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Space Systems Design Laboratory (SSDL)
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ItemMass Model Development for Conceptual Design of a Hypersonic Rigid Deployable Decelerator(Georgia Institute of Technology, 2012-06) Cruz-Ayoroa, Juan G. ; Kazemba, Cole D. ; Steinfeldt, Bradley A. ; Kelly, Jenny R. ; Clark, Ian G. ; Braun, Robert D.As the required payload masses for planetary entry systems increase, innovative entry vehicle decelerator systems are becoming a topic of interest. With this interest comes a growing need for the capability to characterize the performance of such decelerators. This work proposes a first-order mass model for fully-rigid deployable decelerator systems. The analytical methodology that is presented can be applied to a wide range of entry conditions and material properties for rapid design space exploration. The tool is applied to a case study of a C/SiC hot structure decelerator at Mars for comparison to the performance of the Hypersonic Inflatable Aerodynamic Decelerator concepts presented in a recent EDL-SA study. Results show that the performance of a rigid deployable structure can be comparable to that of a Hypersonic Inflatable Aerodynamic Decelerator at high entry ballistic coefficients and small decelerator diameters.
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ItemPerformance Characterization, Sensitivity and Comparison of a Dual Layer Thermal Protection System(Georgia Institute of Technology, 2011-06) Kazemba, Cole D. ; McGuire, Mary Kathleen ; Howard, Austin ; Clark, Ian G. ; Braun, Robert D.With the goal of landing high-mass cargo or crewed missions on Mars, NASA has been developing new thermal protection technologies with enhanced capability and reduced mass compared to traditional approaches. Two examples of new thermal protection system (TPS) concepts are dual layer and flexible TPS. Each of these systems introduces unique challenges along with potential performance enhancements. Traditional monolithic ablative TPS, which have been flown on every Mars robotic mission to date, use a single layer of ablative material. The new dual layer TPS concepts utilize an insulating layer of material beneath an ablative layer to increase efficiency and save mass. A study was conducted on the dual layer system to identify sensitivities in performance to uncertainties in material properties and aerothermal environments. A performance metric which is independent of the system construction was developed in order to directly compare the abilities and benefits between the traditional, dual layer and eventually, flexible systems. Using a custom MATLAB code enveloping the Fully Implicit Ablation and Thermal Response Program (FIAT), the required TPS areal mass was calculated for several different parametric scenarios. Overall TPS areal mass was found to be most sensitive to the constraining allowable temperature in each system and aerothermal heat transfer augmentation (attributed here to material surface roughness). From these preliminary results it was found that the nominal dual layer TPS construction investigated could produce improvements over a traditional TPS in the specified performance metric between 14-36%, depending on the flight environments and total integrated heat load expected.
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ItemStatistical Entry, Descent and Landing Performance Reconstruction of the Mars Phoenix Lander(Georgia Institute of Technology, 2011-06) Dutta, Soumyo ; Clark, Ian G. ; Russell, Ryan P. ; Braun, Robert D.The Phoenix Lander successfully landed on the surface of Mars on May 25, 2008. During the entry, descent and landing (EDL), the vehicle had instruments on-board that took sensed acceleration, angular rates and altimeter measurements. In this study, methodology used to reconstruct the trajectory and other EDL performance information using a statistical filter to process the observations from the sensors is demonstrated. A statistical filter estimates parameters simultaneously with the uncertainty in the estimates. The results presented here will include Phoenix’s event timeline, trajectory information, time-of-flight atmosphere and aerodynamic coefficients of an EDL subsystem as well as the uncertainty in the estimated states.
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ItemSubsonic and Transonic Wind Tunnel Testing of Two Inflatable Aerodynamic Decelerators(Georgia Institute of Technology, 2010-06) Tanner, Christopher L. ; Cruz, Juan R. ; Hughes, Monica F. ; Clark, Ian G. ; Braun, Robert D.Two inflatable aerodynamic decelerator designs were tested in the Transonic Dynamics Tunnel at the NASA Langley Research Center: a tension cone and an isotensoid. The tension cone consists of a flexible tension shell attached to a torus and the isotensoid employs a ram-air inflated envelope. Tests were conducted at Mach numbers from 0.3 to 1.08 and Reynolds numbers from 0.59 to 2.46 million. The main objective of these tests was to obtain static aerodynamic coefficients at subsonic and transonic speeds to supplement supersonic aerodynamic data for these same two designs. The axial force coefficients of both designs increased smoothly from subsonic through transonic Mach numbers. Dynamic data show significant oscillation of the tension cone and minimal oscillation of the isotensoid. The transonic and subsonic data will be used to assemble an inflatable decelerator aerodynamic database for use in computational analyses and system studies.