Introduction ofSmall Solar Power Sail
Demonstrator“IKAROS”

IKAROS
IKAROS Demonstration
Demonstration TeamTeam
JAXA
JAXA SpaceSpace Exploration
Exploration Center
Center (JSPEC)(JSPEC)
Japan
Japan Aerospace
Aerospace Exploration
Exploration Agency
Agency (JAXA)(JAXA)

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Overview of IKAROSIKAROS is a space yacht that gathers energy for propulsion from sunlight pressure by means of a membrane(or a solar sail.) The mission aims at verifying navigation technology using a solar sail for first time in the world.
A solar sail can move forward without consuming propellant as long as it can generate enough energy fromsunlight. This idea of a solar sail was born some 100 years ago, as we often find it in science fiction novels, but
it has not been realized to date. In that sense, if we can verify this navigation technology through the IKAROS it
will mark the first spectacular achievement of its kind in the world.
In addition to the solar sail technology, the IKAROS will also verify power generation from thin film solar cells
attached on the membrane in addition to acceleration by solar radiation. Therefore, the demonstrator is named“Solar Power Sail” and is not just a solar sail mission.
A solar sail is technology that can generate propulsion in space without propellant as long as sunlight exists. In
the case of a solar power sail, it can gain the necessary electric power using a vast area of thin film solar cellson the membrane even when the demonstrator is away from the sun. The IKAROS is, therefore, an ambitious
mission to verify the above two technologies together which are essential for us to explore deep space.
The IKAROS is a spin-type explorer, thus it will deploy its square membrane 14 meters to the side (or 20meters across) using the centrifugal force in space. After its deployment, we will evaluate the performance ofthe power generation by the thin film solar cell on the membrane, then perform experiments by navigating deep
space through sunlight pressure power. The solar sail used for the IKAROS is made of polyimide resin
deposited with aluminum. It is very thin, only 7.5μm (about 1/10 of a human hair.) On top of this thin sail,various devices are equipped, including the thin film solar cells, a liquid crystal device that controls attitude bychanging light reflection characteristics, a temperature sensor, and a dust counter.
Through the technologies verified by the IKAROS, we can transport larger volumes to deep space and generate
more power there. We would like to realize an explorer that can travel to the sphere of Jupiter by combining
solar sail technology and a high-performance ion engine to become a pioneer in the age of solar system
voyages of discovery.

IKAROS = Interplanetary Kite-craft Accelerated by Radiation Of the Sun2What is a Solar Power Sail?
A Solar Sail is a space yacht that gathers sunlight for propulsion by means of a deployedlarge membrane (sail) in space. It is like a yacht that sails by gathering wind. This idea wasborn some 100 years ago, but it has not been realized as it requires a thin film mirror that isextremely light and strong enough to hold a vast area.
A Solar Power Sail is a Japanese original concept that combines solar sail propulsion andelectricity generation from thin film solar cells attached on the membrane. IKAROS will verify
the concept. In the future, we aim to further elaborate this technology to a hybrid propulsion
system with a solar sail by activating the high-performance ion engines with the power
generated by the solar power sail.

Super thin membranesolar sail

Image of solar sail(The Planetary Society)

Thins film solarcells
Small Solar Power Sail
Demonstrator “IKAROS”

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IKAROS Characteristics
Orbit from Earth toVenus
Venus
in '10<Major Characteristics>
Scheduled launch day:

1.5 108

May 18, 2010 from the Tanegashima Space CenterEarthEarth1 108

Launch Vehicle:

H-IIA

Venus Arrival 12/12/'10
7Diam. 1.6 m x Height 0.8 m (Cylinder shape)

Membrane:

Square of side 14 m and cross section 20 m (afterdeployment)

Launchtime mass:

310 kg *Including membrane mass

Dry mass:

290 kgMembranemass:

15 kg *Including 2 kg of 4 tip masses

5 100SunSun-5 107-1 108

Venus

Venus
-1.5 108

E Departure 6/14/'10
IKAROS

Orbit:

Venus transfer orbit

Attitude control system:

Spin-2 108-1.5 108 -1 108-5 10705 107

xsc

φ1.6m

1 108

1.5 108

2 108

TetherThin film solar cells
IKAROSmain bodySolarsailφ20m

MassBody:

0.8m

Configuration

Tip mass4IKAROS Mission
Minimum success:Deployment of the large membrane and power generation by the thinfilm solar cells. → If we succeed with the above, it will be a global first!
Full success:Acceleration verification and navigation technology acquisition by thesolar sail. →Verification of solar sail acceleration and navigation itself
will be the first in the world!!

