NOTE: Realism Overhaul career is handled by the mod Realistic Progression Zero (wiki, with tutorials, HERE). If you still want to attempt "stock" career in RO (and note, it is very broken), read the following guide.

If you are totally new to Realism Overhaul this is the guide for you. I assume that you have played KSP at least once and are familiar with common terms (dV, TWR, and such), if not please look them up before reading this guide.

I assume that you have the following mods installed beside Realism Overhaul:

• Real Solar System (our solar system that fits perfectly with the modpack)
• Procedural Parts (allows to configure parts like tanks in size/volume to avoid stacking of such parts)
• TAC Life Support (when going realism go full realism!)

Known issues

Depending on your system and specs, it is possible to experience massive FPS drops when looking at engine smoke and exhaust. If that happens to you, remove the mods "Real Plume" and "SmokeScreen" from your installation. It looks a lot less awesome without those, but it fixes the issue.

Selecting difficulty

Allow Reverting Flights - If this is the first time you are playing Realistic Overhaul, absolutely do select it. Even if you are a KSP veteran this mod changes so many things about KSP that you can expect your first 20 or so rockets to crash and explode.

Allow Quickloading - Strongly recommended. Sadly this modpack brings KSP to the limits, so crashes happen more frequently. Make sure to check the "Low RAM" guide on the forum!

Science Rewards - In RO you cannot get as much science from Earth/Kerbin as you are used to, in fact most biomes hand out a flat 0 points except for crew reports. If you reduce this value don't push it below 50%.

General changes

If you use the complete pack, you now have several launch locations to choose from. Just go to the Tracking Station and select your favorite place to launch from. Depending on your settings not all of them can communicate with unmanned vehicles, therefore it is recommended to begin with the default launch facility (Cape Canaveral)

You start with a completely different set of engines and parts, including many different fuel types. Once you begin to build advanced rockets, I strongly recommend to read the detailed description.

Most engines cannot be throttled in RO, which forces you to either calculate perfect burn times or/and switch them off/on to adjust speed. I strongly recommend to read the False KSP Lessons page for further significant changes.

Most parts can endure a lot less heat than in stock KSP, so expect your parts to explode a lot thanks to temperature issues. Heat shielding and dissipation becomes mandatory very soon.

Building your first rocket

Before you go into VAC make sure to grap the "Launch our first vessel!" and "Gather scientific data from Earth" contracts, which is what we are going to do in a few minutes.

As always we start with the Mk1 Pod. While this looks about the same as in stock KSP, it is actually much different. If you right-click on it you will be presented a long list of settings for it, including tanks and various control settings. The "Show UI" button allows you to configure those tanks in detail (more on that later).

In addition the Pod now comes with a built-in heat shield and a set of RCS thrusters which compensate the lack of a reaction wheel. It is also slightly larger in size (2m) which sounds like a minor change, but in fact this is a significant change thanks to the FAR aero calculations.

For the moment leave those settings alone and put a "TR-18A Stack Decoupler" followed by a "Star 48 (PAM-B) Solid Kick Motor" on the bottom, and a "RealChute Cone Chute" on the top.

Notice the difference in sizes or various parts. While this is only a minor annoyance in stock KSP, it actually is a significant issue in RO. On the lower screen you will find the FAR button that will allow you to display the aero effect on your rocket in more detail. Click it then select "Transonic Design" and activate the first button "Show cross-sectional area curve". You will now see you basic aero model that will be used for calculations.

The smoother this line is, the smoother your rocket will glide through the air. The curvier that line is, the more turbulences (aka rocket flip to death) you will experience. And now you see why that "minor" gap between those components actually is an issue. According to FAR (in Transonic Design) the critical Mach number is 0.54, which means this rocket will become mostly incontrollable at about 180 m/s.

We cannot change the size of the rocket (yet), but we can change the size of the chute on top. Right-click it, then click "Previous Size" twice to shrink it to match the Pod size. FAR sometimes takes a moment to update the curve, you can force that by rotating the craft. Now the critical Mach number didn't get any better (worse in fact), because the gap below the Pod still exists, but the curve got somewhat smoother, reducing the general turbulence a little.

Since we already know that the rocket is going to shake, we need to compensate for that. Switch on CoM and CoF display and add 8 Basic Fins evenly around the bottom of the rocket. The CoF should now be just on the CoM, which isn't perfect, but once the rocket ignites and looses fuel, that should solve itself. If you switch KER to Atmospheric display (we are not going to leave the atmosphere for now), you see that it has a TWR of 1.3, which is about what we want to have.

The First Launch

Now that we have a basic rocket assembled, we can launch it into the air. Make sure to grab the crew and EVA report on the launchpad, then ignite the engine. Let it raise to about 100 m/s then do a slight tilt and let gravity handle the rest. Note that you cannot rotate the rocket without the use of the RCS thrusters, but for the first flight that doesn't matter much anyways.

Once you are at the apoapsis - which should be about 13.4km - use the RCS thrusters for a turn, then detach the pod and activate the chute. It would not be entirely necessary to detach the pod for this flight, but for future returns it becomes necessary until you have better landing options, as the re-entry heat would otherwise destroy your parachute. The pod has a built-in heat-shield, which should be sufficient for your first few flights.

