Propulsion

About: Propulsion is a research topic. Over the lifetime, 24977 publications have been published within this topic receiving 200311 citations.

Design of Long-Endurance Unmanned Airplanes Incorporating Solar and Fuel Cell Propulsion

Abstract: Preliminary performance analysis and conceptual design are described for a class of unmanned airplanes possessing multi-day endurance capability. A mixed-mode electric power system incorporates solar cells for daytime energy production and a non-regenerative H2-O2 fuel cell to supply energy for night flight. The power system provides energy for all onboard systems, including propulsion, payload, and avionics. Excess solar energy is available during significant portions of the day, and may be used for climbing, maneuvering, or payload functions. By jettisoning fuel cell reactant product (water) during flight, vehicle endurance may be increased under certain conditions. Empirical structure sizing algorithms are combined with low-Reynolds number aerodynamics algorithms to estimate airplane size and geometry to meet prescribed mission requirements. Initial calculations for summertime, high-altitude flight (above 40,000 ft (12 km)) at moderate latitude (31 degrees N) indicate that mission endurance of several days may be possible for configurations having wing loadings on the order of 0.9 to 1.3 lb/ft squared. These aircraft tend to be somewhat smaller than solar-powered aircraft previously conceived for multi-month endurance utilizing regenerative fuel cell systems for night flight.

Mixed Phase Modeling in GlennICE with Application to Engine Icing

Abstract: A capability for modeling ice crystals and mixed phase icing has been added to GlennICE. Modifications have been made to the particle trajectory algorithm and energy balance to model this behavior. This capability has been added as part of a larger effort to model ice crystal ingestion in aircraft engines. Comparisons have been made to four mixed phase ice accretions performed in the Cox icing tunnel in order to calibrate an ice erosion model. A sample ice ingestion case was performed using the Energy Efficient Engine (E3) model in order to illustrate current capabilities. Engine performance characteristics were supplied using the Numerical Propulsion System Simulation (NPSS) model for this test case.

Nuclear Thermal Propulsion (NTP): A proven growth technology for human NEO/Mars exploration missions

Abstract: The nuclear thermal rocket (NTR) represents the next “evolutionary step” in high performance rocket propulsion. Unlike conventional chemical rockets that produce their energy through combustion, the NTR derives its energy from fission of Uranium-235 atoms contained within fuel elements that comprise the engine's reactor core. Using an “expander” cycle for turbopump drive power, hydrogen propellant is raised to a high pressure and pumped through coolant channels in the fuel elements where it is superheated then expanded out a supersonic nozzle to generate high thrust. By using hydrogen for both the reactor coolant and propellant, the NTR can achieve specific impulse (I sp ) values of ∼900 seconds (s) or more — twice that of today's best chemical rockets. From 1955–1972, twenty rocket reactors were designed, built and ground tested in the Rover and NERVA (Nuclear Engine for Rocket Vehicle Applications) programs. These programs demonstrated: (1) high temperature carbide-based nuclear fuels; (2) a wide range of thrust levels; (3) sustained engine operation; (4) accumulated lifetime at full power; and (5) restart capability — all the requirements needed for a human Mars mission. Ceramic metal “cermet” fuel was pursued as well, as a backup option. The NTR also has significant “evolution and growth” capability. Configured as a “bimodal” system, it can generate its own electrical power to support spacecraft operational needs. Adding an oxygen “afterburner” nozzle introduces a variable thrust and I sp capability and allows bipropellant operation. In NASA's recent Mars Design Reference Architecture (DRA) 5.0 study, the NTR was selected as the preferred propulsion option because of its proven technology, higher performance, lower launch mass, versatile vehicle design, simple assembly, and growth potential. In contrast to other advanced propulsion options, no large technology scale-ups are required for NTP either. In fact, the smallest engine tested during the Rover program — the 25,000 lb f (25 klb f ) “Pewee” engine is sufficient when used in a clustered engine arrangement. The “Copernicus” crewed spacecraft design developed in DRA 5.0 has significant capability and a human exploration strategy is outlined here that uses Copernicus and its key components for precursor near Earth object (NEO) and Mars orbital missions prior to a Mars landing mission. The paper also discusses NASA's current activities and future plans for NTP development that include system-level Technology Demonstrations — specifically ground testing a small, scalable NTR by 2020, with a flight test shortly thereafter.

Hyper-X Flight Engine Ground Testing for X-43 Flight Risk Reduction

Abstract: Airframe-integrated scramjet engine testing has been completed at Mach 7 flight conditions in the NASA Langley 8-Foot High Temperature Tunnel as part of the NASA Hyper-X program. This test provided engine performance and operability data, as well as design and database verification, for the Mach 7 flight tests of the Hyper-X research vehicle (X-43), which will provide the first-ever airframe-integrated scramjet data in flight. The Hyper-X Flight Engine, a duplicate Mach 7 X-43 scramjet engine, was mounted on an airframe structure that duplicated the entire three-dimensional propulsion flowpath from the vehicle leading edge to the vehicle trailing edge. This model was also tested to verify and validate the complete flight-like engine system. This paper describes the subsystems that were subjected to flight-like conditions and presents supporting data. The results from this test help to reduce risk for the Mach 7 flights of the X-43.