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

[blowfish]

When was that cockpit added to B9?

It was mistakenly included in one of the releases - it's not done yet and if you saw it up close you would understand why.

[Van Disaster]

Well thats a bit better ( there is a fairly sizable bit of runway left now ) but the wings look a tad oversized.

Interesting how much more wing your lifters run, but you seem to favour a pair of engines more in each class than I do. I managed to put 75t in LKO with two SABRE Ms, although it took a good 25 mins...

[Hodo]

https://farm9.staticflickr.com/8579/15909198056_db8042b332_c.jpg

Well thats a bit better ( there is a fairly sizable bit of runway left now ) but the wings look a tad oversized.

Interesting how much more wing your lifters run, but you seem to favour a pair of engines more in each class than I do. I managed to put 75t in LKO with two SABRE Ms, although it took a good 25 mins...

I tend to over-engineer many of my designs. I come from the Gruman and Republic aircraft school of thought, "redundancy is safety!"

I also like having a bit more power to take less time getting something somewhere. I think my average in space time is less than 15min except for system lag. But gametime 15min is average for most of my heavy haulers, and less than 10 for my light weight stuff.

The redundant systems can REALLY be seen in this landing picture of my long haul craft, that takes comm sats up to geosync orbit in a single bound.

Two chutes,

20 air brakes,

several sets of landing gear,

2 communications omnidirectional antenna and a single dish,

2 battery sets

2 generators

and life support to have the crew of 7 survive in space for a year.

Yep, slightly over engineered, but it hasn't failed me yet.

[blowfish]

On the subject of engine number, what's the lowest (runway) TWR you have been able to use? I can't seem to get off the runway if I go much below 0.5 (and even that is questionable), but I could probably be doing more with flaps for added lift.

[Van Disaster]

I have a few options for low TWR, given having asked for a longer runway a few times & told it'll never happen:

* Use droptanks & run sabres in rocket mode - this has the advantage of letting you temporarily shift CoM back a bit.

* use powered landing gear

* Use SRBs! pretty spectacular.

* Use the 4km desert runway from Kerbinside

* Just run off the end...

I don't tend to check TWR for my heavy spaceplanes ( somewhere around 0.5 I believe ) - the problem I have is my current layout has the rear wheels in a position to avoid tailstrikes, but that's a long way from CoM which I try and keep in the middle of the payload bay. I got the frame I use while I'm trying to develop more intelligent droptanks into the air halfway down the runway with 0.39 though:

To be fair it has enormous flaps, and empty the takeoff run is absurdly short anyway:

[Drew Kerman]

On the subject of engine number, what's the lowest (runway) TWR you have been able to use? I can't seem to get off the runway if I go much below 0.5 (and even that is questionable), but I could probably be doing more with flaps for added lift.

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Thanks to the 1.47 bugs with Tweakscale it greatly increased the weight of my K-130 and I didn't notice the difference since I hadn't flown it much. So when I loaded it with science drop pods the total weight gave me a 0.46 TWR. With full flaps, brakes on until max thrust, and the full length of the KSC runway I can make it into the air off the end and get positive rate of climb. Once I realized the Tweakscale issue and downgraded to 1.44 I realized my TWR is really around .86 but it's nice to know I can get off the ground with a 0.46!

[kcs123]

Latest test flight with WIP SSTO heavy lifter craft I was able to take off with 0.36 TWR. MJ in SPH editor shows 0.4 TWR, but since I'm using Advanced Jet Engines mod that nerfs jets further, actual TWR on take off is 0.30 - 0.36. I have used 24 x 20.3t Kibbal parts from Station Science mod for total of 487.2 t as payload. If you count other small parts like batteries inside cargo bay payload could be rounded to 490t.

Craft is stable in flight with much lower TWR, so it is just a metter to have runway long and strong enough to be able to accelerate to take off speed. Take off with lower TWR is possible with higher wing span, but it is not practical on supersonic speeds.

Tricky part with wings is to find good shape and ratio that will alow you stable low speed take off and landing. At the same time that must not weight too much because at high altitude and supersonic speed you can have same L/D ratio with smaller wings.

Also in space large wings are not usefull at all, you can't have any lift from wings in space at all and additional weight from wings is only unwanted dV drainer.

However building heavy SSTO planes make sanse if you have enough cargo space for craft/station assemblies that you connect together in space. Because it can be 100% recovered it is much more economy wfficient then rocket for the same sized payload.

[Aedile]

Latest test flight with WIP SSTO heavy lifter craft I was able to take off with 0.36 TWR. MJ in SPH editor shows 0.4 TWR, but since I'm using Advanced Jet Engines mod that nerfs jets further, actual TWR on take off is 0.30 - 0.36. I have used 24 x 20.3t Kibbal parts from Station Science mod for total of 487.2 t as payload. If you count other small parts like batteries inside cargo bay payload could be rounded to 490t.

