Can't Get Into Orbit

[Rbenard108]

Yes, Im very new at this game and not very good (I understand how to get into orbit) I just don't know what rocket to make that will let me get into orbit I have tried playing around with a bunch of rocket vareations but can't seem to get the right one. So far on my career mode these are the "branches" I have unlocked Basic Rocketry, Engineering 101, Survivability, General Rocketry, and Stability.

Please comment below the things I need to use to make a rocket that will take me to orbit around Kerbin for example:

Mk1 Parachute

Command Pod

Decoupler

FL-T800

Thanks (sorry I'am noob at this game and need help from experts)

[Vanamonde]

Here, try my example ship.

[Rbenard108]

Thanks! This is EXACTLY what I needed thank you SOO much!

[RocketBlam]

Don't trust him. That ship is rigged to explode!

Hehe, just kidding. They're ALL rigged to explode.

[LordFerret]

*I removed it, point made.*

- - - Updated - - -

Don't trust him. That ship is rigged to explode!

Hehe, just kidding. They're ALL rigged to explode.

This I can confirm. lol

Edited September 9, 2015 by LordFerret
poster in retreat

[GoSlash27]

Yes, Im very new at this game and not very good (I understand how to get into orbit) I just don't know what rocket to make that will let me get into orbit I have tried playing around with a bunch of rocket vareations but can't seem to get the right one. So far on my career mode these are the "branches" I have unlocked Basic Rocketry, Engineering 101, Survivability, General Rocketry, and Stability.

Please comment below the things I need to use to make a rocket that will take me to orbit around Kerbin for example:

Mk1 Parachute

Command Pod

Decoupler

FL-T800

Thanks (sorry I'am noob at this game and need help from experts)

RBenard,

I recommend learning and using the rocket equation. It makes all of this a ton easier.

Rwd= 2.718^[3,500/(9.81Isp)]

9(Rwd-1)(engine mass+payload mass)

_______________________________ = loaded tank mass

(9-Rwd)

If you have a small enough payload, enough fuel, and an engine that doesn't suck you will make orbit.

Best,

-Slashy

Best,

-Slashy

[Chaos_Klaus]

@Slashy:

I don't think it's helpful to just throw an already rearranged rocket equation at someone who is a KSP beginner. Also: Your calculation only works for a single stage rocket.

You are right though, that understanding the concept of delta v is important and the rocket equation is used to calculate delta v.

@Rbenard108:

You need around 3500m/s of delta v to get into low kerbin orbit. Delta v is a measure of how much you can do until you run out of fuel. If you are standing still, then do a burn spending 100m/s of delta v, you will be moving with a velocity of 100m/s afterwards. If you turn around and burn in the opposite direction for another 20m/s you will then go at 80m/s because you deccelerated by 20m/s. That is how delta v works. Every maneuver takes delta v.

The big advantage of talking about "delta v" instead of "amount of fuel" is that delta v already accounts for the changing mass of your rocket and the efficiency of your engine. You can see this in the Tsiolkovsky rocket equation which is used to calculate delta v:

delta v = ISP * 9,81m/s² * ln (wetmass/drymass)

As you can see, delta v increases when ISP icreases. ISP means "specific impulse" and is a measure of your engines efficiency. So if you use a more efficient engine, you get more delta v. You can see an engines ISP if you right click it in the VAB.

You can also see that increasing the wetmass/drymass ratio increases your delta v. So you can either add more fuel which increases your wet mass (which is the mass of the complete vehicle including fuel), or you can decrease the amount of dry mass (which is everything but the fuel). Since this ratio is inside the natural logarithm, you will get better results by decreasing dry mass, because there is diminishing returns to adding more fuel.

Ok. So what does that all mean for rocket design?

Use efficient and light engines whenever you can! Efficient engines have high ISP which gives you more delta v. Light engines keep your dry mass small, which also gives you more delta v. Engines like the Terrier or Poodle are a good choice.

The problem is that these engines are efficient in vacuum but they lose thrust under atmospheric pressure. They are useless below 20km on Kerbin. So you can not use these engines on your first stage. However, they make for great small and light upper stages. A light upper stage also means that you can get away with a smaller lower stage.

I like to think of my launchers like this (top to bottom):

- Payoad

- upper stage (high efficiency vacuum engine)

- lower stage (high thrust atmospheric engine)

- solid boosters if the thrust is too low (fire together with lower stage engine)

I use Kerbal Engineer to see if my design has enough delta v. 3500m/s is a good ball park number for LKO.

[Xyphos]

RBenard,

I recommend learning and using the rocket equation. It makes all of this a ton easier.

Rwd= 2.718^[3,500/(9.81Isp)]

9(Rwd-1)(engine mass+payload mass)

_______________________________ = loaded tank mass

(9-Rwd)

If you have a small enough payload, enough fuel, and an engine that doesn't suck you will make orbit.

