Archive for the Intercept Category

Sensor rules part 2

Posted in Intercept on March 9, 2019 by Anders Backman

What is this Marre-red maneuver Sir?

It was invented by a rather colourful pirate called Mauricius Redondo way back and is used when you come out of the sun and assume your enemy is hiding in the planetary shadow. You approach the planet building up quite some speed, say 30 to 50 klicks a second, and drift as you pass above or below the planet with your powerplant off. Keep drifting ’til you think you passed the enemy the power up the reactor and start braking. You are now ‘south’ of your opponent, in the planet shadow with your enemy to sun-ward yet no risk of any sun-blinding. Then you take him out son.

Sensors part 1 skipped the rules on how planets and asteroids may affect scans, this post is going to remedy that, first with the actual rules and then some examples on how this work in practice. The following blog posts deal with the the different sensor types and how to avoid being detected by them.

Planet Line Of Sight (LOS)

Planets block line of sight, it’s quite obvious; just look down at the ground at night and notice that you cannot see any stars.

Ships far from a planet cannot see targets on the opposite side of the planet if they are near the planet. Ships near a planet cannot see targets on the opposite side of the planet, regardless of how far they are, and ships scanning for targets near a planet cannot see targets if they are opposite the planet regardless of how far away they are.

Planets and asteroid columns

Shadow column

Planets cast long shadows where ships can hide. The column below a planet, 1 square wide for Small planets, 3 squares wide for Large planets, is called the Shadow column. Ships and missiles in the Shadow column treat the Sunfactor as 0 instead of its normal value (usually 6), no other signatures are affected by planetary shadows. Ships in shadow also ignore Sunglare.

Planet LOS sectors

Planets also block Line Of Sight (LOS) of course, ships on one side of the planet won’t see and won’t be seen by ships on the other side. Planets have sectors that delineate who can see whom, near sectors that are simply the 8 arcs of the gravity well, and far sectors that extend the gravity arc all the way out to the edge of the map. If your ship is inside a gravity well the opposite near & far sector are blocked. If your ship is outside of the gravity well but your scan touches the gravity well the opposite near sector is blocked. Planet LOS is symmetric so a ship cannot see a someone that cannot also seem them. Look at the pictures for the near and far sectors of planets, small and large.

So, how does this work in practice? The scanner has placed a Scan somewhere and it’s up to the target, to make sure it is a legit Scan. This is done by the target asking the scanner a few simple questions and act upon the answers.

Does the Scan touch your ships Sunglare?

  • Ships in shadow ignore Sunglare

If the scan touches your Sunglare column and you are not in shadow you say yes and reduce the scan strength of your scan by Sunfactor (typically 6). If the scan does not touch your Sunglare column or your ship is in shadow you answer no and leave the scan as it was. This question is always asked.

Does a planet block parts of your Scan?

  • If scanner and scan is outside of gravity ignore Planet LOS
  • Near sector block opposite near and far sectors
  • Far sector block opposite near sector only

Your opponent now asks you if the planet blocks part of your scan.

If your ship is inside the gravity well (a near sector) the opposite near and far sectors are blocked. If your scan touches any of the blocked sectors you must tell your opponent what is blocked of the scan, if your scan doesn’t touch the blocked sectors you tell him nothing.

If your ship is in a far sector the opposite near sector only is blocked. If your scan touches that blocked sector you must tell your opponent what is blocked, if your scan doesn’t touch the sector you tell him nothing.

Planetary LOS examples

The scanner simply places his Scan somewhere calculates its strength based on Sensor + Scan modifiers. The target of the Scan then ask a series of questions which may lower the Scan or make certain parts of it ignored. Scans are done in reverse Initiative order.

Scan 1

A has his ship located in 1 and decides to do a 1 box Scan in box B4. His Sensor is +2 and the scan modifier for a 1 box scan is -1.
Player A ”I have a visual scan, strength +1, one box large, in box B4.”
Player B ”Does your Scan touch your ships Sunglare column?”
Player A ”Yes, my Scan touches my Sunglare, dammit!”
Player B ”Is your scan from or does it touch a gravity well?”
Player A ”No, it’s not from gravity and you can see it doesn’t touch it”
The scanner grudgingly admits that the Scan does touch his Sunglare column so the target reduce his Scan strength by -6 to an abysmal -5. If the target was not inside the Scan he would say Nothing, if inside the Scan but with a Signal of -1 the target would still say Nothing, if the Signal was 0+ it would be a Contact so the target would tell its position and what Signature(s) that gave 0+ Signal, the scanner would then probably do a Sense task to try to get a Tracked result on the target. The target player has also learned that the scanner’s ship is somewhere below the Scan, thank’s to the Sunglare.

