What is a Solar Sail : Types & Its Applications

Nearly hundreds of years back, Europe was involved in the naval investigation of the planet. So an astronomer namely “Johannes Kepler” was proposed the thought of investigating the galaxy through the solar sail. But while his investigation, some comet tails were blown through some type of solar wind, he said that sails could capture that breeze to push spacecraft.

While this solar wind idea has been disproven, scientists from NASA have been investigating with massive solar sails to drive through the light cosmos. Solar sail uses energy from the sun and transmits to use into deep space. This article discusses an overview of Solar Sail.

What is a Solar Sail?

A revolutionary method used to propel a spacecraft throughout space is known as a solar sail. A spacecraft includes huge reflective sails which capture the light energy from the Sun & push the spacecraft frontward. The solar sail diagram is shown below.

At present, the materials used to make solar sails are lightweight like polyimide or Mylar coated through a metallic reflective coating. Theoretically for a solar sail, there is no least size however for the similar mass spacecraft; larger sails will capture additional sunlight to speed up the spacecraft more rapidly.

In the year 1970, a NASA team proposed a solar sail through a 600,000 square meters surface area that would be utilized to transmit a spacecraft to congregate with comet Halle. This is equal to a square of 800 meters.

How does Solar Sail Work?

We know that lights are made up of different photons which don’t contain any mass, however, they move throughout space they do have energy. Once light strikes a solar sail, then photons within the light will bounce off the solar sail. Here it includes a bright & mirror surface.

When the photons strike the sail then their energy will transfer to it by providing a small push. Since they reflect the sail, then photons provide another push. So both these pushes are extremely small, although in the space vacuum wherever there is nothing to delay the sail, every push will change the speed of sail.

Direction Control

Once a solar sail is arranged directly at the face of the Sun, then photons will thrust the spacecraft frontward. However, it can go in other ways through tacking similar to a sailboat, modifying the sail’s angle that is comparative to the Sun.

It is also feasible to move the orbit of spacecraft in the region of the Sun by angling the solar sail so that photons will thrust against its traveling direction. It also controls their direction in different methods like shifting their midpoint of mass.

Solar Sail Speed

The speed of a solar sail mainly depends on its mass and size because a larger sail mainly captures extra sunlight, achieving more momentum & speed up more rapidly for the equal mass. For a provided sail size, a less mass spacecraft will include a high acceleration.

The maximum speed of this is 10% of the light speed associates with 18,600 miles/ sec. Spacecrafts powered by solar are capable of traveling quicker as compared to conventional spacecraft because of the constant light force being given to the sail to push it frontward.

In the future, NASA scientists estimating its speed to reach 150,000 mph. On that speed, this sail could arrive at Pluto within less than 5 years.

Solar Sail Components

A spacecraft powered by a solar sail includes three essential components like Constant force used by sunlight, big and very thin mirror & a launch vehicle. A spacecraft does not require the usual propellant for power, as its propellant is sunrays & the sun is its engine.

Here, light is collected with electromagnetic radiation that uses force on objects. The scientists from NASA have established that 1AU or astronomical unit is the distance in between the earth & the sun that is equivalent to 150 million km,

The power generated by the Sunlight is 1.4 kw. The force used by the sun can be calculated by the power and divided by the light speed.

In contrast, the main engine of a space shuttle can generate 1.67N millions of power throughout takeoff & 2.1 million N of push within a vacuum. Finally, the continuous energy of the daylight on a solar sail could push a spacecraft five times quicker as compared to usual rockets.

Types of Solar Sail Designs

These designs are classified into three types namely square sail, heliogyro sail & spinning disk sail.

Square Sail

A square sail is used to produce maximum force because of the big surface area. Generally, these are designed with four masks which are arranged into space. As compared to other types of sails, this sail has some benefits like there are no hot spots due to the sail guards the spacecraft from the thermal heat of the sun. This kind of sail is most frequently used because of its simple shape & surface area is large.

