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

[DaniWesNL]

The S2 plane was around 100 tons. The MK2 was around 40 tons. Both tear apart as soon as I pitch up slightly after taking off.

I would expect the weels to break off if you land too hard, the engines breaking off with too much drag, or maybe the entire fuselage ripping from the wings. But the individual parts of the fuselage detaching from each other as if I've used separators still seems strange.

[Wanderfound]

The S2 plane was around 100 tons. The MK2 was around 40 tons. Both tear apart as soon as I pitch up slightly after taking off.

I would expect the weels to break off if you land too hard, the engines breaking off with too much drag, or maybe the entire fuselage ripping from the wings. But the individual parts of the fuselage detaching from each other as if I've used separators still seems strange.

It has been known to happen...

[starikki]

The S2 plane was around 100 tons. The MK2 was around 40 tons. Both tear apart as soon as I pitch up slightly after taking off.

I would expect the weels to break off if you land too hard, the engines breaking off with too much drag, or maybe the entire fuselage ripping from the wings. But the individual parts of the fuselage detaching from each other as if I've used separators still seems strange.

and what EAS are you flying on?

Edited January 22, 2015 by starikki

[taniwha]

DaniWesNL: just how fast are you going when you take off? If it's much over 70m/s, your plane has insufficient wing, you have insufficient pitch authority (to lift the nose), your rear wheels are too far behind your CoM, or any combination of the above. My little plane takes off at around 40m/s, with flaps set to 0. Mind you, it can achieve level flight at 26km doing Mach 0.9-ish.

[HoneyFox]

Yes to all of the above.

I was more wondering about the practicality of the leading edge slat controls; the AoA thing is just the AoA setting working as it should.

About slat in FAR or in RL?

[Goddess Bhavani]

From mucking about with FAR over the past several months, leading edge control surfaces can have a very large impact on lift and maneuverability. Just a few degrees of fixed trim or pitch angle can make an unflyable design workable.

[DaniWesNL]

DaniWesNL: just how fast are you going when you take off? If it's much over 70m/s, your plane has insufficient wing, you have insufficient pitch authority (to lift the nose), your rear wheels are too far behind your CoM, or any combination of the above. My little plane takes off at around 40m/s, with flaps set to 0. Mind you, it can achieve level flight at 26km doing Mach 0.9-ish.

I usually have to go faster than 150 m/s to be able to take off. Mind you my aim is to make an SSTO with enough delta-V to achieve a decent orbit and have some fuel left for course corrections.

My pitch authority and rear wheel placement are fine, I checked those with the very detailed guide.

However the problem lies probably in the fact my aircraft has not enough lift, either a wings or weight issue or maybe both. I am mostly using wings that don't appear to have any lift rating in the description (non stock ones). But when I check for the CoL, it doesn't have an arrow. Does that have anything to do with this?

Also since I found my aircrafts seem to have lift issues, I simply add more thrust, though that's probably not the right way to go. Maybe I am too much of a rocket engineer to be an aircraft engineer

Edited January 22, 2015 by DaniWesNL
spelling

[boborene]

Very interesting mod. Is any way to make flight pressure effects to be configurable? I mean all these FAR effect to be 50% to learn easier to control flight here?

[Crzyrndm]

However the problem lies probably in the fact my aircraft has not enough lift, either a wings or weight issue or maybe both. I am mostly using wings that don't appear to have any lift rating in the description (non stock ones). But when I check for the CoL, it doesn't have an arrow. Does that have anything to do with this?

Also since I found my aircrafts seem to have lift issues, I simply add more thrust, though that's probably not the right way to go. Maybe I am too much of a rocket engineer to be an aircraft engineer

FAR zeroes out the stock "lift" values, hence surfaces that don't have a lift rating. It also removes the arrow from the CoP(CoL) for reasons I can't remember at the moment.

150m/s takeoff's aren't particularly difficult, you just have to be rather light on the controls in the lower atmosphere (first 3-5km in particular). You could add some flaps to lower takeoff speed and you should be throttling back once you get into the air to keep the dynamic pressure in a manageable range.

[BudgetHedgehog]

It also removes the arrow from the CoP(CoL) for reasons I can't remember at the moment.

Ferram explained it very well on reddit the other day:

The arrow isn't useful, because the Center of Lift (or Center of Pressure, which is what FAR and NEAR turn it into, accounting for drag as well) doesn't have a direction associated with it. It's just a point in space. The vector is ultimately simply confusing to players, especially when they try to use it in the VAB and scream, "why is my rocket making lift even though it's symmetrical?!"

To explain this a little better: let's add a vector to the CoM. Why would you add that? What would it represent? How would it not be confusing, considering the CoM is just a point in space?

[tetryds]

Btw, when having issues with an aircraft please attach pictures to your post, more pics as inflight, showing AoA sweep and stability derivates also help.

It's way easier to help that way.

For instance it's simple to notice a plane needs bigger wings, or more tail.

Have you doubled your tail today?

[taniwha]

DaniWesNL: yeah, it's difficult. I have yet to get a plane into space with recent FAR.

[NathanKell]

Note that wing breakage is based on wing *loading*, so 6G is survivable if you have low wing loading, but not if high. That is, FAR checks the m^2 wing area divided the weight (i.e. mass * G loading), and if that's too small, the wings break.

