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NFDesignNotes2
 
Designing Nightfighter
Designer's Notes by Lee Brimmicombe-Wood

Part 2. Sketching Out the Design

THE STORY SO FAR: Having decided that a nightfighter game should focus on hunting enemies in the dark, I adopted a blind-play system in which an umpire fed information to the player.

Having set out the fog of war system, the next step was to sketch out the game's parameters and address that ever-critical problem of scaling. As with any project you approach the design from multiple directions at once. Here are some of the major issues I had to ponder, and the assumptions that I would build the game around:

Unit Density:
In real life it was too dangerous and impractical for night fighters to operate in formations, so the archetypal scenario would portray a lone fighter hunting down one or more bombers. Even 'free fighting' techniques such as Wilde Sau and Zahme Sau would probably not require more than a handful of aircraft on the map at any time. This low unit density promised rapid play.

The Opposition:
The opposition in the game were going to be bombers. Historically, these big, ordnance-laden aircraft did not manoeuvre. They navigated long distances, flying straight and level courses except for turns at pre-planned waypoints. Like the nightfighters it was too dangerous for them to fly in tight formation, so instead they would gather into very loose 'streams' and fly as a gaggle towards their target.

This immediately suggested that there was little for the umpire to do other than to man the guns. Furthermore, reading post-war interrogations of the German aces, it became clear that the majority of bombers at night never saw their attacker coming or were able to respond. The umpire would not have a huge amount of input into the bomber defence.

After some reflection it seemed that the most sensible course was to treat the bombers as robots. The bomber stream would transit the map, with aircraft flying in straight lines from one end to the other. The player's job was to find and fix these bombers.



ILLUSTRATION: The game map is arranged so that bombers transit from top to bottom down the hexrows like simple robots. There is still plenty of space on the map for a bomber to hide in.

One decision made in early testing was to reduce the density of the bomber stream for the Wilde Sau and Zahme Sau scenarios. To get an authentic RAF bomber stream of 1943 vintage required some 90 or so bomber counters to transition the map area in the time allotted. The workload on the umpire proved to be immense and so I deliberately scaled this back to create a less 'target rich' environment.

Performance:
Day fighting games often expend a lot of effort on modelling aeronautical performance. They try to distinguish between aircraft turning circles, speed and climb performance. Fortunately, the nightfighting premise permitted me to chuck that baggage out of the window. Historically, nightfighters didn't manoeuvre hard except in emergencies. Instead, the business of flying pursuit interceptions with primitive radar meant that careful, slow, constant-rate turning was required. Since agility was a low priority, medium bombers and heavy fighters were adapted for the job, as they had the size and stability to carry lots of electronics, a big gun battery and plenty of fuel for a long endurance chase. In the game I could simply ignore turn performance and assume that all nightfighters behaved in a broadly similar fashion, describing large turn circles in the sky. Only in emergency situations, such as avoiding a destroyed bomber, would we have a fighter doing anything agile.

Far more important to the night hunter than turning ability was the amount of speed available for overtaking an enemy. Speed was everything. The four-engined RAF bombers were actually faster than many of the night fighters and the only reason the Nachtjagd stayed in business was because the bombers, for various practical reasons, flew at less than their top speed. Even then the German Me110s and Ju88s had barely enough speed to sidle up to their prey. In battles that took place at over 200 miles per hour, the difference of a few mph of overtake speed was critical and I felt I had to model this in the game.

Altitude was another consideration. Climbing to height takes too long to resolve in a tactical game. If the fighter had to climb to catch a bomber it would be a long way away before the fighter ever got up to height. So I decided that one of my other big assumptions was that aircraft would start close enough in altitude that height was not a factor. The exception to this was where the fighter had purposely started with a height advantage over the bomber that it could convert into speed. Where speed margins were narrow, this was often necessary for tired 'old crows' like the Me110F-4 to catch an enemy. So I added a rule for height advantage which could be readily exchanged for extra speed.



