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Tips on building rockets?


Abbubner

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Hey to all you smart people, I've began to realize that I'm awful at building rockets. Does anyone have any tips to building effective rockets? (In dumb language, please. I'm not all that smart when it comes to space travel.)

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Well, it is all changing dynamicly with what payload you are carrying. But if you want to see how to design a rocket, just look into "What did you do in KSP today?'' thread ,i post a lot in there and you can get inspired by one of the designs.

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Just now, cratercracker said:

Well, it is all changing dynamicly with what payload you are carrying. But if you want to see how to design a rocket, just look into "What did you do in KSP today?'' thread ,i post a lot in there and you can get inspired by one of the designs.

Thanks for that, I'll look into the thread the next time I'm playing. 

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Start with a really small rocket, and make it work. Then build a larger stage under it and tinker with that until it works. Then add another stage. Repeat until it reaches whatever your goal was. :D

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Start like the game asks you. Start get higher Leave atmo go for Orbit and don't Skip Till it is mostly goes planned. Unplaned Kabooms are part of the game.

Look precisely when you get the problems. Hight, maneveur or wild flips, maybe woble or sth like this? Every problem has a cure. Wiki will help a lot and search funktion in the forums. But look precise if the given tipps are for your install. If this don't help than ask a precise problem you need a solution like mentioned above.

I love to be more helpful but without a screenshot and precise notification it is Impossible.. .

And One more try out the Missions and Tutorials ingame and aktivate the Stock vehicles to see how they are build?

Funny Kabooms 

Urses 

Edited by Urses
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Thanks for all of these replies, and to answer your questions, my real issue is that I'm not sure if there's a specific thrust:payload ratio that I should follow. Is there a specific amount of thrust I should creat to a ton? And how do I factor in the fuel? I hope this helps, and if not, please tell me. I don't want to leave you all in the dark. 

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Here's a quick rule of thumb - lop a zero off the end of the thrust in kilonewtons of any engine in the game, and that will give you the approximate amount of thrust in metric tons.  Thus the Poodle in vacuum gives 250 kN of thrust, which is approximately 25 tons.  Do the math so that the sea level thrust of your engines is somewhere between 1.4 and 1.7 (depending on your personal preference and a bunch of other factors) when initially lifting off the pad.  For example, a 14 ton rocket with 200kN of thrust off the pad should be good, since the initial TWR is approximately 1.42.

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7 minutes ago, Norcalplanner said:

Here's a quick rule of thumb - lop a zero off the end of the thrust in kilonewtons of any engine in the game, and that will give you the approximate amount of thrust in metric tons.  Thus the Poodle in vacuum gives 250 kN of thrust, which is approximately 25 tons.  Do the math so that the sea level thrust of your engines is somewhere between 1.4 and 1.7 (depending on your personal preference and a bunch of other factors) when initially lifting off the pad.  For example, a 14 ton rocket with 200kN of thrust off the pad should be good, since the initial TWR is approximately 1.42.

This is really helpful, thank you. 

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@Abbubner

Norcalplanner gave you a good advice.

If you have problems to do the maths (like me with thrugling around with calculator 'till it "feels" right) and don't mind to use mods. Than you can try out KER(Kerbal Engineer Redux) or MJ(MechJeb). They do a lot this way.

And no i don't wish to Start a diskussion witch one is better! 

Funny Kabooms 

Urses

Edited by Urses
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Sometimes I write walls of text on certain topics, and then I save the link so that I don't have to write it again in the future. And the thing that I keep re-linking by far the most is a treatise on mass fractions and how they influence the way you build rockets in KSP. Now that you have a rough idea of how much liftoff thrust you should aim for, you can use the advanced information contained within that link to make your rocket stages go the distance and give you your money's worth. :)

Also, did you know that we have an entire subforum dedicated to asking questions about how to do stuff? :wink: Not only is there a wealth of information to browse among old questions and a lot of friendly people eager to help with new questions, but there's also a Tutorials sub-subforum with pre-written guides on various topics.

 

Edited by Streetwind
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52 minutes ago, Streetwind said:

Sometimes I write walls of text on certain topics, and then I save the link so that I don't have to write it again in the future. And the thing that I keep re-linking by far the most is a treatise on mass fractions and how they influence the way you build rockets in KSP. Now that you have a rough idea of how much liftoff thrust you should aim for, you can use the advanced information contained within that link to make your rocket stages go the distance and give you your money's worth. :)

Also, did you know that we have an entire subforum dedicated to asking questions about how to do stuff? :wink: Not only is there a wealth of information to browse among old questions and a lot of friendly people eager to help with new questions, but there's also a Tutorials sub-subforum with pre-written guides on various topics.

 

It is really great that I'm getting so many people and locations on this forum willing to help me. Thank you, and everyone, for your help! :kiss:

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Think like a dart. Weight at the front, fins at the back, and it'll fly fair.

