Space-Plane Analysis: A trajectory generation and sensitivity analysis.

In February 1993 the Advanced Earth to Orbit Launcher Upgrade Studies (AEOLUS) have been started. The aim of AEOLUS is to develop the technological level in the field of advanced launchers so that The Nether1ands will be able to participate in advanced-launcher projects. Within this project, studies at the highest level of the launcher, or space plane, are conducted by Faculty of Aerospace Engineering, Delft University of Technology. This space-plane analysis has been performed within the work package 212. In this report, AEOLUS document code AE­DUT-TN-9403 (1), a sensitivity analysis has been performed to get insight in the relation between the important trajectory parameters and the performance of a space plane (like the payload mass and the fueVpropellant mass). For the required trajectory calculations, the trajectory simulation tool ASCENT has been used. With ASCENT trajectories can be composed by hand. The sensitivity analysis has been performed with the Taguchi method. This method is an efficient approach tor determining near optimum design parameters. To perform the sensitivity analysis, firstly, a Two Stage To Orbit space plane data set has been composed with the help of data of the Winged Cone Configuration and data of the HORUS 2B. For this space plane a Sänger-like trajectory is generated with the help of the simulation program ASCENT. Next, thirteen trajectory parameters have been selected lor the sensitivity analysis. In 36 different simulations the trajectory parameters are varied ± 10% around !heir reference value. The configuration and mass values of the first stage and second stage are kept the same for all 36 simulations. The payload mass has been corrected in relation to the required amount of propellant mass tor the second stage. For the conditions investigated in this report il has been found !hal the resulting variation in delivered payload mass was about ± 3,5 ton around the mean value of 1.5 ton of the simulations. The propellant mass varied about ± 23 ton around the mean value of 161 ton. The relations of these performance variables with the most important trajectory parameters have been expressed in two polynomials. Mainly the separation conditions and the trajectory of the second stage influence the delivered payload mass. The best separation conditions are tor the highest possible values tor the separation altitude and Mach number. The influence of the flight-path angle at separation appeared to be small. To decrease the fuel mass consumed during the first stage, the dynamic pressure and the flight-path angle should be as large as possible. The first part of the trajectory after take-off can have much influence on the required fuel mass. The sensitivity analysis results also clear1y showed that trajectory optimization is a necessary tool tor space plane analysis. Furthermore, because of the large variations in propellant mass, it will be necessary to have a space plane design tool to anticipate on these changes by corrections in the space plane configuration.