Heliogyro Sail

In 1970, this kind of sail was invented & the structure of this sail is very stronger. It utilizes angular momentum to eliminate the requirement of support that results in a lighter spacecraft. This kind of sail includes 12 spinning blades where each blade length is 4 miles long.

So, the spacecraft moves toward Halley’s Comet. The controlling of these blades can be done similarly to a helicopter by altering the pitch & cycle to movement.

Spinning Disk Sail

This kind of sail was designed by JPL as compared to Heliogyro sail, spinning disc type sails are related in that both rotate when they move in space; but, their design structure will change. In this kind of sail, sail masks include a small gap in between them to increase the sum of the surface region like a square sail.

For large manner arrangements, this kind of sail has a very attractive design because it includes a ring inside to have artificial gravity that is equivalent to the Mars gravity on its surface.

Tests before Launching

There are different types of tests exist which are used before launching a solar sail.

• Ground Deployment
• Suborbital
• Attitude Control

Ground Deployment

In solar sail missions, the method like fold deployment is the main technology. For the mission’s success, the sail can arrange through the booms within the orbit is the solution. To check the arranged process is reliable and stable, the fold deployment method is used within a 100meter scale sail & a ground deployment test is performed on this model.

In this model, the SMC boom concept was used within the 160x160m sail using a complete air tube-like inflatable boom. The thickness of this tube is 1mm and it is designed through Kapton AI Kapton membrane. Here, the boom rigidity can be enhanced by adding 4 curve steel strips within the tube.

Suborbital Tests

The suborbital test, followed by a complete orbital mission, so this test was to feature a spacecraft through simply two petals & carry a camera to monitor operation.

Attitude Control

An active ACS (attitude control system) is very important for solar sail craft to obtain & handle a required direction. The direction of the sail will change gradually within interplanetary space however very quickly within a planetary orbit.

This control can be achieved through a relative shift in between the center of pressure with craft & its mass center. So, this can be achieved through control vanes, individual sails movement, a control mass movement, etc.

Why do we use Solar Sails?

The solar sail applications mainly include the following.

• It is used to propel a spacecraft throughout space. The spacecraft of a solar sail includes huge reflective sails which capture the energy of light from the Sun & push the spacecraft ahead.
• Solar sails could open up new paths especially for space science & exploration. A solar sail-powered spacecraft could arrive at far-away planets very quickly due to the constant acceleration.
• It is used very efficiently for other mission classes like monitoring of solar, flybys with multi-object. Spacecraft with pole-sitting for nonstop observations of Earth & Polar Regions of other objects
• It provides CubeSats propulsion like small, low-cost satellites that are being used through emerging space-faring states, miniature companies & also school groups which permits them to plan within space without depending on the fuel of the rocket.
• Protection of planetary
• Large cargos & people delivery
• For particular artificial orbits maintenance
• Solar system exploration
• Delivery of observatories or science instruments
• It is used within space ships for both the satellites like manned & unmanned
• For corrections of trajectory, these are used in satellites

Advantages & Disadvantages

The solar sail advantages mainly include the following.

• The solar-sail spacecraft advantage is, it travels between the stars and planets without using fuel. It uses simply a conventional launch vehicle to enter into Earth orbit, wherever the solar sails can be arranged & the spacecraft transmit on its way.
• It doesn’t need fuel
• Use of less spacecraft resource
• Low within the mass
• Lifespan is longer within space

The solar sail disadvantages mainly include the following.

• The main drawback of a solar sail is the science missions do not lie within LEO (Low Earth Orbit). So we run the validating risk of solar sails like a technology within a surrounding for which they are not proposed.
• The operating temperature of the sail is a function of sail angle, solar distance, reflectivity, etc. Sail is used simply where its temperature is kept within the limits of the material.
• They are delicate, large & cannot be utilized on any craft proposed to land on other bodies unless retracted.

Thus, this is all about an overview of solar sail which is used for a long-distance NASA mission. Solar sails are also known as photon sails or light sails which are a spacecraft propulsion method with radiation force used through sunlight on huge mirrors. Here is a question for you, what are the solar sail design challenges?