Engineering Papers⌕ Search

Engineering topics

Venkatapathy, Ethiraj

Publications and source records attributed to Venkatapathy, Ethiraj.

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Sustaining PICA TPS for Future NASA Robotic Science Missions

Phenolic Impregnated Carbon Ablator (PICA), invented in the mid 1990's, is a low-density ablative thermal protection material proven capable of meeting sample return mission needs from the moon, asteroids, comets and other "unrestricted class V destinations" as well as for Mars. Its low density and efficient performance characteristics have proven effective for use from Discovery to Flagship class missions. It is important that NASA maintain this TPS material capability and ensure its availability for future NASA use. The rayon based carbon precursor raw material used in PICA preform manufacturing required replacement and requalification at least twice in the past 25 years and a third substitution is now needed. The carbon precursor replacement challenge is twofold – the first involves finding a long-term replacement for the current rayon and the second is to assess its future availability periodically to ensure it is sustainable and be alerted if additional replacement efforts need to be initiated. Rayon is no longer a viable process in the US and Europe due to environmental concerns. In the early 80's rayon producers began investigating a new method of producing a cellulosic fiber through a more environmentally responsible process. This cellulosic fiber, lyocell, is a viable replacement precursor for PICA fiberform. This presentation reviews current SMD-PSD funded PICA sustainability activities in ensuring a rayon replacement for the long term is identified and in establishing that the capability of the new PICA derived from an alternative precursor is in family with previous versions of the so called "heritage" PICA.State of the Art Low Density Carbon Phenolic AblatorsStardust SRC post flight withPICA forebody heat shield(0.8m max. diameter)PICA Processing StepsRole of Rayon/Lyocellin PICA.

Stackpoole, Mairead↗
NASA NTRS2018

Time-Varying Entry Heating Profile Replication with a Rotating Arc Jet Test Article

A new approach to arc jet testing that replicates the time-varying conditions of atmospheric entry heating was demonstrated. The concept relies on the spatial variation of heat flux and pressure around a cylindrical test article. The spatial variation is transformed to a temporal variation at one location by rotating the test article during exposure to the arc jet stream. The test article rotation mechanism is based on a programmable stepper motor. An entry heat flux profile was mapped to the cylinders heat flux distribution to determine the rotation angle vs. time executed by the mechanism. A series of arc jet tests with instrumented cylindrical TPS test articles was conducted to prove the concept.

Aerothermodynamics↗
NASA NTRS2018

Studies in Support of Venus Aerocapture Utilizing Drag Modulation

Aerocapture has been extensively studied and these studies have shown the benefit for planetary exploration missions. While the traditional approach to aerocapture with lifting configurations and lift-guided modulations have been assessed to be technologically feasible, aerocapture using purely drag modulation was proposed and studied by Prof. Braun and his students. These studies show that if one can assess the feasibility of aerocapture using drag modulation at Venus, and develop tall pole technologies needed at Venus, then this concept is much easier to execute at all other relevant destinations. Based on the above finding, partnered proposals were submitted by Adam Nelessen at JPL and Ethiraj Venkatapathy at Ames in collaboration with Prof. Braun at the University of Colorado, Boulder (UCB). Under this partnership, Ames Research Center (ARC) is working to address some of the key entry technology challenges associated with drag modulation aerocapture at Venus. Drag modulation aerocapture is a simple, scalable, and likely cost-effective way to enhance planetary science missions. The approach envisioned is to design a small spacecraft, that would most likely be a secondary payload, with a removable drag skirt. The vehicle would enter the atmosphere at Venus with a low ballistic coefficient, decelerate rapidly, drop the skirt resulting in a smaller vehicle with a higher ballistic coefficient which would skip out of the atmosphere and enter into a desired orbit. ARC's role in this collaboration is multifold. First of which is to perform design studies on various pre- and post-jettison geometries utilizing a 3-DOF trajectory code to determine the aerodynamics and aerothermodynamics of the vehicles and evaluate viable thermal protection material system designs. Once these design studies are complete, Ames will then perform higher fidelity CFD and TPS sizing to further design the vehicles. Second, the multi-body separation dynamics of the drag modulation event will be explored using both CFD simulations (CART3-D and US3D) as well as possible ballistic range testing. ARC's tools and expertise have been used to assess and advise on the selection of the separating configuration. In addition to the preliminary evaluation, ARC will provide tools and expertise to UCB team members to further assess aerodynamic interactions between the separating bodies and provide guidance as to the feasibility of stable transition.

