Research On Space Debris Environment Model

The dissertation mainly focuses on the theory and application about space debris environment model, the main works and contributions are summarized as follows:1,On the basis of historical launches analysis, evolution and current space debris environment is discussed. The distribution of semimajor axis, eccentricities and inclination of the cataloged space objects orbit is analyzed. And the result is that the majority of space objects are in the high inclination and near-circular orbits, with peak concentrations in low-Earth orbits, at altitudes below 2,000km, in the orbits of semi-synchronous about 12-hour periods, and in the geostationary ring.2,The system of space debris envrionment model is established, including debris source models, current space debris envrionment assessment, prediction of future space debris environment and effects of debris mitigation measures.3,On the basis of research of the generation process of space debris by various source terms, the breakup model, solid rocket motor firings model, NaK coolant droplets release model, West-Ford needles model and ejecta model are established and analyzed in detail.4,NASA standard breakup model turned out to have a shortcoming in the representation of the particles'area-to-mass ratio for fragments in the submillimetre regime. On the basis of theoretic analysis, this shortcoming has been corrected.5,According to the laws of kinetic gas theory, the expression of impact probability of space objects is given. Spatial density and flux of space debris based on volume discretization is discussed. And collision geometries of space debris are analyzed.6,The spatial density of space debris is calculated and analyzed. Peak concentrations in LEO regime are at altitude shells between 750km and 1000km, and near 1450km. In the super-LEO regime, peak concentrations are in the orbits of semi-synchronous ~12-hour periods, and in the geostationary ring.7,For the LEO regime two sample orbits are used to sense space debris environment: one is the orbit of the International Space Station (ISS), the other is the orbit of ESA's ENVISAT satellite. And the flux on the orbit of BEIDOU 1A satellite is calculated and analyzed for the geostationary ring.8,Two different types of future launch traffic model are studied: the steady-state model and the mission model.9,The steady-state model is based on the assumption that the historical launch activity of the past few years is typical of future activity, with a constant, average overall launch rate. After the historical launch activities analysis, business-as-usual (BAU) forcast scenario is defined. For BAU scenario, the number and the spatial density of the cataloged objects after fifty years is calculated. A near-linear increase can be observed, and the total number is 2 to 3 times the current number. 10,The mission model is purely based on estimates of the future uses of space such as new technology, new launchers, new space architectures, and speculations of civil, military, and commercial objectives and benefits. The research based on mission model revealed that the long-term evolution of space debris environment is sensitive to variations of traffic rate. The deployment of satellite constellations and nano-satellite swarms in narrow altitude and inclination bands can strongly increase local spatial densities and collision risk levels.11,The effective debris mitigation measures in view of operational, technical, and economic feasibility versus improvements in environmental stability are as follows:·prevention of on-orbit explosions·reduction of mission-related objects·collision avoidance between trackable objects·post-mission disposal of space systems12,The effectiveness of debris mitigation measures is studied. Each mitigation measure can reduce the absolute growth of potentially hazardous objects, but a trend towards increasing growth rates is maintained, indicating that single mitigation measure is a necessary but not sufficient condition to provide a stable space debris environment for future generations.However, if full mitigation is applied, the space debris environment in LEO can reach a stable level, with no growth of total population, despite continuing space operations at present deployment rates.