Squad on the recent Aero changes

[KerikBalm]

I just want to make sure that 1.03 fixes these things:

http://forum.kerbalspaceprogram.com/threads/97285-KSP-v1-0-2-Stock-Bug-Fix-Modules-%28Release-v1-0-2b-3-May-15%29-Stock-Plus-%284-May-15%29

PartDragFix (3 May 15) - (STATUS: Initial Release) - Description: Drag for the new landing gear and Mk3 cargo bays are a bit off.

- Landing gear drag is backwards. Gear up gives more drag than gear down.

- Mk3 cargo bays (should) now properly occlude parts behind them.

Squad needs to make mk3 cargobays properly occlude, and it needs gear up to be less draggy than gear down

[Endersmens]

Mach 3 sustained at sea level... serious fun! Ferram is right in that it is the gas turbines that are the limiting factor: mass flow would make the turbine inlet temperatures go far beyond what any current or even near future turbine technology would allow. A variable bypass cycle engine could do it, but I shudder to think of the amount of fuel it would gobble (15:1 stoic to start plus burning rich... ugh!).

As for landing speeds, it's mostly wing planform and wing loading (it's more complicated than that, but nobody is really interested in every single factor) that determines landing speeds, not the type of engine. Modern jet engined fighters have high landing speeds because of their swept/delta wings (and compensate for it with flaps and slats), not because they lack propellers.

IMHO, increasing drag and reducing lift all across the board isn't the solution to kludging blunt body physics, nor is "fiddling with it till it feels right" because that is simply using bias to solve an engineering issue that should have been solved mathematically from the beginning. Work the system until it works, as they say.

That said, I guess it's good that they're still mulling aero over. I'd hate to have been stuck with 1.0.2 aero and heating... even if it will break my latest round of SSTOs and spaceplanes.

Oh, the comment I made about propellers wasn't directed at propellers, I was just giving an example of a plane that can reasonably land at 30 m/s.

[basic.syntax]

There was a Squadcast? It wasnt friday yesterday... Is there a summary somewhere?

I'm working on a summary. Squad broadcast a "full team" office party direct from HQ, for close to 2 hrs. Twitch archive is at this link.

[Elthy]

I'm working on a summary.

Great to hear, i hate watching streams. Especialy since it seems its 19 pieces, some of them are not even a whole minute long...

[Roflcopterkklol]

Soooo sqaud likes soupospheres?....

Why not just keep the old aero model then lol...

[tater]

The F-104's thrust margin (excess thrust) increases with mach number until the engine reaches temperature limits. The thrust margin is 12,000lbs at mach 2, and a little under 5000 at 0.8.

[LostOblivion]

Soooo sqaud likes soupospheres?....

Why not just keep the old aero model then lol...

The new aero is still a huge improvement over the old one. Onrockets, I can't say I note much difference from FAR actually.

[DoToH]

Mu - "exactly. There's no way you should be able to do high mach at sea level..."

If SQUAD thinks this is aero problem and not engine OP problem, I'm done with stock aero. Waiting for FAR is the best option post 1.0.

[juanml82]

I thought they had? I've had very few of these, and the solution tends to be to remove and refit all your engines and intakes

One RAM or shock cone intake seems to be enough to run an engine up to its flight ceiling. Having less than 1:1, or trying to fly level at the peak of altitude, might cause the engine to suffocate, but by and large I find they shut down before they run out of air.

Assymetric thrust is still a thing. You won't typically notice unless you make dumb stuff like one intake for two ramjets or you put a lot of engines in a plane with just one intake each. But it's there.

[Kaezan]

The way I understand it is it's similar to the way an airconditioner works.

There are X molecules of heat in a given amount of air. If you increase the pressure your putting more air/heat molecules into the same amount of space.

For instance if 1 cubic metre of air has 1 heat molecule under regular conditions asl. Compress that same air to double it's pressure so now you have 2 molecules of heat in 1 cubic metre of air meaning its twice as hot.

Now if you think of that as the atmosphere, the higher you go the less pressure and the less density so the less heat in the same space than asl.

