Propulsion

Film Cooled Surface

This cooling technique increases the efficiency of turbine blades.

Turbine film cooling flows typically are subject to jet detachment and reduced cooling effectiveness for high blowing rates. Current concepts to improve jet attachment involve impractical or overly complex hole designs due to manufacturing or durability constraints. Novel film cooling concepts from NASA’s Glenn Research Center involve creating a V-shaped recess on the flow surface of a turbine blade to induce fluid, temperature, or shedding effects; threading turbine film cooling holes with helical channels or grooves (much like the threads of a screw) for the purpose of producing a swirling flow of cooling fluid exiting the film cooling hole; and pairing the threaded holes with holes that have an opposite direction of swirl.

Posted in: Briefs, Aeronautics, Aerospace, Propulsion, Computational fluid dynamics, Cooling, Machining processes, Gas turbines
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NASA’s Pursuit of Power

Advances in batteries and propulsion enable innovations in both terrestrial and deep-space power applications.

Advances in Capacitor Materials

Electrochemical capacitors, or supercapacitors, have gained intense interest as an alternative to traditional energy storage devices. Applications for supercapacitors range from plug-in hybrid electric vehicles (PHEVs) to backup power sources. While the power density of supercapacitors surpasses that of batteries, commercially available batteries have a significantly higher specific energy density.

Posted in: Articles, Aerospace, Power Management, Propulsion, Batteries, Energy storage systems, Ultracapacitors and supercapacitors, Batteries, Energy storage systems, Ultracapacitors and supercapacitors, Nanomaterials, Spacecraft
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Generation-2 Lean Direction Injection System

This technology eliminates the risk of flashback and auto-ignition, and achieves emission and operability goals.

John H. Glenn Research Center, Cleveland, Ohio

An advanced Lean-Direct-Injection (LDI) turbine engine combustor was developed. Named LDI-II, which stands for second-generation LDI, this technology has vastly improved and expanded the performance characteristics of the initial LDI design by not only exceeding NASA’s N+2 emissions goal, but also meeting the operability requirements of full engine power range. The key enabling feature of the technology is the coherence combination of fuel staging and positioning/sizing of swirler-venturi fuel/air mixer elements.

Posted in: Briefs, Propulsion, Exhaust emissions, Fuel injection, Gas turbines
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Testing Aircraft Electric Propulsion Systems on NASA’s Modular Stand

This test stand allows the aviation industry to test a wide range of electric propulsion systems to understand efficiencies and identify needed design improvements.

As powered flight expands to include electric propulsion technologies, aeronautics designers need to understand the electrical, aerodynamic, and structural characteristics of these systems. Therefore, researchers at NASA’s Armstrong Flight Research Center have developed a modular test stand to conduct extensive measurements for efficiency and performance of electric propulsion systems up to 100 kW in scale.

Posted in: Briefs, Propulsion, Electric motors, Engine efficiency, Jet engines, Performance tests, Test facilities
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Iodine-Compatible Hall Effect Thruster

The use of iodine reduces the technical demands on thruster design.

The Hall effect thruster (HET) was designed for long-duration operation with gaseous iodine as the propellant. Iodine is an alternative to the state-of-the-art propellant xenon. Compared to xenon, iodine stores as a solid at much higher density and at a much lower pressure. Because iodine is a halogen, it is reactive with some of the materials with which a Hall thruster is typically constructed. Through research and testing, the new method allows for the HET to be used with iodine propellant for long periods of time.

Posted in: Briefs, Physical Sciences, Propulsion, Propellants, Spacecraft fuel, Storage, Rocket engines
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Burnable-Poison-Operated Reactor Using Gadolinium Loaded Alloy

The problem to be resolved in this work was the use of radial control drums as the sole active reactivity control system for nuclear thermal propulsion, which results in significant rocket performance changes during full-power operation. This can result in large inefficiencies in propellant usage, inaccurate estimations in Isp and thrust, and can be a dangerous operation requiring continuous active control of the reactor given the unstable nature of current nuclear thermal rocket reactor designs.

