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Static Analysis with FAR
Ferram Aerospace Research (FAR) allows for users to perform static analysis on aircraft in the Space Plane Hanger (SPH). The static analysis window can be brought up by clicking on the FAR icon in the toolbar in the SPH, then clicking the "Static" button at the top of the FAR Control & Analysis Systems window that pops up.
Aircraft performance changes with craft orientation and Mach number; therefore, it is important to note how variations in orientation and Mach number affect vehicle behavior. The static analysis provides two ways to "sweep" one of these variables, while keeping the other constant to determine how vehicle performance changes as a function of one of these variables.
This will vary the vehicle's angle of attack (the difference between the velocity vector and the craft's forward vector along the pitch axis) while holding Mach number constant. This is used to determine how a craft behaves in stall, how efficiently it lifts, and if there are any regions of instability in the design. This will function by starting the AoA at the lower bound, increasing it to the upper bound, and then decreasing it back to the lower bound; this allows performance with increasing and decreasing angle of attack to be collected, such as showing the hysteresis that stall exhibits with respect to AoA.
This varies the vehicle's Mach number while maintaining a constant AoA. This is generally used to check how drag varies with Mach number and if there are any stability issues in the transonic regime (near Mach 1, where vehicles can become highly unstable). As there are no significant hysteresis effects when varying Mach number, the sweep simply begins with Mach number at the lower bound and then increases it to the upper bound.
These mark the boundaries of the independent variables for the sweep. For the AoA sweep, these are angles of attack in degrees, while for the Mach number sweep, these are Mach numbers. There is a third value that specifies the Mach number for AoA sweep or the AoA for a Mach number sweep.
If flaps are included on the aircraft, they will affect the lift, drag, and pitching moment. FAR will simulate aircraft performance at any flap setting. A flap setting of 0 represents no flaps (fully retracted) and a flap setting of 3 represents full flaps (fully deployed). In general, flaps increase lift and drag coefficients, decrease the pitching moment coefficient. Any flaps set up as leading edge slats will reduce the lift coefficient slightly, but will increase the stall angle by several degrees.
To simulate the airplane behavior with control surfaces deflected, FAR allows the user to specify a pitch setting. This is the amount that the elevators and other pitch control surfaces are deflected. A value of 0 represents no deflection, and a value of 1 represents full deflection. Deflecting elevators in general increases the lift and drag coefficients, and either increases or decreases the pitching moment coefficient depending on aircraft configuration (decreases for conventional configurations, increases for canards).
When airplanes burn fuel, the center of mass of the aircraft moves. This can greatly impact the stability of the aircraft. Check this box to simulate the aircraft with a full fuel load, and uncheck it to simulate the aircraft with no fuel.
If spoilers are included on the aircraft, checking this box will tell FAR to simulate the aircraft with spoilers deployed. Spoilers in general decrease the lift coefficient, and increase the drag and pitching moment coefficients.
Because FAR overrides the stock game's aerodynamics, it also needs to override the code that draws the "Center of Lift" (CoL) indicator, which indicates the Center of Lift, or Neutral Point, of the aircraft. Sometimes, however, the game still draws this indicator as if the stock aerodynamics were in effect. If this happens, users can click the "Update CoL" button to redraw the indicator with FAR aerodynamics.
This is a non-dimensional aerodynamic coefficient used to measure of the lift created by the vehicle; for winged vehicles this is approximately linear with angle of attack until it reaches the critical angle of attack, which is where maximum lift occurs and where stall occurs (the sudden drop in lift). For an aircraft, more of this is always good. For a rocket, lift is generally bad due to the fact that it can be a strong source of instability.
This is a non-dimensional aerodynamic coefficient used to measure the drag of a vehicle; this is approximately linear with CL2 for winged vehicles at low angles of attack, but becomes highly non-linear at higher angles of attack, notably post-stall. For wingless vehicles it is highly non-linear at all times. Low drag is generally desirable for rocket launches, planes in cruise and spaceplanes during ascent, but high drag is generally desirable for reentry vehicles, planes on a landing approach, and spaceplanes during reentry.
This is a non-dimensional aerodynamic coefficient used to measure the pitching moment (like a torque) of the vehicle. This is generally linear with CL for winged vehicles at low angles of attack, but its behavior is difficult to predict post stall and for wingless vehicles. How this value varies with AoA is key to designing a stable vehicle; it must decrease with increasing AoA (a downward sloping line) for the vehicle to be stable in that AoA range; increases in CM at a certain AoA cause pitch instability.
This is simply CL / C D and acts as a measure of how efficient the vehicle is at lifting. To fit on the same scale, this value is reduced by a factor of ten to make reading the graph easier.
Written for FAR v0.13.3.