Engines and guns

Engine: Pods or big thruster style?

Big build in thrusters are usually easier to make because you only have to worry about the looks of the small part showing on the outside, while most of the engine is supposedly located inside the main bulk of the craft - in theory at least: usually it's a much better idea to use the space for structures supporting fancy stuff showing on the outside.

Engine pods on the other hand are infinitely more tricky:

• Everything is out in the open.
• Being pods, they should probably be somewhat smaller than the actual craft (unless it's a racer with ridiculously large engines and/or pods that contain the fuel as well), so you have to come up with a clever, compact design, that echo or at least live up to the design you invented for the main bulk: You started out making the most fancy design you could come up with and cram into the main bulk, now you have to come up with something similar with only a fraction of the space.
• One of the main reasons to actually have engine pods out in the open (besides heat dissipation) is the ability to make maneuverable engines: If you fire your engines in space you will continue floating in that direction until you fire equally in the opposite direction: Movable engine pods can do that trick, saving you from turning the whole craft backward to slow down or mounting a huge battery of fixed engines pointing forward (and in all other directions), that will only be used seldom, while being dead weight most of the time.
  And let's face it: it just doesn't look very cool to approach with your butt forward. Especially if you've placed all the cool guns and armour in the front (engines aren't that easy to encapsulate in armour plating).
• Maneuverable engines pose a vastly complex challenge, compared to ordinary fixed pods, since you have to incorporate moveability into the already crammed design, and make the connection look solid enough to survive the stress between the thrust of the engines and the inertia of the main bulk of the craft. On top of that, unless the pods come with their own fuel tanks, reactors or the like, you'll probably have to hint some pretty thick power cables or fuel pipes passing via or around the joint between the main bulk and pods.
  Most of these considerations apply equally to gun turrets btw.

Basically, all the difficulties enumerated in the theory above implicate, that if you wish to have engine pods, you better start working with them at once: They're difficult to make, and hard to fit into the design.

Basic flight mode. Notice the little dark grey racer body used as greeble right above the wing gun. A great many thanks to Jakob Bindslet for donating a handful of these, and to Jan Beyer for a whole bag: I'm going to use those that type of parts a lot more now compared to earlier, when I had only 2 or 3!

Back to the Longship: In the Longship Project, the first three months went by designing (early versions of) the cabin and stern. A little over two months into the process I designed the large main engines 3/11 2004, followed by the smaller pods three days later, 6/11 2004.

Since these were only my third and fourth attempt at movable engine pods, I was really on pretty loose ground. Apparently this wasn't difficult enough, since I decided to try my hand on wheel engines, one of the most loathed concepts in the Spacer world, because it's really hard to make them look good and not tacked on, making the craft "look like it's hauling somebody else's spare wheels" as a spacer aptly put it a while back on CSF.

Shape and scaling: Basically I thought the barrel/onion dome/torch shape would fit the Viking design pretty well (a lot of them traveled on the Russian rivers), and I'm particularly satisfied with the smooth shape achieved in the large engine pods. The downscaling of the design to the small wheel diameter didn't live up to expectations though.

Distribution: The flat  hexagonal distribution of engines with the two big ones on the sides, and a pair of small ones above and below was chosen in order to mirror the cabin section, and fit within the long narrow lines of the craft without sticking out too much.

The most energy you'll ever use will be to get off the ground, so why not make the engine pods double as VTOL system (Vertical Take-Off and Landing)?

Full reverse. Since all the engines are placed "in the shadow" of the cabin, they can't rotate 180 degrees and fire straight forward, because the cabin and wings are in the way.
However the different thrustvectors in this configuration approximate a 180 degree thrust even though it's a little hard on the craft.

Full reverse again. Notice how the larger engines pass neatly between the wing turrets and the cabin. Since the small pods can only turn around one axis, the horizontal maneuvering is done with the large ones.
I had to use old friction pins for the big engines because the new ones are simply too weak for the weight.