Craft is stable in flight with much lower TWR, so it is just a metter to have runway long and strong enough to be able to accelerate to take off speed. Take off with lower TWR is possible with higher wing span, but it is not practical on supersonic speeds.

Tricky part with wings is to find good shape and ratio that will alow you stable low speed take off and landing. At the same time that must not weight too much because at high altitude and supersonic speed you can have same L/D ratio with smaller wings.

Also in space large wings are not usefull at all, you can't have any lift from wings in space at all and additional weight from wings is only unwanted dV drainer.

However building heavy SSTO planes make sanse if you have enough cargo space for craft/station assemblies that you connect together in space. Because it can be 100% recovered it is much more economy wfficient then rocket for the same sized payload.

Planes make whole lot of sense to low orbit. After that just pick the payload with a nuke powered orbital tug.

[Van Disaster]

TBH in KSP with it's lack of limits on hypersonic airframes you can do it without even needing an orbiter, you only need to get out of the atmosphere long enough to lob the payload with an orbital insertion booster out of the cargo & fire it off.

Big spaceplanes make economic sense if you lift a *lot*, otherwise the startup cost is a bit of a killer. Reusable rocket airframes ( SpaceX style ) are a fraction of the cost, just a lot heavier on fuel. Winged rockets might be an interesting mix to look at...

[Crzyrndm]

Small bug report with the aero tinting window. If you enter a very small Cl (probably Cd as well) factor such as 0.000005 the tinting GUI window breaks down.

Log

It also seems strange that I needed to make the Cl that small or smaller to see any tinting

NOTE: To get any tinting I had to get the AoA up to about 1 degree (craft cruises at ~0.4)

[Montaño]

Hi, just one question.

Is it possible to obtain the tabulated values of the polar graphs? It would be quite useful to make more in deep analysis.

In fact, there is any way to expand the graphs to the interval [90,-90]? I mean: I think that it could be useful to know the drag of a capsule in the re-entry...

Thank you!

[kcs123]

Small bug report with the aero tinting window. If you enter a very small Cl (probably Cd as well) factor such as 0.000005 the tinting GUI window breaks down.

http://i.imgur.com/3PWCF8J.png

Log

It also seems strange that I needed to make the Cl that small or smaller to see any tinting

http://i.imgur.com/MJ7G5hZ.png

NOTE: To get any tinting I had to get the AoA up to about 1 degree (craft cruises at ~0.4)

Never got a problem with GUI like that. Not saying that bug doesn't exist, though. It is not strange that you don't see any lift, most probably your plane doesn't provide any, or have very little lift.

We have good debate about it, you may check post in SSTO design contest thread and few post after that to find out why.

Hi, just one question.

Is it possible to obtain the tabulated values of the polar graphs? It would be quite useful to make more in deep analysis.

In fact, there is any way to expand the graphs to the interval [90,-90]? I mean: I think that it could be useful to know the drag of a capsule in the re-entry...

Thank you!

I think that you misunderstand how FAR graph works. Tabulated values are not global NAV point values. Those are relative values from craft prograde vector.

And you can enter interval values from [-90 , +90], but not [90,-90].

Edited December 5, 2014 by kcs123

[Hodo]

Never got a problem with GUI like that. Not saying that bug doesn't exist, though. It is not strange that you don't see any lift, most probably your plane doesn't provide any, or have very little lift.

We have good debate about it, you may check post in SSTO design contest thread and few post after that to find out why.

I think that you misunderstand how FAR graph works. Tabulated values are not global NAV point values. Those are relative values from craft prograde vector.

And you can enter interval values from [-90 , +90], but not [90,-90].

KCS is right, I think you are mistaken in your reading of the graph. I rarely if ever use a capsule for anything, unless it is in my RSS install and in that case, I have re-entry down to a science. I know what works and what burns up.

Even in my "normal" install I rarely use the AoA part of the graph but I live by the FAR mach graph and the numbers chart, those two bits of information is enough for me to know if the craft will fly or be a brick.

I have now started making some designs that are quite low drag and VERY efficient in the SSTO lifter area, and we wont even talk about my fighters. Since the F/A-106A that I entered in the challenge linked by KCS, I have made about 12 new craft, and the latest bunch are almost 2/3rds of the drag of the 106. And that has just been further understanding those charts and numbers.

[krillin678]

I am having some issues with far/near with time warp in orbit. Lots of mods. Where can I go to report on my findings? My ships are getting frozen in orbit or spontaneously exploding.

Edit: Found major conflict in mods not related to far/near. It is a real bummer as now I will have to comb the files to find what one is doing it. So probably NOT related to far/near

Edited December 6, 2014 by krillin678
more info

[Starman4308]

I am having some issues with far/near with time warp in orbit. Lots of mods. Where can I go to report on my findings? My ships are getting frozen in orbit or spontaneously exploding.

Follow these instructions to get help: if you've pinned it down to FAR/NEAR, this thread is usually okay.

However, it is extremely unlikely that FAR or NEAR is the the root of your problems, on account of FAR/NEAR only changing the aero model.

