Key Takeaways:

• RMD is a chemical expulsion device and tank for on/off orbit propellant delivery
• Plug & play monolithic RMD reduces lead times without compromising performance
• 3D printed RMD offers vast scalability and design customization

Miniaturization of technology, components, and sub-systems is a reality for nearly all markets and industries; for space, this is critical to reduce launch costs and increase on-orbit efficiency. Laser Powder Bed Fusion (LPBF) is an additive and digital manufacturing technology that has allowed Moog to re-invigorate a heritage product: The Rolling Metal Diaphragm (RMD). The RMD is a storage tank and high-performance expulsion device, primarily for chemical propellants. 

Advanced manufacturing, additive technologies, and Industry 4.0 digital supply chains are evolving and enabling producers to minimize size and mass of launch vehicles and payloads, while simultaneously mitigating historically long lead times. Engineers at Moog are leveraging additive manufacturing and trusted digital logistics solutions to reimagine green propellant combustion engines and other essential components for small satellites (smallsats), vehicles typically 500 kg or less.

When rapid and agile on or off-orbit maneuvers are required in space, chemical propulsion has always been the go-to solution. Chemical propulsion continues to present a product growth opportunity because of the rising demand for green propellant. Without compromising performance, 3D printing RMDs frees up significant working capital by reducing production costs and lead time.

The RMD is 3D printed from lightweight titanium powder into a monolithic component that is both customizable and multifunctional. No additional welding is required to assemble the flexible diaphragm; instead, it is printed integral to the shell of the tank.

Why Titanium? Titanium is compatible with and recommended for a variety of propellants, such as hydrazine, as well as ammonium dinitramide (ADN) and hydroxylammonium nitrate (HAN)-based propellants, which are effective solutions for green propellant-based missions.

To date, Moog engineers have produced and tested two different sized RMDs to explore design scalability. Both are intended to be customizable and distributed throughout any size smallsat vehicle, whether one or more RMD is needed. The additive production process allows RMDs to take on unique shapes, consistent with the vehicle layout to hold the pressurant. An example of some customization, which has been explored thus far, is the addition and relocation of connection ports on the smaller RMD to accommodate additional thrusters and more convenient fill ports.

The larger tank is nearly 10 inches in diameter, with more than a 1 U.S. gallon capacity. After seeing a sneak peek of it, some customers remarked, “This is a game changer. Cannot wait to review the characterization data.”

General dimensions and specifications are described in the table below: 

Operationally, the RMD provides on demand, no-slosh metered fluid expulsion via a small, flight-proven Moog valve, without other transient dynamic response. The flexible, zero permeability diaphragm is controlled by a pressure differential, with nominal pressures up to 375 psi (~28.9 bar). While presently Moog is using 375 psi as a design metric, the pressure capability can be increased by using generative analysis tools to strengthen (not thicken) the structure strategically. Other geometric modifications can be utilized to tune pressure tolerance as desired. 

Moog can supply the RMD either to be filled at the launch site or prefilled with propellant and shipped unpressurized. Commercial ground transportation companies have been licensed to carry the sizes of tanks Moog has developed.

Moog is changing the fundamental aspects of space access by enabling sustainable, cost-effective, high performance products for smallsats (ESPA class, cubesats, picosats etc.). Additive manufacturing allows the company to consolidate multi part assemblies into one monolithic RMD expulsion device while also providing custom sizes and features per-vehicle and/or per-mission needs. The RMD, as well as other products in development at Moog, are intended for a wide array of mission needs at attractive price points with drastically reduced lead times. The high-performance capabilities of the RMD make it particularly desirable for defense and critical communications where spacecraft quiescence and predictable center of gravity control is required. 

¹ Patent Pending

This blog consists of general capabilities information that is not defined as controlled technical data under ITAR Part 120.10 or EAR Part 772.