Phenolic Impregnated Carbon Ablator (PICA) is a low-density ablator that has been used as the planetary entry heatshield for several NASA missions since 1999. Due to the obsolescence of the input fiber source, new PICA materials were developed using Lyocell, a domestic rayon fiber source. Results are presented from this effort. Manufacturing included fiber conversion, fabrication of tile component and near net shaped heatshield preforms, and conversion to PICA materials. Thermal, mechanical, and representative environment arc-jet testing have been conducted. Initial testing indicates comparable performance with respect to heritage PICA material, and likely "drop-in" replacement for future NASA mission needs

Gasch, Matthew J.

Stackpoole, Margaret Mairead

Venkatapathy, Ethiraj

Violette, Steven

NASA Technical Reports Server

Entry Systems and Technology Division
Development of Lyocell based Phenolic Impregnated 
Carbon Ablator (PICA-D)  for Future NASA Missions
PICA-D and Three Exciting NASA missions
Mairead Stackpoole, Matt Gasch and Ethiraj Venkatapathy, 
NASA Ames Research Center, Moffett Field, CA 94035
Steve Violette, 
Fiber Materials Inc, Biddeford, ME 04005 
Presented at NSMMS and CRASTE, Henderson NV June 24-27 2019
https://ntrs.nasa.gov/search.jsp?R=20190028255 2019-09-26T20:09:15+00:00Z
Entry Systems and Technology Division
Outline
• Background
– Heritage PICA
– PICA Sustainability Challenge
• PICA-D and Three Exciting NASA missions
• Sustainability
– Lyocell – an alternative precursor to rayon
– PICA Manufacturing
• Establishment of PICA-D as a Replacement for Heritage PICA
– Lyocell Fiberform/PICA Billet and Near Net Shape Cast Processing
– PICA-D Arc Jet Campaign
– Establish PICA-D as a drop-in replacement for Heritage PICA
– Establish the Expanded Capability (Extensibility) of PICA-D
• Summary
• Acknowledgements
2
Entry Systems and Technology Division
Background – PICA
State of the Art Low Density Carbon Phenolic Ablators
Stardust forebody TPS. 
(~0.8m diameter)
MSL Heat Shield 
(4.5m diameter)
• Phenolic Impregnated Carbon Ablator (PICA) 
– first used as forebody single piece heatshield for 
Stardust
• Low density coupled with efficient ablative 
capability at medium-high heat fluxes
• Since Stardust-
– Under the Orion program PICA was shown to be 
capable for both ISS and lunar return missions 
but was not selected as the baseline TPS
– PICA was transitioned to Mars Science Lab 
(MSL) post CDR in a tiled configuration  when 
the mission environments went beyond the 
capabilities of SLA561V
– OSIRIS-REx sample return capsule as a single 
piece 
• On Dec. 3, 2018, the OSIRIS-REx spacecraft arrived at its target, 
near-Earth asteroid Bennu
3
OSIRIS-REx forebody 
TPS. (~0.8m diameter)
Bennu taken by the OSIRIS-
REx spacecraft from a 
distance of ~ 50 miles
https://www.nasa.gov/osiris-rex
Entry Systems and Technology Division
Challenges with PICA Sustainability
• In 2016 NASA learned that the “heritage” rayon used in PICA was ceasing production, leading to a flight-qualified 
PICA sustainability concern
• The carbon fiber precursor for PICA has become obsolete twice since the material was developed and used 
on Stardust, so a secure source is essential to maintain PICA capabilities for future missions
• In FY16/17, NASA ARC was funded by the Planetary Science Division of the Science Mission Directorate to 
address PICA rayon sustainability
• Lyocell Based PICA (PICA-D) was manufactured and limited testing performed – initial results indicate Lyocell is a 
good candidate as a potential replacement for heritage rayon
4
Mission/ Project Precusror type Rayon Sustainability Changes /Updates to PICA
Stardust Near Net 
Shape (NNS)
Liberty rayon US source – production ceased in 
the 90s
Developing process to fabricate NNS within the density specification 
required
Orion CEV ADP -
billets
Multiple sources –
settled on Sniace
Multiple international sources 
evaluated
Optimized densification process for billets, tested the bounds of the 
density specification and the influence on performance / properties
MSL- billets Sniace rayon international source – production 
ceased in ~ 2017
Leveraged ADP data to allow use on MSL
OSIRIS Rex NNS Sniace rayon international source – production 
ceased in ~ 2017
Spec tightened over Stardust for NNS casting range . Phenolic 
adjustments based on lessons learned from ADP/MSL
M2020 - billets Sniace rayon –
source depleted
international source – production 
ceased in ~ 2017
Leveraged MSL
PICA-D billets Lyocell Domestic/international sister 
plants. Greener processing
ADP/MSL specification range
PICA-D NNS Lyocell Domestic/international sister 
