Conceptualizing thresholds for effective active debris removal in Low Earth Orbit

The space industry's rapid recent growth represents the latest tragedy of the commons. Satellites launched into orbit contribute to-and risk damage from-a growing buildup of space debris and other satellites. Collision risk from this orbital congestion is costly to satellite operators. Technological and managerial solutions-such as active debris removal or end-of-life satellite deorbit guidelines-are currently being explored by regulatory authorities. However, none of these approaches address the underlying incentive problem: satellite operators do not account for costs they impose on each other via collision risk. Here, we show that an internationally harmonized orbital-use fee can correct these incentives and substantially increase the value of the space industry. We construct and analyze a coupled physical-economic model of commercial launches and debris accumulation in low-Earth orbit. Similar to carbon taxes, our model projects an optimal fee that rises at a rate of 14% per year, equal to roughly $235,000 per satellite-year in 2040. The long-run value of the satellite industry would more than quadruple by 2040-increasing from around $600 billion under business as usual to around $3 trillion. In contrast, we project that purely technological solutions are unlikely to fully address the problem of orbital congestion. Indeed, we find debris removal sometimes worsens economic damages from congestion by increasing launch incentives. In other sectors, addressing the tragedy of the commons has often been a game of catch-up with substantial social costs. The infant space industry can avert these costs before they escalate.

We are proposing a mission concept for Active Debris Removal (ADR) of multiple uncooperative debris targets from Low Earth Orbit, using a minisat spacecraft ("mothership") carrying several Coulomb Drag based Plasma Brake¹ modules. The Plasma Brake technology enables very high downmass/upmass ratios for debris deorbiting. In optimal conditions, the ratio for such a mission could be up to 60, representing a radical increase in ADR performance of 1-2 orders of magnitude compared to the current state-of-the-art ADR missions, and drastically improving the cost efficiency compared to one-object-per-mission approaches. The  Plasma Brake is especially competitive in the ~700-1200 km altitude range. The applicable debris mass limit of this deorbiting method is dictated by the demisability of the targets and is roughly 500 kg / Plasma brake unit. It provides a scalable, cost-effective method for reaching a net-zero space debris operations in the long term.The mission scenario consists of transfers between targets and a sequence of mothership operations repeated at each target: rendezvouz, detection, approach, de-tumbling of the target, attachment of a Plasma Brake module to the target. The critical core technologies needed to realize the mission, and are currently at low TRL, include:Sensors, actuators and algorithms required for the proximity operations used to approach and de-tumble the target object, Capture/attachment technologies for uncooperative targets like: kinematic structures, Hoberman sphere mechanisms, electrostatic adhesive, Adaptation of Plasma Brake concept to work with uncooperative targets, Framework for choosing the targets of a a multi-object touring mission that maximizes the downmass/upmass ratio, including the navigation scheme and navigation algorithms. Most ADR technologies so far are only viable for deorbiting large pieces of debris. The proposed system allows the effective deorbiting of much smaller pieces of debris as well, maintaining its effectiveness indefinitely to clean up the debris that is required by zero-debris targets.The mission concept and development of the critical core technologies needed for the mission to TRL 4 (testing prototypes in laboratory environment) have been proposed in EIC Pathfinder call of October 2024 by the authors.¹Janhunen, P., Electrostatic plasma brake for deorbiting a satellite, J. Prop. Power, 26, 370-372, 2010, https://arc.aiaa.org/doi/10.2514/1.47537

