Robust multi-disciplinary modelling of future re-usable aerospace planes

Practical embodiment of the Single-Stage to Orbit concept has long been held as the key to unlocking a future of rapid, reliable, even scheduled access to space. The full potential of Single-Stage to Orbit will only be realised when this vehicle concept is integrated into an airline-like operational paradigm which has, as its basis, the re-usability of the individual vehicles that comprise the fleet, but in addition, extends to the long-term assuredness of operations through sustained reliability, quick turnaround, and control over recurring costs to the point where the profitability of the enterprise can be assured for its owners and investors. The purpose of this paper is to make some initial steps towards providing some quantitative answers as to how decisions that are made regarding the design of the actual hardware might impact on long-term viability of the technology through influencing the reliability of the system and eventually its cost when incorporated as part of an integrated transportation system. This is achieved through embedding a physics-based simulation of the performance of the vehicle subsystems, under operational conditions, into a Discrete Event Simulation of spaceport operations, allowing the statistical relationship between the various design characteristics of the vehicle, and the metrics that are relevant to its operational cost, to be exposed

Robust multi-disciplinary design and optimisation of a reusable launch vehicle

For various technical reasons, no fully reusable launch vehicle has ever been successfully constructed or operated. Nonetheless, a range of reusable hypersonic vehicles is currently being considered as a viable alternative to the expensive but more conventional expendable rocket systems that are currently being used to gain access to space. This paper presents a methodology that has been developed for the rapid and efficient preliminary design of such vehicles. The methodology that is presented uses multi-disciplinary design optimization coupled with an integrated set of reduced-order models to estimate the characteristics of the vehicle's aero-thermodynamic, propulsion, thermal protection and internal system architecture, as well as to estimate its overall mass. In the present work, the methodology has been applied to the multi-disciplinary modelling and optimization of a reusable hybrid rocket- and ramjet-powered launch vehicle during both the ascent and re-entry phases of its mission

Influence of boundary layer transition on the trajectory optimisation of a reusable launch vehicle

Based on flight experience from the Space Shuttle programme, it is well known that mis-prediction of the effects of boundary layer transition represents one of the highest technical risks when designing a Reusable Launch Vehicle. Indeed, mis-prediction of the boundary layer behaviour at hypersonic speeds could impinge on the overall survivability of a given design, whereas excessive conservatism in the analyses could result in an overweight vehicle not capable of attaining orbit with a useful payload mass on-board. From the standpoint of conceptual design, it is therefore of paramount importance to develop engineering means of predicting the effects of uncertainty in the behaviour of the boundary layer on the vehicle as far as transition is concerned. Indeed, a robust preliminary analysis should ensure thermal survival of the spaceplane structure and give a measure of confidence in the ability of the conceptual vehicle to maintain sufficiently good controllability during re-entry in the presence of possibly asymmetric boundary layer transition. A reduced-order model has been used to evaluate the sensitivity of a particular design of hypersonic reusable launch vehicle to the uncertainty in predicting its aero-thermodynamic behavior that results from variability in the onset of boundary layer transition on its surface, especially when optimising the re-entry trajectory of the vehicle. The results of the simulations presented here seem to suggest that the effects of boundary layer transition on the vehicle's performance during re-entry might largely be ameliorated through careful aerodynamic design and appropriate scheduling of the control surface deflections along the vehicle's trajectory

Development of a rapid inviscid-boundary layer aerodynamics tool

Hypersonic vehicles, combined with scramjet propulsion, offer significant and unique flexibility, performance and reusability benefits over rockets. These characteristics will likely reduce the cost of access-to-space. However, the realisation of such vehicles is significantly complicated by engine performance requirements which dictate relatively low altitude, high dynamic pressure trajectories. The thick atmosphere and high velocities result in high aerodynamic drag and heating. This paper introduces a simple, aerothermodynamic model for the analysis of hypersonic vehicles using Cart3D to calculate the inviscid flow-field and provide edge conditions to boundary layer calculations. Comparisons are made between two viscous methods of varying fidelity; flat plate correlations for skin friction with a simplified running length calculation and integral methods applied along inviscid, surface streamlines. Three validation cases are presented; (1) a hypersonic, blunt body; (2) a delta-wing, lifting body at subsonic to hypersonic Mach numbers and (3) a hypersonic, realistic vehicle configuration with internal flow-paths. In general, Cart3D predicts the lift and pitching moment coefficients well but consistently under-predicts drag given the absence of shear stress. The viscous contribution to aerodynamic forces was found to be adequately modelled using flat plate correlations and a simple Euclidean distance in place of the true running length. Preliminary results, however, suggest predictions of surface heat transfer rates benefit from a streamline running length and higher fidelity boundary layer methods