plants. Greener processing
Leveraged OSIRIS REx/MSL
PICA-D = Domestically sourced lyocell derived PICA
PICA = Rayon derived PICA
Entry Systems and Technology Division
PICA-D and Three Exciting NASA missions 
– Mars Sample Return Sample Retrieval Lander (MSR SRL) 
– Mars Sample Return Earth Entry Vehicle (MSR EEV)
– Dragonfly 
Mission timelines highlight why a long-term sustainable 
PICA TPS option is needed
5
Entry Systems and Technology Division
Mars Sample Return Campaign
6Courtesy: Jet Propulsion Laboratory
Entry Systems and Technology Division
Mars2020 and Sample Retrieval Lander (SRL)
7
Cruise & EDL
Platform
Sample Fetch Rover
Mars Ascent Vehicle
(JPL reference concept)
SRL Mission
Orbiting Sample
Rover with science 
instruments will collect 
samples from the Martian 
surface and deposit tubes 
filled with samples at 
location for sample fetch 
rover to collect
M2020 Mission
• 4.5m tiled configuration
• Last sniace rayon mission
• 5+m tiled configuration
• Lyocell derived PICA
• Vehicle has a different shape than Mars 2020 
• Entry environment in family with Mars 2020/ MSL 
Courtesy: Jet Propulsion Laboratory
• MSL “built to print” heatshield
Entry Systems and Technology Division
MSR Earth Entry Vehicle (EEV)
8
Orbiting Sample Capture
• Single piece PICA-D considered for MSR EEV foreboby
• Requirements for MSR EEV – up to 1.4m which is greater than Stardust (0.8m)
• Leveraging PICA-D for manufacturing scale-up demonstration
• Tiled backshell PICA baselined
• Expected conditions (~1600 W/cm2, ~80kPa, ~1000 Pa shear)
• PICA performance beyond thermal needs to be assessed - potential MMOD impact and 
ground impact
EEV Aeroshell
Micro-Meteoroid Garage
Secondary 
Containment Vessel 
Body
Orbiting Sample 
Sealed Inside 
Primary Containment 
Vessel
• ~ 1.4m single piece
• Lyocell derived PICA
Courtesy: Jet Propulsion Laboratory
Entry Systems and Technology Division
Dragonfly
• Mobile robotic rotorcraft lander to Titan, 
• Study prebiotic chemistry and 
extraterrestrial habitability at various 
locations 
• Perform vertical-takeoff and landings
9
• Dragonfly forebody TPS (~4 m diameter)
• Currently NF – Phase A
• Benign environment for PICA
• Leverage MSL integration approach
• 4+m tiled configuration
• Lyocell derived PICA
Courtesy D. Adams, Applied Physical Laboratory
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
St
ag
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o
in
t 
To
ta
l M
ar
gi
n
ed
 H
W
 H
ea
t 
Fl
u
x,
 W
/c
m
2
Stag Pressure, atm
IHF 4-inch Dia. IsoQ
IHF 2-inch Dia. IsoQ
Mini SPRITE
Commet Sample Return
Stardust
MSR-Stagnation
Dragonfly Wedge
Dragonfly
IHF 6-inch Nozzle
IHF 13-inch 
Nozzle 
Dragonfly 
Wedge
Mini-SPRITE
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
St
ag
 P
o
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To
ta
l M
ar
gi
n
ed
 H
W
 H
ea
t 
Fl
u
x,
 W
/c
m
2
Stag Pressure, atm
IHF 4-inch Dia. IsoQ
IHF 2-inch Dia. IsoQ
Mini SPRITE
Commet Sample Return
Stardust
MSR-Stagnation
Dragonfly Wedge
Dragonfly
IHF 6-inch Nozzle
IHF 13-inch 
Nozzle 
Dragonfly 
Wedge
Mini-SPRITE
Entry Systems and Technology Division
Lyocell – A Sustainable Precursor 
• Traditional rayon manufactured from wood pulp involves many 
steps and the conversion of wood pulp into rayon or regenerated 
cellulose results in toxic byproducts
– rayon manufacturing was discontinued and is no longer a viable process in 
the US and Europe 
• Lyocell - solvent spinning technique is simpler and more 
environmentally sound 
– uses a non-toxic solvent chemical that is 99% recycled in the 
manufacturing process 
• Lenzing – sister factories in US, Austria and UK able to provide 
the same Lyocell precursor – multiple supply routes alleviate 
future sustainability concern
10
Refer to below links if interested in information on how fibers are made from wood pulp:
https://www.youtube.com/watch?v=tHdJGFv99fE
https://www.youtube.com/watch?v=14PZNgRoEUM
Entry Systems and Technology Division
11
PICA Manufacturing Overview
Role of Rayon/Lyocell in PICA Manufacturing
• Chopped, graphitized rayon or Lyocell - based carbon fiber slurry-cast into either block 
(billet) or single piece heatshield preforms
• Single piece cast heatshields have fiber oriented to optimize through-thickness thermal 
conductivity
• Lightweight phenolic sol-gel matrix is infiltrated into preform
Rayon or Lyocell Conversion 
to carbon
FiberForm® billet 
preform
Tiled PICA heat shield (> 
1.25m  max diameter)
Single piece PICA 
heatshield (< 1.25m max 
diameter)
Near net shape 
preform
Sustainability 
concern
Entry Systems and Technology Division
Establishment of PICA-D as a Replacement 
for Heritage PICA