Thicker air = more heat for the same amount of space.

The air in front of a fast moving vehicle (aircraft) has to compress and move out of the way. The faster you go the more than air has to compress in front of the vehicle meaning the vehicles is exposed to more heat.

Thats my understanding of how it works anyway in laymans terms.

Pressure (symbol: p or P) is the force applied perpendicular to the surface of an object per unit area over which that force is distributed.

http://en.wikipedia.org/wiki/Pressure

The pressure "felt" by the airconditioner inlet is X times the force a single molecule do.

To double the pressure in the inlet either the molecule has double the force, or there are 2 molecules.

Thicker air means more molecules, not a direct increase of heat. (if there are 3 molecules at 30ºC and if you insert another 3 molecules at 30º the system is at 30º, not higher.)

If i tell you that air molecules are rubber spheres and the aircraft is pushing through them, is it clear that the problem is the drag those spheres cause and not the "move away"?

[basic.syntax]

Great to hear, i hate watching streams. Especialy since it seems its 19 pieces, some of them are not even a whole minute long...

The chunking is a sign of their streaming architecture, they don't really want to be a download service. If you want to download it for later, it takes a third party utility... I doubt Twitch encourages that... downloads don't bring ad views

I can't do quick summaries... its going to be more like a transcript. I need to step out for a few hours, and it's not done yet.

[Kuu Lightwing]

If SQUAD thinks this is aero problem and not engine OP problem, I'm done with stock aero. Waiting for FAR is the best option post 1.0.

you seem to focus on one issue while there are many of them. Scott Manley also noticed that capsules don't slow enough. Simply nerfing the jets will affect their performance at regimes other than "fly level at asl"

[DoToH]

you seem to focus on one issue while there are many of them. Scott Manley also noticed that capsules don't slow enough. Simply nerfing the jets will affect their performance at regimes other than "fly level at asl"

Of course. Solving issues is a matter of identifying the correct cause, that's my point. Tweaking wrong parameters will solve some issues and create new ones, as they did when they increased drag without taking into account the effect on reentry mechanics. IMO, aero values have too much impact on gameplay to adjust them with a fast hotfix (and that's why I think 1.0.1 was a bad decision). If they tweak aero values, they have to test how new values affect gameplay: engine parameter balance for both rocket and jet engines, reentry, low altitude/speed flight, high altitude/speed flight, fairings..... Five days is not enough time to test every affected aspect.

If their conclusion about reaching mach 3 ASL was "we need more drag", I can't trust them any more to give a good solution for aero.

Edited May 8, 2015 by DoToH

[sephirotic]

Not to pick on you in particular since I've seen a lot of people do it, but...once again, static thrust isn't maximum thrust. The number you're quoting is the static thrust: it's the thrust at sea level on a standard day. It is most certainly not the thrust at Mach 1 at sea level, nor is it the thrust at Mach 2 a bunch of kilometers up.

I'm quite aware of that, that is why if you take a closer look at my SS, you'll see my actual thrust at 100kn, I've actually checked the specs of the J39 engine and I doubt it can actually reach that.

[Endersmens]

My suggestion would be for them to optimize the atmosphere for reentry and launches and such, so that the space side seems right, and then just adjust plane parts until they fit realistically in to the new atmo. IE reducing jet thrust, adjusting drag and lift. that kind of stuff.

[Eric S]

I wasn't doing anything wrong. I've played this game enough (couple hundred hours) to understand how it works. The standard chute given when starting a new career in 1.0 just refused to slow the craft enough to prevent it exploding.

I'll chip in with not having a problem with parachutes in 1.0. A single starter parachute on the starter capsule resulted in a 100% recovery rate of the capsule provided nothing overheated. Then again, except for sub-orbital flights, I always went for a fairly shallow reentry (30km periapsis or so) which gave the atmosphere plenty of time to slow down before it came anywhere near the ground. I'd usually tweak the pressure trigger so that I got a partial deployment somewhere around 10km and full deployment at 350m, which would result in a long, slow descent.

