Aerospace

Features

• Narrow fusion zone
• Deep penetration
• Accurately controlled weld characteristics
• Low distortion
• Minimum heat effected zone
• Near parent metal strength
• Ability to weld many combinations of difficult or dissimilar metals
• No surface oxidation
• Reproducible quality welds

Electron Beam welding has been successfully used as one of the fabrication techniques on a gas chromatograph mass spectrometer (GCMS) on the Huygens probe on board the current Cassini Mission to Saturn.

Saturn and its mysterious moon, Titan, are the primary destination of the Cassini Mission, a project under the joint development of NASA, the European Space Agency and the Italian Space Agency. Launched from Cape Canaveral, Florida in October 1997 aboard a Titan IV/Centaur rocket, Cassini will execute two gravity-assisted flybys of Venus, then Earth and Jupiter. Cassini’s velocity will increase as it swings around each planet, allowing it to reach its final destination by July 2004.

Upon arrival, an onboard rocket engine will fire to retard the spacecraft into the first of some 60 orbits of the planet. In late 2004, the orbiter will adjust its trajectory and release the Huygens probe for its three-week journey to Titan. After atmospheric entry and parachute deployment, the Huygens probe will slowly descend to the surface of Titan. The instrument-laden probe will then relay important measurements to the Cassini orbiter where they will be stored for eventual transmission to Earth.

Process

The GCMS analyser has very precise design and fabrication parameters that led engineers at NASA Goddard in the US to choose electron beam welding technology to make the necessary welds. Approximately 24 welds were made using a Wentgate Dynaweld welder made by Cambridge Vacuum Engineering to ensure high-integrity, leak proof joints in key components of the GCMS.

Cambridge Vacuum Engineering’s American arm, Wentgate Dynaweld, won the contract to supply a 60kV, 4kW electron beam welding unit, complete with PLC/CNC control of the machine and its associated complex tooling.

The welder was installed and commissioned early in 1998 by the company’s service team.

After successfully using a subcontract electron beam welding facility for use on the Huygens GCMS, NASA decided to invest in their own in-house capability for the welding of key components destined to be part of future space exploration missions.