Pieces Of Orbital Debris Research Articles

Red Light or Green Light?: Legal Considerations for Regulating Traffic in Orbit

The number of functional and non-functional satellites, and other pieces of orbital debris, is constantly increasing due to new space activities, including use of large constellations of small satellites, and the growth of commercial space missions. Congestion in space challenges the ongoing safety, security and sustainability of space activities and space assets. There are now more than one million debris items larger than 1cm orbiting the Earth, and this number may grow exponentially as more than 100,000 additional satellites are planned for launch over the next ten years. These will only add to the increasing risk of damage and destruction to any satellite involved in case of a collision in space. In this context, there is a necessity to develop a Space Traffic Management (STM) regime that encompasses the means and the rules to safely access, conduct activities in, and return from outer space. It would also aim to protect the Long-Term Sustainability (LTS) of space activities by ensuring that space remains a secure environment, even as global society relies ever more on space-based applications such as communications, navigation and Earth observation. This article examines those rules present in the current space legal framework that are relevant to the regulation of space traffic and analyses two key concepts for establishing a comprehensive STM regime, namely the monitoring of space activities through data access and information sharing, and appropriate coordination mechanisms between states, Space Agencies and private operators. space law, regulation, traffic in orbit, space debris, space situational awareness, information sharing, coordination, international cooperation

Rupture limit equation for shielded COPVs

How well a spacecraft component resists the damage that might occur following a high-speed impact by a meteoroid or piece of orbital debris is one of the main design considerations for earth orbiting spacecraft. Most spacecraft have at least one pressurized tank on board, such as a liquid propellant tank. In addition to a hole, it is possible that, for certain tank designs, construction materials, operating conditions, and impact parameters, a pressurized vessel may experience catastrophic failure (i.e. rupture) as the result of such a high-speed impact. Risk assessments performed during the design phase of a spacecraft typically consider and weigh the likelihoods and consequences of various failures that might occur following a MOD particle impact, including whether or not such a tank rupture might occur. In this paper, the datasets from several test programs involving shielded and unshielded composite overwrapped pressure vessels (COPVs) are combined to yield a single, new equation that can be used for this purpose. Comparison with test data shows that this new equation is able to correctly discriminate between the COPV rupture and non-rupture data points for the full high-speed impact test database considered herein.

Quantitative assessment of a threshold for risk mitigation actions

Many low-Earth-orbit missions have a policy that if a future conjunction with a secondary object such as a piece of orbital debris is detected, a go/no-go meeting will be held to decide about a risk mitigation action before the time of closest approach. Commonly, the policy is that a probability of collision (Pc) above a predetermined action threshold at the time of the meeting means the mission will take action to reduce the risk. The value to which the action threshold is set is a compromise—if it is higher, then there is a higher probability that a collision might occur when action is not taken; if it is lower, then more actions will be taken, increasing the cumulative costs and risks of the actions themselves. This paper shows how a policy using an action threshold affects the overall mission risk of a collision with a large object. We augment this with estimates of action success, expected hard-body radius, and expected covariance to obtain an algorithm for estimating the risk reduction associated with an action threshold policy. We apply this algorithm to the OCO-2 and CloudSat missions as examples, using historical conjunction data for these two missions, and show how this algorithm can guide developing missions in setting an action threshold.

Optimal Capture of a Tumbling Object in Orbit Using a Space Manipulator

This paper introduces an optimal capture strategy for a manipulator based on a servicing spacecraft to approach an arbitrarily rotating object, such as a malfunctioning satellite or a piece of orbital debris, for capturing with minimal impact to the robot's base spacecraft. The method consists of two steps. The first step is to determine an optimal future time and the target object's corresponding motion state for the robot to capture the tumbling object, so that, at the time when the gripper of the robot intercepts the target the very first instant, the resulting impact or disturbance to the attitude of the base spacecraft will be minimal. The second step is to control the robot to reach the tumbling object at the predicted optimal time along an optimal trajectory. The optimal control problem is solved with random uncertainties in the initial and final boundary conditions. Uncertainties are introduced because sensor and estimation errors inevitably exist in the first step, i.e., determination process of the initial and final boundary conditions. The application of the method is demonstrated using a dynamics simulation example.

