Early Orbital Rocket Tutorial

Early Orbital Rocket Tutorial

After you've completed the 3000 km downrange contract, the next big step is to launch a satellite into orbit. To demonstrate one way of accomplishing this important milestone, this tutorial will show you how to build an analog of a early American rocket, the Thor-Able. As with the early career tutorial, please note that this is simply one way of progressing in an RP-1 career. There are many paths to success!

This will be a two-stage rocket, using an AJ10 (Early) upper stage and an LR-79 lower stage. Both of these engines are unlocked in the 1956-57 Orbital Rocketry tech node. The rocket will also use integral fuel tanks, which are lighter and more capacious compared to earlier conventional (separate structure) fuel tanks.

Let's design the rocket from the top down. First, create a satellite using a procedural avionics part. This extremely boring satellite uses the TL3 science core configuration. This tech level reduces power draw dramatically, while also continuing to reduce mass compared to earlier versions. This particular science core has a radiation detector, a thermometer, and a barometer all integrated into the core (select the "Configure Experiments" button to enter this menu), and is therefore capable of completing the First Science Satellite contract. It also has 10,000 EC, which will allow it to power the experiments in orbit and broadcast the results back for quite some time.

Next, we're going to add a fairing base and two fairing halves. You can see that this rocket uses a 1.25m diameter for the upper stage, which is wider than the 0.81m diameter used historically. There are a couple reasons for doing this, including reutilizing existing 1.25m tooling that you'll already have if you've been flying X-planes. However, the main reason is aesthetic - the original Thor-Able looks like an electric toothbrush, which is suboptimal. This rocket has an appearance closer to a later Thor-Ablestar or Thor-Agena.

Once you've placed the fairing base and fairing halves, it's time for avionics which can actually control the upper stage. Select another procedural avionics part and attach it beneath the fairing, adjusting it to 1.25m diameter. Configure the avionics to use the Near-Earth TL2 "Early Avionics" configuration, and set the controllable mass to be around 2.5 tons. Add a few hundred EC to power the avionics, and leave the RealAntenna stuff alone - the defaults are fine for this early rocket.

Next, select a procedural integral fuel tank, and place it beneath the avionics. Increase the diameter to 1.25m and the length to around 1m, and select the HP (high pressure) variant in the tank's PAW (aka the right-click window). Be sure to increase utilization to the maximum of 95 percent to take full advantage of the tank's capacity.

We'll need a way to provide ullage and attitude control, so select the smallest RCS thruster part (the 28/45N one) and place four of them near the bottom of the fuel tank. Configure the RCS thrusters to use HTP, which is a nice compromise between cost, power, efficiency, and fuel volume for early rockets. Click on the "Show Tank UI" button, then add just 1 or 2 units of HTP to the tank.

Select the AJ10 Series (Early) engine to power this stage, which will have the beginning AJ10-37 configuration. Place it on the bottom of the fuel tank, then fill the remainder of the fuel tank with UDMH and IWFNA using the button in the PAW. Fine-tune the length of the tank so you have somewhere between 1m 50s and 2m of burn time. Please note that the AJ10-37 configuration is one of the least reliable engines in the game, and will fail early and often if you're using Test Flight or TestLite. Upgrade this engine to the next configuration as soon as you unlock the 1958 Orbital Rocketry node.

The engine will need to be covered for proper aerodynamics, so select an interstage fairing base. Place it so that the top "floating" node is the one that connects to the bottom of the engine bell. Using the PAW, reduce the height and increase the extra height until the bottom of the engine is near the interstage, and the ghostly blue lines are approximately reaching the bottom of the tank. Add a fairing in whatever symmetry the interstage is configured for, which is 4x by default. You may need to turn auto-shape off on the fairing base and tweak things manually to achieve the desired look and size. The upper stage is now complete.

Start the lower stage with a second procedural avionics unit, also using the TL-2 Near-Earth "Early Avionics" configuration. Increase the controllable mass to around 42 or 43 tons, and give it a few hundred EC so it won't run out of power during the launch.

Place two more integral fuel tanks beneath the avionics, both with 95 percent utilization, but with the standard (not high pressure) configuration this time. Make them 2.4m in diameter, with the top tank being a cone which tapers down to the 1.25m diameter of the upper stage. Increase the length of each tank to approximately 5.8m.

Select an LR-79 engine and place it on the bottom of the rocket stack. Use the PAW of each tank to fill them with the correct mix of kerosene and liquid oxygen. Note that this engine will have the starting S-3 configuration, which is less powerful and less reliable than subsequent configurations. As with the AJ10-37, upgrade the LR-79 as soon as you unlock the 1958 Orbital Rocketry node. The second configuration ("S-3D") is much more reliable and can be used for a couple of years before upgrading again.

Adjust your staging, and see what sort of delta V this rocket has. It should have close to 10 km/s on tap with this small payload. We could launch it now, but it wouldn't be ideal - the bottom of the rocket isn't very aerodynamic, and there's no provision for roll control on the first stage. Let's address these and finish the rocket.

Remove the engine, and place a 2.4m boattail fairing on the bottom of the rocket. Be sure to turn it over before attaching it, so the ghostly blue lines are heading down towards the ground. Attach fairings to the side, and adjust their size and shape using the PAW, similar to the interstage. You can keep the fairing straight, or you may be able to taper it a bit down to 2.3m or 2.2m, depending on the LR-79 engine model you're using.

Lastly, choose a small vernier engine for roll control (either the LR-101 or S-3D exhaust) and place two of them down near the LR-79. If you want a more Thor-alike appearance, select the LR-101 variant which is straight up and down (not angled), and tuck them up beneath the boat tail fairing. You may need to use the offset tool to place them exactly where you want. Finish by adding some launch clamps to provide stability, power, and fuel while the rocket is on the pad. You can add small fins if you wish for an appearance that's closer to a historical Thor, but they're not really needed. Here's the completed rocket.