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…

Synthetic Intelligence playing Intercept

Posted in Computer games, Intercept, Rules with tags , on October 6, 2021 by Mr Backman

Rumor has it that SI, a Synthetic Intelligence from the Ascent group will be playing Intercept. This has gotten the investors and backers of the game anxious to get get the latest and greatest version online ahead of schedule.

Fear not dear players, this is mostly minor tweaks and don’t worry; the Floater and large scale skimming updates promised in the last post are still on schedule, over and out.

Gas giant skimming

Posted in Intercept, Rules, Traveller, Vector movement with tags , , on September 29, 2021 by Mr Backman

Dangers of skimming they say, bah!

Sure, there are dangers, plenty of ’em too. Flying inside a gas giant’s vast gravity field isn’t dangerous per se, you can orbit them forever with no danger of being sucked in, the problem is that in order to skim hydrogen we must dip into the atmosphere and have it slow us down. Speed is what keep us from falling into the gas giant and we are intentionally slowing down while being as close to its crushing atmosphere as possible.

So, we dip in as deep as we dare and let the atmosphere slow us while our scoops gulp in as much gas as possible. Then we thrust away building up speed again to avoid the huge planets cold embrace. Some make one high speed approach and hard braking, others make a series of gentler dips instead, spreading out the danger. System Defense Boats and other daredevils sometimes even slow their ships down to zero deep within the atmosphere, hovering using their grav floaters and slowly scooping gas. No matter how you go about it the risks are real and minor damage to the hull is common.

As if the skimming itself wasn’t hard enough, there is also the real risk of pirate scum picking on us when we are the most vulnerable, they are rare but they do exist.

So there should be no surprise when I tell you that we do not skim that often. The time to enter and exit the huge gravity wells of gas giants offset the cost of getting fuel for free, time is money you see, especially as you must also pay for any hull damage inflicted by the skim.

So there you go, the dangers of skimming are real but not what you think!

Gas giant maps

Gas giants are, as is evident by their very moniker, huge. They are so large so they need special maps when used where the planet take up a large chunk of the map and their gravity field cover the rest of the map. Map sheets for small and large gas giants are available in the InterceptBundle here.

There is the possibility to use the Large scale rules on pages 34-35 and use the large planet maps for large gas giants and small planet maps for the small gas giants. This won’t be covered here though, just make sure you take the scale changes into account as outlined by the rules there.


Let us say we ha a streamlined ship with 1G of thrust, a Size of 8 (100 dTon) and a Pilot skill of 2, the computer is a model 1 giving us just 1D6 dice pool. The Pilot defaults table will give us 3(Miss) for 3 steps of turning every turn and the task result will be treated as a Miss. We will use the Pilot default on our approach flight but for the aerobrake turn we’ll dare an actual Pilot task roll trying to get a better result as the damage roll depends heavily on our Pilot task result.

The ship will fly towards the gas giant ass first, brake-thrusting to keep the speed from becoming too large from gravity – maximum safe speed/drag is 4/2 for airframes and 2/1 for streamlined. Keep those numbers in mind as you approach the gas giant. Try to hit the atmosphere edge on rather than head on when entering the voluntary aerobrake squares (the light grey area bordering the planet), also make sure that your ship face in the direction it will be going to head in the next turn.

The ship in the picture is thrusting to negate gravity (each x show where it would be if it drifted that turn). In the last turn it drifted and let gravity pull it into the voluntary aerobrake zone and speed it up to a speed of 4 (4.5rounded down). The circle around the ship show that it is drifting

The next turn we’ll go through aerobrake skimming step-by-step so please pay attention. This is a good moment to tell your crew over the intercom to buckle up, things can get bumpy.

Aerobrake skimming

Aerobrake steps

We’ll follow the steps from page 25 of the rulebook in some detail here, don’t worry though as it is much easier in practice. Print out a mapsheet and doodle away.

Decide drag and determine Pilot task result

Decide drag, then roll Pilot or use Pilot default to determine the level of success and the amount of turning available this crucial turn. Rolling the Pilot task will give you a better result on the average but with the Pilot default table you know what you get. We are moving at a speed of 4 and have decided to use 2 drag to stay in the 5-6 column of the Aerobrake DAM table, more on that later.

After deciding drag we will determine our Pilot task result. Pilot default has given us 3(Miss) for all of the turns of our approach but we will try to roll the Pilot task for the aerobrake hoping to get at least a Fair result, aerobrake damage depend heavily on the Pilot task result and a Miss is just not good enough we think. Rolling may give us worse than Miss of course but we bet that fortune smiles upon us. The ship is Size 8 and our Pilot skill is 2 with 1D6 dice pool so we roll 3D6 and pick the two highest and add 2.