PHOTO: Many German nightfighters were crippled by speed issues. In theory they were fast twin-engined types, but engines and airframes did not keep pace with the development of four-engined bombers. And the drag of specialist equipment such as radar aerials and exhaust hiders could easily take 10% off the top speed. The Luftwaffe tried to develop fast nightfighters equivalent to the Mosquito, like the pretty, wood-airframed Ta154 in this photo, but the loss of critical glue technology due to Allied bombing soon put paid to the program.

Scale:
The performance considerations fed into the game scaling. One mile hexes and one minute turns are a huge departure from the kind of scales you see in tactical air games. Compare this with the Fighting Wings series, where hexes are often in hundreds of yards and turns represent seconds. However, rather than knife fights in a tiny portion of sky my nightfighter game would feature pursuit chases that would take place over distances of ten or twenty miles.

The scale was also, in part, set by the physical map size. To keep the game's sprawl under control, and to permit the umpire to keep his map easily hidden, I'd decided to use an 11 x 17" mapsheet for the umpire. With standard-size hexes that gave me an 18 x 28 hex chunk of airspace. At one mile per hex that represented depth almost exactly equivalent to a Himmelbett Raum or a 'Smack' fighter box, but with the width of an historical bomber stream. In retrospect it almost seems too good to be true, but there you have it.

This scale meant that movement speeds were going to have to 'stretch' a bit. If a four-engined bomber travelling at 230 mph moved three hexes a turn then the kind of minor overtake speeds I needed were not going to show up at all. A 10 mph overtake was going to translate into 0.13 of a hex. So I needed to exaggerate speeds slightly, using a formula to generate speed values in terms of overtake (or undertake) rather than absolute speeds. I also pulled an old trick of tracking half-hex movement by letting some aircraft move an extra hex on even-numbered turns. This allowed me to incorporate minor overtake speeds with little workload on the player. It has proven successful in playtest.

Visible distances also had to 'stretch' a little. Visual sighting at night was affected by many factors, including the moon and the air pollution that was rife over the Ruhr. So I devised a visibility setting that would control the maximum visual sighting distance in the game. Distances to searchlight-illuminated objects could match real life and I set these at around five miles. However, real-life visual sighting against unilluminated bombers generally took place at around 250-300 metres. At my scale this would result in most visual tallies taking place in the same hex. To show those few occasions where visibility at night could be really excellent, particularly under moonlit conditions, I decided to stretch the highest level of visibility out to one hex on the map. This was an intentional exaggeration to give a flavour of these exceptional conditions.



ILLUSTRATION: This scale illustration shows a Lancaster bomber in the middle of a mile-wide hex. The light circle around the bomber represents the zone in which bombers could be seen with certainty at night, around 250 metres from the bomber. Visual ranges could vary widely. The ace Heinz-Wolfgang Schanaufer, for example, reports bombers engaging him up to 1000 metres or so. And sometimes the engine exhausts could be detected at 800 metres.

On a good night there is still a lot of hex to hide a bomber in and even with radar aids it could take a while to find and identify a target. This was not helped by the fact that pulse width restrictions meant that air intercept radars had a minimum range and on bad nights this min-range could be larger than the visible distance to the target. Transitioning from radar guidance to a visual tally of a bomber was a huge problem for real-life night fighters.


Simplicity:
From the very start I wanted to make a simple, fast-playing game. Both Downtown and The Burning Blue were complex games that would take a good three to five hours to play. My aim now was to make Nightfighter much simpler, playable in under an hour. In part this was to have a fun, fast game that permitted the player and umpire to swap. But also it was because I felt it was a healthy exercise to try and boil a complex subject down to its essence: to focus only on those things that were important. It's good design discipline and all along the way I've had to resist the urge to throw the kitchen sink into the game. I had my testers assess the complexity of the game a few months back and the consensus was that it was a solid '4' on the GMT scale.

In the next part I'll start looking at some of the major mechanics in the game: search radar, air intercept radar and visual tallying.

You can order Nightfighter: Air Warfare in the Night Skies of World War 2 at:

http://www.gmtgames.com/p-233-nightfighter.aspx