Rocket Launch & Gravity Turn

Ten meters per second squared!

Sorry Guys!

Firstly i would like to apologise to my viewers and readers for the lack of content the last couple of weeks. I've been a bit spaced out....  ;)

Side Flight

Alright, so currently what we have done is built a semi-advanced rocket that can reach space quite easily. Now what we want to is to understand the initial launch and gravity turn.

The gravity is extremely important in space flight for two reasons. The first reason the gravity turn is so important because it is fuel efficient. This efficiency directly relates to the thrust to weight ratio, as the ship ascends the fuel is being consumed at the same time, putting the ship on a 45 degree angle offers less resistance from aerodynamics and in turn allows the rocket to fight the forces of gravity at a more efficient rate.

What Goes Up.

Now there is a downside to how you approach the gravity turn. We all know what the prograde vector looks like now, now one option is to follow the prograde once above 10km to an almost horizontal flight path, what this will do will have a much slower approach to the safe 70km space zone, but will require much less thrust to reach a stable orbit on you periapsis. This can be made even more efficient by using an engine that uses much less fuel in a vacuum once the 70km apoapsis is reached.

Must Come Down.

The other approach is quite simple, just the reverse. What you do is once the 10km mark on the 45 degree angle is reached is to stay locked on the 45 degree vector. This will get the rocket to the 70km mark significantly faster, but will result in a much more lengthy burn to circularise that orbit. The sweet spot is finding the vector that is inbetween both of these approaches. That is the most efficient way to launch, but can prove extemely tricky to master. Watch the video below to get a more in-depth understanding.

Building Efficiency and Math

Lets Do The Math!

In this section of the blog i will be going over the the math and equations needed for space flight. What will be discussed is the thrust to weight ratio, how the equation works and how simple it is to build an efficient rocket following these steps.

Basically, it's the result of dividing your thrust (in newtons) by your weight (in kilograms times acceleration, i.e. kg*m/s², so... well, also in newtons). Thrust is what gets you up, weight is what keeps you down. And if thrust > weight, i.e. if your thrust-weight ratio is more than 1, you go up. If thrust < weight, you can put your engines into overdrive and you won't move an inch. For the record, the Saturn V first stage rocket engine had a TWR of 94.1. In other words, it could have lifted itself over 94 times. Beat that!

What does that mean for our space vehicle? Basically, it means that whatever we put as rockets behind our craft, it has to overcome the total weight of the craft. Which also means that, if you have multiple stages, the upper stages are just dead weight at start. Yes, yes, there are rockets in there and they might have a lot of punch, but they do not add to the thrust at start. Thrust is always only the thrust you ACTUALLY apply, not the thrust your rocket can eventually do in total.

Note that every rocket engine has a TWR of more than one. By definition. Engines below a TWR of 1 need some kind of aerodynamics on the craft to get it off the ground. The question is, though, whether the dead weight sitting on top of it STILL keeps that equation above 1. The F1's 94.1 TWR doesn't mean that the Apollo craft got shot into orbit at 100g. It means that there was a friggin' HUGE rocket sitting on top of that engine and hence it could barely get the whole behemoth up into an orbit!

My guess is that Kerbin has a gravity of about 10 m/s² (much like earth), meaning that a rocket engine rated at 200 max thrust (like the non-gimballed stock engine) can lift 20 units of mass (or 8 stock liquid fuel tanks). Given that a rocket of 1 stock command center, 7 fuel tanks and 1 engine (totalling a mass of 20.5, 7*2.5+2+1) can't get off the ground but with 6 fuel tanks it can, I'd say that should be about right. So when building your rocket, always add up the mass of the parts you assembled, multiply by 10, then divide by the thrust of the engines, but ONLY the engines that actually thrust. The more you get out of that, the faster your rocket will climb. Considering that engines seem to overheat more readily if they're operated at the TWR limit, try to get to a TWR of at least 1.7 in your first stage. My Mun rocket has a first stage TWR of 2.2, which is plenty but not overdoing it to the point where the g-forces become unmanageable.

