Realism in KSP

[Red Iron Crown]

KSP should also have correct thrust. Isp does not affect fuel flow, it affects thrust.

This is one of the easier to implement suggestions from your infamous list (it's infamous now, right?). Somehow it got lost in all the noise of "OMG regex wants to rescale the universe!", but it's a good, simple, realistic change.

[Renegrade]

This is one of the easier to implement suggestions from your infamous list (it's infamous now, right?). Somehow it got lost in all the noise of "OMG regex wants to rescale the universe!", but it's a good, simple, realistic change.

Yes, it's absurdly simple to implement, I would very much like to see a thrust corrector implemented. It's maybe three lines of code, and they might be able to hit that g0 bug at the same time..

[SunChaser]

This discussion reminds me of the 'nerf lobby' in Paradox games--some of my favorites. A whole bunch of people feel a feature (or lack thereof) makes the game too easy/difficult, kills immersion, etc. but if patches alter the difficulty of the game dramatically, people might just not update the game...and then show up on the forums complaining about balance issues and bugs that were fixed a year ago (hello Crusader Kings II).

[tater]

Cold shouldn't be a factor. If some areas of the ship are supposed to be exposed to it, it can be assumed they are equipped with a Radioactive heat generator (sort of an rtg but for heat). Since that's a passive system, no player interaction is required.

Oxygen for breathing is recycled from co2 (generated by breathing). That's also passive so, like urine, it can perfectly well be abstracted

Cold isn't really a problem for occupied habitats with a power source in space. The only heat loss is via direct radiation to space,a nd unless you have a structure designed for way more people than actual occupants, or run out of power in a module designed to be a great passive radiator (like the Apollo LEM), cold should not be a problem, usually the opposite. We'd likely assume that habitats are designed to radiate the correct amount for their maximum capacity, with some slop.

[regex]

This is one of the easier to implement suggestions from your infamous list (it's infamous now, right?). Somehow it got lost in all the noise of "OMG regex wants to rescale the universe!", but it's a good, simple, realistic change.

The funny thing is that list is just a collection of a bunch of other people's gripes that I collected and agreed with (well, aside from re-scaling, but we all know that isn't happening in stock). And thrust correction is important; you could rely on the rocket equation for lifters if it was fixed.

This discussion reminds me of the 'nerf lobby' in Paradox games--some of my favorites. A whole bunch of people feel a feature (or lack thereof) makes the game too easy/difficult, kills immersion, etc. but if patches alter the difficulty of the game dramatically, people might just not update the game...and then show up on the forums complaining about balance issues and bugs that were fixed a year ago (hello Crusader Kings II).

Any change is difficult, especially in an early access game but there are plenty of little things that KSP needs to have fixed, things that should have been done in the first place. After that, well, the community is already split and you're never going to be able to please everyone, but it would be really nice to have a NEAR-equivalent in stock so that newbies can rely on real-world examples. Plus other nods to "realism" that people expect (reentry heat is a big one).

[Red Iron Crown]

And thrust correction is important; you could rely on the rocket equation for lifters if it was fixed.

Does scaling fuel consumption rather than thrust reduce the rocket equation's usefulness for lifters? How so?

[regex]

Does scaling fuel consumption rather than thrust reduce the rocket equation's usefulness for lifters? How so?

Look at Engineer, for instance; it has an atmospheric value for delta-V when it shouldn't (TWR should change in atmosphere, not delta-V). Rockets have a certain delta-V value and that doesn't change in atmosphere versus space. You may get drag and gravity losses, but the change in velocity that a craft can make is determined by the rocket equation. That doesn't hold true for KSP because fuel flow is affected by isp in atmosphere, meaning that you have two (actually, infinite based on pressure curve) delta-V values. When designing a lifter you have to check both the atmospheric and space delta-V and hope you have enough. Experienced players already compensate for this, but new players can't rely on math to get them to orbit. Where one calculation would serve, you have to do two and take an average.

E: I AM TOTALLY WRONG HERE!