I have colored the entire Scan 1 orange because of the Sunglare strength reduction, the Scan is still valid but very weak. Don’t stare into the sun.

Scan 2

Player A has moved his ship into position 2 and decide to do a huge 3×3 box scan centered around E1. The scan modifier for a 3×3 scan is -3 so his with his +2 Sensor the Scan strength is -1.
Player A ”I have a Visual Scan strength -1 three by three boxes in box E1.”
Player B ”Does your Scan touch your ships Sunglare column?”
Player A ”No it doesn’t. I have learned my lesson”
Player B ”Is your scan from or does it touch a gravity well?”
Player A ”Eh, yes it is”
Player B ”OK does the planet block any of your scan, what sectors if so?”
Player A ”The northeast near and far sector”
The northeast near and far sector is colored gray in the pictures. If player B had any ships or missiles inside the parts of the scan inside northeast near and far those targets would have been ignored. The near is simply the gravity sector and far extends from that forever. The Scan touches the Sun column but as player A wasn’t scanning from the Shadow column this had no effect.

I have colored the parts of the scan that should be ignored in red.

Scan 3

Player A has drifted into position 3 with the help of gravity. He decides to do a 3×3 box Scan in E4. He figures the Shadow column will protects him from Sunglare. The Scan strength is -1.
Player A ”Visual Scan strength -1 three by three boxes in E4.”
Player B ”Does your Scan touch your ships Sunglare column?”
Player A ”No”
Player B ”Is your scan from or does it touch a gravity well?”
Player A ”Not from within, but it touches”
Player B ”OK does the planet block any of your scan, what near sector if so?”
Player A ”Near north”
The scan touches the Sunglare column but as the ship is in shadows the answer is no. The near north sector will be ignored but most of the Scan is still valid as you can see. Had his scanning ship been 3 squares to the right none of the Scan would be blocked,had the ship been one square further up it would be in the near sector (gravity well) so the entire opposite arc would be blocked, all the way to the top of the map.

I have colored the parts of the scan that should be ignored in red.

What about asteroids?

Asteroids cast shadows so you can reduce your Visual(Hull) by staying in their shadows and by staying in their shadows you may also ignore Sunglare. Asteroids are too small to offer Planet LOS blocking however but there is still a way to get LOS blocking from an asteroid; land on them. See page 26 in the rulebook.

What about shadowing?

There is this obscure trick where a ship with the same position, vector and facing of a larger ship lies in its shadow so it treats the Sunfactor as 0. This is called shadowing and and can be done with friendly ships as well as enemies. Sunglare does still apply when being in shadows this way however. Shadowing enemy vessels is a good way to stay undetected as ships rarely scan their own position.

Be cool and stay in the shadows until next time, over and out.

Sensor rules part 1

Posted in Intercept on February 3, 2019 by Anders Backman

elite sensors

Knowing the sensor rules well will probably win you more battles than any other part of these rules, it is also what sets Intercept apart from other space combat games as it allows double-blind movement without a referee.
Using sensors resembles the old game Battleship; choose an area on the map to scan and if an enemy have targets there they may become detected. Larger scans mean lower sensitivity so if you search too large an area the enemy may go undetected despite being inside the area you scanned.

First, a brief summary of the Sensors phase of Intercept

  • Scans The scanner decides on up to two areas to scan and determine the scan strength of each, this is revealed to the target.
  • Questions The target ask questions about the scans that may reduce scan strength or ignore parts of the scans.
  • Signal The target determine the signal by adding his ships signature to the scan strength for each ship or missile volley inside the scan area. Target reveal any signals (signature + scan strength) that are 0 or higher.
  • Sense roll If the scan got at least one signal that was 0 or better the scanner may roll a Sense task trying you get a Tracked result on the target. Only one Sense roll is done and is used for all 0+ signals.

Sequence of play and procedure

Sensor scans are done one side at a time in A / B order, each side is allowed up to two scans. A / B order means that side A scans first on odd turns and B on even turns. There is a row of boxes at the bottom of the mapsheet, cross them off as each turn is performed. The leftmost uncrossed box tell you if it is an A or B turn (A means player A win Initiative ties and scans first, B means the same for player B).