Building Security in Space: A Brief Introduction

Asian Perspective 35 (2011), 497-501 Building Security in Space: A Brief Introduction Peter Van Ness In early April 2011 we convened an international workshop at the University of Hawaii titled “Avoiding an Arms Race in Space.” The idea was to bring space scientists from the United States and China together with international relations specialists to identify common ground for a code of conduct on building security in space. Our objective was to maintain outer space as a global commons for all the world’s people to enjoy. This was perhaps the first meeting of its kind. The articles published in this special issue are written by the Chinese and US participants in the workshop, with the exception of Shenyan Chen, who did not participate because she could not get a US visa in time, but wanted to contribute her article on space debris. We began with the following proposition: An arms race in space among the major powers would be immensely dangerous, destabiliz­ ing, and expensive. Russia, which has a long history in space tech­ nology dating back to Sputnik in 1957, does not today have the resources or the political will to sustain such a race. But China does. This is principally an issue between the United States and China. It is in the interests of both the United States and the People’s Republic of China—and the world!—that the weaponization of space be stopped. All of us are beneficiaries of the many services provided by the satellites orbiting in space. Modem society, as we know it, would not be possible without the space satellites that we have become depend­ ent on for telecommunications, banking and other commercial trans­ actions, the Internet, meteorology, and navigation. The military depends on space satellites for command and control, targeting of weapons, and intelligence gathering; since 2007, China and the United States have both tested antisatellite (ASAT) weapons. In that sense, space has already been militarized. But it is not yet weaponized: there are not yet any space-based weapons. There are now more than 960 operating satellites orbiting the 497 498 Building Security in Space earth. As of May 2011, 443 were from the United States, 101 were from Russia, and 69 were from China. The US satellites were cate­ gorized as 10 civil, 194 commercial, 118 government, and 121 mili­ tary. Complicating the picture and endangering the functioning of these satellites is space debris. More than twenty thousand pieces of space debris of varying sizes are orbiting the earth, many of them too small to track, and they are a serious danger to the operating satel­ lites. For example, in April 2011, and not for the first time, the Inter­ national Space Station had to maneuver to stay a safe distance from a piece of orbital debris. The US-China Joint Statement, published during PRC president Hu Jintao’s official visit to the United States in January 2011, called for bilateral cooperation in many fields, including space. When Pres­ ident Barack Obama announced a New National Space Policy in June 2010 he called for “peaceful cooperation and collaboration in space,” and invited arms-control proposals to make that happen. China has also urged cooperation, insisting that China would not participate in any kind of arms race in space. More recently, the US deputy assis­ tant secretary of defense for space policy, Gregory Schulte, said that the United States wanted to establish a regular dialogue with China on outer space in order to create “rules for the road” and avoid misun­ derstandings between the two countries. In June 2011 The Economist magazine declared “The End of the Space Age,” and in July 2011 Atlantis, the last of five NASA space shuttles, made its final trip to the International Space Station and safely returned to Earth. Yet the space race continues. Both the US and Chinese militaries are pressing forward with plans for space weapons, and commercial firms are competing to put people in space. China plans to launch its own space station by 2015, and is inviting scien­ tists from all countries to participate in its experimental research, while Russia, India, and other spacefaring nations have announced new space...

Protecting spacecraft against orbital debris impact damage using composite materials

All earth-orbiting spacecrafts are susceptible to impacts by meteoroids and pieces of orbital debris. These impacts occur at extremely high speeds and can damage flight-critical systems, which can in turn lead to catastrophic spacecraft failure. With the advent of many new high-strength composite materials and their proliferation in aircraft applications, it is necessary to evaluate their potential for use in long-duration space and aerospace structural systems. This paper presents the results of several experimental investigations in which several different composite materials were tested for their ability to prevent the perforation of the inner walls in multi-wall systems subjected to hypervelocity projectile impact. Damage to multi-wall systems that employ composite materials is compared to damage in traditional all-aluminum multi-wall structures of similar geometry and weight under similar impact conditions. The advantages and disadvantages of using composite materials in perforation-resistant multi-wall structures are presented and discussed. The analyses performed show that the effectiveness of multi-wall systems with composite materials varies significantly depending upon the location within the multi-wall system of the composite materials. Based on the results obtained, it appears that composite materials are most effective when used as the middle wall of a triple-wall system.