Edited September 3, 2014 by regex

[Red Iron Crown]

Look at Engineer, for instance; it has an atmospheric value for delta-V when it shouldn't (TWR should change in atmosphere, not delta-V). Rockets have a certain delta-V value and that doesn't change in atmosphere versus space. You may get drag and gravity losses, but the change in velocity that a craft can make is determined by the rocket equation. That doesn't hold true for KSP because fuel flow is affected by isp in atmosphere, meaning that you have two (actually, infinite based on pressure curve) delta-V values. When designing a lifter you have to check both the atmospheric and space delta-V and hope you have enough. Experienced players already compensate for this, but new players can't rely on math to get them to orbit. Where one calculation would serve, you have to do two and take an average.

I must be missing something. Isp does change with atmospheric pressure, so it is proper and correct that in atmosphere the delta-V value would change. The rocket equation does not care about fuel consumption or thrust, only Isp. If I understand it correctly, the dV calculations would not change at all if thrust scaling were implemented (though TWR calculations certainly would).

[cantab]

Delta-V is lower in atmosphere since specific impulse is lower in atmosphere, because the ambient air impedes the rocket exhaust. It's for the same physical reasons as the thrust being reduced given constant fuel flow (which is the norm in real rockets).

Indeed, realistically making Isp loss in atmosphere affect thrust would make rocket design more complicated, since you would now have separate atmospheric and vacuum TWR as well as dV. Not that the complexity is reason to not do it.

[juanml82]

BTW, regarding greenhouses, which have been mentioned, how is that supposed to work in reality? Say a mission to Mars.

You can grow plants using hydroponics in space. That means plants would take energy, maybe from the sun, maybe from artificial sources, water (on which they are placed), and nutrients and would then transform them into fresh food. Which likely has a positive effect in the astronauts morale and psychological standing, as they are working in the greenhouses and eating fresh food instead of preprocessed food.

But, considering that you need to pack the mass the plants will transform into food into the ship in the first place, isn't a lot more efficient, from a mere delta-v standpoint, to pack preprocessed food instead, which will take less space and, therefore, ought to weight less?

The only way a layman like me can think greenhouses could have a positive effect on delta-v is if, upon arrival to destiny (let's say, Mars), the plants are taking their water and nutrient from Martian soil. That way, the ship will be carrying seeds, containers and tools, but water and nutrients are gathered in situ. Of course, that would seem to bring the problem of whether Earth plants can use Martian soil to grow and turn it into food.

Which means, regarding KSP, that it would seem that "realistic" greenhouses would have to be inefficient while traveling (ie, they weight a lot more than a similar clockdown timer in food), but they do become effective in long term bases. After all, we can assume Minmus soil isn't just fertile, it actually makes vegetables taste sweeter! But, then again, they might be useless beyond Dres, as there isn't enough sunlight to allow photosynthesis, or it significantly reduces yield.

[cantab]

On greenhouses, the advantage in principle is that the plants grow from the waste products produced by the crew - carbon dioxide in breath, nitrogen compounds in urine, and miscellaneous organics in faeces.

[regex]

I must be missing something. Isp does change with atmospheric pressure, so it is proper and correct that in atmosphere the delta-V value would change. The rocket equation does not care about fuel consumption or thrust, only Isp. If I understand it correctly, the dV calculations would not change at all if thrust scaling were implemented (though TWR calculations certainly would).

Well, then I am wrong and fail at math (not like that's anything new).

[juanml82]

On greenhouses, the advantage in principle is that the plants grow from the waste products produced by the crew - carbon dioxide in breath, nitrogen compounds in urine, and miscellaneous organics in faeces.

I see (10 char)

[Motokid600]

How accurate is KIDS when it comes to the isp/thrust curve? Because I gotta say having ksp effect TWR instead of fuel flow DOES introduce some complex variables. For instance when I'm using FAR without KIDS all my rockets have a 1.45twr at the pad. All of them. And that worked every time.

With KIDS.. it's a whole new ball game. Which brings me to a question now that I think about it. In stock KSP TWR do in fact increase as you ascend. As fuel drains the craft gets lighter and the TWR gets higher. So.. with KIDS. And in real life.. not only us the rockets mass decreasing, but the isp is also increasing, yes? Which.. makes TWR increae WAY more then with stock ksp? I'm confused as to the exact difference. Because when using KIDS my TWRs are out of control.

[Sky_walker]

Whoever renamed this topic - THANK YOU!

