Heavy lifting

[Escher]

Howdy Kerbalnauts!

I've been having a few glaring issues lately. I have difficulties getting anything larger than a prodobodyne OKTO and a single solar panel into orbit, even with several mainsail engines. I don't entirely know how to lift the heavier stuff and still have enough fuel to get it into orbtit, what do I do to make sure that my fancy contraptions don't have an emergency landing right into the ground?

[Akalaël]

Mainsails are made to put in orbit several dozens of TONS of playload ! They are just overkilled for your tiny probe

Start by the begining : think that Mailsails are using tons of liquid fiuel and oxidizer at a second. Use the LV-T45, they are enough to get your probe into orbit...

See more tutorials, it will help !

http://forum.kerbalspaceprogram.com/showthread.php/25008-How-to-reach-orbit-and-a-rocket-that-can-do-it-a-walkthrough-for-newbies

Edited May 6, 2013 by Akalaël

[korda]

Payload mass is one thing, rocket mass is other. I can imagine that you tried building really big rocket and ended up designing one that barely can lift itself; try to remember that more is not always better, especially when it comes to design of rockets.

If you need to put something heavy in orbit (space station with ability to refuel ships for example) you will need a LOT of thrust at start. My heavy lift rocket starts with 12 long solid boosters and 6 main sail engines. Get used to burning tons of fuel very fast during lift-off (however be careful - if your rocket will accelerate too fast your ship can end up breaking apart. Also air works much more against you when you try to fly too fast in atmosphere). First stage should burn the most of your rocket fuel.

Also it is sometimes better to split heavy payload in two or three: building that freaking huge space station is possible if you divide it into few parts and launch each as separate mission (and then dock them of course).

Try to test some rockets with some heavy mock-up payload (like sending big fuel tank with OKTO into space). Try adding more and less fuel at different stages, or try adding and removing engines, adding decouplers and making more stages. Try adding detachable solid boosters at first stage. You may notice that adding more fuel is sometimes bad idea (rocket will spend more fuel because of extra weight of that added fuel). Try using LV-N engine for orbiting - it is super effective when it comes to fuel consumption in space, but it has weak thrust and it's heavy, so use it after gaining orbit. Use struts: those big engines can break stuff like radial decouplers and weight and acceleration can make link made with stack decoupler break too; your rocket should be stiff. If something big wobbles or moves during liftoff it means it needs struts (or better design... well that means more struts too). Extra weight of struts will payback easily - less stable rocket uses more fuel because of extra steering with thrust it requires to fly straight, at least this is my experience (not ending up with huge explosion is also good thing). Simply experiment with designs, don't go for "if it doesn't fly it means I need more of it".

If you try and still have problems, I can show you my heavy lift rocket (it isn't best design I bet, but it can put really heavy stuff on orbit).

Edited May 6, 2013 by korda

[Crush]

Hello Escher

When you would post a screenshot of one of your rockets it would be easier for us to find out where your mistakes might be. Otherwise we can just guess, because there are so many things you can do wrong.

[Louhikarme]

I seem to have hit my personal mass of stuff that gets into orbit.. i could get 40tons payload on orbit that had engines for Duna and that worked well. now my next payload was whopping 90tons and thats where i'm stumped. i did manage to get the darn thing to orbit but now i need to change the engines there for Duna fly and refuel it. all in all thats not that bad, i'll get docking practice aswell. but i would love to know the secrets of getting 90-100 tons into orbit.

[korda]

I seem to have hit my personal mass of stuff that gets into orbit.. i could get 40tons payload on orbit that had engines for Duna and that worked well. now my next payload was whopping 90tons and thats where i'm stumped. i did manage to get the darn thing to orbit but now i need to change the engines there for Duna fly and refuel it. all in all thats not that bad, i'll get docking practice aswell. but i would love to know the secrets of getting 90-100 tons into orbit.

I'm not really sure, but I can imagine that because of diminishing returns sending extremely heavy stuff into orbit is not possible at all, I'm not sure how heavy it has to be to get close to limit of what is possible with stock parts.

