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

[NoClass]

:ma

If you put a craft on the launchpad or runway or whatever, when flying your plane for re-entry, set that as your target.

You can also plant flags! I have three near KSP, labelled "RW09", "RW27", and Old Runway. They're better than nothing, though it's hard to discriminate precise headings, courses, and glideslopes off of the navball.

Oh, what I would do for some proper NAVAIDs! Maybe I'll have to look into MJ just for the spaceplane guidance.

@TeeGee: Have you tried using the trim controls (Alt+QWEASD) to control your spaceplane at hypersonic speeds? They are slightly tricky because they don't revert to centre so you have to do it yourself, but they are extremely gentle and precise and can make attitude changes at high speed with too much control-surface much easier.

This! Trim makes all the difference in the world if you just want a touch of elevon at a time. You can totally fly long distances using incremental trim touches once you get it centered.

Of course getting it centered is a pain, as the trim setting moves SLOWLY (ugggh), and can't be mapped to a controller (UGGH!). It would also be nice for there to be a trim toggle button, that jumps trim to whatever control input you or SAS is using.

Also, go ahead and get yourself a controller. I use a Logitech Dual Action controller, and it made flying winged aircraft waaaaay easier. In the meantime using the precision controls (CAPS LOCK toggle) is also helpful.

[RoboRay]

:ma

You can also plant flags! I have three near KSP, labelled "RW09", "RW27", and Old Runway. They're better than nothing, though it's hard to discriminate precise headings, courses, and glideslopes off of the navball.

If you put a flag every couple of kilometers west of the runway along the centerline, heading toward the mountains, you get a longer line to use for visually orienting yourself.

the trim setting moves SLOWLY (ugggh), and can't be mapped to a controller (UGGH!). It would also be nice for there to be a trim toggle button, that jumps trim to whatever control input you or SAS is using.

For rapid coarse pitch trim adjustments (if you don't normally use flaps on your designs), assign flaps function to a couple of small horizontal surfaces near the tail. Attach the surfaces so that they are angled upward to a point where the "medium" flap position makes them level with the wing. Then, you can use the "raise flaps" action group to rapidly add a big notch or two of nose-up trim.

[LethalDose]

Just wanted to say I love FAR. It was painful learning to fly again, but I'm glad I did it.

I was flying some spaceplanes with FAR window open to watch for warnings and my mach number when I had an idea as I was going supersonic. Occassionally when an aircraft goes supersonic, it will create a visible cone of rapidly condensed water vapor with it's shockwave:

Has anyone thought to use the particle emitters in KSP to simulate this?

[grievous056]

Hey, I've been having a problem with FAR causing the center of lift icon to no longer work in the SPH. When FAR is installed, the center of lift icon just stays stuck to the floor instead of going onto the plane like it's supposed to.

[AndreyATGB]

Did you try the update CoL button in the FAR menu? What wings do that? Do you have the latest ModuleManager (and only one)?

[ferram4]

@grievous056: Then you have installed it incorrectly or you have another mod preventing FAR from loading properly. With FAR installed everything should move the CoL around and place it somewhere on your vehicle. You'll need to provide a complete list of all the mods you're using, their versions, a copy of the entire output_log.txt from KSP_Data after causing the issue during a session, and what parts you were using when you caused the issue. If you do not provide all of those, I will not be able to figure out what is wrong and won't be able to help you.

[technoDaleks]

Hello!

Was the information display for drag changed? By this, I mean that in the past I could right click on a part and see how much drag it was causing. has this been bundled into the general information display?

[Drew Kerman]

how do you factor in weight to your design? I'm not talking about a shifting CoM I'm talking overall weight of the entire craft and whether it's just too heavy to get off the ground. Is this factored into the static analysis?

Anybody? I think I loaded up way too much fuel into my aircraft for it to leave the ground. It almost reached mach 0.25 when it ran off the runway and experienced minor stalling. In my derivatives window the pitch up goes green at like mach 0.265 or something like that. So if FAR is modeling the weight of my aircraft properly then I just wasn't going fast enough?