[tater]

BTW, regarding greenhouses, which have been mentioned, how is that supposed to work in reality? Say a mission to Mars.

You can grow plants using hydroponics in space. That means plants would take energy, maybe from the sun, maybe from artificial sources, water (on which they are placed), and nutrients and would then transform them into fresh food. Which likely has a positive effect in the astronauts morale and psychological standing, as they are working in the greenhouses and eating fresh food instead of preprocessed food.

But, considering that you need to pack the mass the plants will transform into food into the ship in the first place, isn't a lot more efficient, from a mere delta-v standpoint, to pack preprocessed food instead, which will take less space and, therefore, ought to weight less?

The only way a layman like me can think greenhouses could have a positive effect on delta-v is if, upon arrival to destiny (let's say, Mars), the plants are taking their water and nutrient from Martian soil. That way, the ship will be carrying seeds, containers and tools, but water and nutrients are gathered in situ. Of course, that would seem to bring the problem of whether Earth plants can use Martian soil to grow and turn it into food.

Which means, regarding KSP, that it would seem that "realistic" greenhouses would have to be inefficient while traveling (ie, they weight a lot more than a similar clockdown timer in food), but they do become effective in long term bases. After all, we can assume Minmus soil isn't just fertile, it actually makes vegetables taste sweeter! But, then again, they might be useless beyond Dres, as there isn't enough sunlight to allow photosynthesis, or it significantly reduces yield.

You have to remember a couple things. One, human (erm, kerbal) waste. A reason for hydroponics is to reuse organic waste, feeding the plants (which can be eaten, and turned into more waste), while simultaneously creating drinking water. The other is timing. It depends entirely on how long the mission is supposed to be. For shorter missions, it's not be that useful. For a continuously inhabited base, it's a big deal.

I'd imagine greenhouses (they'd likely use lights, with PV panels or other for power) for bases, really large stations, and possibly long-duration flights with habitat modules (distant system would need nukes for power anyway, solar won't cut it).

Edited September 3, 2014 by tater

[NathanKell]

How accurate is KIDS when it comes to the isp/thrust curve? Because I gotta say having ksp effect TWR instead of fuel flow DOES introduce some complex variables. For instance when I'm using FAR without KIDS all my rockets have a 1.45twr at the pad. All of them. And that worked every time.

With KIDS.. it's a whole new ball game. Which brings me to a question now that I think about it. In stock KSP TWR do in fact increase as you ascend. As fuel drains the craft gets lighter and the TWR gets higher. So.. with KIDS. And in real life.. not only us the rockets mass decreasing, but the isp is also increasing, yes? Which.. makes TWR increae WAY more then with stock ksp? I'm confused as to the exact difference. Because when using KIDS my TWRs are out of control.

What do you mean by "how accurate"? Either Isp determines thrust (as in reality, i.e. accurate) or it determines fuel flow (as in KSP, not accurate). There aren't degrees of accuracy here.

[cantab]

How accurate is KIDS when it comes to the isp/thrust curve? Because I gotta say having ksp effect TWR instead of fuel flow DOES introduce some complex variables. For instance when I'm using FAR without KIDS all my rockets have a 1.45twr at the pad. All of them. And that worked every time.

With KIDS.. it's a whole new ball game. Which brings me to a question now that I think about it. In stock KSP TWR do in fact increase as you ascend. As fuel drains the craft gets lighter and the TWR gets higher. So.. with KIDS. And in real life.. not only us the rockets mass decreasing, but the isp is also increasing, yes? Which.. makes TWR increae WAY more then with stock ksp? I'm confused as to the exact difference. Because when using KIDS my TWRs are out of control.

I don't know how close to reality KIDS is, but I know that many real rockets have to throttle down to avoid destroying the craft from aerodynamic stress, the point of highest stress being known as "Max Q". For the Space Shuttle the main engines and boosters dropped to about 2/3rds thrust at a certain point in the flight to keep the stresses under control. Rockets may also need to throttle down to keep the g-forces or other potential issues under control; the Saturn V outright shut down the centre engines on both first and second stages during its flight for this.

