Dawn Aerospace Mk-III Spaceplane Aerothermodynamic Analysis

Abstract

Dawn Aerospace is developing a horizontal take-off and landing two stage to orbit partially-reusable launcher concept. The re-usable first stage spaceplane operates on a return to launch site trajectory and integrates into the existing airspace, flying as an UAV. For any re-entry vehicle the design needs to account for aerothermodynamic behaviour around the vehicle, to ensure the structure can survive the re-entry temperatures. The unique mission of the Mk-III means the thermal design considerations are unique and provide a new engineering challenge and research topic.

This thesis investigates the aerothermodynamic behaviour of the Mk-III flow and structure. A loosely coupled model was created for this purpose, which couples engineering methods to predict the aerothermodynamics and the thermal behaviour of the structure. The coupling is done by transferring the external skin temperature and convective heat flux between the two simulations.

The primary research question for this thesis is “What thermal protection systems have potential to be implemented on the Dawn Aerospace Mk-III spaceplane for a range of different design trajectories.” Two thermal protection systems (TPS) and material choices have been identified as potential solutions. The first is a fully titanium structure, which can handle the temperature experienced by the Mk-III for all trajectories at every point along the vehicle. The second is a combined titanium and BMI CF structure with an insulation layer on the BMI CF. The titanium is required for the temperatures experienced on the vehicle’s leading edges, while the BMI CF has been identified as suitable in areas away from the leading edge if protected by an insulation TPS. A benefit this option produces is that the insulation layer can be changed in thickness to lighten the vehicle for lower design trajectories, therefore creating different vehicles for different trajectories. However, combining a metal with a composite could pose manufacturing issues such as cost for different manufacturing processes and joining problems. This thesis could not properly trade-off between these two options due to it being outside the scope of this thesis and due to limitations in detailed structural knowledge.

These two material choices were chosen from four materials analysed in the thesis and four different TPS. Other TPS were not suitable at decreasing the structural temperature for the Mk-III mission or had an unjustifiable weight penalty. The other material choices would have been suitable in certain situations but were heavier than the current proposed options and might have required a TPS.

This thesis provides valuable insight in what suitable material and TPS choices could be for the Mk-III mission. It also shows that for any future material and TPS choice to be made, a comprehensive structural analysis is required. Mass is a key trade-off parameter between the two proposed solutions and a better structural analysis is required for any further trade-off.