Pneumatic sensing-line nonlinear model.

Abstract

Fig. 1 Shower zones on the ecliptic plane associated with known short-period comets. The dots are in approximate scale to the suggested shower zone size. For illustrative purposes, representations of Earth and Mars orbits are also shown.while at the descending node V = (TT -co). Calculated times of the next comet-ecliptic plane intersections are also presented in Table 1 together with the comet period. From these data it is rather straightforward to apply definition (3) of the proposed meteoroid stream model and generate danger time intervals during which short-period comet shower zones are active. Hazard EvaluationBecause the flux in the shower zone is only vaguely known, it is recommended that, for any mission analysis, the mission trajectory first be checked to see if it will intersect any known active shower zone. If it will, then change of the trajectory should be considered. The probability that it will may be approximated by the ratio of the average total area of the active shower zones compared to the total ecliptic plane area under consideration. This probability is, for example, only 1.07% for the 55 shower zones on the ecliptic plane inside the orbit of Mars.An alternative solution is to adopt a maximum flux for the shower zone, compute the passage time through the zone, and then determine the spacecraft hazard using conventional analysis methods. In this way, stream danger zone effects on the spacecraft can be considered along with the effects of sporadic cometary and asteroidal meteoroid environments. This approach may, however, result in increasing the spacecraft's flux exposure (flux-area-time-product) to levels making design difficult. For example, if the relative maximum flux encountered in a condensation is 10 3 times the sporadic nearEarth flux, then a spacecraft would receive in 525 min the same flux exposure it would receive in one year of operation in the meteoroid environment near Earth.