10th International Planetary Probe Workshop HIAD Earth Atmospheric Reentry Test Flexible Thermal Protection Systems Trade Studies for HIAD Earth Atmospheric Reentry Test Vehicle 10th International Planetary Probe Workshop 17-20 June 2013, San Jose Joseph A. Del Corso, John A. Dec, Alireza Mazaheri, Aaron D. Olds, Nathaniel J. Mesick, Walter E. Bruce III, Stephen J. Hughes, Henry S. Wright, F. McNeil Cheatwood NASA Langley Research Center Joseph.A.DelCorso@nasa.gov

HIAD Overview Mission Infusion Flexible TPS (F-TPS) Development and Qualification Sub-Orbital Flight Testing System Demonstration Robotic Missions IRVE-II Earth Return IRVE-3 HIAD Earth Atmospheric Re-entry Test (HEART) Inflatable Re-entry Vehicle Experiments DoD Applications Tech Development & Risk Reduction 2012 2013 F-TPS advances (combination of ground and flight testing) readies technology for mission infusion

F-TPS Background F-TPS is modular in that it utilizes different materials for each function Outer high temperature fabric Insulation Impermeable gas barrier 3

The HEART Concept The HEART HIAD is a proposed secondary payload on the Orbital Sciences Cygnus spacecraft. Enhanced Antares launch vehicle, but paired with a Standard Pressurized Cargo Module (change to CRS contract) ISS utilization and mission implementation via the Cargo Resupply Services (CRS) contract require very early mission definition, interface development, and planning. HEART Mission Goal Develop and demonstrate a relevant-scale HIAD system in an operational environment. HEART Mission Objectives Demonstrate manufacturing processes of a large-scale HIAD. Demonstrate successful operation of a large-scale HIAD throughout the planned operational environments. Validate HIAD predictive tools (structural, thermal, flight dynamics). HEART 8 to 10 m Diameter IRVE-3 3 m Diameter HEART Dramatically Increases HIAD Scale, Entry Mass and Entry Environment Capabilities Capability IRVE-II IRVE-3 HEART HIAD Diameter (m) 3 8 to 10 Entry Mass (kg) 125 300 5500 Peak Heat Rate (W/cm2) 2 15 30 to 50 Total Heat Load (kJ/cm2) 0.02 0.2 5.0

HEART Launch-to-Flight Configurations Cruise Configuration (to and from ISS) Pressurized Cargo Module (PCM, Orbital Sciences) Stowed HEART HIAD Module (LaRC) Flexible Thermal Protection System (LaRC) Enhanced Antares Fairing (Orbital Sciences) Interstage Structure (Orbital Sciences) Interstage to PCM Separation Plane (Orbital Sciences) If this concept is important and has bold assertions, they must stand out in the description. The description should reflect confidence that the concept is based on a strong story that has depth. This slide expands on the “PROJECT DESCRIPTION/APPROACH” section of the “Penta” Chart from the Introduction. Cygnus Service Module (Orbital Sciences) Antares to Cygnus Separation Plane (Orbital Sciences) Inflatable Structure (LaRC) Reentry Configuration Launch Configuration

OML Trade Study Background Baseline HEART OML is 55-deg cone with non-spherical nose Aerothermal analyses indicate peak heat rate (and resultant surface temperature) could exceed current understood limit of the baseline F-TPS outer layer, and place more demands of the insulative layer. Options: change OML (cone diameter, cone angle, nose radius, shoulder radius), switch to advanced (Gen2) F-TPS materials, or reduce entry mass

HEART OML Configurations Matrix Cone Angle (deg) Nose Radius (m) D = 7 m D = 8 m D = 9 m D = 10 m 55 -- D/5 D/5.6 60 D/3.5 D/4 D/4.4 D/4.9 65 D/3 & D/4 D/3.4 & D/4 D/4.3 70 D/3.5 & D/4 55 (baseline) Ellipsoidal-ish Additional length available with the Cygnus spacecraft allows spherical nose--function of vehicle diameter (D) 20 OML configurations initially considered 7-m configuration quickly eliminated due to excessive heating, flow impingement and aero stability concerns

OML Trade Study Re-entry Trajectories POST2 3 degree-of-freedom simulation 5500 kg entry vehicle 55 to 70 deg cone half angle 8 to 10 m diameter Ballistic entry (0° angle of attack) Newtonian drag coefficients Deorbit from 421x180 km orbit 50 km perigee target

Aerothermal Analysis Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) CFD code utilized Only ballistic entry conditions considered (no lift). Surface assumed fully-catalytic with the temperature-dependent emissivity. Radiative equilibrium surface temperature assumed. Solutions obtained for both laminar and fully-turbulent (Cebeci-Smith) flows. Radiative heating computations obtained with 11-species, 2-temperature non-equilibrium air models. Only laminar flow was simulated for radiative heating estimation. Flight indicators (laminar and fully-turbulent) were generated for the solid nose cap and the inflatable portion of each configuration, and then implemented in POST2. For each flight heating indicator, corresponding arc-jet heater settings were defined based on the computed flight-to-ground correlations

