Feasibility of using Earth-Bounded NDT Techniques for the Space Environment MIT V. Nikou, P.F. Mendez, K. Masubuchi & T.W. Eagar Massachusetts Institute of Technology, Cambridge, USA Explain the presentati on is about NDT of welds done in space

MIT February 1 st, 2003 Inspecting things in space is difficult Space Shuttle Columbia The Need for Non Destructive Testing in Space General NDT in space: NASA 1980? NDT of welding in space: this work  Welding in space is at an advanced stage:  Russians did it in space  Japanese and Americans did it on planes  NASA has a prototype design  Weld requirements: especially strict in space  Space structures: sufficient life to make economic sense  NDT in space only considered for monitoring

Summary MIT 1)Space Environment 2)Review of available NDT methods 3)Evaluation of NDT methods 4)Recommendations What is this?

MIT The Space Environment 1.Zero Gravity: Low Gravity condition (g/g 0 =10 -5 to ) Physics change (density, convection, surface tension) 2.Space Vacuum: Mean Km in the order of Atm Thickness of residual atmosphere is very small Local pressure gradients instantaneously equalized 3.Space Radiation: Vacuum Ultraviolet radiation (VUV) Wide temperature variations on structures (–110 0 C to C) 4.Composition of space environment: Atomic Oxygen (very corrosive) Atomic Hydrogen Space Debris Meteoroids What is this?

NDT Methods Reviewed MIT 1.Visual (easy, less accurate) 2.Radiographic (very sensitive, portable, radiation hazard) 3.Ultrasonic (space-graded compounds needed as couplants) 4.Magnetic (surface defects, dry method OK) 5.Penetrant (can operate only up to Atm) 6.Electrical-Eddy Current (surface and shallow crack detection) 7.Acoustic Emission (has to be detected in real time, better for monitoring)

NDT Methods Reviewed MIT 1.Visual 2.Radiographic 3.Ultrasonic 4.Magnetic 5.Penetrant 6.Electrical (Eddy Current) 7.Acoustic Emission 1.Radiographic 2.Magnetic 3.Ultrasonic 4.Eddy Current Use a consistent order for sorting them.

MIT NDT (Welding - Monitoring) Flaw detection Weld geometry Materials Safety Versatility NDT Techniques Performance Factors Flaw Detection:  Minimum detectable flaw size  Maximum detectable flaw depth Materials:  Al  Ti  Metal Matrix Composites (MMC)  Austenitic Stainless Steel  Martensitic Stainless Steel Geometry of welds:  Brazing (B)  Electron Beam Welding (EBW)  Laser Beam Welding (LBW)  Arc Welding (AW)  Resistance Welding (RW)

NDT Methods Evaluation Eddy Current: most suitable Why? Ultrasonic: maybe for MMC Why? Radiographic: heavy Magnetic: less suitable Why? MIT Explain why in little bullets

Conclusions  No welding in space without NDT of welds  Review of NDT methods for welds made in space  Earth-bounded NDT processes could be used in space  Eddy-Current most all-around suitable technique  Ultrasonic suitable for MMC  Future work involves examining the defect generation of specific welding methods