Chaotic Behavior of the Biharmonic Dynamics System
Motion of a biharmonic system under action of small periodic force and small damped force is studied. The biharmonic oscillator is a physical system acting under a biharmonic force like . The article contains biharmonic oscillator analysis, phase space research, and analytic solutions for separatrixes. The biharmonic oscillator performs chaotic motion near separatrixes under small perturbations. Melnikov method gives analytical criterion for heteroclinic chaos in terms of system parameters. A transition from chaotic to regular motion of the biharmonic oscillator was found as the heteroclinic chaos can be removed by increasing the coefficient of a damping force. The analytical results obtained using Melnikov method have been confirmed by a good match with numeric research.
Planetary protection for Mars Sample Return
Abstract A Mars sample return (MSR) mission must deal with two new categories of planetary protection requirements: (1) assuring a very low probability of inadvertent release of the sample in order to provide extra protection against the extremely unlikely possibility of biological hazards in the returned material and (2) keeping the samples free of round-trip Earth organisms to facilitate confirmation of safety after return to Earth. This paper describes the planetary-protection-related technical challenges awaiting an MSR mission as well as the range of capabilities being developed to meet these challenges. Containment assurance requires breaking the chain of contact with Mars: the exterior of the sample container must not be contaminated with Mars material. The sample container and its seals must be designed to survive Earth impacts corresponding to the candidate mission profiles, and the Earth entry vehicle must be designed to withstand the thermal and structural rigors of Earth atmosphere entry (all with an unprecedented degree of confidence). Sample contamination must be avoided by sterilizing the entire spacecraft, a challenge with modern avionics, or by sterilizing the sample collection and containment gear and then isolating it from other parts of the spacecraft.
Temporal adaptive Euler/Navier-Stokes algorithm involving unstructured dynamic meshes
A temporal adaptive algorithm for the time integration of the two-dimensional Euler or Navier-Stokes equations is presented. The flow solver involves an upwind flux-split spatial discretization for the convective terms and central differencing for the shear-stress and heat flux terms on an unstructured mesh of triangles. The temporal-adaptive algorithm is a time-accurate integration procedure that allows flows with high spatial and temporal gradients to be computed efficiently by advancing each grid cell near its maximum allowable time step