liquid, and on the
gravity. Wind speed is of course also an important
parameter. In Table 1 the physical constants are lis-
ted, based on data from Cassini. For comparison, the
corresponding values on the Earth are also presented.
Table 1: Physical constants (Hayes et al, 2013).
Constant Titan Earth
Atm. density,
5 1.2
Atm. viscosity,
Liquid density,
530-660 1030
Liquid viscosity,
Acc. of gravity, g [m/s
] 1.4 9.8
Let us start with the floatation, i.e. how deeply the
boat will float in the liquid. The gravity force F
(downwards) is obtained as
= (1)
where m is the total mass of the boat and g is the
acceleration of gravity. The buoyancy force, F
(upwards) is equal to
 (2)
is the liquid density and D is the
submerged volume (displacement) of the hull. This is
according to Archimedes’ principle. At equilibrium
which yields
Since g appears both in F
and F
it disappears
from the final equation, which says that for a given
mass the displacement is inversely proportional to the
fluid density. According to Table 1 the density on
Titan is about half of that on Earth. Therefore the
displacement will be twice as large on Titan as on
Earth for a given mass.
Stability is of fundamental importance for a
sailing yacht. As appears from Figure 1, it is achieved
through the sideward movement to leeward of the
centre of the underwater volume from B to B’ when
the yacht heels (Larsson et al, 2014). Since F
acts at
the centre of buoyancy, it will create a righting
moment with F
. A vertical line along F
will cut the
heeled center plane of the yacht at the metacenter, M.
The distance between this point and the centre of
gravity G is called metacentric height and is denoted
. It follows that the righting arm, RM, can be
computed as 
sin , where is the heel angle, and
that the righting moment, RM, is
 =
sin (5)
To compute the righting moment we need the
metacentric height 
. This can be computed using
the distance from B to M, 
, which is obtained from
a fundamental formula in stability theory (Larsson et
al, 2014)
where I is the moment of inertia around a
longitudinal axis of the area inside the waterline of
the hull.
For a sailing yacht, B and G are close together and
and 
are approximately equal. With this
approximation, and using (1) for the gravity, the
righting moment is
 =  sin / (7)
Space Sports Sailing in Space
Figure 1: Stability principle.
For a given mass and heel angle the righting
moment is thus proportional to g and I/D. As seen in
Table 1, the gravity on Titan is seven times smaller
than that on Earth, so for the same stability I/D has to
be 7 times larger. Now, for a given length, the inertia
I is proportional to beam cubed, while the
displacement D is proportional to beam to the first
power. It the follows that I/D is proportional to beam
to the second power. For I/D to be 7 times larger than
on Earth beam has to be increased
times, i.e.
about 2.6 times.
A hull with the same length as on Earth, but twice
as beamy would satisfy the displacement criterion
above but it would be less stable. To remedy this, the
hull could be longer and it could carry more ballast.
The main parameter of interest may be the payload
the yacht can carry. For a given displacement this
depends on the weight of the yacht itself. The heavier
the yacht, the smaller the payload. The weight
increases with beam, but much more so with length.
So from this point of view it is better to make the hull
wider. This will however increase resistance, as we
will see. Another very interesting possibility is to use
a catamaran. Then stability is no problem and the
resistance low.
Having considered the most important properties,
floatability and stability, we now turn to the speed
potential of the yacht. This is determined by the
driving forces on the sails and the resistance of the
submerged part of the yacht. Let us start with the
There are two main components of resistance for
a body moving along the surface of a liquid: friction
and wave resistance. The former occurs because of
the internal friction in the fluid, its viscosity, while
the latter is caused by the generation of waves
transmitted from the body.
Similarity laws for scaling resistance (Larsson
and Raven, 2010) show that friction, R
, may be
computed as
is a friction coefficient, the fluid
density U the fluid velocity and S the wetted surface
of the body.
is determined by the Reynolds
where L is a characteristic length of the body and
ν the kinematic viscosity of the fluid.
Table 1 gives a range of possible viscosities for
the liquid on Titan. The range is however centered
around the value on Earth (10
/s). Since the
dependence of
is essentially logarithmic
(Larsson and Raven, 2010) it is enough for the present
discussion to note that the order of magnitude is the
same for the liquid viscosity on Titan and Earth. We
can thus assume the same C
. For a given speed,
friction is then proportional to . As we have seen
the density on Titan is half of that on Earth, but the
wetted surface is larger if the hull is made twice as
wide. However, not so much that it compensates for
the lower density. Friction may thus be assumed
somewhat smaller on Titan.
As shown in Larsson and Raven (2010) the wave
resistance is governed by the Froude number, F
 (10)
Neglecting some higher order effects, a constant
Froude number will imply the same wave pattern
(scaled with length) and the same wave resistance
coefficient, C
, regardless of the speed, length and
gravity. The wave resistance, R
is obtained from the
coefficient in the same way as the friction in equation
Unlike C
, C
will not be the same as on Earth.
