Aerospace Engineering Commons^™

Modeling Of Heat Transfer Attenuation By Ablative Gases During The Stardust Re-Entry, Alexandre Martin, Iain D. Boyd

Ablation Workshop

The great majority of modern space vehicles designed for planetary exploration use ablative materials to protect the payload against the high heating environment experienced during re-entry. In order to properly model and predict the aerothermal environment of the vehicle, it is imperative to account for the gases produced by ablation processes. In the case of charring ablators, where an inner resin is pyrolyzed at a relatively low temperature, the composition of the gas expelled into the boundary layer is complex and may lead to thermal chemical reactions that cannot be captured with simple flow chemistry models. In order to obtain …

Ablation Modeling Of A Solid Rocket Nozzle, Mark E. Ewing, Galen H. Richards, Micheal P. Iverson, Daron A. Isaac

Ablation Workshop

No abstract provided.

Definition Of Ablation Test-Case Series #3, Tom Van Eekelen, Jean R. Lachaud, Alexandre Martin, Ioana Cozmuta

Ablation Workshop

The test-case series #3 will be a further extension of the tests defined within the framework of the NASA ablation modelling workshops. In order to reduce the amount of work, all tests within test-case series #3, will use the TACOT material defined by Lachaud et al. The main goal of this new series, is to test the 3D modelling capabilities of the participating codes. The first 1D results were presented at the 4th Ablation workshop, and together with the results of the second test-case series, will be discussed and analyzed more thoroughly at the 5th Ablation Workshop, Feb. 28- March …

Ablation Test Case Series #2. Be13 Results, Jean-Marc Bouilly

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Itrac Results, Mark E. Ewing

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Mopar: Results For The Inter-Code Calibration, Jonathan E. Wiebenga, Iain D. Boyd, Alexandre Martin

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Test Case Baseline Results, Tim Risch, Chris Kostyk

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Amaryllis Results, Tom Van Eekelen, Jean-Marc Bouilly

Ablation Workshop

No abstract provided.

Ablation Test Case Series #2. Are The Test Problems Well Posed With Ch = Cm = 0?, Ben F. Blackwell

Ablation Workshop

No abstract provided.

Prediction Of Tacot Decomposition Using The Chaleur Code, Ben F. Blackwell, Micah Howard

Ablation Workshop

This talk will briefly discuss the ablation thermochemistry data used for the TACOT code comparison test cases. Three areas of interest will be highlighted: codes and numerical methods for solving the thermochemical equilibrium problem, differences in ablation thermochemistry data (Bc and enthalpy) when using the CEA and JANAF databases, and the effect of the choice of pyrolysis gas species will be discussed.

A Perspective On The Design And Development Of The Spacex Dragon Spacecraft Heatshield, Daniel J. Rasky

Ablation Workshop

In December, 2010, Space Exploration Technologies (SpaceX) successfully orbited, re-entered and recovered their Dragon spacecraft, on an almost “picture perfect” first full mission. Earlier in 2009, SpaceX, announced the passing of a significant technical milestone with the successful arc jet testing of a their new high performance heat shield material, called PICA-X, which provided the primary (forebody) thermal protection for Dragon.

In 2008 and 2009, Dr. Rasky worked closely with SpaceX on the Dragon heatshield design and also developing the ability to manufacture PICA-X. The “X” stands for the SpaceX-developed variants that have several improved properties and greater ease of …

The Mysteries Of Real Materials, Bernard Laub

Ablation Workshop

The presentation will consist in showing arc jet data mysterious to the modelers. It will show a short movie (10-20 sec) of an arc jet test where a material exhibited a failure mode that nobody understands followed by thermocouple data from arc jet tests on another material of interest in which the T/Cs exhibit repeatable, consistent, fascinating yet frustrating response characteristics that have the modelers stumped. This all happens between RT and 200 F. Doesnt sound important? Unless we figure out what it is and can model it, we can’t size the TPS with any confidence.

Direct Observation Of Mechanical Ablation, Charles Powars, Craig Derbidge

Ablation Workshop

This presentation describes an experiment that solved a mysterious problem affecting the material that protects solid rocket motor cases from burning propellant gases: Why was the ablation of this material in the forward dome region of recovered flight test motors as much as 2x that observed in full-scale ground test firings?

