I don't understand the fuss behind ARM

[SofusRud]

Before that we just built a simple rocket to launch a simple ship to Laythe. That was probably easier, as we didn't have to worry so much about fuel usage.

Perhaps you missed my point.

The point I was making with my Single Stage to Laythe was to demonstrate that the new ARM engines were unbalanced to such a degree as to make it possible to hastily throw together a craft (using only one engine type) that can reach that far in a singe stage.

[Jouni]

I just don't see the point. If you can navigate to Laythe easily, you can probably build a simple rocket that can fly there easily. That hasn't changed. It was already possible to build single-stage rockets to Duna (using Aerospikes or 48-7S engines), so upgrading that to Laythe wasn't such a big deal.

[Dodgey]

No, I would not object, If the engine was "warp drive" or similar and had an astronomical energy cost and research tree and needed unobtainable. I trust them so far not to go completely insane though.

No, not a warp drive just a very good chemical engine. And let's say it was put at the top of the tech tree to "balance" it in career mode. Once you unlocked it what would be the point of using any other engine, you could say that economics would balance it out, but the only information we have received about that is that all three currencies (science, rep and money) would be interchangeable. For the sake of argument let's say that it was balanced by the economics, how do you work with sandbox. You could say it's not ment to be balanced it's sandbox, but my question would be, if you could properly balance both sandbox and career why wouldn't you? That's what I don't like about the new engines and the argument of "it will be balanced in career", if you could balance them in both career and sandbox (which you can by the way, look at the mod Stupid_Chris brought out) why wouldn't you?

Jouni, the point he is making is that a hastily thrown together rocket is able to make it to laythe using only one engine, yea you could make a rocket SSTD but I'm assuming that it wouldn't be a five minute build job. In anycase, throwing together 14 odd fuel tanks and 7 engines should not make an SSTO in anycase, I can't see any situation where this is logical.

Edited April 9, 2014 by Dodgey

[Rakaydos]

For that matter how is Science (a limited but permanant resource) supposed to be exchanged for budget? (which most people seem to be thinking is a renuable, expendable resource)

Can you give away your budget to unlock the tech tree, launch a capsue, recover it, then repeat?

[Dodgey]

For that matter how is Science (a limited but permanant resource) supposed to be exchanged for budget? (which most people seem to be thinking is a renuable, expendable resource)

Can you give away your budget to unlock the tech tree, launch a capsue, recover it, then repeat?

I remember the devs saying that at some point, I can not remember where they said it, but I do remember them saying it. If anyone could confirm/deny this that would be awesome.

[Jouni]

Jouni, the point he is making is that a hastily thrown together rocket is able to make it to laythe using only one engine, yea you could make a rocket SSTD but I'm assuming that it wouldn't be a five minute build job. In anycase, throwing together 14 odd fuel tanks and 7 engines should not make an SSTO in anycase, I can't see any situation where this is logical.

Four Aerospikes and 1.5 jumbo tanks worth of fuel provide 5800 m/s of delta-v for 1.5 tonnes of payload. That should be enough to reach Duna, if only barely.

SSTO rockets are supposed to be easy, because Kerbin is so small.

[SofusRud]

I just don't see the point. If you can navigate to Laythe easily, you can probably build a simple rocket that can fly there easily. That hasn't changed. It was already possible to build single-stage rockets to Duna (using Aerospikes or 48-7S engines), so upgrading that to Laythe wasn't such a big deal.

The point is that when a new engine allows slapdash constructions like mine to do stuff like that it demonstrates an imbalance in that engine. That's the whole point of having a wide array of rocket engines for different purposes. My single stage to Laythe clearly demonstrates that

Only thing the new parts make easier, is getting things to orbit, so less docking requred

is simply not true. The new engines are so overpowered as to make other rocket engines unnecessary for that kind of mission. Not only does the practical obsolescence of a large number of parts bother me, but its also the fact that these new engines make it too easy. I got no sense of achievement from that Laythe mission because the engines are so overpowered that i might as well have had infinite fuel on. Can we at the very least agree that part of the fun of going to other planets in KSP is the sense of achievement you get from doing something difficult.

Also, as to the the folks who say that "if we think engines aren't balanced then we should just stop using them": What kind of argument is that? Part of the fun in achieving something is mastering the tools in your disposal in order to overcome a difficult task. If one of the tools at your disposal is an instant problem-solving device then that cheapens the whole process. And if we were to accept that argument the devs might as well have been deciding engine stats by throwing a dart at a wall covered random numbers, but they haven't. Until now the engines were more or less balanced (see Stupid_Chris's graphs) and the devs have made efforts to keep parts balanced when they weren't (see Aerospike and LV-N), so why shouldn't they do so again in this case.

