Observations on aero and part balance

[Streetwind]

So let's talk about the gameplay itself for once, shall we? I've not done a whole lot in KSP2 yet, but I did do a few comparisons to KSP1, just to see how close the two games were, and where they would differ.

 

The primary difference I found is that apparently, the aerodynamics model is noticeably more sensitive when it comes to the shape of parts and the vessel you build. There's a bigger difference between "sleek and pointy" and "blunt and flat" than before.

Exhibit A: I am consistently reaching low Kerbin orbit with 3200 m/s dV now, where I needed 3400-3500 in KSP1. Sometimes even a bit less than 3200. The rockets I was testing this with are super simple: mk1 pod with a parachute, fuel tanks, and engine. Nothing attached to the outside.

Exhibit B: I tried launching an uncrewed probe. I knew my launch vehicle was passively unstable, as it had no second stage to keep the CoM forward (it is so easy to get into Kerbin orbit single-stage), and a fairing larger than the stack, but I stubbornly tried anyway. After flipping over three times, I gave in to common sense and went back to the VAB, planning to add a second stage. But on a hunch, the first thing I tried was tucking the solar panels just a bit more snugly against the probe, and rebuilding the fairing just a bit more snugly around it. I also made the tip of the fairing more pointy. Fairings currently appear to be massless, so there's no reason to be stingy. Lo and behold - the thing flew without flipping! Just by changing the aerodynamics of the fairing.

Exhibit C: In KSP1, I would typically hold on to my fairings until about 45 km. By common wisdom, this was already considered fairly high, and most players would ditch their fairings lower than that. This time in KSP2, I had troubles with fairing separation under thrust (in KSP1 I used to turn down the separation force of fairings to get a smooth detach, here in KSP2 it seems I need to turn it up instead), and so I hung on to my fairing until I had my AP where I wanted and shut down the engine. That was at 55 km altitude. Just coasting like that, my apoapsis altitude changed by maybe one meter per second, dropping due to drag on the vehicle. As soon as I popped the fairings, though? The apoapsis altitude started changing rapidly, maybe as much as 10 meters per second. Not a problem, obviously, as I was rapidly leaving the atmosphere behind, but that is a huge amount of drag for 55km. An order of magnitude drag increase just from popping the fairing around a XS size probe. KSP2 definitely encourages us to encapsulate our payloads, and hang on to our fairings for longer.

 

EDIT: apologies for how this post became a wall of text; I was trying to split it into two posts, but the forum force-merges them every time.

 

The second difference? There were a lot of rocket engine buffs. A few nerfs too, though far fewer and smaller. Overall, engines have gotten better, which probably contributes to how it feels easier to launch now than in KSP1.

