Tackling Space Debris: Challenges and Solutions for a sustainable space environment

Tackling Space Debris: Challenges and Solutions for a sustainable space environment

Sri Vamsi Rajesh

John P. Stevens High school

Independent Research Paper

July 2024

Abstract

Space debris has become a critical issue in the realm of space exploration and satellite operations. This paper examines the growing problem of space debris, its origins, types, and the threats it poses to current and future space missions. It explores the historical context of space debris accumulation, including significant events that have contributed to the problem, such as the destruction of the Fengyun 1-C satellite and the collision between Iridium and Kosmos 2551. The paper categorizes space debris by size, mass, spin characteristics, and orbital parameters, providing a comprehensive overview of the debris population. Furthermore, it discusses the potential dangers of space debris, including the Kessler Syndrome and re-entry hazards. The research also outlines current international laws and technological approaches aimed at mitigating the space debris problem. By synthesizing information from various sources, this paper aims to highlight the urgency of addressing space debris and the need for sustainable space environment practices

Keywords: Space Debris, Kesseler syndrome, ESA(European Space Agency)

Introduction

It has been about 65 years since the launch of the first artificial satellite, Sputnik 1, in 1957, marking the beginning of space exploration. As of 2024, there are approximately 9,900 active satellites orbiting Earth, contributing to a total of over 10,000 trackable objects, including satellites, parts of launch vehicles, space junk, human remains, and more. In the early history of humanity, humans did not explore every part of the globe at once; they gradually ventured into forests, seas, and untouched islands, eventually altering and polluting these environments. This concept of exploration also applies to our endeavors in space. The nature of space debris changed significantly after the launch of Sputnik 1 and the explosion of the Transit 4A rocket body on June 29, 1961. The repetition of these events—launching metal marvels into space and the subsequent break-up of spacecraft—has resulted in a substantial accumulation of debris. Many countries utilize satellites for various purposes, such as defense, telecommunications, weather forecasting, and conducting research about space. Space debris can be classified into two categories: natural and artificial. The primary issue with this debris is that it accumulates over long periods, and these pieces serve no useful purpose now or in the future. Space debris poses potential threats to future space exploration missions and can also pose risks to Earth. There have been multiple international laws established to address this issue, such as the Outer Space Treaty (1967), the Rescue Agreement (1968), the Liability Convention (1972), the Space Debris Mitigation Guidelines (2007), and the COPUOS Resolutions (United Nations Committee on the Peaceful Uses of Outer Space). This paper will provide an overview of space debris, its historical context, the physical characteristics of debris, and explore the threats it poses while discussing potential solutions to mitigate its impact on future missions.

Types of Debris

Space debris can be classified into two categories: Natural Orbital debris and Man-made orbital debris.

Natural Orbit Debris: Dust and micrometeoroids are small rocks weighing less than a gram. They are remnants of larger rocks that have broken down after the formation of the solar system. These particles are mostly found between planetary orbits. Figure 1 shows an example for a micrometeorite.

Man-made Orbit Debris: Man-made orbital debris includes various stages of rockets used in satellite or payload missions. The first stage, also known as the booster, is not reusable and remains in space. Subsequent stages are detached and discarded after the mission is completed. These stages can collide with micrometeoroids, breaking into smaller debris. Figure 2 shows an example for Man-made Orbit Debris.

(Fig 1:Micrometeorite image, Source: Wikimedia)

(Fig 2:Man-made orbit Debris, Source: Space.com)

History of Space Debris

The majority of space debris results from intentional or accidental collisions of large spacecraft. Over the past 50 years, numerous collisions have occurred, with some drawing significant global attention. Notably, the destruction of Fengyun 1-C and the accidental collision between two satellites in 2009—the American Iridium and the decommissioned Russian Kosmos 2551—marked significant increases in large orbital debris. These incidents alone contributed to one-third of cataloged orbital debris. The deliberate destruction of the Fengyun 1-C weather satellite by the Chinese military in early 2007, using a "kinetic kill vehicle" that struck the satellite at 16 km/s, created over 3,000 pieces of space junk that continue to pose hazards in low Earth orbit (LEO). Political reactions included statements from Australia's Foreign Minister expressing concern about the potential for an arms race in outer space, stating he did not want to see “some sort of spread, if you like, of an arms race into outer space.” Although the Outer Space Treaty bans weapons of mass destruction in space, it does not prohibit conventional weapons tests in orbit. In 2009, the defunct Russian communication satellite Kosmos 2551 collided with the American Iridium satellite, both owned by the same company, Iridium. This collision destroyed both satellites and generated thousands of trackable debris pieces smaller than 10 cm.

Additionally, on June 29, 1961, the US Transit-4A satellite was launched from Kennedy Space Center on a Thor Ablestar rocket, reaching an orbital altitude between 881 km and 998 km. After 77 minutes, the satellite and two additional payloads exploded, distributing 625 kg of mass across at least 298 trackable fragments. This event significantly contributed to the population of observable space debris, with on-orbit explosions becoming a primary source of space junk.

