Official FAR Craft Repository

[capi3101]

Hi,

I've created the following craft for FAR and am having trouble landing it. I believe my problem largely lies with the high AoA requirement at lower velocities I think, as it basically falls like a rock below 150 m/s; which is rather high to land at for someone who's never been good at landing in the first place. Having the craft fall through the landscape glitch at high velocities doesn't help the landing experience, either :/.

http://imgbox.com/RMw8ZYYZ

http://imgbox.com/Dh8QAzQr

http://imgbox.com/7BNTkM2e

http://imgbox.com/dkh3F8PK

http://imgbox.com/cWK0cK7r

Other than that, so long as you don't exceed structural tolerances, it flies quite well. Ironically, it even flies well in stock as well except for taking off.

Would anyone have suggestions on how to improve its handling at low velocities? Or am I just a terrible pilot?

Ideally it would retain it's overall shape and ability to reach orbit; I am able to reach orbit if I remove one of the rocket fuel tanks, though it's much more difficult.

Thanks

You've got some pretty significant wing loading going on there - good for high speed flight, bad for pretty much everything else. What's the takeoff mass of the plane, and what is the FAR analysis telling you about your wing area? How about the AoA at 0km and Mach 0.35?

An SPH screenie with your CoM and trans-sonic curves visible wouldn't go amiss in helping to diagnose any potential problems.

I might suggest swapping out that Terrier for something with moar oomph (an Aerospike would do well if you've got access, but even a Thud or two would do well - something that gives you more thrust). Just a thought.

EDIT: More craptastic advice from the nugget. If you go to try adding more wing, start with a strake, maybe a Wing Connector C or D aft, and then put your Tail Fin ailerons there; you'd wind up with a cranked arrow wing, which shouldn't affect the overall shape too terrible much but will give you some more wing. Start with that, and expand it out more if it's still not enough. Myself, if I was designing the plane, I'd take its mass and divide it by the wing area; in my experience, you're generally "good enough" if the result is between 0.3 and 0.5, favoring the low end of that range.

Edited June 24, 2015 by capi3101

[Tipped]

You've got some pretty significant wing loading going on there - good for high speed flight, bad for pretty much everything else. What's the takeoff mass of the plane, and what is the FAR analysis telling you about your wing area? How about the AoA at 0km and Mach 0.35?

An SPH screenie with your CoM and trans-sonic curves visible wouldn't go amiss in helping to diagnose any potential problems.

I might suggest swapping out that Terrier for something with moar oomph (an Aerospike would do well if you've got access, but even a Thud or two would do well - something that gives you more thrust). Just a thought.

EDIT: More craptastic advice from the nugget. If you go to try adding more wing, start with a strake, maybe a Wing Connector C or D aft, and then put your Tail Fin ailerons there; you'd wind up with a cranked arrow wing, which shouldn't affect the overall shape too terrible much but will give you some more wing. Start with that, and expand it out more if it's still not enough. Myself, if I was designing the plane, I'd take its mass and divide it by the wing area; in my experience, you're generally "good enough" if the result is between 0.3 and 0.5, favoring the low end of that range.

Thanks for the advice. I ended up removing one of the rocket fuel tanks and vertically doubling up the "tail fin" aileron at the end of the plane. It still falls like a rock at speeds too high for my computer to let me safely land it anywhere, but at least it works on the runways now. Though getting it on the runway early enough that it can slow down can be a challenge, but that's part of the fun! Overall I think it's the best spaceplane I've built in terms of stability in FAR; certainly the best since nuFAR.

http://imgbox.com/FZuKHuTC

http://imgbox.com/FFMBlEP5

Another question: What is the reference area of a plane? I assumed it was the surface area of the wings; but it increases and decreases dramatically whenever I add new parts. Or is FAR just removing a lot more area from what it considers wings than I would expect? If so, is there a simple heuristic I can use to guess at how it will change by adding a new part?

