Mechanical & Fluid Systems

Low Solidity Vaned Diffuser (LSVD) Design for Improvement of Pressure Recovery

Many pump vaned diffuser designs are based on existing airfoil designs, with little attention given to the vane leading edge. There is a need for a vaned diffuser leading edge that helps resist flow separation and the resultant poor diffuser pressure recovery. Diffusers in pumps are often working with an incompressible fluid that makes potential flow methodologies — which have incompressibility as a boundary condition — attractive. The potential flow-based free-streamline analysis methods have been known to improve the aerodynamics of varied components at high incidence angles, such as diffusers, jet engine nacelles, and liquid rocket engine turbopump inducers.

Posted in: Briefs, Mechanical Components, Airframes, Pumps, Aerodynamics

Tangential Wrap Rib Deployable Reflector

The reflector does not use complicated deployment mechanisms.

There is a need for a large deployable reflector of 2-meter diameter or greater so smaller launch vehicles can be used. Common issues with going from a large solid reflector into deployable structures are the structural stiffness and deployable structure complexity.

Posted in: Briefs, Mechanical Components, Antennas, Product development, Storage, Launch vehicles

Development of the Orion Crew-Service Module Umbilical Retention and Release Mechanism

The design is highly modular, and can easily be adapted to other vehicles/modules and alternate commodity sets.

The Orion Crew-Service Module (CM/SM) umbilical retention and release mechanism supports, protects, and disconnects all of the cross-module commodities between the spacecraft's crew and service modules. These commodities include explosive transfer lines, wiring for power and data, and flexible hoses for ground purge and life support systems. Initial development testing of the mechanism's separation interface resulted in binding failures due to connector misalignments. Separation of the umbilical lines between the Crew Module (CM) and the Service Module (SM) happens as part of the vehicle separation activities prior to reentry. If the umbilical fails to separate successfully, the crew and spacecraft will likely be lost.

Posted in: Briefs, Mechanical Components, Mechanics, Architecture, Fasteners, Entry, descent, and landing, Spacecraft

Micro-Lid for Sealing a Sample Reservoir for Micro-Extraction Systems

Improved micro-extraction systems could be useful for military remote sensing using microfluidics.

Great strides are taken to miniaturize spaceflight instrumentation, particularly analytical systems such as liquid chromatographs, gas chromatographs, and mass spectrometers. With miniaturization of instruments, large amounts of samples are no longer required. Therefore, a lesser quantity of sample from the environment needs to be acquired and extracted. Current practices of sample extraction are large in volume and consume an enormous amount of power, which is inconsistent for microfluidic instruments in development. These consume minute amounts of power and are of low mass. There have been efforts to create micro-sample extraction systems; however, a downfall of those systems is the inability to automatically close sample reservoirs.

Posted in: Briefs, Mechanical Components, Mechanics, Containers, Seals and gaskets, Test equipment and instrumentation, Spacecraft

Single-Fluid-Pumped Radiators with Increased Turn-Down Ratio and Control in the Stagnation Regime

The system trades mass-optimized heat rejection for a human-rated, single-fluid pumped system of greater heat rejection range and passive control.

Fluid-pumped radiators are used to reject heat from structures to space. A fluid travels inside the structure to collect heat, and then travels external to the structure through radiators where the heat is rejected to space via radiation heat transfer. A radiator is essentially several tubes attached to a thermally conducting plate or face sheet. The fluid cools as it travels along the inside of the tubes, and then returns to the inside of the structure to repeat the heat rejection cycle. If the structure contains humans, the fluid in the structure must be nontoxic and nonflammable. Further, as space can be extremely cold (4 K), the fluid external to the structure may freeze, particularly during low-power operations where heat rejection needs are minimal. Freezing of the fluid renders the radiator inoperable, and unfreezing a radiator can be very difficult, power-intensive (i.e. heaters), and/or timely. For these reasons, two fluids may be used: one inside that is compatible with humans (e.g. water), and one outside that has a low freezing point (e.g. ammonia). The heat is then transferred from the inner loop to the external loop through a heat exchanger. This dual-loop system is more complex and heavier than a single-loop system. However, as the outer loop does not freeze as easily, the dual-loop radiator system can be operated at lower heat rejection loads, increasing its overall heat rejection range (or turn-down ratio) over that of the single-loop system.