[Rakaydos]

I dont know whether it's a problem with my ship or what, but when I have the Flight Asistance: Yaw active without SAS, I'm slowly turning to the right, eiither on the runway or in the air.

Can someone please help me track down the problem?

https://www.dropbox.com/s/jpjdlfn5nbddavm/Manticore%20v7.craft?dl=0

[Rakaydos]

Also:

Doesn anyone know why the Bicoupler has less drag than the Mk 1 to Mk 2 adaptor?

[Montaño]

Mmmm, probably I explained the question very bad...

Or maybe I have in fact no idea.

I think that the AoA is the angle between velocity vector and the x vector of the coordinate system of the body. It should be so.

When a capsule or the command pod re-enters in the atmosphere, it usually point to the retrograde direction (more or less) making a 180º angle with the velocity vector:

So my question was: can FAR give me the drag coefficient value for a 180º angle?

Because I really belives the drag coefficient is not the same for 0º and 180º. I mean, it should not be the same! Or maybe the AoA definition is not as I though... I don't know.

Anyway, my question was also if it is possible to have the tabulated graphs. You know, to do the math.

[ferram4]

@Cryzyrndm: Yeah, I found out what that was. That's when double.ToString() shifts from standard floating point output to scientific notation. I've fixed that for the next build.

@Montaño: Dumping from the graphs is planned, I just haven't updated to the fork of the graph code that includes that yet. Also, AoA = 0 is measured relative to the default "forward" direction in the editor; you can flip the capsule around and it'll simulate fine around that new 0.

@Rakaydos: If it's yawing constantly in one direction, that means it is not symmetrical. You will have to remove the asymmetry, then it will not yaw.

Also, there is a simple explanation for why the bicoupler makes less drag than the adapter: drag is based partly on the change in cross-sectional area per unit length. The bicoupler changes cross-sectional area very little, while the adapters tend to change it a lot more.

And a final note: biplanes are a terrible design choice. When the wings aren't as close together as you have them, they only produce 20% more lift than a single wing, not double; the design you have is going to be much, much worse than that. Biplanes, triplanes, and other multiplanes only existed because they had better structure than monoplanes given all the other constraints at the time. Anything going above Mach 0.4 probably shouldn't be a biplane.

[Montaño]

@Cryzyrndm: Yeah, I found out what that was. That's when double.ToString() shifts from standard floating point output to scientific notation. I've fixed that for the next build.

@Montaño: Dumping from the graphs is planned, I just haven't updated to the fork of the graph code that includes that yet. Also, AoA = 0 is measured relative to the default "forward" direction in the editor; you can flip the capsule around and it'll simulate fine around that new 0.

@Rakaydos: If it's yawing constantly in one direction, that means it is not symmetrical. You will have to remove the asymmetry, then it will not yaw.

Also, there is a simple explanation for why the bicoupler makes less drag than the adapter: drag is based partly on the change in cross-sectional area per unit length. The bicoupler changes cross-sectional area very little, while the adapters tend to change it a lot more.

And a final note: biplanes are a terrible design choice. When the wings aren't as close together as you have them, they only produce 20% more lift than a single wing, not double; the design you have is going to be much, much worse than that. Biplanes, triplanes, and other multiplanes only existed because they had better structure than monoplanes given all the other constraints at the time. Anything going above Mach 0.4 probably shouldn't be a biplane.

Thank you ferram, that was exactly what I was asking!

[Rakaydos]

That's the thing, it doesnt yaw when I have Flight Assist OFF, only when I have it ON.

As for being a biplane... does FAR even model that? given the other shortcuts, I find it easy to imagine it not doing so, so long as the angle of attack doesnt stall the plane.

And it lets me do a "frisbee" reentry with hardly any atmo heating at all- I see more flames going up than I do going down.

Edited December 6, 2014 by Rakaydos

[Hodo]

Ferram I have a request for an additional tool to FAR. Can we get a lift indicator slider? One that lets us see where the CoL is at, say mach 1 or mach 5 on a specific craft?

Currently we can build the craft CoM and CoL to the static CoL but doesn't the CoL shift rearward at supersonic speeds and hypersonic speeds?

[Kitspace]

Do the control surfaces require any special configs or something?

In my case with the new version not all of them including some of the stock ones got the new tweaks for some reason.

Edited December 6, 2014 by Kitspace

[Van Disaster]

Ferram I have a request for an additional tool to FAR. Can we get a lift indicator slider? One that lets us see where the CoL is at, say mach 1 or mach 5 on a specific craft?

Currently we can build the craft CoM and CoL to the static CoL but doesn't the CoL shift rearward at supersonic speeds and hypersonic speeds?

One of the derivatives will show the effect of CoL/CoM balance, but agreed that would be a nice thing - along with a slider for full/empty rather than a toggle, perhaps. ( and wing loading! ).

[Crzyrndm]

Another bug report:

The stability derivates are changing depending on the flap settings of the previous calculation

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Test Craft (all stock parts)