Should Specific Impulse (ISP) be nerfed with improved aerodynamics?

[Red Iron Crown]

I'd be against an Isp nerf, it affects far more than just reaching orbit. Everything gets harder with less efficient engines.

Honestly, I figure the presumably reduced dV-to-orbit will be offset somewhat by requiring more mass (in the form of fairings, nosecones, and more engine mass to compensate for thrust scaling). That and it will become more challenging to fly to orbit assuming slamming over to 45 degrees at 10km.

Maybe the simplest solution would be to extend the atmosphere higher, like to around 150km or so. That would increase dV requirements without requiring a nerf or planet rescale.

[KSK]

Yes. For example, they have an exhaust pipe. Not sure where youi're getting SSME from that. >.>

I always figured the exhaust pipe was for roll control as per the SpaceX Merlin engines. Makes sense to have it there but yeah - not very SSME.

[Whirligig Girl]

Maybe, instead of even TRYING to make an attempt at making spaceflight directly analogous to KSP, they should accept their rescale and make the situation as realistic as possible given the assumptions of Kerbin being 1/10 of real scale.

Why? When I tried the 1/10 scale stock system mod, I decided that I would use all the physics-based realism mods that there were (FAR, DRE, etc), to see what it would really be like to be in a world like that. Maybe KSP might go in the same direction? (Not as far though.)

So you would embrace the low-speed re-entries and the tiny delta-v to orbit, and see where that leads you? Honestly though, I'm not a fan of that. People playing KSP try to do things that real space programs did to succeed. This means that spaceflight around Kerbin must be similarly challenging to spaceflight around Earth, even though there's a hugely different scale.

But how to do this? And to what extent? At this point, I'm kind of regretting the choice to make Kerbin 10% of Earth. I mean, I'm sure whatever happens will be fine, fun, and playable, but maybe it would've been better if KSP had been full scale from the start.

One thing that I've noted as a "problem" is that the Kerbal X is a Mun-landing-return rocket. It used to be a Mun landing only rocket, but then the Mainsail was buffed. A rocket that small, in my opinion, shouldn't be able to do more than a flyby of the Moon. It's just too small. I feel like my rockets should be bigger! The Saturn V was bigger!

The way I see it, there are a few ways we can go from here, ranked in some kind of order.

1: Don't nerf engines, ignore the fact that delta-v to orbit is 75% that of current soupospherical aerodynamics.

2: Nerf engine Isp in the atmosphere only.

3: Nerf engine Isp universally, but not quite as much.

4: Make the souposphere part of the aerodynamics overhaul.

5: Double the scale of the solar system.

--This has a few advantages.

--Mun now actually has a proper delta-v advantage to doing Munar Orbit Rendezvous compared to stock, where direct ascent is actually more efficient.

--The game's difficulty is not super hard, but it is harder.

--More challenges can be solved in a realistic way. Bigger rockets!

6: Increase the solar system's scale by 5x.

--Pretty darn hard.

--Rocket scale and solar system scale are roughly equal compared to real life.

--Might need a planet revamp to keep a high quality and detailed surface.

7: Increase the solar system's scale by 10x.

--Too hard for many players, potentially.

--Orbit requires more delta-v than a stock Duna landing under current physics.

--Spaceflight is analogous to real life in it's entirety.

--You would almost certainly need a revamp of the planets to bring their detail up to a good quality. Redoing planetary geographies even.

If you have proper monsters-of-rocketry instead of train-built stock parts, is 10x scale even really that much harder? Probably. It's certainly more time consuming. I think 2x would be the best option except it would mean rescaling the planets, which is a problem.

Overall, I think that a significant engine Isp nerf would be the most likely option. Just my 2 cents. I don't feel like arguing about it today, so if you disagree, you've already won the argument.

[chaos_forge]

I for one would be a fan of increasing the planets' sizes by 2x, but leaving ISPs the same.

[BudgetHedgehog]

Every time I read 'stock ÃŽâ€V to orbit, 4.4km/s, is balanced, and 3.5km/s isn't', I ignore the rest of the post. Who decided that 4.4km/s was correct and balanced? The devs, when they made the air behave like jelly. It's not correct for such a stupidly small planet as Kerbin and the only reason that arbitrary number exists is because the aerodynamic model was wrong and unfairly balanced* (nosecones increasing overall drag etc). An unfair* aero creates an unfair* ÃŽâ€V to orbit. 3.5km/s to orbit, while low, is what it should be for the size Kerbin is. Call it too low, unbalanced, whatever, but that's only because that's how the atmosphere should behave for such a small planet.

