Maximum Lifter Capability?

[Wijbrandus]

I've been doing fairly well getting payloads into orbit, and then on to the moons (Mun and Minmus). However, last night I kind of hit a brick wall.

I'm trying to get a payload into orbit, AND have enough fuel to get it to the Mun. The payload weighs 35 tons. I do not believe this is something I can assemble in orbit as it has to be solid enough to land on the Mun and launch again repetitively.

Is there a practical limit to how much payload we can move in one launch? I have tried all sorts of variations, but I haven't hit upon anything that can get this into orbit, let alone have enough fuel to make a rendezvous with the Mun. If anyone has successfully moved that large of a payload, can you share your secrets?

The mods I am using so far are MechJeb, Kethane, and ISA_Map. This payload is a Kethane refinery.

[Nibb31]

Instead of trying to add capacity to your existing rocket, try building an extra stage underneath it that would lift the entire rocket. In theory, it will probably be 3 or 4 times bigger than the entire rocket.

[Daze]

I don't think it exist a particulary maximum payload, imo it all depend on how much asparagus your pc can tolerate

[Temstar]

With stock and using a single 2.5m stack as the load bearing element the maximum payload is about 200 tons. Above 200 tons some part of the stack will simply be crushed by the weight of the payload pressing down on it while the rocket at the bottom pushes it up.

But if you're willing to build payload horizontally consists of multiple stacks and have basically each of those 2.5 stack pushed up by its own rocket then there's no maximums size to payload other than part count.

[tavert]

Is there a practical limit to how much payload we can move in one launch? I have tried all sorts of variations, but I haven't hit upon anything that can get this into orbit, let alone have enough fuel to make a rendezvous with the Mun. If anyone has successfully moved that large of a payload, can you share your secrets?

The only real limit at present is the number of parts your computer can handle before the game becomes unplayably slow.

Look up some Youtube tutorials on "asparagus staging" to improve your rocket efficiency. There are some threads over in the Spacecraft Exchange that show example heavy lifter designs. Some better than others of course, but worth browsing to find and learn from the good ones.

[magnemoe]

An 6+1 aspargus with large gray tank+ orange tank and mainsails should not have much problem lifting this to orbit. You might want to use an nuclear upper stage who you can use from circulating to Mun deborbit burn, it has the benefit of also being easy to use on the Gilly launch.

[Akalaël]

Yes, with an asparagus style, you can easily lift very heavy playloads (talking here of hundreds of tons).

By "easily", I mean, once all the minor problems that occurs in KSP will be solved

just for the exemple see

http://kerbalspaceprogram.com/stock-enormus-refiuling-and-deep-space-ship/

a 155 tons lifter.

[numerobis]

35 tonnes you can even lift with a spaceplane. Frequent poster pa1983 (I think is the username, something like that) makes gorgeous SSTOs with more than that much payload capacity. I have also built such craft myself, though mine are lacking in the aesthetics department.

[Shuttle]

If anyone has successfully moved that large of a payload, can you share your secrets?

I don't recommend reading anyone else's tips because it will spoil all the pleasure of building a powerful rocket yourself

just for the exemple see

http://kerbalspaceprogram.com/stock-enormus-refiuling-and-deep-space-ship/

a 155 tons lifter.

Well, it is a powerful vehicle but the part count seems to be a little high to me (651 parts), and I also have only ~5-10 fps during lift off on GTX460 i5 2500

[HoY]

If you want to reliably get over 100tonnes into orbit you'll have to get used to 500+ part count for the launch. The heavier the payload, the more struts needed!

[Sir Nahme]

for 40 tons my lifter tends to be around 150-200 parts

[Noticeably FAT]

I don't recommend reading anyone else's tips because it will spoil all the pleasure of building a powerful rocket yourself

I don't know about all that. I can understand not downloading the craft files, but not looking for tips and tricks? After a while that just becomes frustrating if you just aren't able to solve the problem on your own. Even if you have solved a problem it's interesting to look and see how someone else solved it. There's really no such animal as a 'correct answer' in a game like KSP, and other people will think around some truly strange corners and their answers can improve yours.

To the OP: I'm not going to show you how to build it unless you ask, but my standard lifter will get 80T into orbit farily easily. It has a central core of a medium 2.5m tank + small 2.5m tank + mainsail (this could be better optimized but I've never bothered, it's really just the orbital maneuvering stage), under that is a jumbo tank + smallest 2.5m tank (for overheating) + mainsail (this fires with the asparagus boosters). Around that are four asparagus staged boosters consisting of two jumbo tanks + smallest 2.6m tank + mainsail. On each booster are two large SRBs. It's big, inefficient, loud, wobbly, and completely reliable for any payload I've wanted to lift. The largest was a jumbo tank with some small LF boosters using nuke engines. That was pushing the limits of the design, but it got the full orange tank into a 300km orbit just fine.

