Supersonic delta qualification by analysis program for the mars science laboratory parachute decelerator system

The Mars Science Laboratory Mission (MSL) plans to deploy NASA's largest, highest Mach number, and highest payload extra-terrestrial aerodynamic decelerator to the surface of Mars in 2010. The 21.5-m Viking-scaled Disk-Gap-Band (DGB) parachute will deploy at up to Mach 2.2 and 750 Pa, the upper deployment condition range demonstrated by the Viking Balloon Launched Decelerator Test (BLDT) program. All previous Mars parachute systems have derived their supersonic qualification from Viking heritage. MSL differs from the previous Mars programs in that it is 33% larger than the Viking parachute and will spend up to seven seconds above Mach 1.5, a flight regime known to induce the canopy area oscillations, characterized by variations in drag and collapses in the band region of the parachute. To reduce risk to the mission, MSL has embarked on a multi-phase delta qualification by analysis and subscale supersonic wind tunnel test program to address the fundamental physics of the supersonic operation of DGB parachutes. The program explores the cause of the area oscillation phenomena and the performance of the parachute system as a function of Mach number, Re number, parachute to capsule size and proximity. With a physical understanding of the parachute flow field and parachute response to it, the existing Viking BLDT heritage qualification data can be leveraged to the larger scale of MSL, enabling a heritage-based supersonic qualification. To achieve this, MSL will determine by fluid dynamics simulation validated by subscale supersonic wind tunnel tests, that the supersonic flight characteristics of the Viking scale/material DGB and MSL scale/material DGB are aerodynamically similar. The first phase is computational fluid dynamics of a 2% scale rigid parachute canopy and capsule validated by a 2% scale wind tunnel test of the rigid configuration in the NASA AMES 9×7 ft unitary tunnel. Results from this program indicate excellent qualitative and quantitative validation of the capsule wake velocity predictions and fundamental physics of the aerodynamic drivers of the supersonic instability. Phase two is fluid structure interaction analysis of a flexible canopy with capsule validated by 4% scale wind tunnel tests in the GRC 10×10 ft unitary tunnel. The final phase is the application of the validated FSI tools to the prediction of the full scale parachute performance in Mars type deployment conditions, providing predictions of supersonic drag performance, stability and canopy loading. The methodology and results of the analysis and test program as well as validation results to date will be presented.