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trouble lifting more than 150 tons into orbit


maarten2208
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hello,

I'm having trouble lifting more than 150 tons into an orbit. so far it hasn't been such a problem because I assemble much of my ships in space. but now I want to try my luck on eve I will have to design a new launcher. does anybody have any tips to make a good launcher?

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hello,

I'm having trouble lifting more than 150 tons into an orbit. so far it hasn't been such a problem because I assemble much of my ships in space. but now I want to try my luck on eve I will have to design a new launcher. does anybody have any tips to make a good launcher?

I feel your pain - currently working on a 288T launcher myself (had one already, but let's just say it's reliability left something to be desired). You can always add more fuel and more engines, so the tricky part is making sure it won't fall part. As SRV Ron suggested, build in stages. That is, attach the very last stage to the payload first, launch it, and make sure it holds together across through the duration of the stage. Once that's working, add the second to last stage and make sure that holds together, and so on. Install mechjeb or some equivalent to get info on dV and TWR for each stage, and if you have a general idea of what sort of rocket you want, that info can guide your design. For instance, if you're doing serial staging and have the same engine type (mainsails, say) for every stage, then the optimal design will divide dV evenly between all stages. If some of your engines are more efficient than others, you'll probably want to give slightly more dV to those stages. I don't know off the top of my head what the optimal strategy is for dividing dV in asparagus rockets, but I've no doubt the answer is on this forum somewhere. Ideal TWR is apparently around 2 on the launch pad - personally I tend to end up quite a bit lower than that because I'm concerned about part counts, and so would rather use a slightly larger fuel tank than deal with cluster engines, but it's something else to keep in mind.

And use lots struts, but use them smartly - you don't want to get your part count too high, and a little bit of flex is going to hold together better than something that's completely rigid.

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I don't know off the top of my head what the optimal strategy is for dividing dV in asparagus rockets, but I've no doubt the answer is on this forum somewhere. Ideal TWR is apparently around 2 on the launch pad - personally I tend to end up quite a bit lower than that because I'm concerned about part counts, and so would rather use a slightly larger fuel tank than deal with cluster engines, but it's something else to keep in mind.

With using the Kerbal School of Hard Knocks and testing, I found that placing a pair of Mainsails on the last asparagus pair with Skippers on the rest gave me the best performance on the one fuel can design. All mainsails used too much fuel due to high thrust ratio, all skippers used too much fuel due to low thrust weight ratio.

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HfUTTmt.jpg

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hello,

I'm having trouble lifting more than 150 tons into an orbit. so far it hasn't been such a problem because I assemble much of my ships in space. but now I want to try my luck on eve I will have to design a new launcher. does anybody have any tips to make a good launcher?

MOAR BOOSTERS!

Yo dude, I heard you like struts, so now you can strut with your struts stuck to struts on your struts!

Some dry ice to keep your cpu from meltdown might be a good idea.

With pure stock, I've manages to get 7000tons in orbit. Took less than 3100 parts, and about 6 hours realtime.

With KW rocketry, and joint strengthening, the limit seems to be somewhere towards... too much!

Basically, I usually put an efficient asparagus stage, on top of a brute-force pancake stage, on top of a very brute force pancake stage, wrapped in an onion of SRB.

SRB gets you up to about 4-5km, very brute force pancake gets you to 12km and some speed, after that it's easy.

Pancake stage rather than asparagus, as you need the sheer violence that enough Mainsails will give you.

.

How wide a pancake? For me, the limit is about 5 concentric layers on the bottom layer.

That is 1 + 6 + 12 + 18 + 24 + 36 = 97 oranges + mainsails.

You may need to move your launch from launchpad to runway, to avoid terrain problems.

Try something like this: Image shows seconds stage, seperating from first stage. Below that was a layer of ~149 SRB

u3bap5l.png

GHszHuc.png

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Bigger.

Asparagus.

(and on your outermost asparagus, you don't need engines on all tanks. engines have mass, and removing 8 of them adds a ton of effeciency. Drop tanks, as I call them, can add a bunch of delta-V for really large lifters. Remember, while under 10km, anything faster than 150m/s is wasting a ton of fuel pushing against the atmo. If you are having to throttle down a bunch, then you should consider removing engines.)

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