The Dangers of the Debris

Computer-Generate Image 
Representing Space Debris
in LEO and GEO

If you have watched the movie Gravity, you might already know about space debris. If you haven’t, what are you doing? Go watch it. It's great, but here is a quick summary. Two astronauts played by Sandra Bullock and George Clooney are in space and the satellite that they are in is struck by space debris. They have to figure out how to survive. It's a great movie. Go watch it. Anyways, today, we will be talking about space debris.

Now you may be wondering, what is space debris? Glad you asked. Space debris is any defunct or broken manmade object orbiting the Earth. These debris are different from satellites because they no longer serve any functions. Space debris is a big problem, as there is constantly being more and more space debris added into our orbit, and it imposes a risk for us and anything in orbit. However, there are some solutions to stop space debris. 

Replica of Sputnik 1

Space debris dates back all the way to the first launch ever, with Sputnik 1 in 1957. Sputnik 1 was launched by the USSR and was the first-ever satellite ever put into Earth’s orbit. Soon after, the North American Aerospace Defense Command (NORAD) started to create a database of all known rocket launches and all objects that were in Earth’s orbit. This database included things like satellites, protective launch shields, and upper-stages of launch vehicles. This tracker was aware of anything that was in orbit and was later developed by NASA in the 1980s. However, it showed that there was more and more space debris entering Earth’s orbit. In fact, NASA tried to join rocket designs so that fairings and rocket boosters wouldn’t actually enter orbit. However, this didn’t really help, because other space programs still used old designs which put rocket boosters into orbit. Here is some of the information about the amount of space debris in the last 12 years:

• As of 2009, 19,000 debris over 5 cm (2 in) were tracked.

• As of July 2013, estimates of more than 170 million debris smaller than 1 cm (0.4 in), about 670,000 debris 1–10 cm, and approximately 29,000 larger pieces of debris are in orbit.

• As of July 2016, nearly 18,000 artificial objects are orbiting above Earth, including 1,419 operational satellites.

• As of October 2019, nearly 20,000 artificial objects in orbit above the Earth, including 2,218 operational satellites.

Vanguard 1

Space debris, prior to contrary belief, isn’t just small bits of decommissioned satellites that are in our orbit. Space debris can consist of many different things. One thing is dead spacecraft. For example, the U.S. launched the Vanguard I into a medium Earth orbit (MEO) in 1958. Vanguard I’s upper stage is still in Earth’s orbit, making it the oldest surviving man-made object in orbit. It is predicted to remain in orbit for more than 240 years. Lost equipment can also be space debris. For instance, during the first American spacewalk, astronaut Ed White lost a glove. Other space equipment that were lost in space and became space debris include cameras, thermal blankets, and garbage bags. Rocket boosters also are an example of space debris. One example is the Centaur 2 Rocket Booster that just passed by Earth on February 2, 2021. Check out this article I wrote about it. Finally, there is debris from satellites that were destroyed by weapons. This debris was caused by anti-satellite weapons (ASATs). ASATs were popularly used by the US and USSR to destroy old satellites. However, after they started to create more debris, the two nations decided to deorbit satellites and have them burn up in the atmosphere. As shown by this, space debris can come in many different sizes. While most are present on LEO, there is also space debris in MEO and geostationary orbit (These are orbits where the satellites are always pointing at one place of the Earth. TV and communication satellites operate like this. They are normally at an altitude of 35,000 km.) They also travel at extremely fast speeds, which makes them even more dangerous.

Entry Hole Created by Space Debris
During STS-118 on Space Shuttle
Endeavor's Radiator

Space debris poses a danger to spacecraft in orbit as well as people on Earth. Space debris is a hazard to active satellites and spacecraft. This risk is constantly increasing as more and more rockets and satellites are launched into orbit. They are also a threat to spacecraft that are passing through LEO. There have been many instances of space debris coming into contact with both uncrewed and crewed spacecraft. One example was on the Space Shuttle Challenger’s front window during STS-7. During this, a piece of space debris hit the window and created a 1 mm pit on the window. Another example with the Space Shuttle was with STS-118, where a piece of space debris blew a bullet-like hole through Endeavour’s radiator panel. The reason why the damage was so much was that both the space shuttle and space debris travel at very fast speeds, causing a high amount of damage. Bigger crewed spacecraft often have a safeguard to protect themselves from space debris. For example, the ISS uses Whipple shielding to protect itself from minor debris. Whipple shields are a type of hypervelocity impact shield that protects spacecraft from space debris.

Whipple Shield Used on 
NASA's Stardust Probe

However, exterior portions of the ISS can still be damaged. In 1989, the ISS panels were predicted to degrade 0.23% in four years due to “sandblasting” from small space particles. People on Earth are also in danger from space debris. While smaller debris often gets burned up during reentry, larger debris isn’t. Surprisingly, data from NASA shows that an average of one cataloged piece of debris has fallen onto Earth every day. For instance, in 2001, a Star 48 Payload Assist Module (PAM-D) rocket upper stage re-entered the atmosphere and crashed landed in the Saudi Arabian desert.

