Engine Rebalances

[Whirligig Girl]

One of the things coming in beta is purported to be rebalancing. A few threads have suggested things to make balances to. Also, I'm assuming this will be implemented because of course it is.

KR-2L Advanced Engine: [d]Remove high Vacuum Isp. like really though. Seriously. It's clearly an F-1 Engine, so why the heck does it's efficiency rival the SPACE SHUTTLE MAIN EFFING ENGINE?? (KS-25/RS-25). Now we'd need a lower thrust J-2 Engine (Or J-2X engine, because that's be related to the Space Launch System theme of the Kerbodyne parts). Lower it's thrust A LOT. If it's supposed to be a J-2 or J-2X, why in Kraken's name is the thrust so high?

LV-N Atomic Rocket Motor: Make it cost A LOT, and move it back in the tech tree.

KS-25x4 Engine Cluster: Make it a 3.75m to 1.25mx4 adapter-fuel tank, and make the KS-25 engines standalone 1.25m parts of EXTREME COST. (I.E., a total KS-25 4x cluster on a 3.75-1.25x4 tank adapter would cost a bit more than the engine currently does. Making the KS-25s standalone would also allow use of them on Space Shuttles, and also WE MUST HAVE EXTREME GIMBAL CONTROL.

Toroidal Aerospike: Increase it's cost, and also it's thrust.

The two Rockomax probe engines: Lower their Isp and thrust, so that they're not the go-to Eve Launch Engine. That really should be the Aerospike.

O-10 Monopropellant Engine: Increase size, cost, mass, and thrust. Make it a valid dual-engine solution for the Orbital Maneuvering System on the shuttle. Either that or keep this the same and make the Mark 55 Radial Engine a monoprop motor.

RT-10 Solid Rocket Booster: Decrease it's burn time by adding MOAR THRUST! Make it a VERY quick burning, VERY high thrust motor, and maybe decrease it's Isp as well. Make it's burn time half of what it currently is, and around 2 times more powerful. Make it a dangerous piece of BOOST. BOOST YOUR BOOSTERS FOR MAXIMUM BOOST

http://i.imgur.com/HAQfHrp.png

http://i56.tinypic.com/nvcj0k.jpg

http://i.imgur.com/GF1No.jpg

Not only would gameplay ++, but it would also create new challenges like "Get to Circular-ish orbit with only RT-10s and no thrust/fuel balancing."

Edited November 28, 2014 by GregroxMun

[Bill Phil]

How is the KR-2L an F-1? It's an oversized J-2 because it needs to fit the 3.75 meter parts mainly for aesthetic reasons. Plus, KR-2L, it has a 2 in its name.

I agree with most of this stuff, however.

Although the RT-10 thing is a bit weird. But even if you do double it's default thrust, people could still lower it to 50 percent, as in it becomes more versatile as an engine.

[Whirligig Girl]

Look at it. It looks like an F-1. It has high thrust like an F-1. It has low atmosphere efficiency like an F-1.

[King Arthur]

Certainly looks far more similar to the J-2X than the F-1 if you ask me. The J-2X was intended as an upper-stage engine to be used for such things like transfer burns, so that goes well with the KR-2L's ridiculously good vacuum ISP.

[NathanKell]

I rest my case.

[Jouni]

KS-25x4 Engine Cluster: Make it a 3.75m to 1.25mx4 adapter-fuel tank, and make the KS-25 engines standalone 1.25m parts of EXTREME COST. (I.E., a total KS-25 4x cluster on a 3.75-1.25x4 tank adapter would cost a bit more than the engine currently does. Making the KS-25s standalone would also allow use of them on Space Shuttles, and also WE MUST HAVE EXTREME GIMBAL CONTROL.

The KS-25 engines are definitely not 1.25 m engines. They're about the same size as the Skipper without its oversized attachment plate.

The two Rockomax probe engines: Lower their Isp and thrust, so that they're not the go-to Eve Launch Engine. That really should be the Aerospike.

The 24-77 is already balanced with with the other small engines because of its low Isp. The 48-7S might need some nerfing to make the LV-909 useful again.

O-10 Monopropellant Engine: Increase size, cost, mass, and thrust. Make it a valid dual-engine solution for the Orbital Maneuvering System on the shuttle. Either that or keep this the same and make the Mark 55 Radial Engine a monoprop motor.

The O-10 engine is already powerful enough. You don't really need a TWR higher than 0.1 for orbital maneuvers. I just recently flew 30 missions with 100-tonne fuel tankers that used four O-10s as their orbital engines. The Space Shuttle used two 26.7 kN engines for the same task, so its TWR was even lower.

[Bill Phil]

Look at it. It looks like an F-1. It has high thrust like an F-1. It has low atmosphere efficiency like an F-1.

It's oversized, sure. But it's clearly a J-2 analog.