Surface Temperature Results Max D (m) Cone Angle (deg) Nose Radius Nose Heating (W/cm2) Nextel Nose T(K) SiC IAD Heating (W/cm2) IAD T(K) 8 60 D/4 64 2060 1669 61 1920 1555 65 D/3.5 2020 1636 57 1880 1523 67 2100 1701 56 1860 1507 70 D/3 54 1990 1612 46 1810 1466 62 2030 1644 45 1805 1462 9 55 D/5 2070 1677 52 D/4.4 2010 1628 49 1875 1519 2000 1620 43 1800 1458 50 1970 1596 37 1730 1401 53 41 1770 1434 10 D/5.6 47 1820 1474 D/4.9 D/4.3 44 1850 1499 33 1660 1345 1900 1539 36 1740 1409 8.3 Baseline --- Approximate Temperature Limits: Nextel–1723K, SiC–2023K 10

Ground Testing at Large-Core Arc Tunnel The Boeing Company Facility Ground Testing Test coupon samples at stagnation and shearing conditions Test at relevant mission profile heat flux and pressure LCAT – Huels arc heater 18” and 27” cathodes with secondary air and 12” mixing section Heat flux range 5-150 W/cm2 Surface pressure range 1-9 kPa Shear range 30-270 Pa Reacting flow Arc 11

Nominal Trajectory (Vehicle Stagnation Point) Profile Test Conditions Initial Heating 17 W/cm2 Peak Heating 50 W/cm2 20 W/cm2 30 W/cm2 40 W/cm2 Side View

Baseline F-TPS Sample Performance   Sting Arm 2  Units Test Condition (Nominal Cold Wall Profile) 50 (W/cm2) Measured Peak Heat Flux 50.5 Test Duration (Full profile completed) 300 (sec) Time to 250°C (TC8K, post-profile exposure) 373 Max Temperature Reached (post exposure) 317 (°C) Run Performance Weave appeared to be slightly more porous near the peak heating of the test, but was intact HEART Baseline Nextel 440 BF-20 Pyrogel 2250 KKL Sting Arm 2 Pre-Test Post-Test 13

Option A F-TPS Sample Performance   Sting Arm 1 Sting Arm 2  Units Test Condition (Nominal Cold Wall Profile) 50 (W/cm2) Measured Peak Heat Flux 53.1 Test Duration (Full profile completed) 300 (sec) Time to 250°C (TC8K, post-profile exposure) 501 419 Max Temperature Reached (post exposure) 253 275 (°C) Run Performance Well behaved and was tested for the entire duration. Option A SiC Pyrogel 2250 KKL Post-Test Post-Test Sting Arm 1 Sting Arm 2 14

Option B F-TPS Sample Performance   Sting Arm 1 Sting Arm 2  Units Test Condition (Nominal Cold Wall Profile) 50 (W/cm2) Measured Peak Heat Flux 51.9 Test Duration (Full profile completed) 300 (sec) Time to 250°C (TC8K, post-profile exposure) 329 326 Max Temperature Reached (post exposure) 371 378 (°C) Run Performance Well behaved and was tested for the entire duration. Option B Saffil 96 Pyrogel 2250 KKL SiC Post-Test Post-Test Sting Arm 1 Sting Arm 2 15

Ongoing F-TPS Development within HIAD Project Advancing second generation materials Developing advanced SiC weaving, and investigating manufacturing, and handle-ability FTPS investigating graphite and carbon felt insulators at LCAT Material manufacturing processes are consistent and repeatable Materials have thermophysical characteristics similar to Saffil Materials are mechanically viable for packing Materials are similar to pyrogel in mechanical durability and handling (carbon slightly more susceptible to shearing tearing loads) but no particulates Investments in third generation insulator development Polyimides (GRC), OFI (Miller Inc.), APA (GRC) Opacified Fibrous Insulation – OFI Alumina Paper Aerogel - APA 16

Conclusions Increased cone angle and nose radius offers the lowest peak heating solution for the aeroshell, however, structural stability concerns need to be addressed for cone angles greater than 60 deg. For HEART, the aeroshell diameter should be greater than 8 meters to minimize payload impingement, reduce forebody heat rates, and improve aero stability. Due to its relatively low emissivity, F-TPS configurations using the Nextel BF-20 fabric realize higher surface temperatures than experienced by SiC (which has a higher emissivity). F-TPS designs using Nextel BF-20 fabric may be possible for configurations with low peak heating. However, design margin may be unacceptable. F-TPS designs using SiC fabric are suitable for all HEART configurations considered in the study with an expectation of acceptable design margin. Arc-jet test results for HEART representative heating profiles verify that our selection for F-TPS materials will survive expected re-entry conditions at the design back-face temperature. 17