IHI AEROSPACE Co., Ltd. Kenichi HIRAI

2012.6.21

JAXAYuichi ISHIDA, Toshio OGASAWARA, Takuya AOKI, Tetsuya YAMADA, Kazuhisa FUJITA,

Toshiyuki SUZUKI

IR&D Studies of Light Weight Ablator

for Future Reentry Capsule Heatshield

1.Objective of this study

【 Source 】 Laub & Venkatapathy ：” Thermal Protection System Technology Facility Needs for Demanding Future Planetary Missions”, International Workshop on Planetary Probe Atmospheric Entry and Descent Trajectory Analysis and Science, (2003)

HAYABUSA(300MJ/m2,53%)

Mars Viking

Reduction to 1/3 is required

Development of new LWA

Reduction to 1/3 is required

Development of new LWA

MPFMER

Apollo

GenesisStardust

Galileo

Pioneer VenusHAYABUSA

Successfully returned to Earth in June 2010

HAYABUSA-2To be launched in 2014

CFRP is derived from SRM nozzle material

Reliable but heavy!

2

Peak Heat Flux （ MW/m2 ）< 5 5 ～ 10 10 ～ 20 > 20

0.5m

1m

2m

4m

HAYABUSA-22015

CEV2011

Reen

try C

apsu

le

Size

（DIA

）

HTV-R 2017

Small Capsule One-Piece

CFRP

Marco-Polo2018

Large Capsule Tiled LWA

GENESIS2004

STARDUST2006

MSL2013

ASTERM0.3

PICA0.3

PICA0.3

AVCOAT0.5

CFRP1.3

CFRP1.3

LWA0.3 ～

0.4

LWA0.3 ～

0.4Post-HAYABUSA-

2 ?>2015

LWA0.3 ～

0.4

LWA0.3 ～

0.4

The Possible Future DirectionsThe Possible Future Directions 3

2. Our Strategy(1/2) 4

LWA(0.25<ρ<0.4)

LWA(0.25<ρ<0.4)

Carbon Preform （ 0.15<ρ<0.3 ）CBCF (Carbon Bonded Carbon Fiber)

FIBERFORM

CALCARB RVC (Reticulated Vitreous Carbon)

Grafoam

JFOAM

Carbon Preform （ 0.15<ρ<0.3 ）CBCF (Carbon Bonded Carbon Fiber)

FIBERFORM

CALCARB RVC (Reticulated Vitreous Carbon)

Grafoam

JFOAM

x

Resin ImpregnationPhenolic

SC-1008Polyimide

JAXA Original

Resin ImpregnationPhenolic

SC-1008Polyimide

JAXA Original

Development of Domestic

RVCJFOAM

Development of Domestic

RVCJFOAM

1. Issues of Imported preformsExpensiveLong Delivery Time (EL)Sustainability

1. Issues of Imported preformsExpensiveLong Delivery Time (EL)Sustainability

2.Persuit of unique LWAUnique Preforms(RVC)I don’t want to imitate PICA

2.Persuit of unique LWAUnique Preforms(RVC)I don’t want to imitate PICA

3. Preform microstructure Tailoring for successful JAXA PI impregnation

3. Preform microstructure Tailoring for successful JAXA PI impregnation

Imported Preform CBCF RVC

LWA

Resin Impregnation Phenolic Polyimide

Domestic Preform RVC

LWA

Resin Impregnation Polyimide

Arcjet Test

F/B

F/B

3rd Step(12cm×12cm×5cm)

2nd Step(22cm×22cm×5cm)

Same ProcessProcess is good?

Hopefullyimprove

2. Our Strategy(2/2) 5

500μmGrafoam （ ρ=0.16 ） SEM photo

CBCFCarbon Bonded Carbon Fiber

CBCFCarbon Bonded Carbon Fiber

RVCReticulated Vitreous Carbon

RVCReticulated Vitreous Carbon

【 Source 】： Lachaud et al : “Validation of a Volume-Averaged Fiber-Scale Model for the Oxidation of a Carbon-Fiber Preform”, AIAA 42nd Thermophysics Conf 2011 (Extended Abstract).

Carbon Preform（ ρ<0.2

）

Carbon Preform（ ρ<0.2

）

Chop/Milled Fibers Connected by Phenolic Resin

Chop/Milled Fibers Connected by Phenolic Resin

3. Overview (1/3) candidate carbon preforms

6

LWA

Gelation

RT, air

Gellant

Cure

60-80℃

Stir

RT

Resin Impregnation

Resin Solution

vacuum

50-200℃vacuum

RemoveSolvent

After Gelation

s-BPDA / BAFL / DMAcSolution

240℃,air

s-BPDA BAFL

3. Overview (2/3) JAXA Polyimide Resin Impregnation 7

Gelation at RT!Reliable Process!

sufficiently long gel time (several Hrs)

3. Overview (3/3) JAXA Polyimide Raw Material Cost 8

JAXA/PIIn the Past

JAXA/PIIn the Past

JAXA/PIExpected in 2012?