Was the information display for drag changed? By this, I mean that in the past I could right click on a part and see how much drag it was causing. has this been bundled into the general information display?

You have to turn this on now in the FAR options menu from the button in the Space Center view toolbar

[NathanKell]

You can estimate wing loading by using your max takeoff weight and FAR's wing area (on the stability calcs tab) * 0.75 or so (since in real life wing area doesn't include the tail, but in FAR it does). You can then check vs. various real airplanes' wing area and weight, and/or wing loading. The F-15, for example, has 0.358t / m^2 loading.

[Drew Kerman]

You can estimate wing loading by using your max takeoff weight...

Actually the max takeoff weight is what I'm trying to figure out

[K3-Chris]

MJ/KER?

10 characters

[Hodo]

MJ/KER?

10 characters

Yes both work with FAR. MJ autopilot doesnt do well with planes in FAR but rockets are fine.

[Drew Kerman]

actually I think maybe he was telling me to use one or the other to get my takeoff weight. If so, I still don't get how. I get TWR as applied to rockets, but not when applied to lifting surfaces

[Hodo]

actually I think maybe he was telling me to use one or the other to get my takeoff weight. If so, I still don't get how. I get TWR as applied to rockets, but not when applied to lifting surfaces

I just kind of eyeball it myself for lifting surfaces. If the aircraft is massive I put larger wings on it or design it with a lifting body design.

[Aedile]

Anybody? I think I loaded up way too much fuel into my aircraft for it to leave the ground. It almost reached mach 0.25 when it ran off the runway and experienced minor stalling. In my derivatives window the pitch up goes green at like mach 0.265 or something like that. So if FAR is modeling the weight of my aircraft properly then I just wasn't going fast enough?

You have to turn this on now in the FAR options menu from the button in the Space Center view toolbar

The actual taking off can be problematic for many reasons, there are lots of planes which might fly well, but have issue taking off, generally the problem being not enough control surfaces to pivot you around the gear. Try running simulation with deflected surfaces, and see how the lift looks.

Once you reach the end of the runway, what happens? Gear placement is rather essential.

Also note where your center of thrust is, if it's higher than com, it will push your nose down.

Gear placement and center of trust is something I'm pretty sure you can't see from the simulation.

Apart from that, I think you can have a look in the stability derivatives. Pretty sure there was some coefficient showing how well you'll pitch or climb

Edited June 25, 2014 by Aedile

[AdmiralTigerclaw]

Might help to see a picture of Gaiiden's plane.

Can't get the nose up can be any number of things. Control Surfaces too small or not enough deflection, aft gear too far behind CoM... Or it could even be the surfaces are actually miss-assigned and causing poor performance.

Imagine say, if the main wing control surfaces are a little behind CoM, and pitch option for them wasn't disabled. According to KSP's flight model, pulling back on the stick would attempt to make these surfaces deflect upwards to try and force the aft section of the plane to drop as you bring the nose up. This would negate some or all of the lift of the wing, pushing it down while trying to tilt the plane back. If the control surface has enough deflection, this could even generate a stall. Either from the disruption of airflow over the main wings, or even by masking airflow over aft control surfaces behind them, which in full flight could lead to a loss of control.

But we really need to see the plane to know how it's configured.

All things considered, if the problem were just not going fast enough for takeoff at reasonable speeds below 250 knots, a redesign from the ground up should be considered. There's a point where you just have to admit that certain designs are just not good. I've got a P-3 Orion that takes off in the 100 knot range and practically floats, an SR-71 that once I hardened it with a few struts along the length and fixed the chines flies almost exactly like the real thing (right down to the tendency to depart from stable flight and perform backflips if it exceeds critical AoA). But it would be wise to make sure it's not something silly like underestimating the importance of which control surfaces are allowed to assist with which control moments.

[Woodstar]

OK I know nothing about writing configs so I was wondering if someone here or possibly ferram could write a FAR.cfg for the new KSO Phase III Super25 EWBCL? nothing I put in the cargo bay is shielded causing problems. I know someone wrote one for the first KSO, like I said I know squat about it.