[Nao]

If you want to reliably get over 100tonnes into orbit you'll have to get used to 500+ part count for the launch. The heavier the payload, the more struts needed!

Not true . There are ways of getting more than 200t of payload into LKO without any struts, stock. And in less than 300parts too Gotta use them docking port's they do wonders!

As for the OP's question.

For me the best way of designing launcher is counting how much liftoff thrust you need and building around that.

For example 50t payload into LKO. Assuming 16% mass efficiency (13% is a nice safe value too), take off weight is 312,5t (50/0.16). To get required thrust i multiply the mass by TWR and gravity. Lliftoff TWR of around 1,8 is good value and gravity acceleration is 9,81. So finally it's 312,5*1,8*9,81=5520 with unit being [kN].

So i know i need around 5520 kN of thrust and that's equivalent to 3,7 mainsail engines. So i would use 4 asparagus staged mainsails and 240 tons of fuel for launcher (that's 13 gray rockomax 32 fuel tanks).

It's best to avoid big orange fuel tanks as they induce wobble if there are lot of them so using the gray tanks can save a lot of struts.

Lot's of struts help but if adding more doesn't solve problem of something blowing up, use F3 screen to make sure what part is failing first and try to place it differently or use struts to transfer the load somewhere else (if you already have a lot of struts on that part sometimes removing them can resolve the issue).

[MircoMars]

There's also the option to burn all the fuel in your refinery/transfer-stage during lift-off and refuel it in orbit.

I sometimes pump fuel from the cargo to the lift-off stage to decrease mass as early as possible and end up in orbit almost dry on fuel and rcs... 8)

[Shuttle]

Not true . There are ways of getting more than 200t of payload into LKO without any struts, stock. And in less than 300parts too

My best rocket consists of 200 parts and can lift 150 tons into orbit Challenge accepted

[HoY]

Funny, I find the opposite to be true regarding using grey half tanks instead of orange tanks..

And I did mention "reliably" getting into orbit,, launcher and payload together. So that's your 300 part launcher and another 200+ for the payload, unless your just sending up fuel tanks as dead weight!

My point is, if you want to lift heavy payloads in one shot you have to be willing to deal with any part count induced lag that comes with them.

[tuguley]

If you're talking about payload fraction (the weight of your payload in comparison to the lifter), anything above 10% to LKO is good.

Above 15% payload fraction (to LKO) is amazing and anything above that using only liquid fuel engines is quite the achievement.

You can use mods like engineer redux to find the mass of your stages.

Payload fraction (percent ?) = ( payload mass / total mass ) x 100%

[zavdan62]

get hayper edit ok!

[Nao]

Funny, I find the opposite to be true regarding using grey half tanks instead of orange tanks..

And I did mention "reliably" getting into orbit,, launcher and payload together. So that's your 300 part launcher and another 200+ for the payload, unless your just sending up fuel tanks as dead weight!

My point is, if you want to lift heavy payloads in one shot you have to be willing to deal with any part count induced lag that comes with them.

Ah.. yeah, thats true. I've never needed to launch something huge with a big part count and the only heavy thing was a fuel depot so i guess you are spot on

Part count lag is a pain, although at least we have lagsbane implemented now so even if launch takes 30minutes RL time we can get high part count stuff into orbit without worrying about everything exploding due to lag.

I'm really puzzled about your preference of orange tanks, they always wobble horribly for me and just replacing them with two gray ones solves the problem. Guess we design ships very differently

My best rocket consists of 200 parts and can lift 150 tons into orbit Challenge accepted

It looks like i'll finally have to finish the 25mainsail, no struts launcher i brag about hehe. It works in testing but i've never done any missions with it Good luck with your craft!

[Tristavius]

Agree with some of the above, the most I got into orbit was in the 170 ton region, and based on the TWR maths with the current components, sane limitations on system performance with parts and on not snapping like a twig, I don't think you'll cross much over 200 easily, though people have done it I believe.

35 is actually a very, very small load... I'd say almost anything I ever put up these days is at least in that kind of bracket, but then I've always built big rather than minimum to get the job done... the majority of my stuff is very over-designed.

Except for something tiny like a probe or probe-rover I would always, always use nuclear engines once in orbit... you only need a tiny amount of fuel to get even a large load to Mun and land it if you're transferring with that high an ISP.

Have a look on the spaceship sharing forum to get some design ideas... you don't have to download and use someone else's but it'll give you an idea of how much fuel and thrust you need to get something up there.

