Flieger, grüß' mir die Sonne, grüß' mir die Sterne und grüß' mir den Mond. Dein Leben, das ist ein Schweben, durch die Ferne, die keiner bewohnt! - Hans Albers, F.P.1 antwortet nicht (Adaptation in the 80s: Extrabreit)

Tuesday, 14 April 2015

Kerbals around Mun

Similar to those nice "Isinona-Videos", there are some neat "let´s play" videos out there for my other current game, Kerbal Space Programme. The good ones manage to entertain and educate the new player like me, like for example the series done by DFWanderingKid. Well done!

To continue my little excursory report on my ventures in said Kerbal Space Programme in the course of three game sessions:

After some more tries, I completely rebuild my drone space plane design and I finally make it work. It seems the problem of my previous design was indeed that the center of thrust was too much below the center of mass. Finally, I am able to transport about 900 units of rocket fuel up to my waiting "Warthog" space craft and land my space plane safely back down at the Space Center. Jay, that was quite a challenge! And my Warthog is finally filled up again to the brim with 1440 units of fuel.

- this one worked out (don´t know why and how, anymore...)

Sending up and docking a lander unit, my expedition to Mun is ready to go. The "poodle" engine fires up and the Warthog´s potential deltaV looses about 800m/s until it is on intercept course for the Mun. After I burn retrograde, my first mission is checked; I have put a "space station" in orbit around Mun.

- "Warthog"

The rest a mix of "flight over" and "land" missions, for which I use my lander. However, it turns out that I once more brought along a too little amount of fuel. My lander barely manages to land at two close-by nav points and to get up again into a rendez-vous-orbit with the Warthog. I have to switch to the RCS monopropellant tanks in order to finalize the orbital rendez vous. On top, I placed the RCS thrusters wrongly, i.e. not at the center of mass, which causes every try to apply lateral or vertical thrust in a rotation of my lander, effectively leaving it only with forward/backward thrust in order to to a relyable straight approach. With a little bit supportive maneuvering also by the Warthog, the Lander is finally back docked. Whew. What is tremendously helpful is a mod which finally allows me to actually see the nav points during flight, not only on the mission map; I am sure I would have used much more fuel without a clear guidance.

- minimalist lander

The Lander gets re-filled and is off again for some flights over some nav points, taking crew reports or temperature logs. Again, I underestimated how much fuel the required angular shifts of the orbit takes up. After catching the last nav point, there is not enough fuel to re-angle back to the Warthog´s aeqatorial orbit. I have to use the Warthog with its much bigger and thus much more inefficient engine to catch up with the Lander´s orbit.

After this maneuver, I have only left about 200 units of fuel, which translate into a deltaV of about 670m/s. I wonder how much I need to get my spaceship back to Kerbal? Can I siphon off another 110 units for a last excursion with the Lander before? Certainly not... playing around with a maneuver node, I realize that I need a deltaV of about 200m/s in order to get back at least into a remote Kerbal orbit, with a periapsis of about 5 mio km. So, no way I can get back my crew and resolve those last two nav points, albethey close to each other on Mun´s surface. What a pity. Maybe I should send a mission up to re-fuel the Warthog instead of leaving now and coming back later. What approach is more efficient, I wonder?

I decide to decide this in the next session; if my Warthog gets stranded around Mun, it is not a big problem. After all, the Warthog was built as a spaceship/spacestation hyprid and thus as enough room for my three Kerbal astronauts to not get crazy during long séjours (I am sure they can play plenty of Elite: Dangerous on the ship computer during that time in offline-modus...)

I am very content that my mission made it this far at all, despite my misestimates on the fuel requirements, my beginner-style flight maneuvers (I am sure I am burning more fuel than required if I knew more about orbital flight mechanics) and the crappy RCS capability of my Lander.

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