[Franklin]

I don't know how close to reality KIDS is, but I know that many real rockets have to throttle down to avoid destroying the craft from aerodynamic stress, the point of highest stress being known as "Max Q". For the Space Shuttle the main engines and boosters dropped to about 2/3rds thrust at a certain point in the flight to keep the stresses under control. Rockets may also need to throttle down to keep the g-forces or other potential issues under control; the Saturn V outright shut down the centre engines on both first and second stages during its flight for this.

Adding a red-light-flashing "slow down to avoid breaking up" element to launches would be amazingly fun.

[Motokid600]

What do you mean by "how accurate"? Either Isp determines thrust (as in reality, i.e. accurate) or it determines fuel flow (as in KSP, not accurate). There aren't degrees of accuracy here.

It's hard to describe exactly what I mean, but basically... What's the difference between using KIDS and not using KIDS? Because even without it your TWR does increase as you burn fuel and get lighter. When using KIDS the TWR raises much faster. And that's the only difference I can see between using KIDS and not...

The reason why I ask is because how such a feature ( isp governing thrust ) changes the gameplay by adding in more variables. With KIDS you cannot rely on a static TWR on the launch pad to get all your rockets to orbit. With KIDS your starting TWR needs to be much lower and if your using SRBs you gotta limit their throttle by over 75% and they STILL over accelerate my crafts not long after launch.

Now I'm not looking for a "how to play with KIDS" explaination. It's just that there's a whole lot more trial and error when using the mod. So if introduced into the stock game were gonna have people wondering how to launch their rockets all over again. I was completely fluent with FAR until installed KIDS. I had to damn near relearn how to go about my engine and launch profiles completely.

[Guest]

Exactly. Now you learned how it's done in the real world. As opposed to KSP's just plain wrong model. For someone who didn't learn KSP, but knew a thing or two about real rockets, it'll be more intuitive. For a complete newbie, it'll make no difference, he'll learn to do it the "right" way from get-go.

[NathanKell]

Also, the tools that *do* tell you what your TWR is (like MechJeb and KER) *are* aware of thrust correction, so there's no guessing involved at all. (At least with RealFuels; not 100% sure about KIDS).

Finally, as I said above and as Dragon01 said, there are no gradations in accuracy between "fuel flow is governed by Isp, thrust is constant" and "thrust is governed by Isp, fuel flow is constant."

The former is 100% inaccurate. The latter is 100% accurate.

Besides, do you think the turbopump Pump! Faster! at sea level or something? And for the ion engine, does the engine get fed a thousand times more xenon?

[Motokid600]

Exactly. Now you learned how it's done in the real world. As opposed to KSP's just plain wrong model. For someone who didn't learn KSP, but knew a thing or two about real rockets, it'll be more intuitive. For a complete newbie, it'll make no difference, he'll learn to do it the "right" way from get-go.

Which is absolutely great. I wish I would've picked up KIDS a lot sooner.

Also, the tools that *do* tell you what your TWR is (like MechJeb and KER) *are* aware of thrust correction, so there's no guessing involved at all. (At least with RealFuels; not 100% sure about KIDS).

I wish that maybe one day KER/MJ can display a graph of the actual thrust/isp curve showing me where those values will be at what altutde/speed in the VAB.

Finally, as I said above and as Dragon01 said, there are no gradations in accuracy between "fuel flow is governed by Isp, thrust is constant" and "thrust is governed by Isp, fuel flow is constant."

The former is 100% inaccurate. The latter is 100% accurate.

Correct me if im wrong.. when playing stock ksp I haven't used KER/MJ in awhile. But the TWR in stock KSP does actually rise as you burn fuel, no?

Besides, do you think the turbopump Pump! Faster! at sea level or something? And for the ion engine, does the engine get fed a thousand times more xenon?

I leanred about how it works in real life not longer after installing FAR and just reading up on how rocket engines work in general. How they work in KSP ( particuallry with stock Kerbin. Ive yet to try RSS yet. Soon... ) with said mods.. not so much.

Edited September 4, 2014 by Motokid600

[juanml82]

Correct me if im wrong.. when playing stock ksp I haven't used KER/MJ in awhile. But the TWR in stock KSP does actually rise as you burn fuel, no?

Right, but not because your thrust increases but because your weight decreases

[NathanKell]

TWR != thrust. TWR = thrust-to-weight ratio, and is usually rendered as thrust-to-mass*g0-ratio for a constant metric of comparison.