If everything goes well, your Pod should sink safely to the ground, and the completed missions should award enough money and science to build the first rocket that can escape the atmosphere. If you have the revert option enabled, I recommend to let the rocket launch a few times with different configurations like without the fins, to get a feeling on how the FAR aero system works.

The Second Launch

At this point you should have enough science to buy the Basic Rocketry to get your first steerable and switchable engine, the LR105. Note that it cannot be throttled, which means you actually need to switch the engine off and on to adjust thrust. But this allows you to stay below the critical Mach value and prevent overheating, without having to go through lengthy calculations on how to do that without such an engine.

Again start with a Pod, put a slightly smaller chute on top, but this time we put a Procedural Stack Decoupler below followed by a Procedural Real Fuels Tank. The benefit of using those parts is that you can perfectly align it with the size of the rest of the rocket, which significantly reduce the turbulences during flight. Put the new LR105 engine below and as many fins as you can fit (24 total) and a Communotron on the Pod tilted down to avoid aerial forces, since this time we actually need to send a few reports back home.

The Decoupler and tank should be at 1.9m diameter and the tank at 5.2m length. This should perfectly align with the rocket and put it just below 18t mass. Note how the aero curve this time, thanks to the adjusted sizes, is much smoother, which will significantly reduce the turbulence mid-flight. FAR reports a critical Mach number of 0.73, which is not yet perfect, but a lot better than the last rocket. The huge amount of fins should adjust for that and once again bring the CoF just below the CoM for a smooth ride.

Now we are going to adjust the tanks to actually contain the right fuel. The engine consumes Kerosene and Liquid Oxygen, and the built-in RCS thruster works on HTP. If you right-click on the tank, the game should have detected the engine you put on the rocket and should offer a 38.2% Kerosene / 61.8% Lqd Oxygen mix in the menu. Click it and the tank gets filled up with exactly that. Make sure to ramp up the Utilization to 100% and we are good to go to work on the Pod settings.

Since we won't need most of the tanks currently in the pod (like waste tanks and such), first click on "Remove All Tanks", then on "Show UI" to add new ones. In the new window select an HTP tank and add it. Whenever you add a new tank, the system will use all remaining capacity for that tank, but since we don't need hours of RCS burn time, change the value to 20 and click "Update". Repeat that process to add 150 "Oxygen", 2 "Food", 1 "Water" and finally ElectricCharge, and leave the latter at the maximum setting (225.3). You can check on the TAC tab that the added oxygen, food and water will keep the Kerbal alive and nourished for about 1 day, which is a lot more than we actually need, but two sandwiches and a bottle of water don't weight much anyways.

In total you rocket should have 30 parts, 17.8t weight and a TWR of 1.41. Since the engine cannot be throttled we cannot change that TWR, but have to actually work with the on/off switch of that engine. Later you will usually assign a "Group ID" to each engine, to adjust them all at the same time with the new engine menu, but for now we leave it as it is.

Launch into space

Make sure to grab the "Escape the Atmosphere!" contract as we are going to do exactly that, activate SAS then launch. Again at 100 m/s do a slight tilt, then once it has stabilized switch off SAS and let gravity do the rest. This time however you need to keep a close eye on the current speed. While we have compensated for the instability, we did not (and cannot) compensate for the temperature thanks to friction. Right-click on the engine and whenever you get too much drag switch it off for a while to slow down, then switch it back on. This will get a little tedious, but for now that is the only option.

Our target is about 135km apoapsis, which is just outside the atmosphere (130km). Make sure to grab the upper atmosphere science and send it back down to earth and the space near Earth a few moments later. Then prepare for the descent.

As said before the decoupler will be an important part in our rocket design for now, as the RCS thrusters are the only option to turn around the rocket, but are not strong enough to actually do so in a reasonable manner. If you don't turn, the re-entry heat will melt the chute, and even if you manage to turn around in time, the weight of the engine would drag the rocket down way too fast, and once again melt the chute. The only option at this point is to detach the Pod, turn it around retro-grade and let its internal heat shield do its magic. If the Communotron is facing towards space, it should not melt either.

If everything goes well, you should end up at <300 m/s at about 22km altitude at witch point you can launch the chute. Note that it only partially deploys yet, it will fully deploy later. Watch the pod drift into the ocean at which point you can then recover it.

Further rockets

At this point you should know the basic things to build further rockets, but keep the lessons learned above in mind:

• Aerial forces will flip or even tear your rocket apart if you don't compensate. Make sure to check with FAR on your design.
• Many parts will melt thanks to friction, check the maximum temperature on each part before you use it. Service Bays are your friend.
• Engines require careful planning so they don't over-shoot or under-shoot. Multiple stages to adjust TWR are a requirement for most intermediate rocket designs.
• You can adjust about everything on those modular tanks and several other parts, even just a Pod filled with Kerosene/Lqd Oxygen with an appropriate engine can actually launch. Use that to your advantage.