Ship Combat: The Particle Barbette

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silburnl
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Ship Combat: The Particle Barbette

Postby silburnl » Wed Jul 24, 2019 2:13 pm

In the last session of my Drinax campaign, the players ran into a small freighter who actually had some fight in him, so they got to fire the Harrier's particle barbette in anger for the first time (up to now I've ruled that a single shot across the bows was sufficient to force a surrender). I couldn't find the rules for how to apply the radiation trait at the table, which isn't surprising because they are scattered all over the place - so here's a summary of what I've found after going through my books post-session:

  1. Radiation trait (core rules p75) - gives a dose of 2D * 20 (*5 for spacecraft scale) rads to anyone close to the firer, the target or the line of fire between the two.
  2. Radiation damage (HG p13) - "This is simple to apply to the types of low tonnage ships most Travellers will be using,..."
  3. Radiation (core rules p77) - read across from the Immediate Exposure or Cumulative Exposure entry (whichever is worse) on the Radiation Effects table to determine how bad things get for the victim of a radiation attack (hint: it gets bad pretty quickly)
  4. Radiological protection #1 (HG p13) - a conventional hull reduces the rads taken by 500 (shielding doubles this protection to 1000).
  5. Radiological protection #2 (core rules p109) - a dose of anti-rad drugs reduces the damage taken by 100 rads if administered within 10 minutes of the attack.
  6. Radiological protection #3 (CSC pp10-35) - wearing protective gear can reduce damage by up to 310 rads depending upon what you have, civilian kit tops out at -185 rads (a TL14 HEnv Vacc Suit).
I'm going to assume that the Harrier's particle barbette is sufficiently well shielded that the 'close to the firer' text in item 1 does not apply to crew on the Harrier (although the prospect of dosing the PCs with 1-200 rads every now and again *is* amusing) and the implication of the 'simple to apply' text in item 2 is that anyone on a low tonnage adventurer class of ship is 'close to the target' of a particle barbette strike.

Items 4 and 6 suggest that approximately two fifths of the crew will be lucky enough to avoid rad damage (assuming they suit up for starship combat, which seems like a no brainer) and per item 5, prompt application of anti-rad meds will slightly mitigate the effects for the others, although an unlucky radiation effect roll is no joke. Passengers may well be reliant on emergency vaccuum protection however, so they will be more exposed and possibly harder to dose with anti-rads. Of course all of this only applies if a ship is hit once with a radiation weapon - multiple strikes will tend to inflict large cumulative doses, with rapid debilitation of both crew and pax (and death likely given the amount of damage rolled at the higher ends of the radiation effects table).

A ship with anti-rad shielding like the Harrier is much better placed, with crew-members only taking radiation damage 1 in 12 times (1 in 36 if they've got decent protection or a dose of anti-rads, falling to never if they are in battle-dress).

RAW don't mention aftereffects, but It seems reasonable to infer that a thoroughly irradiated target will be subject to secondary activation effects, in which case anyone on the ship should be making ongoing exposure rolls and any cargo containers looted may be 'hot' in more than the traditional sense....

Is there anything I've missed?

Regards
Luke
--
Currently running Pirates of Drinax
AnotherDilbert
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Re: Ship Combat: The Particle Barbette

Postby AnotherDilbert » Wed Jul 24, 2019 2:53 pm

silburnl wrote: Radiation damage (HG p13) - "This is simple to apply to the types of low tonnage ships most Travellers will be using,..."
Generally 4DD counts as 40D for effects, so a 4D barbette is a 40D weapon for calculating the range of the radiation damage, so the damage extends 40 m, hence the entire ship for most small ships.

silburnl wrote: Is there anything I've missed?
Not that I can see.


I tend to simplify it a bit: any Rad Shielded ship ignores Radiation damage. Any crew on unshielded ships are automatically dead after a few shots (so they generally surrender).
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Re: Ship Combat: The Particle Barbette

Postby DickTurpin » Wed Jul 24, 2019 3:47 pm

Most Traveller weapons do not create lasting radioactivity. Only neutron radiation can make other objects radioactive. Space-based particle beams weapons must use neutrons rather than protons or electrons to avoid beam scatter (interestingly, in an atmosphere the opposite is true), so it can have more long term effects. Neutron beams can knock neutrons or protons out os an atom's nucleus, leaving behind an unstable atom that will decay over time. The time required for the atom to decay can be nanoseconds, or millennia, depending on what type it is.

Since the creation of unstable atoms is random, as is the type created, there will likely be very little detectable radioactivity left after a few minutes. Any residual radiation will most likely be found in denser materials like the ship hull where there is a higher chance for a neutron to actually encounter an atom nucleus in the first place. Accordingly, the Traveller rules do not list the risk of lingering radioactivity as a side effect of particle beam use.

