Sailing Across the Cosmos: Unlocking the Power of Solar Sail

Abstract

 

The most feasible and affordable propulsion method, the solar sailing, manifesting remarkable contribution in this modern era in the field of space exploration. Although this spacecraft propulsion method has some limitations it increases interest due to its potential applications in space exploration. There are several mathematical models to track this propulsion technic. In this content, the ‘Solar Radiation Pressure model’ has been discussed among the models. The model is also applied to predict a real-world visualization.

Keywords: Solar sail, Photonic Thrust, Luminosity, Reflection, SRP model

1 Introduction

 

In the long distant interstellar travel, space explorers need huge amount of fuel to thrust an engine of a spacecraft in order to change the momentum of the spacecraft and move towards the goal. Proposed in the early stages but applied in most recent times, the solar sail technology enhances the space explorer’s interstellar missions by achieving thrust without using a single drop of fuel. The statement is affirmative because of the sailing process by solar light/photon. By the wave nature of photon, the sunlight can provide a change of momentum or impulse to any reflective surface. This propulsion method has some limitations i.e. (i) the solar sail surface of the spacecraft must be in contact with the solar radiation, (ii) The sail must be in close proximity of solar radiation to be more efficient (iii) High surface area of the sail to produce effective thrust etc. By following some theoretical steps these limitations can be reduced. To improve the mass to traveling time ratio of the solar sail attached spacecraft is one of the ultimate goals of this propulsion technic.

 

2 Physics Behind the Photonic Thrust:

 

From the Einstein’s energy and momentum relation equation, P=E/c where, P is the momentum and E is the energy of the photon. This momentum is generated due to the wave nature of light and thus the light can provide thrust by reflection. (Fig-01)

Fig-01: A Solar Sail

3 Solar Radiation Pressure model:

Fig-02: Producing photonic thrust by the reflection of photons

 

Considering a solar sail normal to the sunlight direction (If not normal multiply cos² of the angle Theta, Ѳ=Angle between the normal vector with the surface and the solar radiation vector), the photons will hit the surface of the sail at an angle of zero degree, the pressure exerted(If the efficiency of the sail is 100%) is P=2I/c  …..(1); I= intensity of the solar radiation, c= velocity of light.  After r distance from the sun, I=Ls/4πr^2…..(2); Ls= Total power output of sun= 3.828×10²⁶ Watts. From equation 1 and 2 we can calculate the thrust produced by photons per unit sail area. Here is an important notice that thrust is decreased at the distance squared rate from the sun.

 

3.1 Real world visualization using SRP model:

Let’s consider a square shaped solar sail of the following parameters, Area- 200 m² , weight of the system, m=10 g/m², r= 10⁹m. Plugging in these values in the equations 1 and 2 we get, Total thrust= 40.61 N and a=20.31 m/s² which is much greater in the aero frictionless space.

 

4 Conclusion

Solar sailing technology can be a potential thruster for a long distant journey through the space. Not only interplanetary but also in the outer space of the solar system, this propulsion method can be applied effectively. Appropriate Material selection to create a highly reflective surface of the photonic sail is also a significant as well as a mandatory consideration of this photonic sailing technic.

References:

Bailer-Jones, C.A. (2021) ‘The sun diver: Combining solar sails with the Oberth effect’, American Journal of Physics, 89(3), pp. 235–243. doi:10.1119/10.0002178.