The dynamics associated with the jettisoning of a number of strap-ons from the parent launch vehicle is investigated. Three different models for the separation mechanisms are considered. Included in the analysis are forces due to the jettisoning mechanism along with the thrust on the core and the residual thrust on the strap-ons. Aerodynamic forces are, however, not considered. Geometry of collision in the multibody system is analyzed and three different criteria for detection of collisions are developed. The methodology is illustrated using two typical examples. The attitude motion of the controlled ongoing stage has been indirectly accounted for. Finally, a simple representation of the separation system is employed to construct a no-collision domain in the design parameter space.
The dynamics associated with the jettisoning of spent ullage rocket systems from the parent launch vehicle is investigated. The analysis considers a spring-based mechanism employed to jettison the system hinged on to an accelerating stage. Closed-form solutions are obtained. Analytical expressions are developed for the hinge reactions. Conditions are derived for optimum separation velocity and guidelines presented for selection of design parameters. The influence of residual thrust of ullage rockets on the separation process is examined and the expressions for its permissible value developed. a b E h /n/. Nomenclature = constant longitudinal acceleration of the thrusting stage = distance of the nozzle throat from the hinge (Fig. 1) = net stored spring energy -longitudinal distance between the spring and the hinge (Fig. 1) =X 3 -mass moment of inertia of the spent ullage system about the hinge, and its own mass center, respectively k = effective stiffness of the springs e = distance of the mass center from the hinge (Fig. 1) M = moment about the hinge due to the residual thrust m = mass of the spent ullage system M cl , M c2 , M c3 = critical values of the moments about the hinge, Eqs. (26), (30), and (34) M cl ,M c2 , M c3 = normalized critical values of the moments, M ci = lateral and longitudinal hinge reactions (Fig. 1) Rajeev Lochan graduated with a degree in mechanical engineering from BIT Sindri (Bihar), India, in 1973 and received his Master's in aeronautical engineering from the Indian Institute of Technology (IIT) Kanpur in 1976.He participated in the development of a trisonic wind tunnel at IIT Kanpur before joining Vikram Sarabhai Space Center (VSSC) Trivandrum, in 1977. Since then, he has been engaged in the research of diverse aspects of flight mechanics of launch vehicles. Dynamics of separating bodies, deployment dynamics, boost phase guidance, and onboard algorithms for position and attitude determination are some of the areas where he has made contributions.
The dynamics associated with the jettisoning of heat shield fairings from the parent launch vehicle is investigated. The analysis considers a zip-cord based mechanism employed to jettison the fairings from the accelerating on-going stage. A scheme for characterization of the zip-cord system is described. The geometry of collision is analysed for a known, precomputed structural response. The nocollision domain is constructed in flexibility parameter space for an arbitrarily assumed impulse level. Alternatively, the minimum impulse required for a collision-free separation is also computed as a function of design parameters. Finally, the analysis enables generation of the upper limits on payload size as well as that of the external mountings for a clean separation. This methodology has led to the successful separation of shield heat fairings for the two developmental flights of the Indian launcher Polar Satellite Launch Vehicle (PSLV).
The jettisoning of a nose cone in space from a spinning rocket has been investigated. The spring-assisted separation system is described with its mathematical model. The resulting nonlinear equations have been integrated numerically. The geometry for safe separation has been analysed and the in¯uences of various imperfections in the system, such as dynamic asymmetry, dynamic imbalance, separation system imperfections, etc., are studied. The analysis presented here enables a clear understanding to be obtained of the separation dynamics of a nose cone in a spinning environment. A closed-form solution has been obtained for the relative motion between the separating dynamically symmetric bodies devoid of any dynamic imbalance under the in¯uence of a perfect separation system. For the same system, simple design formulae have also been derived for collision avoidance, which can be gainfully utilized for initial sizing of separation systems.
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