[1.12.X] RealChute Parachute Systems v1.4.8.3 | 24/01/21

[AndreyATGB]

Come on don't start the hypetrain, it's hard to stop you know.

[Lazurkri]

Come on don't start the hypetrain, it's hard to stop you know.

Excessive use of explosion related pictures tends to derail that train. So does pictures of cats.

[power5000]

So will this change how you find your decent speed? like normal parachutes have a drag co of 500 (deployed) and a craft has .2 so you multiply by mass and take avg ect ?

[stupid_chris]

I don't understand whether the "new main" chutes are two-stage drogue+main parachutes... if not, I recommend those

Since lots of things seem to be in flux I think I'll wait for 0.23 to rebuild my modpack and add this one also, but great job!

There's four new parts who will be coming in the next update and they are main/drogue combos, yes.

Speaking of 0.23 I am thrilled of how the new tweakable system will work and I hope (not so) stupid_chris won't have problems make it compatible with RealChute

I'm not planning to use the tweakables system extensively. I've had a look at it and it does not allow the flexibility I need. Once .23 comes out, I'll see if I can enable them until I get the editor window together, but I won't delve more than that with them.

So will this change how you find your decent speed? like normal parachutes have a drag co of 500 (deployed) and a craft has .2 so you multiply by mass and take avg ect ?

The plugin doesn't use drag coefficient at all. You can forget all those 500 and 0.2, drag does not use this system. Part mass is also irrelevant to how much drag the part creates.

[Hyomoto]

I like the work you've done here, so this is just semantics. I hope no one else brought this up because I don't feel like beating a dead horse, but this is not 'more realistic'. I wear a parachute at my job, and the sudden opening is indeed the way they work. Once the streamer grabs a bite of air, it flies open and applies a very sudden, and very violent change to your speed. I haven't heard of any slow-deploying parachutes, though I'm sure some work has been done somewhere for that. In the GAME I think this is nice, but you might want to distance yourself from the idea that you've made them more 'realistic'. Perhaps more game functional, but not 'realistic'.

[stupid_chris]

I like the work you've done here, so this is just semantics. I hope no one else brought this up because I don't feel like beating a dead horse, but this is not 'more realistic'. I wear a parachute at my job, and the sudden opening is indeed the way they work. Once the streamer grabs a bite of air, it flies open and applies a very sudden, and very violent change to your speed. I haven't heard of any slow-deploying parachutes, though I'm sure some work has been done somewhere for that. In the GAME I think this is nice, but you might want to distance yourself from the idea that you've made them more 'realistic'. Perhaps more game functional, but not 'realistic'.

Parachute deployment never goes over 5Gs. If it does, you're screwed. I know this is not how they really work, but this is as good as it gets in this game.

The deceleration offered by my parachutes is realistic. The deployment itself, not so, but I have little control over this, cloth physics is really the last thing you want in KSP. The gradual deployment is a way of simulating the slider.

But parachutes in general are not that realistic in KSP. There's no such thing as a "predeloyed state" IRL.

As I said before, this is not a full reality mode. Else this would get complicated real fast, parachutes are not simple things. This is just an effort to stick a little closer to what you would expect from a parachute, and that is surely not +15G on deployment.

However, if you have tips and tricks you think would improve the system in general, feel free to PM me, I have no personal experience with parachutes and having input from someone who uses them frequently would be great

[XanderTek]

At the very least, RealChute is certainly using more realistic equations to determine drag.

[stupid_chris]

At the very least, RealChute is certainly using more realistic equations to determine drag.

It's using the real equation, the only thing that isn't really accurate is independant of me, and it's how KSP calculates air density.

[Goozeman]

It's using the real equation, the only thing that isn't really accurate is independant of me, and it's how KSP calculates air density.

Spacecraft parachutes have ... devices (I don't know the real term) to control the opening of the chute. Left to its own devices, the chute would just snap open. Take a look at this video of a Dragon capsule landing for the actual opening sequence.

As far as air density goes, the exponential atmosphere is first-order accurate. If you're using FAR, then your landing calculations have other errors that have far greater impact than the density. The exponential atmosphere misses some of the stratigraphy (troposphere, stratosphere, etc.), but we don't have weather, winds, or the coriolis effect going on anyways, so you're not missing much.

