ARM SLS Parts and the Start of The Career mode age?

[Jouni]

That could lift some 45, maybe 50tons to lko. Once you get to 100 ton payload, using the old stock engines you are forced to build wide rather than tall.

A two-stage rocket with a Mainsail at the bottom lifts around 15 tonnes to LKO, so four Mainsails would lift around 60 tonnes, if we can find reasonable engines for the second stage.

They exist in my gamedata folder, and combined with procedural tanks large rockets are a lot less finicky to build and look a lot nicer than using old stock parts.

Serial staged rockets up to at least 150 tons to LKO are no problem (thanks in no small part to Squad fixing the attach joints).

Everything exists as a mod, at least potentially. I thought we were talking about stock parts.

The first stage of those is in the range of 5 to 7.5m diameter. That's a lot of surface but not enough to get enough thrust if you use Mainsails, but it is enough if using engines with specs and dimensions like the SLS engines. http://forum.kerbalspaceprogram.com/threads/29533-What-did-you-do-in-KSP-today?p=1128657&viewfull=1#post1128657

It has always been possible to build a 7.5 m diameter rocket with seven Mainsails to lift over 100 tonnes to LKO.

In the "two boosters and two vertical stages" model, using Mainsails leads to ridiculously tall rockets.

Edited May 5, 2014 by Jouni

[rkman]

four Mainsails would lift around 60 tonnes.

I'm usually going for higher launch twr, 6000 thrust for 60 ton payload is a bit low for my taste. Doable but i'd avoid it if possible, and a lot is possible with clustering 'new standard' engines.

Everything exists as a mod, at least potentially. I thought we were talking about stock parts.

Actually I am talking 'new standard'.

It has always been possible to build a 7.5 m diameter rocket with seven Mainsails to lift over 100 tonnes to LKO.

I replicated that rocket to try it out. Obviously it works, but it has a low launch twr, about 1.2 with a 115 ton payload. It may lift more than 100 tons to lko but not a great deal more. It wastes about 130m/s to gravity loss compared to a rocket with 1.7 launch twr.

Also, following the 'new standard', a rocket with a 7.5m first stage would lift at least 150tons to lko. 100 tons (and a bit, i you want) requires 5m.

7.5m, 150tons to lko:

Edited May 5, 2014 by rkman

[Jouni]

Actually I am talking 'new standard'.

That "new standard" only exists in mods. Except for the LFB, the new ARM engines have less thrust per area than the Mainsail.

I replicated that rocket to try it out. Obviously it works, but it has a low launch twr, about 1.2 with a 115 ton payload. It may lift more than 100 tons to lko but not a great deal more. It wastes about 130m/s to gravity loss compared to a rocket with 1.7 launch twr.

High TWR at launch is a sign of using too powerful engines. Real rockets often have TWR 1.2 or less at launch, because engines are expensive, but fuel is cheap.

Edited May 5, 2014 by Jouni

[rkman]

High TWR at launch is a sign of using too powerful engines.

"To high" obviously is. That rocket with twr 1.2 needed 130m/s more delta-v to get into orbit than one with 1.7twr (i tried other ascent profiles, it only got worse). So i'd say 1.7 is not "high" as in "using too powerful engines", rather it is "high" as in "high enough to be fuel efficient", and 1.2 is to low to be fuel efficient (talking about ksp, not real life).

With stock engines getting 100tons to lko requires a 7.5m first stage, and it will be a sub-optimal rocket.

With engines that follow the new SLS specs (even when tweaked to be more in line with Stock Rebalance) it is possible to deliver the same payload with a 5m 1st stage, and fuel efficiency will be near optimal.

All in all i think the point still stands that the SLS engines are not only more fuel efficient but also have higher thrust-to-surface ratio than older stock engines, and that the difference is significant. I suppose it hinges on whether one thinks the KS-25x4 is one 3.75m engine or 4 ~1.5m engines.

[Jouni]

"To high" obviously is. That rocket with twr 1.2 needed 130m/s more delta-v to get into orbit than one with 1.7twr (i tried other ascent profiles, it only got worse). So i'd say 1.7 is not "high" as in "using too powerful engines", rather it is "high" as in "high enough to be fuel efficient", and 1.2 is to low to be fuel efficient (talking about ksp, not real life).

If you optimize fuel efficiency or delta-v usage, your rockets will actually be worse from the perspective of this discussion. If the goal is to build tall rockets, the obvious solution is to add more fuel as long as it increases payload capacity. If the payload is fixed, lower initial TWR means that you can use less engines, decreasing rocket diameter. On the other hand, if rocket diameter is fixed, you can add more fuel, increasing the payload capacity.