• The Reliant lost 5s of Isp (260s-305s instead of 265s-310s), but got uprated from 240 to 260 kN. Doesn't seem like much, but where a 16 ton vehicle would have a TWR of 1.307 on the pad in KSP1, the same vehicle will have a TWR of 1.412 in KSP2. That's a difference you'll notice in flight. In a sense, the Reliant became the Kodiak from Making History, and that was a no-brainer upgrade.
• The Swivel got a major buff - and fairly so, I'd say, considering how the Reliant overshadowed it in KSP1. Vacuum Isp and thrust stayed the same, but sea level Isp went from 250s to 280s, and as a result, sea level thrust went from 168 kN to 188 kN. At the same time, its mass dropped from 1.5 tons to 1.4 tons. It's a much better engine now.
• The Terrier actually received a mild nerf! Only 335s vacuum Isp instead of 345s. This will definitely impact the way we build Mun landers. However, its role as a second stage engine for launches from Kerbin wasn't much affected, because its sea-level Isp went from 85s to 170s. The Terrier will now be more efficient and have better TWR just after stage separation.
• The Dart got a big swing with the nerfbat. 300s-320s Isp instead of 290s-340s, and maximum thrust dropped from 180 kN to 170 kN. But fear not... even after all that, it still remains one of the best launch engines for S-size stacks in the game. Just shows how OP it used to be in KSP1.
• The Vector was another nerf candidate: it got downrated from 1000 kN to 850 kN, sea level Isp dropped from 295s to 285s, and everything else stayed the same. Yeah, it's strictly worse now. Yeah, it's still a silly engine for its form factor, and you should have no issues building shuttle replicas.
• Hey, remember the Thud? Yeah, me neither! In all seriousness, that engine was so underwhelming in KSP1. Now it went from 120 kN max thrust to 140 kN, hopefully helping it find more use.
• Looking at the XS-sized engines, the allmighty Ant got its vacuum Isp increased from 315s to 330s, though sadly it lost its non-blocky second variant, which I loved... The spider got 25% more thrust with no other changes (2.0 kN -> 2.5 kN), while the Twitch got a little heavier (80kg -> 100kg) and had its Isp changed from 275s-290s to 265s-298s. The Spark lost 5s vacuum Isp but gained 5s sea level Isp (now 270s-315s).
• Going up in size instead, the Skipper got... nerfed? A little? Max thrust went from 650 kN to 600 kN. But Isp went up... strictly speaking... theoretically... by exactly 2s
• But hey, at least the Mainsail, which already had too much thrust in KSP1, now has even more thrust! 1600 kN instead of 1500. It lost a lot of Isp though, going from 285s-301s to 265s-307s. Prepare to dump a lot of fuel into this hungry maw. But when you do, it'll go.
• The Poodle unsurprisingly got the same treatment as the Terrier, meaning: less vacuum Isp (350s -> 340s) but more sea level Isp (90s -> 175s). But unlike the Terrier, it also went down in max thrust significantly, from 250 kN to 215 kN. Fair enough, it used to be on the awkwardly-too-strong side for most landers. This might actually make it easier to use.
• Another size class up, the Rhino went on a diet: 8 tons instead of 9. In return its maximum thrust dropped from 2000 kN to 1750. The redesign away from orbital use to a sustainer type is felt in the Isp, which changed from 205s-340s to 285s-325s. For orbital work we now have the Labradoodle, which is completely new.
• The Mammoth is now the Mammoth-II, and looks the part of its namesake with its ginormous trunk errr I mean turbopump exhaust. It got a mild thrust uprating from 4000 kN to 4250 kN, and like the mainsail, lost a good chunk of Isp: 270s-310s instead of 295s-315s.

 

• All of the SRBs stayed the same, and I didn't look at the jet engines, as I'm just not a plane type of person.

 

• Here is where it gets really interesting though: the high-impulse, alternative-fuel engines. All of them got so much stronger.
• Just look at the Nerv. Maximum thrust went from 60 kN to 75 kN. Isp went from 185s-800s to 250s-900s. Those are two massive buffs, but it's not the end just yet: in KSP2, all fuel tanks - including hydrogen - got normed to a mass ratio of 9, whereas in KSP1, the plane parts that were so often used with the Nerv due to a lack of dedicated LF-only rocket tanks were more around 8. So not only did the engine get a lot better, the tanks for the engine got better too!
• Then there's the new nuclear engine, the Swerv. And it's absurd. There were modded engines available for KSP1 that were considered OP, and they were not as OP as this engine is. It is overtuned to such a monstrous degree next to all other engines, there's just no comparison. I reckon this is our preview for what higher tech levels are going to be offering, at a game stage where the Kerbals have colonies all over the system and interstellar technology is close at hand.
• Let's not forget the Dawn ion drive, either. On the surface, it received a small nerf, in the sense that it needs a bit more energy to run now (10 EC/s instead of 8.74 EC/s). But just like the Nerv is benefitting from better tankage, so is the Dawn. Xenon tanks used to have a mass fraction of 4. Now, just like all other tanks, they're at 9. That means they contain more than two and a half times the amount of xenon for the same dry mass. You might not notice it that much when attaching only a single tank and getting a small few thousand m/s of dV; but it's gonna scale so much higher so much more easily. A single ion stage with 40,000m/s worth of dV would have been borderline impossible in KSP1 even without worrying about how to launch it; now in KSP2, it's not any harder to achieve than making a Terrier stage with 3,100m/s worth of dV.
• And remember, the perhaps biggest buff to low-TWR engines like the Nerv and Dawn: the ability to time warp during burns. I mean, once that actually works reliably But yeah, get used to the idea of working a lot more with really high dV deep space craft in the future. It's gonna be easier than ever before.

 

Edited February 26, 2023 by Streetwind

[KerikBalm]

Dart was not OP in KSP1.

It's only use really was as a core stage burning from liftoff to orbit and beyond. To do well at that job, it needs a good thrust to cross section ratio (so it can lift a tall core stack).

