Document
ment of these slots would be chosen, in of the cap. Small tangential holes could downward against the spring. This conjunction with those of other compo- be included, in addition to the outer downward motion would cause the nents, to optimize performance. slots, to allow initial flow at the lowest outer slots in the cap to partially expose The upper end of the injection tube power level. The cap and the exposed the tangential slots in the injection tube, would be covered with a cap that would portion of the injector tube would pro- thereby limiting the pressure drop by in- contain a number of outer slots equal to trude into a manifold containing the creasing the cross-sectional area for flow the number of injection slots. The cap fluid to be injected, and outer flanges on into the tube. The number and dimen- would translate axially (up and down in the cap would contribute drag between sions of the tangential slots would be the figure). Two retaining pins (of which the cap and the fluid to damp any oscil- chosen in conjunction with the stiffness one can be seen in the figure) in holes latory motion of the cap, thereby helping and preload of the spring to obtain the in the cap would protrude into grooves to suppress instability. Labyrinth-type optimum pressure drop as a function of in the injection tube to prevent the cap seal grooves would prevent gross leakage, the rate of flow (and, hence, as a func- from coming off the injection tube while so that most of the flow must enter the tion of the combustion power level).
allowing the cap to slide freely only injection tube either through the tan- This work was done by Huu Trinh and within limits. The pins would also keep gential slots or the small tangential holes. William Myers of Marshall Space Flight Center.
the outer slots in the cap aligned with In operation, the pressure drop be- This invention is owned by NASA, and a the injection slots in the tube. tween the manifold and the inside of the patent application has been filed. For further A coil spring would lie in an annular cap (which pressure drop would be part information, contact Sammy Nabors, MSFC recess in the injection tube and would be of the total pressure drop from the man- Commercialization Assistance Lead, at compressed between the bottom of the ifold to the combustion chamber) would sammy.a.nabors@nasa.gov. Refer to MFS- recess and an inner flange at the bottom create a force that would push the cap 32518-1.
Handling Qualities Prediction of an F-16XL-Based Reduced
Sonic Boom Aircraft
This technique helps determine how much an aircraft could be modified without affecting its baseline handling qualities.
Dryden Flight Research Center, Edwards, California A major goal of the Supersonics Proj- isting NASA DFRC F-16XL simulation was modified to represent potential ect under NASA’s Fundamental Aero- that would be providing data for this ef- aerodynamic and mass properties nautics program is sonic boom reduction fort, as well as the handling qualities changes due to the aircraft modifica- of supersonic aircraft. An important part tools that would analyze the data. The tions. The values of these parameters of this effort is development and valida- second part was modifying the simula- represent a best guess of how proposed tion of sonic boom prediction tools used tion to represent the modified aircraft modifications would affect aircraft aero- in aircraft design. NASA Dryden’s F- and determining the modification enve- dynamic and mass properties. The pa- 16XL was selected as a potential testbed lope, which showed how much of the air- rameters selected were those thought to aircraft to provide flight validation. craft could be modified without affect- be most affected by the modifications.
Part of this task was predicting the ing baseline aircraft handling qualities. The simulator was set up at one of a handling qualities of the modified air- Validation of the F-16XL simulation was list of various flight conditions with one craft. Due to the high cost of modifying important as the simulation had not been of the parameters modified. Pitch and the existing F-16XL control laws, it was used for research in over 10 years. Up- roll frequency sweeps were input into desirable to find modifications that re- dates and modifications had been made the simulation and simulation response duced the aircraft sonic boom but did to the simulation for use as a demonstra- was recorded. These data were then not degrade baseline aircraft handling tion device. Check case data included input into the handling qualities tools, qualities allowing for the potential of with the simulation were compared with and the handling qualities of the modi- flight test without changing the current data generated from the current simula- fied aircraft were predicted. The final control laws. This was not a requirement tion and matched almost exactly. Pilot step was to have pilots perform a task in for the initial modification design work, input from flight test data was fed into the the simulator and make handling quali- but an important consideration for pro- simulation, and aircraft response was ties ratings and comments. A tracking ceeding to the flight test option. compared to simulation response. task was set up in the simulator and per- The primary objective of this work Validation of the handling qualities formance criteria were defined. This was to determine an aerodynamic and tools was also important as these tools would allow final validation of the han- mass properties envelope of the F-16XL had been updated and modified since dling qualities tools.
aircraft. The designers could use this being used for F-16XL analysis. Flight This work was done by Bruce Cogan and envelope to determine the effect of pro- test and simulation data were input into Seung Yoo of Dryden Flight Research Center.
posed modifications on aircraft han- the handling qualities tools and com- Further information is contained in a TSP dling qualities. pared to past results. (see page 1) . DRC-009-040 The approach to this objective had With the simulation and handling two parts. First was validation of the ex- qualities tools validated, the simulation 22 NASA Tech Briefs, October 2010