Greetings. Figured I'd share my first ever manned interplanetary mission with a lander, and the ability to return to Kerbin. This mission took six brave kerbals to the surface of Duna, and back again to Kerbin. Design and mission planning During the design phase, I experimented a bit with trying to calculate the fuel requirements beforehand, and at the end of the mission, I got my crew in a orbit around Kerbin with only 943 m/s of delta V, or 1.548/1.892 fuel/oxidizer left, which isn't too bad considering how over engineered some of my earlier constructions have been. Given the formula delta V = Isp*g*ln(ms/mf) where g = 9,80665 m/s, ms is the initial mass and mf the final mass, I figured that the delta V of a vessel in KSP could be calculated more easily by subtracting the initial mass with the mass of the fuel and oxidizer used in said burn with delta V = Isp*g*(ln(ms) - ln(ms - (100*f/9))) where f is the amount of fuel as shown by the interface of KSP. Then, by looking at the specs of the various engines and fuel tanks on the wiki and rearranging the formula, I got f = (648*(mc+me)*exp(delta V/(Isp*g)) - 1) / (7201 - exp(delta V/(Isp*g)) where mc is the mass of the craft I want to move and me is the mass of the engine I want to use. This formula would give me a decent enough number on the required amount of fuel (dry mass of tanks included) needed to get the required delta V for my mission. (This one is based on the SPS tanks though. All the other tanks had a slightly different dry mass to full mass ratio.) The initial plan for this mission was to have just one landing on Duna, but in order to balance out the rather heavy and bulky lander, I had to add a set of fuel tanks on the other side, and quickly decided to have the tanks refuel the lander for more landing missions. As it turned out, the amount of fuel needed to get the CoM aligned was enough for a little over two more landings, so I decided to bring along enough fuel to have four landing missions. In addition to the Duna landing, the plan was to have six crew members along for the ride. Three pilots, one engineer and two scientists. This is how the space craft itself (no engine & tanks) turned out. Construction Upon the completion of the design, six of KSA's finest astronauts were chosen for this mission. Ludmin - Commander Lovan - Mothership pilot Errim - Duna lander pilot Gusgard - Navigator Neilfrid - Flight engineer Corvan - Science specialist All of them were veterans from the Artemis program, which brought kerbals on to the surface of the MÃƒÂ¼n and Minmus. As the launch window started to close in, the construction in orbit started, and it proved to be a heavy toll on the finances of KSA. I didn't have any launch vehicle capable of lifting the entire thing into orbit, so it took seven launches to get all the pieces assembled, another two to fill it up with fuel and a final one to get the crew up. The construction itself was rather uneventful though, and on T-17 days, the crew arrived. Initially, I intended to use a space plane to ship the crew up there, but some construction issues came up, and the plan was scrapped for a cheapish vessel. Kerbin departure On T-9 days, the final preparations were made. The Prometheus fired its main engine and placed the craft in a highly eccentric orbit, ready for the final burn for Duna. The reason for this manoeuvre was to use up the fuel in the two external fuel tanks on the rocket stage and ditch them before actually doing the final burn to escape Kerbins SOI. Not really sure if I saved a lot of fuel on that though. Then, 9 days later Prometheus I left Kerbin, heading for interplanetary space. And the crew settled in for the long trip towards their destination. Duna orbit and landings 361 days, and one mid course correction later, the ship encountered Duna, and placed itself into orbit. After a stable orbit was achieved, I checked how my fuel usage had been, compared to what I had estimated that I would need. It turned out that I had 5.442/6.652 LF/O to spare, which meant that a rather drastic orbit inclination change could be performed at a later stage. I did of course add about 500m/s more than what the delta V map said I would need, so that I could mess up a bit on the way to Duna without loosing the entire mission. After a day in orbit a landing site was chosen, and the first landing party undocked, starting their descent to the surface of Duna. As the descent went on, I actually started to become nervous, which I really haven't been in KSP for a good while. A lot were at stake, and if something were to happen, three kerbals would be lost. The landing however was successful, and Errim, Neilfrid and Corvan took the first steps on a foreign planet. (Errim being the first one) After one Dunian day, the crew departed and returned to Prometheus with some fuel to spare. The second landing mission, bringing Errim, Neilfrid and Ludmin to a different landing site, went along just as planned around 50 days later. On MET 1y:8d (50 days later again), the third landing party undocked. This time, Errim and Neilfrid brought Lovan along. For the first time, the landing party encountered some problems during the descent. They were overshooting their landing site, and would now land on a rather steep slope. Since the lander wouldn't be able to stay upright in the slope, Errim had to cut the chutes and "hop" towards a more suited place to land, using more fuel than what had been intended for the landing phase. As I started to ascend from the surface, I kept a close watch on the fuel levels, since a fair amount had been spent during the landing. The lander still managed to get back with some fumes left in the tanks. After another 50 days, an inclination change was made in order to get the final landing on the north pole of Duna. The last landing party to set foot on Duna was Errim, Neilfrid and Gusgard. By now, I had gotten used to landing the Duna lander, so I wasn't really nervous about not getting the crew back from the surface. This time, the crew stayed for two Dunian days before departing. After docking with the Prometheus and getting both the crew and science samples over, the lander and refuel tanks were ditched, and another inclination change was made to get the ship back in an equatorial orbit, ready for departure from Duna, and towards Kerbin. Duna departure and Kerbin capture At MET 2y:11d, Prometheus left Duna, even though they had to wait for one day, as Ike was right in the way for the ideal burn. This is the burn I ended up doing, and it went well enough since I didn't have to do any mid course correction burns to get a Kerbin encounter. 316 days after leaving Duna, the crew was able to see Kerbin again, nearly 3 years after they left. Some corrections were made to get the ship in a more equatorial orbit, and bring the periapsis at an appropriate altitude. Solar panels and dishes retracted in preparation for the Kerbin aero brake. After placing the ship into a proper orbit, the first return pod undocks, and takes Lovan, Errim and Neilfrid back to Kerbin, along with 41 science samples from Duna. As the first return party reports a successful reentry and splashdown, Ludmin, Gusgard, Corvan and 43 samples departs from Prometheus as well. The second landing wasn't as good, since it was a hard terrestrial landing, but it still went well. So as the last crew members are recovered, the Prometheus I mission comes to an end. Oh dear. This turned out to be a bit more than I had expected. Also, you'll have to excuse any grammatical errors and such.