Summary form only given. Low Earth Orbit (LEO) is becoming increasingly populated by orbital debris of all sizes and shapes that is hazardous to operational spacecraft. NASA has recently determined that a collision with debris between 0.5 mm and a few centimeters would be "mission ending". Recently, a novel technique to remediate small debris (less than 10 cm) from Low Earth Orbit (600-1100 km) has been proposed that uses injected high mass density dust particles of 25-50 micron radius to collide with orbital debris, transfer momentum and thus lower the apogee of the debris to an altitude that will naturally decay quickly. The dust is injected at orbital velocities in a polar orbit at the top of an altitude range targeted to be cleared. The dust then forms a ring around the Earth that can continue to exchange momentum with orbital debris in its path. One of the keys to the efficiency of this method is the physics of a hypervelocity impact, in which a very high-pressure shock wave is generated that can fracture, melt, vaporize and ionize the material. This high-pressure material that is not in a condensed state is ejected from the debris at large velocity, in effect acting like retro-rockets and greatly enhancing the exchange of momentum. The efficiency of the momentum transfer is measured by a parameter κ which is 1 for inelastic collisions and 2 for elastic collisions. Assuming a relative impact velocity of 10-15 km/s (twice the orbital speed) and assuming that the melting of aluminum (a standard orbital debris material) is sufficient to eject material from the target orbital debris we can estimate a value of κ to be about 18. The amount of mass necessary to perform the remediation is inversely proportional to κ and hence a solid understanding of the physics of this parameter is critical. We use CTH simulations and analytical theory to calculate the parameter κ, the velocity of the ejecta, and estimate the amount of ionization to occur. We will comment on the creation of electromagnetic radiation created by the impact generated plasma and the potential applications of the radiation.

The sustainability of Outer Space in a context of increased human activity in low Earth orbit (“LEO”) has been much debated lately. The discussion focuses on how space debris appears, how they can be limited and, possibly, removed. Commercial proposals for Active Debris Removal (ADR) and providing life-extension services to satellites are slowly emerging as precursory technological tools. Those technologies will involve so-called on-orbit servicing activities (“OOS”), i.e., activities performed on a spacecraft, while it is in or near its operational orbit and will require that one spacecraft approach, rendezvous, and interact with the asset/the debris to be removed; they raise a host of legal, regulatory, and policy challenges that need to be discussed as those projects progressively mature. Those cutting-edge technologies have potent capabilities and a potential for military and missile technology applications. As a result, they will likely be controlled by export control regulations (possibly by US export control regulation) and might fall under the stringent ITAR requirements. OOS inevitably involves the coupling of two different actors, the servicing spacecraft performing the services, and the asset to service. From an export control perspective, depending on the circumstances of each mission, in particular on the nationality of the servicing spacecraft and the one of the debris, the exchange of information between them might qualify as an export of technical data and would need to be licensed and authorized accordingly. In addition, because of the coupling of those two actors, the OOS model presents an inherent complexity: it creates a greater risk of technical failures, in particular of on-orbit collisions. As a consequence, it can induce more opportunities to exchange technical data in a context of urgency that prompts omissions and ultimately, more opportunities for violating export controls. This would apply even if technical data are exchanged for insurance or investigation purposes. Thus, any situation of on-orbit failure in the context of an OOS presents a risk of inadvertent export control. In the past, inadequately managed launch-failure investigations of satellites launched on non-US launchers caused major export control violations and were to have a profound impact on the US export control system. After observing how technological measures can mitigate risks of export control violations, this paper will propose a normative suggestion to mitigate potential ITAR violations and to avoid inadvertent export control situations in case of on-orbit failures in the context of OOS.

The development of commercially viable ADR services: Introduction of a small-satellite grappling interface

Micrometeoroid/Orbital Debris (MMOD) Impact Detection and Location Using Fiber Optic Bragg Grating Sensing Technology

A well-known hazard associated with exposure to the space environment is the risk of failure due to an impact from a micrometeoroid and orbital debris (MMOD) particle. As NASA prepares to return astronauts to the moon with the Artemis program, the next generation of spacesuit known as the exploration extravehicular mobility unit (xEMU) is in development to support future extravehicular activities (EVAs). An MMOD impact to the spacesuit is of great concern to NASA as a large leak could prevent an astronaut from safely reaching an airlock in time resulting in a loss of life. In contrast to the legacy EMU, the xEMU must meet MMOD requirements for multiple environments including those in low earth orbit (LEO) as well as the meteoroid and secondary lunar regolith ejecta environments found on the lunar surface. The subject of this paper is an MMOD risk assessment of the internal xEMU configuration design developed by NASA Johnson Space Center (JSC) personnel. Assessment of the MMOD risk for an 8-hour, 2-person EVA in both LEO and on the lunar surface showed that the xEMU spacesuit meets the program technical requirement of 1 in 2500 failure odds.