It doesn't have that, it's even worse now

[The Aziz]

2 hours ago, Streetwind said:

Exhibit A: I am consistently reaching low Kerbin orbit with 3200 m/s dV now, where I needed 3400-3500 in KSP1. Sometimes even a bit less than 3200. The rockets I was testing this with are super simple: mk1 pod with a parachute, fuel tanks, and engine. Nothing attached to the outside.

Exhibit B: I tried launching an uncrewed probe. I knew my launch vehicle was passively unstable, as it had no second stage to keep the CoM forward (it is so easy to get into Kerbin orbit single-stage), and a fairing larger than the stack, but I stubbornly tried anyway. After flipping over three times, I gave in to common sense and went back to the VAB, planning to add a second stage. But on a hunch, the first thing I tried was tucking the solar panels just a bit more snugly against the probe, and rebuilding the fairing just a bit more snugly around it. I also made the tip of the fairing more pointy. Fairings currently appear to be massless, so there's no reason to be stingy. Lo and behold - the thing flew without flipping! Just by changing the aerodynamics of the fairing

What's your launch profile? Cuz for the love of all that's green, I can't fly anything the same way I used to in KSP1.

[tstein]

1 minute ago, The Aziz said:

What's your launch profile? Cuz for the love of all that's green, I can't fly anything the same way I used to in KSP1.

My impression is that the DV shown in VAB is simply wrong. I get  to Orbit also with  rockets that by VAB measurements should not be able to. My impression is that the VAB is SUPER pessimistic about the ISP in atmosphere and treat as if you  stayed the whole time at se level and suddenly  jumped to 71 km.

An adition for me, the lack of the vernier engine force sme in much cumber designs than in KSP 1. The lack of the "soviet" parts is really frust5ratign for me since I basically  built my rockets with those almost always.

[Streetwind]

It's definitely not a dV math issue, at least not with the test rockets I've been flying for those observations. I can literally mount a smaller tank than in KSP1 and get into orbit anyways - with an engine that has the same or slightly less Isp (the Reliant).

I have, however, noticed some weirdness with dV math in more complex designs.

For example, I just tried to do a Mun mission. First stage with a Skipper, second stage with a Poodle, third stage was a lander can with some small tanks and eight Ant engines. The VAB certified me 6650 m/s dV, which would be enough to land on the Mun and return to Kerbin. In practical application, I couldn't even land that without running out of fuel.

What went wrong? Well, for starters, the calculator doesn't like more than one engine on a stage. If I attached a single Ant to my lander can, the calculated dV figure was noticeably smaller than with all eight attached, despite this being less mass! Another problem lies in the fuel crossfeed logic being broken. When I launch this rocket, the first stage will drain its own tanks, and the tanks of the lander, but (curiously enough) not the tanks of the second stage. This not only leads to fuel being consumed by a lower Isp engine, reducing available dV below what the calculator said, but additionally, the calculator actually factors in that it can errorneously access tanks it shouldn't be able to. So it gave me a higher dV figure for the first stage. The second stage did not drain any tanks it shouldn't, but I can't disprove the suspicion that it, too, calculated with the wrong amount of fuel. All in all, this rocket probably displayed at least 1000m/s more than it actually had.

The reason I had none of these issues with my test rockets likely lies in the fact that they were a single stage with a single engine, thus neatly sidestepping all of the mentioned problems.

 

Edited February 26, 2023 by Streetwind

[regex]

2 hours ago, The Aziz said:

What's your launch profile? Cuz for the love of all that's green, I can't fly anything the same way I used to in KSP1.

It depends on TWR but a good starting point is to go up until about 40~50m/s and then tilt over until your prograde is about 5~6°. Then just hold prograde. And that may even be a little shallow, when I tried a launch like that I ended up with AP 190km.

Both the NERV and the SWERV have been brought up to match real/theoretical isps for their respective engine types. Which is good, there was no need to nerf that. OTOH, the SWERV is a gas core nuclear engine so hopefully we'll see mechanics related to irradiating other ships through careless firing.

[The Aziz]

5 minutes ago, regex said:

Then just hold prograde

I did. At random point my rocket tilted away from prograde on its own.

The theory is simple and I understand it, trouble is it doesn't work in practice even with seemingly perfect trajectory. You'd think that drag at 10km+ altitude shouldn't be the cause of flipping when you're holding prograde, but here we are.

