How Do Satellites Get Power?

Satellites are some of the most important, advanced, and amazing pieces of technology that humanity has created.

The fact that we as a species have sent an object beyond the atmosphere of our earth to live semi-permanently in the void of space while being used as a tool for the advancement of our society is unbelievable.

It was unbelievable before the first moon landing in 1969, and it is still somewhat unbelievable today that we can do it, despite all the evidence to the contrary.

Space just seems so impossible to reach or reside in, and the fact that human-made satellites have done both is extraordinary.
These objects do so much for humanity as well.

They provide us with precise data about the world, track our weather, maintain our television broadcasts, help us navigate, allow for rapid communication between banks and customers, and many, many more things.

The problem with being so far away from earth, on the cusp of true space, is that there is no easy access to energy or power.

So, when satellites have been launched and are successfully orbiting the earth, how do they get power?

Are they launched with fuel? Or do they have to produce their own?

Today, we will take a more in-depth look at this question and find out once and for all the different ways that satellites get their power.

Solar Arrays

There is one source of power that satellites rely on more than any other, and that power source is solar energy.

This may come as a shock to some people, especially with the little amount of solar energy that we as a society use compared to other energy sources.

However, it is the one that probably is the most sustainable, especially in space. If you take all other forms of energy we use on earth – fossil fuels, wind, hydroelectric, and so on – none of them can be found in space or if they are, it would be impossible to find them, thanks to the vast emptiness of space.

This is not an issue for solar energy, as our sun is nothing but a giant solar battery, constantly pumping out solar energy and radiation to almost all of the solar system.

With the sun on our side, it is much easier to just create something that can convert solar energy into electrical energy, rather than try and send enough alternate fuel with the satellite or even constantly try and refuel it.

Solar arrays are a little different from the standard solar panels you see in your daily life.

For starters, they fan out from the satellite with the main body of it being in between them, rather than just attached to the outside.

Not only this, but the arrays themselves are much better at converting solar energy to electrical energy and more efficient at absorbing sunlight than standard solar panels.

The reason behind this is that only about 20% of sunlight can be converted into electrical energy, while the rest just bounces off the panel.

As such, the arrays need to fan out to maximize the surface area sunlight can hit and be more efficient at capturing that sunlight, otherwise, the satellite will run out of power.

The other thing that makes solar arrays more effective is their flexibility. Solar arrays are incredibly flexible and move more like loose fabric than glass plates.

Many people have compared them to the sails of a ship, which is actually the point of them. When there is a lot of solar energy to absorb, the arrays can unfurl, while when there is only a little, they can be pulled in to save energy.

This flexibility is also perfect for protecting the arrays from space debris. When an object moves through space, there is no friction or force to slow it down, so it moves at the same exact speed it started at.

Due to this, when these objects hit another solid object, they collide, and often this collision causes damage. For the solar array, their flexibility means that they take less damage and can still keep working most of the time.

Hypergolic Propellant

Once a satellite leaves earth’s gravitational field and enters orbit around our planet, then there are very few forces acting upon it to dislodge the satellite from orbit.

At the altitude a satellite would be at in comparison to the ground, the earth’s gravity will stop it from floating away, but it cannot exude enough force to pull it out of orbit, which leaves the satellite floating in a state of limbo around the planet.

Yet, that doesn’t mean that no force is being enacted upon the satellite, earth’s gravity is still pulling on it slightly and there are many objects in space that might fly past and knock it slightly off its trajectory.

If something were to push or pull the satellite out of orbit, it may float off into space or crash down into the earth.

As such, satellites need some fuel to adjust and maintain their position, as well as give ground control something to use in case they need to take control of the satellite for repositioning away from other satellites or in emergencies.

The fuel that they use during these moments is called hypergolic fuel. This is the same kind of fuel that is used for rockets when they make space flights, and there are two main advantages to using this fuel.

The first is that it stays liquid at room temperature, meaning as long as you keep its storage area between 18 and 24 degrees Celsius, then this fuel is ready to go.

The second advantage is that hypergolic fuel is a mixture of two different substances that when combined spontaneously ignite into a huge thermal reaction.

This may seem a bit dangerous, but it means that as long as you seal them separately you don’t really have a lot to worry about, especially on an unmanned satellite.

This fuel is very useful when placing a satellite in orbit, as you don’t really need a lot of it.

It takes very little fuel to maintain an orbit and the satellite requires just enough to adjust its course or move out of the way of other satellites, as such there are no huge ignitions like with the space shuttles, more of a small thrust that pushes the satellite gently.

Although this isn’t really a power source for the whole satellite it is a part of the power to the engines that satellites use, therefore it is necessary for this list.

Batteries

The little power sources that make our world go round: batteries.

From your phone to the TV remote, to even satellites, everything uses batteries, and they are especially key in space.

Solar arrays may be the main power source of satellites and hypergolic propellants may help them move, but batteries are the objects that keep them working year-round.

The reason for this is due to the nature of our solar systems physics and the limitations of solar arrays themselves. Our solar system works due to a lot of gravitational forces putting pressure on one another, mainly planets and the sun.

This pressure causes orbit for our planets around the largest gravitational source, the sun, in the space of 365 days. Our earth also rotates on its axis, which causes our night and day cycle.

Due to these factors, there are times when no sunlight is cast on areas of the earth, which in turn will affect the solar arrays of the satellite.

The solar arrays can’t convert sunlight to electrical energy if there is no sun and since this happens regularly this would be a huge problem for them. Enter batteries.

With batteries, onboard a satellite, having no sun is not a concern as they are effective storage devices. When it is sunny, the solar arrays can transfer any excess energy they are extracting to the batteries, and then the batteries can store that energy for when there is no sunlight.

At the moment when the sun fades, they can use the stored energy until there is sunlight again, thus creating a semi-perpetual energy source. It is a rather effective solution to the issue of storing power on an important tool that you cannot reach.

Final Thoughts

Creating power or energy in space is difficult, by its very nature there are not many resources to use or acquire out there.

Yet, through observation, understanding of physics, careful planning, and lateral thinking, humanity has managed to create semi-permanent objects that hold an essential function around our atmosphere using the sun as a power source.

This is an incredible scientific and engineering feat that will surely pave the way for further space exploration in the future. All from basically turning our information distribution satellites into giant floating photosynthesizers.