Sensitivity studies of the deployment of a square inflatable solar sail with vanes

This paper summarizes the results of numerical experiments to determine the sensitivity of the final attitude of an inflatable solar sail with vanes after deployment to various parameters affecting the deployment process. These parameters are: in- and out-of-plane asymmetries during deployment, length inflation profile, and vane deployment failures. We show how robust the sail deployment is to geometric asymmetries before a 35° off-Sun angle is reached. Differential delays in the time to inflate the booms and a boom sweep-back angle affect the stability favorably. Adjacent vane failures to deploy affect the stability unfavorably, while the failure of opposing vanes is acceptable. Realistic boom length rate profiles obtained during ground tests are used in the simulation showing that failing adjacent vanes in conjunction with initial inflation delays in adjacent booms represent the worst case. We also demonstrate that by feeding back attitude and attitude rate measurements so that a corrective action is taken during the deployment, the final attitude can be maintained very close to the initial attitude, thus mitigating the attitude changes incurred during deployment.     

The Initial Stage of “Space Debris” Cloud Formation during Planetary Satellite Breakdown

The process of formation of a particles cloud (space debris) during breakdown of the Earth’s Artificial Satellite (EAS) is considered. A system of equations of motion is derived, and its analytical solution in the linear approximation for circular orbits is presented. The distinction between this solution and an exact numerical solution is indicated. The cases of satellite breakdown at the apogee and perigee on an elliptic orbit are also considered, and some characteristics of these processes are compared.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 4, 2005, pp. 269–273.Original Russian Text Copyright © 2005 by Gorelov, Zarubkin.     

Deformation of the Envelope of a Broadband Signal during Propagation through the Martian Ionosphere

The regularities of propagation along the spacecraft-Martian surface-spacecraft path of a broadband Gaussian pulse in the condition of its dispersion distortions are considered in application to the problem of radiowave pulse sounding of the near-surface soil of Mars from onboard a satellite. The Martian night-side ionosphere reduces the energy considerably but does not lead to any distortion of the pulse envelope. At the sounding of a two-layer surface, the ionosphere influence, together with the signal absorption, manifests as the lower limit of the thickness of the upper layer reached for measurements in the scope of the planned experiment [1].     

Structural optimization of lifting surfaces with regard to static aeroelasticity

A technique for choosing a rational load-carrying scheme and weight analysis at the early stages of designing lifting surfaces with the use of a special model of the finite element method is proposed. The distribution of structure loads is determined with regard for its deformation. The numerical example is presented.     

Alternative statements of optimal load-bearing structure design problems

We analyze the well-known statements of optimal design problems for load-bearing maximum rigidity structures in which a principle of the minimum of total potential energy of structure deformation is used. A version of the generalized statement of optimization problems for processes described by linear equations with a symmetric operator is proposed. On the basis of the version outlined, we present a mathematical algorithm for obtaining beam structures of maximum rigidity, in which the finite element method is used to solve an analytical problem. We give the numerical results of solving two problems of optimal design of maximum rigidity structures that are simulated by cantilever and statically indeterminate beams.     

The use of solutions to problems of spacecraft trajectory optimization in impulse formulation when solving the problems of optimal control of trajectories of a spacecraft with limited thrust engine: II

As examples of application of the technique suggested in the first part of this work, the problems of optimizing the trajectories of spacecraft transfers between circular coplanar orbits are considered in this second part. During the transfer the spacecraft is controlled by the vector of thrust of a limited-thrust jet engine. The mass consumption is minimized for a limited time of transfer. Extreme trajectories with two and three powered sections (Homan-type and bi-elliptic transfer trajectories) are numerically determined. The solution of these well-studied problems allows one to compare the results of applying the suggested technique with the results of application of other previously used techniques.     

Internal Gravitational Field of a Thin Homogeneous Ring

The potential of gravity forces is found inside a thin homogeneous ring when the ring’s mean radius is much larger than the diameter of its cross section. Rings with elliptic and almost circular cross sections are considered.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 4, 2005, pp. 260–268.Original Russian Text Copyright © 2005 by Kasatkin.     

Parameters of a creasing-bending machine as applied to the scheme of transverse rotary shaping of chevron structures

Based on the topological representation and transformation of the elementary chevron structure module, we propose the dependences that relate the geometrical parameters of rollers with the chevron structure element sizes for the transverse scheme of rotary creasing and bending. The calculation scheme is realized in the form of the parametrized geometrical model using CAD SolidWorks aids.     

An algorithm for solving three-dimensional problem of elasticity theory for transversally isotropic medium

An algorithm for solving a boundary-value problem of deforming structures made of composite materials is considered. The polynomial solutions of the equation system for the linear theory of elasticity for the anisotropic medium in displacements are used in this algorithm.