Next generation mechanically deployable aero-decelerators for Mars entry
File(s)
Author(s)
Peacocke, Lisa
Type
Thesis
Abstract
Current Mars entry vehicle technology is near its payload mass delivery limit. Mechanically deployable aero-decelerators are a next generation technology that would enable the future exploration of Mars, including human landing. Various concepts and architectures have been proposed over the years, with widely-varying mass assessments and limited technology development.
A novel 6 degree-of-freedom entry trajectory simulator coupled with a structural model of the deployable elements, or ribs, has been developed and correlated against industry tools and flight data to investigate and optimise the design of mechanically deployable aero-decelerators. A major assumption of the simulator – that heatshield gores remain flat under rib deformation – has been investigated by testing ambient 3D woven carbon fabric for use as the flexible thermal protection system material, proving that conditioning can significantly improve the stiffness properties of the fabric.
The design optimisation has revealed that, although deployable rib flexibility is beneficial in reducing mass and volume of the deployed ribs, an increase in peak heat flux will result. However, if mass savings from flexible ribs can be reallocated towards increasing the diameter of the entry vehicle, significant entry trajectory benefits can be gained. A set of general design principles for mechanically deployable aero-decelerators has been developed based on the optimisation investigations, including the recommendations to include at least 10 ribs to minimise drag reduction, and to increase the initial rib angle if rib flexibility is allowed to improve deceleration.
In addition, the entry vehicle roll rate appears to be influenced by the number of deployable ribs. This roll instability of faceted entry vehicles is of significant concern, so a novel supersonic wind tunnel test methodology was developed to further investigate this hypothesis. The first experimental results imply that pitch and yaw attitude and instabilities are necessary pre-requisites to initiate roll during entry, and that an 8 rib test article rotates at faster rates than the 12 rib test article. Finally, a new functional relationship for the angular acceleration of entry vehicles has been proposed that it is hoped will inspire further investigations in this area.
A novel 6 degree-of-freedom entry trajectory simulator coupled with a structural model of the deployable elements, or ribs, has been developed and correlated against industry tools and flight data to investigate and optimise the design of mechanically deployable aero-decelerators. A major assumption of the simulator – that heatshield gores remain flat under rib deformation – has been investigated by testing ambient 3D woven carbon fabric for use as the flexible thermal protection system material, proving that conditioning can significantly improve the stiffness properties of the fabric.
The design optimisation has revealed that, although deployable rib flexibility is beneficial in reducing mass and volume of the deployed ribs, an increase in peak heat flux will result. However, if mass savings from flexible ribs can be reallocated towards increasing the diameter of the entry vehicle, significant entry trajectory benefits can be gained. A set of general design principles for mechanically deployable aero-decelerators has been developed based on the optimisation investigations, including the recommendations to include at least 10 ribs to minimise drag reduction, and to increase the initial rib angle if rib flexibility is allowed to improve deceleration.
In addition, the entry vehicle roll rate appears to be influenced by the number of deployable ribs. This roll instability of faceted entry vehicles is of significant concern, so a novel supersonic wind tunnel test methodology was developed to further investigate this hypothesis. The first experimental results imply that pitch and yaw attitude and instabilities are necessary pre-requisites to initiate roll during entry, and that an 8 rib test article rotates at faster rates than the 12 rib test article. Finally, a new functional relationship for the angular acceleration of entry vehicles has been proposed that it is hoped will inspire further investigations in this area.
Version
Open Access
Date Issued
2021-09
Date Awarded
2022-03
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Bruce, Paul
Santer, Matthew
Sponsor
Engineering and Physical Sciences Research Council
Airbus Defence and Space (Firm)
Grant Number
1817405
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)