Series
Master's Projects

Permanent Link
https://hdl.handle.net/1853/71003
Series Type
Publication Series
Description
Associated Organization(s)
Associated Organization(s)

Filters
2012 - 2013 9
9
9
9
Reset filters

Settings
search.filters.applied.f.advisor: Braun, Robert D. × End date: 2013 × Start date: 2011 × search.filters.applied.f.resourcesubtype: Masters Project ×

Publication Search Results

Now showing 1 - 9 of 9
Thumbnail Image
Item

Investigation of Drag Modulated Supersonic Inflatable Aerodynamic Decelerators for Use on Sounding Rocket Payloads

2013-12-13 , Miller, Matthew J.

This paper presents an assessment of use of a supersonic inflatable aerodynamic decelerator for drag modulation of a sounding rocket payload bus structure as part of a high-altitude sample return mission. The scientific goal of this mission is to capture mesospheric dust and particulate matter located 45 km to 85 km in altitude. This mission is also to demonstrate technology that is capable of precise landings by combining a decelerator system comprised of inflatable aerodynamic decelerator to reach within 10 km with a guided parafoil system. Three decelerator configurations, the tension cone, attached isotensoid, and the trailing isotensoid, were examined on the metrics of decelerator mass, aerodynamic performance, and vehicle integration. The attached isotensoid was found to be the most mass efficient option, while the trailing isotensoid was determined to be preferable from an overall system level perspective. The decelerators’ precision landing capability through the use of drag modulation was also evaluated. Downrange error was reduced by 21% by drag modulation as compared to an 8.5 m supersonic disk-gap-band parachute. When coupled with a guided parafoil, drag modulation provides a 95% confidence level in landing within the 10 km parafoil capability region, and a 76% confidence level of landing within 5 km of the target.

View
Thumbnail Image
Item

Aerodynamic Stability and Performance of Next-Generation Parachutes for Mars Descent

2013-07-18 , Gonyea, Keir

The aerodynamic stability and performance characteristics of next-generation supersonic parachutes were determined through wind tunnel testing. Canopy configurations included the disk-gap-band (DGB), ringsail, and ringsail-variant designs referred to as the disksail and starsail. Stereo photogrammetric processing was performed during testing, which was then used to estimate the static and dynamic moment coefficient curves as a function of total angle of attack. The dynamic components of the angle of attack and sideslip angle were shown to be significant, heavily influencing the resulting total angle of attack profile and moment coefficients. Uncertainty in the apparent mass of the canopies resulted in uncertainty in the moment coefficient magnitudes. From the stability curves, the peak moment, trim total angle of attack, and pitch stiffness at the trim angle could be determined. Parachute stability was assessed in the context of drag load and geometric porosity. An inverse relationship between the drag load and the stability of the canopies was generally seen. The DGB canopies tended to be more stable while the ringsail and disksail canopies had more drag. Similar stability properties as the DGB with slightly higher drag loads were obtained by increasing the geometric porosity distribution around the crown of the disksail canopies.

View
Thumbnail Image
Item

Implementation of a Mesomechanical Material Model for IAD Fabrics within LS-DYNA

2012-12-14 , Hill, Jeremy

The implementation and evaluation of a high fidelity material model for dry fabrics is the main objective of this paper. Inflatable Aerodynamic Decelerators (IADs) and other air inflated structures quite often utilize woven fabrics due to their lightweight and high loading carrying capabilities. Design optimization of these inflated structures relies on a detailed understanding of the woven fabric mechanics. Woven fabrics are composite orthotropic materials that respond differently under load from traditional solid mechanics. While low fidelity fabric materials usually assume a continuous medium, a higher fidelity model needs to account for the reorientation of yarns and weave geometry. An existing mesomechanical material model within the LS-DYNAÒ commercial non-linear finite element software package is utilized. In this paper, experimental stress-strain data for Kevlar 129 samples are validated against numerical simulations of models with matching geometry and loading conditions.

View
Thumbnail Image
Item

Supersonic Propulsive Divert Maneuvers for Future Robotic and Human Mars Missions

2013-12-13 , Mandalia, Amit B.

