Advanced Flight Management System for an Unmanned Reusable Space Vehicle

Abstract

Advanced flight management system for an unmanned reusable space vehicle. International Journal of Unmanned Systems Engineering. 1(3): 48-67. The innovative architecture of an advanced Flight Management System (FMS) for Unmanned Reusable Space Vehicle (URSV) applications is presented with the associated re-entry trajectory computation algorithm. The SL-12 unmanned space vehicle, developed by Cranfield University as a part of the 2012-2013 Aerospace Vehicle Design (AVD) Group Design Project (GDP) is used as the reference platform. The overall avionics architecture of the future space transportation vehicle is described. A detailed architecture is developed for the FMS and the core functions of such an FMS are described. A dedicated computation algorithm is presented for re-entry trajectory planning, which involves determination of the path of re-entry vehicle by means of angle of attack and bank angle modulation. Simulation case studies are performed in a realistic re-entry operational scenario resulting in the generation of efficient and feasible trajectories, without violating any of the defined constraints.

Flight Management System for Unmanned Reusable Space Vehicle Atmospheric and Re-Entry Trajectory Optimisation

“…The nominal re-entry phase of the URSV [9] begins at an altitude of around 120 km with a target speed of around Mach 25. The excessive energy is dissipated in order to attain the TAEM interface at the specified conditions.…”

“…where 'Q ' is the max heat flux in W/m , 'n ' is the max g-load factor, 'L' and 'D' are the lift and drag aerodynamic accelerationsin m/s . The lower boundary of the corridor is given by the steady glide equilibrium and the higher boundary is given by the lower of the following maximum drag accelerations [9] expressed as:…”

“…where 'q ' is the maximum dynamic pressure in N/m , 'S'is the wing reference area in m , 'C ' is the lift coefficient, 'C ' is the drag coefficient, 'm' is the mass of the vehicle in kg and 'g' is the acceleration due to gravity in m/s 2 . The constant 'C' is given by [9]:…”

“…where 'ρ ' is the Atmospheric density at sea level in kg/m and 'R 'is the vehicle nose radius in m. A reference drag-acceleration profile is then generated such that the URSV lies within the entry corridor and takes into account a specified trajectory length. A 3-segment linear profile is adopted for the reference drag acceleration profile [9], where D 1 (E), D 2 (E) and D 3 (E) are the three drag segments. D and D are initial and final values of drag acceleration, respectively.…”

“…By assuming an initial estimate of the trajectory length, the only unknown variable in the above equation is D , which is obtained by using secant method [9]. Most of re-entry algorithms assume a determined α profile.…”