Many ESA missions, past, present and future rely on parachutes for their operation. Examples include the Huygens mission to Titan, the ExoMars missions to Mars and the Space Rider space plane. Although ESA employs many engineers who are experts in their fields, the use of parachutes for space missions is not sufficiently common to justify the existence of a permanent team of parachute engineers with in-house developed software tools.
After several high-profile ESA missions, including Huygens, and ARD, it became clear that an independently validated aerodynamic design tool to enable analyses of parachutes was highly desirable.
Vorticity worked in partnership with SCISYS throughout the project, developing an integrated software tool to aid engineers in a number of different tasks, including sizing, estimation of parachute inflation force, material selection, deployment system modelling and trajectory modelling. These tools are supported by six databases that contain data required by the tools.
Parachute Engineering Tool
All the modules are integrated within a Graphical User Interface which allows them to be run individually and to pass data between them for different phases of the analysis. Available models are listed below.
The models are validated against mission data, including Huygens and ExoMars, and Technology Research Programmes, for example, Supersonic Parachute Research and SuperMax.
Parachute Type Recommendation
This module recommends a parachute type (e.g. Disk-Gap-Band or Ring slot) for a given mission based on the requirements for the system and the environment in which it operates.
The Parachute Sizing module calculates the size of parachute required for a mission based on system parameters such as the required terminal rate of descent. The tool makes use of an extensive database of parachute types built into the software to obtain the characteristics of the chosen parachute type.
The highest load experienced by a parachute is usually the inflation force. In order to design an optimal, low mass system it is necessary to calculate this force which varies with deployment conditions, payload design and the environment. The inflation tool enables calculation of parachute inflation in terrestrial tests and allows extrapolation to planetary conditions. It is validated against over 30 years of test data gathered by Vorticity and others.
Once the parachute type, size and inflation load have been determined, the detailed design and materials may be selected. For any parachute design, there are always several options using different materials and detailed geometry (e.g. the number of lines). This tool recommends a detailed design and materials based on the operating conditions and chosen margin policy. It then allows the user to fine-tune the design. The mass of the final parachute is then calculated taking into account factors such as seam allowances.
Deployment is the most challenging phase of a parachutes life cycle. It must be deployed in a controlled progressive manner, ensuring full deployment without risking excessive deployment speeds. Parachutes can be deployed by mortars, tractor rockets or pilot chutes. The deployment model allows all these methods to be modelled and optimised to obtain the best solution for any mission.
A trajectory tool is included to allow the performance of the parachute system to be assessed against mission requirements for total distance covered, flight time and verticalisation of the system.
A stability tool is included to model the motion of the parachute/payload system with 6 degrees of freedom for each (position and orientation). This allows the response of the system to external influences such as wind gusts to be identified.
Ancillary Mass Estimation
A parachute system will always include many components in addition to the parachute itself; for example, deployment systems, release devices and containers and bags to pack the parachute(s). In order to optimise the whole system, these components must be taken into account. This tool allows the estimation of the mass of all these components.