The National Aeronautics and Space Administration (NASA) has continued funding Air Squared through 2020 to develop an innovative CryoScroll™ Cryogenic Spinning Scroll Pump (CSSP).
Air Squared is proud to announce the continued development of the world’s first cryogenic spinning scroll pump for liquid methane and oxygen spacecraft fuel systems. The Cryogenic Spinning Scroll Pump (CSSP) is the latest iteration of Air Squared’s CryoScroll™ technology designed to meet the size, weight, and power (SWaP) constraints of liquid methane-fueled spacecraft propulsion. Engineered to be scalable, a single CSSP can operate from 1,000 to 8,000 RPM alone or in series, allowing adaptability over reaction control system (RCS) and main propulsion applications. Reduced SWaP, scalable design, and demonstrating the world’s first cryogenic spinning scroll design, the CSSP showcases Air Squared’s technological sophistication in pioneering aerospace technology.
Pumping cryogenic liquids present a plethora of engineering challenges. The pump must handle two-phase working fluid as both a liquid and a gas. Reducing SWaP requirements are paramount in an industry where it costs over $10,000 for every pound of material sent into space. Equally as important is reliability over long-term space missions where maintenance may be difficult. Alternative solutions like turbopumps are compact and lightweight, but the rapid changes in media density cause the turbine blades to fail, inhibiting their ability to handle two-phase cryogenic fuel. Reciprocating and rotary pumps have less difficulty handling two-phase media, but necessary high-capacity high-load bearings make them prohibitively bulky and oversized for space. Where failure is not an option, simplicity in design is essential and any extraneous componentry reduces the available payload for the rest of the spacecraft.
The CSSP solves these complex techno-economic problems by combining the benefits of both turbo and positive displacement pumps with Air Squared’s innovative spinning CryoScroll™. Fundamentally a positive displacement pump, the CSSP can deliver high pressures with minimal reduction in flow and pump saturated two-phase liquid. By design, the CSSP may be linked in series, multiplying the delivery pressure of cryogenic liquid fuel to the RCS or spacecraft propulsion rockets. Its spinning, co-rotating scrolls eliminate extraneous balancing components and reduce its SWaP footprint. Air Squared is excited to develop the CSSP in support of NASA’s liquid methane propulsion mission and develop the world’s first CryoScroll™ spinning scroll cryogenic pump.
SPINNING SCROLL TECHNOLOGY
In principle, the design of the spinning scroll (also referred to as a “co-rotating scroll”) is very similar to that of the traditional orbiting scroll, as the relative motion between the two scrolls is identical. Pressure and flow are generated the same in both approaches, with the relative motion between the scrolls creating a series of crescent-shaped gas pockets that generate pressure, vacuum, or expansion depending on how the device is being operated.
The primary difference is that the traditional approach of one scroll remaining stationary while the other scroll orbits eccentrically on a fixed path is replaced with two scrolls that rotate in synchronous motion with offset centers of rotation.
The spinning scroll approach reduces componentry, improves efficiency, and allows for higher running speeds. The true rotary motion of the synchronous scrolls eliminates the need for counterweights, allowing for shorter and lighter drive shafts, which, in turn, reduce power consumption, size, and weight. The simplified balancing and a lighter drive configuration also allow for higher obtainable running speeds by a factor of two. As pressure and flow are directly proportional to speed, the spinning scroll design can offer a similar performance with substantial size and weight reduction.
Air Squared is the industry leader in oil-free scroll design and manufacturing. By introducing a simple design with fewer moving parts, scroll technology has established itself as a highly efficient, very reliable, cost-effective alternative. Through a growing line of compressors, vacuum pumps, and expanders, Air Squared makes the many advantages of oil-free scroll technology available to OEMs worldwide.
This material is based upon work supported by a Phase II SBIR award by the National Aeronautics and Space Administration under the topic: Methane In-Space Propulsion (Z10.02). Any opinions, findings, conclusions, or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Aeronautics and Space Administration.