• FY17 - SMD-PSD funded NASA Ames to manufacture & perform limited 
property/aerothermal characterization of Lyocell-based PICA (PICA-D)
• Fiber Processing, billet fabrication, single piece heatshield preform fabrication, conversion to 
PICA (billets and single piece preform)
• PICA property testing and arc jet testing
• FY17 task with limited testing indicated PICA-D had the potential to be a 
replacement for heritage PICA
• FY18/FY19+ – further efforts to characterize and extend the capability of 
PICA-D and establish Lyocell PICA as a replacement for heritage PICA
• Establishing PICA-D as a “drop in replacement” will allow missions to depend on and design with 
PICA-D without having to address further sustainability risks.
• Establishing extended capability of PICA-D will allow Sample Return Missions with higher entry 
speed that were not considered before.
• Extended operational capability
• Extended single piece heatshield manufacturing
12
Entry Systems and Technology Division
Lyocell Fiberform/PICA Billet and 
Near Net Shape Cast Processing
13
• 9 Fiberform billets manufactured in FY17 to optimize process (Lyocell )
• Additional billets fabricated in FY18 (property and arc jet testing)
• Fabricated 3 net-shaped Fiberform heatshield blanks (OSIRIS REx scale) in FY17 
• Fabricated 4 net-shaped  ~ 1.5m single piece FiberForm castings (FY18/19)
• Converted one into 1.4 m PICA heatshield: characterization underway
• Limited Non Destructive Evaluation (NDE) on the near net shape Fiberform unit to evaluate fiber alignment
• Significant number of lessons learned captured/implemented and substantial risk 
reduction achieved
OSIRIS Rex 
Scale 0.8m
1.4m heatshield
Extended single piece 
heatshield manufacturing 
demonstrated
Entry Systems and Technology Division
Test Campaign to Establish/Extend Capabilities
14
• Arc jet campaign objectives 
– Compare the thermal response and recession behavior of Lyocell derived PICA to rayon derived PICA 
– Initial look at any performance differences or off-nominal behavior in PICA-D
– Establishing the extended capability of PICA-D will allow Sample Return Missions with higher entry speeds 
not considered before
Entry Systems and Technology Division
PICA-D Arc Jet Testing Quick Look
15
Material Average 
centerline 
recession
(1550W/cm
2 and 1.3 
atm)
Average 
centerline 
recession
(400W/cm2
and 0.3atm)
Average 
centerline 
recession
(220W/cm2
and 0.08atm)
Lyocell 
PICA
4.0mm 6.02mm 3.79mm
Rayon 
PICA
4.2mm 5.97mm 3.89mm
Recession Comparison
Rayon Derived PICA Lyocell Derived PICA
Post test Post test
Pre test Pre test
Pre/Post Test Model Comparison 
(1550W/cm2 condition)
Example in-depth TC Trace @ 1550W/cm2
Lyocell Derived PICA
Rayon Derived PICA
For a Given Test Condition (Same Run Time) Initial Results Indicate that Recession and In-depth Temperature 
Between a Lyocell-Derived PICA and a Heritage Rayon-Derived PICA are Comparable, in Both Oxygen and Nitrogen.
Heat Flux = 260 W/cm2, 
Pressure= 19 kPa 
Runs in Air 2017
Heat Flux = 140 W/cm2, 
Pressure= 14 kPa • Previous testing of PICA with RTV seams was only 
done in air under MSL and Orion programs
• In support of Dragonfly Phase A study, PICA-D 
built 2 wedge shear models with RTV seams for 
testing in a nitrogen environment
Runs in N2 2018/19
Run condition very relevant for proposers considering PICA as a forebody or backshell material
Time from on Centerline (sec)
Te
m
pe
ra
tu
re
 (C
)
Entry Systems and Technology Division
Summary
• PICA has become a workhorse TPS for NASA and sustainment is essential
• Looking for a viable precursor that will be available for decades
• NASA ARC / FMI have been and will continue to work together and 
address any PICA rayon sustainability concerns
• Lyocell Based PICA (PICA-D) was manufactured and limited testing 
performed show it to be a viable replacement for heritage rayon, scaled-up 
single piece heatshield manufacturing also demonstrated
• Exciting future NASA missions need PICA (SRL, MSR EEV and Dragonfly) 
and NASA TPS sustainability effort will have a payoff for these missions
• Establishing the extended capability of PICA-D will allow Sample Return 
Missions with higher entry speeds and larger payload not considered 
before.
16
Entry Systems and Technology Division
Acknowledgement
• PICA sustainability activities are funded by NASA’s Planetary 
Science Division of the Science Mission Directorate
• The authors would also like to acknowledge Y-K Chen, D. 
Ellerby, F. Milos, G. Gonzales, D. Prabhu, and K. Skokova and 
Franklin Taylor.
16


Development of Lyocell Based Phenolic Impregnated Carbon Ablator (PICA-D) for Future NASA Missions

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