Renewed interest in re-usable launch vehicles has led to the evolution of technology demonstration concepts, where the prime objective is to demonstrate new technologies at reduced cost and shorter turnaround time. This article presents details of both ascent and descent mission design of a low-cost Reusable Launch Vehicle Technology Demonstration (RLV-TD) programme. The technology demonstrator vehicle is boosted to hypersonic Mach number using a solid booster. During ascent phase, the vehicle was flown in a gravity turn trajectory to minimize structural loads on it. In the descent phase, an optimum angle of attack profile as a function of Mach number was computed to limit dynamic pressure, load factor and achieve vehicle trim with minimum control surface deflection. The mission design parameters were evaluated using Monte Carlo analysis utilizing six degrees of freedom simulations. Comparison of actual flight performance with pre-flight prediction is also made this article. Flight performance exhibits close match with the pre-flight predictions.
A numerical tool is developed for the design and analysis of Mars atmospheric entry trajectories. Simple latitude dependent density model is employed along with an approximate temperature model for Mars' atmosphere. Radiative heat flux and convective heat flux (with cold wall boundary condition) relations are used for the study of stagnation point heating. Approximate drag profile of Mars Pathfinder is used for most simulations. Effects of non-spherical gravity and Mars' surface elevation considerations are discussed in brief. De-orbit thrusting, direct entry, lifting entry, parachute deployment, heat shield release and terminal descent thrusting scenarios are also incorporated into the tool, and their design characteristics are studied. Advantages of lifting entry and the necessity for parachute deployment and terminal descent thrusting are discussed. Different direct entry scenarios are analyzed within feasible launch windows for a typical Mars mission. NOMENCLATURE AND CONSTANTSD = Drag force on the module I sp = Specific impulse of thruster J 2 = Zonal gravity coefficient for Mars = 0.001964 L = Lift force on the module L/D = Lift to Drag ratio R = Equatorial radius of Mars = 3397 km T = Thrust force on the module g 0 = Gravitational acceleration on Earth surface = 9.80665 m/s 2 g r = Radial component of gravity g φ = Latitudinal component of gravity m = Mass of the module r = Radial distance of the module from the centre of Mars t = Time v = Velocity of the module α = Angle of attack of module β = Bank angle of module γ = Flight path angle (FPA) δ, ϕ = Mars-centric latitude λ = Mars-centric longitude (+ towards east) µ = Gravitational constant of Mars = 42828 km 3 /s 2 ρ = Density of atmosphere ψ = Flight azimuth (+ clockwise from north) ω M = Mars rotation rate = 7.101171898 × 10 −5 rad/s Characteristic gas constant = 191.8 J/kg/K Ratio of specific heats = 1.289 dof -Degree of Freedom MPF -MARS PATHFINDER INTRODUCTION "The earth is the cradle of humankind, but one cannot live in the cradle forever."-Konstantin Tsiolkovsky The interest in planetary exploration, mainly the exploration of Mars, has greatly increased in recent times, largely due to the advancements in space technology. So far fourteen attempts have been made by different agencies to land on the surface of the red planet. The United States has successfully landed 5 robotic systems on the Mars surface till date. These were part of Viking I and II, Pathfinder and Mars Exploration Rover (Spirit and Opportunity) missions. All these missions had landed masses below 600 kg. For further larger scale missions, the landing mass capability has to be increased to several tonnes or more [1]. Available literature points out that, entry systems with ballistic coefficients greater than 50 kg/m 2 cannot decelerate payloads to subsonic conditions at the Martian surface without the help of additional decelerators like supersonic parachutes, terminal descent thrusters, or airbags. These requirements and several other factors like the thin atmosphere, uneven terrai...
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