Other than that, a more specific question is really quite important because there are literally thousands of configurations that the stock KSP parts will reach orbit in :) 

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Alright, let's talk about some simple facts and terms when in comes to rocket-building.


TWR (thrust weight ratio) : This number tells you how fast your rocket is going to accelerate on a given planet. When the number is higher than 1. the rocket is capable of ascending on that planet. Rockets like the Saturn V, start with a TWR of 1.2. If you've KER or mechjeb installed, you can check of your rocket will lift. Also, for a working rocket, only the first stage needs to have an atmospheric TWR higher than 1. If your TWR is lower than 1 and such a craft is currently falling towards the surface, then the craft's engines won't have enough thrust to slow down for a soft landing. You can consider adding more boosters, more engines or a more powerful engine. 
eb56e634c4b30235deeaf0a0708fbfcf.png

  • F_{T} is the thrust of the engines
  • m the total mass of the craft
  • g the local gravitational acceleration (usually surface gravity)


Delta-V : This is a very important one. The delta-v simply is the amount of energy/power/force a rocket can produce. Mostly it's represented in m/s. For instance, to orbit Kerbin, your rocket needs ~3400m/s delta-v. The more delta-v the rocket has, the more you can do with it. Here's a very handy delta-v map where you can check how many delta-v you need for certain missions. 

ISPISP stands for the specific impulse impulse of the engine, that doesn't make thing much clearer I think haha. Anyway, it gives you the efficiency of a engine. A propulsion system with a higher specific impulse uses the mass of the propellant more efficiently in creating forward thrust, and in the case of a rocket, less propellant needed for a given delta-v. This means the engine is more efficient at gaining altitude, distance, and velocity. This is because if an engine burns the propellant faster, the rocket has less mass for a longer period of time, which makes better use of the total force times time that was acquired from the propellant.

Gravity turn : A gravity turn or zero-lift turn is a maneuver used in launching a spacecraft into, or descending from, an orbit around a celestial body such as a planet or a moon. It is a trajectory optimization that uses gravity to steer the vehicle onto its desired trajectory. It offers two main advantages over a trajectory controlled solely through the vehicle's own thrust. First, the thrust is not used to change the spacecraft's direction, so more of it is used to accelerate the vehicle into orbit. Second, and more importantly, during the initial ascent phase the vehicle can maintain low or even zero angle of attack. This minimizes transverse aerodynamic stress on the launch vehicle and prevents burning extra fuel, allowing for a lighter launch vehicle. 

 

So the basic you also need to know. If you have a payload of 1000kg, and your last stage has 500 delta-v. reducing the payload to 800kg, will give the last stage 600 delta-v. Always try to make everything as light as possible. The seconds stage will gain even more delta-v if you reduce the last stage to the initial 500 delta-v. Reducing weight can be done by reducing the abliator in the heatshield, adding less solar panels, adding more efficient engines etc. Always try to make you payload or last stage as light as possible, it can give you a huge advantage. 

Stability on your rocket is also very important, you don't want that your rocket tips over during your gravity turn. This can be done by putting the draggy parts at the bottom, Fins for instance. If your payload fairing is bigger in diameter as you rocket, you probably need some extra fins to counter those forces. 
rktstab.gif

When your engine stop, you don't want your rocket to tip over and explodes the hell out of you, you want to let if fly as a lawn dart.

What also is very important are the following info:
CoM: Center of Mass.
CoL: Center of Lift. (more important on planes)
CoT: Center of Thrust. 

Always, you need to be sure that your CoT is in line with the CoM. Otherwise you will create a momentum/spin on your rocket. So with one engine, always place it under the CoM, with more engines, always place them in symmetric order.

Obviously there's a lot more to explain, especially when it comes to rockets in real life, but that for another time.
Scott Manley has great videos on youtube where he explains things about rocketbuilding etc.

And just keep trying, optimizing and trying again. One day you will be the rocket geek of your family. :) 

~Dr.Licor  
 
 

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Welcome to the forums!

There has been some great advice, I absolutely must recommend Streetwind's work on mass fraction. It is incredibly useful once you start getting interested in the more technical side of things. Norcalplanner has also given you great advice, not to mention DrLicor.

If you are more visual and interactive, I must also second Scott Manley's stuff and I will, again, do a bit of shameless self promotion in the sense that I've done up-to-date video tutorials for specific elements of the game and I make a point of trying to not overload the viewer with the physics behind everything and stick to the practical stuff. You can find the link in my signature.

Edited by Ohm is Futile
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you need to attention the mass,aero force.,thrust   and remember you need reaction wheels for stabilising add antennas solar panel    bigger thrust at bottom (first stage)smallest thrust at the last stage   heavier at bottom lighter the top      and be careful aerodynamics can stress your rocket apart and... explode caution the fuel that is it enough 

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