JAXA/PIExpected in 2012?

PhenolicSC-1008

PhenolicSC-1008

Raw Material Cost for □25cm×5cm Panel Fabrication(10,000Yen)

JAXA/PI Price will be

comparative to SC-1008!

JAXA/PI Price will be

comparative to SC-1008!

Bulk Density

[g/cm3]

Imported RVC

(Grafoam FPA-10)0.18

Imported CBCF

(CALCARB 18-2000) 0.19

Domestic RVC

(JFOAM-1, -2, -3)

0.15,

0.21, 0.28

Domestic CBCF NA

Polyimide

Resin

Phenolic

Resin

Imported RVC

(Grafoam FPA-10)NA ○

Imported CBCF

(CALCARB 18-2000) ○ ○

Domestic RVC

(JFOAM-1, -2, -3)○ ○

Domestic CBCF NA NA

Fabrication Matrix of LWA Candidate Carbon Preforms

RVC : Reticulated Vitreous CarbonCBCF : Carbon Bonded Carbon Fiber LWA : Low Weight Ablator

4.Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(1/6)9

CBCF/PreformSize : 22cm×22cm×5cm

Weight : 473.4g

Bulk Density : 0.196g/cm3

CBCF/PI LWASize : 21.98×21.99×4.65cm

Weight : 799.7g

Bulk Density : 0.356g/cm3

4.Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(2/6)10

4.Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(3/6)

0 1 2 3 4 5 6 7 8 9 10 11 12 13-5-4-3-2-1012345

Den

sity

Dis

pers

ion

［％］

1cm cubic

LWA test specimen

0 1 2 3 4 5 6 7 8 9 10 11 12 13-5-4-3-2-1012345

Den

sity

Dis

pers

ion

［％］

1cm cubic

LWA test specimen

CALCARB / polyimide Grafoam / phenolic

1

2 2

3

34

45 5

6

67 7

8

8

9

9

10

1011

1112

12

A1

A2

A1A3

A2B1B2

B3

C1

C2

C3

C3

C2

C1

B3

B2

B1

A3

220

～25

0mm

220 ～ 250mm21-38

48-56

24-28

4210.5-19

10.5-19

21

11

ρ=0.36 ρ=0.28

Data Scatter < ±3% !

Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(4/6)

CALCARB / polyimide Grafoam / phenolic

Residual carbon ratio ［ % ］

within impregnated “resin+solvent”

Res

idua

l car

bon

rati

o ［

％］

Res

idua

l car

bon

rati

o ［

％］

SolventsinRe

sinReCharred

WW

WW

preforminitial

preformfinal

12

65% : Same as genuine PI

35% : lower than genuine Ph

Data Scatter is small, so resin impregnation process is judged

reliable

4.Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(5/6)

220

～25

0mm

220 ～ 250mm21-38

48-56

24-28

4210.5-19

10.5-19

21

0 200 400 600 800 1000 1200 140070

75

80

85

90

95

100

105

Temperature ℃（ ）

W(T

)/W

0×10

0 （％

）

A1 A2 A3 B1 B2 B3 C1 C2 C3

0 200 400 600 800 1000 1200 140070

75

80

85

90

95

100

105

Temperature ℃（ ）

W(T

)/W

0×10

0 （％

） A1 A2 A3 B1 B2 B3 C1 C2 C3

CALCARB / polyimide Grafoam / phenolic

W(T

)/W

0×10

0 ［

％］

W(T

)/W

0×10

0 ［

％］

13

Same behavior as genuine PI

Low BP solvent Is much contained?

0 100 200 300 400 500 6000

0.1

0.2

0.3

0.4

Temperature ℃［ ］

The

rmal

Con

duct

ivit

y ［W

/m/K

］

PICA EstimatedGrafoam / Ph ( ρ 0.28)CALCARB / PI ( ρ 0.36)JFOAM / PI (ρ 0.29)

【 Source 】 Tran et al ：” Phenolic Impregnated Carbon Ablators (PICA) as Thermal Protection Systems for Discovery Missions, NASA TM 110440, (1997)

4.Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(6/6)

14

Good Insulative

Performance!

LWA Thermal Conductivity

4.Validation of Resin Impregnation Process Imported Preform based LWA Fabrication(7/7)15

0 20 40 60 80600

800

1000

1200

1400

1600

1800

2000

2200

Time ［sec］

Tem

para

ture

℃［

］

Measured 2Ap 2Aq 2Ar

ComputedSurfaceTemp

Temperature responses of LWA’s are well predicted by the present tentative

ablation calculation!0 100 200 300 400 500

0

100

200

300

400

500

600

Time ［sec］

Tem

para

ture

℃［

］

Measured 2Ap 2Aq 2Ar

Computed15mm25mm

Depth15mm

Depth25mm

Temperature Response of CALCARB/PI LWA

Repeatability of LWA Temperature responses is

fairly good!

