Difference between revisions of "Tutorial: How to Get into Orbit"

Revision as of 02:33, 27 February 2019

Proceed with caution:

• The instructions listed almost invariably fail for larger Rockets, since it assumes a very small Rocket with good maneuvering.

This tutorial describes a simple launch profile to get a vehicle to Orbit over Kerbin, and back again.

Specifications

• Length: 15–20 minutes
• Difficulty: Harder than a suborbital flight, easier than an orbital intercept.
• Skills needed: Seat of the pants
• For version: 1.0.2

Rocket Design

Rocket assembled and ready to launch. TT18-A Launch Stability Enhancers optional. 0.25

The rocket should preferably be liquid fueled with at least two stages. An example of a simple manned orbiter:

• Command Pod Mk1
• Mk16 Parachute
• Heat_Shield_(1.25m)
• TD-12 Decoupler
• FL-T400 Fuel Tank
• LV-909 Liquid Fuel Engine
• Another TD-12 Decoupler
• FL-T800 Fuel Tank
• LV-T30 Liquid Fuel Engine

In order to make sure the staging sequence is correct, see our guide on Rocket Staging.

Steps to Orbit and Back

Launch Preparation

1. Set thrust to maximum by hitting Z.
2. Toggle on SAS by hitting T.
3. Hit M to go to Map View. Tilt the view so that you're looking straight down Kerbin's North pole, which will give a clear view of the trajectory arc towards the East and the Apoapsis label.
4. Switch back to the normal viewmode by hitting M to enjoy the Launch spectacle.

Accelerate to 100 m/s

Launch by hitting the space bar and keep the rocket pointed straight up until the vehicle's speed is 100 m/s. Use the Navball to keep the level indicator centered on the blue hemisphere.

Pitch 10 degrees East

When the rocket's speed reaches 100 m/s, start a gravity turn by pressing the D key until the rocket is pitched 10 degrees towards the East. The heading ("HDG") on the Navball should now be 90 degrees.

While the rocket accelerates, gravity will bend the trajectory downwards. On the Navball this can be observed as the Prograde marker dropping further down. Follow it by keeping the level indicator within the circle of the prograde marker at all times especially while in the lower atmosphere, but at about 30km the reaction wheels should be able to compensate. If craft nears the apoapsis too fast, which can be seen in a dropping time to apoapsis, it might be necessary to point “above” the prograde marker, away from the brown half.

Stage

The fuel of the first stage will run out before 20km altitude. Hit the space bar to discard it and to activate the second stage. Continue to accelerate at full throttle.

Hit M to switch to map view. Click the Navball toggle at the bottom of the screen to make it visible again. Continue to watch the Navball and steer the rocket to keep it aligned it with prograde.

Get apoapsis above 70 km

In map view, hover the mouse over the "AP" label on the highest point of the trajectory to monitor the apoapsis height; cut off the engine with X when it reaches 70 km (70,000 meters).

Let the rocket coast towards apoapsis after cutting off the engine.

Get periapsis above 70 km

As the rocket approaches apoapsis, orient it once more to align with the prograde marker. At 30 seconds before apoapsis, reignite the engine at full throttle with Z. The apoapsis will begin to shift ahead; aim to keep it roughly the same amount of time ahead by throttling up or down with Shift and Control.

The projected trajectory will begin to widen until the PE label appears on the other side of the planet. A stable orbit will be reached when both apoapsis and periapsis are above 70 km.

De-orbiting

Wait until the craft is at apoapsis and orient it for a de-orbit burn by aligning the level indicator on the navball with the chartreuse yellow retrograde marker. Now burn until the periapsis is around 30 km. Discard the engine and fuel tank by staging, leaving only the command pod with its heat shield and parachute.

If fuel is scarce, any periapsis below 70 km will eventually result in de-orbiting. However, it may take many passes through the atmosphere before the vehicle finally slows down enough.

Re-entry

During re-entry into the atmosphere, the capsule will heat up and lose speed. Keep the level indicator aligned with the retrograde marker to let the heat shield take the brunt of the heat.

Wait until the capsule's speed drops below 200 m/s, or the parachute sign on the left turns from red to grey, and deploy the parachute.

Common problems and solutions

Rocket tumbles or goes out of control

The most common problem of new players is their rockets going out of control while in the atmosphere. There are multiple causes and slightly different solutions. First, make sure that SAS is on.

If that doesn't work, then the cause is often a lack of control surfaces and aerodynamics. You will want to place something like the AV-R8 Winglet at the bottom of your rocket. This gives it both stability and control. Using an engine that has a gimbal, such as the LV-T45 will also give you more control.

Another common cause is aggressive piloting. When pitching over or making other corrections, it is important to make small adjustments. Always keep your nose close to the green prograde marker. In other words, make a small adjustment, wait until you're moving in the same direction as your nose is pointing, and then make another small adjustment.

The final common cause is travelling too quickly while in the lower atmosphere. This causes more aerodynamic pressure on your craft, which may overwhelm the control provided by winglets and engines. If you see flames during ascent, this is a likely cause. The best way to solve this is not to lower your throttle, but instead to add more fuel. The extra fuel also gives you more room to recover from mistakes.