Beck, Robin↗
NASA NTRS2018

Sustaining PICA for Future NASA Robotic Science Missions Including NF-4 and Discovery

Phenolic Impregnated Carbon Ablator (PICA), invented in the mid 1990's, is a low-density ablative thermal protection material proven capable of meeting sample return mission needs from the moon, asteroids, comets and other unrestricted class V destinations as well as for Mars. Its low density and efficient performance characteristics have proven effective for use from Discovery to Flag-ship class missions. It is important that NASA maintain this thermal protection material capability and ensure its availability for future NASA use. The rayon based carbon precursor raw material used in PICA preform manufacturing has experienced multiple supply chain issues and required replacement and requalification at least twice in the past 25 years and a third substitution is now needed. The carbon precursor replacement challenge is twofold - the first involves finding a long-term replacement for the current rayon and the second is to assess its future availability periodically to ensure it is sustainable and be alerted if additional replacement efforts need to be initiated. This paper reviews current PICA sustainability activities to identify a rayon replacement and to establish that the capability of the new PICA derived from an alternative precursor is in family with previous versions.

Stackpoole, Mairead↗
NASA NTRS2018

Sustaining PICA for Future NASA Robotic Science Missions Including NF-4 and Discovery

Phenolic Impregnated Carbon Ablator (PICA), invented in the mid 1990's, is a low-density ablative thermal protection material proven capable of meeting sample return mission needs from the moon, asteroids, comets and other unrestricted class V destinations as well as for Mars. Its low density and efficient performance characteristics have proven effective for use from Discovery to Flag-ship class missions. It is important that NASA maintain this thermal protection material capability and ensure its availability for future NASA use. The rayon based carbon precursor raw material used in PICA preform manufacturing has experienced multiple supply chain issues and required replacement and requalification at least twice in the past 25 years and a third substitution is now needed. The carbon precursor replacement challenge is twofold - the first involves finding a long-term replacement for the current rayon and the second is to assess its future availability periodically to ensure it is sustainable and be alerted if additional replacement efforts need to be initiated. This paper reviews current PICA sustainability activities to identify a rayon replacement and to establish that the capability of the new PICA derived from an alternative precursor is in family with previous versions.

Stackpoole, Mairead↗
NASA NTRS2018

TPS for Outer Planets

This invited talk will provide an assessment of the TPS needs for Outer Planet In-situ missions to destinations with atmosphere. The talk will outline the drivers for TPS from destination, science, mission architecture and entry environment. An assessment of the readiness of the TPS, both currently available and under development, for Saturn, Titan, Uranus and Neptune are provided. The challenges related to sustainability of the TPS for future missions are discussed.

Outer Planets↗
NASA NTRS2018

Progress in Manufacturing and Characterizing Domestic Lyocell PICA (PICA-D) and Comparison to Heritage PICA

NASA ARC is working with SMD-PSD to address PICA rayon sustainability concerns. In FY16/17, Lyocell Based PICA (PICA-D) was manufactured and limited testing performed showing it to be a good candidate as a potential replacement for heritage rayon. Establishing PICA-D as a "drop in replacement" will allow missions to depend on and design missions with PICA without any risk typical of a replacement. Establishing the extended capability of PICA-D will allow Sample Return Missions with higher entry speed that were not considered before.

