Have i figured out good rocket design?(Trying to avoid unneccessary engineering)

[Moonfrog]

After experimenting for quite some hours building individual rockets. I came up with a theory on how to build rockets. Which basically goes like this.

For each section, start small then make something bigger. Based on fuel size of rocket.

2nd. Make sure there is enough thrust or large enough engine/number of engines to lift that section.

3rd. keep everything as balanced and symmetrical as u can. Balanced is more important than symmetrical.

4th. This is for making whatever your ship or probe is for going further, not for lifting heavy stuff.

5th when flying, big stuff falls off first, arrange this with fuel line links and decouplers/radial seperators.

6th don't exceed green G force to so as to avoid crushing of parts on the rocket.

I could write a huge section and wall of text on experiments I did, but i'd prefer to show the final result. This rocket doesn't really do anything except fly. But what I would like to know is, is this rocket actually good? Or do I need to go back to drawing board, because I thought I had a theory that worked but it actually doesn't. here it is.

[capi3101]

The principles you've got are generally sound. As far as this being a "good design", most "good designs" are dependent on the question "what do I want to do with this rocket". If what you were going for here was a Kerbin orbiter, it's overdone; you could do the same thing with fewer parts. As the basis for a larger design (say and interplanetary craft of some sort), it has potential.

Of course, KSP is all about figuring out ways of doing things that work for you and having fun doing it, so if this works for you and if you had fun doing it, by that definition it's a good design.

[TheDarkStar]

You don't need those nosecones, currently they do nothing except add mass and drag. Also, if you built the rocket right (added enough struts) it should be able to withstand the force of your engines at full throttle. At lower altitudes, however, it does help top throttle down so that you stay at terminal velocity.

Also, you usually want to make the smallest rocket possible. That rocket (orbit or Mun landing) could be done with 1.25 or 0.625 meter parts.

[sojourner]

You could ditch 3 of those boosters, put the core stage on top of the remaining tall booster and end up with the entire core in orbit with a good portion of it's fuel. And ditch the nose cones. They are hindrances until Squad updates how drag works in the game.

[Thourion]

You don't need those nosecones, currently they do nothing...

Well they make the rocket look prettier, and if it doesnt look good it doesnt feel good ... so yeah lol

[Alguien]

As other said, without knowing for what the rocket is, we can't tell you exactly if is good

If is for orbiting kerbin is overdone

If is for extra-kerbin exploration it lacks NERVAs

alsao i am sure that tall lifting stage is unpractical, you will be between making that into two more so you can throw dead weight in more fases

[Traches]

You may want to look into the kerbal engineer mod (engineering redux it might be called?) This will give you 2 important numbers for each stage: thrust to weight ratio and delta v. TWR is what it sounds like, and you want it to be a little over 2 for your first stage, a little under 2 for your second, and somewhere over 1 for your third. Your delta v is a measure of how much your rocket can change its velocity-- it's a lot like measuring how many miles your car can go on a full tank. You'll need about 4,500 m/s to make it to orbit.

Balanced is important, and symmetry will give you balance. Rockets tend to be radially symmetric rather than laterally symmetric. The easiest way to tell if your rocket is balanced-- on the bottom left there's a button that shows your center of mass (yellow and black ball), and another that shows your center of thrust (purple looking thing). If your CoM is directly above your CoL, it's balanced.

If you're rocket's shaking itself to pieces, try adding more struts!

[sojourner]

alsao i am sure that tall lifting stage is unpractical, you will be between making that into two more so you can throw dead weight in more fases

If you look closely at the staging and the rocket you can see that the core does stage above the Rockomax cone shaped adapter.

