Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

Improved parachute dynamic flare analysis Tool

A main issue for a successful large-scale ram-air gliding parachute system is the quality of the dynamic flare manoeuvre. By an accurately timed pulling of full brakes horizontal velocity and in particular the vertical speed shall tend to zero just at the moment of payload touch down. Of course, this cannot be reached completely in any circumstance, but a limitation of the sink rate at landing to values less than 3 m/s seems to be achievable.

The numerical simulation of the behaviour of the parafoil/payload system in this situation requires the solution of the set of equations of motion. The problem can be treated at various levels of physical modelling which adresses the number of bodies, the rigidity and the number of degrees of freedom (n-DoF) of the considered system.

At EADS-ST LP46 a two-dimensional (4DoF) and a three-dimensional (8DoF) model describing the parafoil/ payload system are available. As the landing flare manoeuvre shall take place without any lateral motion, i.e. no curved flight during landing, the simulation of this particular phase currently focuses on the 2-D model describing the longitudinal motion allowing two transactional degrees of freedom of the entire system and canopy pitching motion as well as relative payload pitching motion.

Once the flight mechanical model is selected, flare initiation altitude, flare speed, and the aerodynamic model are the major parameters to be varied. Numerous simulations were performed and documented showing the influence of the above parameters. As expected the aerodynamic behaviour of the canopy in terms of lift and drag change due to brake deflection clearly determines the flare performance.

For the actual FASTWing canopy design only theoretical predictions are available to assess the aerodynamic performance of the canopy and the corresponding brake efficiency. During the wind tunnel test aerodynamic characteristics of the basic design and control deflection efficiency of the FASTWing canopy will be examined in detail. Feeding these coefficients into the 'dynamic flare analysis tool' will enable to further optimise the landing flare manoeuvre with regard to initiation altitude and line travel speed during braking.

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EADS Space Transportation
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