Size

The size of space debris is a crucial factor when assessing its potential to cause damage to other objects in space. Generally, larger debris pieces have a greater potential for destruction. For instance, an 80-gram piece of debris orbiting in low Earth orbit has a destructive potential equivalent to 1 kilogram of TNT (Trinitrotoluene). As of 2024, Table 1 provides details on the number of trackable space debris, though it is important to note that not all objects are tracked and cataloged. The number of debris objects estimated to be in orbit is based on statistical models, specifically MASTER-8, projecting future population data for 2024.

(Table 1: Number of trackable space debris)

The objects in space can be classified into two broad categories: Identified and Unidentified (UI). Identified objects are those that can be tracked after launch and can be further subdivided into smaller groups. Here are some of the subgroups:

• Payloads (PL): Objects designed to perform specific tasks in space, excluding the launch. Examples include operational satellites and calibration devices.

• Payload mission-related objects (PM): Objects that were useful during the payload mission. Common examples are astronaut tools and optical instruments.

• Payload Debris (PD): Fragments from a payload with unclear creation causes, identified by their orbit or physical characteristics.

• Payload Fragmentation Debris (PF): Fragments from a payload caused by identifiable events, such as collisions. An example of this is the Iridium collision.

• Rocket Body (RB): Objects designed to perform the launch.

• Rocket mission-related objects (RM): Objects intentionally released during the rocket mission that served a purpose. Common examples are engines and shrouds.

• Rocket fragmentation debris (RF): Pieces from a rocket body created by a known event, such as an explosion.

• Rocket debris (RD): Pieces from a rocket body with an unclear origin, identified by their orbit or physical properties.

We have Figure 3 and Figure 4, which present the count evaluation of the types of Identified debris and the mass of the debris, respectively.

(Fig 3: Count evolution by object type, Source: SDUP(Space Development User Portal)

(Fig 4: Mass evolution by object type, Source: SDUP(Space Development User Portal)

Mass

Large Debris: Large debris refers to objects with a mass greater than 1,000 kilograms. These include defunct satellites and rocket stages. Such debris is tracked due to the significant threat it poses to operational spacecraft, as their mass and potential for collisions can cause substantial damage.

Medium Debris: Medium debris ranges in mass from 1 kilogram to 1,000 kilograms. This category includes small satellites, rocket fairings, and equipment. Although these objects do not pose as high a risk as large debris, they are still monitored and accounted for in space operations.

Small Debris: Small debris encompasses objects with a mass from 1 gram to 1,000 kilograms. This includes fragments from larger debris, small satellites, and spacecraft components. Tracking these objects is challenging due to their size.

Micro Debris: Micro debris refers to objects with a mass less than 1 gram. These include painted flakes, dust, and other small particles. Despite their small size, if present in large numbers, they can pose a risk to spacecraft, particularly in terms of surface erosion and damage upon impact.

Nano Debris: Nano debris includes objects with a mass less than 1 milligram. These are extremely small and hard to track, often resulting from the degradation of larger debris. Although the threat from individual nano debris particles is low, their cumulative presence can impact the space environment.

Spin

Space debris spin refers to the rotation of space junk and can be classified based on its spin characteristics. The classification of debris by spin is crucial for tracking and predicting their behavior, as different spins can change the dynamics of debris. Understanding these characteristics helps assess the potential risk of collisions and aids in preventing such incidents. The main classifications are:

• Non-spinning debris: Refers to objects that have no spin or rotation. They have a stable orientation and no noticeable rotational motion. Examples include defunct satellite bodies, used rocket bodies, and other debris that do not spin.

• Low spin debris: These objects exhibit slow rotational motion with a slight wobble. They rotate at low speeds. An example would be rocket stages that are relatively stable but exhibit slow motion.

• High spin debris: This category includes debris with high angular velocity, resulting in unstable motion. These are often generated from the breakup of satellites or rocket stages, resulting in fragments that spin at high speeds.

• Tumbling debris: These objects have no stable orientation and exhibit tumbling motion. They rotate along random axes, making their movement hard to predict. This can occur due to satellite explosions or malfunctions.

Orbit

Several types of orbits are used in the space industry, each defined by the mission type, altitude above the Earth's surface, inclination, eccentricity, and the launch site's location (Table 2). These parameters determine the specific characteristics and applications of each orbit, such as communication, observation, or scientific research.

(Table 2)

Threats

The Cascade Effect, also known as Kessler Syndrome, is one of the most dangerous threats posed by space junk. This phenomenon presents a significant danger to space travel and missions in general, rooted in the fear of collisions. Even small fragments of space junk can pose a substantial threat to any space object. Hugh Lewis, a space debris researcher at Southampton’s School of Engineering, noted that “you only need something the size of a marble to completely destroy a spacecraft.” Space fragments have a very long lifespan, meaning this effect could have a lasting impact on space operations.