Also, keep in mind that you will use up fuel as you climb. Your fuel tanks will get emptier with every second your engine fires, making them lighter, meaning, less weight has to be lifted. Plus, gravity decreases with distance squared, which also makes the pull of Kerbin less and less with every inch you climb. Not as much as one would wish, though.

Advanced Rocket Design

Congratulations!

Well done! you have successfully launched a rocket into the atmosphere. That's not all though, in this part we will create a more complex rocket that has multiple engines that will help us reach much higher altitudes and into space!

Bigger and Better

Now that you have launched a basic rocket, lets make it bigger and more complicated!

The parts used are as follows:

2x RT-10 Solid Fuel Boosters

2x FL-T800 Liquid Fuel Tanks

2x TT-38K Radial Decoupler

2x TR-18A Stack Decoupler
1x LV-T45 Liquid Fuel Engine
1x Mk 1 Command Pod
1x Mk 16 Parachute

The Rocket should be set up as seen below.

Below is the build video for the advanced

rocket design with the launch included.

https://www.youtube.com/watch?v=Sq8ddoQuiq8&list=PLaztmMOdP1dZcHSGen8mDRu6bol6y-PRS&index=2

Basic Rocket Design

Welcome to the first part of the KSP How to. Firstly we are going to go straight into basic rockets. Throughout this tutorial there will only be rocket based spaceflight tutorial. Planes will NOT be covered.

The type of game that should be chosen is sandbox or career. Follow the on screen instructions to find the rocket building hangar. This is where the fun begins!

The Hanger 

The hanger is where it all happens! Within this building it is possible to build absurdly massive, heavy craft to do amazing things. Below is an image from the rocket building hangar. It is an image of all the parts involved with building a rocket. I will list the different categories that they are split into.

The first one selected is Pods.

• Fuel Tanks
• Engine
• Command and Control
• Structural
• Aerodynamic
• Utility
• Science






• (Not Applicable, Mod)

A little info

All these components hold some constant attributes. They are usually; Mass, Crash tolerance and maximum temperature.

• Mass: How much the object weighs. Measured in ton decimals. eg; 0.5 = Half Tonne
• Crash Tolerance: At what maximum speed the object can collide into a surface and survive. eg; 1.2 m/s
• Maximum Temperature: At what temperature the object can survive on reentry

Try This

I have selected the Mk1 Command Pod and the RT-10 Solid Fuel Booster. Try these two components.

If you want to save your new rocket you can name it at the top of the screen with the bar name "Untitled Space Craft"

Once you have named your ship we can now save it and launch it at the top right of the screen using the save icon and the launch icon

Save:Dark Blue

Green: Launch

Teal: New Ship

Yellow: Load Ship

Red: Exit

Liftoff

Once you hit the launch button you and your rocket will be moved outside onto the launch pad as so.

From here all you need to do before you launch your vessel is press the "T" key. This enables S.A.S. It is an inbuilt device into cockpits and probes that help keep them stable and on course, though it doesn't do it all for you!

Now all you have to do is press the space-bar. Watch your navigation ball to get your speed and your altimeter to see how high you are traveling.

And Have Fun!
Link to the Video:

Introduction to KSP

Hello everybody and welcome to my Kerbal Space program guide and "How To", Trust me you will need it.

What is KSP?

Don't mind the green men if they put you off and make the game look childish. This is not the case. KSP is a very technical and difficult game to understand and get the hang of. It involves everything to do with space and all the physics that have any interaction with our solar system.
This can involve launching satellite probes to set up geosynchronous communication networks to full on surface bases on other plants. (That is not easy!)

With my guidance and your determination i guarantee you, you will be flying around happily in space in just a few hours,

The next post is about basic rocket building and how to launch your first rocket, see you there!