But this watch-your-weight campaign centers on lightening the dry mass of launch vehicles, such as future, evolved versions of NASA’s Space Launch System—an advanced heavy-lift launch vehicle that will provide an entirely new national capability for human exploration beyond low Earth orbit.
As part of the Game Changing Technology Division within the Office of the Chief Technologist, work is underway on the Composite Cryotank Technologies Demonstration effort. The term “cryotank” refers to storage of super-cold fuels, such as liquid oxygen and liquid hydrogen.
Here’s the weighty dilemma:
Roughly 60 percent of the dry mass of a launch vehicle accounts for the fuel and oxidizer tanks. By using composite materials, a cryotank structure can be produced that weighs 30 percent less than aluminum—the current state-of-the-art.
NASA and its industry partners continuously strive to reduce the weight and cost of launch vehicles. The more weight shaved off a vehicle, the more payload can be carried to space, perhaps even allowing for one less engine or strap-on booster.
The Cure: Out-of-Autoclave
“Our project was one of the original projects within the Office of Chief Technologist,” explains John Vickers, NASA project manager for the Composite Cryotank Technologies Demonstration effort at Marshall Space Flight Center in Huntsville, Ala.
The project centers on fabricating tanks that incorporate design features and new manufacturing processes applicable to designs up to 10 meters in diameter. These tanks could be used on future launch vehicles, in space propellant depots and Earth departure exploration vehicles.
A key to this innovative technological push, Vickers points out, is “out-of-autoclave”—a relatively new technology for composites. Out-of-autoclave curing composite manufacturing is an alternative to the traditional high pressure autoclave curing process commonly used by the aerospace industry.
While it has widespread applications in producing aircraft with the material cured in large autoclaves, using composites for aerospace is a relatively new technology. “The downside of that is that autoclaves are very expensive,” Vickers notes, and they are energy-hungry machines.
“So a benefit for not having to use the autoclave is that many other companies can join into the aerospace industry that, prior to this, could not,” Vickers adds. “Aerospace and lightweight materials…well, they go hand-in-hand.”
Pursuing both technologies in parallel—the composite tank and the cost-saving use of out-of-autoclave technology—exponentially contributes to the achievement of the project,” Vickers says. “It really gives the program two distinct technology advancements that are coming together.”
The project goal is to produce a major advancement in a demonstrated technology readiness; successfully test a 5.5 meter-diameter composite hydrogen fuel tank; achieve a 30 percent weight savings; and 25 percent cost savings, compared to today’s state-of- the-art.
The cryotank work can benefit multiple stakeholders, Vickers observes, be it NASA, industry, and other government agencies.
Vickers says that there are two milestone-making test article structures within his program, a 2.4 meter and the 5.5 meter diameter composite tank. “By the way, that 5.5 meter tank will be the largest composite liquid hydrogen tank that’s been designed, manufactured and tested,” he says.
Last September, NASA picked The Boeing Company of Huntington Beach, Calif., for the Composite Cryotank Technologies Demonstration effort. Under that contract, Boeing will design, manufacture and test the lightweight composite cryogenic propellant tanks.
“The work is going very well,” Vickers explains. “We have a NASA team that’s focused on design and they are working very closely with Boeing.”
“As a NASA engineer, it’s the most fun because it’s the most challenging. We are encountering technical design issues that we’re overcoming. And that’s what engineering is really all about,” Vickers says. “Who is against lighter weight and lower cost? So we’re sitting in a pretty good spot.”