Aero and Thermo in 1.0.X

[Claw]

Kerbonauts,

In an effort to collect discussions, feedback, concerns, and accolades about the new aero/thermo system, I'm posting this sticky. Please use it for all 1.0.X aero/thermo discussion and feedback, but not for general aero/thermo questions.

This thread is for voicing your opinion about the system. You can like it, hate it, point out the flaws, and good things with the new system, but I ask that you respect your fellow kerbonauts. Constructive feedback goes a lot further than mere complaints and "abandon ship" posts.

Cheers,

-Claw

[pandaman]

Good idea Claw.

As for me...

I like the new aero and thermal stuff. The f10 thermometers on by default is a good idea, I compare it to having a warning panel on the dashboard. I have heard reports of it being linked to memory leaks, which is certainly feasible, though I haven't encountered any - YET.

The new aero seems fine to me in general, I expect a few balance tweaks as things progress, but don't anticipate big changes.

I like that it encourages what I am told are 'proper' ascent profiles, though I can't judge how realistic it is overall. That needs someone far better qualified than me.

A bit if a re-learning curve, but getting there slowly and enjoying the experience.

[hawk_za]

i peronally love the new aero ..

would make the re-entery heat a bit harser

i would also add radiators and thermal pipes

OH and fix it so there is a reson to use any of the later areials

but other than that you guys are doing a great job keep it up

just my two cents

yours in service

the hawk

[NathanKell]

Aero:

1.0.2 is spot on for blunt objects, but too draggy for pointed ones. This can't be fixed by just changing drag multipliers, the part's own drag coefficient (for each cube face) needs to be modified, say with an exponent in the range of 1-2 (testing will show what's correct). Once that's done, lift can get lowered again (to keep L/D constant for planes). Wing drag can also come down then to keep proportional, although wing drag at 0 alpha should come up (and wing drag at high alpha should come down, in relative terms).

Thermal:

In order to get back a somewhat challenging reentry, the convectionVelocityExponent needs to go up higher than 3, and the convectionFactor go down. However, to keep Eve survivable, the heat shield ablator's hsp needs buffing.

[thereaverofdarkness]

I have been loving it for rocket flight and re-entry, but it seems too easy to make planes go to deadly speeds. SSTO aerojets are going to be a lot tougher now. I haven't upgraded to the later versions of 1.0 yet, but I've been hearing drag was greatly increased.

I do take issue with parachutes. It's great that their partially deployed state has had its drag increased dramatically, but it was increased a bit too dramatically and now it slows the craft almost as much as a fully deployed drogue. Drogues are about worthless now because when they fully deploy, it barely makes a difference. I just use a single small parachute instead, as that seems to function much like a drogue should when used on a larger vessel. Now when you're screaming in at over 2000 m/s above 30km and your parachutes suddenly partial-deploy, they can save your ship from re-entry heating but also cause tremendous g-forces that ought to severely injure or incapacitate the crew. I've watched ships slow from 2500m/s to under 500m/s in under 5 seconds, which means they may be experiencing over 50 Gees of deceleration at some points.

My suggestion for parachutes is cut their partial deployment drag to 1/10th of its current value--I'm not sure how that'll work because I don't know how the calculation is done, but I think if they have about 1/10th of the slowing power it'd be great. Then drogue chutes would be useful, too.

P.S.: A bit off-topic here but I've always been bothered that I can't set my parachutes to deploy at any altitude below 300m unless I set it to 50m. It won't hit the values between because it sticks to the bottom until I slide it all the way to 300m. 50m is too low to have time to slow the ship, but I almost always want 100m or 150m, so I don't have to spend 30+ seconds waiting on 4x time warp for the craft to reach the ground.

Edited May 7, 2015 by thereaverofdarkness

[allmhuran]

Cheers, claw. I'll put just one topic here because I'm sure there'll be others to talk about re-entry, stability, etc. It's not a comment on the physics config as such, but more about the relationship between jet engines and aero.

Jet engines have a bit of an odd curve with speed and altitude. The sound barrier does actually have some "barrier" to it, which is good. But as you gain a bit more speed your acceleration skyrockets. You can easily build a craft that has trouble getting through mach 1, but a few seconds later is starting to overheat due to the speed at which it is flying. Then just a few seconds after that (and just a few thousand meters higher) your engines run out of thrust because they have exceeded their peak power output and because of what seems like two rather significant steps in air density that seem to happen at ~20,000m - 27000m. Put all of this together and it makes aircraft a bit weird to fly. Now, there may not actually be two significant steps in air density in that altitude range, but that's kinda the point.... whatever is going on, it just seems odd.

