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)

Thursday, 21 May 2015

Planes engineering

A report about another two or three game sessions.

Switch back to Kerbin. I want to do something else instead of just fast forwarding and going along with the return of the Mun Mission Ship. Since I now have spent a lot of time in space, I somehow yearn to do some atmospheric flying again. True, the plane flight controls are a pain in the ass, especially SAS´s weird way of balancing out a course which often causes a near endless pendulum movement of the craft, but there is something especially exciting  about flying and landing a plane, too. A mission contract which asks me to collect barometer data around the same continent comes in handily. And instead of using one my old trusted plain from the "Fleabite" product line, I build a new model, which has two jet engines and thus should achieve a continuous near-Mach speed even when ascending. On top, a Reliant engine is ready to propel it to supersonic or to altitudes >14km if needed. I call it "Starflighter".

 - now... how to land there?

Unfortunately, once I arrive at the scenery, all three nav points are on the surface of a mountain area. While I do have a parachute on my plane, this would be only good for one landing. Hmmm... circling around the area, I think I see a upward slope which could be enough for a controlled normal landing. Careful, careful, slowing down the plane as much as possible before touchdown, aaaand touchdown! Yay! Catching the measurement, I easily again launch downhill.

Ooops. The plane wiggles a lot; I realise that one of its wings touched the ground during landing, breaking off an elevon. But it remains controllable. So I think, until in a tight curve, the plane veers off and dives uncontrollably into the ground. Damn. Reload! The next hour, for obvious reasons, I try to construct a VTOL plane (vertical take off and landing). Which is unsucessful. I get impatient and launch another Starflighter. This time I fly even more cautiously and indeed manage to land and take off from all the nav points. Because of the added difficulty of the mountain area, this again feels like a great achievement and with this I am happy to switch back to my operations in space.

The Mun Mission Ship with its valuable payload of scientific data gets thrown into Kerbin SOI and I lower its periapsis to 38km for a good aerobreaking. I am glad that I estimated my fuel requirements well this time, leaving any excess back at the Scientia and its newly assigned Lander. 

Back at the Space Center, a new expedition needs to be launched; there are now four Kerbonauts from rescue missions stuck in the Scientia, and they sure want to go home! (and I want to finish off the according contracts!). For this transport, I re-design once more the Munbus Reloaded. Docking port, check. Moar parachutes, check. RCS for docking maneuvers (plus additional monopropellant to do so!), check. An additional sliver of a fuel tank for those expensive polar orbit maneuvers, check. And, what can I say, I finally have a Munbus-class ship which is perfect and fulfils all mission specifications without trouble.

- pinnacle of the "Munbus"-class ship line


After I launch and send the Munbus to Mun, I let the Mun Mission Ship land. It turns out the the aerobrake is too much and causes an immediate atmospheric re-entry. Drag has definitely increased since I last did an aerobrake in beta 0.9! Thankfully, the Mun Mission Ship swallows the additional thermal assault from the increased re-entry speed without complaints, by staying retrograde and the Terrier engine absorbing most heat. With an astounding 538 science points, I recover this not too-well designed but nevertheless tremendously successful vessel. Time for another bottle of champaign!

There is now enough science to open two 160-point tech nodes and one 300 point node. This means, all plane parts are available for an attempt at reconstruction of the White-Goose class space plane. This baby should be able to carry 6 crew members, thereby being able to exchange a full Munbus-crew, and bring at the same time enough fuel to refill the Munbus. This is going to allow to specialize my one existing Munbus ship as a crew transfer stage between Kerbin and my Scienta-class ships around Mun and Minmus, maybe later even beyond.

- a White-Goose prototype with six turbojets already gets into Mach 1 on an early 40-degree ascend angle; talk about over-engineered!

Two game sessions later, at least 10 different attempted plane configurations and a lot of moaning in the forums later, I have to realize that the new atmiospheric physics model severely cut down the efficiency of my space plane. Not a surprise, I almost had expected this. However, I finally manage to adapt the construction and the ascend profile such, that I can bring half of the originally intended amount of fuel as payload. 720 units of fuel are enough to almost fill up the Munbus.

- this iteration gets up, but has no fuel left for transfer; I also discover that hiding solar panels in the docking bay does not really protect them from heat, but only from sunlight...

The key issue is that a sufficiently fast flight with the turbojet gets only as high as 21km (opposed to being able to get all up into orbit with turbojets still in the in beta 0.9 game). Thus, you need to activate rocket engines earlier, you thus need stronger ones because you are still to much down in the planet´s gravity well, and much more fuel of course. The latter again gimps your thrust-to-weight ratio (TWR) up to that magical barrier where adding more fuel won´t increase the vessels deltaV potential anymore.

Key to solving the problem was to not only add more fuel and more jet engines; indeed it prooved that four turbojets are still enough even for a space plane of 70 tons mass! The key was rather to get rid of the Mk2-plane parts and the two "Reliant" engines in the aft and completely replace that part with Mk2-rocket fuel tanks and a powerful big Skipper engine. Like this, the TWR was sufficiently high to also do a sufficient push on all that required additional fuel (about 20 tons more than the orignial plane in the beta 0.9 client needed!).

- this one is very close to my design goal; unfortunately, it breaks apart during re-entry...

With my about dozenth flight, I finally have a White Goose Mk4 in orbit. Unfortunately, it explodes on re-entry. It probably did not cool down properly after ascend, doint re-entry almost immediately. Anyways, this is close to viable result and I am very happy with this success agains all odds!

The problem of re-entry is fixed with just one more iteration and the next test flight yields 100% success.

- design goal achieved! This view of the "White Goose Mk4" has the heat-overlay activated (F11). Four airbrakes slow it sufficiently down during re-entry and also serve as heat radiators while in orbit

With the "groundworks" now properly covered with the White-Goose, I can focus on the next ambitious goals in my game. As an afterthought, I accept a contract to deploy a station on Mun and two Duna centered exploration and survey missions. Not sure if I did the right thing, but with me maxed mission control building at the Space Center, I can accept as many contracts as I want; they are going to expire only years later. For example, as a first step, I might want to also put a space station in Kerbin orbit; just still a fitting contract is missing.

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