Pilot task is rolled against the ships Size of 8 so we roll 1, 3 and 3 and use the two 3s for a die roll of 6 with 2 added, 8 – we just barely managed to roll a Fair result! This will give us 4 steps of turning but more importantly our damage roll will be based on a Fair result instead of a Miss, more on that later.

Drift and gravity (including Floater)

Gravity will take us back into the voluntary aerobrake zone again and our speed is still 4. Let’s zoon in a bit so we can see clearer.

Turn and thrust (or Initial Split-movement)

Typically you’ll only turn here, to face in your drift direction but nothing stops you from thrusting too, you may even do the first half of Split-movement here, go crazy but don’t forget that if you hit the planet you are dead. Our facing and vector are actually perfect so we’ll leave the ship as is here.

Pop-in and Forced facing

Now the ship pop in its surface fixtures which means that Visual, IR and Radar cannot Scan later in the turn, you do get to keep your Tracked targets and any launched missiles. We’ll pop in and hope that no coward pirate sneak up on us, for new targets we’ll be completely blind this turn.

Our ship is facing in the direction of our vector so there will be no Forced facing. Try to avoid this forced facing adjustment as it will increase the risk of damage quite a lot (your ships hull will be treated as one degree worse if adjusted here.

Aerobrake (first drag and then maneuver)

We decided on a drag of 2 two so let’s do them. We will simply move the drift two squares, one at a time. In our case there are no choices but sometimes there will be two options (zag-zig or zig-zag) and the Pilot can decide which one that is preferable as long as each step moves the drift closer (and thus reducing speed).

The ship has no wings and we didn’t adjust facing so there is no Maneuver to do. If we had some maneuver to use it would still be limited by the drag used (in this case 2), so maneuver could move the drift after aerobrake up to 2 in any direction. We have zero maneuver but if not we could maneuver to any square that wasn’t greyed out in the picture. Note that brake Gs are determined by counting the squares from our position before the aerobrake to the position after drag and maneuver.

Adjust facing

Our ship is still facing in the direction of our vector so no final facing adjustment is needed, this is mostly happening when a ship also uses Maneuver. This final adjustment of facing does not affect damage, it simply turns the ship to face the direction of travel.

Roll aerobrake damage

Aerobrake damage

We came in with a speed of 4 and our aerobrake took us 2 squares from that so our brake is 2. We’ll use the 5-6 column as 4 + 2 = 6. Our ship was Streamlined so our aerobrake DAM is 3. Now it’s time to roll the actual damage.

Aerobrake damage roll

Our Pilot task roll was Fair from the Decide drag and Pilot task step and the table tell us a Fair result will be rolled using 2D6 and picking the lowest and that the location of any damage is Hull.

We roll a 2 and a 5 and use the lowest one so 2 it is. Add 2 to the 3 we got from the aerobrake DAM table, 5 on the damage table is (Scratch), one point shy of Light damage. Some scorched paint and scratches is all we got from the aerobrake, let’s get out of here!

Skimming fuel

  • Skimming will net speed x brake x 5% of its hull per 15 min
  • Hovering will net 1.25% of its hull volume per 15 min

The ship did an aerobrake of  speed 4 and drag 2 which give us 4 x 2 x 5% = 40% of the ships hull volume skimmed. This is probably far more than the actual tankage we got so we leave the gas giant with full tanks and some scratches on the hull for our efforts.

Hover skimming

Hover skimming using Floater will be dealt with in a future post, stay tuned!

Large scale maps

Skimming can also be done using the 100 000 km per square, 1 hour per turn scale. In this scale large gas giants use the large planet maps and small gas giants use small planet maps. This will also be dealt with in a future post so stay tuned for that too!

So, to finish off my diatribe about the dangers of skimming by saying that the subs, the subsidized merchant crews are the bravest and here’s why:
A fully loaded sub has enough fuel for 4 hours of continuous 1G thrust! You normally use less than half of that to get to the jump point, which means that you have a bit more than half to maneuver towards the gas giant. What is even worse is that when fully loaded a sub’s Floater is only capable of negating about 60% of gravity, yeah, that is why they have those wings; to assist in takeoff when the Floater alone cannot do the job, and these guys sure need to turn every dime as their sponsors take half of what they earn.

