ppt by kanav mansotra

1. SEMINAR ON
“SOLAR SAIL”
kanav Mansotra

2. CONTENTS
• Introduction
• Introductory video
• Physical principles
• Attitude control
• Sail configurations
• Sail making
• Conclusion

3. INTRODUCTION
Solar sails are also called light sail or
photon sail
Use radiation pressure for propulsion
Radiation pressure :- pressure excreted
by electromagnetic radiation
Can be used many times as they have
minimum moving parts
Total force excreted is around 1 Newton
making low thrust spacecraft

4. LET’S SEE AN INTRODUCTORY
VIDEO

5. PHYSICAL PRINCIPLES
Solar radiation pressure
 Pressure on the sail due to reflection and small fraction is absorbed.
 Momentum of a photon is given by Einstein’s equation as p= E/c
where p  momentum, E  photon , c  speed of light
 Perfect sail perfect absorbance F= 4.54 μN/m2 , perfect reflectance
F=9.08μN/m2 and 100% specular reflectance.
 Due to wrinkles , absorbance ,curvature ,normal sail will have efficiency of
90%.
 Force on a sail is given by F = F0 cos2 θ / R2 (ideal sail)
θ angle bw sail force vector and radial from sun.
R distance from sun in AU.
 But for an actual sail ,force is F = F0 (0.349 + 0.662 cos 2θ − 0.011 cos 4θ) / R2
 Force and acceleration approach zero as θ nears 60o .

6. Attitude control
 Attitude  behavior of craft towards various force acting on it .
 It is maintained by ATTITUDE CONTROL UNIT (ACS) .
 Control is by changing crafts centre of pressure and centre of mass.
 achieved with control vanes, moments of individual sail etc.
 Along trajectory :- total force and torque changes.
 Sail temperature also changes with solar distance.
 ACS must be able support these changes.

7. Constraints
 Testing on earth is carried out at an altitude of 800km.
 Only at this height does solar pressure and drag pressure are typically equal.
Applications
 Solar sails can be used in space ships for both manned and unmanned
voyages
(statite) .
 Solar sails can be used in satellites for trajectory corrections .
 thereby saving large amount of propellants.
 statite can go closer to sun ( up to distance were radiation pressure is
equal to gravity) .

8. Sail configurations
 Many sail configurations have been proposed like
 parachutes ; failed as it tends to collapse due to absence of rigid structure
.
 square type.
 disk sail.

 In most cases angular momentum is used to stiffen the structures.
thereby eliminating the need for struts.
 In all cases , large amount of tensile stress is needed.
 weaker sails would ripple and cause structural damage .

9.  Latest developments include the use of electric and magnetic fields for
propulsion.
 Electric solar wind sail
electric solar wind sail use electric field generated by electrically
charged wires to deflect solar electron in light rays.
electric field is generated by straightened conducting wires placed
around the craft.
 Magnetic sail
 magnetic sail use magnetic field to deflect electrically charged
particles.
 in both sails , maneuvering is achieved by changing the size and
shape of their respective fields.

10. Sail making
 Sails have been developed from many materials .
 Drexler developed a solar sail with thin aluminum film of .1mm
thickness.
 The most common material used is aluminized 2µm kapton film.
 Solar sails made from alumina , carbon fiber , is found to be superior to
aluminum, or kapton films.
 New carbon fiber material is over 200 times thicker than conventional
solar ail but has the same mass.
 Lithium can also be used for sail making.
 In all cases , sail should be manufactured in space to avoid tearing during
folding and deployment and to reduce weight.

11.  Sails are mostly fabricated using vapor deposition and molecular
manufacturing techniques.
 Magnesium and beryllium can also be used for sail making.
 Reflection of light is preferred over absorption.
absorption exerts a force directed straight from sun which is not
useful for high performance sails.
absorption raises the equilibrium temperature in proportion to the
fourth rot of its absorptivity.

12. Projects operating or completed
 Until 2010, no solar sails had been successfully deployed in space as
primary propulsion system.
 In may 2010, Japanese space agency (JAXA) successfully launched
IKAROS .
 IKAROS (Inter - planetary Kite – craft Accelerated by Radiation of Sun)
has a polyimide sheet of 200 m2
is diagonal spinning square sail 20m.

15. Conclusion
Though concept solar sail has developed for
many years , it is still in its infancy stage .

16. Reference
Wikipedia
space.com
seminarsonly.com

17. THANK YOU