Carsten Wiedemann

MASTER-2005 - The Debris Risk Assessment Tool for the Space Industry

The Meteoroid and Space Debris Terrestrial Environment Reference Model of the Euro- pean Space Agency, ESA-MASTER, has been developed to its next release, MASTER-2005. The Institute of Aerospace Systems at the Technische Universitat Braunschweig has been the main contractor for this project. In order to deliver results that can be used for risk analysis such as debris fluxes and spatial densities, and to ensure their credibility, a number of steps were undertaken. The first step was the initial definition of the orbital debris envi- ronment between 1957 and 2005. Based on models describing the properties of all known sources of orbital debris, combined with a database of known debris generating events, the development of the space debris population throughout this period was simulated, covering objects down to one micron diameter. The debris source models were a major point of activity in the project, as for almost all of them major changes have been implemented, based on the current state of knowledge. The purpose of MASTER is the characterization of the natural and the man-made particulate environ- ment of the Earth, and the fast and simple evaluation of the resulting effects on space missions. The model is based on a semi-deterministic analysis of a reference population derived from the simulation of all major space debris source terms. Meteoroids, as the natural component of the Earth particulate environment, are modelled according to state-of-the-art approaches for both, the sporadic background component and the meteoroid streams. MASTER consists of a flux and spatial density prediction tool which combines a quick assessment of spatial density characteristics with high resolution flux results and additional analytical capabilities. The MASTER application is shipped together with an easy-to-use Graphical User Interface (GUI) and online documentation on a single DVD. The model can be installed and executed on a broad variety of platforms (SUN Solaris, Linux, Windows, and MacOS). For each simulated debris source, a corresponding generation model in terms of mass/diameter distri- bution, additional velocities, and directional spreading has been developed. A comprehensive perturbation model was used to propagate all objects to a number of snapshot epochs. In addition, objects larger than 1mm are simulated into the future based on three different scenarios. Currently, apart from spent payloads and upper stages (launch/mission related objects background - LMRO), MASTER considers fragmentations from on-orbit explosions and collisions, dust and slag from Solid Rocket Motor (SRM) firings, sodium-potassium (NaK) coolant droplets from RORSAT satellites, surface degradation particles (paint flakes), ejecta and West Ford needles (as part of the LMRO population). In order to describe the steady state natural meteoroid environment, the Divine-Staubach meteoroid model is implemented into MASTER. This model considers 5 distinct families of meteoroids and is available

The consideration of non fragmentation debris in the master model

Abstract The 1997 MASTER model (ESAs meteoroid and space debris terrestrial reference) considers man made objects due to historical launches and fragmentation debris larger than 100 μm . This paper addresses the improvements of the MASTER model by consideration of also non-fragmentation debris down to 1 μm in diameter. For this purpose, debris generated by solid rocket motor firings, surface degradation particles, impact ejecta, and NaK droplets released by nuclear reactors in space are currently being implemented in the model. All debris sources are considered from LEO up to the geosynchronous region. The new MASTER debris population is analysed in terms of the spatial distribution and resulting object flux, and it is compared with measurement data. Although the number of man-made objects represented in the model has been increased significantly, it is shown that the required resources to run the model are acceptable in terms of computer time and storage. The new model architecture, especially the parametric source term description, enables effective maintenance and model upgrade in response to ongoing debris measurements and source model improvements. The user branch of the MASTER model now provides a graphical interface for all platforms supported.

Identification of Solid Rocket Motor Retro-Burns in the LDEF IDE Impact Data

The Interplanetary Dust Experiment (IDE) carried by the Long Duration Exposure Facility (LDEF) satellite detected a large amount of impact events recurring for a number of LDEF orbits. Such events show signatures of particle clouds that intersect the orbit of LDEF. In an effort to identify the impact of particles released during specific solid rocket motor burns, a new look at the IDE impact records was taken. The generation of dust particles due to solid rocket burns and the orbit conjunction of the released objects with LDEF was simulated. For the first time, an agreement of specific IDE impact features with the re-entry firings of Russian photo-reconnaissance satellites could be derived.

Prediction of the Space Debris Particle Flux on Satellite Surfaces using MASTER-2005

This paper gives the results of a debris and meteor oid flux analysis for satellites on different orbits. The goal is to combine a particle impact risk analysis with an estimation of the penetration probability for selected wall de signs. The impact probability is a result of the flux of debris objects on a certain o rbit and the meteoroid background flux. For the determination of the orbital debris flux, t he European MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) model is used. The latest version of the model, MASTER-2005, was developed by a consortium under ESA/ESOC (European Space Operation Centre) contract. The consortium was led by the Institute of Aerospace Systems of the Technische Universitat Braunschweig (Germany). MASTER- 2005 was developed in cooperation with QinetiQ (UK), supported by Forschungsgesellschaft fur Angewandte Naturwissenschaften FGAN (Germany) and Astronomisches Institut Universitat Bern AIUB (Switzerland). MASTER-2005 is based on a validated debris population, considering all p articles on Earth orbits with diameters greater than 1 µm. The model considers all relevant sources like fragments, sodium-potassium (NaK) droplets, solid rocket motor (SRM) slag particles and Al 2O3 dust, ejecta, paint flakes and natural meteoroids. Impacts of space debris objects can damage satellites. Penetrating particles can cause failures or even the loss of a spacecraft. To prevent damages, it is useful to pro tect the satellite against particle impacts. In this case it is necessary to modify the satellite wall. To control the number of penetrations it may be useful to vary the spacing b etween the sheets of the honeycomb structure of the satellite hull. Using ballistic li mit equations, the minimum penetrating projectile diameter can be calculated. If the spaci ng is increased, the number of penetrations is significantly reduced. In GEO the n umber of impacts and penetrations is much lower than in LEO. The results are presented in terms of number of impacts and penetrations per area and year.