I dare you to find a single subs skipper that has ever skimmed a gas giant fully loaded!

Avoiding heat worked example

Posted in Intercept with tags , , , on January 31, 2021 by Mr Backman

The players consist of a recently recruited crew aboard the SDB Bigfoot in the Mertactor system of the Spinward marches. Mertactor lies at the edge of the Imperium and the Sword worlds federation just a dozen parsecs coreward, with the Fifth frontier war ended 5 years ago the tensions run high. The players are ordered to travel from the main world of the Mertactor system (unimaginatively named Mertactor) to the planet Ember orbiting closer to the star. This will be a worked example using the system travel maps and the heat damage system, the maps and rulebook can be found here.

Mertactor Traveller map

Mertactor system

The star of Mertactor runs slightly  hotter and brighter than our sun so the hospitable zone is further out. For the purposes of this example we assume the system consist of these planets:

  • Orbit 1 (0.4 AU) Heat +3 (Mertactor 1), a semi molten asteroid
  • Orbit 2 (0.7 AU) Heat +2 Ember, like Mercury, destination
  • Orbit 3 (1.0 AU) Heat +1 Penelope, like Mars but much hotter
  • Orbit 4 (1.6 AU) No heat Mertactor, the main world, starting point
  • Orbit 5 (2.8 AU) No heat (Mertactor 5), uninhabited asteroid belt

Mertactor inner system

Flying route

The referee show the players were the planets are on the system travel map (we use the inner system travel map with each square being 0.1 AU and each turn is 12 hours, 2 turns per day). It is time to start planning the trip. The crew debate whether flying straight towards Ember as fast as possible or avoiding the heat from the sun is their best option.

The pilot and tacticians argue for flying in a straight line, accelerating half the time turning around and decelerating the other half, the way system travel is depicted in Traveller. The repair crew veto against this however saying she don’t think the command will be very happy if they damage the ship getting there . The pilot counters by saying that these repairs can be done en route. She counters with “I’m not going out on the hull while we are pulling 3G and give my ass cancer from the solar wind!”

After some debate the pilot start plotting a route that will minimize the time the ship is inside orbit 3 to reduce the risk of heat damage.

Mertactor plotted route

The plotted route

The plotted route will bring them to Ember in 5 days and 12 hours and only 1 day (two 12 hour turns ) will be inside orbit 3, the last turn will be either landed on the planet or staying in its shadow. The pilot is pretty pleased with himself but the last segment parts of the trip could probably be improved (can you do better?).

Turn 9 will take them inside orbit 3, 4 days and 12 hours into the trip. Turn 10, 5 days into the trip will bring them on orbit 2 at high speed so they’ll need another turn to slow down to zero. This is the way you land on planets; move your ship onto the planet (you have not yet landed) and on the next turn thrust have your ship on the planet two turns in a row (you have now landed). If you move onto a planet and won’t slow down to zero the next you won’t crash on the planet as the system travel map squares are much much larger than the planet, there is plenty of room by the sides (the inner system map we use have 15 million km squares but a large planet like Earth is ~10 000 km in diameter and even a large gas giant is ‘merely’ ~100 000 km in diameter).

So, shall we roll for heat damage then, for turn 9 and 10 but not 11 as that turn have them landing on Ember itself and the recruits had enough sense to land on its dark side where the entire planet protect them from the sun.

Mertactor plot rolling heat damage

Heat damage

On turn 9, 4 days and 12 hours into the flight, we go inside orbit 3 and might take heat damage. Actually staying on the orbit line itself is also considered to be inside the orbit, this makes perfect sense as the planet themselves are ‘on’ the orbit track’ and should be included for heat and sun factor considerations.

Can we do anything to reduce heat damage? There are two ways to reduce heat, Sunstance or power radiators and we’ll look at both them in turn.


The ship must be streamlined or airframed to adopt the Sunstance, ‘normal’ or open frame hulls may not. Sunstance consist of the ship facing the sun and be popped in (which means you cannot scan using Visual, IR or Radar and you cannot attack with your weapons, you will keep your tracked targets if any and you can still control already launched missiles except attacking with them). The argument why this works is that a streamlined or airframed ship is built with a small frontal cross section reducing the amount of heat transferred from the sun.

  • Sunstance modify Heat by -1

The Dragon class SDB is streamlined and their thrust makes them face towards the sun so if they pop in their sensors and weapons they can do this. The crew decide they are far enough from Ember to risk popping in their sensors and going blind (2 squares or 30 million km, nearly 80 times the distance from Earth to the moon). They wouldn’t see much even if they tried (and were much closer) as they would stare straight into the sun with their sensors if they did.