The number of launches and objects in space has been growing fast in the last few years, particularly due to the growth of satellite mega-constellations. Defunct satellites and other space junk products collide and create a collisional cascade of smaller space debris. Space debris ablates and burns up in the atmosphere upon re-entry and thereby metals and rare materials are injected, some of which already exceed the natural input of exogenous material today.Quantifying the influx of these anthropogenic materials into the atmosphere is essential to address the possible environmental consequences, through constraining the physico-chemical atmospheric models. This quantification can be done using catalogs of spacecraft being launched, but not all manufacturers provide these data. Small micro-debris can be used as tracers of their larger counterparts through the collisional cascade, which would complement these existing catalogs, for the inventory of elemental compositions of human-made materials in Low EarthOrbit that will re-enter in the atmosphere.We propose in situ measurements of sub-micrometer and micrometer sized particles as tracers of the larger space debris, using in situ mass spectrometers with a velocity grid, that were originally designed for cosmic dust measurements.These instruments can measure the elemental composition (impact-speed dependent), mass distribution, surface charge, impact velocity vector, and time-resolved fluxes of dust and debris particles. Moreover, measuring the natural cosmic dust flux itself is necessary as a benchmark for the debris.In this talk we introduce in situ cosmic dust measurements in the past, the different measurement methods, and measurements of micrometer-sized space debris so far with “active” (time-resolved) and “passive” (sample return) methods. We elaborate on the particles we can expect to measure in orbit, and the science goals to be achieved through such measurements that are useful for both the assessment of the anthropogenic influx into the atmosphere and for space debris research in Low Earth Orbit. Elemental composition measurements of these micro-debris particles, combined with orbital velocity and location data, offer a new avenue for quantifying the chemical influx of anthropogenic material into Earth’s atmosphere, and for assessing more thoroughly the broader space debris populations.

Ground-based laser momentum transfer concept for debris collision avoidance

With the increasing congestion in orbital environments, on-orbit observation has become critical for spacecraft safety. This study investigated the observation performance of space-based inverse synthetic aperture lidar (ISAL) for monitoring on-orbit targets and space debris in geostationary Earth orbit (GEO) and low Earth orbit (LEO). Using STK simulations, the performances under fly-around and fly-by scenarios were evaluated based on three key parameters: minimum imaging time, pulse repetition frequency (PRF), and signal-to-noise ratio (SNR). The results reveal that while the GEO provided a high PRF and SNR for fly-around observations, longer imaging times limited its practical application, making the fly-by mode more suitable. In contrast, the LEO provided stable fly-around observations with lower system requirements, but the fly-by mode suffered from high PRF demands and a low SNR due to the high relative angular velocity of the target. This study further simulated fly-by observations for actual space debris in both the GEO and LEO, validating ISAL’s performance under different conditions. These findings offer valuable insights into the selection of observation modes and the optimization of ISAL’s performance in on-orbit target and debris monitoring, serving as a foundation for future space-based monitoring systems.

Space Debris Mitigation

An analytical theory for avoidance collision between space debris and operating satellites in LEO

Mitigation Rules Compliance in Low Earth Orbit

Space Sustainability: Reframing the Debate

To date, the International Space Station (ISS) has been one of the largest objects flown in lower earth orbit (LEO). The ISS utilizes high voltage solar arrays (160V) that are negatively grounded leading to pressurized elements that can float negatively with respect to the plasma. Because laboratory measurements indicate a dielectric breakdown potential difference of 80V, arcing could occur on the ISS structure. The paper identifies anodized aluminum surfaces, chromic acid and sulfuric acid anodized, on the ISS, which could arc due to plasma charging. An assessment of the effects of plasma-induced arcing on these ISS anodized surfaces, with and without concurrent micrometeoroid and orbital debris (MM/OD) impacts has been completed. The purpose of this study was to assess the loss of thermal control capability of the anodized surfaces on ISS if the Plasma Contactor Units (PCUs) were not continually operated as ISS is constructed and operated. The study considers six cases for the arcing Chromic Acid Anodized Aluminum (CAA) surfaces or Sulfuric Acid Anodized Aluminum (SAA) with no Micrometeoroid/Orbital Debris impacts (MM/OD), with MM/OD impacts that completely penetrated the anodize layer, and with MM/OD impacts that partially penetrated the anodize layer. The Marshall Space Flight Center (MSFC) performed analyses to provide the data giving the size and depth of penetration of MM/OD impacts. All six cases documented the thermal control properties of the anodized layers throughout the ISS life without PCU operations.