Parul Agrawal

Small Probe Reentry Investigation for TPS Engineering (SPRITE)

Small Probe Reentry Investigation for TPS Engineering (SPRITE) is a novel concept for a comparatively low-cost means of certifying thermal protection system (TPS) materials for spaceflight. By developing a fully instrumented small-scale test platform that can be tested both in arc-jet facilities and in flight, SPRITE promises to improve the ground-to-flight traceability of TPS qualification programs by implementing the NASA “test-like-you-fly” policy. This paper discusses the design and manufacture of the proof-of-concept SPRITE test articles, development and capabilities of the SPRITE flight-like data acquisition system, and fidelity of the design tools used in the effort. With the successful completion of this stage of the SPRITE project, the next test article to be built will have a hemispherical backshell as originally designed for flight stability. Unlike the initial proof-of-concept probes, TPS for the next test article will be scaled according to current margins policies for arc-jet testing at relevant flight-like aerothermal environments. At the conclusion of the ground test campaign, SPRITE probes will be ready for flight testing and, ultimately, acceptance into future mission planning where they will contribute to more affordable access to space for both large and small science payloads.

Thermal Soak Analysis of Earth Entry Vehicles

The Multi-Mission Earth Entry Vehicle project is developing an integrated tool called “Multi Mission System Analysis for Planetary Entry Descent and Landing” that will provide key technology solutions including mass sizing, aerodynamics, aerothermodynamics, and thermal and structural analysis for any given sample return mission. Thermal soak analysis and temperature predictions of various components including the payload container of the entry vehicle are part of the solution that this tool will offer to mission designers. The present paper focuses on the thermal soak analysis of an entry vehicle design based on the Mars Sample Return entry vehicle geometry and discusses a technical approach to develop parametric models for thermal soak analysis that will be integrated into the tool.

Investigation of Performance Envelope for Phenolic Impregnated Carbon Ablator (PICA)

The present work provides the results of a short exploratory study on the performance of Phenolic Impregnated Carbon Ablator, or PICA, at high heat flux and pressure in an arcjet facility at NASA Ames Research Center. The primary objective of the study was to explore the thermal response of PICA at cold-wall heat fluxes well in excess of 1500 W/cm (exp 2). Based on the results of a series of flow simulations, multiple PICA samples were tested at an estimated cold wall heat flux and stagnation pressure of 1800 W/cm (exp 2) and 130 kPa, respectively. All samples survived the test, and no failure was observed either during or after the exposure. The results indicate that PICA has a potential to perform well at environments with significantly higher heat flux and pressure than it has currently been flown.

Atmospheric entry studies for Uranus

The present paper describes parametric studies conducted to define the Uranus entry trade space. Two different arrival opportunities in 2029 and 2043, corresponding to launches in 2021 and 2034, respectively, are considered in the present study. These two launch windows factor in the 84-year orbital period, significant axial tilt, and the wide ring system of Uranus. As part of this study, an improved engineering model is developed for the Uranus atmosphere. This improved model is based on reconciliation of data available in the published literature and covers an altitude range of 0 km (1 bar pressure) to 5000 km. Two different entry scenarios are considered: 1) direct ballistic entry, and 2) aerocapture followed by entry from orbit. For ballistic entry a range of entry flight path angles are considered for probe entry masses ranging from 130 kg to 300 kg and diameters ranging from 0.8 m (Pioneer-Venus small probe scale) to 1.3 m (Galileo scale). The larger probes, which offer a larger packing volume, are considered in an attempt to accommodate more scientific instruments. For aerocapture a single case is studied to explore the feasibility and benefits of this option.

Validation Testing of a New Dual Heat Pulse, Dual Layer Thermal Protection System Applicable to Human Mars Entry, Descent and Landing

In NASA’s quest to find a system capable of delivering 40 metric ton payloads to the surface of Mars, one proposed mission scenario employs a 10 x 29 meter mid lift-over-drag (L/D) vehicle with a dual heat pulse capable thermal protection system (TPS) that achieves orbit via aerocapture, cools down there, and then enters, descends and lands. This paper discusses the simulated dual heat pulse thermal testing conducted in the Ames arcjet complex of a dual layer, phenolic impregnated carbon ablator (PICA) atop a LI-900 (Shuttle insulating tile) TPS attached with large honeycomb (~ 5 cm), proposed for this mission scenario. Test results and recommendations for future work on the maturation of the dual heat pulse TPS technology are provided.

Arcjet Ablation of Stony and Iron Meteorites

A test campaign was conducted placing meteorites in the 60 MW plasma Arcjet Interaction Heating Facility at NASA Ames Research Center, with the aim to achieve flight-relevant conditions for asteroid impacts in Earths atmosphere and to provide insight into how meteoritic materials respond to extreme entry heating environments. The test conditions at heat flux of 4000 W/m2 and 140 kPa stagnation pressure are comparable to those experienced by a 30-meter diameter asteroid moving at 20 km/s velocity at 65 km altitude in the Earths atmosphere. Test objects were a stony type H5 ordinary chondrite (Tamdakht) and an iron type IAB-MG meteorite (Campo Del Cielo), and included the terrestrial analogs Dense Flood Basalt and Fused Silica. All samples were exposed for only a few seconds in the plasma stream. Significant melt flow and vaporization was observed for both the stony and iron meteorites during exposure. Mass loss from spallation of fragments was also observed. Vapor emitted atomic lines from alkali metals and iron, but did not emit the expected MgO molecular band emissions. The meteoritic melts flowed more rapidly, indicating lower viscosity, than those of Fused Silica. The surface recession was mapped. The effective heat of ablation derived from this showed that ablation under these conditions occurred in the melt-dominated regime. Ablation parameters have an effect on ground damage estimates. A bias in ablation parameters towards the melt-dominated regime would imply that impacting asteroids survive to lower altitude, and therefore could possibly have airbursts with a larger ground damage footprint.

Comet surface sample return: Sample chain system overview

A system overview of the sample chain planned for use on a Comet Surface Sample Return mission is provided. The key actions that must be performed in order to acquire, condition, and protect the surface samples are described. Significant mission events are noted, especially with regard to their implications to successful sample return. Finally, recovery activities are discussed as these represent the initial steps taken in the terrestrial curatorial process.