PAM-D Module in the Saudi Arabian Desert

All of these instances match up with the Kessler syndrome. The Kessler syndrome was proposed in 1978 by NASA scientist Donald J. Kesseler and was a theoretical scenario in which a collision due to space debris in LEO could create a cascading effect, resulting in more collisions. This model was essentially a domino effect that really showed the dangers of space debris in LEO and was one of the reasons NASA stepped its game up to handle space debris. There were a few potential triggers of this effect that almost occurred. One was the Envisat, which is a large and inactive satellite. Kessler predicted in 2012 that it could cause the Kessler syndrome to kickoff. Another, more recent program that is raising concern for the Kessler syndrome is SpaceX’s Starlink. Starlink is a network of satellites that will provide internet access all over the world. However, Starlink will add many more satellites in LEO, adding to the Kessler syndrome.

Baker-Nunn Camera Used
to Study Space Debris

Currently, there are many different ways to detect space debris. The two main ways are tracking from the ground and measuring in space. Radio and optical detectors are the main tracking tool for tracking space debris from the ground. One example, lidar, can track space debris as small as 1 cm. There are also different observation methods from the ground that focus only on tracking larger objects. Databases are constantly updated with any data that is collected from ground trackers. In space, to measure space debris, they actually collect spacecraft parts that were damaged by space debris. By studying these parts, scientists can predict the sizes and speeds of future space debris. Scientists also use Gabbard diagrams to study space debris. These are diagrams that graph debris based on its orbital period.

Figuring out how to deal with space debris is becoming a more important problem that we have to solve. With the growing number of satellites and space debris in orbit, we are getting closer to a Kessler syndrome situation. To avoid this, many satellites are initially launched to elliptical orbits so that the satellites will essentially destroy themselves. Other satellites, like CubeSats (Here is a link to an article I wrote about them) stay in very low orbits to avoid a majority of space debris. Other satellites are using self-removal to decrease the amount of space debris. These almost dead satellites use their remaining fuel to de-orbit themselves either towards Earth to burn up in the atmosphere or into deep space. Other satellites will move closer to decrease their atmospheric reentry time. This is what the French Spot-1 satellite did. With an initial re-entry time projected in 200 years, the French Spot-1 satellite lowered its altitude, changing the projected re-entry time to 15 years. Currently, there is no international treaty on minimizing space debris, but there are voluntary guidelines.

Model of Debris in Orbit

There is also the idea of external removal. External removal is where spacecraft remove existing space debris. To decrease human risk, one idea is remotely controlled vehicles. These vehicles will capture and return debris to a central station. One such system is the Clean Space One project. This project and mission hope to make Earth’s orbit safer by removing space debris. In December 2019, the ESA awarded the first-ever contract to clean space debris for a mission named ClearSpace-1. This mission is expected to launch in 2025 and will collect junk using robotic arms and burn them through re-entry. Another method that is in the talks is using a laser. This laser would be ground-based to destroy space debris or move debris out of the way. Nets are also being used to remove space debris. JAXA has already started to test using space nets. In December 2016, JAXA sent a space junk collector to use a tether to remove stuff out of the orbit. However, the test was unsuccessful. However, the ESA is working on a design to remove large debris out of space. The final removal method that might be used in the future is harpooning. Harpoons were used in the RemoveDEBRIS mission to test many different removal methods. The mission was launched on April 2, 2018.

Render of Cleanspace One

Space debris is a problem as old as the space race, starting with the launch of Sputnik 1 and growing exponentially ever since. Many things are classified as space debris, including decommissioned satellites, lost equipment, and rocket boosters. These all come in many shapes and sizes, with most being located in LEO. Space debris poses a threat to crewed and uncrewed spacecraft as well as people on Earth. These instances are shown in the Kessler syndrome developed by NASA scientist Donald J. Kessler. Currently, there are many different ways to detect space debris, and there are many different ways being developed to remove space debris out of Earth’s orbit. Space debris is an important problem that we need to solve as soon as possible. If we don’t figure out how to solve this problem, we could be closer to Gravity actually occurring.

Space Debris in LEO (Exaggerate Size)

Sources:

“Gravity (2013 Film).” Wikipedia, Wikimedia Foundation, 21 Feb. 2021, en.wikipedia.org/wiki/Gravity_(2013_film). 

“Kessler Syndrome.” Wikipedia, Wikimedia Foundation, 14 Feb. 2021, en.wikipedia.org/wiki/Kessler_syndrome. 

Pradhan, Arnav. Earth Is About to Say Bye-Bye to Its Second Moon, Blogger, 3 Feb. 2021, www.arnavpradhan.com/2021/01/earth-is-about-to-say-bye-bye-to-its.html.

Pradhan, Arnav. The Rubik's Cubes in Space, Blogger, 5 Feb. 2021, www.arnavpradhan.com/2021/01/the-rubiks-cubes-in-space.html. 

Rukja, et al. 

“Space Debris.” Wikipedia, Wikimedia Foundation, 9 Feb. 2021, en.wikipedia.org/wiki/Space_debris.

“Sputnik 1.” Wikipedia, Wikimedia Foundation, 17 Feb. 2021, en.wikipedia.org/wiki/Sputnik_1.  

“Whipple Shield.” Wikipedia, Wikimedia Foundation, 24 Sept. 2020, en.wikipedia.org/wiki/Whipple_shield.