Posted in: Briefs, Mechanical Components, Mechanics, Heat exchangers, Heat transfer, Radiators

Metal Stamping Design Guidelines

Metal Stamping provides an economical way to produce quantities of parts that can possess many qualities, including strength, durability, wear resistance, good conductive properties, and stability. In this paper, we are sharing some ideas that can help you design a part that optimizes all the features that the metal stamping process offers.

Posted in: Briefs, TSP, Aeronautics, Manufacturing & Prototyping, Materials, Mechanical Components, Design processes, Stamping, Metals, Parts

Airfoil-Shaped Fluid Flow Tool for Use in Making Differential Measurements

Researchers at NASA’s Marshall Space Flight Center have developed a suite of adaptable flow measurement devices that can be easily installed without compromising the structural integrity of existing conduits. With their simple installation procedures, the devices can be removed or exchanged without difficulty, allowing for temporary or extended use. The design is in-situ and self-contained, taking measurements from within the conduit, thereby offering more accuracy and allowing for opportunities to modify system operating parameters. Some of the designs can be used to mix the flow or inject a second fluid into the stream.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Measurements, On-board diagnostics, On-board diagnostics (OBD), Hoses

Piezo-Actuated, Fast-Acting Control Valve

The ability of this valve to throttle makes it suitable for regulators and cold gas thrusters.

High-power electric propulsion systems have the potential to revolutionize space propulsion due to their extremely high performance. This can result in significant propellant savings on space vehicles, allowing the overall mass to shrink for launch on a less expensive vehicle, or to allow the space vehicle to carry more payload at the same weight. Many electrical propulsion systems operate in pulse mode, pulsing hundreds or thousands of times per second. Creating reliable valves that can operate in pulse mode for extremely long periods and at low power is critical in these applications. Current solenoid valves have difficulty achieving the life requirements. In addition, a valve with the ability to throttle has the potential to simplify the entire propulsion system by eliminating the need for pressure regulators or latching valves.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Valves, Throttles, Reliability, Electric vehicles, Spacecraft

Interface Between STAR-CCM+ and 42 for Enhanced Fuel Slosh Analysis

Fuel slosh is excited during spacecraft maneuvers. The forces and torques exerted on the spacecraft by the slosh must be controlled by the attitude control system to maintain correct pointing and spacecraft orbit. In some rare cases, the attitude control system may excite the slosh and cause a loss of control of the spacecraft, or the expected spacecraft motion from a certain control command will be different enough from the control command to adversely affect the mission. By linking the computational fluid dynamics (CFD) and the flight simulation software, the fuel slosh can be modeled at high fidelity by the CFD software, while receiving and passing information to and from the flight simulation software, thus increasing the fidelity of both models. In the past, fuel slosh has either been modeled with an equivalent mechanical model, such as a pendulum, or with a standalone CFD simulation.

Posted in: Briefs, Fluid Handling, Mechanical Components, Mechanics, Computational fluid dynamics, Computer simulation, Attitude control, Data exchange, Fuel tanks, Spacecraft

Mechanisms for Achieving Non-Sinusoidal Waveforms on Stirling Engines

The current state-of-the-art Stirling engines use sinusoidal piston and displacer motion to drive the thermodynamic cycle and produce power. Research performed at NASA Glenn has shown that non-sinusoidal waveforms have the potential to increase Stirling engine power density, and could possibly be used to tailor engine performance to the needs of a specific application. However, the state-of-the-art Stirling engine design uses gas springs or planar springs that are very nearly linear, resulting in a system that resonates at a single frequency. This means that imposing non-sinusoidal waveforms, consisting of multiple frequencies, requires large forces from the drive mechanism (either the alternator or the crank shaft). These large forces increase losses, and increase the size and requirements of the control system. This innovation aims to reduce the external forcing requirements by introducing internal mechanical components that provide the forces necessary to achieve the desired waveforms.

Posted in: Briefs, Mechanical Components, Mechanics, Motion Control, Alternators, Crankshafts, Engine efficiency, Stirling engines

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