[1.12.3] Kerbal Wind Tunnel 1.3.1.1

[aquilux]

@Boots I saw that before you had been asking about shuttle style reentry and there's intersection between that and this mod. As a shuttle enters you actually want to expose only the heat shield on the bottom to the oncoming flow, which necessitates a high AoA (35-45 degrees). This is not optimal for efficient flight, but that's ok, you're TRYING to slow down. Lower you want to come to a more reasonable AoA to maintain minimum speed until you do your flair maneuver to land gently.

Where this intersects with your mod:

Your mod already graphs out pitching moment based on altitude and speed, sweeping the AoA. This is useful as (as long as it's sloping down to the right) where it crosses 0 pitch moment is where your stable AoA is for those entered conditions. The problem is that unlike regular aircraft, you actually WANT this to change as your altitude and velocity comes down from orbital to stopped, and it becomes difficult and tedious to manually change your alt/speed and find all your crossing points and build your own graph of stable angles across speed and altitude. This leads to the point of this post and where a small tweak might help you out as well.

Request of functionality:

I would like to request two new charts under the "flight envelope" section.

1. The first would have the goal of giving a general idea of craft pitch stability across the entire regime from 70km circular orbit to stationary on the ground, called something like "stability" . It would sweep altitude on Y and speed on X, and color in a gradient of red-white-green based on the average pitch of the pitching moment graph corresponding to each point inside user specified bounds for AoA. A useful tool tip here would be the corresponding mach number based on speed and pressure (altitude).
2. The second would have the more complex goal of indicating angles (I say angles as a craft may have more than one) where the craft would be neutrally balanced in pitch potentially be called "neutral pitch angle". It would sweep mach on Y and pitch on X within indicated bounds, and graph out points corresponding to the pitching moment graph where the line crosses 0 moment colored red-wite-green based off of the average slope of the line corresponding to +/-5 (or user indicated) degrees AoA from the crossing point in the same way as the graph above. The thing that may complicate this graph is if altitude (pressure) comes into play more so than just affecting the relationship between speed and mach number. If it does I don't see how not to have speed instead of mach on Y and have the user input altitude, but using a slider to scroll altitude on pre-calculated graph data points would help visualize how the stable AoA changes through the range. A different option would be to use the first graph to do something similar to your flight envelope calculation, derive a "middle of the road" curve from orbital to landed, have altitude on Y, and use the corresponding speed on that line as an input.

With these two graphs it would become much easier to design shuttle style craft. The first would give you an understanding of the overall stability of the craft as designed through it's entire flight regime, and the second would help verify the craft will hold the desired pitch angle with neutral inputs as well as highlight at what points an attitude upset would be more likely and what other AoAs it may settle into stably post upset.

[Booots]

On 8/13/2024 at 4:58 PM, aquilux said:

@Boots I saw that before you had been asking about shuttle style reentry and there's intersection between that and this mod. As a shuttle enters you actually want to expose only the heat shield on the bottom to the oncoming flow, which necessitates a high AoA (35-45 degrees). This is not optimal for efficient flight, but that's ok, you're TRYING to slow down. Lower you want to come to a more reasonable AoA to maintain minimum speed until you do your flair maneuver to land gently.

1. The first would have the goal of giving a general idea of craft pitch stability across the entire regime from 70km circular orbit to stationary on the ground, called something like "stability" . It would sweep altitude on Y and speed on X, and color in a gradient of red-white-green based on the average pitch of the pitching moment graph corresponding to each point inside user specified bounds for AoA. A useful tool tip here would be the corresponding mach number based on speed and pressure (altitude).
2. The second would have the more complex goal of indicating angles (I say angles as a craft may have more than one) where the craft would be neutrally balanced in pitch potentially be called "neutral pitch angle". It would sweep mach on Y and pitch on X within indicated bounds, and graph out points corresponding to the pitching moment graph where the line crosses 0 moment colored red-wite-green based off of the average slope of the line corresponding to +/-5 (or user indicated) degrees AoA from the crossing point in the same way as the graph above. The thing that may complicate this graph is if altitude (pressure) comes into play more so than just affecting the relationship between speed and mach number. If it does I don't see how not to have speed instead of mach on Y and have the user input altitude, but using a slider to scroll altitude on pre-calculated graph data points would help visualize how the stable AoA changes through the range. A different option would be to use the first graph to do something similar to your flight envelope calculation, derive a "middle of the road" curve from orbital to landed, have altitude on Y, and use the corresponding speed on that line as an input.

Hey there! I just moved and started a new job, but as I get back into modding KSP again I like this idea. I once thought about implementing #1 but realized that I couldn't do this efficiently because the matrix of points to evaluate becomes 3-dimensional instead of two (sweeping AoA for each speed/altitude combo), which makes the computation take a lot longer. But! Around six months ago I figured out a way to rewrite how this mod does the aerodynamics calculations in a way that would sacrifice a small amount of accuracy for a huge boost in speed. The problem is that I needed to do a bunch more coding from the ground up and my first attempt at it (which was all I had time for at the time) failed spectacularly with highly erroneous results.

But now that I should have a bit more free time, I aim to add both of these plots (actually combined as one plot where the color corresponds to the AoA range between the neutrally stable angles) and a bunch more data for glide vehicles.