Kerbal Space Program How-to Series: 7 – Satellites for Fun and Profit

(Current for KSP version 0.90)

To receive contracts for satellites in Career mode, you must unlock nodes containing a probe core (Flight Control) and a permanent source of power (solar panels from Electrics)

I recommend you research Advanced Flight Control for a probe with SAS capability.

Recommended mods:

First off, go to Mission Control, find a mission to launch a satellite and accept it.

Secondly, go to the Tracking Center. You should be able to see a colored orbit representing your goal. If your goal orbit isn’t around Kerbin, you’d need to change focus to that world by double clicking on it. Note also that there are marker orbs moving around that orbit as well; it is important to match that direction, or you won’t get credited for your satellite!

Now, you have to build your launcher. Ready for it?

ksp-kerbin-satellite

Well… doesn’t look like much, does it? Trust me though, this is more than enough to get to pretty much any orbit around Kerbin, Mun, or Minmus. This is because the unmanned module is much lighter than the crew pod and scientific equipment we’ve been dragging about before. We also do not have to worry about the return trip.

Anyway, here’s how to build it:

Probodobodyne OKTO serves as the command module. There is an FL-T200 Fuel Tank under it, supplying a Rockomax 48-7S.

All contract satellites need an antenna, so we’ll stick a Communotron 16 onto the tank. They also need a permanent power supply, so six OX-STAT Photovoltaic Panels are placed around the fuel tank. Just like on the Apallo, there are three on top, three on the bottom, and they are angled and staggered to catch light from any direction. There are also three Z-100 Rechargeable Battery Packs to last through any nights or eclipses.

The 48-7S shares stage 0 with a TR-18A Stack Decoupler. (If you have Precision Engineering, this may be substituted with the TR-2V Stack Decoupler, which is cheaper, lighter, and looks better here.)

Below the decoupler is a Small Inline Reaction Wheel; the OKTO’s reaction wheels are weak, and while sufficient for the upper stage, won’t be enough to keep the launch vessel steady. Below it is an RT-10 Solid Fuel Booster. It is thrust-limited to about 31%.

You may download the vessel here.

Oh, and one more important thing. Look at the description of your contract one more time (you can do so from within the VAB by clicking on the clipboard icon near the lower right). Some satellite contracts require you to stick a particular piece of science equipment onto it. 

Most of these equipment (e.g. the thermometer) are small and physically negligible, and thus can be stuck anywhere on the upper stage; however, the Mystery Goo Containment Unit isn’t, and has to be placed carefully on top to keep balance. Remember to keep the Center of Mass and Center of Thrust as aligned as possible. You can make small adjustments using the Offset tool, while Angle Snap is turned off.

Additionally, due to the added mass of the Mystery Goo, you may wish to add another TR-18A decoupler and RT-10 booster to the bottom, increasing the number of stages to three. The bottom booster should be thrust-limited to about 54%.

Or you can download a version of this vessel with the Mystery Goo already balanced on it here.

You might also be asked for a “materials bay”, which refers to the Science Jr. You’d probably also want the extra booster for that version too.

Name and save your vessel. I like saving these under generic names at first so that they can be reused, then renaming them to remind myself of where they’re headed just before launch (e.g. Rockomax Mun Satellite).

Your next step will depend on which world your target orbit is around:

For Kerbin orbits (launching into inclination): Unless the target inclination is pretty low (<5° or so, depending on your skills), you’d probably want to launch into your target orbit’s inclination. It’d take slightly more fuel to get into orbit, but much less than is required to adjust it, and it’ll make the adjustment phase more intuitive.

To do this, you’d want a flag planted at the KSC. (Alternatively, you can place a pod on the pad as a substitute.) Then go to the Tracking Center. Select your flag and click “fly” to “control” it, then go to the map view. Double-click on Kerbin to focus on it. Adjust your view so that the AN/DN flags point to each other. Your target orbit should look like a straight line, and cross right through the center of Kerbin. (You can use the Mun’s orbit, or the orbit of any previously launched equatorial satellites, as a guide too; they should also be straight lines.). You want to wait/time-warp until KSC goes right under the target orbit. Be sure you’re looking at the correct hemisphere; KSC is on the east coast of an Africa-like continent.

