Braze alloys for space

Growing rapidly, the space industry is predicted to be worth $1.1 trillion by 2040, up from $384 million in 2017, according to Morgan Stanley. Between space exploration, satellite communications, and the possibility of space tourism, more applications demand the ability to enter orbit or beyond.

However, the massive costs involved in vehicle launches could slow that growth. The complexity of space travel leads to exorbitant costs. NASA estimates that the average space shuttle launch cost $450 million per mission. Endeavour, the last orbiter in NASA’s space shuttle program, cost $1.7 billion and was overhauled several times between its 1992 inaugural mission and its 2011 retirement. In addition, more manned flights make safety a huge concern for exploration and tourism, demanding careful engineering and proven systems.

Brazing, a long-standing technique to join two metals by heating and melting a filler alloy that bonds to the two pieces, can play a role in improving safety and costs.

Reducing precious metals

Gold, palladium, and other precious metals – the brazing materials that put men on the moon and supported much of the early space exploration work– are becoming increasingly scarce, driving up commodity prices. Engineers are often reluctant to move away from years of research and development data that shows the alloys are tested and reliable.

Non-precious metal alloys made from nickel, chromium, and cobalt are already successful in aviation applications, and researchers are working to make them fit for orbit and beyond.

Two of Morgan Advanced Materials’ braze alloys, RI-46 and RI-49, were engineered and used by NASA on the space shuttle main engine, known as the RS25. Morgan engineers developed RI-46 to replace the older gold/nickel Nioro braze alloy. Reducing the amount of gold and replacing it with copper and manganese made the braze alloy significantly less dense and provided crucial weight savings while maintaining -240°C to 700°C (-400°F to 1,292°F) temperature performance. NASA plans to continue using the alloys on its Space Launch System (SLS), a vehicle planned to take a crewed mission to Mars.

Sensor mounting

Brazed alloys in space equipment allow sensors to be mounted as close as possible to engines to measure and monitor output and feed data back to operators. Mission control and crew can then accurately read and measure data and output on fuel efficiency, temperature, gas flow, and monitor for fire detection or abnormalities. If these sensors are placed too far away from the engines, data readings become inaccurate, potentially compromising missions.

In late 2018, a two-man space crew had to abort their flight to the International Space Station (ISS) after a post-rocket launch failure. The Soyuz spacecraft started to fail 119 seconds into the flight, with problems reported by the crew first, not by mission control. The crew described feelings of weightlessness, an indication of a problem during that stage of the flight. They aborted, ejected their capsule from the rocket, and returned safely to Earth.

While the cause of failure is still to be identified, such a situation should not happen. Any problems should be picked up by mission control, and not be reliant on crew judgement.

The challenge is that some sensors are made from ceramic, due to the need to resist corrosion and high temperatures, typically up to 950°C (1,742°F). These ceramic sensors then need to be joined to metallic parts of the engine, requiring different braze alloys.

Active alloys can join metal to ceramic or ceramic to ceramic.

Morgan engineered Incusil-ABA and Ticusil about 40 years ago for such applications, which are still in use today. New alloys in development should withstand much higher temperatures.

Morgan Advanced Materials plc