The procedure is similar to the game Battleships, the scanner selects an area to scan and the opposing player, the target, reveal what’s there if anything. It’s a bit more complicated than that of course but it’s basically the same.

mapshhet legend lower


The scanner decide on a square area on the map, from a single square to 5 by 5 boxes (25 x 25 squares) covering most of a map. The area does not have to be all on the map and it doesn’t matter if the scan includes planets or asteroids, at least not yet.

Tell the opponent what scan type (Visual, IR, Radar, Neutrino or Mass), and the area of your scan (top left and bottom right corners) and show on the common map. Determine the scan strength by adding your sensors strength with the scan size modifier. Note that radar and mass scan use different scan size modifiers. Tell your opponent, the target the strength of your scan.

Note that a smaller scan area gives a higher scan strength and thus a greater likelihood of detecting whatever is inside the scan area while a larger scan area and thus a lower strength will be more likely to have something inside them.

Each scan size has a maximum range which the entire scan must lie inside, larger scans have larger maximum ranges, maximum range is always five times the scan size. A 3×3 square scan has a max range of 15 squares or 3 boxes, a 2×2 box scan (10 by 10 squares) has a range of 50 squares or 10 boxes and so forth.

scan sizes

All parts of the scan must be within 5 times the size of the scan.


After the scanner has declared both of his scans it is time for the target to handle the scans, one at a time.

The target will ask a couple of questions that may reduce the strength of the scan or have parts of the scan area invalid.

Does the scan touch your ships Sunglare?

If the ship is in sunshine and your scan touches a one square thick column extending from the square just above your ship all the way towards the sun. If that is the case you answer yes and the scan strength is reduced by the Sunfactor, typically 6 is subtracted. This is the detrimental effect of your sensor looking directly at the sun.
Do not answer yes if the scan is radar or mass or if your ship is in planetary shadow (ships are never considered in planetary shadow against neutrino scans). Note that the Sunglare column does not contain your ship itself, only the column above it all the way to the top edge of the map.

Radar and mass scans ignore Sunglare questions, skip this question when using them.


There are more questions to be asked by the target to the scanner if the map has planets or asteroids on it but it will do for now. Sensor rules part 2 will handle Sun/Shadow columns and planet LOS in detail.


Signal is what you actually end up seeing on your screens; Nothing, Contact position or a fully Tracked target good enough to shoot at. Normally you perform a Sense roll to determine what you get but if the Signal is 12 or higher you automatically get a Tracked result, no Sense roll is needed for that.
Nothing Signal of -1 or lower. The target don’t tell you anything at all, not even if anything was there or not, nothing is nothing.
Contact Signal of 0-11. Target tells you all 0+ Signatures; the Signature value and the type, Visual(Hull) or Visual(Thrust) for Visual scan for example. Roll a Sense task to determine if you got a Tracked result.
Tracked means the target tell you everything about its ship, its position, vector, facing, if it has rolled etc. Target also tell you damage status, and all capabilities of the ship, basically everything on the datacard. Tracked ships move in the open on the common map before any untracked ships. Tracked status remain from turn to turn with no need for new Scans. Tracked ships launching missiles or ships will have them tracked too.

Sense roll

If the target tell you that you got a 0+ Signal the scan has given you something, you know something is there and all Signature(s) that gave 0+ Signal. Roll a Sense task to try to get a Position or a Tracked result.

Lost Tracking

A ship can lose track of a target under certain circumstances. Losing track means the target goes back to hidden movement and the tracker need to re-track the ship again in order to attack or defend against it. Every ships that can track must lose tracking for tracking to be lost, we simply assume that all ships of a side share tracking data between them. The reasons for Lost tracking are the following:

  • Target in the aft centerline of a tracker that is thrusting
  • Popped in loses all tracked targets* and all launched missiles.
  • Target blocked from tracker by planetary LOS
  • Tracker has Surface** location Critical+ damaged or Surface** has Stun
  • Tracker has crew Critical+ damaged or Crew is stunned
  • Target beyond max range as given by the Max tracked table in the rulebook.
    *Popped in has no effect on Neutrino or Mass sensor tracks
    **Core location for Neutrino or Mass sensors

Tips and tricks

The following blog posts deal with the the different sensor types and how to avoid being detected by them.