[SofusRud]

Four Aerospikes and 1.5 jumbo tanks worth of fuel provide 5800 m/s of delta-v for 1.5 tonnes of payload. That should be enough to reach Duna, if only barely.

SSTO rockets are supposed to be easy, because Kerbin is so small.

Actually because kerbin is smaller, for reasons of processing power and gameplay, engines in KSP have a significantly higher mass compared to real-world rockets. Again, this is for balance purposes, in order to lower TWR and make rocket SSTO less easy and less viable. SSTO rockets are not "supposed" to be easy

Edited April 9, 2014 by SofusRud

[Jouni]

Actually because kerbin is smaller, for reasons of processing power and gameplay, engines in KSP have a significantly higher mass compared to real-world rockets. Again, this is for balance purposes, in order to lower TWR and make rocket SSTO less easy and less viable. SSTO rockets are not "supposed" to be easy

Are you suggesting that no combination of fuel tanks and engines of a single type should provide 4500 m/s of delta-v with the smallest probe core? If that's so, then we have a lot of engines to nerf, as otherwise SSTO rockets would be easy.

[SofusRud]

Are you suggesting that no combination of fuel tanks and engines of a single type should provide 4500 m/s of delta-v with the smallest probe core? If that's so, then we have a lot of engines to nerf, as otherwise SSTO rockets would be easy.

that is not what I am saying. I am saying that there is a point at which "SSTO rockets are possible" becomes "SSTO are a viable way to go places and do stuff (again, see my Laythe rocket)", and with the new ARM engines that point has clearly passed

[Jouni]

that is not what I am saying. I am saying that there is a point at which "SSTO rockets are possible" becomes "SSTO are a viable way to go places and do stuff (again, see my Laythe rocket)", and with the new ARM engines that point has clearly passed

Do you count Duna as a place where simple single-stage rockets are not supposed to go? You can apparently do that with Mainsails, Skippers, LV-30s, and LV-45s too.

[maccollo]

Do you count Duna as a place where simple single-stage rockets are not supposed to go? You can apparently do that with Mainsails, Skippers, LV-30s, and LV-45s too.

I don't think "how far can you throw the lightest probe?" is a good illustration of how unbalanced they are, but I think this is.

The first rocket is a two and a half stage design (although the boosters fire a bit long), weighs 197 tons, the payload weighs 25.15 tons.

The second rocket weighs 196 tons and launches the same payload, but it's an SSTO!

Edited April 9, 2014 by maccollo

[Aedile]

Do i have to start waving pictures of my Single Stage to Laythe craft around again? How easy was that to do before ARM?

Jet engines work on Laythe, so landing and coming back with SStLnB, is not ARM achievement. Jets and nuclear engine will get you there and back. You don't even need to bother with wings...

And I believe SSTO requires "getting things to orbit". You will still get much more delta V from aerospike (ASL) or nuclear engine(VAC) than any of the new parts.

So you can do more things with a bigger rocket... You can do more things with the 2.5 parts 1.25 ones. You can do many things with wings and jets, nuclear engines and aerospikes too. Guess you hated the rover parts when they came out. Using ship+lander opens a lot of possibilities as well.

You can do more things with the old parts now due to the stiffer joints.

Feel free to limit yourself in any way you see fit. Whatever floats your boat.

BAIU. The only things it would seem worth asking are:

2. Is asparagus the only way to make a monstrosity of a rocket?

3. Have you really never seen an asparagus-staged rocket that looks good?

I guess, I prefer rockets to look somehow realistic. Don't get me wrong, building monstrosities is fun, and you can build even bigger ones now, so sure. I just like having the option, not to have to build one. For me most of the new parts are not so useful, as I usually prefer minimalistic designs, and usually don't do direct ascent. If I can do it with less weight and fuel, I do.

I have seen, and I do build asparagus staged rockets, I'm pretty sure you know which ones I'm talking about. Edit - it's not just looks btw, it's control and drag as well, (especially if using more realistic drag model)

Edited April 9, 2014 by Aedile

[Jouni]

I don't think "how far can you throw the lightest probe?" is a good illustration of how unbalanced they are, but this is.

The first rocket is a two and a half stage design (although the boosters fire a bit long), weighs 197 tons, the payload weighs 25.15 tons.

The second rocket weighs 196 tons and launches the same payload, but it's an SSTO!

16 Aerospikes and 5 orange tanks worth of fuel would also work, but the total mass would be around 230 tonnes. The new engines improve SSTO efficiency by 17% over Aerospikes.

