Archive for the Intercept Category

Deterministic Pilot task

Posted in Intercept, Rules on March 5, 2020 by Anders Backman


John Boyd said that a pilot going into aerial combat must know two things: the position of the enemy and the velocity of the enemy. Given the velocity of an enemy, a pilot is able to decide what the enemy is capable of doing. When a pilot knows what maneuvers the enemy can perform, he can then decide how to counter any of the other pilot’s actions. 

Deterministic rules

In order to capture the feel of space combat being a contest of wits between two veteran commanders, like a game of chess, I have added variants of the rules where no luck is involved at all. Movement, initiative, sensors, attack, defense and damage are all governed by deterministic rules. Pages 44-45 of the rulebook hold the various deterministic rules but this blog post will focus on one particular section; the Deterministic Pilot task and initiative determination.

The Pilot default table was discussed here and these rules are somewhat similar. You look up your ships Size on a table after having modified the row used by computer pool use, Pilot skill, damage etc. The table gives you the steps of turning allowed this turn if you didn’t turn at all the previous turn. The Usable steps of turning is the value from the table minus half the number of steps you used the last turn.


Usable steps of turning

Look up modified Size, subtract used steps from last turn / 2 (round up)
Highest number of Usable steps of turning win Initiative
A ship has a certain number of steps each turn, based on ship Size, Pilot skill
and Crew damage. Subtract the used number of steps / 2 from the previous turn
(rounded up). A good way to handle this is to write down the turn number / used steps of turn for each ship, so you don’t have to remember how many steps was used the last turn.

Deterministic Pilot task 1


Untracked ships win Initiative over tracked ships as usual but higher Useable
steps of turning is used instead of the Pilot task or Pilot default.
Initiative is determined as follows (in order of priority):
1 Untracked ships have higher Initiative
2 Higher Useable steps of turning have higher Initiative
3 Higher Ship tactics have higher Initiative
4 Higher crew station have higher Initiative (Bridge > Full > Limited)
5 Break ties with player A wins on even, B on odd turns, note on DataCard.

Deterministic Pilot task 2

Pilot task result

Whenever the rules call for the Pilot task result (Very Good, Good, Fair, Miss, Bad or Very Bad) determine the degree of success or failure from the above chart. Pilot task results are used when Aerobraking, landing, ramming and docking. The Pilot task result is not used to determine initiative; for example two ships, one with 4 steps of turning to use and the other with 5  both have a Fair Pilot task result but the ship with 5 steps win over the one with 4.

The Deterministic usable steps of turning go very well together with the Deterministic hitlocation rules as these make maneuvering even more critical. Feel free to mix and match whatever Deterministic rules you like, as long as both players agree upon their use before the game starts. Although I have taken care to make them as balanced as possible there’s no guarantee that the balance will remain the same, you have been warned!

Pilot duel example

The next post will cover a mock duel between two trader captains using the deterministic pilot task presented above.

There’s only one course of action
Left for me to take
I’ve tried every switch selection
That might control this state
I think for my protection
I better make it straight
Into Ejection
Better tell Base
That I think it’s a case
For Ejection
Explode into Space
Protect my Face

Ejection – Hawkwind



Pilot default

Posted in Intercept on February 6, 2020 by Anders Backman

Bildresultat för Dogfight me 109 shot down

Pulling up into his blind spot I watched his plane grow larger and larger in my sight. But this German pilot was not content to fly straight and level. Before I could open fire his plane slewed to the right, and seeing me on his tail, he jerked back on the stick into the only defensive maneuver his plane could make. I banked my 47 over to the right and pulled back on the stick, striving to get him once more into my ring sight. The violent maneuver applied terrific G’s to my body, and I started to black out as the blood rushed from my head. Fighting every second to overcome this blackness about me, I pulled back on the stick, further and further, so that the enemy would just show at the bottom of my ring sight to allow for the correct deflection.

