How well do you know about satellites??

On January 24, 2021, at 10 A.M SpaceX launched Falcon 9 with 143 satellites in a single mission beating ISRO's (India) previous record of 104 satellites in February 2017. Now let me ask you a few questions,

-> What keeps a satellite from falling to Earth?

-> What stops a satellite from crashing with each other?

-> What happens to old satellites?

If you don't any idea then read this blog to know the answers.

A satellite is generally defined as an object in space that orbits around a bigger object. There are two kinds of satellites: first, natural satellites (such as the moon) and second, artificial satellites (such as the International Space Station shortly the ISS). We all know about natural satellites, when it comes to Artificial satellites, they are classified based on the earth's orbit in which they are positioned. To know about different earth orbits read my previous blog "https://vocal.media/fyi/have-you-heard-of-earth-orbits".

An artificial satellite is an object that people have made and launched into orbit using rockets. They came into reality in the mid-20th century, the first artificial satellite was Sputnik 1, a Russian beach-ball-size space probe that was launched on Oct. 4, 1957. This act by the Soviet Union shocked the western world since they believed the Soviets do not have the capability to explore space. Within a month on Nov. 3, 1957 Soviets launched their second satellite " Sputnik 2", which carried a dog, Laika. Later other countries began to send their satellites into space as the benefits rippled through society, for example, Live television broadcasts, long-distance telephone calls across the world were made possible due to telecommunication satellites while weather satellites improved forecasts, even for remote areas. With the miniaturization of computers and other hardware, it's now possible to send up much smaller satellites that can do science, telecommunications, or other functions in orbit.

The main components of a satellite consist of three systems, namely communication system, power system, and propulsion system. The communication system consists of antennas and transponders that receive and retransmit signals. Whereas The power system includes the solar panels and batteries that provide power, and lastly, the propulsion system consists of rockets that propel the satellite. Individual satellites also need their own propulsion system to maintain their position and to make occasional corrections to that position. Launching a single satellite into space can cost anywhere between 10 million to 400 million dollars depending on the launch vehicle used.

Now to our first question: What keeps a satellite from falling to Earth?

Initially, gravity is the only force that acts on a satellite, if a satellite travels at a required speed, it will perpetually "fall" toward Earth, that is instead of crashing back on the surface it will fall around our planet due to Earth's curvature. As satellites get closer to Earth, the gravitational pull gets stronger and the satellite needs to move more quickly. The orbital velocity required to maintain a stable low Earth orbit is about 7.8 km/s, but this speed reduces with increased orbital altitude as gravity reduces with an increase in altitude. At a speed of 7.8 Km/s, a satellite takes approximately 90 minutes to complete an orbit, meaning the ISS in LEO completes 16 orbits in a day, while a weather satellite in GEO takes 23 hours, 56 minutes, and 4 seconds to complete an orbit.

Now to our second question: What stops a satellite from crashing with each other?

Right now, nearly 6,000 satellites are circling our tiny planet. In that only, 40% are operational others are all space junk. The nice and clear image of the earth from outer space shown in movies and images is fake. To say the truth, it was actually covered with satellites and space junks. According to NASA, there are half a million pieces of space debris in earth's orbit, this means there is a growing problem of cluttering up our access road to space and an increase in the possibility of an accident. Space agencies have to consider orbital trajectories carefully when launching satellites into space. Agencies such as the United States Space Surveillance Network keep an eye on orbital debris from the ground and alert NASA and other entities if an errant piece is in danger of hitting something vital. This means that from time to time, satellites need to perform adjustments to avoid an accident.

Lastly, what happens to old satellites?

Every machine gets old and satellites do get old! In the case of old satellites, two things can happen: firstly, For the satellites in lower altitude if the satellites are small in size, engineers will use its last bit of fuel to slow it down so it will fall out of orbit and burn up in the atmosphere but if it is a little bit bigger, then it might not entirely burn up before reaching the ground. In such cases, the engineers make sure debris falls into a remote area in the Pacific Ocean and This place even has a nickname—the Spacecraft Cemetery! If the satellite is larger, then it is left as it is. Secondly, satellites at higher altitudes are instead sent even farther away from Earth. The remaining satellites are left as space debris or space junk.

Space junk is now becoming a great threat and still, we don't have any effective management system. Several companies and entities are proposing different ways to get rid of this junk but they are not yet implemented due to practical difficulties. At the same time, they are only trying to get rid of them but why can't they reuse them?? SpaceX is reusing its launch vehicle then why can't the satellites be..! Even if it is not feasible now, I hope at least in near future the satellites should be designed in a way that they can be reused completely or partially after their lifetime, for example, the old satellite's parts can be stored in ISS so that they can be used to repair the damages in other satellites in space or can be brought down to earth for remodeling. This will reduce waste as well as minimize the manufacturing cost.