Posted in Design system, Intercept, Rules, Traveller on January 8, 2019 by Anders Backman

Falling off the hull

I recently learned that Dropbox have changed how direct download links works so it became really inconvenient for you to download stuff from me (they tried to get you to register at DropBox and yadda yadda). Anyhow, I have fixed all the download links so you just click on the link and save, just the way it was intended, sorry about the inconvenience.

So, just go to the Downloads page and click click on what you want.

PS I have updated the rulebook with a brief combat example on page 13, and some other small updates here and there DS

Intercept maps

Posted in Intercept, Rules on January 8, 2019 by Anders Backman


What is this Marre-red maneuver Sir?

It was invented by a rather colourful pirate named Mauricio Redondo way back and is used when you come out of the sun and assume your enemy is hiding in the planetary shadow. You approach the planet building up quite some speed, say 30 to 50 clicks a second, and drift as you pass above or below the planet with your powerplant off. Keep drifting ’til you think you passed the enemy then power up the reactor and start braking hard. You are now ‘south’ of your opponent facing him, in the planet shadow with your enemy to sun-ward yet no risk of any sun-blinding. Then you take him out son.


Intercept comes with a bunch of ready-made maps, empty, with a small or large planet or our beloved Earth and Luna system. Aside from the grid squares and boxes there are some features that might not be that obvious. This little post will teach you what they are and how to use them. Oh, and if anyone want a custom map with planets and asteroids give me a message here on the blog and I’ll add them.

Map coordinates

The Intercept map consist of individual squares and larger boxes, each box holding five by five squares, each box has a column letter and a row number to help identify which box you mean, individual squares within a box are numbered left to right and then top to bottom. The top left square of the top left box is A1-1-1 for example and the top right square of the third box on the second row of boxes is C3-5-1.

map coordinates

The top left box of each mapsheet has the columns and rows numbered for you.

Note that the rightmost column of boxes is labeled G/A and the lowest two rows are labeled 10/1 and 11/2. If you wish to play on an area larger than a single mapsheet the rightmost column form the first column of the next sheet and the lower two rows for m the first and second of the sheet below. This overlap is there to simplify maneuvering straddling the two sheets. Note that playing on more than one sheet complicates the game quite a bit so don’t do it unless you feel like it is really needed. Simply stating that ships flying outside the sheet are lost works fine too and is much simpler.

The box G/A 10/1 also has the columns and rows numbered for you, this is to help you remember that this box might be the top left box of the next sheet to the right and down.


The sun is always shining from the top of the mapsheet as indicated by an arrow. To the left of the arrow there’s a box where you write the actual Sunfactor used in the scenario. The Sunfactor is 6 for Earth & Luna or any planet in the biozone. Each orbit outside of the biozone and the Sunfactor goes down by 1, down to 0 and for each orbit inside the biozone increase the Sunfactor by 1, Mars is 5, Venus 7 and Mercury 8 for example. Sunfactor 9 or above will be hot enough for the ships to require special rules outside of the scope of this little blog post, stay tuned.

If you have detailed information about the star system you play in, specifically the relative luminosity of the central star (the Sun has 1.0) and the orbit radius in AU (Earth has radius 1.0) use this formula (Round to the nearest whole number but never below 0):

Sunfactor = 6 – 4 * Log10( L / R )

L = Luminosity, R = Orbit radius in AU

Turn number and A/B order

Sensor scans are done in A/B order and the final Initiative tie breaker is also done inA/B.  A/B order means that side A scans first and wins initiative ties on odd turns and B on even turns. There is a row of boxes at the bottom of the mapsheet, cross them off as each turn is performed. The leftmost uncrossed box tell you if it is an A or B turn.

mapsheet legend lower

Fractional thrust etc)

Ships with factional thrust (1.33, 0.85 etc) can always thrust the integer part on any turn but the fractional part may give them +1 G to use on certain turns. This is shown on the ship DataCard but the information is also available in the turn number boxes (the 0.25+, 0.75+, 0.5+ values). Let’s say your ship has a thrust of 1.33, it will thrust 1 G at every turn but as 0.33 >= 0.25 it will thrust 2 G during the first turn of every four. The 0.85 G ship has less than 1 G of thrust so all of its thrust is fractional; 1G at the first, second and third turn but no thrust on the fourth turn of every block of four.

Map out your future – but do it in pencil. – Jon Bon Jovi

That’s all, stay cool, and in the shadows people.