(If you have VOID, instead of doing that by eye, you can open the Orbit Information box, and turn on Extended Info. You want the local sidereal longitude of your flag/pod to either match the longitude of ascending node specified in your contract, or be 180º out of phase. If the given LAN is negative, add 360º to it.)

Then, rotate your view a little, and pay attention to the direction that the marker orbs on your target orbit go when it passes over KSC. It could be northward, southward, eastward, westward, or anywhere in between.This is the direction in which you want to launch; instead of turning straight east as usual, turn in that direction. Do note that north and south are reversed in the sky half of the navball. You can make this a little easier by first rolling your craft with Q (counterclockwise) or E (clockwise) so that you only need to turn your craft on one axis (left/right/up/down).

Once you’re in orbit, go to your map view and view your handiwork; it’d likely be a little bit off, but that’s fine. Check your contract via the clipboard icon on your toolbar; ensure that your current vessel has all the parts required by the contract.

For Mun/Minmus orbits: Follow the previous chapters to get an encounter with Mun or Minmus. (Note that with Minmus, you can try launching to its inclination with the instructions above. Minmus has a longitude of ascending node of 78° and inclination of 6°.) Then, with view focused on the target world, create a mid-course correction maneuver. Adjust your ksp-normalnormal/ksp-antinormalantinormal and ksp-radialradial/ksp-antiradialantiradial axes to make sure that you’re entering at the correct side of the world (the escape symbol denotes the exit). Double check the little orbs around the target orbit. Circularize into a stable orbit around that world.

Now that you’re in orbit around the correct world, it is time to transfer from your orbit to the target orbit.

Orbits are basically determined by two things; you need to be in the correct position, and you need to have the correct velocity (speed and direction). To change any orbit into any other orbit, you perform at least two burns; one to get into position, and one to change to the right velocity and therefore orbit. So your first maneuver node should get you into a position somewhere on the target orbit. It’s easiest to do so by matching one of your vessel’s apsides (Ap/Pe) to one of the target orbit’s nodes (AN/DN). Remember, create a maneuver node at the opposite side, then pull ksp-progradeprograde/ksp-retrograderetrograde to raise/lower your orbit.

Keep in mind that space is three-dimensional, so things that appear close on the screen may not actually be that close (one point could be quite some distance “behind” the other). To get a better view of how close you are, create a second, “dummy” maneuver node near the intercept. Then Backspace to focus your view on your vessel, and then Tab until you are focused on the dummy maneuver node. You can then rotate your view around to see how close you are. You’d likely want to adjust both the size and position of the first maneuver to get as close an intercept as possible (Precise Node to the rescue once again, to avoid tedious view-switching while adjusting). The apsis and node should be pointing at the same spot no matter how you rotate.

More experienced players can try using two burns (one to lengthen the orbit and one mid-course plane change) to intercept on any point on the target orbit; for highly elliptical target orbits, intercepting near the target orbit’s apoapsis could save fuel during the next phase. With no flags to indicate your intercept point, this is slightly trickier; what you can do is to create the dummy node as usual, then move it around to mark the position of your intercept. Ensure it intersects the target orbit no matter how you rotate.

Perform your burn; you should be as precise as possible. Then delete the maneuver node.

Return focus to the “dummy” maneuver node. Your apsis might not be exactly on the target orbit; you’d want to move your maneuver node around so that it is as close to the target orbit as possible (ensure it intersects no matter how you rotate).