Heat transfer to the forward dome elastomeric insulation is predominantly radiation from the burning propellant. The 15- kW CO2 laser at the Wright Patterson AFB Laser Hardened Material Evaluation Laboratory (LHMEL) was used to provide uniform incident radiation from 200 to 400 W/cm2. We suspected that the rocket acceleration …

Characterization Of Material Response During Arc-Jet Testing With Optical Methods–Status And Perspectives, Michael Winter

Ablation Workshop

The characterization of ablation and recession of heat shield materials during arc jet testing is an important step towards understanding the governing processes during these tests and therefore for a successful extrapolation of ground test data to flight. The behavior of ablative heat shield materials in a ground-based arc jet facility is usually monitored through measurement of temperature distributions (across the surface and in-depth), and through measurement of the final surface recession [1, 2]. These measurements are then used to calibrate/validate materials thermal response codes, which have mathematical models with reasonably good fidelity to the physics and chemistry of ablation, …

Sprite: A Tps Test Bed For Ground And Flight, P. Agrawal, A. Cassell, N. Mangini, K. Peterson, Dinesh K. Prabhu, K. Skokova, G. Swanson, D. M. Empey, S. Gorbunov, A. Howard, J. Arnold, E. Venkatapathy

Ablation Workshop

Engineers in the Entry Systems and Technology Division at NASA Ames Research Center developed a fully instrumented, small atmospheric entry probe called SPRITE (Small Probe Reentry Investigation for TPS Engineering). SPRITE, conceived as a flight test bed for thermal protection materials, was tested at full scale in an arc-jet facility so that the aerothermal environments the probe experiences over portions of its flight trajectory and in the arc-jet are similar. This ground-to-flight traceability enhances the ability of mission designers to evaluate margins needed in the design of thermal protection systems (TPS) of larger scale atmospheric entry vehicles.

Numerical Investigation Of Three-Dimensional Effects Within A Charring Ablator, Alexandre Martin, Ovais U. Khan, Huai-Bao Zhang

Ablation Workshop

Re-entry of a spacecraft occurs at hypersonic regime where flow field is extremely complex. High temperature gradients occurring in the shock-layer region ionizes and dissociates the air. Even if a large portion of heat generated during this process is convected away in the surrounding air, a fraction of it is still transferred to the vehicle. Therefore, it is important to protect the vehicle with a suitable kind of shielding. Of many techniques available today, the use of ablator material is increasing in popularity. The basic idea behind an ablating heat shield is that the energy incident on the spacecraft is …

Development And Validation Of Sacram: A Swiss Approach To The Computational Response Of An Ablative Material, Ojas Joshi, Georges Duffa, Pénélope Leyland

Ablation Workshop

Future space exploration missions foresee high-speed entries into planetary atmospheres. These latter imply extreme thermal conditions to which the space vehicle is exposed to, and require an appropriate thermal protection system (TPS). The interest of the scientific community in modelling and testing of materials that compose the TPS has hence greatly increased over the past few years. Since a complete set of material properties is not available in open literature, it is difficult to numerically rebuild experiments. The inter-code comparison exercise proposed by the AF/SNL/NASA Ablation Workshop aims to give a baseline platform for ablation code calibration, with a complete …

Advanced Thermal Protection Systems (Tps) And Transition Analysis: Unique Experimental Capabilities And Current Research Efforts At The University Of Texas At Arlington, Matthew Crisanti, Cody Ground, Stefano Gulli, Jared Poempipatana, Luca Maddalena

Ablation Workshop

A unique experimental capability in the academic panorama is the 1.6 MW-classic arc-jet facility located at the Aerodynamics Research Center of the University of Texas at Arlington. The arc-heated wind tunnel has recently been refurbished and repurposed (extended testing time of the order of minutes and testing gas-composition control) for the study and characterization of the aerothermal response of TPS candidate materials for sustained hypersonic flight.

Experimental Investigation Of Blowing Effects On Turbulent Flow Over A Rough Surface, Mark A. Miller, Sean C. C. Bailey, Alexandre Martin

Ablation Workshop

Entry of spacecraft into an atmosphere occurs at hypersonic speeds, extremely complex flow fields, with aerothermodynamic effects which can cause the surface to be subjected to extreme heating. It is therefore important to protect the vehicle and its payload using a thermal protection system (TPS). Heat shields, which are an important part of a TPS, can be of either ablative or non-ablative types. For an ablative TPS, the energy is dissipated through surface material charring and ablation, as well as releasing gasses which serve to carry energy away from the TPS and thus reduce the total heat flux into the …

Computational Chemistry Modelling Of The Oxidation Of Highly Oriented Pyrolitic Graphite (Hopg), Savio Poovathingal, Thomas E. Schwartzentruber

Ablation Workshop

Under high heat flux, carbon based Thermal Protection Systems (TPS) are observed to rapidly ablate and an accurate characterization is essential to their design. Dissociated oxygen atoms (from the gas phase) striking the surface of TPS could lead to several possibilites. The O atom could adsorb on the surface, recombine with another O atom to form O2 and oxidize the surface to produce CO or CO2 resulting in recession of the surface (ablation). The goal is to predict finite rate models for these reactions which could be incorporated into CFD and DSMC solvers. Our efforts are to predict the rates …