November update

Posted in Intercept on October 31, 2018 by Anders Backman

Damage in Intercept is to simply take the weapons DAM value and subtract the targets DAB value. Use this number and add the highest of 2 D6 if a Very Good hit, 1 D6 if a Good hit and the lowest of 2 D6 if a Fair hit. Should be simple enough.

In order to simplify this a bit further I have precalculated DAM – DAB values for each predesigned ship in Intercept bundle and Designs. During play all you need is to determine your weapons DAM value and add the die roll to it as above, the damage result can simply be read from the damage table on each ship design.

Precalculated damage table

This damage table* tells us that we need to roll 23 or more to at least get a Scratch hit. A damage roll of 35 or more will destroy the ship if it was a Hull hit, otherwise it will destroy that location and by pass on damage cause Critical hit. A damage roll if 38+ will utterly destroy the ship wherever it hits.

Before checking what damage our damage roll caused we should check the box below the damage table. If the hit was a Partial penetration (meaning the PEN of the weapon was less than 4 above the ARM of the target) we go down one row. If the hitlocation was Surface or Thrust we go up one level. No effect is still no effect so no row shifts apply if the hit was No effect.

Free trader weaponry

Let’s take a look at the weaponry*. It has one 10 MW laser, a sandcaster and a missile launcher in each of its two turrets. The laser has a DAM of 24 so a roll of 1-2 give Light damage, a roll of 3-5 gives Severe damage and a roll of 6 gives Critical damage.

The old way of doing damage still exists of course, take your weapons DAM and subtract the targets DAB and use that on the damage table in the rulebook; same result.

As usual I have also added a bunch of smaller edits and updates in the rulebook.

*The damage table and the weaponry come from the Free trader design available from the downloads page.

That is all folks. Happy Halloween!

Sensor types part 2

Posted in Intercept, Rules on September 25, 2018 by Anders Backman


Stars, hide your fires; Let not light see my black and deep desires – William Shakespeare, Macbeth

We’re deep in space. Corner of no and where. You take extra care. ‘Cause we’re very much alone out here – Captain Malcolm, Firefly

In art and dream may you proceed with abandon. In life may you proceed with balance and stealth – Patti Smith

Intercept have four sensor types and five types of scans (Optical sensors can scan using Visual or IR). Each scan type in Intercept (Visual, IR, Radar, Neutrino and Mass) have their own strengths and weaknesses. To get a basic a basic understanding of how the different types actually work you should read Sensors part 1.

Scan modifiers




Stay in the shadow columns of planets and asteroids or stay directly north of your target forcing him to scan with Sunglare. Have planets block the enemy scans of you if you know their location.

In shadow columns the Sun factor is 0 instead of the typical +6 but if your enemy is clever he will scan specifically in the shadow column using IR so, if approaching via the shadow column take your time and drift in with power off.

Approaching from the sun is another way of avoiding detection. Forcing your opponent to scan with Sunglare reduces his scan with the Sunfactor, typically by 6.

Avoid thrusting unless absolutely necessary, drift instead.

Don’t thrust, specially if you have fission or fusion thrusters with their huge signatures, but even impulse or floater drives normally give off the same signature as your hull in sunshine.

Planet and asteroid sun and shadow columns


Approach from the sun and force the opponent to scan with Sunglare. Use fission or fusion thrusters as little as possible. Have planets block the enemy scans of you if you know their location.

Just as for Visual scans approaching from the sun will force your opponent to scan with Sunglare and IR scans too subtract Sunfactor from the scan, typically 6. This is your only option, the shadow column won’t help your IR signature at all.

Turn off the powerplant using Silent running. Use fission or fusion thrusters as little as possible.

Silent running reduce every signature of yours except Visual. Your ship would only have IR(Hull) for IR, typically with the same low strength as your hull in shadows. Don’t use fusion and fission thrusters except when absolutely necessary, impulse and floaters are fine but you need to have the powerplant running to use them of course. Keep in mind that if your powerplant is off you need to power it up using your repair crew which on larger vessels can take a turn.



Have the planet block radar scans. Keep distance to the enemy.

Radar is rarely used except when the enemy knows they are detected. Try to keep distance to your enemy as radar falls off much faster than other sensors by range. Radar is unaffected by Sunglare so coming from the sun won’t help you.

Pop in to reduce signature. Works on any ship except Open frame ships.

