Archive for the Science fiction Category

Floater thrust

Posted in Intercept, Science fiction, Traveller, Vector movement on October 10, 2021 by Mr Backman

Belly landers and tail landers

“The ships hung in the sky in much the same way that bricks don’t.”

― Douglas Adams, The Hitchhiker’s Guide to the Galaxy


Most smaller ships in Traveller are of the belly lander variety which like the term indicate land and take-off on their belly, all of this is accomplished by the floater ability of all grav thrust vehicles great and small. When ships get into space however, the depictions of Traveller ships seem to forget about this gravity negating ability but not here in Intercept.

Belly landers should have their belly towards the planet to negate gravity while tail landers should have their tail towards the planet to negate gravity. Because Intercept is a 2D game with ships seen from their top (or bottom if rolled) we decide that belly landers simply can negate gravity to their left or right, the important thing here is that their floater thrust is 90 degrees of their thrust axis while the tail landers have floater and regular thrust co-axial.

Legal floater directions

Movement phase

Let’s go through a movement phase in Intercept to see if and when we can apply floater thrust. We’ll use a belly lander for the example but a tail lander works similarly except what facing it need to have to perform floater thrust. Note that a ship that uses floater is considered thrusting so there is no +2 DM for attacking or being attacked and the ships Signatures will be for a thrusting ship.

Floater drift after gravity

We will use compass directions in this example, we call the up direction north, down is called south, to right is east and left is west. We strongly suggest you use the same conventions when you play Intercept as left and right can be confusing when two players sit opposite each other each with their own map.

The ship is drifting 3 squares up or north and it was facing north in the last turn. Repeat the last move and mark with a thin cross, then apply gravity based on the position of the last turn and mark with a cross. This is the ships Drift and if the ship doesn’t use any thrust, regular or floater, this is where it will end up for the turn.

Now the pilot Pilot should decide if he wants to and is able to  use Floater to negate the gravity pull. Floaters can only negate gravity so it can only move the drift marker back to the light pre-gravity cross. Whether the ship can do it or not depend on the facing from the last turn.

Floater belly lander float directions

A belly-lander facing north can negate gravity to east or west, gravity was pulling to the east so the floater can only thrust back to west making the course a straight line again. So there, the Drift and gravity phase of movement is over, the ship could now turn and thrust (and also aerobrake if adjacent to the planet). The captain decides to neither turn nor thrust here, but that doesn’t mean that it is drifting, as previously stated using floater is considered thrust.

Floater drift after gravity2

 In this turn the ship is still facing north and still has a vector of 3 squares north. The ships last turn was in the north-west gravity arc which will pull the drift one square south-east as shown. Let’s see if the pilot can use his floater again this turn.

Floater belly lander float directions2

No, the gravity pull of south-east cannot be negated by any the floater thrust arrows, the ship should have turned to face north-east in the last turn if it wanted to use floater this turn. We mark the ship with a ring as it is actually drifting this turn. 

Floater drift after gravity3

Using floater thrust is rarely worth the effort but can be used in certain situations, especially for ships such as the subsidized merchants. Subsidized merchants, the lower left part of the topmost image, uses reaction-mass guzzling fusion thrusters for thrust i space, in atmosphere the fusion rocket switches to air breathing with a considerably lower fuel use. Subsidized merchants have Floater grav drives that can only negate gravity but that can be used to reduce fuel consumption from thrust at the cost of longer times to jump. Thrust away from the planet (costing no fuel if the planet has an atmosphere thanks to air breathing) and then turning to keep the side towards the planet (the belly in reality). Then they’ll simply Drift away from the planet gliding gracefully out to the jump point.

Floater, grav and impulse drives

Floater thrusters is the first gravity technology and it appear at Tech Level 10. They can only negate gravity and will work exactly as if it was a rocket for those inside the vehicle. The subsidized merchant is a prime example but there are also some grav vehicles with Floater to negate gravity and some other propulsion means such as propellers, ducted fans or jet engines. Floaters are rated in in how much mass they can negate gravity of, a 10 ton Floater on a ship massing 10 ton or less will negate 100% gravity regardless of gravity strength (this help the referee a tremendously as she no longer need to design vehicles for each strength of gravity).

Grav thrusters appears at Tech level 11 and create thrust proportional to gravity. These are you regular sci-fi grav vehicles. They can reach orbit and beyond but get more and more sluggish as gravity diminish the farther out they gp. Also note that regular grav vehicles rarely have the instrumentation to actually match something in orbit, see this post on reaching orbit in an air/raft. Grav thrusters have have built in Floaters too.

Impulse drives finally appear at TL 12 and above and can create thrust regardless of local gravity. They are the kind of drives most Traveller ships use, except for the Subsidized merchant mentioned above and some Vargr ships which uses the high thrust ratings of fusion drives to make high G corsairs with limited endurance.

So, now you know how ships and vehicles of scifi manage to hang in midair, just like bricks don’t. That is all folks, until next time…

Fighters in Intercept

Posted in Intercept, Rules, Science fiction on November 23, 2013 by Mr Backman

Vulnerable? Nah, sitting strapped atop a fusion rocket with only three centimeters of glassteel for canopy, taking on huge warships at fist-fighting range, no, that does not make me feel vulnerable, why? I just trim my moustache, whistle a few bars of the Imperial march and tell my buddies to ‘smoke me a kipper, I’ll be back for breakfast’.