Posted in: Briefs, Propulsion, Nuclear energy, Alloys, Electro-thermal engines, Engine efficiency
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An On-Demand Gas Generator for CubeSat or Low-Mass Propulsion Systems

This system is applicable to aerospace, automotive, ocean/marine, or limited-resource environments.

NASA’s Jet Propulsion Laboratory, Pasadena, California

There are difficulties related to storing enough gas to propel a CubeSat within an onboard tank. Currently, a CubeSat requiring a large volume of gas for extended propulsion (outside Earth orbit) would need to store liquefied gases that require heavy-bodied tanks that add significant weight to the spacecraft. Safe storage of gases is difficult and not suited well to the CubeSat platform.

Posted in: Briefs, Propulsion, On-board energy sources, Spacecraft fuel, Gases, Fuel tanks, Satellites
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Suppression of Unwanted Noise and Howl in a Test Configuration Where Jet Exhaust is Discharged Into a Duct

This method is permanent to a test facility, and does not need to be changed from test to test.

John H. Glenn Research Center, Cleveland, Ohio

This technology is based on a model-scale experiment simulating a test facility where an engine exhaust is discharged into a duct. Such a configuration sometimes encounters unwanted noise in the form of high-amplitude spectral levels in certain frequency ranges or, in worst cases, a howl that can raise structural concern. The innovation involves placement of a velocity fluctuation damper at the end of the duct. Such a damper is shown to suppress not only the broadband unwanted noise, but also the howl when it occurs. Even though placing the damper on the upstream end of the duct works, the preferred location is the downstream end.

Posted in: Briefs, Propulsion, Noise, Noise, Exhaust pipes, Jet engines
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Reynolds-Averaged Navier-Stokes Integration for Shock Noise (RISN)

Reynolds-averaged Navier-Stokes (RANS) Integration for Shock- Noise (RISN) is a computer program that evaluates acoustic analogies to predict jet noise. Jet noise is due to turbulence from the chaotic flow within the exhaust of a rocket or air-breathing jet engine. The source of jet noise is the turbulent mixing of the exhaust, screech (tones) due to a feedback loop between the semi-periodic shock cells and the nozzle, and broadband shockassociated noise due to the interaction of the turbulence with the shock cells. Acoustic analogies are rearrangements of the Navier-Stokes equations into a left-hand-side propagation operator and a right-hand-side equivalent noise source. RISN is capable of predicting the noise spectrum from all source components within supersonic offdesign jets. Furthermore, the noise from three-dimensional and axisymmetric nozzles can be predicted as long as a steady RANS solution is present. RISN predictions are based upon integrations of computational fluid dynamic solutions. Predictions consist of the spectral density at observers positioned around the nozzle exit.

Posted in: Briefs, Aerospace, Propulsion, Computational fluid dynamics, Computer software / hardware, Computer software and hardware, Computer software / hardware, Computer software and hardware, Noise, Noise, Jet engines
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Regeneratively Cooled Porous Media Jacket

Cooling jackets were developed comprising impermeable inner and outer walls.

A non-toxic nitrous oxide fuel blend (NOFB) monopropellant with a high adiabatic flame temperature reaching and probably exceeding 3,450 K and a very high thermal decomposition limit (>390 °C) is under development. To design an optimal rocket engine that can handle the high adiabatic temperature during continuous rocket thruster operations, a regeneratively cooled rocket engine is desirable, but the regenerative jacket temperatures must remain well below the monopropellant’s thermal decomposition limit. In fact, the entire engine during operation should ideally remain well below the thermal ignition limit so that heat soak-back cannot potentially decompose the monopropellant following an engine restart.

Posted in: Briefs, Aerospace, Propulsion, Cooling, Rocket engines
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