I made some quick calculations based on the assumption that the KS-25 engine is a 1.5 m engine (and big fuel tanks are as inefficient as the stock 3.75 m tanks). It's possible to fit 19 engines under a 7.5 m fuel tank in a hexagonal pattern, giving us 15200 kN of thrust to work with. That should be enough to lift around 220 tonnes to LKO with a two-stage rocket, or about twice as much as with Mainsails.

Edited May 5, 2014 by Jouni

[LethalDose]

That "new standard" only exists in mods. Except for the LFB, the new ARM engines have less thrust per area than the Mainsail.

To be fair, the LFB is kinda nuts... 50% more thrust than the mainsail and substantially better Isp in the atmosphere and in vacuum.

Edited May 5, 2014 by LethalDose

[John FX]

John FX, the 48-7S is commonly considered overpowered, too. Showing that an overpowered part exists doesn't nullify the concept of sandbox balance, nor is it a good justification to add parts that are even more unbalanced, IMO. If anything, the 48-7S is an illustration of how overpowered parts crowd out the others in efficient designs.

The ions and NERVAs could be considered overpowered, but the balance with those comes from long burn times and lack of larger versions appropriate for big craft. Effectively, player patience and part count considerations help balance those.

As an aside, your link is broken for me, were you meaning to link to tavert's charts?

Oh, I thought I had replied earlier. You are right in what you say but I provided the figures as an example that sandbox balance has never been the priority. With career looming I can see it taking a further back seat than it already does.

And the 48-7S does crowd out other designs if you don`t have other considerations, like part count or how much they cost...

If you had to pay and the pay came from your profit then the new engines might not be the best choices.

Apologies for the link I forgot it needed wolphram alpha cdf player (IIRC)

The link is quite handy, you input your payload, the TWR you require and the Dv you want and it tells you how many of each engine and what fuel tanks you need.

I sort of stopped using it though because the rockomax 48-7s always is the best engine for TWR>1 and the NERVA for TWR<1 if you want any reasonable amount of Dv or payload at all. The craft that this is not the case for are craft I can`t think of a reason to fly.

The only difference I see now is that you don`t have to use a spreadsheet or online calculator to find out which the best engine is.

For an example, the game Total Annihilation had many robots. There were tech 1, 2, 3, and experimental.

If you built an experimental robot then they wiped out everything except experimentals.

They were totally overpowered but were made balanced by having very very very long build times and huge resource requirements.

The game would have been ruined if they were balanced with the other robots purely on combat ability, `balanced for sandbox` so to speak.

They were the reason you developed tech, built your resource production, and put the time and resources into building them.

If they were balanced then you could just build loads of tech 1 robots and swarm them and they would have no niche. There would be no point to most of the game.

Sort of like the poodle now. I never use the poodle, it`s heavy, underpowered, and ugly.

I`d use it in career or a contract if it was cheap enough though.

[Tery215]

SLS isn't balanced for sandbox, but it is for career...

I am very doubtful on this issue.

[Red Iron Crown]

The way parts are balanced may be more career-oriented as time goes on, with some parts obsoleting others. I'd be disappointed if that were so, as I play mostly sandbox and that would mean I would be limited to a smaller subset of available parts if I want to be efficient.

Like most things KSP, we'll have to wait and see.

[Wahgineer]

Career mode (will) balance the parts. Like the OP said, these parts are meant for rockets that will travel to destinations not yet born and across distances not yet conceived. The SLS parts are meant for the part of CAREER where what is on the rocket matters more than the rocket itself. These parts are signalling the end of the sandbox age and the beginning of the career age. Many thought this day would never come, but I'm sorry to say it has: the age of the orange pancake/asparagus HLVs is coming to an end.

[MKI]

As a reference, i have started making huge SLS launches that literally launch whole stations. 7 Orange Fuel tanks for a low orbit Fuel Depot for my SSTO's

This is easily done in the stock game IN A FEW MISSIONS. With the SLS parts i did it in 1. The only way i could of managed such a single mission in the stock game WITHOUT the SLS parts would be a huge multi mainsail, super heavy, super laggy asparagus monster. Is this practical no, but now with the SLS parts it is.

Even large size multi ship missions can be launched via the SLS parts in a single mission. I was able to get a Duna Capable craft into orbit in a single launch, with lab, 3 manned pod and transfer vehicle. All with taking considerable amounts of non-essentials.

Again this isn't even possible without some ridiculous launch unit. Even with the SLS parts, the part count is mostly the payload itself.

@Tery215 - The game is progressing toward Career focus. All updates since they added Career mode have put Career mode front and center. Why can't the same be said for all the parts Squad implements? A sandbox game is nice and all, but when the game is called Kerbal Space Program, you would expect some focus on the Program part wouldn't you? Getting to space in career, and in real life, depends mostly on funding, so if you have the funding you should have better gear. Might seem bogus for sandbox, but it makes perfect sense for a more dynamic career mode.