EDIT: I had problem of sending my ship of weight of about 70 to orbit too. I needed to burn some of it fuel too (however it has 2 LV-N engines, so it wasn't that bad). I didn't even tried to send it with Lander into space, I send Lander and docked and then my ship exploded after compressing time. I love those bugs :|

Edited May 6, 2013 by korda

[magnemoe]

I'm not really sure, but I can imagine that because of diminishing returns sending extremely heavy stuff into orbit is not possible at all, I'm not sure how heavy it has to be to get close to limit of what is possible with stock parts.

EDIT: I had problem of sending my ship of weight of about 70 to orbit too. I needed to burn some of it fuel too (however it has 2 LV-N engines, so it wasn't that bad). I didn't even tried to send it with Lander into space, I send Lander and docked and then my ship exploded after compressing time. I love those bugs :|

My tips for putting heavy motherships into orbit is let the ship work for you. add some extra engines on it, the rockomax 55 radial engine is nice for this. Put them on radial decoupler and decouple before circulating. This will get the ship pretty empty to orbit so you have to refuel it.

Yes it uses novapunch but this could also be done with multiple mainsails.

Even better is to let the nuclear engines help from 2000 meter and up. try to put the ship in the center of the asparagus. the two last boosters is then both helping you getting trust and fuel the nuclear engines.

Launching an base to Gilly, nuclear engine is activated by hotkey.

[korda]

My tips for putting heavy motherships into orbit is let the ship work for you. add some extra engines on it, the rockomax 55 radial engine is nice for this. Put them on radial decoupler and decouple before circulating. This will get the ship pretty empty to orbit so you have to refuel it.

Well yeah, but that was the issue - putting it there without need to refuel. I think that often it's not possible to avoid wasting main ship fuel though.

Even better is to let the nuclear engines help from 2000 meter and up. try to put the ship in the center of the asparagus. the two last boosters is then both helping you getting trust and fuel the nuclear engines.

Launching an base to Gilly, nuclear engine is activated by hotkey.

Current stock nuclear engine (LV-N) has poor Isp in atmosphere and very low thrust, can't really see why I should design whole rocket just to have ability to utilize that 60 points of thrust when Mainsails are making 1200 if I remember it right.

[HoY]

That 60 thrust helps lol. It increases overall fuel efficiency and that means you need less fuel to get to orbit. I personally don't add engines that are going to drop off of the payload,, however if it has them I usually build the launcher around being able to use them to help with ascent. But I always steal the fuel from the lower stages while I'm burning the engines, that way I don't have to refuel the payload, or if I do it needs much less fuel and will probably get refueled just from other crafts making quick stops by dropping off their payloads

[Flixxbeatz]

Or if you don't want to stress your computer out, check these fairly simple designs:

Picture 1: A Crew Launch Vehicle. Simple 2 strap-on + core setting with engine clusters (You can swap clusters for Mainsails to prevent stressing your computer further)

Picture 2: Standard Issue Booster (Interplanetary Ship Core as a payload). Four strap-on, asparagus cluster engines. Same as above, feel free to swap clusters with Mainsails.

Picture 3: My Standard Resupply Vehicle (A single orange tank) using a Standard Issue Lifter.

Also, for launching things like the one in picture #2, and you don't want to build a massive rocket lifter stack of boosters to put it in orbit, you must drain fuel on the payload first (so basically you're now lifting an empty can to orbit) and refill it later by running resupply missions. It's all about patience and strategy

[magnemoe]

Well yeah, but that was the issue - putting it there without need to refuel. I think that often it's not possible to avoid wasting main ship fuel though.

it makes launches easier, also it much easier to refuel in orbit than to build something stable.

Current stock nuclear engine (LV-N) has poor Isp in atmosphere and very low thrust, can't really see why I should design whole rocket just to have ability to utilize that 60 points of thrust when Mainsails are making 1200 if I remember it right.

True, however you don't want to push more than an large gray tank with an LV-N that is no problem to lift with mainsail main stage with two boosters.

If you want to move 100 ton you want at least 5. run in parallel with an mainsail it will increase isp with 25%, you activate it at 2000 meter, here the isp is better than chemical. Also for long cargo the rocket can easy become very unstable, this is the main reason I launched the base like this.

[capi3101]

I seem to have hit my personal mass of stuff that gets into orbit.. i could get 40tons payload on orbit that had engines for Duna and that worked well. now my next payload was whopping 90tons and thats where i'm stumped. i did manage to get the darn thing to orbit but now i need to change the engines there for Duna fly and refuel it. all in all thats not that bad, i'll get docking practice aswell. but i would love to know the secrets of getting 90-100 tons into orbit.