[regex]

11 minutes ago, The Aziz said:

I did. At random point my rocket tilted away from prograde on its own.

The theory is simple and I understand it, trouble is it doesn't work in practice even with seemingly perfect trajectory. You'd think that drag at 10km+ altitude shouldn't be the cause of flipping when you're holding prograde, but here we are.

Add four fins at the bottom to help with stability, maybe split your one engine into four for better control authority. vOv

Clearly we're in an entirely new game with new rules.

[J.Random]

18 minutes ago, The Aziz said:

I did. At random point my rocket tilted away from prograde on its own.

The theory is simple and I understand it, trouble is it doesn't work in practice even with seemingly perfect trajectory. You'd think that drag at 10km+ altitude shouldn't be the cause of flipping when you're holding prograde, but here we are.

Have any wheeled rovers inside the fairings? There seem to be some weirdness there, with random "bumps" just throwing SAS off course.

[The Aziz]

47 minutes ago, regex said:

Add four fins at the bottom to help with stability, maybe split your one engine into four for better control authority. vOv

Clearly we're in an entirely new game with new rules.

First time I used fins for stability the SAS sent me like 30 degrees off east where I was pointing at. There's a lot of unexpected behavior, unseen in KSP1. Same rocket designs, same planet, same flight path, different results.

42 minutes ago, J.Random said:

Have any wheeled rovers inside the fairings? There seem to be some weirdness there, with random "bumps" just throwing SAS off course.

I have a hard time getting to and returning from the Mun thanks to the rockets doing what they do, there's no place for rovers yet, or anything larger than a 2.5 capsule.

[Streetwind]

The simpler and more minimalistic a rocket is, the better it likely performs in the current state of the game. Things can't break if they're not there

Regardless, this thread was not meant as a discussion of what doesn't work. We have like two thousand of those threads already. Instead I wanted to point out interesting little tidbits and trends we can already see.

[Sea_Kerman]

7 hours ago, Streetwind said:

When I launch this rocket, the first stage will drain its own tanks, and the tanks of the lander, but (curiously enough) not the tanks of the second stage.

This, oddly enough, seems to be caused by landing legs

 

[Streetwind]

Wow, that's hilarious Never would have suspected those.

[Rocket Farmer]

7 hours ago, The Aziz said:

I did. At random point my rocket tilted away from prograde on its own.

The theory is simple and I understand it, trouble is it doesn't work in practice even with seemingly perfect trajectory. You'd think that drag at 10km+ altitude shouldn't be the cause of flipping when you're holding prograde, but here we are.

I personally find if I’m wandering off prograde or flipping I need to

1.  Lower the drag of the top of my stack.  Move external items (solar panels, antenna) lower down and put batteries inside the stack instead of hanging in the outside.

2. make any fairings as pointy as possible.

3. Narrow the bulge of the top of the stack (make it more aerodynamic).

4. Put fins/wings/control surfaces on the bottom of the rocket near the engines to create drag at the back of the rocket.

5. Increase SAS modules.

6. If all else fails (and sometimes it does if you are lifting a monstrosity) just put a huge amount of RCS on board and leave it on during the dangerous ascent parts.

With all of the above you could launch a pancake the size of a baseball diamond.

[Rpatto92]

On 2/26/2023 at 1:57 PM, tstein said:

My impression is that the DV shown in VAB is simply wrong. I get  to Orbit also with  rockets that by VAB measurements should not be able to. My impression is that the VAB is SUPER pessimistic about the ISP in atmosphere and treat as if you  stayed the whole time at se level and suddenly  jumped to 71 km.

An adition for me, the lack of the vernier engine force sme in much cumber designs than in KSP 1. The lack of the "soviet" parts is really frust5ratign for me since I basically  built my rockets with those almost always.

I noticed when building  space planes (failed) that the rappiers were producing closer to 150KN of thrust at over bellow 5000meters and in the VAB they're only rated for 105KN in atm. Strangely even with that extra over max rated thrust, my plane fails to exceed 200ms. I haven't as yet eliminated all potential causes but I suspect fairing drag to be a huge factor or drag in general being significantly  higher. It also appears that inertia could perhaps be playing a role, as maintaining high speeds seems a lot easier and accelerating with massive vessels even with close to or exceeding 1:1 thrust/weight a lot harder. Also, fuel appears to burn more slowly and  larger craft appear to be much heavier than perhaps they were previously. 

