However, nothing is ever easy! Even with just going to the Mun, we have a lot of prep work to do. First and foremost, we have no idea about the topography of the Mun, besides what we can see by staring at it from the surface of Kerbin. Already, from there we can see it's littered with craters and valleys, which end up posing a big problem, because all the planning in the world won't help us out if we nail the delta/V and get everything right and then realize that our landing spot is on the side of a crater and at a 45 degree angle. If we try to land there, odds are we'll just tip the craft and strand anyone in the capsule on the Mun. So, it's very important that first things first, we need to send an unmanned probe to the Mun to map it for us, so we can pick a nice landing spot and look for any interesting anomalies.
So, for this mission, the engineers have whipped together the KSS Long Shot, a four-stage rocket with a wonderful little probe tucked away under the fairings in the nose. You'll see it later, but for now, the probe is much safer and more aerodynamic in it's housing. The probe should our purposes well, it contains a little 20kN thrust motor with about 55 liters of fuel, meaning the probe itself has a TWR of 1.72 and enough fuel to burn at full throttle for about two minutes, which is awesome in case we get the probe into orbit around the Mun and then decide to change up it's orbit. It also carries several science instruments and enough batteries and solar panels to hopefully run forever. Most importantly, however, is that nearly a quarter of the probe's weight is donated to mapping equipment, capable of mapping an entire planet in just a few orbits.
Since I've already shown how to calculate the delta/V of a rocket, I downloaded the Kerbal Engineer Redux, a fantastic little mod that helps you build rockets. Slap a flight computer somewhere on your rocket, and it feeds you all the fantastic information you'll need, such as the delta/V of each individual stage, as well as the TWR of each stage. So, in designing the Long Shot, I've got two stages with big ass 2100kN and 1700kN motors with just enough fuel to equal out to almost 5,000m/s of delta/V, and since we already know that getting into orbit from the Kerbin surface takes 4,700m/s, we know that the Long Shot should have no problem getting into a good, stable orbit around Kerbin.
However, we need to plan for further than Kerbin orbit if we want to go to the Mun. We have acouple more steps. Once we're in orbit at 100km, we need to 1) perform half a Hohmann transfer orbit like we covered in mission one, which will blow out our apoapsis and get it into the Mun's path, 2) When the mun comes swinging around in it's orbit and crosses our apoapsis, hopefully we will be there and will be picked up by the Mun's gravity, where we can establish an orbit around the mun.
I'll save you the math this time around, because it's the same as in mission one. Using the same formulas, I just need to plan for a burn to raise my apoapsis to 12,000,000m, the Mun's altitude. Don't forget when plugging in altitudes to add 600,000m for the thickness of Kerbin's surface! After running the numbers, I find I need about 900m/s of delta/V to reach the Mun, and then about 200m/s more to establish my orbit, or 1100m/s all told to complete the mission. Add 1100 to 4700 and we find that we need roughly 5,800 m/s of delta/V to get this probe to the Mun.
Thankfully, the KSS Long Shot is equipped with an atomic motor, which uses the power of science to create a very fuel efficient motor . The atomic motors only produce 60kN of thrust, so they are rather weak, but they do it at an lsp of over 800. Since there is no air resistance in space, every little bit of thrust matters because once you speed up, there is nothing to slow you back down. So, this little 60kN stage with a decent amount of fuel nets me a whopping 4,900m/s of delta/V at a TWR of 0.71. That 0.71 is troubling, because as discussed earlier, a TWR of less than 1 means your rocket will not be able to lift itself. However, we already figured that the first two stages have almost 5,000m/s of delta/V, which means that by the time we're even thinking about using this weak third stage, we'll be well into orbit and while this little motor won't push us very fast, it'll push us where we need to go with no worry about falling back to earth since we're already in orbit.
Finally, the last stage, the itty bitty motor on the probe itself nets an additional 2,571m/s of thrust, bringing our total delta/V to nearly 12,500m/s for the entire rocket. We only need 5,800m/s of delta/V, but I decided to build one stock rocket capable of reaching almost anywhere so next time I need to map something I can just load up this rocket.
Blastoff! The KSS Long Shot is off to a great start, launching smooth and stable with nary a hint of wobble. Interesting to note in the background, the Kirby Space Center received a large grant and we've updated all our old, aging buildings and built much nicer facilities!
Still burning on the second stage, the Long Shot begins to tip over and add some horizontal speed to it's path so it can establish an orbit. Mun goers, I'll give you a hint. the orbital plane of the Mun falls nice and neatly onto the 90 degree line on your nav ball, or "west". Normally when visiting other planets, we'll have to do a little burn later to match the eccentricities (or how many degrees from you the orbit you want to match is twisted), but going to the Mun, if you can keep your icon over the 90 line, you're orbit will be nice and level with the Mun's.
Burning off the least dregs of fuel in it's second stage, the Long Shot slips into a tidy orbit around Kerbin at about 150km. So far, all is going well!
It's time to ditch the heavy, now empty second stage and let the atomic motor do it's thing! The second stage seperates with a puff, floating off into space. A quick test of the atomic motor shows all is working well and we're good to head to the Mun!
What we're about to do is a daunting task. The Mun, the circular grey orbit on the outside of the screen, is orbiting Kerbin counter-clockwise. We want to line ourselves up right and burn in the right place to blow our orbit out to be even with the Mun's and then be there in the exact right time so that we show up right as the Mun is passing by, and then the Mun's gravity will pick us up and pull us into orbit.
