If NASA wants to meet its goal of sending humans to Mars in the 2030s, they’re going to need to construct the proper ride. That’s why the U.S. space agency is currently developing a methane rocket engine that could drive the means for human transportation to the “Red Planet.” Like a number of other corporations and agencies involved in the “new space” industry, NASA has turned to 3D printing to aid in this endeavor, 3D printing a turbopump that will push fuel to the engine of a potential Mars lander. The results of their 3D-printed fuel pump are looking good so far, as NASA has successfully tested the pump to determine that this method for delivering methane fuel may very well be suitable for driving a rocket engine.
This rocket engine fuel pump has hundreds of parts, including a turbine that spins at over 90,000 rpm.
Made up of hundreds of components, the 3D-printed turbopump was designed with 45 percent fewer parts than rocket fuel pumps made by traditional manufacturing methods. To direct fuel into a rocket engine for a Mars landing spacecraft, a series of turbines spin rapidly to drive the pump, which, similar to the way a heart might beat, pulses liquid methane into the engine. Running the system at full power saw the turbines generate 600 horsepower to 36,000 rpm, supplying 600 gallons of methane per minute. At this capacity, the turbopump could fuel an engine capable of creating 22,500 pounds of thrust. In addition to this full-power test, NASA also conducted several other tests at lower power levels.
Selective laser melting was the 3D-printing process used to print the turbopump—a process that builds layers from a metal powder that are then fused together with a laser. Not only did the use of 3D printing allow for a more streamlined pump design, but the technology enabled for a rapid turn around on the manufacturing of two matching turbopumps, one for testing liquid methane fuel and the other for liquid hydrogen.
In 2015, NASA finished testing the other turbopump design for use with liquid hydrogen fuel. For this series of testing, however, the NASA team worked with methane for its ability to store for prolonged periods of time,because liquid methane is cooled to –255 °F (–159°C), as compared to liquid hydrogen, which is cooled to –400 °F (–240°C). In turn, liquid methane boils off more slowly, extending its storage life. Due to the substantial amount of carbon dioxide in the atmosphere of Mars, an added bonus is the fact that it’s possible to create methane fuel from this plentiful gas.
The designer of the turbopump, Marshall engineer Marty Calvert, commented on the use of methane fuel as compared to hydrogen, saying, “By demonstrating the same turbopump can work with different fuels, we’ve shown that a common design would work for either engines fueled by methane or hydrogen. Because liquid methane is much more dense than hydrogen, it requires the turbopump to spin at a different speed to deliver the same amount of mass flow to the engine.”
Aside from the 3D-printed turbopumps, NASA has 3Dprinted injectors and other rocket parts, as well. The next step will see the team combine the 3D-printed turbopump with these components and test the use of methane once again. Mary Beth Koelbl, manager of the Propulsions Systems Department at NASA’s Marshall Space Flight Center in Huntsville, Ala., said of the use of 3D printing for the project, “This is one of the mostcomplex rocket parts NASA has ever tested with liquid methane, a propellant that would work well for fueling Mars landers and other spacecraft. Additive manufacturing, or 3D printing, made it possible to quickly design, build and test two turbopumps with identical designs that worked well with both liquid methane and liquid hydrogen propellant.”
3D printing is the ideal technology for creating advanced space equipment, in that agencies like NASA don’t often need to mass produce parts, but they do need to be able to produce very customized ones. In a case such as the testing of a new design, 3D printing serves to fabricate completely unique parts on demand, ultimately saving NASA time and money to create components. This is in addition to the ability to 3D printing complex parts with new geometries that would have been very difficult to manufacture through traditional processes.