Popping in will reduce the radar signature of your ship by 6 on all ships except open frame hulls whose signatures are unaffected by popping in. Note that if you pop in you can no longer scan (except with neutrino or mass sensor), you will also lose any tracks you have (once again except if you track using neutrino mass sensors) and finally you will lose any launched missiles, drifting decoys remain however.

Cloud chamber.png


Stay north of the enemy forcing him to scan with Sunglare. Neutrino sensors are always subject to Sunglare, even when in planetary shadow.

Coming from the sun forces your opponent to scan with Sunglare. Sunglare reduces the scan by Sunfactor, typically subtracting 6 from the Scan. As neutrinos can travel straight through a planet Sunglare affects scans even when a planet would normally block (sun column, shadow column questions are ignored for neutrino scans).

Turn off your powerplant using Silent running. This works with both fission and fusion reactors. Use fission and fusion thrusters as little as possible.

Neutrinos are only given off in detectable quantities from fission or fusion reactors and fission or fusion thrusters. So, turn off your powerplant using silent running and don’t use your fission and fusion thrusters. With these off your ship has no Neutrino signature at all and thus no chance of detection from neutrino scans whatsoever.

Elite Dangerous_20180624213851


Stay away from known mass sensors, their falloff is as bad as radar so range alone might save you. Coming from the sun has no effect on mass scans, they ignore Sunglare.

Mass sensors fall off much faster than regular sensors because they rely on tidal force rather than gravity directly. Try to stay away from known mass sensors is about all you can do.

Don’t use Impulse, Grav or Floater thrusters needlessly, fission and fusion thrusters work fine. Turn off floor field when drifting.

Thrusting using Impulse or Floater give off huge signatures, on par with fission or fusion thrusters for Visual and IR scans. Use them only when you absolutely must. Fission or fusion thrusters are actually fine and won’t show up on mass scans. When you are not thrusting your strongest signature comes from your floor field, turn it off when drifting. Your ship have a mass signature like a ship in sunshine when the floorfield is on and like a ship in shadow when the floorfield is off.

That’s all folks, stay cold, dark and inert.

Sensor types part 1

Posted in Intercept, Rules, Science on September 20, 2018 by Anders Backman

Planet LOS in Star Wars

Space combat takes place at incredible ranges, tens of thousands of kilometers, and unlike in the movies, you won’t see anything through your window; a nuclear detonation for sure, fission or fusion thrusters as pinpoints of light maybe, the plume of a missile just before it hits you, the blinding flash from a laser hitting your ship, but aside from that nothing…

All ships carry sensors to see things around them and this is especially true of warships. All ships will have optical sensors seeing in visual and infrared wavelengths and most will also have radar. More exotic sensors such as neutrino or gravity sensors may be carried by larger or more specialized vessels.

Visual, infrared and radar sensors are mounted on the surface of the hull and can only be used when unfolded and extended, popped out as it is called in the game. Neutrino and mass sensors sees right through the hull so they can be used whether popped out or not. This make them especially suitable for military purposes as they can be used while still protected by the ships armor.


Visual scans are done with optical telescopes collecting light from visible wavelengths.

Light sources can be light from the sun reflected from the hull. How much depends on the strength of the sunlight, the area of the reflecting hull and how reflective the hull material is.

Light can also be directly emitted by a ships thrust, either the intense light from fission or fusion rocket plumes or the much fainter glow from impulse thrusters or floaters (that magic sci-fi blue glow).

The Inverse square law

The light falls off in strength as it spreads from its source, in both dimensions, if range doubles the intensity goes down as 1/2 times 1/2 or 1/4.


Popular media usually depict space as cold but in reality the problem is the opposite, getting rid of heat is hard part and the only viable long term way of doing it is by radiating it away. Every object radiates heat, how much depends on its temperature.

Ships have optical sensors that can either look in visual wavelengths or in infrared to detect objects as they radiate heat to cool. Ships radiate enormous amounts of heat when using fission or fusion thrusters, less infrared is radiated from the power plant when running, ships also radiate a faint heat from the temperature of the hull itself.

The infrared light falls off the same way as visual light, by the square of the distance. A given ship is typically easier to detect visually than by infrared, at least when the ship is in sunlight or if the ship has a running power plant. If the ship is using fission or fusion thrusters it’s about as easy regardless of using infrared or visual scanning. What to use really depends on what you think you are trying to find, tricky.