Venus

Full success(in six months)
Minimum success
Earth5) Orbit control and navigation
technology using solar sail(in a few weeks)4) Acceleration experiment bysolar sail1) H-IIA LaunchSun-pointing
Spin separation (5 rpm)

3) Membrane deployment experiment
Spinning-down (1-2 rpm)
Solar power generation by thin film solar cells2) Radio telemetry ON
Initial operation check
Spinning-up (20 rpm) and deployment start5

IKAROS Membrane
13Tip mass: A 0.5 kg weight supports thedeployment of the membrane.

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Dust counter: Space dust counter using
piezoelectric elements.

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Tether: Connecting the main
body and the membrane.
Thin film solar cells: Amorphous silicon cell of
25μm in thickness.

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Liquid crystal device: Controlling attitude by changing
reflection ratio. (In addition to the above, an electric charge-

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measuring patch and a thermometer are equipped.)1313

Membrane:7.5μm in thickness made of polyimide resin deposited with aluminum and speciallyprocessed with reinforcement to prevent cracks.
(1/4 of the squaremembrane)(1/4 of the squaremembrane)

Front side
(Facing tothe sun)Back side(Not facing tothe sun)

6Membrane Deployment Sequence and Mechanism
Tip mass separation
Separationfrom launchvehicle

5rpm

2rpm

Tip mass

Spin down

Activate the tip mass separation
mechanism to separate all four tip
masses at the same time.

First stage deployment (quasi static): About one hour
As it deploys, the spin rate will dwindle.

25rpm～15rpm5～6rpmStopper(rotation guide)

To spin up to 25 rpm, and start the first stage deployment byactivating the stopper (rotation guide) that holds the membrane
through the relative rotation mechanism (motor drive).

The membrane will slowly andgradually deploy through centrifugal
force as the relative rotation
mechanism activates.

Completion of
the first stagedeployment.

Second stage deployment (dynamic): About five seconds, or about 100
seconds until vibration settles down.
1～2rpmAs the membrane is released,
it will deploy dynamically.

Activate the stopper (rotation guide) andrelease the hold of the membrane tostart the second stage deployment.

Completionof the secondstagedeployment.

7Orbit and Attitude Control by SunlightWith a solar sail, orbit control is possible without using propellant. Orbit control requires to change theangle (facing direction) of the membrane to the sun. By shifting the attitude of the orbiter’s main bodythrough thruster jets, we will change the attitude of the membrane.
*IKAROS uses a gas-liquid equilibrium thruster.

Theory of orbit control
Changed orbit

To go away from the sun

Original orbit

To go closer to the sun

Original orbit
Sunlight power received by
the solar sailChanged orbit

Sunlight
Solar Sail

Solar Sail

Sunlight power received
by the solar sailSunlight

Other engineering and science missions
The following engineering and scientific missions are also scheduled to be conducted by the IKAROS
mission in addition to the solar power sail deployment, thin film solar cell power generation, and solar
sail acceleration and navigation verification.
Engineering mission◆Attitude control device (Liquid crystal device
experiment) : Attitude control test using a liquid
crystal device whose reflection characteristics change
by turning on electric power.
VLBI-Tx and LGA◆VLBI experiment : High accuracy
orbit determination test by the VeryLong Baseline Interferometer

Liquid device ON

Liquid device OFFScience Mission◆ALDN (Dust counter):Dust distribution will be observed by a dust
counter using PVDF (PolyVinylidene DiFluoride)◆GAP:
Gamma-ray burst observation experiment by apolarized light detector
GAP detector

ALDN sensor

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