[Nansuchao]

Hi, I'm a long time user of Far. Now, in 1.04, it seems I'm unable to enter the Eve atmosphere. It's difficult with rockets (unless you fire your engines) and almost impossible with spaceplanes.

I tried with a SSTO that was able to land on Eve in 1.02, but now, also using a very shallow trajectory, touching the atmosphere just a bit to slow down and going out, I'm still finding terrible heating issues.

Any suggestion? ( I added radiators to my ships, same result)

[FourGreenFields]

Another question: What is the reference area of a plane? I assumed it was the surface area of the wings; but it increases and decreases dramatically whenever I add new parts. Or is FAR just removing a lot more area from what it considers wings than I would expect? If so, is there a simple heuristic I can use to guess at how it will change by adding a new part?

If I am not mistaken (I may very well be) it's more like the "lifting area". The fuselage etc. also adds some lift. However, no idea how it's calculated, or if I guessed correctly.

Hi, I'm a long time user of Far. Now, in 1.04, it seems I'm unable to enter the Eve atmosphere. It's difficult with rockets (unless you fire your engines) and almost impossible with spaceplanes.

I tried with a SSTO that was able to land on Eve in 1.02, but now, also using a very shallow trajectory, touching the atmosphere just a bit to slow down and going out, I'm still finding terrible heating issues.

Any suggestion? ( I added radiators to my ships, same result)

Airbrakes (the stock ones). Loads of them. At least it works for my SSTOs if I want to reenter.

[Nansuchao]

I put 4 of them, but usually I have an high Angle Of Attack during reentry (with Monoprop help), so Airbrakes doesn't works. Btw, I have them deployed, nothing better... I loose my cockpit...

[FourGreenFields]

I put 4 of them, but usually I have an high Angle Of Attack during reentry (with Monoprop help), so Airbrakes doesn't works. Btw, I have them deployed, nothing better... I loose my cockpit...

AfaIk airbrakes still use stock model -> they work.

And 4 of them doesn't sound like much. How heavy is your SSTO?

[eddiew]

Thanks for the advice. I ended up removing one of the rocket fuel tanks and vertically doubling up the "tail fin" aileron at the end of the plane. It still falls like a rock at speeds too high for my computer to let me safely land it anywhere, but at least it works on the runways now.

It's pretty tiny - maybe worth "cheating" with a couple of radial parachutes on the top? One chute per 2.5t of dry mass usually works out well, and landing gear has a very high impact tolerance too.

Also I might be wrong, but I'm pretty sure you don't need those radiators, or more than a couple of solar panels - all of which are drag sources ^^;

[tetryds]

Drift:

[Nansuchao]

It's a heavy MK3 SSTO, powered by a 2.5 meter Fusion Reactor by Interstellar Extended plus a 3.750 m Vista Engine.

In the past, with FAR, I was able to land safely a spaceplanes similar to the Draco (Scott Manley's Interstellar Quest). Mk3 structural parts are lighter than S2 Wide Body B9 Aerospace parts and I have less wings, to have less drag with the nuFar.

[tetryds]

@Nansuchao: It's a lot easier if you post some pictures of it

[Nansuchao]

You're right... Give me some minutes.

EDIT: Here's some pictures

Inside the Cargo bays, there are a Fusion reactor 2.5M plus a Htermal Generator 2.5 m, Life Support and a simple Monoprop lander for Gilly.

In the past, I was able to land an almost similar spaceplanes with a Lab inside the Cargo bay.

Edited June 26, 2015 by Nansuchao

[FourGreenFields]

I wouldn't realy call that heavy. But I'd use more than 4 airbrakes nonetheless.

[tetryds]

I heavily recommend NEVER placing anything on the top of your wings.

It's a terrible practice and when more complex wing interactions get added it's going to kill all of your designs.

This is for everybody.

[Nansuchao]

I thought about that, but I needed those radiators, and I haven't other place for them...

