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

Revision as of 04:58, 2 May 2015

Getting into orbit over Kerbin is rather simple, but it will require some knowledge and preparation. Space begins at 70,000m above the planet Kerbin. Stay above that for an entire flight around the planet and you're in orbit.

The process to get into orbit follows a simple progression:

1. Launch straight up to 10 km
2. Change your Pitch to 45° east and keep the engines on until your projected Apoapsis is above 70 km
3. Change your pitch to horizontal just before you reach the Apoapsis
4. Burn at Apoapsis until your Periapsis is above 70 km

Specifications

• Length: 15–20 minutes
• Difficulty: Harder than a suborbital flight, easier than an orbital intercept.
• Skills needed: Seat of the pants
• For version: Every version (tested on 0.23)

Steps

Step 0 - Rocket Design

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

A liquid fueled rocket with at least two stages preferably. Anything less will either only get you suborbital or an unwieldy expensive super large fuel tank that's only good for being an orbiting billboard (unless you are bringing heavy payloads to orbit of course)

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is:

• Unmanned: Probodobodyne OKTO2 or Manned: Command Pod Mk1 with Mk16 Parachute and TR-18A Stack Decoupler
• FL-T400 Fuel Tank
• LV-909 Liquid Fuel Engine
• TR-18A Stack Decoupler
• FL-T800 Fuel Tank
• LV-T30 Liquid Fuel Engine

For fun, use the LVT-30 engine for your first stage as it doesn't have thrust vectoring and thus will challenge you to actually fly the craft into orbit using your WASD keys keeping your navball on target. Your control module by default provides enough SAS control by itself to prevent you from going out of control for this mission.

Make sure your staging sequence is the way you want it, else you can add your flight to the countless list of catastrophic mission failures.

Step 1 - Launch Prep

Prepare your launch.

1. Set your map view with the M key to see your rocket at the launch site from space, tilted so you are looking north. You want to be able to see your apoapsis marker during your gravity turn so you can gauge when to cut your engines and coast up to it prior to burning your orbiting maneuver.

2. Set your thrust to maximum by holding Shift.

3. Toggle on SAS by hitting T.

Step 2 - The Launch

Say your countdown if you wish, and hit spacebar to launch into...well, space...without the bar (you'll make a space station with a bar at this end of the galaxy later).

Step 3 - Get up to 10,000 meters

Keep your rocket pointed straight up (use your navball to keep your dot on the top dot on the blue part of the navball) until you hit around 9,900 meters. Your first engine should cut out before this, just jettison it with the spacebar and burn your final engine. Throttle your second engine down to 2/3rds power since the atmosphere is weaker here and won't slow you down as much, and you will save precious fuel.

Step 4 - Gravity Turn 45 degrees East until 70km Apoapsis

Now for the fun part. Assuming you are pointing straight up, press the D key several times to angle your ship over toward the east. Watch the navball as it rotates under the gold V-shaped marker along the 90 degree east line. Continue pressing D to angle the rocket over toward the ground until you reach the 45-degree east mark (halfway down the blue part of the navball). Press the T key to enable SAS to help you keep it there, but don't rely on it. You will need to make course corrections until your apoapsis gets past 70 km altitude and enter space. At this point you should be going into space at a 45-degree angle from the ground, and in an easterly direction. Doing so will gain you speed and not waste the fuel you will need to get into orbit. If you want to aim for a more fuel-efficient ascent, you can try pitching down to 30 degrees when your apoapsis reaches 40 km.

As of Version 1.0, atmospheric drag has been increased, so it may be difficult and not worth the fuel to begin your turn until above 18-20 km.

Step 5 - Get Your Apoapsis above 70km

While climbing up to 70 km or 70,000 meters, it's now time to switch to your map view and control your ship from there entirely. Hopefully your navball is toggled on, else click on the collapsed tab at the bottom of the map view.

You will need to keep burning your fuel until you see your apoapsis marker reach 70 km. You can see how high it is by hovering your mouse over it. Once it hits 70 km (I usually shoot for 75 km to buy me some head room) your craft will be able to coast up to it without any further fuel. Feel free to cut your engines with the X key and save some fuel for your orbital burn.

Step 6 - Orient for On-Orbit Burn

As you approach apoapsis (preferably 30 seconds prior), orient your ship to the 0-degree latitude mark (the thin dividing line between the blue and brown halves on the navball), heading east. Again, you should be in your map view when you start your burn. Press the Tab key to center your view on Kerbin and zoom out so you can see your orbit as it forms.

Step 7 - Burn into Orbit

Once you are 10–30 seconds away from your apoapsis, begin your on-orbit burn using the Shift key to throttle up. You can use full or partial throttle; your choice. Full throttle takes less time but runs a small risk of overshooting your apoapsis and wasting precious return fuel. If you aren't concerned, go full throttle, baby, at any point near apoapsis and claim a stake with the stars. You only need to burn your fuel long enough to see the periapsis marker appear on the other side of the orbit from the apoapsis. When your orbit grows to a full circle and the apopapsis and periapsis markers start to switch positions, cut your engine with the X key. Congrats, you made it into orbit. It's usually a good idea to keep burning your fuel until your new periapsis marker is above 70 km. If it's below that altitude, your orbit will cause your craft to fall into the atmosphere and aerobrake, eventually returning to Kerbin. If your periapsis is above 70 km, congrats, you will orbit Kerbin forever. If you have a manned flight and fuel is low, keep your periapsis below 70 km to ensure a safe return to Kerbin.

Finishing word

After orbiting for a while, and depending upon your remaining fuel (with this design, you won't have much, if any) you can choose to return to Kerbin. Orient your craft for a de-orbit burn by aligning the gold V-shaped indicator on the navball over the green retrograde marker and burn backwards (retrograde) to the direction of your travel to slow down enough that periapsis falls well below 70 km. For maximum efficiency, wait until you are at your apoapsis point, lest you be stuck in space with a manned crew forever.