Hypervelocity impact of dual-wall space structures with graphite/epoxy inner walls

The design of a spacecraft for an earth-orbiting mission must take into account the possibility of high-speed impacts by pieces of orbital debris and their effects on the spacecraft structure and on all of its exposed subsystem components. This paper presents the results of a preliminary experimental investigation in which the perforation resistance of dual-wall structures with aluminum outer walls and graphite/epoxy inner walls was compared against that of all-aluminum structures under simulated orbital debris impact loadings. The advantages and disadvantages of using graphite/epoxy as the inner wall material of a dual-wall structure are presented and discussed. The analyses performed showed that the effectiveness of the graphite/epoxy panels varied significantly depending on the velocity of impact. Based on the results obtained, the primary advantage of using graphite/epoxy as the inner wall material appears to be that it eliminates the severe cracking and petalling sustained by aluminum inner walls in dual-wall systems with internal multi-layer thermal insulation.

Response of space structures to orbital debris particle impact

All long-duration space and aerospace and transportation systems, such as the Space Station Freedom and the Space Shuttle, are susceptible to impacts by pieces of orbital debris. These impacts occur at high speeds and can damage the flight-critical systems of such spacecraft. Therefore, the design of a structure that will be exposed to a hazardous orbital debris environment must address the possibility of such hypervelocity impacts and their effect on the integrity of the entire structural system. A technique is developed for analyzing the response of dual-wall structures to oblique Hypervelocity projectile impact. Ballistic limit curves that predict the potential of an impacting projectiles to perform the main wall of a dual-wall strucutral system are obtained using the techniques and are compated against experimentally derived curves. Comparisons are performed for a variety of impact velocities, trajectory obliquities and projectile masses. It is shown that the results obtained using the technique developmed herein compare very well with experimetanl results.

Aluminum 2219-T87 and 5456-H116: A comparative study of spacecraft wall materials in dual-wall structures under hypervelocity impact

All earth-orbiting spacecraft are susceptible to high-speed impacts by pieces of orbital debris. To prevent mission failure and possibly loss of life, protection against perforation by high-speed orbital debris particles must be included in the spacecraft design. Although any number of materials can be used to manufacture perforation-resistant structures, aluminum is often used in such systems because of its relatively high strength-to-weight ratio. This paper presents the results of a study in which the high speed impact response characteristics of dual-wall structures made from two different aluminum alloys were analyzed to determine which alloy would be more suitable for use in a perforation-resistant dual-wall structural system that is to be exposed to the orbital debris environment. Impact response characteristics were obtained numerically and experimentally. At impact speeds below ⋍7 km/s , it was found that the two aluminum alloys considered contributed similar levels of perforation resistance; at speeds in excess of ⋍7 km/s , aluminum 2219-T87 was superior to aluminum 5546-H116 in preventing perforation of dual-wall structural systems.

Use of composite materials in multi-wall structures to prevent perforation by hypervelocity particle impact

All earth-orbiting spacecraft are susceptible to impacts by meteoroids and pieces of orbital debris. These impacts occur at extremely high speeds and can damage flight-critical systems, which can in turn lead to catastrophic failure of the spacecraft. The design of a spacecraft for an earth-orbiting mission must take into account the possibility of such impacts and their effects on the spacecraft structure and on all of its exposed subsystem components. This paper represents the results of an experimental investigation in which several different composite materials are tested for their ability to prevent the perforation of the pressure walls in multi-wall systems subjected to hypervelocity projectile impact. The damage in the composite material specimens is also compared to the damage in aluminum specimens of similar geometry and weight caused by hypervelocity projectiles with similar impact energies. The analysis shows that using composite materials in combination with metallic materials in multi-wall structures can increase the protection afforded a spacecraft against perforation by orbital debris particles over that provided by traditional, purely metallic double-wall structures.