This impression might be exacerbated by the huge step in technology between the basic jet engines and the turbojets/rapiers. Basic jet engines seem pretty OK, but turbojets will easily push you to speeds that will cook your aircraft. Compare this with real jets, where the limiting factor for your engines is almost never that the aircraft is going to overheat... it's that the engines just can't push you any faster. The only aircraft with engines that even come close to the performance of KSP's turboramjets would be the SR71, and yeah, that thing got really hot and had to be made out of titanium because of it. But check out the engines on that thing! Each of the Pratt & Whitney J58 engines puts out 35,000 pounds of thrust, and are very specially designed around their bypasses and intakes for super high speed flight. The F100 engines on an an F15 each put out 14000 pounds of thrust at a TWR of about 7 to 1, and the F15 is itself known as an energy fighter (very high power). The General Electric CJ610 engine (used on, eg, a Lear Jet) puts out about 3000 pounds of thrust.

So if the basic jet engine sorta matches the Lear Jet, and the turboramjet sorta matches an SR71, there's a pretty huge gap in the middle that represents engines for the kinds of planes that many people want to build, and this might be messing with the perception of aero.

[Claw]

This impression might be exacerbated by the huge step in technology between the basic jet engines and the turbojets/rapiers. Basic jet engines seem pretty OK, but turbojets will easily push you to speeds that will cook your aircraft...

So if the basic jet engine sorta matches the Lear Jet, and the turboramjet sorta matches an SR71, there's a pretty huge gap in the middle that represents engines for the kinds of planes that many people want to build, and this might be messing with the perception of aero.

In my mind, this certainly is a huge problem. Considering the fact that there are only two air breathing engines, and a third if you throw in the rapier. It's not really practical to expect such a small number of engines to provide the performance needed for Mk1, Mk2, and Mk3 sized craft. They are all significantly different in size, weight, and drag. So, with so few engines, they are stuck in this middle ground of being too powerful for Mk1 craft, but a Mk3 craft ends up needing tons of engines. Definitely tough to balance with so few options.

Alternate options would be to add more engine types (such as SCRAM) or even just multimode the current engines to provide some sort of "feel" as if there are more of them.

Cheers,

~Claw

[allmhuran]

One thing that might help a great deal would be to throw in afterburner characteristics. Not only would this create a separate "class" of engine, it would also naturally balance that new class due to the decreased efficiency when on burner.

The whiplash turboramjet in KSP must, surely, be an afterburning engine to be able to provide the performance that it does provide. But if that were really the case then fuel consumption should increase massively when you push it into afterburner at, say, about 90% throttle (with an appropriate effect to let the user know that they are in fact now in afterburner and guzzling fuel).

This creates room for three jet engines: basic (high ISP, mach 0.5 - 0.8 for a "normal" looking Mk1 aircraft), advanced jet (mach 1 - 1.5 for the same aircraft, higher altitude, slightly lower ISP at sea level) and the turboramjet (average ISP at sea level off burner, capable of extremely high speeds and altitudes on burner at a tremendous efficiency cost)

You can then start re-tweaking the complex relationship between thrust, speed, drag, heating and altitude against that set. I don't know nearly enough about the numbers to say what that relationship should be, but I reckon the most advanced jet should probably get you to about mach 3.5 on burner at ~20,000m, with drag being a hard limit, and a slow overheat entering as a soft limit at about mach 3.

Edited May 7, 2015 by allmhuran

[DoToH]

Aero:

1.0.2 is spot on for blunt objects, but too draggy for pointed ones. This can't be fixed by just changing drag multipliers, the part's own drag coefficient (for each cube face) needs to be modified, say with an exponent in the range of 1-2 (testing will show what's correct). Once that's done, lift can get lowered again (to keep L/D constant for planes). Wing drag can also come down then to keep proportional, although wing drag at 0 alpha should come up (and wing drag at high alpha should come down, in relative terms).

Thermal:

In order to get back a somewhat challenging reentry, the convectionVelocityExponent needs to go up higher than 3, and the convectionFactor go down. However, to keep Eve survivable, the heat shield ablator's hsp needs buffing.

Can't be sure without testing, but these seem the changes I'd like.

[thereaverofdarkness]

The only aircraft with engines that even come close to the performance of KSP's turboramjets would be the SR71, and yeah, that thing got really hot and had to be made out of titanium because of it. But check out the engines on that thing! Each of the Pratt & Whitney J58 engines puts out 35,000 pounds of thrust, and are very specially designed around their bypasses and intakes for super high speed flight. The F100 engines on an an F15 each put out 14000 pounds of thrust at a TWR of about 7 to 1, and the F15 is itself known as an energy fighter (very high power). The General Electric CJ610 engine (used on, eg, a Lear Jet) puts out about 3000 pounds of thrust.