Future robotic and human missions to Mars require improved landed precision and increased payload mass. Two architectures that seek to meet these requirements using supersonic propulsive diverts are proposed in this paper: one utilizing a high-altitude propulsive divert and another with thrust vectoring during supersonic retropropulsion. Low ballistic coefficient entry vehicles decelerate high in the thin Mars atmosphere and may be used to deliver higher-mass payloads to the surface. A high-altitude supersonic propulsive divert maneuver is proposed as a means of precision landing for low ballistic coefficient entry vehicles that decelerate to supersonic speeds at altitudes of 20-60 km. This divert maneuver compares favorably to traditional precision landing architectures with up to 100% improvement in range capability while saving over 30% in propellant mass. Architectures which utilize hypersonic vehicles with ballistic coefficients of 10 kg/m2 were found to land within 500 m of a target with this maneuver alone. This high-altitude divert range capability is sensitive to altitude and flight-path angle variations at maneuver initiation and relatively insensitive to velocity at initiation. Propellant mass fraction is relatively invariant to the initial conditions and correlates directly with the divert distance. Supersonic retropropulsion has also been proposed as a means to deliver higher-mass payloads to the surface, and thrust vectoring during supersonic retropropulsion can save a substantial amount of fuel in a precision landing scenario. Propellant mass savings greater than 30% are possible if thrust vectoring is unconstrained during the supersonic phase of flight. Propellant mass fraction is found to be sensitive to the divert direction and also the altitude and flight-path angle, favoring low altitudes and shallow flight-path angles.

View
Thumbnail Image
Item

Photogrammetry Analysis of a Hypersonic Inflatable Aerodynamic Decelerator Structural Test Article

2013-07-11 , Li, Lin

Analysis was performed on photogrammetry data of a 6m Hypersonic Inflatable Aerodynamic Decelerator (HIAD), an inflatable stacked torus used to aid in atmospheric entry, to understand its structural dynamics. Photogrammetry data was obtained during wind tunnel testing under various loading conditions. Test parameters included the freestream dynamic pressure, yaw angle and internal inflation pressure. In addition, two HIAD configurations were analyzed, the basic stacked torus (Baseline configuration) and a second configuration adding a torus near the shoulder to aid in rigidity (Tri-Tori configuration). The analysis includes estimating the deflection of the HIAD under loading as well as calculating the standard deviation relative to the mean deflection and the frequency content of the dynamic response. Under load, the deflection angle for each configuration ranged from 1° to 3° (1σ). Analysis of the results indicates that the Tri-Tori configuration did not demonstrate significant benefit over the Baseline. The photogrammetry data showed that the oscillatory motion increased with higher dynamic pressure but was insensitive to yaw angle. In addition, the analysis showed that the standard deviation of the HIAD shape with respect to the average deflection increased while moving radially outwards. However, the standard deviation values calculated from different camera pairs were inconsistent and did not produce the same standard deviations especially at the interface region. The frequency analysis showed that each radial member behaved similarly to a rigid oscillator, having the same frequency content of motion along each radial direction and increased amplitude when moving radially outward. Both the frequency and shape standard deviation analyses showed that the motion of the HIAD was piecewise continuous in the azimuthal direction. These discontinuities likely arose when stitching together the images from different camera pairs. The photogrammetry data is a valuable dataset providing insight into the static and dynamic response of the HIAD under loading. However, inconsistencies in the camera imaging and stitching need to be resolved and higher temporal resolution will improve the fidelity of analysis

View
Thumbnail Image
Item

Dynamic Stability Analysis of Blunt Body Entry Vehicles Through the Use of a Time-Lagged Aftbody Pitching Moment

2012-10-05 , Kazemba, Cole

This analysis defines an analytic model for the pitching motion of blunt bodies during atmospheric entry. The proposed model is independent of the pitch damping sum term which is present in the standard equations of motion, instead using the principle of a time-lagged aftbody moment as the forcing function for oscillation divergence. Four parameters, all with intuitive physical relevance, are introduced to fully define the aftbody moment and the associated time delay. It is shown that the dynamic oscillation responses typical to blunt bodies can be produced using hysteresis of the aftbody moment alone. The approach used in this investigation is shown to be useful in understanding the governing physical mechanisms for blunt body dynamic stability and in guiding vehicle and mission design requirements. A case study using simulated ballistic range test data is conducted. From this, parameter identification is carried out through the use of a least squares optimizing routine. Results show good agreement with the limited existing literature for the parameters identified. The model parameters were found to be accurate for a wide array of initial conditions and can be identified with a reasonable number of ballistic range shots and computational effort.