[Moonfrog]

Its designed to so each booster section is meant to be useful in increasing the range of the pod and kerbal in it. I've had designs where i could literally add huge booster rocket sections, then after some fiddling, remove them. It would travel exact same distance into space. Its designed to make sure that each section is useful and adding to the range. I feel i often add useless booster sections that don't actually add any distance to its ability to travel, i originally thought that they did. after hours of experimenting and rearranging fuel tanks and stuff on a single rocket made of 3 rockmax fuel tanks. i Came up with that based on what i learned. Also learned that 3 rockmax fuel tanks with skipper engine, travel same distance roughly as 2 rockmax fuel engines and a skipper engine. I figured out theres this weird relation between fuel weight, thrust, between each decoupled section as fuel is routed towards central one. I discovered that by having 1 rockmax fuel tank and 1 skipper engine. Then attached 2 identical rockets to the side. It went same distance as just one rocket. Even if u used the special fuel system it still goes same distance makes no difference. But if u remove the engines, then drop the two side fuel tanks when there empty, by looking at its fuel manually. It goes much further on one engine then having 3 engines draining from 3 fuel tanks. Learning that helped a lot. Little point in duplicating rockets except for balance purposes. They need to be bigger to go further.

Next experiment is trying to figure out if using small booster rockets helps increase distance travelled. How to make small ones work well if they do. SO far everything is getting bigger i imagine u could use small rockets to help as well, but i have a feeling from my experiments that smaller rockets should not be linked by fuel. Only larger rockets should have fuel lines going inwards. Guess experimetns find out.

How do you guys build your rockets btw? Do you guys use any principles or design methods that u go by? I don't really know the math or anything so i tend to learn this way myself.

Thx for you replies. P.S i am slightly saddened about the news of the nose cones >.<

Edited August 22, 2013 by Moonfrog
thought of something.

[Alguien]

If you look closely at the staging and the rocket you can see that the core does stage above the Rockomax cone shaped adapter.

Not what i am talking about

I mean the ones with the orange tanks, that rocket is going to carry the weight of all those tanks for longer than it should, i will cut the heigh down and make it six simetry instead of 4

[sojourner]

Not what i am talking about

I mean the ones with the orange tanks, that rocket is going to carry the weight of all those tanks for longer than it should, i will cut the heigh down and make it six simetry instead of 4

Ah. Yeah, agreed. for this setup he has too much fuel in that first asparagus. Like I said, he could put the core on top of one of those tall asparagus stages and delete everything else and it would fly just as well.

Edited August 22, 2013 by sojourner

[MarkusA380]

For each section, start small then make something bigger. Based on fuel size of rocket.

2nd. Make sure there is enough thrust or large enough engine/number of engines to lift that section.

3rd. keep everything as balanced and symmetrical as u can. Balanced is more important than symmetrical.

4th. This is for making whatever your ship or probe is for going further, not for lifting heavy stuff.

5th when flying, big stuff falls off first, arrange this with fuel line links and decouplers/radial seperators.

6th don't exceed green G force to so as to avoid crushing of parts on the rocket.

Sounds like you understood the standard rules for rocket building in KSP...

Just go on figuring out better designs, you will get very powerful rockets at the end.

[Moonfrog]

If u think u can modify the rocket to fly better, I don't mind you doing so and showing a screenshot. So I could compare the two designs. Since the whole idea of what I was trying to do was test to see if it would fly rather far. According to my experiments the rockets have to be proportionally bigger, if u have identical rockets on either side, it won't go further it will just lift more. Trying to work on a design that eliminates the two duplicate rockets on the side, but keep same number of fuel tanks.

That design can get into orbit on the first stage, I mean into space where it says orbit on the navball. Then with still some fuel left it can get into a safe orbit with the second stage. I would like to see anything u can come up, one of the thingsi like about the game is designing the rocket.

[sojourner]

I recreated your core and one of the boosters, wasn't sure what the engine was on the final stage due to the fairing so I put an LT-V30 there, not that I needed it.:

http://i479.photobucket.com/albums/rr153/seattle221/Kerbal/screenshot14.png~original

As you can see from the mechjeb data it has tons of delta-v. The first stage TWR is a little low, but nothing to worry about.

And here is the core stage in orbit. You'll notice that there is still over 600m/s of Delta-v left before you have to stage to the final engine which has a wopping 4000m/s of delta-v available! For comparison you can see on the nav ball a burn for a hohmann transfer to Mun setup -which will only require 841m/s of delta-v.

http://i479.photobucket.com/albums/rr153/seattle221/Kerbal/screenshot13.png~original

So yeah, ditch all that asparagus staging. Total overkill for your payload.