This is for two reasons. A wider hull will give a larger
, and, more importantly, a given speed will give a
higher Froude number on Titan, thereby increasing
. The first effect can be roughly estimated as
proportional to beam, i.e. for double beam a twofold
increase for a given Froude number. But the second
effect is difficult to estimate. The relation between C
and F
. is very nonlinear, and also dependent on the
hull shape. For most standard yachts there is a
maximum Froude number around 0.45, where the
wave resistance gets so large that the driving force
icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support
from the sails is insufficient for increasing the speed.
This limit will now occur at
times smaller speed
than on Earth, due to the 7 times smaller gravity (see
Equation 10). In fact the whole wave resistance/speed
curve will be compressed in the speed direction by a
At low speeds friction dominates over wave
resistance and, as seen above, the speed may then be
somewhat larger on Titan, but at higher speeds the
total resistance depends mainly on the wave
resistance, and then the speed will be considerably
smaller due to the Froude number effect.
Finally, let us look at the sail forces. The sail is a
wing which generates a force with components in the
direction of motion, F
and at right angles to that, F
Both can be obtained in a similar way as R
and R
where C
and C
are coefficients
the density of
the atmosphere, V the wind speed and S
the sail area.
Like for the liquid, the coefficients depend on the
Reynolds number
where C is the mean chord of the sail and
is the
kinematic viscosity of the atmosphere.
The wind speed on Titan is not well known. There
are indications of occasional hurricanes, but the
normal wind speed should be quite low. According to
Habib (2015) the average speed is estimated to about
3 m/s. Other sources quote lower speeds, around 1
m/s (Hayes et al., 2013, Bird et al 2005). On Earth the
average wind speed is 6.6 m/s (Habib, 2015).
Let us first assume a wind speed of 3 m/s. As seen
in Table 1, the atmospheric viscosity on Titan is about
1/10 of the viscosity on Earth, so the Reynolds
number according to equation (14) is about five times
larger for a given sail. This yields a slightly lower
friction coefficient on the sails, but this will have a
very small effect on the forces, which are almost
exclusively caused by pressure differences between
the two sides of the sail. We can thus assume that both
and C
are the same on Titan and Earth for a given
sail. Equations (12) and (13) then show that the forces
are proportional to
. Table 1 shows that the
atmospheric density on Titan is about four times that
on Earth, but on the other hand, the wind speed is only
about half in our assumption. So
turns out to be
the same! The sail forces will thus be unchanged.
The other scenario with an average wind speed of
1 m/s will yield 9 times smaller forces! To get the
same sail forces on Titan as on Earth the sail area has
to increase 9 times!
A factor speaking in favour of the lower wind
speed is that no waves have been observed on the
lakes of Titan. This may however be a matter of
measurement accuracy (Hayes et al., 2013). If the
wind speed is only 1 m/s very small waves will be
generated and they will not influence performance.
However, if the speed is 3 m/s the waves could be
significantly larger than the average on Earth. This is
due to the fact that the forcing of the waves, pressure
variation in the atmosphere, is the same, as we have
seen, but the gravity and density of the fluid lower.
Such large waves will slow down a sailing yacht
considerably, at least sailing upwind.
Titan is the largest moon of Saturn, and apart from the
Earth it is the only body in our solar system where a
liquid exists on the surface. Within the last ten years
a system of lakes and rivers have been discovered.
The climate and seasonal cycles of Titan are still not
very well known, but the composition and pressure
are fairly well established. Perhaps in the future boats
will sail the lakes of Titan for research purposes or
even sport. This paper addressed some of the issues
that will have to be considered before sailing on
Titan, or even designing a boat for sailing on Titans
lakes. A sailing yacht on Titan will have twice as
large displacement as on Earth, it will be 2.6 times
less stable for the same beam. Since friction will be
smaller, it will be faster than on Earth at low speed,
but significantly slower at high speeds due to the
wave generation. The same sail area is required to get
the same sail forces if the average wind is 3 m/s, while
a 9 times larger sail area is required for if the wind
speed is only 1 m/s. To avoid the stability problem a
catamaran seems to be a good choice!
The authors wish to acknowledge the support from
Chalmers Area of Advance Materials Science, and
the Department of Physics of University of
Gothenburg. And Västra Götalandsregionen via
Regionutvecklingsnämnden for its financial support.
Bird. M.K et al, (2005). The Vertical Profile of Winds on
Titan. Nature 438, pp.800-802
Space Sports Sailing in Space
Habib, M., (2015). Let’s Put a Sailboat on Titan,
Hayes, A. G. et al, (2013). Wind driven capillary-gravity
waves on Titan’s lakes: Hard to detect or non-existent?
Icarus 225, pp. 403-412.
Larsson, L., Eliasson, R.E., Orych, M., (2014). Principles
of Yacht Design. Adlard Coles Ltd, London
Larsson, L., Raven, H.C., (2010). Ship Resistance and
Flow, PNA Series, Society of Naval Architects and
Marine Engineers, Jersey City, USA.
icSPORTS 2016 - 4th International Congress on Sport Sciences Research and Technology Support