Industrial Gases Support Space Activity
July 26, 2023
When NASA's deep space rocket, the Space Launch System (SLS), took off on its first flight as part of the Artemis I it did so using several hundred thousand gallons of liquid oxygen and liquid hydrogen as propellants. These gases thereby launched what will be a series of complex missions to build, as NASA puts it, “a long-term human presence at the Moon for decades to come.
Such strong resolve to return to the moon and onward to Mars, along with increasing satellite deployment, the pursuit of privatized space stations and the emergence of space tourism, means commercial opportunities in space are themselves, rocketing. While launches tend to steal the headlines, industrial gases are involved in various stages before, during and after lift-off. When every stage is mission critical, quality and reliability are key. These are four areas where industrial gases are vital:
Stage 1: Manufacturing spacecraft components
Today, more and more of the rocket engines that ascend layer by layer through the Earth’s atmosphere are themselves built layer by layer. Industrial gases and specialized alloy metal powders are used in the 3-D printing of engine components like turbopumps and combustion chambers. Additive manufacturing has become the preferred method for engine parts where low weight, high strength and complex geometries are required. When you’re sending something into space, every gram matters.
With light weight in mind, aerospace companies also often use carbon-fiber composites in their spacecraft structures. The “lay-up” or molding process for these parts involves the composite material being cured in an autoclave. These large vessels are pressurized with nitrogen – just one of the many gases critical manufacturing steps.
Stage 2: Component integrity testing
The components have been manufactured – now it’s time to test their integrity. That means simulating space here on Earth. Components, sub-systems or even full satellites or spacecraft are subjected to their future in situ conditions in so-called space simulation chambers or thermal vacuum chambers for many hours on end. The entire James Webb Space Telescope, for example, was put in a vacuum chamber to be tested for the rigors of space. At this stage, industrial gases are crucial for simulating the extreme parameter changes that the spacecraft may encounter. Cryogens like liquid nitrogen and liquid helium are used to cool the chambers and create a vacuum.
Stage 3: Engine testing and launch fuels
When it comes to sending a rocket skyward, the heavy lifting is done by industrial gases. In a typical launch, around 90% of the rocket’s mass at take-off is the propellants. Liquid oxygen and liquid hydrogen are the two signature gases of most modern space programs. There is also engine testing before the launch which requires even more of these two gases The engines are tested on the ground in test stands and tested again when they are on the spacecraft. They will burn for the full duration as if in an actual launch – usually around eight or nine minutes.
The number one factor on the supply of gases for launch and testing is not necessarily cost: it’s reliability. Launch companies will need truckloads of gases – several waves of deliveries over a few days. And then there might be a last-minute change to the mission timeline – so flexibility is critical too.
Stage 4: In-space propulsion
With the spacecraft and its payload successfully reaching space, the mission continues. Certain payloads – a satellite for example – begins orbiting the Earth. To reach and maintain their desired orbits, satellites also use propulsion. This is typically high efficiency electric propulsion that relies on rare gases like xenon and krypton.
In ion-drives (or ion-thrusters), heavy ions of these rare gases are accelerated to create just enough propulsion to move satellites in a void. The drives are solar-powered and are so efficient that 10 kg of xenon gas can see a small satellite through its multi-year lifecycle. These rare gases are not highly abundant in our atmosphere so specialized separation work is required to get a meaningful quantity of the gases from the air.
The next frontier
The steep increase of space activity in recent years means an increased frequency of launches. Trends like “in-space manufacturing” are already emerging, where specialized materials and products are produced in the unique environment of space for use on Earth. In-situ resource utilization like mining the Moon or asteroids is another exciting endeavor that will emerge in the coming years.