Alu-Ti Welding demonstration and Pre-Qualification

 
For spacecraft missions,  new requirements such as demisability will preclude the use of titanium for propellant tanks some LEO missions. If Aluminium propellant tanks are successfully introduced in space propulsion systems, it will be necessary to interface such tanks with the tubing and pipework surrounding the tank.  As such pipework will still be made from titanium alloys, usually Ti-6Al-4V or Ti3Al2.5V, an Al-Ti joint will be required.

Objective(s)
To identify suitable joining technologies which can be developed so that Al-Ti transition joints can be successfully manufactured.  To develop the joining technology to develop a tube-to-tube and port-to-tube joint.

Achievements and status
Two joining techniques were selected for study; Rotary Friction Welding (RFW) and Magnetic Pulse Welding (MPW).  The RFW technique has been successfully developed such that Al-Ti transition joints in size ¼ and ½ inch can be routinely produced.  These joints have gone through a full qualification test programme and are now available for commercialization.  The MPW process has proven to be more problematic.  In order to produce a fully welded joint, it has been necessary to model the process and develop the technology.  This process is still on-going (see next steps).

Benefits
If demisable aluminium tanks are to be introduced, then it will be necessary to interface the tanks to titanium tubing.  The successful development of the Al-Ti tube-to-tube joint using RPW makes this a real possibility.

Next steps
VEGA has announced that for the AVUM, an aluminium tank is being developed.  Therefore the VEGA project team is working closely with Omnidea-RTG to adopt the RFW technology and produce a new 3/8 inch joint.  This will be performed as a CCN to the existing contract which ended in May 2016.