I did add some fins for control and it could use more struts than I used to decrease some wobble (it's a tall rocket).

[Moonfrog]

i tested your redesign. It works really well. I guess I need to go back to the drawing board and do some more experimenting. Must be something wrong with how i'm building the side boosters. Because you taken one of the larger boosters stuck it underneath and its distance is pretty good.

Thx for showing me that. I get back to experimenting.

[Specialist290]

Been following this thread with interest, Moonfrog, and it sounds like you've managed to start getting a grasp on something known as "the tyranny of the rocket equation" without ever actually seeing the rocket equation yourself. You can find a fairly simple explanation of the rocket equation and the factors that go into it here, and I'd also recommend reading some other pages on there as well. You don't have to be able to do all the math in order to design a good rocket, but knowing how all the basic equations work can help you get a better picture of how to cut down on unnecessary mass to get the most out of your rocket once you get your head around the numbers they're giving you, and most of the math on those pages doesn't require anything more complicated than the calculator you can pull up on your computer to solve. (Note that a lot of that info talks about real-world rocket design, but most of the basic principles work just as well in KSP, at least on the rocketry side of things.)

[Moonfrog]

After attempting to read those articles, thank you for suggesting them, and failing to understand it. I decided to do some Kerbal maths with my experimenting. I came up with this. DT = A * FT where DT = distance travelled. A = movement. FT = flight time.

DT = F/m * FT where F = force. M = mass

DT = F/m (MF * FE) where MF = mass of fuel. FE = Fuel efficiency.

I then input random Kerbal numbers.

DT = 10/5 (3 * 1) = 6. I then wanted to increase the fuel mass to see how it would effect DT and realised I needed a change in my equation.

DT = F/(M+MF) (MF * FE) where M is mass that is not fuel. I then modified the MF part what is roughly the fuel tanks in my kerbal mind.

DT = 10/2+8 (8 * 1) = 8. The DT number got bigger. I tried increasing the number again more so.

DT = 10/5 +15 (15 *1) = 7.5. The number is bigger than the first one but less than the second one. Second one seemed like an easy choice. It went further in theory with less fuel, using the same engine. All kerbal mass assumes the engine will fly and this is a single or per stage. In a 2nd stage or3rd, the bit on top of the stage underneath would be added to the M. I probally should rename it to liftning Mass.

So I decided to figure out the fuel ratio to non fuel mass. 8/2 = 4.

Using this number 4. I have designed and built a rocket based on the magic Kerbal number 4. Where I build something I want to lift, a small pod. Then multiply the number by 4 and use that to determine the total mass of the fuel and engine mass to lift it. Plus other smaller parts.

Applied this to other stages.

Heres the kerbal rocket. What do u guys think? hopefully it can be interplanetary but knowing my luck so far.

Edited August 24, 2013 by Moonfrog
image failed

[Moonfrog]

I tested my own design. in order to stick to the magic number 4, I will have to add another stage somewhere to the design, for as it is, the nuclear engines do not seem powerful enough to get it easily into orbit. Of course all my kerbal maths could be wrong haha. any ideas on how to attach further stage onto the craft?

[Specialist290]

That's the thing about the nukes: They're great once your craft is in space, but they're horrible for ascent thrusters, both because of the low thrust and the low Isp in the lower atmosphere. You're best off putting them on your final stage, where their relatively low thrust isn't as much of a drawback and they can take advantage of the high Isp they get in vacuum.

And yeah, the math does take a little effort to understand, but the underlying principles are easy enough. It helps if you have something like Kerbal Engineer Redux's Flight Engineer, which lets you see how all the stats interact while you're in flight.

[sojourner]

I'm guessing that didn't even get off the ground? too much fuel for too small engines.

[Moonfrog]

it got into orbit, just the nuclear engines used up too much fuel stabilising the orbit. I have recently discovered a problem. I built my rocket wrong, it is all built on the number 3, rather than the number 4. So I have to rebuild it properly as a proper test for the magic number 4 theory.

those small engines are outputting 200 thrust. with 6 of them its 1200 thrust. Equal too 2 skipper engines. Back to the engineering department.