I don't care for fuel changes, it's fuel, it could be called Floober and Gabajee for all I care, all I need to know is that I need it to power my engines. Don't compare KSP to real life, don't even try because it has no relation to it. Kerbin is too small and the engines are underpowered. Only when Kerbin = Earth can you consider comparing stats to real life. Blah blah, nerf the Isp because for some reason, people are attached to an arbitrary 4.4km/s as "balanced" and won't be happy until that number remains the same even with a realistic atmosphere. Here's the scoop - you can only get that number with a realistic atmosphere by either making kerbin bigger or nerfing the engines across the board. Maybe actual realistic Isp will keep that number the same as well, I don't know, I've never used KIDS, but if it is the same, hooray, it's "balanced". Or, it's more realistic unbalanced and the only thing that will fix it (scale increase or Isp nerf) makes everything else harder. How about we wait and see what the actual ÃŽâ€V to orbit figure is before we start asking for nerfing? Because if it's 4.4km/s then something needs a buff because that number was arbitrary and wrong to begin with [insert comment about lack of release before 1.0 to check balance here].

In other words, wait and see. It's pretty much what Squad are doing anyway..

*when I say unfair, I mean it is more difficult than it should be. It's unbalanced and needs a buff, that kind of thing.

EDIT 2: Put me down for increasing the scale of the universe please.

Edited February 16, 2015 by ObsessedWithKSP

[Renegrade]

I'm not opposed to MODERATE size increases (upwards of 2.0x), nor am I opposed to Squad making it easier to mod the system (I'd like that very much. 3/4 of KSP is mods afterall). However... Full scale stock can stuff it. Go play Orbiter. I don't want to spend eight hundred thousand years getting into orbit, or requiring four hundred million parts to make a launcher.* Note that increasing scale is roughly the same as a global Isp nerf, as in either case, you'll need a bigger rocket to ALL destinations. Oh, with the important distinction that you aren't trying to simulate a 3cm wide antenna against a system that's 60 AU wide using a teensy tiny double-precision number.

* numbers may be exaggerated slightly for dramatic purposes. But only slightly.

--Mun now actually has a proper delta-v advantage to doing Munar Orbit Rendezvous compared to stock, where direct ascent is actually more efficient.

Wat? That has more to do with the lack of life support in stock than anything else. Since you don't need to bring both pods with stock for life support, the CSM-less Direct Ascent model can ditch the extra mass associated with that and be competitive easily..in all scales.

However, once you get into KSP career mechanics, using a CSM/LEM model starts turning a rather big profit when you send the research lab with it. Now, you can haul along an extra 3.5t lab module to munar orbit, with a comparatively TINY lander, hit a dozen biomes along the equator (or go for a polar orbit and hit ALL the biomes if you've brought enough fuel), all with only a single goo pod and a single science jr.

Direct Ascent:

600kg pod, 500kg science, misc bits. Has to go from LKO to the Mun, land, return, and back again. (860+300, 640, 640, 300). Using a 48-7S design(+100kg), that would take about 1.463t of fuel for a total mass of about 2,663.

2,663*10 biomes = 26,630kg

Mobile Lab CSM:

3,500kg lab, 500kg 909, misc bits. Has to go from LKO to low Mun orbit and return. 1,100kg lander. 5,410kg of lander fuel. (860+300+300). 3.329t fuel to move itself to the Mun with the lander+fuel, 326kg to return to Kerbin without lander and lander fuel.

4,000 lab + 1,200 lander + 5,410 lander fuel + 3,655 self-fuel = 14,256kg.

Mobile Lab LEM:

600kg pod, 500kg science, misc bits. Has to go to the Mun surface, land, and return to the CSM. 640+640. Using a 48-7S (+100kg) design, that would take about 0.541t of fuel per landing (using fuel from CSM).

Given that it's not too hard to reach LKO in stock air with a 16% payload fraction, that's 89.16t for the CSM/LEM design, or 166.44t for the Direct Ascent model.

Interesting tidbit: The mass of fuel from the Direct Ascent model is the same as the entire CSM/LEM design.

