Kerbal Space Program How-to Series: 6 – One Tiny Step (Minmus Landing)

(Current for KSP version 0.25)

In this chapter we will look at a rocket that is capable of landing on Minmus, doing some science, and returning to Kerbin safely. Why Minmus? It may be slightly harder to get to, but it is more science-rich (and we’ve also already gotten science from the space around the Mun), and it is much easier to land and take off from, due to its weaker gravity and flat “seas”.

Recommended mods:

You will also learn to:

  • Set and use action groups
  • Use fuel lines to connect fuel tanks

If you’re in Career mode, you should go to Mission Control and accept the “Explore Minmus” contract. Also accept any Minmus science data contracts, as well as “Plant a flag on Minmus”, if you have them. I also recommend you install the Fine Print mod. It makes contracts much more diverse, and the next chapters will cover how to complete some of them. Additionally, its contracts will be incorporated into the next version of KSP, so I suggest you get used to them now.

If you haven’t already, research Flight Control; this should complete column 4 of the tech tree. Then in column 5, research Fuel SystemsElectrics, and Space Exploration. Space Exploration unlocks a new science part, the 2HOT Thermometer; so you can use it on the launchpad and runway for some extra science points.

Here comes the rocket (download):

ksp-minmus-lander

As usual, you start with a Command Pod Mk1, a Mk16 Parachute on top of it, and a TR-18A Stack Decoupler on the bottom of it, sharing stage 0.

You may notice there are things stuck to the pod. Specifically there are three OX-STAT Photovoltaic Panels; these are placed symmetrically. Before placing, press Shift-S a few times to angle them upward. Then place one facing the north (toward the side with the flag; the door faces east), so that the other two flank your hatch (that faces south by default). This is a long mission, and thus you want solar panels to provide electricity to power your pod’s reaction wheels and rotate your vessel.

There are also seven 2HOT Thermometers on the pod. It doesn’t matter where they are placed on the pod as long as they don’t block the hatch; they are light enough that KSP considers them physically negligible.

ksp-minmus-lander-pod-closeup
Closeup of the pod.

During your flight, trying to right click each of those thermometers to perform scientific experiments would be quite a pain. It is thus easiest to assign them to action groups. Click on the blue hammer-and-spanner icon at the top of the screen. Click Custom01, then one of your thermometers. Add “Log Temperature” to your group actions. Now assign each of the others to Custom02 to Custom07 the same way.

Below the decoupler is an FL-T100, an FL-T200 and an FL-T400 Fuel Tank, supplying an LV-909 Liquid Fuel Engine. There are three SC-9001 Science Jr.s around it. One of them points toward the north. Three LT-1 Landing Struts are placed on the outside edge of the Science Jrs. These should be placed low enough that the LV-909 would be protected when they are extended. Last but not least, there are three more OX-STAT Photovoltaic Panels, stuck over the edge of the LV-909. These should be angled downward (Shift-W a few times), with one of them facing southward. This arrangement ensures that at least one panel will be facing toward the sun no matter where our vessel is pointing (unless the sun is blocked altogether by a planet or moon, but the pod stores enough electricity for that) Place a TR-18A Stack Decoupler under the LV-909. That’s stage 1.

ksp-minmus-lander-stage1-bottom-closeup
Closeup of the bottom of Stage 1

Below it is a somewhat unusual arrangement. There is an FL-T400 Fuel Tank, stacked on a Small Inline Reaction Wheel, stacked on an FL-T800 Fuel Tank; Two more FL-T800s are placed symmetrically on the north and south sides. The reaction wheel is there because this vessel is somewhat heavy and tall, which makes it very difficult for the command pod’s reaction wheels to keep it steady or turn it. To visualize this, swing a pencil using two fingers about its end, and about its middle; which is easier? Thus, the reaction wheel is placed nearer to the center of mass to help it out. We won’t need it for the upper stage, so it would be dumped along with this stage.

Two LV-T30 Liquid Fuel Engines are placed below the side fuel tanks. Fuel will not automatically flow from the middle tanks to the radially attached (side) tanks however, so you need to connect them with FTX-2 External Fuel Ducts. These work similar to struts. Ensure that 2x symmetry is on, then click on the middle tank first, then the side tank. Place a TR-18A Stack Decoupler beneath the middle tank. That’s stage 2.

ksp-minmus-lander-stage2-closeup
Closeup of stage 2.