One situation where a GM might be justified in decreeing that there is an issue is if the ship is carrying a lot of heavy element radioactives or fission based nuclear warheads (TL 6 nukes). The results can vary from atomic explosion (very rare; let's not even go there. Especially if you are my GM), to radioactive contamination.
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Re: Ship Combat: The Particle Barbette

Postby Old School » Wed Jul 24, 2019 4:34 pm

A ship with anti-rad shielding like the Harrier
Note that the Harrier does NOT have radiation shielding, so when the Harrier decides to pick a fight with a Gazelle, that radiation damage hits both ways. Radiation is what killed the original crew of the Harrier and left it drifting in space for two centuries.

Whether or not patrol vessel, SDBs, etc. should have radiation protection is a matter of much debate. RAW, they do not, and neither does the Harrier.
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Re: Ship Combat: The Particle Barbette

Postby Sigtrygg » Wed Jul 24, 2019 5:50 pm

DickTurpin wrote:
Wed Jul 24, 2019 3:47 pm
Space-based particle beams weapons must use neutrons rather than protons or electrons to avoid beam scatter (interestingly, in an atmosphere the opposite is true), so it can have more long term effects.
Close but not quite. They don't have to be neutrons, in scientific fact they can not be, the particles are a beam of just about any neutral atoms. You ionize them, accelerate them, then neutralise them as they leave the accelerator.

http://www.projectrho.com/public_html/r ... icle_Beams

I'm not sure how you would generate a beam of neutrons and then accelerate them to near lightspeed...
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Re: Ship Combat: The Particle Barbette

Postby Putraack » Thu Jul 25, 2019 4:11 am

I think you have it all. I'd point out to your crew's targets that maybe they ought to surrender now, before they actually get zapped. My new crew was a little squicked with that weapon, and was happy to pick up a laser turret from salvage.
baithammer
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Re: Ship Combat: The Particle Barbette

Postby baithammer » Thu Jul 25, 2019 6:14 am

The radiation trait operates differently depending on scale, with ship scale having enough shielding to prevent self flashing. ( Further, the weapon is outside the hull.)

Personal scale lacks enough shielding to prevent self flashing.
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Re: Ship Combat: The Particle Barbette

Postby Moppy » Thu Jul 25, 2019 8:07 am

silburnl wrote:
Wed Jul 24, 2019 2:13 pm
Is there anything I've missed?
How do you fire a warning shot "across the bows"? It's a tightly focused beam that is invisible in space. They probably won't even notice you fired.

Harriers do not have rad shielding.

Virtual gunner sofrware will shoot back even if all crew are dead.
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Re: Ship Combat: The Particle Barbette

Postby AnotherDilbert » Thu Jul 25, 2019 9:38 am

baithammer wrote: The radiation trait operates differently depending on scale, with ship scale having enough shielding to prevent self flashing.
Ship scale weapons cause 2D×100 rads, so 200-1200 rads. A standard hull protects against 500 rads. Consequently ships do not fully prevent "self flashing".
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Re: Ship Combat: The Particle Barbette

Postby Linwood » Thu Jul 25, 2019 9:49 am

Can you fire the weapon at reduced power - “painting” the target with enough radiation to get the crew’s attention but not enough to cause damage? That might qualify as a warning shot.

Otherwise a single missile detonated at a safe distance might serve.
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Re: Ship Combat: The Particle Barbette

Postby Moppy » Thu Jul 25, 2019 10:06 am

Linwood wrote:
Thu Jul 25, 2019 9:49 am
Can you fire the weapon at reduced power - “painting” the target with enough radiation to get the crew’s attention but not enough to cause damage? That might qualify as a warning shot.

Otherwise a single missile detonated at a safe distance might serve.
By the rules, your average merchie has only radar and lidar, and wouldn't notice a low power beam hit unless you damaged something.

Some might say sensors for hull damage and radiation leak (from the fusion core?) are "present but undefined". Players might or might not know many hull points their ship has remaining, but how do the characters know?
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Re: Ship Combat: The Particle Barbette

Postby Sigtrygg » Thu Jul 25, 2019 11:23 am

The same way an Audio knows it has low tyre pressure... diagnostic sensors built into the fabric of the ship will give feedback 'in universe' to characters about the state of their ship.
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Re: Ship Combat: The Particle Barbette

Postby AnotherDilbert » Thu Jul 25, 2019 11:48 am

Moppy wrote: By the rules, your average merchie has only radar and lidar, and wouldn't notice a low power beam hit unless you damaged something.
Even humble small craft have visual, thermal, and radar sensors (Core, p151).