280 SL ISP isn't too far off, actually. The LV-909 has 300 SL ISP. The Dv loss isn't much. In fact, the SL ISP of the J-2 is 200 seconds. The ISP if an F-1 at SL is around 260 seconds.

Although, the Kerbodyne tanks should have slightly HIGHER mass ratios than the rockomax tanks. Just because it's bigger, doesn't mean it has a smaller mass ratio, actually, it's the opposite in many cases. They're already insanely expensive...

Edited November 28, 2014 by Bill Phil

[Whirligig Girl]

Okay, so after some closer looking, I want a huge lowering of thrust on the KR-2L, and a new F-1 engine analog.

[Frozen_Heart]

I hate the KR-2L. It has tons of thrust and an amazing ISP. Completely wrecks the balance.

I'm not a fan of the LFB and the KS-25 either. We should have been given adaptors so we could use them for other things as well rather than premade parts.

[Kegereneku]

About the Aerospike.

I'm not sure increasing its thrust (and cost) would solve the the core of its problem, because it lie in the dynamic of every engines.

See, the current relation between engine performance and altitude used by KSP make Isp vary with atmospheric pressure, this is playable, but wrong.

Thrust is what actually vary with atmospheric pressure.

Edit : I was remembered that Isp's equation include Thrust, meaning it does change with pressure(since thrust vary), what's wrong is that Fuel Flow (in Isp's equation) should remain constant, unlike now.

The selling point of the Aerospike is that unlike other engines it can maintain the same amount of thrust (while also being more fuel efficient) over a wider range of atmospheric pressure. Those qualities are what would make it the engine of choice for any single stage or reusable SSTO.

However as it is now, all other engine have the same quality and staging is more fuel-efficient while being cheaper.

So I think making the Aerospike more powerful would only reestablish the reason it was considered "OP" when first introduced.

Not that I see any easy way to remedy to this problem without changing the aerodynamic.

Edited November 28, 2014 by Kegereneku
various correction

[Red Iron Crown]

See, the current relation between engine performance and altitude used by KSP make Isp vary with atmospheric pressure, this is playable, but wrong.

Thrust is what actually vary with atmospheric pressure.

Not quite. Isp does vary with atmospheric pressure in real life, just look at the stats for any real life engine. The unrealistic part is how that change in Isp is handled, in KSP fuel flow rate varies while thrust remains constant, in real life fuel flow rate remains constant while thrust varies.

[BudgetHedgehog]

Yeah, I don't see valid reasons behind the majority of these suggestions. The Aerospike is perfectly fine as it (it's dangerously close to OP as it is) and the RT-10... lolwat? You know it's one of the first parts in the game, right? And players with FAR and/or DRE are going to lower the thrust anyway..

And you know the O-10 is physicsless anyway, right? Increasing its mass won't do anything as it already has an infinite TWR. Stick as many as you like on your shuttle, it ain't going to be any heavier. That's the imbalance.

Cost/tech tree changes aren't going to make any difference in sandbox and a rebalance should balance engines against each other, not the players progress. ATM, the NERVA is fine - yeah, it's the go-to long-range vacuum engine, but it's heavy and unwieldy as well.

However, I do like the idea of separating out the 4 nozzle NASA engine (seriously, why do they all have such forgettable names?) My only worry would be part count though. Either that or a new angled engine with high gimbal with around the 400kn thrust range (who am I kidding, just make KM SSE stock already..).

[J.Random]

Can I downvote this (and every other "need rebalance") suggestion? Engine balancing is pointless until atmospheric model is improved (which was kinda promised) and fuel flow curve replaced by thrust curve (I don't think Squad promised this one, but I can dream, right?).

[NBZ]

and a new F-1 engine analog.

You may like NecroBone's SpaceY pack:

R1 engine 2 MN under a 2.5m stack

R5 cluster 10MN under a 5m stack

[Kegereneku]

Not quite. Isp does vary with atmospheric pressure in real life, just look at the stats for any real life engine. The unrealistic part is how that change in Isp is handled, in KSP fuel flow rate varies while thrust remains constant, in real life fuel flow rate remains constant while thrust varies.

Oh yeah, entirely right.

I've been using the word Isp recently as a goaround and forgot it represented both Flow Rate and Force, aka Thrust, so a part of it do vary with atmospheric pressure. It's making me very feel tired right now.

In any case it is definitely linked with the aerodynamic model, it would be a very fundamental change.

All tutorials would have to explain how thrust do vary with altitude, all design would be made obsolete, game balance would entirely change as pointed out by J.Random.

The more I think about it, the more I'm wondering if an Aerodynamic Model upgrade wouldn't be the biggest change since docking.

[John FX]

My request is very simple.

A 100kn engine with a low profile and not too heavy for landers.

It is a glaring gap in the range right now.

[Jouni]

Okay, so after some closer looking, I want a huge lowering of thrust on the KR-2L, and a new F-1 engine analog.