PICA↗
NASA NTRS2018

Overview of Heatshield for Extreme Entry Environment Technology (HEEET)

The Heatshield for Extreme Entry Environment Technology (HEEET) projects objective is to mature a 3-D Woven Thermal Protection System (TPS) to Technical Readiness Level (TRL) 6 to support future NASA missions to destinations such as Venus and Saturn. The scope of the project, status of which will be discussed, encompasses development of manufacturing and integration processes, fabrication of a prototype 1m diameter engineering test unit (ETU) that will undergo a series of structural tests, characterizing material aerothermal performance including development of a material response model, and structural testing and analysis to develop tools to support design and establish system capability.

Driver, David M.↗
NASA NTRS2017

Progress Towards providing Heat-Shield for Extreme Entry Environment Technology (HEEET) for Venus and other New Frontiers Missions

Heat-shield for Extreme Entry Environment Technology (HEEET) has been in development since 2014 with the goal of enabling missions to Venus, Saturn and other high-speed sample return missions. It is offered as a new technology and incentivized for mission use in the New Frontiers 4 AO by NASA. The current plans are to mature the technology to TRL 6 by FY18. The HEEET Team has been working closely with multiple NF-4 proposals to Venus, Saturn and has been supporting recent Ice-Giants mission studies. This presentation will provide progress made to date and the plans for development in FY18.

Ablative thermal protection system↗
NASA NTRS2017

Progress Towards Providing Heat-Shield for Extreme Entry Environment Technology (HEEET) for Venus and Other New Frontiers Missions

Heat-shield for Extreme Entry Environment Technology (HEEET) has been in development since 2014 with the goal of enabling missions to Venus, Saturn and other high-speed sample return missions. It is offered as a new technology and incentivized for mission use in the New Frontiers 4 AO by NASA. The current plans are to mature the technology to TRL 6 by FY’18. The HEEET Team has been working closely with multiple NF-4 proposals to Venus, Saturn and has been supporting recent Ice-Giants mission studies. This presentation will provide progress made to date and the plans for development in FY’18.

Ablative thermal protection system↗
NASA NTRS2017

NASA's Advanced TPS Materials and Technology Development: Multi-Functional Materials and Systems for Space Exploration

NASA's future missions will be more demanding. They require materials to be mass efficient, robust, multi-functional, scalable and able to be integrated with other subsystems to enable innovative missions to accomplish future science missions. Thermal protection systems and materials (TPSM) are critical for the robotic and human exploration of the solar system when it involves entry. TPSM is a single string system with no back-up. Mass efficiency and robustness are required. Integration of TPSM with the aeroshell is both a challenge and an opportunity. Since 2010, NASA's Space Technology Mission Directorate has invested in innovative new materials and systems across a spectrum of game changing technologies. In this keynote address, we plan to highlight and present our successful approaches utilized in developing four different materials and system technologies that use innovative new manufacturing techniques to meet mission needs. 3-D weaving and felt manufacturing allowed us to successfully propose new ways of addressing TPSM challenges. In the 3-D MAT project, we developed and delivered a multi-functional TPS materials solution, in under three years that is an enabler for Lunar Capable Orion Spacecraft. Under the HEEET project, we are developing a robust heat-shield that can withstand extreme entry conditions, both thermally and mechanically, for entry at Venus, Saturn or higher speed sample return missions. The improved efficiency of HEEET allows science missions entry at much reduced G'loads enabling delicate science instruments to be used. The ADEPT concept is a foldable and deployable entry system and the critical component is a multi-functional fabric that is foldable and deployable and also functions as a mechanical aeroshell and a TPS. The fourth technology we will highlight involves felt to address integration challenges of rigid ablative system such as PICA that was used on MSL. The felt technology allows us to develop a compliant TPS for easy integration. The above four technology developments have focused on mission infusion as the success criteria. These technologies are in different stages of mission infusion. These innovations have led to new mission concepts to be proposed in the future. In our keynote address we will present approaches we have employed throughout the project to create the bridge to transition from low TRL to mission infusion and to overcome the traditional TRL valley of death.