[blowfish]

I thought about that, but I needed those radiators, and I haven't other place for them...

Generally, anywhere but the top surface of the wing is preferable. There seems to be a fair bit of space along the sides of the fuselage...

[Nansuchao]

I'll try it. Thanks to everyone for the help.

[gilflo]

Hello guys

I did not use 1.0.4, just 1.0.2 for the time being cause i did not have any time to play last 2 weeks, but about airbrakes and re entry, i think airbrakes must be situated at COG or at equal distance before and behind COG and they also must be not only on top of fuselage or wings but also symmetrically below. If you place them only on top you would only destroy lift and they will act at liftdumpers that you use on landing to help the plane being stuck on the ground. Placed only on top, in the air they will destroy lift and give a pitch momentum when you need to be as stable as possible on re entry. If they are symmetrical on pitch axe it's better. You could also placed them laterally on fuselage.

Then about my re entries, i noticed they have been always easier and flyable with no spin and no flip every times i use a very flat angle , i mean entry trajectory begins more than 120 degrees of longitude before landing spot.

[Nansuchao]

Well, I put those Airbrakes there just for this reason, to have an easier pitch momentum. Usually I reenter (or enter in this case) with an high AOA to loose speed, then when the aerodynamic begin to make the ship unstable in that position, I toggle the Airbrakes and begin to make S turns to slow down. So, the only moment I use Airbrakes is near the landing site, to bleed excess velocity if needed.

Are you suggesting to put more Airbrakes and reenter in a stable flight instead that Shuttle's way?

[Wanderfound]

Are you suggesting to put more Airbrakes and reenter in a stable flight instead that Shuttle's way?

No and yes.

You don't need more airbrakes; a single pair is plenty, even for a large Mk3 ship. And while a Shuttle-style high-AoA approach works in KSP, it usually isn't necessary; you're coming in at 1/3rd of the velocity that the Shuttle had to deal with. It's also worth remembering that the Shuttle was not aerodynamically stable during reentry; the OMS thrusters were necessary to maintain that extreme AoA.

Some reentry demonstrations:

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(first half showing an easy reentry, second half demonstrating how to recover from a bad reentry)

And a Mk3 example:

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And a demonstration of just how powerful airbrakes are:

Javascript is disabled. View full album

Edited June 28, 2015 by Wanderfound

[FourGreenFields]

Hello guys

I did not use 1.0.4, just 1.0.2 for the time being cause i did not have any time to play last 2 weeks, but about airbrakes and re entry, i think airbrakes must be situated at COG or at equal distance before and behind COG

Actually, they don't have to. I often use airbrakes on SSTOs to keep them stable at the high altitudes and speeds they encounter only during reentry, which means I put them all on the tail.

(Btw, I think the lift reducing air brakes you mean are called spoilers)

[blowfish]

It's generally a bad idea to place airbrakes in front of the CoM because the drag will reduce stability. If you're using them during flight, then yes, it's a good idea to place them symmetrically top to bottom so that they do not induce a pitch moment when activated.

[Nansuchao]

Usually not during flight, just sometimes during the approach, to bleed speed and keep the nose up enough. I have no problem landing, just entering Eve atmosphere.

[gilflo]

http://www.airliners.net/aviation-forums/tech_ops/read.main/223154/

The best place for airbrakes is laterally around COM, like on the WANDERFOUND SSTO, or laterally at the tail like F28 or BAE 146 liners.

If you want to destroy lift at landing to be sure your aircraft will not bounce on bumpy landing or on bumpy surface, just use spoilers and put a pair of speedbrakes on top of wings or fuselage.

[gary85]

How you make vista engine work with 2.5m reactor and only 1 generator?

[Nansuchao]

Using the right generator, that now isn't the same as the older Interstellar.

In Interstellar Extended now there are Particle Generators and Thermal Converters. With the Thermal Converter you can have way more than the 2.5 GW needed for Vista just with a single 2.5 m Fusion Reactor.