We were both flying in a tight circle. Just a little more and I’ll have him. Pressing the [trigger] I waited expectantly for the 109 to explode. I’ve hit his wing. A section two-feet long broke loose from the right wing as the machine gun cut like a machete through it. Too low, a little more rudder and the bullets will find his cockpit. I could see occasional strikes further up the wing, but it was too late. The 109, sensing that I was inside him on the turn, slunk into a nearby cloud. Straightening my plane, I climbed over the top of the bank, and poised on the other side, waiting for him to appear. But the 109 did not appear, and not wishing to tempt the gods of fate further, I pushed my stick forward, entered the protective cover of the clouds, and headed home.

Unknown World war 2 pilot

In Intercept no task is rolled more than the Pilot task. It affects how much your ship may turn but most importantly it also determine the Initiative or the order things are done in the game, high initiative move last and attack first and as damage is inflicted directly the losing initiative may not get a chance to fire back.

As the target number to beat is your ship Size a Pilot task roll will inevitably reveal your ship’s Size to your opponent (and your Pilot skill). For this reason Intercept gave Untracked ships an automatic task result of Fair with 4 steps of turning each turn, enough to turn in any direction without revealing the Size.

Flying really large ships such as 60 000 dTon cruiser with Size 12 and getting an automatic Fair result made them much more maneuverable when Untracked than when Tracked and some players may also feel that Tracked ships are way too unpredictable in how much one can maneuver from turn to turn because of the required Pilot task rolls every turn.

Pilot Defaults


So, what to do? In the current rulebook I have added something called Pilot defaults which list four Pilot task results, one for each turn out of four for each ship Size.

A Size 7 ship use the series 3(M) 3(M) 3(M) 3(M), which means the ship may turn 3 steps and the Pilot task result is considered a Miss for all 4 turns of each hour.

A Size 8 ship use the series 3(M) 3(M) 3(M) 2(B), which means the ship may turn 3 steps and the Pilot task result is considered a Miss for turns 1-3 but turn 4 it can only do 2 steps of turning and the Pilot result is then treated as Bad.

Note that rolling the Pilot task will on the average give you more steps and better results but may also give you worse results, the decision is up to you what to use. Ships with computer dice to use on the Pilot task roll will have even better chances of beating the Pilot default of course.

Pilot task rolls are done in A/B order as usual but each ship must now decide weather to roll a Pilot task or use Pilot default, this is true regardless if you are tracked or not. This completely replaces the untracked automatic 4 steps rule mentioned above; if you want to hide your Size you use Pilot defaults.

When two ships are equal in Size, Ship tactics and crew stations, and both tracked the following might ensue;
First turn.
Player A must decide weather to roll Pilot or use a Pilot default. Player B will then probably roll because he would automatically lose if not. On B turns the tables are turned and A player is more likely to roll.

The huge battle cruiser with its Size 12 have Pilot defaults of 2(B) 1(VB) 2(B) 1(VB) so untracked large ships are now just as slow and lumbering as when tracked. Mission accomplished!

The Deterministic rules on page 44-45 does not allow Pilot defaults, instead you always use a similar table where both Pilot skill and Computer pool dice are taken into account, as are the amount of turning you did the previous turn. Feel free to use this instead but then you need to note the number of used steps of turning each turn.

Well, that is all for now, next up will be a post on how PEN and ARM work in the 2020 rules. Carry on and remember that the speed of light limit is not just a good idea, it’s the law!

Small October update

Posted in Intercept, Rules on October 14, 2019 by Anders Backman

October update

I have made some small updates and rearrangements to the rulebook over and now they are available to downloads. That is all folks, see you next time.

Vector movement game units

Posted in Intercept, Other vector movemet systems, Rules, Science, Traveller, Vector movement on July 16, 2019 by Anders Backman

When you create your own vector movement system, as I am sure everyone does, you need to determine what map scale, turn length and acceleration units are. There is an obvious formula from school that most seem to use and but will argue for why this is wrong and why one should instead use another formula, also from school.

Plotting example


Typically one decide on the map scale first (how large will the hexes, squares, inches or centimeters be?). Deciding on scale is mainly about what you want in your maps, do you want planets to be one unit or less in scale? Do want to show Earth and the moon on the same map? Do you want to fit the inner solar system on your map, like Triplanetary? And so on.