I'm not really sure, but I can imagine that because of diminishing returns sending extremely heavy stuff into orbit is not possible at all, I'm not sure how heavy it has to be to get close to limit of what is possible with stock parts.

The trick in short, as many would eloquently put it, is MOAR BOOSTERS. Yes, there is a diminishing return on how much you can put into orbit as once; it's more often than not a limitation of your memory, though. The key is to have plenty of stages, to make sure you follow a fuel-optimal ascent (by keeping your speed close to Kerbin's terminal velocities), and to make sure your TWR is close to optimal the entire way up (1.2-2.5, I'd say). Struts and control surfaces are also essential, particularly for the lower stages. RCS is helpful once you've finished the ascent burn to get the payload on the desired trajectory for the orbital insertion burn. I've put up as much as 130 tonnes in one go with stock parts; it is possible and there are folks here who will gladly help you your designs if you need them.

[korda]

Sometimes I wish that there would be option in VAB to control how much fuel I want in particular tank...

[HoY]

There will be in a future update.

[Escher]

Ah, thanks guys. Sorry I didn't reply earlier. Someone requested a picture of a spaceship of mine:

What is wrong with this design currently?

[Alistone]

Currently it doesn't have enough thrust.

Try replacing the 4 tiny radial engines below the orange tanks with Mainsail engines (really big).

And add another 4 large orange fuel tanks above the current tank 4 radial orange tanks. That will probably get you to orbit just fine.

From there you can probably figure out how to do additional tweaks. Alternately you could just add more of a different engine.... but from what I see you need more thrust.

EDIT: You see I'm asking you to add essentially 10x as much thrust with thos big engines; and then I'm asking you to double the fuel load. I'm just "eyeballing" the simplest way to add get to a better T/W ratio. You could do all sorts of redesigns that will be even more efficient. You could find a way to stack sets of 3 engines beneath each orange tank and then you wouldn't have to add more fuel. I'm just trying to keep it simple & direct.

EDIT EDIT: Also, by using fuel lines with no symetry you can route your fuel to empty just 2 radial tanks first; decouple them, then run the other 2 radial tanks empty, then decouple them with still a full center tank. This makes your ascent more efficient because you aren't hauling the weight of empty fuel tanks all the way up with you.

Edited May 6, 2013 by Alistone

[HoY]

You also have 2 ASAS modules onboard. You can remove the lower one and save a little weight.

You want the center engine or engines firing the whole time as well, not just after the outer engines run out of fuel.

[ruiluth]

This is a simple and light design I learned from Scott Manley. Use 2x symmetry. [] is a FL-T800 Fuel tank, ^ is a LV-T30, = is a stack decoupler, and < is a TT-70 Radial Decoupler. & just represents the payload.

&

=

[] [] []

[]<[]>[]

^ ^ ^

the middle engine is actually a LV-T45 for the thrust vectoring. add struts and winglets and feed fuel from the outer tanks into the center ones. Used correctly, this design can put a small craft on the Mun and return it home.

This is more or less the design i used to put my first kerbal on the mun.

EDIT: also if you don't use mechjeb you may want to put ASAS on it

Edited May 7, 2013 by ruiluth
cuz i forgot something

[Flixxbeatz]

Ah, thanks guys. Sorry I didn't reply earlier. Someone requested a picture of a spaceship of mine:

-snip-

What is wrong with this design currently?

Put some mainsails for additional power. Employ asparagus staging, also.

And it looks wobbly. Put some struts on it, especially if you have mainsails as core.

[TaranisElsu]

Your design is pretty close. Good job. As has already been said, you have enough fuel but not enough thrust.

I recreated your rocket as best I could based on the picture, and I recommend the following changes:

• Replace the center engine cluster with a Mainsail engine. It single-handedly solves your thrust deficiency.
  
• If the rest of your engine clusters are LV-T45's, I would replace them with LV-T30's. They have a little more thrust, and you won't need the thrust vectoring because the center Mainsail will provide plenty.
  
• Add fuel lines from the boosters to the center stage (outer orange tanks to inner orange tank). This will make it empty the outer tanks first so you can drop them, and still burn the center engine for a while longer. You can do the "asparagus" staging, but it is not necessary to take it that far.
  
