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X-33 LH2 Tank Failure Investigation Findings

Presented byMindy Niedermeyer

MSFC

Aerospace Materials, Processes, and Environmental Technology Conference

September 18 - 20, 2000

https://ntrs.nasa.gov/search.jsp?R=20010067274 2020-06-20T09:29:14+00:00Z

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X-33 LH2 Tank Failure Investigation Findings

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X-33 LH2 Tank Failure Investigation Findings

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X-33 LH2 Tank Failure Investigation Findings

• Tank History and Test Objectives• Failure Description• Investigation• Conclusions

Introduction

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X-33 LH2 Tank Failure Investigation Findings

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X-33 LH2 Tank Failure Investigation Findings

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X-33 LH2 Tank Failure Investigation Findings

Tank Description

• Structural component of the aft body

• Quad-lobe design

• Sandwich - honeycomb graphite epoxy construction

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Outer Face Sheet -0.034 in. thick (7 plies)

Inner Face Sheet - 0.066 in. thick (13 plies)

[65/0/-65/90/-65/0/65]T

[45/903/-45/03/-45/903/45]T

Geometry of sandwich structure

Core (1.5 in.)

X-33 LH2 Tank Failure Investigation Findings

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X-33 LH2 Tank Failure Investigation Findings

Test Objectives

• Verify structural integrity at 105% expected flight load limit varying the following parameters

• Cryogenic temperature

• Internal pressure

• Mechanical loading

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X-33 LH2 Tank Failure Investigation Findings

• September 21, 1999 test aborted due to hydrogen leaks

• 100% cryogen fill (LH2)• 20 psig internal pressure

• November 3, 1999 test completed • 100% cryogen fill (LH2) at 42 psig internal pressure• Load case 5 applied at 5 psig internal pressure• Tank drained of cryogen

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X-33 LH2 Tank Failure Investigation Findings

Timeline

• Tank filled,12:30 PM

• Tank pressurized to 42 psig, 2:00 PM

• Tank vented to 2 psig, 3:00 PM

• Loads applied, pressure increased to 5 psig, 4:40 PM

• Tank drained, 6:00 PM

• Lobe 1 failure, 6:24 PM

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X-33 LH2 Tank Failure Investigation Findings

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X-33 LH2 Tank Failure Investigation Findings

Initial Findings

• Peel Failure• Outer skin and core peeled away from inner skin

• Core Failure• Core is ‘mangled’

• Hydraulic fluid on test article• Foreign Object Debris (FOD)• Poor bondlines• Pressure in core above ambient 13 hours after failure

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X-33 LH2 Tank Failure Investigation Findings

Subsequent Findings

•• Core pressures behaved unexpectedlyCore pressures behaved unexpectedly

•• MicrocrackingMicrocracking

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Mean Core Pressure vs TimeAll Lobes

-20

0

20

40

60

80

100

120

140

11:00 13:00 15:00 17:00 19:00 21:00 23:00

Time

PL11 PL12 PL13 PL21 PL22 PL23 PL31 PL32 PL33 PL41 PL42 PL43 PL44 PL45 PL46 PL47 PL48 PL49 Tank Pressure

Core Pressure vs Time

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X-33 LH2 Tank Failure Investigation Findings

Conclusions

•• The inner skin microcracked and hydrogen infiltratedThe inner skin microcracked and hydrogen infiltrated•• The cracks grew larger under pressureThe cracks grew larger under pressure•• When pressure was removed cracks closed slightlyWhen pressure was removed cracks closed slightly•• When tank was drained and warmed, cracks closed and When tank was drained and warmed, cracks closed and blocked leak pathblocked leak path

•• FOD and debond areas provided an opportunity for a FOD and debond areas provided an opportunity for a leak pathleak path

•• There is still hydrogen in the other 3 lobes todayThere is still hydrogen in the other 3 lobes today