1,721,344 research outputs found
Orbit design for future SpaceChip swarm missions in a planetary atmosphere
No full textThe effect of solar radiation pressure and atmospheric drag on the orbital dynamics of satellites-on-a-chip (SpaceChips) is exploited to design equatorial long-lived orbits about the oblate Earth. The orbit energy gain due to asymmetric solar radiation pressure, considering the Earth's shadow, is used to balance the energy loss due to atmospheric drag. Future missions for a swarm of SpaceChips are proposed, where a number of small devices are released from a conventional spacecraft to perform spatially distributed measurements of the conditions in the ionosphere and exosphere. It is shown that the orbit lifetime can be extended and indeed selected through solar radiation pressure and the end-of-life re-entry of the swarm can be ensured, by exploiting atmospheric drag
Long-Term Evolution of Highly-Elliptical Orbits: Luni-Solar Perturbation Effects for Stability and Re-entry
Full text linkThis paper investigates the long-term evolution of spacecraft in Highly Elliptical Orbits (HEOs). The single averaged disturbing potential due to luni-solar perturbations, zonal harmonics of the Earth gravity field is written in mean Keplerian elements. The double averaged potential is also derived in the Earth-centered equatorial system. Maps of long-term orbit evolution are constructed by measuring the maximum variation of the orbit eccentricity to identify conditions for quasi-frozen, long-lived libration orbits, or initial orbit conditions that naturally evolve toward re-entry in the Earth's atmosphere. The behavior of these long-term orbit maps is studied for increasing values of the initial orbit inclination and argument of the perigee with respect to the Moon's orbital plane. In addition, to allow meeting specific mission constraints, quasi-frozen orbits can be selected as graveyard orbits for the end-of-life of HEO missions, in the case re-entry option cannot be achieved due to propellant constraints. On the opposite side, unstable conditions can be exploited to target Earth re-entry at the end-of-mission
End-of-life disposal of geosynchronous satellites
No full textEnd-of-life disposal of spacecraft in the GEO region is required for the further exploitation of this particularly important orbital regime. The orbital dynamics around the geostationary ring can be exploited for designing graveyard orbits or looking for re-entry solutions. Here we present an end-of-life trajectory design method based on a detailed cartography of the orbital space. Given a post-mission orbit of a decommissioned satellite and the available fuel on board, efficient two-burn transfers are calculated for each reachable orbit on the grid. Furthermore, an analysis of cost (delta-v) versus stability of target orbit or re-entry time is performed by means of finding the Pareto optimal solutions for each case
Orbital dynamics of "smart dust" devices with solar radiation pressure and drag
No full textThis paper investigates how perturbations due to asymmetric solar radiation pressure, in the presence of Earth shadow, and atmospheric drag can be balanced to obtain long-lived Earth centred orbits for swarms of micro-scale 'smart dust' devices, without the use of active control. The secular variation of Keplerian elements is expressed analytically through an averaging technique. Families of solutions are then identified where Sun-synchronous apse-line precession is achieved passively to maintain asymmetric solar radiation pressure. The long-term orbit evolution is characterized by librational motion, progressively decaying due to the non-conservative effect of atmospheric drag. Long-lived orbits can then be designed through the interaction of energy gain from asymmetric solar radiation pressure and energy dissipation due to drag. In this way, the usual short drag lifetime of such high area-to-mass spacecraft can be greatly extended (and indeed selected). In addition, the effect of atmospheric drag can be exploited to ensure the rapid end-of-life decay of such devices, thus preventing long-lived orbit debris
Deorbiting spacecraft with passively stabilised attitude using a simplified quasi-rhombic-pyramid sail
Full text linkThis paper studies deorbiting using an analogue to the quasi-rhombic-pyramid concept for planar motion. The focus is on maintaining a stable (meaning oscillatory) attitude close to the direction of the velocity of the spacecraft relative to the atmosphere. The study consists of a massive computation of deorbit times chosen in a region of the phase space where atmospheric drag plays a leading role. Here, no damping effects are considered. Thus, any passive stabilisation observed is either due to solar radiation pressure or atmospheric drag. The results show that such stable deorbiting is feasible up to a threshold that depends upon the physical parameters of the sail. This threshold is around 500 km of altitude. Stable deorbiting is also shown to reduce the unpredictability that appears due to tumbling
Transformation of Satellite Breakup Distribution for Probabilistic Orbital Collision Hazard Analysis
Full text linkFragmentation clouds from explosions or collision of payloads and rocket bodies in space pose a threat to objects in Earth orbit. Most of the fragments are too small to be tracked and can only be accounted for statistically. Here, a framework for the fully statistical treatment of a fragmentation cloud, its evolution and ramifications, without the need of simplifying assumptions, is presented. The cloud is modeled as an uncertainty around a single fragment, which can be propagated using any of the existing, nondeterministic, nonlinear orbital uncertainty propagation methods. This work is focused on providing the initial distribution and the estimation of the statistical collision probability. The NASA standard breakup model is revisited to derive a probability distribution of the initial fragment cloud. Two density transformation methods are discussed to obtain the distribution in a subset of orbital elements, suitable for mid-to long-term evolution. The fragment spatial density and the impact rates on targets in any orbit are obtained. The method is applied to show the fragment cloud distribution of a payload collision in low Earth orbit (LEO). Its collision probability with a satellite in LEO and a rocket body in the geostationary transfer orbit are estimated. The result is compared against, and shows the limitations of, sampling and methods based on finite differences
Long-term evolution of highly-elliptical orbits: luni-solar perturbation effects for stability and re-entry
No full textThis paper investigates the long-term evolution of spacecraft in Highly Elliptical Orbits (HEOs). The single averaged disturbing potential due to luni-solar perturbations and zonal harmonics of the Earth gravity field is written. The double averaged potential is also derived in the Earth-centered equatorial system. Maps of long-term evolution are constructed to identify conditions for quasi-frozen, or long-lived libration orbits. In addition to allow meeting specific mission constraints, quasi-frozen orbits can be selected as graveyard orbits for the end-of-life of HEO missions. On the opposite side, unstable conditions can be exploited to target an Earth re-entry at the end-of-mission
Propagation and Reconstruction of Reentry Uncertainties Using Continuity Equation and Simplicial Interpolation
Full text linkThis Paper proposes a continuum-based approach for the propagation of uncertainties in the initial conditions and parameters for the analysis and prediction of spacecraft reentries. Using the continuity equation together with the reentry dynamics, the joint probability distribution of the uncertainties is propagated in time for specific sampled points. At each time instant, the joint probability distribution function is then reconstructed from the scattered data using a gradient-enhanced linear interpolation based on a simplicial representation of the state space. Uncertainties in the initial conditions at reentry and in the ballistic coefficient for three representative test cases are considered: a three-state and a six-state steep Earth reentry and a six-state unguided lifting entry at Mars. The Paper shows the comparison of the proposed method with Monte Carlo–based techniques in terms of quality of the obtained marginal distributions and runtime as a function of the number of samples used. © AIAA International. All rights reserved
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