Guns

Like with engines, the utility of guns are proportional to the degree of movability: 

Fixed guns: Usually found on small one man fighters fixed in a forward position: Think 1st and 2nd world war. Back then, with no computers or automated targeting systems, this was the only way you could hit anything.
In the space age, however, fixed guns are a serious drawback:
a) firing at long ranges, you have to aim REALLY precisely, and if the other guy is doing the same, you're just going to kill each other.
b) returning to WW2, you've seen the movies of Kamikaze pilots attacking warships: flying through a barrage of defensive fire is not a nice thing, especially if you have to keep a moderately straight flight path to hit it.

Adjustable guns: Adjustable guns solves the problem with hitting small targets at long ranges, and they can to some degree be used while doing evasive maneuvers while still keeping the guns on the target: This was basically the idea behind the "loose" guns on the 61 Shark2 fighter. But you're still limited by their angle of movement, and you're still basically flying directly toward the enemy, except when you're having him on your tail and are screwed.

Gun turrets placed directly on the hull of the craft with two axis of movement are usually able to cover an area of around 90x360 degrees, or half of the skysphere around the craft. This gives them a big advantage over fixed and adjustable guns, since you can defend yourself from every angle with only two turrets on either side of the craft (think: the Millenium Falcon from Starwars), and have double firepower along the narrow strip around the horizon where the two hemispheres meet. This is fine when you're attacking less agile targets or retreating from them (assuming that the horizon crosses both the front and back).
However, when you're under attack from more agile crafts yourself, having only two turrets can cause you trouble, as most angles apart from the horizon is only covered by one turret: agile crafts will position themselves in these huge "weakspots" and probably cross between hemispheres regularly to cause confusion, because when the target drops below the horizon of one turret the other turret has to "take over the target", turn and continue the fire: If the other turret is busy engaging another target on it's side, it'll be too busy to take over, while the first turret will be idle until either a) a target returns to it's  hemisphere, or b) you bank the craft to bring the targets into the horizon area or fly in between the targets.
Ideally you'd have more turrets with overlapping angles of fire, so the transition from turret to turret can be smoothened. If the turrets are fed from a centrally placed source (like with electricity from a reactor) it's also worth considering to make it slightly underpowered so you'd have to prioritize the different functions: like allocating power from the engines to take out tough targets, or vise versa to attack fast or flee.

That must be plenty of theory for now, back to the Longship:

Broadside

Armament: The armament consist of 8 turrets:
4 medium caliber stern guns
2 medium caliber wing guns
1 light caliber rear gun
1 heavy caliber main gun

The rear gun and wing guns are fast firing gatling type guns, the light rear gun trades the higher calibre for higher ROF.

The stern guns are of the same caliber as the wing guns, but without the gatling function has a lower ROF.

The main gun is the craft's heavy calibre weapon intended for blowing holes in blast doors, and medium armoured vehicles like tanks or warship.

Full barrage: turn a little to the left, and you should actually be able to use all 8 guns at once. Straight ahead, you can only use 7

Firing angles: The craft is heavily armed and decidedly attack oriented:

Front: 7-8 of the 8 guns cover the frontal area, and they have a limited firing angle of around 45x120 degrees with a small overlap in the front:
Flying roughly straight toward it's target the craft presents the smallest profile and the largest amount of firepower.

I ought to get a bigger background. Notice that the main gun is mounted considerably lower than the rear gun thus allowing it to fire backwards at pursuing warships.

Sides: up to 5 guns can cover the sides down to an angle of between ± 10-90 degrees, giving the craft good abilities to hover around the war zone, sweeping the ground with suppressive fire, taking out armoured walls and vehicles with the main gun: just the kind of surface warfare where you'd expect troopers to be effective in the first place.

Rear gun

Rear: when the loot has been loaded, and it's time to get away, the angle directly behind the craft is covered by 4 guns: the main, the rear, and the wing guns.

However just above and below the rear is only covered by 2 guns because the top- and belly-mounted guns are hardly able to cross down below the horizon.

Main and stern guns.
One of the things that annoyed me about this model is that I couldn't cram in some rockets to complement the direct fire of the guns.

Top and below: with the heavy vertically distributed firepower, the craft is relatively weakly defended against attack from above and below with only 2 guns on either side (the wing guns above, and the main and rear gun below).

Go to: 67 Longship, Engine and guns, Interiour, landing gear & hatch