Could be completely wrong, perhaps some other factor is at play warping my perception of the game balance but it's certainly a little off.

[The Aziz]

It does feel like a thick soup. Unless I put some crazy TWR, my rockets are barely accelerating in low parts of the atmo, so no wonder they're flipping. There are some serious drag problems otherwise it wouldn't act like that. I used to launch rockets in KSP1 with TWR ≈1.2, now it's impossible, 1.8 feels like absolute minimum to even keep the rocket going.

[Periple]

1 hour ago, The Aziz said:

It does feel like a thick soup. Unless I put some crazy TWR, my rockets are barely accelerating in low parts of the atmo, so no wonder they're flipping. There are some serious drag problems otherwise it wouldn't act like that. I used to launch rockets in KSP1 with TWR ≈1.2, now it's impossible, 1.8 feels like absolute minimum to even keep the rocket going.

I haven't had any trouble launching but then I make my rockets pointy!

I have noticed the same thing with planes though: a plane where everything is in a single stack is much slipperier than one that has dual fuselages or nacelles.

[JoeSchmuckatelli]

On 2/26/2023 at 6:17 AM, Streetwind said:

apologies for how this post became a wall of text

Actually I appreciate your write up.  I've had the vague concern that it's much easier to get to orbit than KSP was.  Didn't know exactly, how, but the sense was there. 

If I may suggest - this is a post about 'balance' which is a great discussion to have when the game is performant - and everyone is in the massive bug hunt mode.  So if you don't get much response now, bump it after the second patch! 

(Presumes most of the game is functional because of the second patch) 

On 2/26/2023 at 11:17 AM, regex said:

depends on TWR but a good starting point is to go up until about 40~50m/s and then tilt over until your prograde is about 5~6°. Then just hold prograde. And that may even be a little shallow, when I tried a launch like that I ended up with AP 190km

That is pretty much what I did in KSP - but I don't trust 'hold prograde' in 2. 

Need to play around with it if it is working for you - but for me?  It's like instead of holding prograde and getting pulled by gravity into a turn - the SAS is looking way ahead for the PE marker and using it as a target.  (hence the flip) 

[RaBDawG]

On 2/26/2023 at 6:17 AM, Streetwind said:

So let's talk about the gameplay itself for once, shall we? I've not done a whole lot in KSP2 yet, but I did do a few comparisons to KSP1, just to see how close the two games were, and where they would differ.

 

The primary difference I found is that apparently, the aerodynamics model is noticeably more sensitive when it comes to the shape of parts and the vessel you build. There's a bigger difference between "sleek and pointy" and "blunt and flat" than before.

Exhibit A: I am consistently reaching low Kerbin orbit with 3200 m/s dV now, where I needed 3400-3500 in KSP1. Sometimes even a bit less than 3200. The rockets I was testing this with are super simple: mk1 pod with a parachute, fuel tanks, and engine. Nothing attached to the outside.

Exhibit B: I tried launching an uncrewed probe. I knew my launch vehicle was passively unstable, as it had no second stage to keep the CoM forward (it is so easy to get into Kerbin orbit single-stage), and a fairing larger than the stack, but I stubbornly tried anyway. After flipping over three times, I gave in to common sense and went back to the VAB, planning to add a second stage. But on a hunch, the first thing I tried was tucking the solar panels just a bit more snugly against the probe, and rebuilding the fairing just a bit more snugly around it. I also made the tip of the fairing more pointy. Fairings currently appear to be massless, so there's no reason to be stingy. Lo and behold - the thing flew without flipping! Just by changing the aerodynamics of the fairing.

Exhibit C: In KSP1, I would typically hold on to my fairings until about 45 km. By common wisdom, this was already considered fairly high, and most players would ditch their fairings lower than that. This time in KSP2, I had troubles with fairing separation under thrust (in KSP1 I used to turn down the separation force of fairings to get a smooth detach, here in KSP2 it seems I need to turn it up instead), and so I hung on to my fairing until I had my AP where I wanted and shut down the engine. That was at 55 km altitude. Just coasting like that, my apoapsis altitude changed by maybe one meter per second, dropping due to drag on the vehicle. As soon as I popped the fairings, though? The apoapsis altitude started changing rapidly, maybe as much as 10 meters per second. Not a problem, obviously, as I was rapidly leaving the atmosphere behind, but that is a huge amount of drag for 55km. An order of magnitude drag increase just from popping the fairing around a XS size probe. KSP2 definitely encourages us to encapsulate our payloads, and hang on to our fairings for longer.

