KSP 1 exploits (useful bugs) that you do OR don't want to be in KSP 2

[SciMan]

Oh boy that's another thing I don't want returning from KSP 1. The idea that no matter what you do the drag forces must make the thing act like a parachute.
It's not just wrong, it's not realistic enough.

Why don't I want that returning? It's quite easy to answer that, to be honest.

No sane spacecraft IRL would be designed to use an inflatable heat shield and then (as the picture in the post above this shows) 2 more on outriggers behind the center-of-mass to make it passively stable.

If I can make my entire spacecraft fit behind an inflatable heat shield, I shouldn't need "drogue heatshields" to stabilize it. It should be stable by the fact that the rest of the craft is in the massive low-pressure zone created by the heat shield. This should mean that the craft will STAY in that orientation despite occasional minor perturbations, instead of having an irresistible urge to swap ends and put the heat shield at the back of the craft, right where it can't do the very job it was designed to do.

Not only is the KSP 1 behavior of the inflatable heat shield nonsensical and aerodynamically wrong, it makes the part useless if you use only one (unless you put a stupid number of fins on the rear of the craft to offset the rather stupid (too high) amount of drag that the heatshield creates).

In other words, yes it's built like an asbestos bouncy castle. But it shouldn't act like a parachute, because that's not what it is. It's a heat shield, it goes first thru the atmosphere, then whatever it's protecting from the thermal extremes of atmospheric reentry goes behind that. That's just common sense, it's a heat shield, it should "shield" from "heat". But if it's stuck to the back (or what is now the back) of the craft, it can't really do that, now can it?

To be honest, I think that this is a case where something has to be "unrealistic to be realistic".
It's a heat shield.
If it has to be aerodynamically unrealistic to be functionally realistic (aka not making your craft flip ends), well then something's wrong with your physics simulation, isn't it?

[t_v]

1 hour ago, SciMan said:

To be honest, I think that this is a case where something has to be "unrealistic to be realistic".
It's a heat shield.
If it has to be aerodynamically unrealistic to be functionally realistic (aka not making your craft flip ends), well then something's wrong with your physics simulation, isn't it?

In. real life, spaceships like pods need to be engineered to not flip when reentering. If you have a giant noodle attached to your heat shield, I would expect it to flip. If you build stuff like small landers/rovers with a low center of mass, the whole thing is pretty much stable in KSP (although I would like them to add more faces to the heat shield drag model so that when it starts tipping, the face that is tipping towards prograde generates more drag to correct). Think about it in terms of cross-sectional area: this heat shield is one of the largest parts on the craft, therefore it is hitting a lot of air and pushing backwards on the craft. if your craft starts leaning at a 45 degree angle, what do you think will contribute more torque to the craft, the smaller parts on one end of your unreasonably long lander, or the gigantic surface on the other?

If you want to, think of it like a short, empty fuel tank of the largest diameter. A part like that isn't going to drag any less because it's at the front of the ship, even if it is performing a crucial role there. If you want to keep that big empty fuel tank at the front of the ship even though the drag/mass ratio is highest on that part, you'll need to design with a low center of mass, or add tons of fins, or a few really really big fins, or parachutes, or add more large surfaces in the back. When reentering, streamlined flow isn't something to be considered; it is just a matter of how much surface area you have times how much air is hitting per unit area, and in that respect, those giant heat shields are almost always going to flip a thin, noodle craft. If you design your craft with large diameter parts, you'll see that the drag can indeed balance out and the heat shield will not end up in the back all the time. 

this being said, I would love to see some high-temperature drogue chutes later in the tech tree so that I can land my spaghetti bases while keeping the benefits of large heat shields. The thing you seem to be taking issue with is not a product of the physics simulation but about the combination of limited parts in KSP 1 and poor craft design

[Pthigrivi]

Which brings me to one of my most desperate asks for years and years: ballutes. All that aerocapture energy is practically free! You can use it to capture around Duna or Eve, enter a useful orbit around Jool by burning through Laythe's atmosphere, and on all return missions to Kerbin. When you get into big awkward payloads with starter colony tech the option to pull the center of drag way back would open up a much greater design window. 

[darthvader15001]

ok we need the kal-1000 for overklocking engines when  you need just 1 more kn to launch or just to burn up in the atmosphere 

Edited July 19, 2022 by darthvader15001

[SciMan]

Alright well the solution to my problem is indeed "more parts" or at least more variety in parts. Ballutes would help (while being realistic) as would just normal heat shields that are bigger.

Because 99% of the time, I don't need the inflatable heat shield because I need to save mass. I need it because I need a really large heat shield, and the inflatable one happens to be the largest one available.
An ablative one would do just fine, it's just they aren't in the game in a large enough diameter.

So, procedural heat shields would be nice.