[Northstar1989]

I play with RSS 64K, and it's not THAT hard... The real-time-to-orbit doesn't really increase nearly as much as you think because, time warp. I routinely get to orbit in 5-8 minutes, which isn't that bad considering it's "halfway to ANYWHERE" (emphasis added) and *should* be a much bigger part of the challenge of the game. The bigger challenge in RSS 64K actually becomes not getting to orbit in the first place, but the GREATLY increased fuel-requirements to get from there to anywhere else. Mods like KSP-Interstellar help ENORMOUSLY with this, though.

Of course, I never expect the devs to up-scale Kerbin, even by a modest 2-3x. Which is why I suggested an ISP-nerf, to increase the game's difficulty. A reduction in fuel-density (without changing ISP) would also have the same effect though- maybe we assume that LF/O represents Hydro/LOX and *GREATLY* reduce the mass-per-liter of both LiquidFuel and Oxidizer to account for that. This way, you will still need larger rockets to get to orbit, but nothing has to be done to the engines, etc...

Regards,

Northstar

[NoMrBond]

I wonder if we could get a preview/WIP of the numbers Ted&Co have come up with for the balance pass?

It seems like it would be difficult to parse though without knowing how the improved aero and ISP mass flow correction are going to play into it

[Rath]

I think that if this got implemented you would get the realistic crowd into poodle should only work with hypergolics ect. If the devs do this you will kill my favorite launcher(I looked at real hypergolics and that won't work with what that launcher is for. (yes I DO use poodles, amazing right). There is a such a thing called too much realism.

[Scoundrel]

Interesting cognitive rationalizations in the OP and its respondents about an issue which I have spent the last two weeks figuring out (I'll eventually be blogging about when 1.0 comes out, but let's be honest, nobody really cares). Also I probably shouldn't have drunk a bottle of wine before replying, so this will likely end up being a big wall of text.

IMHO, the problem isn't what is and what isn't LF and O, or even that KSP engines follow stoichiometricly perfect operation throughout their performance envelope with thermal efficiencies bordering on 99%. The problem is that the engines blatantly flaunt the laws of thermodynamics in some really weird ways.

See, cognitively we understand that KSP engines don't equate to any real world analogues. We, as human beings, have a certain pattern recognition that kicks in when we start to educate ourselves on a subject that immediately senses incongruities... colloquially we call that our "BS detector."

What the OP and many of us have/are starting to notice is that the engines obviously fail to follow the various laws of thermodynamics, and each of us has a differing viewpoint as to where and what that failing is. The OP has what he/she thinks is an obvious answer (make the stock engines hypergolic engines) and others have their opinions (differing for various reasons), all of which are actually, IMHO, symptomatic of a system that is based on bias rather than science.

If we were to run the engines through the actual thermodynamic formulae used to design rocket engines, we would be shocked and flabbergasted at exactly how bent the engines are (I have actually done this, and yeah, they are very, very broken). This has nothing to do with the choice of fuels or needing real world analogues from which to draw our conclusions. Rather it reveals how flawed a system based on biases actually is, and how desperately we need objective, unbiased mathematically derived engines in this game.

See, the fact that oxidizer and fuel are volumetrically the same and share the exact same density actually isn't that relevant. Nor is the Isp values, which are arbitrary anyways. What is relevant is that the engines do not follow any form of logic or mathematical formulae in their execution. Engines in KSP have no Pe value, or even a specific power rating that follows a logical pattern, which are the core of any real engine comparison for anyone who knows anything about rocket engines. Instead we are dealt with arbitrary various ratings that are derived from "QA feedback".

Think about that for a moment.

The engines we will end up with in stock will be engines that a handful of people say "feels" like they're balanced... a result based on perception-based consensus rather than consistent numbers based on actual formulae. If their performance were derived from the actual thermodynamic formulae that we build real engines from (which is readily available), we would have a set of engines that even the most irrational of players would be hard pressed to find one to claim is OP. The engines would, by the inherent nature of thermodynamic principles, be balanced. In fact, they would be so balanced that we could apply subtle biases towards increased tech levels and even radial size that would feel like a logical progression in engine tech without making things remotely unbalanced, which I think is something that many of us would like to see.

So rather than argue about whether or not we need more than one type of fuel or oxidizer and the various merits/complications therein, IMHO, we should be asking for thermodynamically consistent engines and mechanics, and go from there.