So, young lovely, what are you doing after this dreadful yawn of a ball? Meet me at the Areobrake salute and I’ll buy you a drink.

Single crew fighters have been a standard troupe in Science Fiction but their usefulness have been questioned on Atomic Rocket and other hard SF sites. This article will argue for their existence from an Intercept perspective; why would one build small fighters in Intercept except for coolness and Traveller canon?

Fighters have one thing going for them; their Size. Small ships are hard to hit and tend to win the Initiative. Fighters are small enough to allow the Pilot and Ship tactician being the same person so grouping them together under the command of an ace Pilot / Tactician makes perfect sense, remember that guns of the same kind can be grouped into batteries even if they sit on different ships as long as they are all under the same commander. Capital ships can easily kill a fighter with a single shot but only if they can hit them. Grouping together lots of low powered weapons will steal precious surface area from larger weapons and the fighters will probably maneuver themselves into the cracks between firing arcs or even the blind aft centerline were they can attack with impunity. Large fighter groups can also work as a mobile anti missile system defending their motherships.

What then can the capital ship do in defense? They can build really thick hulls and rely on internal sensors alone (neutrino and mass) but a more viable solution is to have their own fighters engaging the enemy and protecting their aft centerline.

So, we have dashing and brave squadron leaders with excellent pilot and ship tactics skills dogfighting around the capital ships and that one, ex farm boy, young pilot can happen to score a cascading damage hit through the radiators of that huge, space station like, enemy ship, a hit that might eventually, through cascading damage, blow up the entire ship, with huge amounts of sheer luck (or is it Luke?). You can download an example fighter design (among other ships) at the downloads page.

Yes, the single-seater fighter ship is very much alive and well in Intercept!

Goodbye Vectors, hello April fools!

Posted in Boardgames, Films and TV, Intercept, Rules, Science fiction, Vector movement on April 1, 2013 by Mr Backman

I have recently come to the conclusion that not many people find Vector movement to be neccessary or even preferrable for a space combat system. Less and less people read actual Science Fiction, ie something not based on films, games or comics, so it gets harder and harder to sell the idea that vector movement is how spaceships move and they should therefore like it.

So, today I have decided to go with the flow and embrace the more cinematic style of space combat. Battles from SciFi universes such as Star Wars and Star Trek could run battles using the Intercept rules with double blind hidden movement, fully deterministic, logarithmic values etc without foregoing their popular cinematic movement style.

What then IS a proper cinematic movement system? I have decided to break down the two most popular settings, Star wars and Star Trek and see how we could emulate that in our game:

Star Trek

I have complained about the various scientific inaccuracies of Star Trek but failed to mention its strengths; Star Trek shows us a positive and humanistic view of the future. Enterprise and its brave crew aren’t on a mission to subjugate planets and aliens, they are there to explore and help and always keeping in mind the prime directive, never interfere destructively. Star Trek also gave us the female perspective with Lt Uhura as a near equal on the bridge yet still able to express her female side with her short hemlines and sensuality. Star Trek also stress how important emotions are to us humans, always trumping cold logic. Kirk wins by persevering over staggering odds despite Spocks logic telling him his efforts are futile. We can learn something from this as politics is often too much ruled by logic and hard facts ignoring the very thing that makes us unique in the world; our emtions.

Star Trek ships use subspace warpdrives to quickly move from system to system. There are cases when they have battled during warp but this is too different to regular combat and will be covered in a future post. Star Trek ships always move with the nose in their forward direction. Some kind of drag seems to be in effect as ships with damaged impulse drives tend to slow down and ultimately stop. Top speed vary little between capital ships as is eveident from their inability to outrun each other. The Wrath of Kahn end battle has Kirk using thick clouds of a Nebula to turn the tides on Kahn instead of merely outrun him. The ability to turn seem more or less the same, regardless of speed and ship size.

Star Wars

I have often critizesed Star Wars for being a fantasy story disguised as Science Fiction. This may or may not be true as all Science Fiction is really nothing but some other literary genre in disguise (Blade runner is crime fiction, Barbarella and Zardoz is soft-porn etc). What Star Wars did to Science Fiction is to put religion as center stage. Many know me as a fervent atheist but what is atheism exactly, if nothing but a different faith? All humans need to believe in something and to hold something higher than himself, to serve and strive for. Star Wars also show us that not everything can be settled by a majority vote; there are issues and questions that must be handled by wise and spiritual elites, far better at judging changes in tradition and culture. Jedi knights show us a solution to the problems facing todays democracies; the lack of spirituality and disregard for tradition.

Star Wars ship jump between solar systems very much like the Traveller jump drives but no combat seems to occur while in jump space. Star Wars ship seems to have vastly different top speeds depending on size where smaller ships outrun bigger ones. Star Wars ships turn slower the faster they go as is evident if one analyze the dogfights in Star Wars Episove IV.

