possible BUG: SUAVE traveling back in time

[Hu gePanic]

I just realized that SUAVE travels back in time if you request too much from the airplane-model.

When I fly a mission like this:

Segments    = SUAVE.Analyses.Mission.Segments
segment     = Segments.Climb.Constant_Throttle_Constant_Speed(base_segment)
segment.tag = "test"
segment.analyses.extend( analyses.cruise )
segment.altitude_start = 35000 * Units.ft
segment.altitude_end   = 70000* Units.ft
segment.air_speed      = 370* Units.kt
segment.throttle       = 1

and there is not enough thrust available, it will go back in time.  

--> check the X-Axis!!

If I increase the available thrust, it will solve fine!

Is this a new bug?

[Emilio]

Hi,

Sorry for the delay.

This is not new. It's not a bug, it's a feature. Haha.

But seriously what this is saying is that the only way the equations of motion can be satisfied is that if the airplane is descending. Thinking of negative time saying you've swapped your start with your finish.

Why is this a feature? In an optimization case it provides an answer that can be returned back to an optimizer rather than a NaN or something. If this start to occur your constraint is that the last time is greater than the first time. For most cases this constraint won't be active.

-Emilio

[Hu gePanic]

Hi, thanks for the answer.

I see this similar as the "negative-thrust" you get when descending too slow and steep.

For me this results in 5-line code to check for negative-thrust, and also for negative-time.

I would love to have some feature in the results that show such "features". Like a "error-log" that can be checked to validate results (if len(results.errors)>0: print("Something went wrong, check results.errors!")

Thanks

[Emilio]

Thanks for the feedback. Yeah we discussed this internally. Hopefully it will be a 3.0 feature!

-Emilio