 

EDIT: apologies for how this post became a wall of text; I was trying to split it into two posts, but the forum force-merges them every time.

 

The second difference? There were a lot of rocket engine buffs. A few nerfs too, though far fewer and smaller. Overall, engines have gotten better, which probably contributes to how it feels easier to launch now than in KSP1.

• The Reliant lost 5s of Isp (260s-305s instead of 265s-310s), but got uprated from 240 to 260 kN. Doesn't seem like much, but where a 16 ton vehicle would have a TWR of 1.307 on the pad in KSP1, the same vehicle will have a TWR of 1.412 in KSP2. That's a difference you'll notice in flight. In a sense, the Reliant became the Kodiak from Making History, and that was a no-brainer upgrade.
• The Swivel got a major buff - and fairly so, I'd say, considering how the Reliant overshadowed it in KSP1. Vacuum Isp and thrust stayed the same, but sea level Isp went from 250s to 280s, and as a result, sea level thrust went from 168 kN to 188 kN. At the same time, its mass dropped from 1.5 tons to 1.4 tons. It's a much better engine now.
• The Terrier actually received a mild nerf! Only 335s vacuum Isp instead of 345s. This will definitely impact the way we build Mun landers. However, its role as a second stage engine for launches from Kerbin wasn't much affected, because its sea-level Isp went from 85s to 170s. The Terrier will now be more efficient and have better TWR just after stage separation.
• The Dart got a big swing with the nerfbat. 300s-320s Isp instead of 290s-340s, and maximum thrust dropped from 180 kN to 170 kN. But fear not... even after all that, it still remains one of the best launch engines for S-size stacks in the game. Just shows how OP it used to be in KSP1.
• The Vector was another nerf candidate: it got downrated from 1000 kN to 850 kN, sea level Isp dropped from 295s to 285s, and everything else stayed the same. Yeah, it's strictly worse now. Yeah, it's still a silly engine for its form factor, and you should have no issues building shuttle replicas.
• Hey, remember the Thud? Yeah, me neither! In all seriousness, that engine was so underwhelming in KSP1. Now it went from 120 kN max thrust to 140 kN, hopefully helping it find more use.
• Looking at the XS-sized engines, the allmighty Ant got its vacuum Isp increased from 315s to 330s, though sadly it lost its non-blocky second variant, which I loved... The spider got 25% more thrust with no other changes (2.0 kN -> 2.5 kN), while the Twitch got a little heavier (80kg -> 100kg) and had its Isp changed from 275s-290s to 265s-298s. The Spark lost 5s vacuum Isp but gained 5s sea level Isp (now 270s-315s).
• Going up in size instead, the Skipper got... nerfed? A little? Max thrust went from 650 kN to 600 kN. But Isp went up... strictly speaking... theoretically... by exactly 2s
• But hey, at least the Mainsail, which already had too much thrust in KSP1, now has even more thrust! 1600 kN instead of 1500. It lost a lot of Isp though, going from 285s-301s to 265s-307s. Prepare to dump a lot of fuel into this hungry maw. But when you do, it'll go.
• The Poodle unsurprisingly got the same treatment as the Terrier, meaning: less vacuum Isp (350s -> 340s) but more sea level Isp (90s -> 175s). But unlike the Terrier, it also went down in max thrust significantly, from 250 kN to 215 kN. Fair enough, it used to be on the awkwardly-too-strong side for most landers. This might actually make it easier to use.
• Another size class up, the Rhino went on a diet: 8 tons instead of 9. In return its maximum thrust dropped from 2000 kN to 1750. The redesign away from orbital use to a sustainer type is felt in the Isp, which changed from 205s-340s to 285s-325s. For orbital work we now have the Labradoodle, which is completely new.
• The Mammoth is now the Mammoth-II, and looks the part of its namesake with its ginormous trunk errr I mean turbopump exhaust. It got a mild thrust uprating from 4000 kN to 4250 kN, and like the mainsail, lost a good chunk of Isp: 270s-310s instead of 295s-315s.

 

• All of the SRBs stayed the same, and I didn't look at the jet engines, as I'm just not a plane type of person.

