Is it just me, or are space-planes insanely hard?

[Jarin]

5 hours ago, AeroGav said:

Surfaces at the front not having any incidence, but the main wing having it, is bad.   It is effectively a nose down  trim that makes the CoL marker in VAB look further forward than it really is.    When your AoA gets large , the main wing will stall while your canards are still unstalled and making lift.  Your craft will swap ends or get into an unrecoverable deep stall.

... huh, so that's why my last spaceplane got all flip-happy on re-entry. 

[MrBonk]

11 hours ago, AeroGav said:

Then I'll also shout out to CorrectCoL.  The blue indicator only takes account of parts with a lift rating, this one makes it more accurate by computing the effects of aero forces from non wing parts.

If you only  install two mods in KSP, get these two.  

Looks like I'm well on the way to a modded KSP install then.....'once you start' and all that

 

[Wanderfound]

12 hours ago, Jarin said:

... huh, so that's why my last spaceplane got all flip-happy on re-entry. 

It's a good tip if you're having trouble, but it's not compulsory.

If you've got sufficient tailplane and appropriate weight distribution, it shouldn't flip even if you do have a bit less incidence on the canards than the wings. Most of mine are done with inclined wings but flat tailplanes and canards.

6 hours ago, MrBonk said:

Looks like I'm well on the way to a modded KSP install then.....'once you start' and all that

 

RCS Build Aid, Kerbal Pilot Indicators, Kerbal Alarm Clock, Kerbal Engineer Redux.

[Jarin]

1 hour ago, Wanderfound said:

If you've got sufficient tailplane and appropriate weight distribution, it shouldn't flip even if you do have a bit less incidence on the canards than the wings. Most of mine are done with inclined wings but flat tailplanes and canards.

I've mostly just moved away from Canards entirely since they just seem to lead to my aircraft being less stable in general. I suppose that's why they're less common in reality as well, aside from craft with computer-assisted stability (which SAS really... isn't). 

Computer-assisted stability is AA, which can make just about any monstrosity fly nicely. 

[AeroGav]

2 hours ago, Wanderfound said:

f you've got sufficient tailplane and appropriate weight distribution, it shouldn't flip even if you do have a bit less incidence on the canards than the wings. Most of mine are done with inclined wings but flat tailplanes and canards.

Flat tailplanes - more stable, flat canards less stable .  If you have both, they cancel each other out.

 

51 minutes ago, Jarin said:

I've mostly just moved away from Canards entirely since they just seem to lead to my aircraft being less stable in general. I suppose that's why they're less common in reality as well, aside from craft with computer-assisted stability (which SAS really... isn't). 

This debate ran on and on on another thread and got quite heated.   In KSP , with CorrectCoL installed,  I built a simple aircraft and converted it from tail to canard, moving the main wing to make yellow and blue ball only just touch on both versions.   Identical handling, max pitch angle you could pull was the same. Using F12 cheat menu, I  sent them both in on a re-entry trajectory with radial out set on SAS, the reaction wheel fighting to hold the nose up as aerodynamic stability of the two aircraft was trying to pull it back on prograde.  Guess what?  The altitude where the reaction wheel lost that battle and the nose fell below 30 degrees of pitch was the same.

The real reason most aircraft are tailed is because of laminair flow.  You get less drag when air flowing over a surface is non-turbulent, designers go to strenuous efforts to keep airflow over an airframe non-turbulent as long as possible.    This is especially important on the main wing because it's got  a large surface area.   If the air hitting the main wing has already been disturbed by the canards,  expect worse fuel consumption in cruising flight, which is the most important consideration for civil aircraft.

Non FBW canards - Saab Viggen STOL fighter of the 1970s , can operate off roads instead of airbases -

Burt Rutan VariViggen homebuilt

Mine under Ferram Aerospace  - 0.27m³ mach 1 wave drag area and landing speed under 62 m/s

The advantage of canards is that you pitch up by lifting with the canard rather than pushing down with the nose, so total lift can be higher.  Also, in a supersonic aircraft, having the main wing further back means you can make it bigger without getting wave drag penalties.   However, there is a second drawback in that it's harder making a high lift system (flaps).  Flaps already pitch the nose down, but on a canard they'll be even further aft of CG so the pitch down moment is stronger.   You need to install flaps on the canard as well, which is too much complexity and expense for a civil a/c,  or just don't bother with flaps (like the Rutan Variviggen) , or use relaxed stability, which requires FBW.

[MrBonk]

Yes! I've managed to get a hot-rod MK1 ssto design sorted to the point where I can get to the Mun with fuel to spare.  Oddly enough, having a shielded docking port right on the front seems to work quite well, even though it looks ugly as sin. 2 rapiers and a single nuke, and only liquid fuel. I'll upload and post some pix when I get home from work tonight ☺️

 

The cockpit gets a bit warm on ascent, but nothing to really worry about....unless you're sitting in it, I suppose

 

Edited March 28, 2017 by MrBonk
Added pics