TPS↗
NASA NTRS2017

Thermal Protection for Mars Sample Return Earth Entry Vehicle: A Grand Challenge for Design Methodology and Reliability Verification

Mars Sample Return is our Grand Challenge for the coming decade. TPS (Thermal Protection System) nominal performance is not the key challenge. The main difficulty for designers is the need to verify unprecedented reliability for the entry system: current guidelines for prevention of backward contamination require that the probability of spores larger than 1 micron diameter escaping into the Earth environment be lower than 1 million for the entire system, and the allocation to TPS would be more stringent than that. For reference, the reliability allocation for Orion TPS is closer to 11000, and the demonstrated reliability for previous human Earth return systems was closer to 1100. Improving reliability by more than 3 orders of magnitude is a grand challenge indeed. The TPS community must embrace the possibility of new architectures that are focused on reliability above thermal performance and mass efficiency. MSR (Mars Sample Return) EEV (Earth Entry Vehicle) will be hit with MMOD (Micrometeoroid and Orbital Debris) prior to reentry. A chute-less aero-shell design which allows for self-righting shape was baselined in prior MSR studies, with the assumption that a passive system will maximize EEV robustness. Hence the aero-shell along with the TPS has to take ground impact and not break apart. System verification will require testing to establish ablative performance and thermal failure but also testing of damage from MMOD, and structural performance at ground impact. Mission requirements will demand analysis, testing and verification that are focused on establishing reliability of the design. In this proposed talk, we will focus on the grand challenge of MSR EEV TPS and the need for innovative approaches to address challenges in modeling, testing, manufacturing and verification.

Design and Verification for Reliability↗
NASA NTRS2017

IPPW Enabled International Collaborations in EDL Lessons Learned and Recommendations:

The International Planetary Probe Workshop (IPPW) is a forum for exchanging information and encourage collaboration. The IPPW-14 (2017) in its 14th year and attracts participants mainly from US and Europe. The authors of this proposed talk are exploring and have established international collaboration in multiple areas of interest to IPPW community. The authors will present examples that illustrate the motivations for the partnership, the unique capabilities and the potential benefits of international collaboration and how to approach the collaboration in order to overcome the challenges.

Venkatapathy, Ethiraj↗
NASA NTRS2017

Contribution of Asteroid Generated Tsunami to the Impact Hazard

The long-standing uncertainty about the importance of asteroid-generated tsunami was addressed at a workshop in August 2016, co-sponsored by NASA and NOAA. Experts from NASA, NOAA, the DoE tri-labs (LLNL, SNL, and LANL), DHS, FEMA, and academia addressed the hazard of tsunami created by asteroid impacts, focusing primarily on NEAs with diameter less than 250m. Participants jointly identified key issues and shared information for nearly a year to coordinate their results for discussion at the workshop. They used modern computational tools to examine 1) Near-field wave generation by the impact; 2) Long-distance wave propagation; 3) Damage from coastal run-up and inundation, and associated hazard. The workshop resulted in broad consensus that the asteroid impact tsunami threat is not as great as previously thought.

Asteroid↗
NASA NTRS2017

In Pursuit of Improving Airburst and Ground Damage Predictions: Recent Advances in Multi-Body Aerodynamic Testing and Computational Tools Validation

An airburst from a large asteroid during entry can cause significant ground damage. The damage depends on the energy and the altitude of airburst. Breakup of asteroids into fragments and their lateral spread have been observed. Modeling the underlying physics of fragmented bodies interacting at hypersonic speeds and the spread of fragments is needed for a true predictive capability. Current models use heuristic arguments and assumptions such as pancaking or point source explosive energy release at pre-determined altitude or an assumed fragmentation spread rate to predict airburst damage. A multi-year collaboration between German Aerospace Center (DLR) and NASA has been established to develop validated computational tools to address the above challenge.

Asteroid↗