What kind of reentry profile were you using when you had these problems?

[Kuu Lightwing]

Of course. Solving issues is a matter of identifying the correct cause, that's my point. Tweaking wrong parameters will solve some issues and create new ones, as they did when they increased drag without taking into account the effect on reentry mechanics. IMO, aero values have too much impact on gameplay to adjust them with a fast hotfix (and that's why I think 1.0.1 was a bad decision). If they tweak aero values, they have to test how new values affect gameplay: engine parameter balance for both rocket and jet engines, reentry, low altitude/speed flight, high altitude/speed flight, fairings..... Five days is not enough time to test every affected aspect.

If their conclusion about reaching mach 3 ASL was "we need more drag", I can't trust them any more to give a good solution for aero.

They designed the game. I'm pretty sure they have a better understanding on how does it work. The problem was that they fixed some increased drag bug just before 1.0 when the whole atmo was balanced as if the bug is in place.

As for reentry/heat mechanics, which one you don't like - for planes or for capsules?

[LostOblivion]

I'm also gonna jump on the boat where I don't understand why the increased drag was the solution to fast falling pods. Pods fall fast. IRL you slow them down with parachutes, and if those parachutes rip your ship apart, you use drogues first.

[Kuu Lightwing]

IRL they don't fall at Mach 2.

[sal_vager]

They were falling faster than should be possible, drag was even less than in FAR so just changing the chutes wouldn't solve the underlying issue there.

It's not helping that all parts make lift and lift is too high now, even the pod and heat shield makes more lift than it should so it feels much dragger than it's supposed to.

Also, anyone who is still having problems with their parachutes should delete their PartDatabase.cfg, as upgrading to 1.0.2 doesn't replace that file if it finds it's already there.

[DoToH]

A single starter parachute on the starter capsule resulted in a 100% recovery rate of the capsule provided nothing overheated.

Right. Tried again in my 1.0 install and touchdown speed for Mk1 pod + Mk16 chute is 7 m/s, half the crash tolerance for the pod.

They designed the game. I'm pretty sure they have a better understanding on how does it work

They designed three parts (heatshields). They turned those heatshields useless with their 1.0.1 patch. As every other human, they can be wrong.

As for reentry/heat mechanics, which one you don't like - for planes or for capsules?

Are they different?

Edited May 8, 2015 by DoToH

[Enceos]

There's one bad thing Squad team never does for aero - consult the experts, ferram4 is the best candidate. He's knows about aerodynamics more than any other guy on this forum.

[Jouni]

I'm also gonna jump on the boat where I don't understand why the increased drag was the solution to fast falling pods. Pods fall fast. IRL you slow them down with parachutes, and if those parachutes rip your ship apart, you use drogues first.

Reentry capsules are designed to have a lot of drag and slow down quickly in order to minimize heating. Soyuz deploys the drogue chute at around 9 km, when its speed is around 230 m/s. The Apollo capsule had over 3x more surface area but less than 2x more mass, so it slowed down even faster. It apparently deployed drogue chutes at around 7 km at speeds under 150 m/s. Kerbin's atmosphere has a lower scale height than ours, so the comparable altitudes should be roughly 60% of those figures.

[Kuu Lightwing]

Are they different?

Maybe... Yes? Have you ever heard of a capsule that burned on ascent in 1.0.0? Planes did that a lot.

[m4v]

Reentry capsules are designed to have a lot of drag and slow down quickly in order to minimize heating. Soyuz deploys the drogue chute at around 9 km, when its speed is around 230 m/s. The Apollo capsule had over 3x more surface area but less than 2x more mass, so it slowed down even faster. It apparently deployed drogue chutes at around 7 km at speeds under 150 m/s. Kerbin's atmosphere has a lower scale height than ours, so the comparable altitudes should be roughly 60% of those figures.

For comparison, in 1.0 the terminal velocity of the small pod was like 280m/s at sea level, by just letting it drop from 10km altitude the pod would reach freaking mach 0.8