The Team for Advanced Flow Simulation and Modeling (T*AFSM) at Rice University has been using the Stabilized Space-Time Fluid-Structure Interaction (SSTFSI) they developed to model parachute aerodynamics. The complexity of ringsail parachutes requires additional techniques for successful modeling of the reefed stages. Methods developed for this purpose include sequential shape determination, which is an iterative method for determining a shape and corresponding flow field, and coupled FSI using a circumferentially symmetrized traction applied to the parachute. In addition to modeling the reefed stages, these methods provide a suitable starting point for full FSI computations. A multiscale sequentially-coupled FSI computation, together with cable symmetrization, can be used to obtain a refined structural mechanics solution where needed. Furthermore, pressure distribution generation can be used to match structural shapes to drop test observations.
The Team for Advanced Flow Simulation and Modeling (T☆FSM) at Rice University specializes in developing fluid-structure interaction (FSI) modeling techniques for several classes of challenging problems including geometrically complex parachutes. Current modeling technologies are expanded upon with emphasis placed on more realistic FSI modeling of the Orion spacecraft ringsail parachutes. A method for generating a starting condition that matches NASA drop test data and allows for a fair comparison of design variations is introduced. The effect of the geometric porosity distribution on parachute performance and stability is analyzed for three parachute configurations. Rotationally periodic computations that model flow past the complex canopy geometry are presented. Fabric and geometric porosity coefficients are calculated for an improved FSI porosity model. A spatially multiscale technique is used to compare fabric stresses with and without a vent hoop.
The Team for Advanced Flow Simulation and Modeling (T*AFSM) at Rice University has been developing fluid-structure interaction (FSI) modeling techniques using Stabilized Space-Time FSI (SSTFSI) core technology to model spacecraft parachutes and carry out informative dynamical analysis of parachute performance. Computer modeling of spacecraft parachutes, which are quite often used in clusters of two or three large parachutes, involves FSI between the parachute canopy and the air, geometric complexities created by the construction of the ringsail parachute with hundreds of gaps and slits, and the contact between the parachutes. The computational challenges related to the FSI have successfully been addressed, and one of the special techniques used to deal with the geometric complexities is the Homogenized Modeling of Geometric Porosity. The technique for modeling, in the context of an FSI problem, the contact between two structural surfaces is described and the results of FSI computations using this technique are presented. The results obtained from FSI computations of single parachutes and parachute clusters, the related dynamical analysis, and a special decomposition technique for parachute descent speed are presented. A special technique for extracting model parameters from a parachute FSI computation is also presented.
To increase aerodynamic performance, the geometric porosity of a ringsail spacecraft parachute canopy is sometimes increased, beyond the "rings" and "sails" with hundreds of "ring gaps" and "sail slits." This creates extra computational challenges for fluid--structure interaction (FSI) modeling of clusters of such parachutes, beyond those created by the lightness of the canopy structure, geometric complexities of hundreds of gaps and slits, and the contact between the parachutes of the cluster. In FSI computation of parachutes with such "modified geometric porosity," the flow through the "windows" created by the removal of the panels and the wider gaps created by the removal of the sails cannot be accurately modeled with the Homogenized Modeling of Geometric Porosity (HMGP), which was introduced to deal with the hundreds of gaps and slits. The flow needs to be actually resolved. All these computational challenges need to be addressed simultaneously in FSI modeling of clusters of spacecraft parachutes with modified geometric porosity. The core numerical technology is the Stabilized Space--Time FSI (SSTFSI) technique, and the contact between the parachutes is handled with the Surface-Edge-Node Contact Tracking (SENCT) technique. In the computations reported here...
At higher altitudes, prior to the deployment of the main parachutes, the Orion spacecraft descent to Earth will rely on deceleration by drogue parachutes. These parachutes have a ribbon construction, and in fluid–structure interaction (FSI) modeling this creates geometric and flow complexities comparable to those encountered in FSI modeling of the main parachutes, which have a ringsail construction. The drogue parachutes to be used with the Orion spacecraft have 24 gores, with 52 ribbons in each gore, resulting in hundreds of gaps that the flow goes through. We address this computational challenge, as was done for the main parachutes, with the Homogenized Modeling of Geometric Porosity (HMGP). Like the main parachutes, the drogue parachutes will be used in multiple stages, starting with a "reefed" stage where a cable along the parachute skirt constrains the diameter to be less than the diameter in the subsequent stage. After a certain period of time during the descent, the cable is cut and the parachute "disreefs" (i.e. expands) to the next stage. Computing the parachute shape at the reefed stage and FSI modeling during the disreefing involve computational challenges beyond those in FSI modeling of fully-open drogue parachutes. Orion spacecraft drogue parachutes will have three stages...
Fluid--structure interaction (FSI) modeling of spacecraft parachutes involves a number of computational challenges. The canopy complexity created by the hundreds of gaps and slits and design-related modification of that geometric porosity by removal of some of the sails and panels are among the formidable challenges. Disreefing from one stage to another when the parachute is used in multiple stages is another formidable challenge. This thesis addresses the computational challenges involved in disreefing of spacecraft parachutes and fully-open and reefed stages of the parachutes with modified geometric porosity. The special techniques developed to address these challenges are described and the FSI computations are be reported. The thesis also addresses the modeling and computation challenges involved in very early stages, where the sudden separation of a cover jettisoned to the spacecraft wake needs to be modeled. Higher-order temporal representations used in modeling the separation motion are described, and the computed separation and wake-induced forces acting on the cover are reported.
The Team for Advanced Flow Simulation and Modeling (T☆AFSM) at Rice University has been developing the Stabilized Space--Time Fluid--Structure Interaction core technologies in conjunction with an array of special techniques to overcome the complexities present in modeling ringsail parachutes. Flight characteristics of single and clustered ringsail parachutes are explained. Ringsail modeling techniques are employed to examine and discern the parachute's aerodynamic characteristics. Several design modifications, including suspension line length ratio, over-inflation control line and canopy loading are investigated. The application of the ringsail modeling techniques to two and three parachutes in a cluster is demonstrated.