So if the basic jet engine sorta matches the Lear Jet, and the turboramjet sorta matches an SR71, there's a pretty huge gap in the middle that represents engines for the kinds of planes that many people want to build, and this might be messing with the perception of aero.

That J58 is actually a lot closer to the basic jet engine. The 1.45x5.44 meter engine has a mass of 2.7 tons and yet it produces a mere 150kN of thrust. In KSP terms, that's pretty pathetic. KSP engines are tremendously overpowered and yet the aerodynamics system forces us to use higher-end engines to get performance similar to the SR-71. The basic jet engine will get you around much better than most real aircraft can, but it won't fly you into the upper atmosphere very easily.

[allmhuran]

Sure, I'm not saying that the specs equate with real world specs, I'm just talking about the way engines progress from "low performance" to "high performance".

[Maarek_Stele]

2 things I'd like to note here that I think should be fixed in future patches.

1. parachutes with the new heat system. When using a heat shield, pod, and chute can survive extreme re-entry when you wait to stage the chute till lower altitudes. This is not the case when you set the chute using atmo pressure pre-deploy and stage the chute up high, the chute is destroyed even when not deployed. This makes no sense to me, if the chute is still packed staged or no it should survive if not deployed yet.

2. Fairings are related to the aero & heat so I'm putting here. The issue is that I noted that solar panels are working through un-jettisoned fairings. They should block the sun.

[Yakuzi]

The devs mentioned they got heaps of feedback on 1.0 aerodynamics from "big names in the aerospace industry" (I would get you a link, but KSP news is so dispersed I can't be bothered finding it), so why doesn't Squad ask them and ferram for advice/contribution?

The most important thing is that you get it right in the next version (you may want to consider a parallel beta candidate). From a craft design point of view, I am quite frustrated that important systems like aerodynamics are still incomplete/under development after the "1.0" release...

[Xellas]

During a mission I had to trigger a few things in Kerbin orbit, then one last thing on a sub-orbital trajectory. I decided to just throw up a throwaway probe core for the purpose, and after the sub-orbital test it had no further engines and was doomed. I decided to watch, as I expected it to burn up in the atmosphere. Mind you, this is a naked core with 4 batteries on it, and 2 LFO tanks, with no heatshields anywhere on the craft. It dived into the atmosphere probe-first.

And lived.

All the way to the ground. From 2.5 km/s starting velocity at 90km up. With no heatshields whatsoever. Not a single part exploded in fact.

Methinks a few tweaks are still in order, because as it stands the re-entry heating is basically no threat to ANY spacecraft whatsoever.

[Chris_2]

I'm posting this one more time, as to me it's pretty obvious what is wrong with the thermal system:

The biggest problem of the new system is the way too high thermal conduction. Heat should be much more localized to the place where the heat is generated. In what reality does the cockpit of a spaceplane heat to 1500°C from burning a rocket engine? Sure, the engine might get hot (well, actually, just the nozzle and combustion chamber of the rocket will heat or else there will be serious problems...), but now -my entire spaceplane- becomes glowing hot. Also, most parts should have much much lower heat resistance (say, 600C or so), but, decreasing the heat resistance of parts (that shouldn't have heat resistance) is not really possible, as these parts would then be destroyed as the spacecraft becomes 'uniformely hot' during an LV-N burn or reëntry. The solution is obvious: increase the thermal capacity of parts; decrease the thermal conduction between parts; then heat will become much more localized and only then the heat resistance of some can be decreased. That would also make reentry more interesting, so only parts that are designed to resist heat can be in the airstream.

Aero feels pretty good. I like it a lot that breaking the sound barrier is really hard. SSTO's should definitely -not- be made easier. I like that it is pretty hard to build a decent (like this ) SSTO. The only thing is that the wings need re-balancing in my opinion. Right now a plane barely needs wings and can glide with 40m/s. I'd suggest reducing the lift of wings (so more wings are needed), but also reducing the weight and drag of wings to compensate, so basically the same performance spaceplanes as now are possible, but with larger wings (so they don't look so rediculous as some do now). Also, IMHO, the mark 2 parts generate too much body lift. I like lifting body's, but right now mk2 planes don't need wings at all...

