The secure touchdown of the probe is likely one of the most tough challenges in Mars exploration, and the Mars supersonic parachute is extraordinarily necessary for this course of. To this point, all of the profitable Mars exploration missions have used disk-gap-band (DGB) parachutes. Nevertheless, the DGB parachute with the very best diameter of 21.35 m can’t be additional used for future Mars exploration missions with greater masses.
Subsequent-generation supersonic parachutes carried out by NASA, comparable to disksail parachutes, are options to DGB parachutes. Disksail parachutes have bigger porous gaps and smaller porous seams on the cover floor than DGB parachutes. Nevertheless, there are few research on the aerodynamic traits of supersonic parachutes with completely different geometric porosity constructions and places.
Therefore, the affect mechanism of porous seams or gaps and their places on the efficiency of supersonic parachute techniques in Martian atmospheric circumstances stays unclear.
In a analysis paper just lately printed in House: Science & Know-how, eight students from 5 organizations, together with Central South College, Xi’An Jiaotong College, Nanjing College of Aeronautics and Astronautics, Beijing Institute of House Mechanics & Electrical energy, and The Hong Kong Polytechnic College, collectively examine the aerodynamic traits of the brand new supersonic parachute with completely different porosities and seam/hole positions and perceive the affect mechanism of the porosity and the positions of porous constructions on the aerodynamic performances of supersonic parachutes.
First, the authors introduce the parachute mannequin within the research. The unique parachute system mannequin used on this research contains the capsule and cover. The cover mannequin is designed from the SSDS mannequin in NASA’s Low-Density Supersonic Decelerator (LDSD) flight assessments, and the capsule mannequin is in step with the Mars Science Laboratory (MSL) probe mannequin.
The construction of the cover mannequin is split into 4 components alongside the X-axis path from the mouth to the highest of the cover physique: the cover band, the ring 19–ring 16, the ring 15–ring 10, and the cover disk with a vent.
The cover mannequin has 2 varieties of porosity constructions, i.e., hole and seam. The highest hole, G1, locates between ring 10 and the cover disk, and its geometric porosity is 4%. The center hole, G2, locates between rings 16 and 15, and its geometric porosity is 3%. The seams find between the opposite rings or the ring and cover band. The order variety of the seam is called from the higher ring. The gaps have massive geometric porosity, and the seams have tiny geometric porosity.
On this research, cover fashions with completely different single-seam positions are designed (the highest vent is retained for all of the fashions), wherein just one seam is open for a cover mannequin. In the meantime, the highest hole mannequin, the G1 mannequin, is a mannequin that solely retains the highest hole of G1 and the highest vent, and the center hole mannequin, the G2 mannequin, solely retains the center hole of G2 and the highest vent. Combining the above seams with completely different gaps, new cover fashions with completely different seams and gaps are additionally designed.
Moreover, the cover mannequin is taken into account a inflexible physique on this work.
Then, authors set forth the freestream circumstances and numerical strategies used within the simulation. The freestream circumstances used within the simulation are in step with these of the working altitude of the supersonic parachute within the MSL mission and the working speeds of the parachute within the steady descent stage.
As for numerical strategies, the unsteady flows over the supersonic parachute system (i.e., completely different cover fashions with the identical MSL capsule) are studied by numerically fixing the third-dimensional compressible N-S equations. The finite quantity technique is adopted for spatial discretization, and the HLLC (Harten-Lax-van Leer-Contact) scheme is employed to calculate the inviscid flux time period. Moreover, the TVD polynomial interpolation scheme is used to keep away from numerical oscillations.
As well as, an implicit 2-time-step propulsion scheme is adopted to seize the complicated unsteady circulate area constructions across the supersonic parachute with the time step of 1.0×10-4 s.
Final, the authors current the outcomes and draw the conclusion. The numerical outcomes are summarized as follows:
(1) The porosity constructions of the cover physique don’t have any important impact on the circulate area mode of the supersonic parachute system, and so they have little impact on the stress distribution of the capsule floor and the circulate area construction across the capsule physique.
(2) For the cover fashions with single seams within the current research, the fashions with decrease seams (decrease facet of cover) have higher drag efficiency, and the S11 and S17 fashions present bigger drag coefficients and higher stability efficiency. For the cover fashions with a single hole, the drag coefficient of the G2 mannequin (0.72) is considerably bigger than that of the G1 mannequin (0.64), whereas the lateral pressure coefficient fluctuation of G1 (0.072) is smaller than that of the G2 mannequin (0.091).
(3) With the addition of various seams, the drag coefficient of G1S fashions is bigger than that of the G1 mannequin with a single G1. In contrast with the unique G1 mannequin, the soundness efficiency of the mixed G1S fashions has no important change. The drag efficiency of the mixed G2S fashions with the seams decreases in contrast with the unique G2 mannequin; how- ever, the soundness efficiency of the mixed G2S fashions is improved in contrast with the unique G2.
Moreover, when the mixture of seam and hole farther aside is designed for a cover, the stress inside the cover principally decreases in contrast with the unique single mannequin, whereas the mixture of seam and hole with a brief distance is designed for a cover and the stress change inside the cover is minor.
The numerical outcomes of this research present that the brand new supersonic parachutes with completely different porosity constructions of seams, gaps, and their mixtures exhibit considerably completely different aerodynamic performances. The subsequent era of parachutes with extra complicated mixtures of seams and gaps must be designed to research their aerodynamic traits and affect mechanisms.
Lulu Jiang et al, Impact of Totally different Geometric Porosities on Aerodynamic Traits of Supersonic Parachutes, House: Science & Know-how (2023). DOI: 10.34133/area.0062
Beijing Institute of Know-how Press Co.