5.Domenstic RVC based LWA Development Development of JFOAM(1/5)

Grafoam CALCARB

JFOAM-1

SEM Photographs of various kinds of lightweight carbon preforms (Our RVC’s are designated as JFOAM-1(density=0.16g/cm3) )

16

Current microstructure of JFOAM is much

coarser than existing imported CBCF/RVC!

5.Domenstic RVC based LWA Development Development of JFOAM(1/5) 17

Similar Properties as Existing Carbon Preforms

5.Domenstic RVC based LWA Development Development of JFOAM(1/5)

JFOAM bulk density vs thermal conductivity

【 Source 】 Tran et al ：” Phenolic Impregnated Carbon Ablators (PICA) as Thermal Protection Systems for Discovery Missions, NASA TM 110440, (1997)

Fiberform （ ρ0.17 ）

Fiberform （ ρ0.14 ）

18

0.11 0.16 0.21 0.28

CW Heat Flux ［ MW/m2 ］

Impact Pressure ［ KPa ］

Heating Time ［ s ］

#1 1.8 4.4 30

#2 3.4 13.7 30

#3 6.0 19.6 30

Test Conditions of Arcjet Experiments

65mm

50m

m

T/C φ0.2mmType-K

Flat FacedSpecimen

BakeliteHolder

LWASpecimen

5.Arcjet Tests of LWA(1/6) 19

JFOAM/PIBefore Test

JFOAM-3/PI After Test: 6MW/m2 x 30s

JFOAM-3/PI After Test: 3.4MW/m2 x 30s

5.Arcjet Tests of LWA(2/6) 20

(a)

CALCARB / PI 6MW/m2x 30sSpallation by

Smaller Particles

JFOAM-1 / PI 6MW/m2x 30sSpallation by

Larger Particles

JAXA/ISASArcjet Tests Photographs

By Degital Camera

5.Arcjet Tests of LWA(3/6) 21

Empirical Expression for Surface Recession Rate of PICA

0.2 0.4 0.6 0.8 1

0.05

0.1

0.15

0.2

0

Rec

essi

on R

ate

(mm

/s)

p0.33exp(-5.93/q0.25)

Arcjet Data AHF271Computed TITAN

X （ p0.33×exp （ -5.93/q0.25 ））

Y（

Rec

essi

on R

ate

）

[mm

/s]

Y=0.2326XP:pressure(KPa)q:heat flux(W/cm2)

Hwang, et al., Race Towards Launch: Qualifying the Mars Science Laboratory Heatshield in under Ten Months, ICCE-17(17th International Conference on Composite/ NANO Engineering, (2009)

5.Arcjet Tests of LWA(4/6)PICA Recession Characteristics

22

5.Arcjet Tests of LWA(5/6)Recession of JFOAM/PI LWA

23

1 2 3 4 5 6 7

0.1

0.2

0.3

0.4

0.5

0Cold Wall Heat Flux （MW/m2）

Rec

essi

on R

ate

（mm

/s）

PICA Estimated

CALCARB / PI ρ（ 0.36） JFOAM / PI ρ（ 0.29）

Grafoam / Ph ρ（ 0.28）

JFOAM / PI ρ（ 0.34） JFOAM / PI ρ（ 0.37）

Our LWA’s surface recession rates are comparative to PICA, when the density values are around 0.36!

5.Arcjet Tests of LWA(6/6)Recession of JFOAM/PI LWA

24

0 1 2 3 4 5 6 70

20

40

60

80

100

120

Cold Wall Heating Rate ［MW/m2］

ρcV

［g/

m2 /s

］

Grafoam / Ph (ρ 0.28)CALCARB / PI ρ（ 0.36）JFOAM / PI (ρ 0.29)JFOAM / PI (ρ 0.34)JFOAM / PI (ρ 0.37)HAYABUSA-CFRP

For the moment, char density values of RVC/LWA’s are somewhat ambiguous, however, recession mass flux values of RVC/LWA

seem to be almost constant. Are they independent of the microstructures?

5. Conclusions & Future Works We are currently conducting IR&D activity towards domestic

RVC/LWA with density 0.3-0.4g/cm3 for future reentry missions. From the experiences of fabricating LWA panels of 22cm x 22cm

x 5cm and density measurements, we have confirmed that our resin-impregnation process for LWA is quite stable and reliable. CALCARB/PI <±3% Grafoam/Ph <±3%

The insulative peformance of current LWA’s is judged acceptable. But the Arcjet tests revealed signs of spallation-driven recession

especially for our domestic RVC/LWA, which may be attributed to the coarse microstructures peculiar to our current RVC’s.

Therefore, further modifications for our RVC are currently underway in order to improve recession resistance.

Fine Cell Structures

25

1mm

Fine Cell Structured JFOAM (ρ0.20)

1mm1mm

Current JFOAM (ρ0.22)

The Possible Future DirectionsFine Cell Structured JFOAM

The Possible Future DirectionsFine Cell Structured JFOAM

26

Fine Cell Structure

Thank You for Your Attention!

Thank You for Your Attention!

Any Questions?Any Questions?