[1.3.1] Ferram Aerospace Research: v0.15.9.1 "Liepmann" 4/2/18

[thorfinn]

Tandem wings work, on the other hand.

(Though going Mach 5 with them is also probably not the best idea)

[RobsterCraw]

I've been struggling with writing a launch script for kOS for use with FAR. Are there any resources that have the formulas for atmospheric density (as it relates to altitude) and/or a list of ways to pull FAR variables like coefficient of drag, reference area, or whatever is used to calculate force of drag. I'm sorry if this is a stupid question, but I haven't found an answer by searching the thread or elsewhere.

[Camacha]

I've been struggling with writing a launch script for kOS for use with FAR. Are there any resources that have the formulas for atmospheric density (as it relates to altitude) and/or a list of ways to pull FAR variables like coefficient of drag, reference area, or whatever is used to calculate force of drag. I'm sorry if this is a stupid question, but I haven't found an answer by searching the thread or elsewhere.

You are asking for quite a lot and this is a notoriously difficult task A lot of people have tried and given up on doing this sort of calculation, only recently a couple seem to have succeeded a bit in the form of trajectory calculation and prediction.

[RobsterCraw]

@ Camacha: Hmm, is it notoriously difficult to optimize a trajectory properly or to even just come up with some simplified model? If it's near impossible to do this with formal calculations that will optimize any craft's flight, maybe I could just come up with launch script where the velocity and pitch are some function of max Q, and Fg, and then just come up with a way to model a third term by logging data and trial and error for each launch vehicle so I can just make it a declared parameter when the script is run..

[DaMichel]

I'm only farmiliar with FAR, not with KOS. I assume by your question that KOS doesn't support FAR in way that it would be possible to obtain data from it.

But if you are willing to modify KOS, it would be relatively straight forward to get the data using C# reflections. A lot of it is contained in member variables of FARControlSys. Here is how KerbalFlightData pulls the values: https://github.com/DaMichel/KerbalFlightData/blob/master/KerbalFlightData.cs#L259. As Camacha said, the trajectory calculation plugin is probably a good source, too.

Edited December 19, 2014 by DaMichel

[Camacha]

@ Camacha: Hmm, is it notoriously difficult to optimize a trajectory properly or to even just come up with some simplified model? If it's near impossible to do this with formal calculations that will optimize any craft's flight, maybe I could just come up with launch script where the velocity and pitch are some function of max Q, and Fg, and then just come up with a way to model a third term by logging data and trial and error for each launch vehicle so I can just make it a declared parameter when the script is run..

On of the 'problems' with FAR is that a lot depends on the exact orientation of the craft. If you change that a little bit, everything changes, along with any calculations. So on paper a lot is possible, but making it useful is another matter. I love what FAR does in that respect, no easy answer there. You really need to engineer some sort of solution.

I assume by your question that KOS doesn't support FAR in way that it would be possible to obtain data from it.

It is. kOS is now capable of obtaining any and all right click menu data available. That should make life a little easier.

Edited December 19, 2014 by Camacha

[ferram4]

v0.14.5.1 is out, with some sanity checks in the Stab Deriv GUI, skin friction drag that actually tends towards a rarefied gas value for at the edge of the atmosphere, and a Reynolds Number readout, because why not?

[DresCroffgrin]

v0.14.5.1 is out, with some sanity checks in the Stab Deriv GUI, skin friction drag that actually tends towards a rarefied gas value for at the edge of the atmosphere, and a Reynolds Number readout, because why not?

Once again, ferram, you improve the best mod for this game. One question though, as an aerospace engineer looking for context: what is your reference length for Reynolds Number?

[ferram4]

It's difficult to get the total reference length, because that turns into a geometry nightmare. Instead, it uses the length of each part / mean aerodynamic chord of each wing part to calculate local Reynolds numbers. The readout shows an average of those numbers.

[SanderB]

I'm trying out v0.14.5.1 and the ballistic coefficient of one my rockets (with a fairly normal build) is 12k at launch (pointing along the velocity vector) and progressively gets lower and lower, down to 1k and even 250 at its lowest. Is this normal? It's quite a difference from previous versions.

[ferram4]

Yes, that is the result of the skin friction drag coefficient increasing with decreasing Reynolds number and the reduction in mass as you burn off fuel. Perfectly normal.

[Hodo]

Does this mean if we covered our craft in teflon we would go faster?

[SanderB]

What are our rockets covered with, sand paper perhaps?

[ferram4]

They are using the numbers based on theoretically perfectly smooth flat plate, with the exception of rarefied gas, where it's using perfectly diffuse reflection of molecules as its approximation. In either case, no, sand paper would result in more drag.

[Buzzer]

Is that possible to reach ~*200,000m with only the stock command module and one Solid Fuel Booster? I wasnt able to reach even *20,000m without FAR...

I´ve followed the instructions and I´m running it on KSP 32bit (Windows 7)

* Edited after a few more tries.

