View of the manufacturing setup. Source: Cranfield University

Titanium in space: researchers develop manned vessel prototype

An additive manufacturing process pioneered by engineers at Cranfield University in the UK has led to the production of the first full-scale prototype of a titanium pressure vessel for use in manned spaceflight.
^ View of the manufacturing setup. Source: Cranfield University

Selected by Daniel Sweet

A team comprised of engineers and researchers from Thales Alenia Space, Cranfield Univeristy, and Glenalmond Technologies designed the 8.5 kg vessel, which is made of the titanium alloy Ti-6Al-4V and is approximately 1m in height. It was created using the Wire + Arc Additive Manufacturing (WAAM) procedure, which Cranfield University has developed over the last decade.

This streamlined machining process converts a digital drawing directly into a finished structure, eliminating the need for long-lead-time forgings and substantially reducing the amount of waste material produced by other forms of manufacturing.

Indeed, if manufactured traditionally, the component would have required about 30 times more raw material than its final mass.

By using the WAAM process, more than 200 kg of Ti-6Al-4V was saved per prototype.

Massimo Chiampi, Study Manager for Additive Manufacturing projects at Thales Alenia Space, explained how the WAAM process came to fruition: “We were looking for an innovative manufacturing solution for the tanks, which typically suffer from long lead time with the conventional production route based on subtractive machining. Thanks to this project, we have demonstrated that the adoption of WAAM technology enhances the competitiveness of our product.

A near-net-shape item is fabricated in few days - compared to several months needed for the procurement of the standard wrought products - and also the amount of machining operation is consistently reduced.

We have achieved a 65% reduction on the overall lead time without giving up the requested performances and this provides a benefit also in terms of design flexibility, making it possible to answer customer needs at a late stage of the project.”

After being manufactured at Cranfield, the titanium vessel was sent to Glenalmond Technologies where it was stress-relieved, laserscanned, machined, and inspected using ultrasonic techniques. The final inspection was performed by Agiometrix using an optical scanner and computer tomography (CT-scan) for internal quality analysis. Thales Alenia Space then ensured that the part met mechanical requirements and specifications.

Satisfied that the vessel fulfilled the technical and quality driving requirements, the team is now proceeding to the building of a second prototype. This will allow them to fine tune the whole manufacturing cycle, demonstrate the repeatability and reliability of the process, and push the implementation of the new approach into flight hardware.

“We have been developing WAAM technology for more than 10 years,” reflected Dr. Jialuo Ding, principal research fellow at Cranfield University, “and it is very satisfying to see it reach this level of commercial maturity.”

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