Your first orbit will almost certainly not be circular – if you burn for marginally too short a time then the periapsis will be lower than your apoapsis, and vice versa. Once you’ve done that, congratulations! You’ve achieved orbit. Keep going with this until you can see on the other side of the planet your periapsis, the lowest point in the orbit, is also above 70km. The opposite works too, so if it goes too far ahead of you in the trajectory then lower your heading to a little below the horizon to correct. If during the burn the apoapsis slips behind you then raise your heading to a little above the horizon to bring it back. As such, your goal is to keep your craft as close as possible to the apoapsis (which is the most efficient point for the manoeuvre) throughout, which is fortunately quite simple to do. If you keep burning your engines while pointed right at the horizon, however, the apoapsis will likely pass you by which will make achieving orbit more difficult. Now at that point with the apoapsis approaching throttle up once more with your heading towards the horizon, as in in the picture above (it is generally easier to do this in map view). Once you have an apoapsis you’re happy with cut your engine (either throttle down with ctrl or press x), then wait until the apoapsis is about 30 seconds away, remembering that the keys control time warp to make the wait a little shorter. You will have to exit map view to jettison stages however, which is worth remembering. If the first liquid stage runs out of fuel jettison it and keep going with the final engine. Kerbin’s atmosphere ends at 70km which means that anything above that altitude an orbit can be considered stable so keep burning your engines at that 45 degree angle until your apoapsis is above 70km (you may want to go a little higher to about 80km to give some extra breathing room). At this stage what you need to be keeping an eye on is your apoapsis – the highest point in the orbit you can see this by mousing over the little ‘Ap’ icon on the map.
#Kerbal space program prograde mods#
Ideally it should be your prograde vector rather than the heading of the vehicle itself which is at 45 degrees – gravity will be pulling this lower than the actual heading of your craft so it’s that marker you need to be more concerned with.įrom now on map view (default key to enter and exit this is ‘m’) is going to be very much your friend, as without mods it is the only way to get some vital data you will need to achieve a good orbit. Your SRBs will carry you around the first 10km using my design from last time, at which point you should turn about 45 degrees so that you are heading east, jettisoning the spent SRBs and activating the first liquid engine. To blast off the launch pad the first step is to throttle up (in case you’ve forgotten, the default keys are shift to throttle up, ctrl to throttle down and x to cut engines), activate SAS to hold your vertical heading and hit the staging button to launch. Launching in that way the rotational speed of the planet is effectively acting as a head start on the speed we need to achieve to reach orbit. Instead, we need to head off at an angle after gaining a little altitude, with eastward (in the same anticlockwise direction as the planetary rotation) being the preferred heading. This need for horizontal motion is a crucial consideration – you can’t just head straight up and expect to achieve much. The first question to logically ask before trying to reach orbit is ‘what is an orbit?’ Simply put, an orbit is when you are travelling in a direction parallel to the ground at sufficient speed that when you fall back down, you miss the planet.
#Kerbal space program prograde how to#
Today’s second part of the guide describes how to tackle the first major hurdle of any budding space program – reaching orbit.Īfter reading the last guide on how to build a successful rocket and some basic flight instructions you should be ready to try the next step in space, orbit, which is the fundamental requirement of almost every mission you could choose to undertake in KSP.
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