Place a Rockomax BACC Solid Fuel Booster below the decoupler, then place two more symmetrically, again in a north-south orientation. Set the Thrust Limiter of all of them to 85%, then put them in stage 3. The total cost should be 27,507 funds.

Give the staging a once-over, name the vessel (my name is ‘Minmus Lander “Apallo”’) and save it, and then you’re ready for launch. As usual, wait a few seconds, T for SAS, Z for full throttle, then Spacebar for launch. As usual, launch eastward into a low orbit (~80,000m).

While launching, don’t forget you can use your thermometers. Hit 1 as soon as you launch to use your first thermometer, then click Keep Data. 2nd should be used in the upper atmosphere (>18,000m), 3rd should be used once you’re in low orbit.

Once you’re in orbit, you can extend your gears by pressing G (you probably will have to tap it twice to actually extend them). Locate Minmus (it orbits Kerbin further away than the Mun), then right click on it and Set as Target. Right away you should notice that Minmus has a slight inclination (6 degrees, though since your orbit might not be perfectly equatorial, you may see more or less). You thus have to correct your inclination to give yourself the best chance of intercepting it. As you might have learned from the orbital rescue chapter, you do this by creating a maneuver node at either the ascending node (AN) or descending node (DN), then adjusting the ksp-normalnormal / ksp-antinormalantinormal axis. 

(Optional) Note that your projected orbit might have lengthened slightly; that’s because your maneuver node’s axis is always in reference to your current rather than your projected orbit, so your maneuver gains a slight “prograde” pull in reference to the new plane. If you don’t want this to happen, you must pull the ksp-retrograderetrograde axis some. Note that this will change your plane yet again, so a balancing act must be done. It’s up to you whether you want to do this; keeping a near-circular orbit will make the next task a bit easier.

Once you have matched planes, find an encounter with Minmus, similar to the way you did with the Mun; create a node on the opposite side, pull ksp-progradeprograde till your projected orbit raises slightly above Minmus’s orbital height, then move the maneuver node around until you get an encounter. (If your orbit has lengthened due to your plane change, you now may have to constantly adjust your maneuver to keep your transfer orbit at the correct height.)

(More experienced players can try using two maneuver nodes; one to lengthen the orbit, and a second mid-course correction to plane-change to get an intercept. Plane changes are more efficient the further you are, so this could save some fuel. Or even better; you can try launching right into Minmus’s inclination. Launching into an inclination will be covered in the next chapter about satellites.)

Try to enter on the right side once again, and aim for a Minmus periapsis of about 12,000~25,000m. This can be somewhat difficult, and you might see your orbit jitter quite a bit, since Minmus is so far away it makes accurately targeting it difficult. That’s fine though; you can always correct it mid-course and within Minmus’s SOI.

Thermometers don’t provide any science in deep space. However, once you enter Minmus’s SOI, you can still do a crew report, EVA report (and Take Data to free the crew report space), and open one of the Science Jr / Mystery Goo combos. Do it once again once you’re in low orbit around Minmus, and this time you can use your 4th thermometer.

Now is a good time to quicksave with F5 (alternatively, using Alt-F5 will allow you to quicksave to a specific filename. Alt-F9 quickloads from a chosen file.)

You now want to look around Minmus in the Map View, and pick a landing site. I suggest one of those flat “seas”, on the day side. Create a maneuver node, and pull ksp-retrograderetrograde so that it touches the ground somewhat past your intended landing site. The most efficient place to put your node is on the opposite side of Minmus, but you may have to put it a bit closer to avoid clipping any mountains on the way down.

If you have the Trajectories mod, turn it on with the special button in your toolbar. Turn on “show trajectory” and “body-fixed mode”. This will display your path relative to the surface, thus allowing you to account for Minmus’s rotation. Make sure it doesn’t clip into any mountains, and that the intersect point / “red X” is slightly past your intended landing site.

Once you’re satisfied, perform the maneuver. Delete the node, and check your trajectory once again. If you haven’t extended your lander legs, you should do so now. (Press G; you might have to do it twice)

Now you are on a collision course. Since Minmus has no atmosphere, parachutes are useless; you’ll have to use your engines to slow your landing to a safe speed.

To help do this, create another maneuver node close to the surface. Pull ksp-retrograderetrograde until your trajectory on that point is a straight line downward. If you have Trajectories, you should be able to very accurately pinpoint your landing site. Point to your ksp-maneuver maneuver node in preparation.