For that, we'll use the fantastic maneuver node. By clicking anywhere on your blue orbit, you can plot out what maneuvers will put you where. The three icons in the maneuver node are the same as the ones on your nav ball, yellow is orbit progressive and retro (speed up or slow down), which we're worried about. I know I want to put my apoapsis about 45 degrees ahead of the Mun, in order to give it some space to travel as I get out to it. The yellow line is my projected path, which I can control with the manuever node and when I like it, it will tell me how hard I need to burn and in which direction.
After playing with it, I've got a great path planned out and the orbit screen changes. The yellow line is still my projected path, and where it turns purple is the Mun encounter, where the gravity of the Mun begins to affect my craft and change it's course, and if I do nothing and just let it fly, the green line is the Mun escape, or the path my craft will take after being affected by the Mun's gravity.
Right now, I've got it lined up perfectly. The KSS Long Shot will sneak up around the backside of the Mun, where all I will have to do is a small retro burn and I'll fall into orbit around the Mun. However, following the purple line, it goes through the Mun, which is a clear way to say that if I don't get into orbit, the Long Shot will crash straight into the surface. Yikes!
As soon as the maneuver node is set, you'll notice a little yellow bar on the right on the nav bar and a blue icon on your navball. That blue icon tells you where you should put your crosshairs in order to perform your burn, and the yellow bar tells you how much more you need to burn. As the Long Shot nears the maneuver node, it begins to burn hard, and sure enough, the apoapsis begins to balloon out and reach for it's projected path.
Bingo! Just as predicted, when the yellow bar gets down to nearly zero, the Long Shot is on a nearly perfect intercept orbit with the Mun, with oodles and oodles of fuel left. For now though, the Flight Crew settles in for a long wait as the Long Shot flings out to the Mun.
Before getting too far out, the Flight Crew remembers that they need to blow the nosecone off the Long shot to expose the probe and mapping gear. The probe itself is rather small, about a fifth of the length of the craft. For now though, the bottom stage and atomic motor still have plenty of fuel and keeping them around won't really hamper much, so we'll keep the probe attached until the bottom stage runs out of fuel. No sense in wasting good fuel!
After a good bit of drifting, the Long shot drifts across the Mun Encounter point and shit starts getting real. The Long Shot has been picked up by the gravity of the Mun, and it's being pulled in. The new blue line represents the new orbital path I'm on, and the golden line shows where I'll end up after passing the Mun. However, we have a problem. Flight Control had a little too much Shasta and Potter's before the launch, and bodged the approach. We're coming in way, way too low to the surface of the Mun, and we stand a good chance of slamming into the Mun instead of flying by it. Even if we don't crash, we'll still be far too low to do any mapping, which needs to happen in a stable orbit around 350km from the surface in order for the equipment to work properly.
Our situation is easy enough to solve, however. The Long Shot points it's nose forward and into a progressive burn, pushing the periapsis up from the surface to a much more roomy 100km. Now that my periapsis is secure and not on a collision course, I can left the Long Shot drift closer to it's periapsis and then perform a retro-active or braking burn to slow down, which will begin to pull in that arch around the Mun until it snaps back into a nice, beautiful blue ring and I'm in orbit around the Mun!
The Long Shot drifts lazily through space around to the dark side of the Mun, where Flight Control expertly careens the ship drunkely around it's axis and fires a little retro burn that snaps the orbit firmly around the Mun. At this point, it's almost mission success, we just need to perform a few now familiar Hohmann orbit burns to raise the periapsis to 350km and another to lower the apoapsis to 350km to result in a nice, stable and consistant orbit and flip on the mapping device, and hope the engineers screw it together properly!
At long last, the Long Shot is in a stable 350km orbit around the Mun, and a hushed silence fills the control room as the Chief of Flight Gerhard Kerman flips the big red switch for the mapping device. Soon, the first bits of data start to show up on the output screen as the probe soaks in the surface of the Mun. Regulation volume cheers erupt in the control room and the orderlies begin to hand out standard issue party hats and snack trays in celebration.
Success! The mapping equipement I used is the stellar ISA MapSat pack, and it functions much like radar topography does in real life. A radio dish sends a radar wave down to the surface of the Mun, which bounces back and is read by the dish, and because radar waves lose strength the farther they travel, logically spots lower on the surface will require the radio wave to go a bit further before bouncing back than the mountains or high spots, so the minor fluctations in the strength of the returning wave can be interpreted to create a topographical map of the surface below. After a few passes, the Long Shot has fully competed it's mission in giving us a map of the Mun!
And here we see the fruit of our labor! This is it, the surface of the Mun! It may not seem like much, but the map contains a huge amount of important data for us. Dark blue, light blue, green, yellow, red, and white, in that order range from lowest to highest, with dark blue being 0 meters, or sea level, and white being 3500 meters. From this map, we can see that most of the Mun is relatively flat, with the best spot to land being on either to the north or south poles, away from the craters around the equators.
The red icons on the map are very interesting, however. They represent 'anomolies', or readings that the scanner just can't explain. Given we've already found one easter egg on Kerbin itself, I'd be willing to bet that some, if not all of these anomolies are easter eggs, just waiting for us to find them! Priority one for the Kirby Space Program is immedietly swinging towards developing a rover and a lander to investigate these anomolies! Stay tuned!
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