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)

Wednesday, 25 March 2015

Again Kerbal Space Program

Just a short update what I am at right now. Elite is canned again for the time being. The Occulus Rift still not out, and I am still not sure where Elite is headed after that bare-bones release. Just grinding missions and money for different ship skins does not cut it for me, and the sheer beauty of all those red, white, blue, yellow, orange stars are just not enough to keep me entertained for hours and hours. Compared to Kerbal Space Program, the variations in your ship´s setup are virtually non existant. Combat or Trader, and not much difference for an exploration setup.

Well, yes, Kerbal Space Program on the other hand... just have a look at this thread, for example.

The mix of building, trying out and, eventually, succeeding against all odds of physical laws, those challenges do have a certain addictive gravity. Also proving that a truly true sandbox game can very well work with a quest-like mission campaign as a focus.

And, it is flying in space, with landing on planets! Landing on the Mun is such a satisfaction, as is a successful landing on Kerbal after a mission. It turns out that designing and flying a "spaceplane" or a rocket which does not jettison any parts from launch until landing (SSTO - single stage to orbit), seems to be the hardest challenge.

Needless to say, steering a spacecraft in Elite: Dangerous is for four year old kids, in comparision.

My short list of achievements so far:

- Can handle satellite deployment like a pro. Figured out a setup which is cheap as dirt (7,000 Credits only, versus a profit of about 20,000 to 50,000 Credits or even more): A 3-ton satelite with a light Rockomax 48-7S engine on an entirely small-booster launcher (stage S1: 3 RT-10 Solid Fuel Boosters, the center one fires as S2, S3: 1 booster), which easily achieves an initial apoapsis of 100,000 km and thus plenty of time for the small satellite engine to raise periapsis into >70km orbit and plenty of fuel left to achieve wide-ranged orbits around the planet or one of the two moons.

- my satellite rocket launcher

- Did a one-stage low-tech Mun landing with a setup similar to in this video. Needed four tries, every piloting mistake leeches off the scarce fuel and thus left my pilots stranded in space; even managed to catapult one of them on a one way trip into solar orbit. Ouch.

- "Moonwalker", with jet engines in the mix

- Brought a spacestation into orbit; wondering now what use it could be, except for having fullfilled a mission, the game does not have any game mechanics connected to it. Maybe as a refueling point for later launches?

- Learned how to rendez-vous and dock. Let´s say its just so much more faster to just launch and go where you want to go instead of this tedious process of matching orbital speed and heading in newtonian space, with just those good old fashioned liquid fuel engines and limited fuel.

- Constructed a spaceplane and finally managed to fly one into orbit. However, atmospheric flight physics is a bitch, even with the game´s simplified model!

Spurred by my success to actually being able to construct - and also properly pilot - a space plane as an SSTO (which took quite some time to figure out), my strategy plan is to use those for efficiency´s sake to handle ground-to-orbit business, such as refueling the space station and to send and assemble vertiable spacecrafts in orbit and supply and refuel them there via the space station for various missions in the solar system.

Currently I have one space craft (I call it affectionately "Warthog") ready for leaving orbit for Mun (I have stacked a number of survey missions both on the surface and in flight there). Launching it into orbit used up most fuel and I am in the process of refueling it via an SSTO plane.

While the mentioned smaller 18-ton spaceplane already had managed to transfer a proud number about 400 units of fuel, my space craft has room for 1440 units. I probably would not need a full tank just to reach Mun, but I am nevertheless going to need it for landing either the spacecraft itself or/and in parallell fuel a small lander spacecraft for multiple landings and flights. And did I mention already that docking in orbit can be quite a hazzle?

So, in order to cut down the required number of preparatory orbital rendez-vous, a bigger space plane is in order. However, its construction incurs some problems. I use a similar layout as for the 18-ton heavy version, just that it now is 30 tons heavy. Something is wrong, though. While I already expected that take-off would be a bit difficult due to all that fuel in its hold (960 Units reserved for fuel transfer), the real problem starts at greater height when it picks up supersonic speed levels (from about 500 m/s onwards). The plane just flips over and tumbles down without any chance to regain control. Trying to keep the angle of attack very low screws my apoapsis at some point (engine thrust is too weak to keep the plane on an ascending course), and I am not sure if that helps, anyways, so I am not the wiser just by exercising piloting by my guts.

Now, I researched a lot in videos on fora on the possible issues behind it. The most common one, the center of mass being behind the center of lift, seems not the culprit here. I have the center of mass placed a good chunk forwards, to a level that even take-off gets to be an art in itself. It is also pointed out that using up fuel causes shifts of the center of mass; I covered that by checking the distribution with full and empty fuel tanks and all stadia in between and balanced it out that there is not much shift in the center of mass.

There are two more factors which could be a cause: The center of thrust could be too far below the center of mass, thus pushing the plane up once the ram jet engines´ thrust increases at greater heights (not sure though, thrust should decrease due to less scoopable air, just speed increases due to less drag due to thinner air). Or the center of lift is still too much in the middle of the plane axis; this is good for low altitude controlability, but could be bad at upper atmosphere, supersonic flight levels (not sure though, a forwards center of mass should sompensate and thus not be influenced by speed).

It is just weird that my smaller plane seemingly did not have that flipping issue. But, well. plus ten tons is plus ten tons and basically makes for a totally different plane, right?

Once I have solved this problem, I am going to be happy to have this plane as a drone-fueling spaceplane and a similar-weight-design model as a passenger liner for orbital supply ferrys, and can finally focus on the space travel itself. My current Warthog-class spaceship in orbit is very rudimentary. It consits of an Apollo-style 3-man cockpit, a crew quarter and a science quarter and a Rockomax "poodle" engine with the said 1440-unit Rockomax X200-32 Fuel Tank. Landing struts, docking port, solar panels, RCS steering jets. I designed it this way so that my passengers do have some room for comfort, and it also can count as a space station for some of those missions (space stations have and seem to be only defined by a high crew requirement).

My ultimate plan is to launch light weight modular elements, which I can assemble in space via docking clamps according to what kind of spacecraft I am going to need, thereby re-using what I already have instead spending my finances for building and launching everything anew. Higher tech levels offer nuclear powered or ion engines, for example, which are well suited for interplanetary travels. A host of different landers and land rovers can be constructed for each planet with their different gravity and atmospheres.

Looking forward to it; this game has quite some stuff to ponder about. A kind of Lego in space, for adults. Jay! It would be cool if the game would evolve over the years with some "science-fiction mods", so that at some point, we arrive at an Elite-like game environment? Well, I can dream, can I?

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