Edited May 10, 2015 by Chris_2

[SaturnV]

I‘m not good at aerodynamic, but I never saw any plane fly in fire at mach 2~3, only in KSP

[Kuu Lightwing]

I‘m not good at aerodynamic, but I never saw any plane fly in fire at mach 2~3, only in KSP

maybe because few planes fly that fast? Or because it's a spaceflight simulator an we need reentry effects, but orbital velocity is only 2300 m/s?

[freerunnering]

This thread is for voicing your opinion about the system. You can like it, hate it, point out the flaws

I have always played with FAR installed and so far I'm liking the new aero system.

I like reentry heating, it's realistic and fun (though really weak).

The need for strong heat shields for interplanetary missions makes going to the mun easy.

It'd be better to have different classes of heat shields. Cheaper weaker ones you unlock earlier. And then more expensive better ones for deep space unlocked later?

Now the thermal system:

I hate the new engine/craft heating system.

We have no radiators, no means of cooling anything down. There's no button I can press to say "pay more and make heavier to withstand more heat" it just doesn't work, and besides lots of ugly hacks with spamming girders and wings/solar panels, there's nothing I can do.

Am I meant to just guess which parts act as radiators (as I believe solar panels do, despite that being the opposite of real life) and spam them?

When building a craft there is no indication if the engine I've picked will produce too much heat and blow the rest of my craft up straight after launch. Does lifting off the throttle reduce heat production? I guess, but the UI game doesn't tell me how much heat the engine is producing anywhere and the heat gauges on parts are slow to update, so... guess.

I want reentry heat because it adds to the game. Craft overheating just infuriates me. I really want an option to disable engine/craft heating without turning off reentry heat.

This has sucked a lot of the fun out the game for me and made me regret updating KSP.

Managing overheating is not a gameplay mechanism I want, unless I'm reentering the atmosphere or skimming close to the Sun.

P.S: If I turn off reentry heating will the craft engine also be turned off, or am I stuck with this?

P.P.S: Sorry this reads a bit like a rant. Yesterday was the first time I have updated KSP and then regretted updating and got annoyed at the changes.

Edited May 11, 2015 by freerunnering

[treejoe4]

the heat shields they gave us are essentially pointless now, you can almost never need one

[Rhomphaia]

Is the heat production on the Skipper supposed to be so high?

It produces 1.75 times as much heat as the next hottest engine, very nearly up there with the NERV.

[NathanKell]

Ingame? Or is that from reading the cfg file? (heatProduction is scaled by part mass in use).

[Rhomphaia]

Well the number comes from the cfg, but I only checked the cfg after noticing skippers were running really hot compared to anything but the LV-N.

[itsthatguy]

OK: So now that we have re entry heating, re-entry with space planes is super annoying from LKO, and from higher speeds near impossible without taking multiple approaches to slow yourself down over a longer period of time. I've been developing a Kerbal Shuttle (Kerbal version of space shuttle, but I'm sure you guessed that.) Re-entry with it takes an insanely long time, or else I lose control surfaces to the heat and can't land.

My larger goal of using SSTOs to ferry things and Kerbals around the solar system, land on planets, return, etc. is now basically ruined because re-entry from deep space without heat shielding would be a MASSIVE pain in the arse.

In my opinion there needs to be either:

A: A way to procedurally produce a heat shield for the bottom of space plane parts (control surfaces, wings, fuselages, etc.) like the real Space Shuttle

B. Have space plane parts that already have heat shielding on the bottom.

Just a suggestion, and anyway if anyone has a solution to this problem that is already implemented in the game, please let me know

Thanks!

[tater]

I did some testing with a mk 1-2 pod, and set periapsis to 20km.

I tested so far at a max velocity of 11km/s (that was at about 500 km alt, I forgot to check at 70km, so above 11km/s). Heat shield burns up in no time (2 s?), and craft never exceeds 1374 K. All the max temps listed in the VAB (assuming they are correct) need to be seriously nerfed, IMO.

The issue with spaceplanes… dunno, I don't do them. The trouble is that either reentry is not a thing for capsules, or it is, and spaceplanes need some other solution. Perhaps aircraft would be better off with a larger kerbin to bleed off some velocity?

[itsthatguy]

The issue with spaceplanes… dunno, I don't do them. The trouble is that either reentry is not a thing for capsules, or it is, and spaceplanes need some other solution. Perhaps aircraft would be better off with a larger kerbin to bleed off some velocity?

I have no problem with most of the parts because of the ridiculous high max temps, but because heat gets distributed so much for some reason the control surfaces at the BACK overheat and I can't control it in order to land.

Edited May 17, 2015 by itsthatguy