• Get rid of the second ASAS -- every one after the first is only extra weight because they do not do anything more. SAS are additive though, so you could add lots of those for more stability, but I didn't need it.
  
• Move your separatrons so that you have one at the top and one at the bottom of each booster, or one on each side of the center of mass. The way they were, the boosters ended up moving down and together, blew each other up, and almost took out the center engine.
  
• Do you have any RCS ports? I see the RCS tank but no RCS ports in the picture.
  
• Are you hoping to bring your crew home? I see no parachutes . And you would need a separator between the Mk2 Lander-can and the RCS tank (I added two separators).
  
• Add a lot of struts. The whole thing wobbled around quite a bit the first time that I sent it to the launch pad.
  

Here are some pictures in the VAB:

Here it is in orbit:

Returning safely to Kerbin (I had a small staging malfunction, separate the crew modules from the rest of the rocket and then pop the parachutes and split them):

Launching tips:

• Make sure you do not overheat the Mainsail. Two notches from maximum is enough (about 80% or so).
  
• Go straight up to 10 km, then start your gravity turn, turning to the East (90*), gradually decreasing your pitch until your nose points to the horizon at around 40 km.
  
• Cut the throttle once your apoapsis is above 80-100 km.
  

BTW: I had another 2200+ dv while in orbit, enough for a round trip around the Mun .

I recommend getting either Kerbal Engineer (http://kerbalspaceprogram.com/0-18-1-kerbal-engineer-redux-v0-5/) or MechJeb. They both show you your calculated delta-v and thrust/weight ratio per stage. Very important numbers to design around. Or get out a calculator if you do not like mods

Also, Kerbal Crew Manifest will help you fill the lander can (http://kerbalspaceprogram.com/18-1-kerbal-crew-manifest/).

Happy flying!

[Louhikarme]

Allright, after reading some stuff on about linking fuel lines, i was doing that already but not with this tho. So now i can get this monstrosity to nearly orbit, i just run out of fuel when i'm around 80km and start burning for circular orbit, and the 8 nuclears don't have enough punch for the payload. but, i think i'm on the right path, just couple tweaks more. only have one pic tho.

[smunisto]

Use a mod like Engineer or Mechjeb to detemine when you stop pushing the TWR ratio up and it starts dropping due to too much engines/fuel.

You have too much tanks. Try using less tanks and more asparagus.

[Louhikarme]

Use a mod like Engineer or Mechjeb to detemine when you stop pushing the TWR ratio up and it starts dropping due to too much engines/fuel.

You have too much tanks. Try using less tanks and more asparagus.

i got engineering redux. its great. currently on that version i drop 2 engines at a time. Just need to fine tune the sweet spot now.

[AstroRick]

I had built what I considered to be a good "mothership" or "core" for sending probes, landers and other things off to the planets. It used a large spherical tank (mod), four nerva engines and various docking, power and science devices such as an ISA mapsat dish.

Full, the ship weighs about 230 tons. Standard practice was to launch a fueless core (much much lighter) into orbit and then run fuel up to it. The large spherical tank holds about 7 orange tanks worth of fuel and the refueling ship I was using could reliably supply about two orange tanks worth of fuel each flight. I decided I wanted the turn-around to be faster between the launch of a core and the start of a mission to the planets!

I started simply by seeing what would get the core off the launchpad "with some attitude" Eight orange tanks with mainsails. Then I did the same for the "Tanks, core and mainsails" package, working my way down, stage after stage. Lots of struts, lots of moving of various engines and lots of messing with staging as you might imagine! And oooh... the spectacular failures....

Finally... success! A ship which would reliably put over 200 tons into a 100km circular orbit, fueled and ready for whatever I wanted to dock on top of it. I've flown the core from Moho to Eeloo.

Here is a picture of the final launch "package" in the VAB.

It seems pretty stable on the way up, but I would be a bit scared to fly it without mechjeb. So the only mods used were sphereical tanks and mechjeb on this thing.

Edited August 15, 2013 by AstroRick

[AstroRick]

Addendum. I didn't use any kind of vegitable-based staging for that monster. After a few successful launches the thing got all explody on me! I did a complete redesign and was able to halve the parts used, all because of asparagus staging! It really is the way to go. I'll post pictures soon.