(Time warp tip: If it doesn’t let you warp past 1x, you can still use “physical time warp”, the four-arrow kind that you get within Kerbin’s atmosphere. Use Alt+. and Alt+, to increase and decrease physical warp. You will be limited to 4x speed. Do note that high physical warp may sometimes destabilize large vessels.)

As you get close to the maneuver, switch your navball to Surface mode. Now ignore the maneuver node and point to the ksp-retrograde retrograde icon instead; the maneuver node was just to estimate your time to arrival and burn time. Start burning when you get close to your intended landing site. (VOID users: the most accurate time to start burning is still at “1/2 done at node”; you may want to burn a fraction of a second earlier for safety purposes)

When you’re almost at zero the retrograde marker will start to move toward the zenith; press X to kill your engine. As Minmus’s gravity pulls you downward, your vector will turn nearly vertical. You can delete your maneuver node at this point.

The “seas” are very nice and flat, and are only a few meters above “sea level”, so you can use the altimeter to gauge your height.

As you fall, you want to kill off the last of your horizontal velocity; burning offset to the ksp-retrograderetrograde icon will “herd” it away from your level indicator. Easy on the throttle (Shift, not Z); it’s easy to overthrust against Minmus’s low gravity. Get the retrograde icon as close to the zenith as possible. Then point your level indicator to it/the zenith.

If you’ve ever played the old “Lunar Lander” game you’d know that being too cautious / thrust-happy would waste fuel, as gravity has more time to act on your lander. Of course, fail to thrust enough, and you’ll crash. A good rule of thumb is to not exceed 50 m/s at 500 meters, 25 m/s at 250 meters, and 10 m/s at 100 meters; you get the idea. Again, easy on the throttle.

Try to land at less than 9 m/s. Once you touch down, kill your engines with X, and turn SAS off with T. (Leaving SAS on when you’re on the ground may cause it to stay in a leaned position and waste electricity.)

Take a moment to congratulate yourself; you’ve landed! Do a crew report. Open your third and final set of Science Jr and Mystery Goo containers, and use your 5th thermometer.

Do an EVA. Take Data from the pod, then press Spacebar to let go and drop down to the ground. Go for a little moonwalk. Shift+W/A/S/D will have him run. Space will have him jump; look at how high he goes! Minmus has only about 1/20 of Kerbin/Earth’s gravity on the surface.

Don’t forget to take an EVA report and a Surface Sample. Also, plant a flag to commemorate your victory (and complete the contract if you have it). You may want to put the current biome into the title of your flag, to give yourself a reminder that you have visited it.

Now take all the data from the Science Jrs and the Mystery Goo containers. Pressing R will turn on your EVA pack allowing you to maneuver while off the ground. Minmus’s gravity is also weak enough that you can thrust upward with it using Shift. This is also why we didn’t bring a ladder here; it shouldn’t be too difficult to maneuver back to the pod and reenter it.

Press F5 to quicksave again. T to turn on SAS again, then thrust up with Shift to launch. (Full-throttle Z would likely make your craft difficult to control here). You can do your gravity turn almost immediately since there is no atmosphere; just be careful of any mountains around. Once again, turn east (90 degrees heading); but note that your vessel might not be oriented the same way it was on the launchpad, so pay attention to your navball. You only need an apoapsis of about 8,000~10,000m (if you’re not using VOID, you probably should watch the map view almost immediately after launching); then use a maneuver node to circularize it.

Plan a direct return trajectory, similar to what you did with the Mun. You will need to create your maneuver node somewhat further forward than you did on the Mun (10-o’-clock if Minmus’s orbital direction is 12-o’-clock), since you’re further away. Again, pull your ksp-progradeprograde axis until your Kerbin periapsis is about 30,000m.

If you accidentally encounter the Mun, you can avoid it by adjusting your ksp-normalnormal / ksp-antinormalantinormal axis. If you have Trajectories, you can actually see your projected landing spot on Kerbin if you increase “number of conics” high enough.

Press F5 to quicksave again, then perform the maneuver. Reenter and parachute-land as per usual; you can use the 6th thermometer “flying” above your landing site, and the 7th after you touch down. You can also do Crew Reports and EVA Reports, if you still managed to land on a new biome. Then recover your craft. This one mission alone should be worth about 900 science points. Congratulations for yet another successful mission!

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