[Aedile]

actually I think maybe he was telling me to use one or the other to get my takeoff weight. If so, I still don't get how. I get TWR as applied to rockets, but not when applied to lifting surfaces

Well, generally 3-10 square meters per ton should be enough. Your weight is around 10kN per ton, so your lift should counteract this. Once you pitch your plane, some of your trust will go to vertical speed as well. Your lift is proportional to CL, atmospheric density, wing area and the square of the speed.

The thing is, in KSP wings have no lift at 0 AoA , so to take off the runway, you should somehow change the wings angle. In addition, you will use some of the engine for vertical climb. So either put your gear so that your plane is a bit nose up, or make sure your control surfaces can pitch it enough. Note that the surface distance to the CoM matters a lot. (gimbals and reaction wheels also help, though it's better not to rely on them much)

The drag is mostly relevant to how much thrust your plane needs, you can easily build a plane which will fly fine with 0.5 TWR.

Edited June 25, 2014 by Aedile

[Drew Kerman]

Thanks for the input guys, I will do another design pass and if it still doesn't work will post a pic. As was said it may just be the design simply won't work and needs to be scrapped

[Woodstar]

OK I know nothing about writing configs so I was wondering if someone here or possibly ferram could write a FAR.cfg for the new KSO Phase III Super25 EWBCL? nothing I put in the cargo bay is shielded causing problems. I know someone wrote one for the first KSO, like I said I know squat about it.

So can anyone that is config savvy help me out?

[Duxwing]

Dear Ferram,

How can I reduce the Mach Tuck of my 3-Kerbal LKO transport?

Relevant Mods:

-Procedural Dynamics

-Advanced Jet Engine

-Duxwing

[Drew Kerman]

Ok I think I'm close. Looking for some final advice. Please keep in mind this is under a career game with financing, so I haven't researched a lot of parts to use and haven't put much science towards aerodynamics in the tech tree. So I have limitations and this is the best I think I can do with what I have to get a hybrid aircraft. The idea is for it to power climb on the jet engines and glide down slowly with the electric propellers, doing this a few times until fuel runs low and it needs to return. Honestly don't know if the concept is viable but I'm trying to find out and learn a bit more about plane building in the process.

I just flew a test flight that had my nose lift and my rear end hit the ground and blew up a few seconds into my takeoff roll no doubt because my gear was too close to the CoM. I noticed when I 2x physical warp the plane almost tips over backwards. Would it be a good guide to be able to 3x or 4x physical warp without the aircraft tipping back on its rear as a good indication of where to place the gear relative to the CoM? I also think the propeller thrust being under the CoM helped the nose come up and I should instead takeoff on jet power alone at first rather than move the gear too far back to make it harder to lift off. I could also angle the canard wings down a bit.

The test was flown with only the main fuselage/nose cone and engine fuselage/nose cones filled with fuel.

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[Hodo]

I would swap one part out on that craft. The tail, I would put a raised tail section or any type of tapered tail so you reduce your tail strike chance.

[jrandom]

I'd also recommend maybe moving the center of lift just a liiiittle bit back from the CoM (unless you absolutely need it there for supersonic flight). That will make the pitch a bit less sensitive and you can fly a gentler takeoff.

[Drew Kerman]

I would swap one part out on that craft. The tail, I would put a raised tail section or any type of tapered tail so you reduce your tail strike chance.

May not be an option with the parts I have available, but I will look into it that's a good idea. Was thinking of a small tail-wheel perhaps too so the nose could still pitch up but the rear won't strike

I'd also recommend maybe moving the center of lift just a liiiittle bit back from the CoM (unless you absolutely need it there for supersonic flight). That will make the pitch a bit less sensitive and you can fly a gentler takeoff.

Yea I'm trying to decide what is good. Is there any good rule of thumb? Like the CoM ball resting fully on the forward axis indicator of the CoL? Currently where it is you can see the axis sticking out, and I'm thinking of moving the CoM forward just enough to cover it up