View
Thumbnail Image
Item

Flexible Thermal Protection System Physics-Based Modeling for Temperature Profile Predictions

2013-12-03 , Rossman, Grant A.

Candidate material testing was performed on various Flexible Thermal Protection Systems (FTPS) layup configurations in an arc-jet ground test facility. A physics-based thermal model was created to predict the thermal-material response of each FTPS layup under arc-jet induced thermal loading. Initial thermal model temperature predictions of embedded thermocouples for FTPS test articles showed an unsatisfactory correlation to arc jet test data. The Levenberg-Marquardt (LM) inverse parameter estimation technique was implemented to reduce discrepancies between thermal model temperature predictions and experimental thermocouple temperature measurements by iteratively modifying FTPS thermal parameters within the model, such as thermal conductivity and specific heat. A formal parameter estimation methodology, previously applied for ablative TPS, is applied to this FTPS problem to improve understanding estimation behavior and LM error minimization. Nominal, uncertainty, sensitivity, and inverse analysis are performed on scaled thermal inputs to provide insight on solution uniqueness and stability. This error minimization technique is demonstrated on a previously flown FTPS layup configuration consisting of two outer fabric layers, two insulation layers, and one gas barrier layer. Results show that the LM method is a viable technique for inverse parameter estimation of FTPS thermal modeling problems.

View
Thumbnail Image
Item

Evaluation of Deployable Aerosurface Systems for Mars Entry

2012-12-14 , Cruz-Ayoroa, Juan G.

One of the challenges presented by the exploration of Mars is the entry, descent and landing (EDL) of payloads to the surface. Current robotic missions to Mars are reaching the limist of existing Viking heritage EDL technologies. A number of EDL technology improvements can be made to extend the capabilities beyond the current landed mass limits, including increasing the entry vehicle hypersonic drag and lift capability. Technologies being currently studied include inflatable aerodynamic decelerators, which are designed to increase vehicle drag. Many of these concepts center on axisymmetric designs, which provide high drag but relatively low lift and are most easily integrated to blunt entry vehicles. However, due to packaging density and launch vehicle fairing constraints, it is likely that future missions will require the use of slender bodies. This study investigates three deployable concepts designed to provide better integration into a slender vehicle while augmenting its performance by increasing its hypersonic drag. The deployable aerosurfaces are applied to a 5 meter diameter slender vehicle for a robotic mission at Mars with entry masses ranging from 10 to 60t. A multidisciplinary design optimization framework is used to estimate the landed mass capability of each system. Results show that the deployable concepts can significantly improve payload mass capability by reducing the terminal propulsion propellant required. Initial feasibility studies show that the concepts are hypersonically statically stable and comply with mechanical and thermal material capabilities

View
Thumbnail Image
Item

Guided Entry Performance of Low Ballistic Coefficient Vehicles at Mars

2012-05-21 , Meginnis, Ian M.

Current Mars entry, descent, and landing technology is near its performance limit and is generally unable to land payloads on the surface that exceed approximately 1 metric ton. One option for increasing landed payload mass capability is decreasing the entry vehicle’s hypersonic ballistic coefficient. A lower ballistic coefficient vehicle decelerates higher in the atmosphere, providing additional timeline and altitude margin necessary for landing more massive payloads. This study analyzed the guided entry performance of several low ballistic coefficient vehicle concepts at Mars. A terminal point controller guidance algorithm, based on the Apollo Final Phase algorithm, was used to provide precision targeting capability. Terminal accuracy, peak deceleration, peak heat rate, and integrated heat load were assessed and compared to a traditional Mars entry vehicle concept to determine the effects of lowering the vehicle ballistic coefficient on entry performance. Results indicate that, while terminal accuracy degrades slightly with decreasing ballistic coefficient, the terminal accuracy and other performance metrics remain within reasonable bounds for ballistic coefficients as low as 1 kg/m2 . As such, this investigation demonstrates that from a performance standpoint, guided entry vehicles with low ballistic coefficients (large diameters) may be feasible at Mars. Additionally, flight performance may be improved through the use of guidance schemes designed specifically for low ballistic coefficient vehicles, as well as novel terminal descent systems designed around low ballistic coefficient trajectories

View