The KR-2L needs most of the thrust it has. The largest single part in the game weights 82 tonnes, so the game needs a relatively simple way of launching 100-tonne payloads. Add an upper stage that's powerful enough to push such payloads to orbit, and the total mass becomes around 200 tonnes. With the stock atmosphere, where drag is significant even in the upper atmosphere, upper stages need a relatively high TWR. For a 200-tonne upper stage/payload combination, the engine should produce at least 2000 kN of thrust. With a more reasonable atmosphere, the 3.75 m upper stage engine could work with just 1500 kN of thrust.

[Whirligig Girl]

You may like NecroBone's SpaceY pack:

R1 engine 2 MN under a 2.5m stack

R5 cluster 10MN under a 5m stack

I know of this mod; but I'm talking about stock parts.

[Whirligig Girl]

Yeah, I don't see valid reasons behind the majority of these suggestions. The Aerospike is perfectly fine as it (it's dangerously close to OP as it is) and the RT-10... lolwat? You know it's one of the first parts in the game, right? And players with FAR and/or DRE are going to lower the thrust anyway..

And you know the O-10 is physicsless anyway, right? Increasing its mass won't do anything as it already has an infinite TWR. Stick as many as you like on your shuttle, it ain't going to be any heavier. That's the imbalance.

Cost/tech tree changes aren't going to make any difference in sandbox and a rebalance should balance engines against each other, not the players progress. ATM, the NERVA is fine - yeah, it's the go-to long-range vacuum engine, but it's heavy and unwieldy as well.

However, I do like the idea of separating out the 4 nozzle NASA engine (seriously, why do they all have such forgettable names?) My only worry would be part count though. Either that or a new angled engine with high gimbal with around the 400kn thrust range (who am I kidding, just make KM SSE stock already..).

I'm pretty sure they fixed physicslessness of the O-10, and at any rate, increasing it's mass would also entail giving it physics.

[Red Iron Crown]

I'm pretty sure they fixed physicslessness of the O-10, and at any rate, increasing it's mass would also entail giving it physics.

It is still physicsless in 0.25, with the dubious distinction of being the most massive massless part (nominally 90kg).

[Whirligig Girl]

Just remember though,

[King Arthur]

I hate the KR-2L. It has tons of thrust and an amazing ISP. Completely wrecks the balance.

I'm not a fan of the LFB and the KS-25 either. We should have been given adaptors so we could use them for other things as well rather than premade parts.

I'm going to play Devil's Advocate.

The KR-2L with the state KSP is in right now needs the high thrust.

Currently the 1.25m (Jeb's Junkyard/C7 Aerospace), 2.5m (Rockomax/Kerbodyne), and 3.75m (Kerbodyne) engines follow a simple and easy power growth pattern of "small->medium (used to be large prior to ARM)->large" respectively, with the LV-T30 maxing out the 1.5m engines at 215kn, the LFB KR-1x2 topping out the 2.5m engines at 2000kn (outpowering the Mainsail at 1500kn), and the S3 KS-25x4 capping out the 3.75m engines (and consequently the entire stock engine lineup) at 3600kn.

At 2500kn, the KR-2L is the smallest of the 3.75m engines and is only running a 500kn difference from the 2.5m engines. Literally, without nerfing all of the other smaller engines across the board, the KR-2L cannot be nerfed while still preserving the "small->medium->large" pattern of engine power growth.

At the same time, the KR-2L cannot have its vacuum ISP reduced as it's an oversized analogue of the real-life J-2 and J-2X which were also upper stage engines tuned for performance in vacuum.

The crux of the issue with the KR-2L is that it serves as the "Poodle" of the Kerbodyne lineup, tuned for flying in space, but cannot reduce its thrust any lower than it currently is without being overshadowed by the 2.5m lineup.

For what it's worth though, the KR-2L is an absolutely terrible engine to consider using for a 1st stage as its atmosphere ISP is 280, clearly inferior to most of the "launcher" tuned engines.

[Laie]

Also, the KR-2L having an "amazing" ISP is mostly psychological. It's sitting squatat in the middle between the skipper and the poodle, yet somehow we insist to see it as "almost as good as the poodle" rather than as "an improvement over the skipper". Also bear in mind that it's atmospheric ISP is considerably worse than the Skipper's.

The other problem is TWR. We've come to expect that when the ISP goes 370->390 (a whopping 5% improvement), the TWR has to drop by like 30-40%. This already poses the problem that the good-ISP engines are sitting in a tight niche: you need to run them for like 2500m/s of delta-v until they make up for their extra weight. For that kind of delta-v, the LVN will be better still. Also see the other threads about perking the Poodle and nerfing the LVN that are currently active. The KR-2L is breaking that pattern of good ISP coming with bad TWR, and frankly, I think that's a good idea.