[stupid_chris]

Spacecraft parachutes have ... devices (I don't know the real term) to control the opening of the chute. Left to its own devices, the chute would just snap open. Take a look at this video of a Dragon capsule landing for the actual opening sequence.

Yeah, they spend more time before fully opening, but that's a very short state, unlike what we have in KSP. I believe this is also a slider controlling their deployments.

As far as air density goes, the exponential atmosphere is first-order accurate. If you're using FAR, then your landing calculations have other errors that have far greater impact than the density. The exponential atmosphere misses some of the stratigraphy (troposphere, stratosphere, etc.), but we don't have weather, winds, or the coriolis effect going on anyways, so you're not missing much.

What I meant is the air density in KSP is only dependant of pressure. Which is far from being right. It's also dependant of temperature and the partial pressure of other gasses in the air, like water vapor and such. We do have Coriolis effect though, the atmosphere rotates with the planet

[DerekL1963]

I hope no one else brought this up because I don't feel like beating a dead horse, but this is not 'more realistic'. I wear a parachute at my job, and the sudden opening is indeed the way they work. Once the streamer grabs a bite of air, it flies open and applies a very sudden, and very violent change to your speed. I haven't heard of any slow-deploying parachutes, though I'm sure some work has been done somewhere for that.

Google "parachute reefing" and be enlightened. It's a standard technique, dating back to the 1950's (at least), for limiting the rate at which parachutes open and thus controlling the forces involved.

[Goozeman]

Yeah, they spend more time before fully opening, but that's a very short state, unlike what we have in KSP. I believe this is also a slider controlling their deployments.

I think that's more an issue of people opening the parachutes at far to high an altitude. Theoretically, they could remain reefed that long, but that's what a drogue chute is for.

What I meant is the air density in KSP is only dependant of pressure. Which is far from being right. It's also dependant of temperature and the partial pressure of other gasses in the air, like water vapor and such. We do have Coriolis effect though, the atmosphere rotates with the planet

Water vapor only minutely affects the density of the air (~2%). The tables for dry air, then, are accurate to better than 5%, which is good enough for KSP. (Patched conics anyone?) This doesn't necessarily make the calculations wrong, just "less right" than a more accurate model. A full atmospheric model could be implemented fairly easily, but again, a single equation is "good enough." This equation takes all of the variables in the standard atmospheric model and collapses it to:

rho = rho_0 * exp[h/h_scale]

where rho is SSL density and h_scale is the scale height. Again, not perfect, but we're not doing laboratory quality calculations here. I've done mission architectures for spacecraft design, and this is more than good enough to get a general idea of what is happening on reentry. Other factors will introduce far more error than the atmo model, such as your Cd vs. M curve and the weather. The lift/drag model is orders of magnitude more egregious (completely inaccurate) than the atmo model (first-order accurate).

[stupid_chris]

Water vapor only minutely affects the density of the air (~2%). The tables for dry air, then, are accurate to better than 5%, which is good enough for KSP. (Patched conics anyone?) This doesn't necessarily make the calculations wrong, just "less right" than a more accurate model. A full atmospheric model could be implemented fairly easily, but again, a single equation is "good enough." This equation takes all of the variables in the standard atmospheric model and collapses it to:

rho = rho_0 * exp[h/h_scale]

where rho is SSL density and h_scale is the scale height. Again, not perfect, but we're not doing laboratory quality calculations here. I've done mission architectures for spacecraft design, and this is more than good enough to get a general idea of what is happening on reentry. Other factors will introduce far more error than the atmo model, such as your Cd vs. M curve and the weather. The lift/drag model is orders of magnitude more egregious (completely inaccurate) than the atmo model (first-order accurate).

Yeah, that's the equation the calculator I did uses. But once you go off Kerbin, the atmosphere should be made of different components, and it is at different temperatures, and having the same equations on those planets can get pretty innacurate.

[Goozeman]

Yeah, that's the equation the calculator I did uses. But once you go off Kerbin, the atmosphere should be made of different components, and it is at different temperatures, and having the same equations on those planets can get pretty innacurate.