Star Trek cinematic movement rules

Use as much of the Deterministic optional rules as possible to get the feeling of Kirk and Klingon in a battle of the minds. It is especially important to use the deterministic ruls of Initiative where the Initiative goes to the ship which ‘skipped’ more steps, see the Deterministic combat rules for details on this.

Ships should note their speed and can move to any square in their forward arc. Turning is done anywhere during movement.

All ships can turn 4 steps each turn regardless of size, -1 step if Hull or Crew has Light damage, -3 if Hull or Crew has Severe damage. No turning if Hull or Crew has Critical damage.

Ships can increase or decrease speed by Acc, top speed is 6 regardless of Size, Acc etc. Ships lacking thrust reduce speed by 1 each turn until stopped.

Star Wars cinematic movement rules

Do not use the deterministic rules as Star Wars portray battles as individual skill rolls. Give your hero characters lots of skill bonus.

Ships should note their speed and can move to any square in their forward arc. Turning is done anywhere during movement.

Ships roll Pilot tasks vs Size as usual noting the steps of turning. Reduce turning steps by one for each full multiple of Acc in speed. Ships moving at top speed cannot turn at all.

Ships can increase or decrease speed by Acc, top speed is Acc * 4. Ships lacking thrust reduce speed by 1 each turn until stopped.

Well, that is all folks, get out and enjoy this beautiful April fools day!

100 diameters limit

Posted in Rules, Science, Science fiction, Traveller on May 30, 2010 by Mr Backman

Traveller has always had the rule that hyperspace jumps should be made beyond 100 diameters of the planet, gasgiant, ship, star or nearby massive object. When some kind of reason for this is mentioned it goes along the lines of  ‘too deep within the gravity well’ or other reference to gravity. Can ships jump inside nebulae (they’d certainly be inside 100 diameters of the nebula)? How can ships jump at all when they are always inside 100 diameters of the milky way galaxy? What about jumping near black holes or neutron stars (shouldn’t the density of objects be accounted for at all)?

We all know the real reason is to force ships to actually travel in space before jumping, without such a limit the ships could just as well jump directly from the ground and not much space travelling would occur. So let us all agree that wa want some kind of rule that forces ships to fly away from planets before jumping, preferrable such a rule should behave as the 100 diameter rule for planets yet still make some scientific sense. The rule should also dismiss the cases of nebulae and galaxies so ships can jump inside these while still abiding to the rule. If the rule is based on gravity instead of some weird new invented force all the better.

Gravity then, is proportional to the mass of the object and inversely proportional to the square of the distance. Gravitational force is not the only measure of gravity, we have gravitational potential and tidal force as well. These two are effects derived out of gravity but they behave differently range wise:

  • Gravitational potential falls off as M/R, where M is the mass of the planet and R is the distance from the planet. It is a measure of the energy needed to reach the distance R.
  • Gravitational acceleration falls off as M/R^2, where M is the mass of the planet and R is the distance from the planet. It is a measure of the gravitational acceleration exerted on an object at the distance R.
  • Gravitational tidal force falls off as  M/R^3, where M is the mass of the planet and R is the distance from the planet. It measures the fall-off rate of gravitational acceleration. It is the force that causes ebb and flood on Earth as well as what causes the moon to always show the same face towards Earth.

The mass of a planet is proportional to its volume (given the same density), that means that it rises with D^3. Twice the diameter and the planet becomes 2^3 = 8 times as massive. The 100 diameter rules states that a planet twice as large must be jumped from twice as far away and as mass scales with D^3 we need something that scales as 1/R^3 and the only gravity effect that fit the bill is tidal force. Using tidal force as a limiter for when a safe jump can be performed makes a lot of sense; it is a measure of fast gravity changes near the ship. If jumdrives need a uniform gravity field to work properly the tidal force tells us how much gravity differs in different parts of the ship. If jumpdrives need to know the exact gravity pull when jumping the tidal force tell us how much error we get from our positional error. 

Safe jump distance (taught to Imperial school children to be 100 x the diameter of the object) is really calculated like this (x^(1/3) means the cubic root of x):

  • Planet safe jump Rj = 1 000 000 km x (Traveller Size / 8 ), multiply by the cube root of Earth density if you want that level of detail (Earth has density 1.0)
  • Planet safe jump Rj = 1 000 000 km x (M) ^(1/3), M is measured in Earth masses (Earth has a mass of 1.0)
  • Star safe jump Rj = 0.5 AU x (M) ^(1/3), M is the stars mass in Solar masses (Sol has a mass of 1.0)

What does all this give us? The referee can tell its players that they must travel out 100 diameters from a planet to “where the tidal force is weak enough to safely engage the jump drive”. If one wants the detail one can calculate the actual safe jump distance from any object. When scientifically versed players asked how one can jump inside the 100 diameters of the milky way the referee can tell them it is because the tidal force from the galactic centre is way too weak to cause any problems, the same goes for jumping inside nebulae.

Note: I have taken the liberty to round off figures in the formulae above, it should really be 1 280 000 km but I find one million kilometers easier to remember.

Relativistic rock? Is that a sub-genre of Space rock? You know, Hawkwind, Ufomammut and the like?