150m/s is ~340mph. Think about how fast that is for a takeoff speed.

[Wanderfound]

About slat in FAR or in RL?

RL; I know it works in FAR.

[Rebelgamer]

I had one that wouldn't rotate until it got above 175m/s, but it was more like a cruise missile than a plane...and it is surprising how many people forget just how big a difference in speed there is between m/s and mph/kph/knots. Users look at it and go, "it's only 120, that's not that fast".

[Goddess Bhavani]

For those having issues with very high takeoff speeds, try the following:

Designate some forward-placed control surface or canard as a "flap". I like using a leading edge control surface as a flap to increase the angle of incidence of the combined wing, easing the task of rotation or low speed approach.

Another factor to consider is how the craft sits on the ground. If its nose low then at takeoff velocity the wing planform is generating a lot of downforce instead of lift.

I don't have screenshots on this computer (might add them later), but I set the aircraft's rear wheels to be slightly higher up on the fuselage so the aircraft when sitting on the ground, has a nose-up attitude. This allows me to have reliable rotation speeds at realistic values like 120 - 160 kts (60-80m/s approximately).

Real aircraft landing gear also design their landing gear to have the optimal takeoff attitude.

[Crzyrndm]

I had one that wouldn't rotate until it got above 175m/s, but it was more like a cruise missile than a plane...and it is surprising how many people forget just how big a difference in speed there is between m/s and mph/kph/knots. Users look at it and go, "it's only 120, that's not that fast".

Not really that surprising. Most people don't use m/s much (if at all) and have no references against their "everyday" units (kph || mph). On top of that KSP lacks any feeling of speed (open road speed is less than 30 m/s, but would you be able to pick that in game?).

So no, I wouldn't say it's surprising.

[blowfish]

Another factor is wheel placement - the closer the rear wheels are to the CoM, the less pitch authority you need to lift up the nose.

[NathanKell]

Ideally the plane should balance on the rear wheels alone, with just the *slightest* tilt forward, yeah. If your wheels are further back than, say, one CoM sphere's distance behind the CoM sphere (for larger planes, less for smaller ones) then they are too far back.

[taniwha]

Yeah, my planes rock back when KSP drops them on the tarmac, and then gently settle on their nose wheel.

[Van Disaster]

I tend to use kts ( knots ) for flight, it's intuitive given I sailed a lot. Also it's approximately double m/s, so that's easy enough. My large spaceplanes tend to take off at crazy speeds - but they're compromised hypersonic craft, extremely heavy and rather long so their rear gear is well back to prevent tailstrikes, you have to expect & work around that - part of the compromise is also in the available wing choices. I'll be seeing what I can do with the B9 pwings now they're also tanks, might reduce the length a little.

What sort of angle is a Mach 5-6 shock cone? I went from this B9 pw test design ( more designed to test a bunch of newly released features than wing shape ):

to this:

with no noticeable reduction in hypersonic drag or from obviously not terribly accurate observation of cD. I'd have thought maybe the ends of the canards would be outside the cone, but not the main span wingtips.

[Wanderfound]

Yeah, my planes rock back when KSP drops them on the tarmac, and then gently settle on their nose wheel.

You can get away with extreme rearset gear on some designs, however:

Light weight and a hefty amount of pitch authority helps (but, yeah, usually best off with gear adjacent to CoM).

[Van Disaster]

Anything with positive pitch authority ( I dunno the exact proper phrase ) can get away with a lot more, given you're picking the plane up instead of pushing part of it into the runway. That does mean your canards need to provide significant lift though, it's not going to work if they're just there for essentially trim.

[TheXRuler]

Hey Guys i have now finally upgraded my heavily modded KSP to 0.90 from 0.24.2. I had spent quite a few days designing 2 large SSTO's, the larger of which could carry an entire 18m by 2.5m payload weighing up to 35 tons (I had FAR installed back then too).

Now after upgrading, even using the Lance Mk Ic, my largest SSTO i am unable to put a measely 5 tons into orbit. So now i am wondering, where there any major changes in FAR's aerodynamics system that will require me to do a complete redesign?

Here are three screenshots from different angles, and the actual craft file (although you would need TAC life support and B9-Aerospace to be able to load it)

Screenshots

http://s1377.photobucket.com/user/thexruler/media/2015-01-23_00005_zpsxgvenf0p.jpg.html?sort=3&o=0

http://s1377.photobucket.com/user/thexruler/media/2015-01-23_00003_zpsj83eav0p.jpg.html?sort=3&o=1

http://s1377.photobucket.com/user/thexruler/media/2015-01-23_00004_zpshx6t4nxe.jpg.html?sort=3&o=2

Craft File

https://www.dropbox.com/sh/767s5y3trqao4wq/AAD1VSGS7qSE7zJm4yeIBWTda?dl=0

Edited January 23, 2015 by TheXRuler
Broken Links

[Van Disaster]

@TheXRuler: What version of FAR were you using in 0.24.2? also exactly why can't you put your payload into orbit?

There's been several fairly large changes in the last few major versions ( although I've missed some so I don't know exactly what all of them are ) including the current one which has considerably more high altitude drag. Personally I'm still putting huge payloads into orbit with something that looks like a glider so that isn't necessarily a showstopper, but it does take a bit more fuel.

Edited January 23, 2015 by Van Disaster