The SDB will use Sunstance on turn 9 but not turn 10 and they won’t face the sun that turn.

Powered off radiators out

Powerplants generate huge amounts of power which must be bled off into space or the ship would melt and the crew would fry. The more power per volume of ship the less protected the radiators can be, this is classified into three categories of radiators; protected, vulnerable or fragile. When a ship power down the powerplant they pop in the radiators to make it less vulnerable but if a ship power off their plant but keep its radiators extended they can use the radiators to cool the ship from Heat.

  • Protected radiators modify Heat by -1
  • Vulnerable radiators modify Heat by -1
  • Fragile radiators modify Heat by -2

The Broadsword class SDB has a huge powerplant and its radiators are fragile. The problem is that the ship uses powered thrust so they cannot thrust and use their radiators to bleed off heat at the same time, when the powerplant is on the radiators are fully occupied with shedding the heat generated by the powerplant itself.

The SDB won’t cool using Powered off radiators out as they need power to thrust.

Rolling heat damage

Rolling heat damage

One should only roll heat damage if the ship is in sunshine (not landed on the Darkside of a planet or asteroid and not in the shadow column of a planet or asteroid) and the orbit modifier is +1 or more (and thus the Sunfactor is 7 or higher). The damage is rolled at the end of the turn and is only affected by the ships state at the end of the turn. This means that even if the ship did some fancy turning after thrusting trickery, as long as it end up popped-in and facing the sun the Sunstance modifier apply.

Where the heat damage occur, if any, depends on in what direction the ship is facing: If it faces towards the sun roll 2D6 and use the lowest, if the ship is facing away from the sun roll 2D6 and use the highest, in all other cases simply roll 1D6 for location.

  • 1 Hull Mechanical repair from outside the ship
  • 2 Crew Mechanical repair from inside the ship
  • 3 Core Electronic repair from inside the ship
  • 4 Surface Electronic repair from outside the ship
  • 5 Power Engineer repair from inside the ship
  • 6 Power Engineer repair from outside the ship

As heat damage is rolled every turn we roll the damage roll differently depending on the turn length we use. Look up the turn length on the left table and then roll with modifiers applied on the right table. 

Turn 9 heat damage

The SDB is thrusting towards the sun using Sunstance. As the ship is facing the sun hit location is rolled using 2D6 and using the lowest.

SDB roll a 1 and 6 and use the 1, a Hull hit.

We have a Heat modifier of +1 from orbit 3 and -1 from Sunstance. The turn length is 12 hours so we roll 2D6 and use the highest , a result of 6 uses exploding dice but no matter how many 6s that came up in the original roll, you still roll exploding dice by rolling 1D6 and add the result divided by 2 rounded down, keep rolling if you got a 6.

SDB roll a 3 and a 5 so they use 5. The modifier was +1 -1 so the result is 5. Scratch damage to the Hull.

Turn 10 heat damage

The SDB is thrusting onto the planet but it won’t be considered landed or in shadow until after the next turn. The ship does not face the sun so the Sunstance does not apply, the good thing is that this means they can pop-out their sensors and weapons again.

The SDB isn’t thrusting towards the sun and neither is it thrusting away from the sun, hitlocation is simply rolled by a 1D6.

SDB roll a 3, a Surface location hit.

We have a Heat modifier of +2 from orbit 2 now and no modifier for Sunstance. We roll 3D6 again and use the highest.

SDB roll a 6 and 5 so they use 6. A 6 means exploding dice, they roll a 4 which adds 2 to the die roll. A die roll of 8 with a modifier of +2 is 10, Severe damage to the Surface location!

After this the SDB is safe in the shadow of Ember and the repair crew is setting out to Jury-rig or repair the Surface location, the scratch damage on the Hull has no effect yet so it’s ignored.


If you look carefully at the plotted course you’ll notice a mistake I deliberately put there, the fact that turn 9 didn’t thrust at all! This means they could have powered down their powerplant too and probably avoided the Hull Scratch damage it got despite the Sunstance. I put it there as a hint for the apt reader to come up with a better route.

It is actually possible to do an approach using both Sunstance and powered own radiators out for the two damage rolls. See if you can solve it! You could also try the hell bent for leather Traveller appoach of heading straight for the planet and taking the heat, see where that would land you.

If you can’t stand the heat, stay out of the kitchen!