Best,

-Slashy

Best,

-Slashy

Care to explain this method? I understand math, alegrebra, etc. but this equasion is meaningless unless the variables are explained.

all I see, is Rear Wheel Drive = 2.718 to the power of [3500 divided by 9.81 Internet Service Providers]

Edited September 9, 2015 by Xyphos

[GoSlash27]

Chaos Klaus,

I'm sure you're right, but in my defense I *did* say the same thing you did. Nearly verbatim

I just said it mathematically whereas you said it in English.

But your form is definitely preferable for beginners to grasp, so thanks!

Best,

-Slashy

- - - Updated - - -

Care to explain this method? I understand math, alegrebra, etc. but this equasion is meaningless unless the variables are explained.

Xyphos,

"Rwd" is just a placeholder. It stands for "wet/dry ratio". For our purposes we could use any arbitrary symbol to represent it.

The first equation is the rocket equation written backwards. It basically says

"If you start with the Isp of a given engine, then following this equation will tell you the ratio of your wet mass to dry mass that is required to achieve orbit around Kerbin."

The second equation is an expression of the makeup of a single stage rocket. The only input required is the previously computed "Rwd".

Following this equation, plugging in your engine mass and desired payload will yield "you need this mass of loaded tanks".

It will only work, however, if the engine in question doesn't choke on the surface and actually has enough thrust to lift the entire stack at 1.4G or so.

I tried to avoid the need to use definitions by using the definitions themselves as the variables. Apologies; I was in a hurry when I wrote it

Heck, it might not even be correct. I didn't take the time to verify it...

In plain direct language... what Chaos Klaus said.

If you have an acceptably efficient and powerful engine, a small enough payload, and enough fuel... you will make orbit so long as you fly it right.

Also, lots of helpful people on this forum who can help show the way.

Best,

-Slashy

Edited September 9, 2015 by GoSlash27

[Xyphos]

and I assume that 3500 is dV ?

so then....

Rwd= 2.718 ^ [dV / (sG * Isp)]

where...

Rwd: "Required Wet/Dry" mass

dV: Delta Velocity

sG: Surface Gravity

Isp: Engine Specific Impulse

all one needs to do is input the variables for any given celestial body.

thanks, but an incomplete thought is neither coherent or communicable.

Edited September 9, 2015 by Xyphos

[GoSlash27]

and I assume that 3500 is dV ?

so then....

Rwd= 2.718 ^ [dV / (sG * Isp)]

where...

Rwd: "Required Wet/Dry" mass

dV: Delta Velocity

sG: Surface Gravity

Isp: Engine Specific Impulse

all one needs to do is input the variables for any given celestial body.

thanks, but an incomplete thought is neither coherent or communicable.

^ Correction: 9.81 is not the local surface gravity, but rather a universal conversion factor. It's 9.81 for every body.

But yeah... incomplete thought is neither coherent nor communicable

Best,

-Slashy

[RAINCRAFTER]

Every thing's been done.

Someone please lock this up.

[Moach]

things needed to get into orbit....

step 1: blast up

step 2: blast sideways

step 3: keep that going until you're falling with enough sideways speed to completely miss the ground

step 4: worry about how to get back (optional)

but then again... don't we have a section for how-to's? - I think we do... hang on

...yup, we do -- and now we're there!

whoa... dude!

Magic!

[Rbenard108]

I just don't understand what rocket I need to make yeah there are numbers involved but I just need to know how to make a rocket that will take me to orbit. Do I need to use the calculation for every type of rocket I make?

[GoSlash27]

Rbenard,

No, you don't *have* to use math to do it. The math just makes it easier.

You want to have a good engine for the job. Pick one with good thrust and Isp for the boost stage. If you want to 2-stage it, then the upper stage needs an engine with good vacuum Isp for best results.

You want at least 1.4G acceleration off the pad and at least .5G up high in the second stage.

If it's too weak you need moar boosters or less payload

If it runs out of steam too early you need moar fuel or less payload.

It's a balancing act and a learning curve when you're just starting out. There's a nearly infinite number of combination of parts that will make orbit and also an infinite combination of parts that won't. You'll get a feel for what works and what doesn't as you experiment.

You also need to have a good launch profile, which is a gravity turn.

Check this guy out for a demonstration of a good gravity turn:

http://wikisend.com/download/426314/SRBLifter.craft

Just spawn it and hit "space". The first stage will follow a near- perfect gravity turn trajectory without any control from you.

It will flip shortly after staging (the second stage requires some active control), but the first stage will give you a good idea of what a gravity turn looks like.

Best,

-Slashy

Edited September 10, 2015 by GoSlash27

[Highguard]

I posted exactly what you ask for in a thread started by ... oh, you. Two days ago. Did you try it?

[Clipperride]

If this is your first game of KSP, I'd recommend science rather than career mode. You still have to unlock the tech nodes, but don't have to worry about the costs involved in learning the best way to do things. Once you get a feel for things you can return to career.

I don't find maths much fun so leaned by trial and error. Now, (almost) all my rockets achieve their goals with only slight tweaks to the original build. Space planes however..... ;-)