Plotting board


Everyone is familiar with radar works; you send out radio bursts that bounce off the target and get detected as it comes back.

One problem with radar is that it falls off much faster than visual or infrared does. Radar, although invented during World War II didn’t detect the planet Venus until 1961 yet it can easily be seen by the naked eye. Doesn’t radar waves fall off by the inverse square as visual and infrared does?

Of course they do. The problem is they fall off by the inverse square both going there and coming back again, 1/r^2 going there x 1/r^2 coming back again or, 1/r^4. If this sound weird and hard to grasp think about the following analogy:

You walk at night in a forest with a flashlight in your hand. The flashlight is a powerful maglite showing you the trees out to about 30 meters.

The flashlights range depends on the power of the flashlight but also the quality and focus of the lights parabolic mirror. The light falls off going out, bounces off trees and falls off coming back again, back to your eyes, your detectors, just like a radar.

Let’s say you decide to try your car lights instead. They must be a hundred times more powerful right? And now you can see trees out to about a hundred meters, three times farther or so. Three to the fourth power (3^4) is about a hundred (81) so that terrible range fall off of radar affects flashlights and headlights the same way.


Two men in a rubber raft inspect the wall of photodetectors
of the partly filled Super-Kamiokande neutrino detector (Ars Technica)


Neutrinos are these strange subatomic ghost particles created in fission and fusion reactions. These particles really fleeting, reacting to next to nothing. Build a wall one lightyear thick and half of them still get through. How can one ever hope to detect them with something smaller than a solar system, smaller than a planet even, small enough to fit on a ship?

What you do is you amass an enormous amount of atoms, in the hope that one neutrino might interact with one of them and then surround the mass with super sensitive detectors hoping to catch that one interaction somehow. The first detectors used thousands of cubic meters of water or chlorine as the mass and after waiting a long time they got the first signal from the sun. Imagine that, it took this enormous tank lined with super sensitive detectors sitting for months to detect a single neutrino coming from this enormous fusion reactor we call the sun.

Neutrino detectors in Intercept appear at TL-11 and assumes that some breakthrough has appeared, some resonance to exploit or some other way to make the neutrino detectors much smaller and much more sensitive, still bulky but practical. Neutrinos created in fission or fusion thrusters and fission or fusion power plants are what these detectors see. As the neutrinos leave their source they spread out, just as the visible photons for the visual scans and the infrared photons for the IR scans so the fall off is the same.

Neutrino sensors can only detect fission and fusion thrusters and fission and fusion power plants. On the other hand when they can see targets on planets or right through planets as if they aren’t there at all. In fact, a ship in the planetary shadow scanning towards the sun will be affected by Sunglare as if the planet wasn’t there at all.

Gravity with Thrust


Detecting a nearby mass seems easy. Just measure its gravitational pull on you. Not so easy. Imagine you were locked inside a small box either being a hundred km above earth and falling towards it (let’s ignore air drag completely) or being a light year away in the depth of space.

How can you detect which is case it is? How can you detect how far away earth is and in what direction? In both cases the box and you would be at rest with each other, either falling freely towards earth or just drifting in interstellar space. You could peek out of the box but that would be cheating. There is one difference that you can actually measure, being near earth means you closest point, say your toe, would be pulled towards earth a tiny amount more than your furthest point, say your nose, the difference between these pulls could be measured as a very weak force and this force would grow weaker the farther away from earth you go, a light year away in deep space and you’d measure nothing at all.

This force is called the tidal force and pulls apart parts of objects in a gravity field. The ocean water closest to the moon gets pulled towards the moon relative the water on the other side causing two bulges that move as the earth rotates. Yes that is why there are two tides each 24 hours.

Tidal force falls off as 1/r^3, double the range and the tidal force is 1/2 x 1/2 x 1/2 or 1/8 the strength. This limits the range of mass sensors but on the other hand they can see right through planets and because of the 1/r^3 falloff can scan towards the sun.

Mass sensors detect the mass of a ship directly but usually they detect the much stronger emissions from the gravitic Impulse or Floaters and also any working floorfields. This means that older low tech ships lacking floorfields and relying on fusion or fission for thrust are actually the hardest to detect.

Well, that is all for now. The next article will deal with the practical use of these sensors in Intercept. How to use them effectively and how to avoid being detected by them. Keep the solar wind to yer backside folks!