[Dodgey]

The point is that you can just throw together a bunch of fuel tanks and engines and go to Laythe in a single stage, jet engines are overpowered however you look at it, hell you can get to orbit without using any oxidiser (there was a challenge to get to orbit with the least about of oxidiser, the majority of winners had 0 used). As we said, the point is that you can throw a bunch of tanks and engines together and get to Laythe in a single stage, where is the engineering challenge.

EDIT:

20%? And don't you think that is a pretty substantial increase without using jet engines?

Edited April 9, 2014 by Dodgey

[SofusRud]

Jet engines work on Laythe, so landing and coming back with SStLnB, is not ARM achievement. Jets and nuclear engine will get you there and back. You don't even need to bother with wings...

And I believe SSTO requires "getting things to orbit". You will still get much more delta V from aerospike (ASL) or nuclear engine(VAC) than any of the new parts.

So you can do more things with a bigger rocket... You can do more things with the 2.5 parts 1.25 ones. You can do many things with wings and jets, nuclear engines and aerospikes too. Guess you hated the rover parts when they came out. Using ship+lander opens a lot of possibilities as well.

Could you do Single stage to Laythe using only one type of engine? Because that is my point, way to miss it. The my argument isn't that "engines let you do stuff" but that these ARM engines are practically ALL you need to do stuff. And sure, Aerospikes and nuke engines have higher ISP, but that is balanced with a lower TWR that precludes doing the things with them that you can now do with the ARM engines. Single stage to Laythe used to be a difficult business of jets, wings, nukes and copious fuel management, and that's what made managing to do it cool. For that matter, rovers are cool, and I find your assumption that I wouldn't like them to be odd and slightly insulting.

As for just limiting myself, see my previous post on this thread wherein I explain why I reject that argument

Edited April 9, 2014 by SofusRud

[Aedile]

I don't think "how far can you throw the lightest probe?" is a good illustration of how unbalanced they are, but I think this is.

The first rocket is a two and a half stage design (although the boosters fire a bit long), weighs 197 tons, the payload weighs 25.15 tons.

The second rocket weighs 196 tons and launches the same payload, but it's an SSTO!

http://youtu.be/Xey0WyIfTBw

Mainsail has always been crappy engine, so are most 2.5m ones.

I do not understand why people are so much bothered by this? Getting the twr right does miracles.

Now, do try a case with lifting only a Mk1-2 pod.

Pod,x200-16,orange tank, skipper - SSTO 54tons- (barely to orbit)

Same thing, but mainsail 55tons - nowhere near orbit.

Same thing 21(yup) rockomax 48, 50 tons - comfortably to orbit and 500ms left

Same thing 4 LV-30, reaction wheel, 55 tons - comfortably to orbit and de-orbit

Mk1-2 pod. Pod,x200-16, the new 2.5 engine, 55 tons - didn't make it to orbit.

FLTt-800,Pod, s3-7200 Tank, KR2L engine - 56 ton, no dice, short some 200ms.

Pod, s3-7200 Tank, Ks25x4 engine - 54 ton - exercise in futility.

So you see your results may vary depending on payload

Why would you need a 197 ton rocket to lift a 25 ton payload, is a bit unclear for me...

[Rakaydos]

Mainsail has always been crappy engine, so are most 2.5m ones.

I do not understand why people are so much bothered by this? Getting the twr right does miracles.

That's the thing, the mainsail IS a crappy engine, but one you use anyway because it can carry a stack 4 orange tanks high. The crappyness means you only use it whenn you have to.. not just put fuel tanks on it and fly anywhere.

Barring the Stock Rebalance project , the x4 cluster can only carry a stack of 3 s3 tanks. When it comes to making a rocket look like a rocket, the most powerful engine in the game is actually undergunned compared to it's "crappy" smaller cousin. But it's ISP is so high that an ugly, squat rocket can get anywhere in the kebin system without even dropping asparagus stages to thin it down.

The stock rebalance project is a mod that changes the stats of the over and underperforming engines. In it, the x4 cluster is a heavy fuel hog, even worse than a mainsail... but it can lift a stack of 5 size 3 tanks agains kerbin's gravity. You use it in a first stage to make a rocket look like a rocket- not to make a squat monster that goes where it pleases.

[Jouni]

If we want to balance the engines for sandbox, we can't really have that many different engines. Apart from some special cases (e.g. jet engines, ion engines, Eve landings, possibly Tylo landings), we only need about four different engines:

1. Booster engine with high TWR and low Isp.
   
2. Core engine with more thrust and better Isp than the booster engine. For balance, it should have lower TWR.
   
3. Vacuum engine for orbital maneuvers and most landings. High Isp but relatively low thrust and TWR.
   
4. Transfer engine for interplanetary trips. Even higher Isp and lower TWR.
   

Of course the same engine may come in different sizes, but it's still just one engine. If the engines in the same category have different TWR and Isp, one of them will most likely be better than the others.