 

• Here is where it gets really interesting though: the high-impulse, alternative-fuel engines. All of them got so much stronger.
• Just look at the Nerv. Maximum thrust went from 60 kN to 75 kN. Isp went from 185s-800s to 250s-900s. Those are two massive buffs, but it's not the end just yet: in KSP2, all fuel tanks - including hydrogen - got normed to a mass ratio of 9, whereas in KSP1, the plane parts that were so often used with the Nerv due to a lack of dedicated LF-only rocket tanks were more around 8. So not only did the engine get a lot better, the tanks for the engine got better too!
• Then there's the new nuclear engine, the Swerv. And it's absurd. There were modded engines available for KSP1 that were considered OP, and they were not as OP as this engine is. It is overtuned to such a monstrous degree next to all other engines, there's just no comparison. I reckon this is our preview for what higher tech levels are going to be offering, at a game stage where the Kerbals have colonies all over the system and interstellar technology is close at hand.
• Let's not forget the Dawn ion drive, either. On the surface, it received a small nerf, in the sense that it needs a bit more energy to run now (10 EC/s instead of 8.74 EC/s). But just like the Nerv is benefitting from better tankage, so is the Dawn. Xenon tanks used to have a mass fraction of 4. Now, just like all other tanks, they're at 9. That means they contain more than two and a half times the amount of xenon for the same dry mass. You might not notice it that much when attaching only a single tank and getting a small few thousand m/s of dV; but it's gonna scale so much higher so much more easily. A single ion stage with 40,000m/s worth of dV would have been borderline impossible in KSP1 even without worrying about how to launch it; now in KSP2, it's not any harder to achieve than making a Terrier stage with 3,100m/s worth of dV.
• And remember, the perhaps biggest buff to low-TWR engines like the Nerv and Dawn: the ability to time warp during burns. I mean, once that actually works reliably But yeah, get used to the idea of working a lot more with really high dV deep space craft in the future. It's gonna be easier than ever before.

 

Bro…. There is no air pressure or heat currently in KSP2.  Of course the two are going to be different 

Edited March 12, 2023 by RaBDawG

[regex]

2 hours ago, JoeSchmuckatelli said:

Need to play around with it if it is working for you - but for me?  It's like instead of holding prograde and getting pulled by gravity into a turn - the SAS is looking way ahead for the PE marker and using it as a target.  (hence the flip) 

I've been using the prograde to get both rockets and spaceplanes into orbit, it generally works as expected. On some craft you have to watch for a later transition, I think somewhere around 40~50km altitude, where the SAS bugs out and decides to wander off. At that point just toggle it off and on. I haven't seen that one in a while so I'm of the impression it's craft-related.

[cocoscacao]

Whenever I try to increase pitch above 20 percent at 30km altitude + speed ~1400, my ssto flips violently and wings get torn apart.

Edited March 12, 2023 by cocoscacao

[darthgently]

20 minutes ago, cocoscacao said:

Whenever I try to increase pitch above 20 percent at 30km altitude + speed ~1400, my ssto flips violently and wings get torn apart.

You are stalling.  The craft is still in the atmosphere and if you pitch up too much the aero forces will do that

Edited March 12, 2023 by darthgently

[cocoscacao]

Stalling? At 1400m/s? I'm using caps-lock to toggle fine tuned controls. At 30 kilometers, I don't think aero-forces should be strong enough to flip me so violently for a steady 5 degrees pitch increase.

[Periple]

21 minutes ago, cocoscacao said:

Whenever I try to increase pitch above 20 percent at 30km altitude + speed ~1400, my ssto flips violently and wings get torn apart.

I think you may have a stubby part near the nose. That will move the center of pressure forward the faster you go. Once it moves past the center of mass your craft will become unstable and will want to flip like you describe, even if in the VAB your center of pressure indicator is behind the center of mass indicator. This happened to me pretty often in KSP1, and I think KSP2's aero model is less forgiving of stubby parts so it might be even more accentuated here. 

I haven't had any difficulties of this kind with my planes in KSP2, but I have made an effort to keep them pointy and keep any stubby bits near or behind the center of mass!

[cocoscacao]

2 minutes ago, Periple said:

I think you may have a stubby part near the nose

Mk 2 cockpit. Very basic plane, although my wings are rather wide... Still, I wasn't expecting something like that. In KSP 1, atmo becomes relatively benign after 17km mark. New game, new rules I guess...