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)

Sunday, 28 February 2016

Change of plans

There are three missions which require a huge spacecraft, aka spacestation in Kerbin orbit, aka surface outpost on Minmus, aka spacestation in solar orbit. The game´s mission check is such that I can fulfill all missions in with one single ship, provided that I build it after I have accepted these contracts.

However, to proceed like this seems like cheating. Since I am almost at the end of the tech tree and have enough cash anyway, I decide to play it a bit more realistic.
First task, a habitat module for Kerbin orbit, to be docked to the Spacewreck Terminal for the first mission contract. I built it as a ring structure in order to simulate artifical gravity by rotation. And plenty of docking points of each size, because it will extent the orbit capacity as a transfer terminal.
Launch. It takes some tries, aka reloads. First, I have to add a lot of struts to make the whole structure stable enough to withstand the drag. Then I have to figure out the path to orbit. A standard gravity turn is not possible due to excessive drag of a monstrous structure like this, so I need about 20% more deltaV to launch it straight up for a long time, until the atmosphere is so thin that the drag is no hindrance anymore to turn it in orbital direction.

After a while, the Transit Terminal has made it. The launch stage was constructed as an SSTO (single-stage-to-orbit), minus the usual booster stages for the first 100m/s. However, now that it is up, instead of guiding the launch stage back down, it could rather double as a huge fuel depot. This could totally replace the improvised Spacewreck Terminal as a whole, after I fulfilled the mission contract and docked both together.

In the meanwhile, the Spacefish launches from Spacewreck Terminal for its second itinerary, a Minmus flyby for four tourists.

Now to my favourite, spaceplane construction. Unfortunately, the construction is hindered by some weird inconsistencies. When I attach wing parts together, why do they not form a whole and behave like this? Totally annoying and only fixable by adding unwieldy struts everywhere, thus amplifying drag, which in turn is very damaging for a spaceplane´s performance.
Jeb, is chief test pilot, because he grins and laughs even when everything totally goes wrong...

... like here. After spending many hours trying to finally get a version up into space, rendez-vous and dock it to Spacewreck Terminal for a transfer of 2880 units of fuel (a proud figure!), re-entry gets screwed. I guess I did not look properly for where the plane´s center of mass (CoM) was located when devoid of the heavy payload/fuel!

I needed two flights up to Spacewreck terminal, because the mission contract requires that the spacestation has a fuel depot with 5211 units of fuel. However, this version of a spaceplane supply will not make a second run. Just barely I am able to stabilize the fall at about 8km altitude...

However, when the center of mass is behind the center of lift, it is almost impossible to keep the plane stable. At 5km altitude, it therefore suddenly sharply veers off, and the drag forces do their job and tear the plane apart. Thankfully, there are enough wings left to guide the remaining parts remotly safely downwards.

I even manage to produce a landing, making a sacrifical touchdown with the backpart hitting first and again shearing it apart. Priority was to save the crew, and thus I still count this as a successful mission, in Kerbal terms. However, economically this was a total loss of about 110,000 Credits.

Back to something easier. The Atomic Kitten has in the meanwhile left Minmus SOI and needs about eight days to return to a 70km periapsis at Kerbin.

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