Some examples:

  • Intercept 10 000 km per square, 15 minute turns, 1G per square.
  • Intercept large scale 100 000 km per square, 60 minute turns, 1G per square.
  • Traveller LBB 1000 km per inch, 5 minute turns, 1G per inch.
  • Mayday by GDW 300 000 km per hex, 100 minute turns, 1G per hex.
  • Triplanetary ~10 million km per hex, 1 day per turn, ? G per hex.

Intercept let you play using two different scales and switch back and forth as you like, there’s even a smaller scale in the works if I can iron out the problems with planets taking up large parts of the map, that scale will be 1 000 km, 4 minute turns and 1G per square as usual.

We will later calculate what acceleration Triplanetary is likely using based on the distance and time scales and formulas learned.


High school math teaches us two formulas for determining distance traveled, one for when applying constant acceleration from a standstill and another when having constant speed.

The two formulas are:

Formula one and two

Notice how formula 2b is the same as formula 1 but without the 1/2 multiplier. Distances traveled become twice as far in formula 2 so one of them must be wrong, right?

Not so fast! The formula from high school actually looks like this:

Formuila one with prior speed

Formula (3) also take the velocity from the previous turn into account (the v0 term). As v equals a multiplied by t we get our beloved formula (2b) as the first term, or something similar at least.Why is the first term twice as big as the second term? Well, the the first term assumes the speed is constant through the time segment t while the second term treat is as increasing, the distance traveled can be seen as areas in graphs with speed plotted versus time, like this:

Formula and area

If we use formula (3) to determine total distance traveled while t keeping t as the turn length and v as v (n-1) where n is the number of turns we’ll see that as the number of turns increase the grey area will more and more resemble a rectangle (the triangle of the last turn will contribute less and less of a fraction of distance traveled).

Formula graph

The grey area is the distance traveled. If we call one rectangle as 1.0 and one triangle as 0.5 we get the following distances:

  • Turn 1: 1 triangle plus 0 rectangles = 0.5
  • Turn 2: 2 triangles plus 1 rectangle = 2.0
  • Turn 3: 3 triangles plus 3 rectangles = 4.5
  • Turn 4: 4 triangles plus 6 rectangles = 8.0

and so forth…

You see that as the number of turns increases the number of rectangles increases faster than the number of triangles. So, as the number of turns increase the the number of rectangles will outstrip the number of triangles.

In the vector movement systems of Triplanetary, Mayday, Traveller, Intercept etc we use a vector that both represent velocity and acceleration however. So we either decide that one unit length should be correct for acceleration from a standstill but wrong for drifting or accelerating with a prior velocity (1) or we decide that one unit length should be correct for drifting and approach correct when handling prior velocity (2).

Too much theoretical bullshit you say? OK, let’s do a practical example.

Let’s travel from a standstill to the moon as see which of formula (1) or (2) most closely fit (3). We ignore braking at the moon just go to the moon as fast as possible. The average distance between the earth and the moon is 380 000 km so let’s go with that.

Units for formula (1)

  • A = 10 m/s^2
  • T = 1000 s
  • S = 5000 km

Distance earth – moon will be 76 squares.

Traveling 76 squares with 1 unit acceleration will be

1+2+3+4+5+6+7+8+9+10+11+12 = 78 units after 12 turns (12 000 s) = 3 h 20 m
(We overshot the moon by 2 squares but this is the closest we could get)

Units for formula (2)

  • A = 10 m/s^2
  • T = 1000 s
  • S = 5000 km

Distance earth – moon will be 38 squares.

1+2+3+4+5+6+7+8+9+10 = 46 units after 10 turns (10 000 s) = 2 h 45 m
(We overshot the moon by 8 squares but this is the closest we could get)

The correct value using formula (3) and setting v0 to zero is (8 718 s) = 2 h 25 m


Sorry about the long winded explanation but for some reason most vector systems get this wrong. Doesn’t matter when you play of course but say you want to travel from earth to the moon using actual mapboard movement you’d find that the travel time would not match the calculated value.

Apollo 11 50 years anniversary July 16 1969

Yes, 50 years ago today a couple of Americans started their travel from earth to the moon , certainly not under constant 1 G acceleration and they made damned sure their velocity was as close to zero as possible before they hit the moon. Apollo 11 did the trip in about half a week.