A Model for the High Area-to-Mass Ratio Debris in GEO

Recent observations performed using the ESA Space Debris Telescope (ESA-SDT) in Tenerife, Spain have revealed a new type of orbital debris. These objects with an area-tomass ratio of up to 30 m 2 /kg are currently not included in debris models like MASTER-2005. Their diameters are in the order of tens of centimeters. In this paper, a first approach to a new debris source model for the type of debris discovered during the ESA-SDT observations will be presented. The model will describe the parameters of the observable high area-tomass ratio objects that can be generated by two types of events. The first is a delamination of thermal insulation material from a spacecraft. The second type of event is a spacecraft fragmentation. The investigation of the design of candidate spacecraft can provide the first parameters of a model. These can be used to determine the overall size distribution of the released insulation material for both types of events. After an implementation of the model and a simulation that takes into account the orbit distribution and evolution of candidate spacecraft, a new debris population can be simulated.

Modelling the Meteoroid Stream Flux onto Targets in Earth Orbits

In contrast to the highly dynamic space debris environment, the annual mean meteoroid environment can be assumed to be static. However, the activity during the year consists of a superposition of a sporadic background flux with a number of seasonally recurring meteoroid streams. The damage potential of these mainly very small particles results from their high relative velocities (more than 70 km/s) and the resulting kinetic energy. Thus, it is important to analyse the effects of the meteoroid streams on targets in Earth-bound orbits. This paper describes the model approach that is used in ESA-MASTER-2005 (Meteoroid and Space Debris Terrestrial Environment Reference) to account for the meteoroid stream flux. It gives flux predictions for a set of targets in different Earth orbits and compares the stream flux against the meteoroid background and debris flux.

Cost of Space Debris Impacts on a LEO Satellite

The goal of this paper is to combine debris impact risk analysis with cost estimations. Impacts of space debris objects can damage satellites. These damages can cause failures or even the loss of a spacecraft. The loss of a satellite reduces its expected useful lifetime. As a result, financial investments cannot be amortized completely. This loss of amortization causes cost. To prevent damages, it may be useful to protect the satellite against debris impacts. To achieve this, it is necessary to modify the satellite. This causes increased development and production effort. Consequently damages as well as mitigation measures can produce additional cost. In this paper a procedure for a rough estimation of the order of magnitude of debris related risk and cost is presented. An important task is the determination of the impact probability and the number of impacts during a mission. The impact probability is a result of the flux of debris objects on a certain orbit. For the determination of the orbital debris flux the MASTER 2001 model is used. MASTER (Meteoroid and Space Debris Terrestrial Reference model) is the European model for estimating the risk of hypervelocity impacts on satellites. MASTER is based on a very complex model of the space debris environment in terms of spatial density and velocity distribution. It is based on quasi-deterministic principles, using comprehensive orbit propagation theories and volume discretization techniques, to derive spatial density and velocity distributions in a three-dimensional control volume ranging from Low Earth Orbits (LEO) to the Geo-stationary Orbit (GEO) altitudes. In the course of this paper cost models are derived for satellite missions, satellite damages due to debris impacts, and shielding. The definition of a standard satellite is made by a rough sizing of a spacecraft, based on mass models of its subsystems. The model gives the properties of a typical satellite with a certain Beginning Of Life (BOL) mass. The model includes an estimation of typical satellite dimensions. A flux analysis using the MASTER model is made for a selected Low Earth Orbit. Penetrations of the satellite hull are calculated by the use of damage equations. A risk analysis is made by combining the probability of a penetration with the failure probability of the satellite. The cost estimation comprises the loss of amortization and the additional effort for satellite protection. The results are shown for a reference mission of a LEO satellite.

Improvements in Modelling of Solid Rocket Motor Particle Release Events

The ESA space debris population model MASTER-2001 (Meteoroid and Space Debris Terrestrial Environment Reference) considers 1,032 firings of solid rocket motors (SRM) with the associated generation of SRM slag and dust particles in its current version. The resulting particle population is a major contribution to the space debris environment in Earth orbit. For the modelling of each particle release event a detailed knowledge of the size distribution is essential. However, the knowledge of the particle sizes after passing the motor nozzle throat is poor. The current SRM dust implementation in the MASTER model assumes a fixed size distribution which is identically used for both large upper stages and small apogee motors. This assumption can lead to an over-representation of large dust particles in regions where mainly apogee motors are used (i.e. GEO), and an under-representation in lower altitudes where large stages predominate. In this paper, a concept for the improvement of SRM particle size modelling is discussed based on validation results with impact measurements obtained from space returned hardware. It will be shown that an introduction of a nozzle throat diameter dependency into the size distributions for both dust and slag enables a more precise modelling of SRM particle release events. The improved size distributions are going to be used by the MASTER-2005 space debris model which is currently under development by the Institute of Aerospace Systems and QinetiQ (UK) under ESA contract.