A barbette strike is a multi-GJ stream, and will be about as discrete as lightning. Space is never completely empty, there is tiny amounts of matter in the vacuum that will react and be noticeable when hit by a massive concentrated energy stream. At a guess...
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Re: Ship Combat: The Particle Barbette

Postby Old School » Thu Jul 25, 2019 12:24 pm

AnotherDilbert wrote:
Thu Jul 25, 2019 9:38 am
baithammer wrote: The radiation trait operates differently depending on scale, with ship scale having enough shielding to prevent self flashing.
Ship scale weapons cause 2D×100 rads, so 200-1200 rads. A standard hull protects against 500 rads. Consequently ships do not fully prevent "self flashing".
So the Harrier should be rolling for self radiation damage every time it fires the barbette? Lol. Guess we can all wrap up our campaigns early.
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Re: Ship Combat: The Particle Barbette

Postby GenericSuperhero » Thu Jul 25, 2019 1:04 pm

Old School wrote:
Thu Jul 25, 2019 12:24 pm
AnotherDilbert wrote:
Thu Jul 25, 2019 9:38 am
baithammer wrote: The radiation trait operates differently depending on scale, with ship scale having enough shielding to prevent self flashing.
Ship scale weapons cause 2D×100 rads, so 200-1200 rads. A standard hull protects against 500 rads. Consequently ships do not fully prevent "self flashing".
So the Harrier should be rolling for self radiation damage every time it fires the barbette? Lol. Guess we can all wrap up our campaigns early.
I just assume that THE SHIP is the firer, so it's safe from irradiating own's crew/itself.
Common sense would be to aim the thing away from hull.
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Re: Ship Combat: The Particle Barbette

Postby Moppy » Thu Jul 25, 2019 1:15 pm

AnotherDilbert wrote:
Thu Jul 25, 2019 11:48 am
Moppy wrote: By the rules, your average merchie has only radar and lidar, and wouldn't notice a low power beam hit unless you damaged something.
Even humble small craft have visual, thermal, and radar sensors (Core, p151).
Yea I forgot about thermal. Used to just checking High Guard. Thanks for catching that.
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Re: Ship Combat: The Particle Barbette

Postby Moppy » Thu Jul 25, 2019 1:21 pm

GenericSuperhero wrote:
Thu Jul 25, 2019 1:04 pm
Old School wrote:
Thu Jul 25, 2019 12:24 pm
AnotherDilbert wrote:
Thu Jul 25, 2019 9:38 am

Ship scale weapons cause 2D×100 rads, so 200-1200 rads. A standard hull protects against 500 rads. Consequently ships do not fully prevent "self flashing".
So the Harrier should be rolling for self radiation damage every time it fires the barbette? Lol. Guess we can all wrap up our campaigns early.
I just assume that THE SHIP is the firer, so it's safe from irradiating own's crew/itself.
Common sense would be to aim the thing away from hull.
What he means is that if the beam produces radiation in a tube all around the beam, some part of that tube must also extend backwards (because that is what all around means) and therefore some part will always strike the mounting ship no matter which way the beam is pointed, unless your mount is on a stick.

However I assume that either the beam doesn't generate that radiation until it hits something, or that the weapon mount is specially shielded and the radiation can't penetrate the barrel (in any direction).
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Re: Ship Combat: The Particle Barbette

Postby AnotherDilbert » Thu Jul 25, 2019 2:06 pm

Old School wrote: So the Harrier should be rolling for self radiation damage every time it fires the barbette? Lol. Guess we can all wrap up our campaigns early.
That is what the rules say, yes:
Radiation: When a Radiation weapon is fired, anyone close to the firer, target and the line of fire in-between the two will receive 2D x 20 rads, multiplied by 5 for Spacecraft scale weapons. This effect extends from the firer, target and line of fire a distance in metres equal to the number of dice the weapon rolls for damage.
So anyone within 40 m of the line of fire receives radiation. Unless you are more than 40 m away from the barbette, which I guess is difficult on the Harrier, you should receive radiation.

Apparently part of the backstory is that the original crew killed itself this way, as you pointed out earlier:
Old School wrote:
Wed Jul 24, 2019 4:34 pm
Note that the Harrier does NOT have radiation shielding, so when the Harrier decides to pick a fight with a Gazelle, that radiation damage hits both ways. Radiation is what killed the original crew of the Harrier and left it drifting in space for two centuries.
So, you should probably invest in heavy-duty rad suits and meds, and take a bit of care when firing the barbette...
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Re: Ship Combat: The Particle Barbette

Postby Garran » Thu Jul 25, 2019 3:01 pm

AnotherDilbert wrote:
Thu Jul 25, 2019 2:06 pm
Apparently part of the backstory is that the original crew killed itself this way, as you pointed out earlier:
The radiation blast was from a drive malfunction as they jumped in. Unless they were trying to use the barbette for improvised ion propulsion, it wouldn't qualify as the cause. ;)
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Re: Ship Combat: The Particle Barbette

Postby Old School » Thu Jul 25, 2019 3:14 pm

Apparently part of the backstory is that the original crew killed itself this way, as you pointed out earlier:
That’s not at all what I said, or what the campaign books say. For someone who demands such slavish attention to the rules, you can be quite liberal interpreting my posts to fit your narrative.

While its not clear if the crew was killed outright by the drive malfunction or the ship got blasted by an enemy weapon because it was a sitting duck, there’s no indication whatsoever that the crew killed itself with its own weapon.

In YTU, getting posted to a Gazelle is a tough assignment. Its got two particle barbettes, and does not have upgraded radiation shielding. Guess that’s where the navy sends folks they don’t want to pay a pension to.

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