1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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 W/cm2
Surface pressure range 1-9 kPa
Shear range Pa
Reacting flow
Arc 11

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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