And no, I don't tend to build "noodle" craft. I'm landing colony modules, I'm not trying to aerobrake at Jool or Laythe.
These colony modules have a length-to-diameter ratio that tops out at maybe 3:1, and I do my best to put the heaviest parts closest to the heat shield (such as full fuel tanks that will be used for landing, I've even tried a cluster of 6 full large ore tanks purely as ballast with the heat shield attached directly to the core part that those ore tanks attach to).
Heck, I even test in water to make sure that the balance is right (without the heat shield deployed).
Unfortunately, reliably, when it comes time to reenter, the thing flips end-for-end and burns up. Despite me doing everything right.
I'll wait for you to explain why when I did everything right it still doesn't work.
My simple explanation is that the cone shape of the inflatable heat shield is too flat, so you can't nestle something heavy deep within the cone to make the passive stability work right.
That's why I said it might be a case of where it has to be unrealistic to be realistic.

That other bit about changing the drag model so that it isn't just a flat plate face-on to the oncoming atmosphere might also help somewhat, because currently if it gets even a little bit off-axis to the incoming airflow it will tend to cause forces that work to increase that angle, until again, the heat shield is facing the wrong way.
Because it is a well known fact that a flat plate (of any shape, round square triangle other polygons doesn't matter) is incapable of being stable in flight when the oncoming atmosphere is directed at one of the large flat faces of the plate (aka flat-on not edge-on, = plate starts flipping end-for-end all the way till impact). Even edge-on, without a little rotation to give it some dynamic stability that type of shape will still not be passively stable in the atmosphere (this is why you need to spin a Frisbee when you throw it).

[t_v]

Sorry for assuming your problem was due to extreme design, I just see this problem happen too many times specifically due to poor choices in craft design. It is true that not only do you have to avoid one extreme in construction, you have to actively go to the other extreme to have it be reasonably stable (enough that SAS can stabilize), and that is an issue. I do think that a better drag model could by itself fix the problem, and parts like Ballutes (Thanks Pthigrivi for introducing me to that interesting concept!) would ensure additional stability even in long craft. 

[magnemoe]

On 7/18/2022 at 7:47 PM, SciMan said:

Oh boy that's another thing I don't want returning from KSP 1. The idea that no matter what you do the drag forces must make the thing act like a parachute.
It's not just wrong, it's not realistic enough.

Why don't I want that returning? It's quite easy to answer that, to be honest.

No sane spacecraft IRL would be designed to use an inflatable heat shield and then (as the picture in the post above this shows) 2 more on outriggers behind the center-of-mass to make it passively stable.

If I can make my entire spacecraft fit behind an inflatable heat shield, I shouldn't need "drogue heatshields" to stabilize it. It should be stable by the fact that the rest of the craft is in the massive low-pressure zone created by the heat shield. This should mean that the craft will STAY in that orientation despite occasional minor perturbations, instead of having an irresistible urge to swap ends and put the heat shield at the back of the craft, right where it can't do the very job it was designed to do.

Not only is the KSP 1 behavior of the inflatable heat shield nonsensical and aerodynamically wrong, it makes the part useless if you use only one (unless you put a stupid number of fins on the rear of the craft to offset the rather stupid (too high) amount of drag that the heatshield creates).

In other words, yes it's built like an asbestos bouncy castle. But it shouldn't act like a parachute, because that's not what it is. It's a heat shield, it goes first thru the atmosphere, then whatever it's protecting from the thermal extremes of atmospheric reentry goes behind that. That's just common sense, it's a heat shield, it should "shield" from "heat". But if it's stuck to the back (or what is now the back) of the craft, it can't really do that, now can it?

To be honest, I think that this is a case where something has to be "unrealistic to be realistic".
It's a heat shield.
If it has to be aerodynamically unrealistic to be functionally realistic (aka not making your craft flip ends), well then something's wrong with your physics simulation, isn't it?

I assume you refer to my hard brake image. 
This had some practical problems as in I had to redesign the base in flight to be able to handle the aerocapture. First issue is that its mass is not totally centered on the base, yes its no problem to fly it but at an 7 g brake the force is 7 times stronger wile the twr on the base is probably around 0.5 g. 
Drag is even more non centered as it was not an priority during design, in short the two rear heat shields was not enough to keep it from tumbling and exploding. 

I did test this base in sandbox once I realized how fast it would come in, found how I could center the drag forces enough to work and had kerbals move stuff around. 
If the base and rest was inside an fairing it would worked much better as an fairing increases drag if off center making it self stabilizing, more so on something long, however it would not work in KSP as the base was launched from KSC inside an fairing but then it had to go to Minmus to stock up on fuel and ore. The tug at the rear was launched as an 3rd stage on an rocket who had the two rear heat shields added in orbit this rocket was then refueled in Minmus orbit.