Now to get into the right velocity. Essentially, you need to manipulate all three axes, and match the target orbit as closely as possible. To do this, it helps to know what each axis does:

ksp-progradePrograde is “forward” relative to your current velocity, and raises your orbit on the opposite side. ksp-retrograde Retrograde is “backward”, and lowers your orbit on the opposite side. Pull retrograde even more, and you can “reverse” your orbit; this is obviously very fuel-expensive. Raising and circularizing orbits with this axis are generally more efficient the closer you are to the parent world / the faster you are going, due to the Oberth effect.

ksp-normalNormal is “leftward”, and ksp-antinormalantinormal is “rightward”. They will adjust your orbital plane counterclockwise and clockwise, respectively. These are generally more efficient the further you are from the parent world; the slower you are going, the easier it is to change your direction.

ksp-radialRadial is “outward”, and ksp-antiradialantiradial is “inward”. These are somewhat unusual; radial will raise your orbit in front of you, and lower your orbit behind you. Antiradial does the opposite. The effect is similar to rotating a hula hoop around a stick. It changes your direction, so it is more efficient the further you are from the parent world; however, it is inefficient compared to a combination of prograde/retrograde burns, and as such is best used for small-ish adjustments.

To ensure your orbital planes are aligned, you’d want to rotate your view such that your intercept point goes directly through the center of your parent world. Both your current orbit and your target orbit should look like straight lines in this view. You can also adjust your other two axes in this view; ksp-progradeprograde/ksp-retrograderetrograde will change the “length” of your orbit, while ksp-radialradial/ksp-antiradialantiradial will “shift” it left or right. In fact, I encourage you to do so, as changing these axes may throw your orbital plane off again.

When the “lines” are as similar as possible, rotate around to check your work. You might want to make some final few adjustments, to get the Ap and Pe flags as close as possible. Hovering over them will tell you their heights; a good rule of thumb is to get the first three digits to match, or be as close as possible.

(Note that if your target orbit is circular or nearly so, it may be extremely difficult to get the Ap and Pe flags to be in the right position. Fortunately in that case, you don’t have to; you just have to make sure they’re the correct height)

Your orbit should very nearly be pixel-perfect at this point. Do one last check on your projected orbit to make sure you’ll be going the right direction (compare your apoapsis and periapsis times). Then all that’s left is to perform the maneuver. Again, get this as precise as possible.

When you are done, view your contracts by clicking the clipboard icon in the toolbar, and scroll to the relevant one. Ensure that “Reach the designated orbit within deviation” is checked. Now all that is left to do is to wait for a while, and that should fulfill the “maintain stability for 10 seconds” requirement, and complete your contract!

Additional tips:

  • If the thrust of your vessel is so powerful that you have trouble finishing your maneuvers precisely (easily happens with these lightweight satellites), you may rightclick on your engine and turn the Thrust Limiter downward in-flight.
  • Stationary orbits (known as such because they are “stationary” relative to the surface) may sometimes require you to overlook a particular point on the surface. For Kerbin, you simply have to place your transfer (first) node approximately a quarter-turn before the point. For other bodies, it can be more complicated; you may want to use the Trajectories mod, turn on “body-fixed” mode, and make sure your apsis is at the correct spot. In any case you have a lot of room for error, since you can overlook almost half of the world from any particular point, so worst case scenario, just wait in your elliptical orbit until your intercept goes over the correct spot.
  • If you just put something into a synchronous or tundra orbit (a tundra orbit is just a synchronous orbit with a specific, high inclination and eccentricity), using the Trajectories mod with body-fixed mode should reveal a closed loop (resembling a figure-eight or a twisted ellipse) called an analemma. An observer on the surface would see the satellite traverse this track every day. Stationary and synchronous orbits have orbital periods matching that of the world’s rotational period.
  • When you have a lot of satellites in orbit, it is easy for them to get in the way of your map view in future missions. If you hover over the top of your screen, you can show/hide vessels by category, and hide all probes this way. This can cause a problem if your own ship is a probe as well as you won’t be able to see its icon; to remedy this, temporarily change your vessel to a different vessel type by rightclicking on the probe core, and clicking Rename Vessel. You can change the type of vessel your ship is classified as this way. You can also rename vessels/change icons at the Tracking Center by clicking on its name in the info box.

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