[leax256]

35 tonnes you can even lift with a spaceplane. Frequent poster pa1983 (I think is the username, something like that) makes gorgeous SSTOs with more than that much payload capacity. I have also built such craft myself, though mine are lacking in the aesthetics department.

Using Spaceplanes to launch payloads?!!! I can barely get my SSTO into Orbit.

[DMagic]

That's strange about the orange tanks being less stable than multiple gray tanks. I've always found the opposite to be true too. While trying to launch a fuel depo, essentially 5 orange tanks strung together, I tried dozens of times with 10 gray tanks and 5 mainsails on the first stage. Nothing I did could ever make the thing reliable, and different components were failing almost every time. No amount of adding, adjusting, or removing struts (sometimes more struts can make things worse) helped, but just replacing the 10 gray tanks with 5 orange ones worked on the first attempt.

Do you always put a small gray tank below the orange ones to avoid overheating? Maybe that is less stable than using 2 big gray tanks.

[Nao]

@DMagic

My problem with orange tanks is probably due to not using enough struts as i'm quite liberal with them. But to show what I have problem with try building this ship:

Stack of mk1-2 pod, 3x orange tank + mainsail. When put on launch pad the engine wobbles hard and, the whole thing explodes after 1-2 seconds

If i exchange the bottom orange tank with two gray ones, engine wobbles only slightly and after 4-5s middle orange tank explodes.

If i exchange both bottom and middle orange tanks for double gray ones, everything is fine with minimal wobble.

Strutting everything up helps but it increases part count and doesn't solve the problem completely. Also in my experience, heavy strutting is bad for bigger rockets (above 1000t) as the ship is very rigid, loads starts to concentrate and parts start to fail.

[Spatzimaus]

Mods help with this, of course. Especially KW Rocketry, which adds 3.75m parts; they're not more efficient or more powerful than if you'd built a stock asparagus of the same weight, but the much lower part count makes a huge difference in how big you can go. There are other mods that add parts that are just outright better, but I like keeping it mostly balanced.

My personal best is a 4000-ton lifter that carries a 450-ton payload. Yes, an 11% payload fraction isn't particularly impressive, but my design has two major advantages; first, it's an SSTO rocket, that can safely de-orbit itself after delivering a payload to LKO (or on a Kerbin escape trajectory, for missions to other planets), and secondly its shape lets me launch awkwardly-shaped payloads without any issues. (I think I can actually carry a 500+-ton payload, but the biggest I've tried so far is the 450.)

[CobraA1]

Considering the orange fuel tank is 36 tons, and I can get an orange fuel tank into orbit without using a drop of the fuel inside it, it's certainly possible .

I've got two configurations that can do it:

• Older design: 2 orange fuel tanks in center (with a mainsail), surrounded by 3 pairs of liquid boosters (6 boosters total), each booster being 2 orange tanks and a mainsail. Spaghetti staging, with each stage releasing two boosters, on opposite sides to retain symmetry.
  
• Newer design: Again, 2 orange tanks connected to a mainsail in the center. 2 liquid fuel boosters (w/mainsail, same as old design), 2 "booster" fuel tanks (w/out engines), but with the addition of 4 large Rockomax solid boosters.
  

Again, each "booster" is 2 orange tanks, if there are 2 "boosters," that's 4 orange tanks total.

That's just the lift vehicle to get it to orbit: The payload is a large orange tank, an RCS tank, a few extra things for functionality and aesthetics, and an extra fuel tank (Rockomax X200-16) so I can maneuver to the destination (usually a station) without using the orange tank's fuel. The idea is that I have the entire orange tank available at the destination.

With the newer design, when all is said and done, I lift almost 70 tons into a 100km orbit (including the still-attached center stage, with only a little bit of fuel left).

As a test, I sent my newer refuel ship to the moon via its Poodle engine, and when I was done thrusting towards the moon, it weighed 43.32 tons. So yes, very much possible.

If you want to reliably get over 100tonnes into orbit you'll have to get used to 500+ part count for the launch.

Well, I'm lifting 70 tons with 150 parts. I don't think it'll balloon to 500+ for 100 tons. The idea is to keep it simple: I use a "liquid fuel booster" design, which is basically fuel tanks + engine, arranged using spaghetti staging. I only add extras (struts, control surfaces, etc) as needed to keep it stable.

To keep the part count down, be intelligent with strut placement! Don't just place them randomly. Take a look at this:

It's strong, yet lightweight.

An arrangement like that for your struts will probably do a lot more good than randomly adding 300+ struts wherever you feel like it. Of course, feel free to experiment and pay attention to how the craft is warping/bending before it falls apart. That can tell you a lot about where and how you need to place your struts.