In our current generation, technologies such as GPS, weather monitoring, tracking, defense systems, and scientific research rely heavily on satellites. If debris the size of a marble were to collide with any of these satellites, it could potentially disrupt many industries and their economies, causing widespread system shutdowns.

Another significant threat posed by space debris occurs when it re-enters the Earth’s atmosphere, potentially causing damage. Generally, as debris re-enters, it tends to break down into smaller pieces and thus poses less harm. However, larger debris pieces can cause substantial damage. There have been a few notable incidents illustrating this risk:

• In November 2018, two large objects fell into a mining facility in Myanmar, destroying a home. One of these objects was about 15 feet long.

• In June 2024, a 3-foot, 90-pound piece of debris from SpaceX's Crew Dragon capsule crashed near a resort in North Carolina.

These incidents clearly demonstrate that metal pieces launched into space do not simply disappear; they might fall back to Earth, causing damage upon impact.

Current practices

International Law:

The international community has always tried to regulate how the area is being used. Before Neil Armstrong stepped his foot onto the Moon’s surface, the international community began to establish a legal scheme for space. The scheme (Outer Space Treaty) states to govern all outer space missions and also the celestial bodies. Ratified by 109 countries, including the United States. The Outer Space Treaty established space as a common place for mankind meaning it is a common tool for humanity. And they cannot claim anything as theirs found in space. But the Outer Space Treaty did not really focus on space debris but asserted that any object is the responsibility of the state that launched it.

Technologies to Combat Space Debris:

Agencies such as NASA and ESA (European Space Agency) have developed ways to reduce the risk of space debris. Current technologies are limited to what they can do; they can only retrieve defunct or retired satellites and not smaller pieces of debris. The method of removal depends on where the debris is located in LEO or GEO orbit. The satellites from LEO can be brought back to Earth. One way to retrieve it is to attach a robotic arm to a manned spacecraft. This method is very expensive and puts the astronaut's lives at risk. Hence it is not considered much. Another common method is to add residual fuel to the retiring satellite and maneuver it to land in the Pacific Ocean.

When a satellite in GEO cannot safely return back to Earth. The main method to remove defunct space objects is to push them into a “graveyard orbit.” GEO satellites do have some extra fuel and they are maneuvered into a less populated orbit and they are left there until a technology is built and capable of bringing them back into Earth. The ESA has also adopted a "Zero Debris Approach" as part of its Agenda 2025, aiming to limit the production of debris in Earth and lunar orbits by 2030. This includes stricter requirements for ESA missions to ensure the safe disposal of space objects, improve orbital clearance, avoid in-orbit collisions, and prevent internal break-ups. The guidelines also emphasize the need for international collaboration to maintain a sustainable space environment.

Concentrated Solar melting technique

This method is an experimental method to solve the debris in the LEO and mainly under 20 cm. Even though melting can cause extra debris, small parts such as paint flakes might vaporize. The proposed solution involves the deployment of a mini satellite, weighing approximately 100-180 kilograms. This size is optimal as it provides sufficient mass and volume to accommodate all necessary components while remaining manageable in terms of launch costs and orbital maneuverability.

The primary components of this system include:

1. Solar Reflectors or Mirrors: A set of strategically aligned mirrors designed to concentrate sunlight onto a single focal point. This concentrated solar power is intended to melt the targeted debris, effectively reducing its size and risk.

2. Robotic Arm: Equipped to capture pieces of debris and position them precisely within the focal point of the concentrated solar rays. This ensures that the debris is subjected to maximum heat and energy for efficient melting.

3. Power System: Comprising solar panels and batteries, this system provides the necessary energy to power the satellite's operations, including the mirrors' alignment and the robotic arm's movements.

4. Cooling System: Essential to prevent the satellite from overheating due to the concentrated solar energy. This system includes radiative cooling panels, cryocoolers, and thermoelectric coolers to dissipate excess heat and maintain operational stability.

5. Control, Navigation, and Communications (Nav. and Comms): Advanced control systems to navigate the satellite, align the mirrors, and ensure precise operations. This also includes communication systems to relay data and receive commands from ground control.

6. Debris Detection and Insulation: Utilizing computer vision (CV) and machine learning (ML) algorithms to detect and track debris. This ensures accurate identification and targeting of debris for capture and melting. Insulation is also necessary to protect the satellite's components from extreme temperatures and radiation.

7. Miscellaneous: Additional components such as radiation shielding to protect against harmful space radiation, and other necessary equipment to ensure the satellite's longevity and functionality.

By integrating these components, the proposed method aims to provide an innovative and effective solution for mitigating space debris in LEO.

Conclusion

In conclusion, the problem of space debris is complex and a growing concern for the sustainability of space activities. While the current technologies are limited in their ability to clear small pieces of debris, the development of those technologies are really important for our future.We have to find a solution as quickly as possible because outer space is vast and immense but the earth’s orbit is limited. We need to leave some free orbits for sustainability and for future space missions.

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