Edited December 19, 2014 by Buzzer

[Hodo]

So with the new fluid dynamic model that you are starting, are you considering starting a water dynamic mod?

[BudgetHedgehog]

Is that possible to reach ~*200,000m with only the stock command module and one Solid Fuel Booster? I wasnt able to reach even *20,000m without FAR...

I´ve followed the instructions and I´m running it on KSP 32bit (Windows 7)

* Edited after a few more tries.

Welcome to realistic aerodynamics. Now you know why it's called a souposphere in stock.

[Hodo]

Is that possible to reach ~*200,000m with only the stock command module and one Solid Fuel Booster? I wasnt able to reach even *20,000m without FAR...

I´ve followed the instructions and I´m running it on KSP 32bit (Windows 7)

* Edited after a few more tries.

Yes it is possible if you go straight up. Granted the G Forces and the TWR on that craft will cause the dynamic Q at the front of the rocket to be so high it may flip over and explode.

[jstnj]

Not sure which mod is at fault here...but I am trying to reenter Kerbin's atmosphere in a mk1 pod with a DRE heatshield and a RealChutes mk26 parachute and the slowest I can get before crashing into the ground is about 575m/s (can't deploy chute).

Any ideas whats going on here? It seems that there isnt enough drag through the atmosphere to slow the pod down?

Running 14.5.1 clean fresh install on .90

Edited December 20, 2014 by jstnj

[ferram4]

Why did you clip the heat shield into the bottom of the pod and confuse FAR? Why did you add a heat shield when the MkI pod has one built-in anyway?

Hell, how did you even manage that, I fixed that particular clipping-induced bug, why is it coming back?

[Zilentification]

Not sure which mod is at fault here...but I am trying to reenter Kerbin's atmosphere in a mk1 pod with a DRE heatshield and a RealChutes mk26 parachute and the slowest I can get before crashing into the ground is about 575m/s (can't deploy chute).

Any ideas whats going on here? It seems that there isnt enough drag through the atmosphere to slow the pod down?

I am having the same problem.

On a Clean install with just Far and Deadly Reentry my command pod wont slow down enough. I've tried reentry at different periapsis's, and different speeds. All that is attached to the Pod is the default starting parachute. I keep hitting the ground/water at speeds of 400-500m/s which means I never slow down enough allowing me to deploy the parachute.

Not sure if this helps but I just did a quick orbital flight to come up with these numbers.

Was in a 100 by 100 orbit around Kerbin. Did a retro burn to lower Peri to 25km This is my altitude vs surface speed as I re-entered.

• 50Km, 2143m/s
  
• 40km, 2136m/s
  
• 30km, 1975m/s
  
• 20km, 1540m/s
  
• 10km, 913m/s
  
• 05km, 558m/s
  
• 01km, 340m/s
  
• Splat.
  

Edited December 20, 2014 by Zilentification

[Camacha]

Why did you add a heat shield when the MkI pod has one built-in anyway?

A Mk. 1 has a built in heat shield?

*Camacha mumbles to himself and shakes his fist at nothing.

[steve_v]

Sure does, you can probably reduce it's quota of ablative for most re-entries too.

That said, I have noticed stuff not slowing down as quickly as it used to... no big deal, but a mk.1 pod with something heavy (i.e. an engine) on the bottom and no other drag inducing parts crashes into terrain at supersonic speeds.

Edited December 20, 2014 by steve_v

[FiftyShades]

I am having the same problem.

On a Clean install with just Far and Deadly Reentry my command pod wont slow down enough. I've tried reentry at different periapsis's, and different speeds. All that is attached to the Pod is the default starting parachute. I keep hitting the ground/water at speeds of 400-500m/s which means I never slow down enough allowing me to deploy the parachute.

Not sure if this helps but I just did a quick orbital flight to come up with these numbers.

Was in a 100 by 100 orbit around Kerbin. Did a retro burn to lower Peri to 25km This is my altitude vs surface speed as I re-entered.

• 50Km, 2143m/s
  
• 40km, 2136m/s
  
• 30km, 1975m/s
  
• 20km, 1540m/s
  
• 10km, 913m/s
  
• 05km, 558m/s
  
• 01km, 340m/s
  
• Splat.
  

Oh wow so its not just me... I never had this issue in the .25 build but since the update even on a sub orbital, non orbit trajectory... 1400m/s at 85,000m and still at almost 400 to 500m/s at 1000m, If i even dream of deploying a chute the chute fails.

However the exact same install on another computer doesnt seem to share the issue, the only difference between the two craft on different machines is the deathbomb had two goo containers.

[Funeh]

Do I need ModuleManager?

Yes; it is used to properly apply aerodynamic properties to stock wing parts and re-balance the stock jet engines to have more reasonable performance. If you do not copy it over FAR will not function properly.

Hi, so is there ModuleManager for 0.90 so I can use FAR? I have only found version for 0.20 ( http://forum.kerbalspaceprogram.com/threads/31342-0-20-ModuleManager-1-3-for-all-your-stock-modding-needs )