Talk:Aeris 4A

Improved canards

Hi, I tried to create a screenshot with all modifications including the Advanced Canards, but I was barely able to lift up, and unable to maintain ascend. Reverted the canards and got back to the AV-R8 Winglets I did it in the first try. — xZise [talk] 14:30, 16 November 2013 (CST)

There will be an element of personal taste over what should be considered improved handling, but I find the Advanced Canards work well for me, with the plane almost wanting to leap off the runway at 80–100m/s, with just a quick touch of pitch up control. When I go much further with my modifications, to my increased fuel capacity version, the change to the Advanced Canards becomes pretty much essential. My canards are attached at their default rotation, unlike the supplied tilted/inclined attachment of the AV-R8s.

The increased lift provided by them does mean that you need to move the main wings back fairly significantly. I moved my entire tank+engine+wing subassembly back, such that the FL-T400s are approx level with the Mk1 Fuselage. Both of my large and small wing sections are in the same relative position to the FL-T400s. I feel that the handling is much more like the high power to weight ratio, slightly unstable, delta-wing fighter-type aircraft that's visually represented by the Aeris 4. Here's the list of changes in my design shown in the screenshot:

Murph's Aeris 4B

• Rocket engine changed to the Aerospike.
• Inline Advanced Stabilized removed.
• Nose wheel relocated under the docking port.
• 1k battery added in front of the RCS tank.
• Single flat solar panel on top of RCS tank.
• Engine+wing subassembly moved significantly backwards.
• Nose and tail canards swapped in.
• Struts from the slight bulge in the cockpit where the canards are attached, back to the front of the wings.

My CoL is very slightly forward of my CoM when fully loaded with fuel, which I think helps just a little once the tanks are closer to empty, on re-entry, approach, and landing.

It does require a fairly careful use of the controls, as it can quite easily go into a spin if you allow the nose to stray too far from the prograde vector. That is quite realistic for the aircraft style, in my opinion. With care and skill, however, it's both very responsive, and very controllable. It is stable on both SAS and MechJeb autopilot, as long as you are stable and close to prograde when you engage the autopilot.

--Murph (talk) 22:20, 16 November 2013 (CST)

D'Oh I placed the canards facing the wrong way! I tested it the canards facing forward and it works great. I'll remove the note. — xZise [talk] 16:24, 18 November 2013 (CST)

Excellent, glad to hear it!  :-) I'm also interested to see that you opted for the nose canards a little further back than me. I think I quite like mine attached to the cockpit section, but it's another thing to play around with, and something which is very much into the realm of personal preference/taste. --Murph (talk) 23:27, 18 November 2013 (CST)

Yeah I tried to move the CoL indicator further back. I also changed the order so that the RCS tank and battery is in front of the docking port. This makes it a bit heavier in the front (I think ^^) moving the CoM a bit to the front. I don't know if this helped, but both modified versions of mine were flying pretty well. And your naming is nice (Aeris 4B). — xZise [talk] 03:59, 19 November 2013 (CST)

Fixing the broken IntakeAir mechanic

So, the more I've been playing around with the Aeris 4, trying to both perfect it and master both the design and piloting of spaceplanes, the more I've become convinced that the current default IntakeAir behaviour is basically badly broken. Specifically, the guaranteed asymmetric flameouts happening when there's still significant thrust being generated by the engine that doesn't flameout. That seems highly unrealistic to me, and happens at a relatively low altitude for engines equipped with one large ram intake and two smaller side-mounted ram intakes.

After some digging around on the net and lots more experimentation, I've discovered that changing the resource configuration for IntakeAir in GameData/Squad/Resources/ResourcesGeneric.cfg from flowMode = ALL_VESSEL to flowMode = STACK_PRIORITY_SEARCH results in what I consider to be far more realistic and satisfactory behaviour. With that change, I've removed the 4 small intakes from my Aeris 4, leaving it with just the 2 main large intakes (one per engine), and get a result which could be considered relatively comparable to the real SR-71. I also changed the 3 rear tanks to be a FL-T400 in the middle, and a Mk 1 jet tank on each wing, reflecting greater need for jet fuel, reduced need for rocket fuel.

Why the SR-71 for comparison? Well, there's not many real examples to choose from which are fighter-style/size, Mach 3+, and cruise comfortably above 20,000m. Those characteristics more or less match the Aeris 4 (other than the max comfortable cruise altitude).

Power below 20,000m is not changed all that much (subjectively). From 20–25,000m, it degrades steadily, but can still comfortably cruise at 25,000m on jets alone (that's roughly the same as the SR-71). Above 25,000m, power degrades quickly, to eventual symmetric flameout at approx. 32,000m. 32,000m flameout seems plausible for what might be achieved by the SR-71 (guessing here, as I didn't find any concrete figures on absolute max altitude for it, just the 25,000m service altitude), had it been developed into a spaceplane, rather than almost-space plane.

Now, guaranteed symmetric flameout might not be entirely realistic, but it seems much closer to reality than sudden asymmetric flameout with the remaining engine producing significant thrust, and at a point where both engines were moments before producing good thrust happily. It's also possible that there should be some other changes to intakes and jet engines with this change, to keep everything reasonably balanced. In some ways, this change does make spaceplanes "easier", but that was absolutely not my motivation for changing the config in this way.

This is kinda a bit beyond the scope of this article, changing the fundamental mechanics for jet intakes game-wide, so only mentioning it on the talk page for now. It's just another step in my quest to perfect the Aeris 4.

--Murph (talk) 18:01, 22 November 2013 (CST)

Now you could incorporate your findings in Intake air. Although I'm not sure how often symmetric compared to asymmetric flameouts would happen in reality. I mean to have a symmetric flameout both engines must fail at the same time, but is there a guarantee that both engines are getting the same amount of air (wind?). As soon as one engine does operate only slightly longer it induce pretty much torque. — xZise [talk] 04:38, 23 November 2013 (CST)