I see your point, but even the atmosphere of Venus (Eve?) is 92% CO2. Whether or not that 8% of "other" makes a significant difference or not, I don't know. Given that it's sulfuric acid rain/vapor, it very well could.

Also, if anything, Duna's atmo is more uniform, being largely CO2 with traces of other things, so the exponential atmo should work there.

Jool is a whole other can of worms. There's no way you could get that close to Jupiter without frying electronics anyways.

Anyways, so long as the scale height is adjusted for each planet (and I'm pretty sure it is), the model should be relatively accurate.

[stupid_chris]

I see your point, but even the atmosphere of Venus (Eve?) is 92% CO2. Whether or not that 8% of "other" makes a significant difference or not, I don't know. Given that it's sulfuric acid rain/vapor, it very well could.

Also, if anything, Duna's atmo is more uniform, being largely CO2 with traces of other things, so the exponential atmo should work there.

Jool is a whole other can of worms. There's no way you could get that close to Jupiter without frying electronics anyways.

Anyways, so long as the scale height is adjusted for each planet (and I'm pretty sure it is), the model should be relatively accurate.

They are supposed to be indeed. It could be something to add to my todo list eventually to try to figure correct atmospheric densities for each planet

[Goozeman]

They are supposed to be indeed. It could be something to add to my todo list eventually to try to figure correct atmospheric densities for each planet

To get you started, my notes say that Mars' atmo is 0.015 kg/m^3 at the surface and the scale height is ~11km. Don't know how that would translate to KSP, though.

[stupid_chris]

Mars's atmosphere has a pressure of about 0.01atm ASL if I'm not mistaken, while Duna has 0.2 atm ASL. I think the hardest part will be coming with an accurate temperature model.

[Aknar]

What will the tweakable system involve for this mod? I'm sure you've seen you can set the pressure at which the parachute will fully deploy and altitude at which parachute is automatically deployed now. Is it gonna cause issues? Do you think you'll be able to work directly with this (people where worried about drogue chutes being useless now except for the small extra drag hey have when they aren't fully deployed yet)?

[stupid_chris]

What will the tweakable system involve for this mod? I'm sure you've seen you can set the pressure at which the parachute will fully deploy and altitude at which parachute is automatically deployed now. Is it gonna cause issues? Do you think you'll be able to work directly with this (people where worried about drogue chutes being useless now except for the small extra drag hey have when they aren't fully deployed yet)?

I don't plan on using the tweakables extensively. I've already had access to them and they don't offer the versability I need. I'll look at the documentation Mu writes up when .23 comes out and I'll push an update containing a few new features as well as support for tweakables, but as soon as the editor window is complete I'll drop them.

[Goozeman]

Mars's atmosphere has a pressure of about 0.01atm ASL if I'm not mistaken, while Duna has 0.2 atm ASL. I think the hardest part will be coming with an accurate temperature model.

I guess that's where I'm confused. Pressure doesn't really mean anything to aerodynamic calculations. It's all about density and relative changes in pressure due to motion, not absolute pressure.

As far as temperature modelling goes, talk to Farram4. Just watching the Mach number readout in the FAR mod, it seems that he has done some good work with temperature.

[stupid_chris]

That's the equation of air density, and it is a function of temperature actually.

Density = pressure / R * Temperature.

I'm in contact with ferram to add some more compatibility with RealChute/FAR, so I'll look into it.

[Spanier]

Is there a difference between arming and deploying a parachut in your mod?

[stupid_chris]

Is there a difference between arming and deploying a parachut in your mod?

Arming makes it deploy as soon as it can, while deploying is instantaneous. If it fails, the parachute will go back to the staging list and be deactivated.

[Tommygun]

Arming makes it deploy as soon as it can, while deploying is instantaneous. If it fails, the parachute will go back to the staging list and be deactivated.

I tried out the Arming method the other day coming down to Kerbin and it deployed both the drogue and main chutes before the thermal effects happened.

Is it supposed to deploy that far up?

[stupid_chris]

I tried out the Arming method the other day coming down to Kerbin and it deployed both the drogue and main chutes before the thermal effects happened.

Is it supposed to deploy that far up?

It deploys as soon as it can. In that case, drogue predeployment is most likely 45km and main 40km. Arming on Kerbin isn't of much use honestly.