The distinction between booster engines and core engines is based on the assumption that all reasonable lifters use asparagus staging. (There is no point in vertical staging, if you are mostly interested in efficiency.) The more boosters the lifter uses, the more powerful the core must be compared to a single booster. Because the core engine is used all the way to the orbit, it makes sense for it to have relatively high Isp.

The SLS engine cluster actually has too much thrust. The real SLS first stage (essentially the engine cluster and a stack of three big fuel tanks) will not be able to lift itself, so it really needs the boosters to get off from launchpad. There are also other rocket designs like that, where the first stage is more like a second stage with a lot of extra fuel, while the boosters do the heavy lifting. I really like most things in the Stock Rebalance Project, but changing the role of the SLS engine cluster is not one of them.

[Rakaydos]

1. Booster engine with high TWR and low Isp.
   
2. Core engine with more thrust and better Isp than the booster engine. For balance, it should have lower TWR.
   
3. Vacuum engine for orbital maneuvers and most landings. High Isp but relatively low thrust and TWR.
   
4. Transfer engine for interplanetary trips. Even higher Isp and lower TWR.
   

Of course the same engine may come in different sizes, but it's still just one engine. If the engines in the same category have different TWR and Isp, one of them will most likely be better than the others.

So...

RM48= Probe Booster

LV30= 1m Booster

Mainsail/LFB= 2m booster

stock rework SLS cluster= 3m booster

RM 55= Radial Booster(??)

Ant engine= Probe core

LV45= 1m core

Skipper= 2m core

Large bell= 3m core

Ion: Probe transfer engine

NERVA: 1m transfer engine

Not sure how all the radial engines fit in, as they tend to be anemic but easilly spammed.

The SLS engine cluster actually has too much thrust. The real SLS first stage (essentially the engine cluster and a stack of three big fuel tanks) will not be able to lift itself, so it really needs the boosters to get off from launchpad. There are also other rocket designs like that, where the first stage is more like a second stage with a lot of extra fuel, while the boosters do the heavy lifting. I really like most things in the Stock Rebalance Project, but changing the role of the SLS engine cluster is not one of them.

Really, they should have give us 1m shuttle engines and a 3m cluster adaptor pack. That way those of us who wanted to buils an SLS could use the x4 adapter, those that want to build a saturn 5 could use a 5x adaptor, and those of us who want to put 27 ion engines under a size 3 tank can do that too.

Edited April 10, 2014 by Rakaydos

[Coccalime]

I think the idea of talking about balance before currency is introduced is just silly. In real life you could send tiny satellites into space with rockets like the Saturn V and it would seem over powered, but it wouldn't be practical cost wise. These new parts are based off of real world equivalents so i don't really think they are over powered, and once money is implemented they will cost much more and as such they will be much less practical. The rockets only seem over powered because they don't have a downside yet, but they will in the future because they will be much more expensive.

[Rakaydos]

I think the idea of talking about balance before currency is introduced is just silly.

If you're interested, come talk about how budget should work over here. There's been a few developer comments that touch on the subject, so we can at least start speculation.

[antiquark]

Yeah, seems overpowered. Here's an SSTO that will get an orange tank (!) into orbit.

At one time, I used an orange tank as a criteria to determine if my multi-stage booster design was up to snuff. Now it's a piece of cake!

[hansman1982]

Maybe I am doing something wrong but my ARM engines are overheating like a SOB. Typically I have to cut their thrust down to 45% in order to stop it.

I really don't see the fuss. Especially if you download KW.

[magnemoe]

that is not what I am saying. I am saying that there is a point at which "SSTO rockets are possible" becomes "SSTO are a viable way to go places and do stuff (again, see my Laythe rocket)", and with the new ARM engines that point has clearly passed

Previously SSTO was possible but had an terrible payload faction they also did not scale up well because of part count. Note that for me an SSTO has to land again to be relevant else you can just as well use staging.

Well I have three SSTO in my stall now, one is an 7 kerbal transport, second uses one 24x4 and a 3.75 frame it will put 20 ton in orbit, used it for an small Mun expedition. last is an 120 ton cargo to LKO it uses 7 of the 24x4, now if I stuff 4 of the new SRB on the 20 ton version it can put 40 ton in orbit, with 12 SRB on the large and its 200 ton.

I rarely have an need to launch more. SRB lands safe back on spaceport with parachute.