Infinite Composites: Type V tanks for space, hydrogen, automotive and more

Infinite Composites has developed technology for the metallic boss-CFRP tank interface that mitigates thermal expansion mismatch and ensures attachment on a nanoscale level for 20 years of service. Photo Credit: Infinite Composites

Another key part of such a pressure vessel is the metallic boss interface which is attached to the composite structure for connecting to external valves and fueling systems. The boss receives end loading during transportation, as well as large temperature swings during pressurization cycles, and its bond with the composite structure is critical. Infinite Composites uses a proprietary process for metallic bosses bonded to the composite laminate that mitigates the mismatch in thermal expansion between the dissimilar materials. This enables intimate bonding on a nanoscale level which can remain intact even after 20 years of daily use.

These pressure vessels have also passed numerous tests, including burst pressure up to 993 bar, 816°C bonfire testing, cryogenic testing to -207°C, pneumatic testing to simulate 200 launches and landings of an orbital class rocket and pressure/temperature cycling simulating 20 years of service. “We’ve also done filling tests with cryogens like liquid oxygen and liquid helium,” says Villarreal. “Our tank construction has proven its performance throughout. We have made tanks all the way down to 2.5 inches in diameter for NASA Langley and 325-liter tanks that measure roughly 2 feet in diameter by 5 feet long.”

Wet filament winding vs. towpreg, 3D printing

Infinite Composites uses the most common process for making pressure vessels — filament winding using liquid resin —versus winding of towpreg or prepreg tapes. “We have used towpreg, but we prefer the flexibility of being able to use whatever customized resin we want and not be restricted to one matrix system in a prepreg, because that’s not optimal for developing new fluid compatibilities,” explains Villarreal. “We prefer the flexibility in the materials that wet winding gives.”

He adds that the automated tape winding or fiber placement (AFP) equipment required to layup prepreg is also very expensive. “The process is also more complicated and not as scalable as wet filament winding using multi-spindle machines,” says Villarreal. “However, we’re working on a project with Dr. Ranji Vaidyanathan at Oklahoma State University right now for manufacturing in space, and that type of application may require towpreg because mixing liquid resins in space doesn’t seem practical.”

“What I think has a lot of promise is continuous fiber 3D printing,” he continues. “I think that will be the most advantageous kind of manufacturing technology going forward because you could print the mandrel where it functions as part of the carbon fiber structure. And you could easily do this in a fully automated way in a space environment. You also can get some very interesting structures with internal features that you can't really get with any other type of manufacturing process right now. So that's my pick for the future of manufacturing composites including composite pressure vessels.”

Growth in New Space

Infinite Composites Type V tanks burst tested for 700-bar hydrogen storage (left) and nitrous oxide (NOX) and helium gas raceway for a space vehicle fuel system (right). Photo Credit: Infinite Composites

The New Space market is exploding, says Villarreal, extending beyond the traditional cryofuel and oxidizer tanks for rockets and launch vehicles to propellant tanks for satellites and lunar landers, as well as pressurized tanks for space fueling depots, space stations and habitats. “These applications have to go to Type V tanks because they are so mass-sensitive. It’s a direct trade-off — every pound in a launch vehicle is a pound of paying cargo left on the ground. They can be giving up millions of dollars by having multiple, heavier tanks.” The same calculus applies to satellites and lunar landers.

Infinite Composites is supplying tanks for multiple LEO and GEO satellites as well as a lunar lander, all of which should be in space by 2024. “Our tanks are used in the propulsion systems, which typically use gases like xenon or krypton,” says Villarreal.

“But we're increasingly getting more customers wanting larger and larger tanks,” says Villarreal. “We've had interest from groups that want all-composite tanks with more than a 36-foot-diameter for their launch vehicles. We can't make tanks that large yet, but the interest is out there. I think that's where the market is going. And space continues to be the biggest growth sector for us, although hydrogen applications are picking up as well.”

Hydrogen, converging solutions

Infinite Composites is doing work with multiple players in the hydrogen-powered aircraft space, delivering 10 Type V composite tanks for testing. “We’re also working with a group called Skydweller [Oklahoma City, Okla., U.S.] that is building UAVs for ultralong flights,” says Villarreal. “We’re replacing some of their battery capacity with hydrogen tanks, and doing some great studies with them, looking at 350-bar compressed gas tanks as well as a joint proposal to develop liquid hydrogen tanks for UAVs.”

Infinite Composites has tested and is continuing to explore non-cylindrical tank shapes. Photo Credit: Infinite Composites

Will these liquid hydrogen  tanks be like those already used in space launch vehicles, or more like the all-metal dewars being developed for hydrogen-powered heavy trucks? “We’ve done some testing with vacuum-insulated dewars,” says Villarreal. “I think one of the challenges for these is that the metal structures in the tank are just transferring heat. In our testing with liquid helium for a liquid hydrogen project, all the lines were stainless steel and if there was even a tiny break in the insulation — or any spot that was less insulated — then the liquid helium would just boil off. I think all-composite tanks are going to be the big winner because you can avoid most of that heat transfer through the tanks, especially if we do go to vacuum-insulated tanks for such applications.”

Villarreal also notes that currently, Type V tanks used for transportation on Earth experience far more pressure cycles (tens of thousands) compared to space vehicle tanks (tens to hundreds). That may change with increased use of reusable launch vehicles and the vision for refueling stations in space to extend mission duration for space tugs and other spacecraft. “But the major difference is the risk of damage from external sources,” he says. Tanks for spacecraft are manufactured to be extremely lightweight and able to withstand launch, but not necessarily impact-resistant for everyday service in a ground or airborne terrestrial vehicle. “That drives significantly more rigorous testing to mitigate,” Villarreal adds. As described above, Infinite Composites has done this type of testing thanks to its origin in NGVs and in its more recent hydrogen tank developments — and sees technologies coming together.

“We’re at the intersection of all these markets — hydrogen for more sustainable aviation and global transportation, industrial applications for gas storage and transport and New Space — and we see the technology for these applications converging. We're even selling some of the same tanks to hydrogen aircraft programs that we would to space vehicle groups because they meet all the same standards and safety factors and went through the same testing. I don't think there will be a big difference in the technologies that are being used in these markets within five years or so.”

“The Type V tanks that we produce already exceed the DOE targets for gravimetric efficiency for hydrogen storage in vehicles, and they’re exceeding the targets previously set for space applications,” says Villarreal. “They're lighter than anything else on the market. I see that coming together and providing the solution for energy storage for propulsion in the future.”