Decompression and Self-sealing Hulls

[Jak Nazryth]

Just started a new Traveller Campaign with 6 enthusiastic players and it is my first time trying the new mongoose system. I ran them through a quick space fight just to have them get used to the combat system, but I had to fudge and guess some of the time. Still learning myself. Here are the main questions we had after the first test fight ship-t0-ship.

There is an option and cost for self sealing hulls in the basic ship design but I cannot find anywhere in the rules (yet) where decompression is covered.
When is a ships hull actually breached? During any hull hit or when the hull reaches 0? Are there any rules for decompression of a ship? If you don't purchase self-sealing hulls, how do you determine how hard/long it takes for characters to patch holes?
Thanks for any input!

 

[rust]

As I read and handle it, any hull hit that does damage breaches a hull.
The time to repair it, 1d6 hours per point of damage, is covered under
Repairs in the starship operations chapter of the rules. The Central Supply
Catalogue has starship hull patches for temporary repairs, but as far as I
remember does not give the time required to put such a patch in place.
I am not aware of any rules for decompression, but I am also not sure
that such rules would be necessary, it should be sufficient to treat that
part of the starship as rapidly losing atmosphere and to give the charac-
ters just enough time to get into their vac suits (clever characters get
into their suits when a combat starts).

 

[Captain Jonah]

Another fuzzy area to be sure.

As rust points out, there are hull patches for use repairing small holes.

As a rule of thumb try that while a ship has Hull left any damage it takes to external fittings do not breach the section of the ship that holds air. So sensors or drives on the external table are smashing up stuff outside of the air tight zone. A Hull hit on the other hand punches a hole in the hull and needs patching. With self sealing hulls you lose a few hours of air before the breach seals. I assume a normal ship had 30 days of air as part of its one month of life support. Hull hits on the other hand cost a day or so’s air or (15 days divided by hull number) so each point of hull costs you a fraction of your air and once your hull has gone you have lost half your air.
Once your hull is gone every hit now punches deep into the ship and any area hit on Internal damage is then considered to be open to space with no atmosphere. So a drive hit opens the engineering room to space. At this point you a talking about far more than a few hull patches and may end up with engineers in vacc suits for a few days.

If you want to be nasty about it the air loss for structural damage can be double that of hull loss meaning that you are out of air and on bottled life support by the time you are half wrecked. Multi section ships count each section separately.

Once all Hull has gone the self sealing option becomes useless but you should have a much higher reserve of air at that point and so should last longer. Ships with more than a month of life support, in cargo for example, can break out next month’s air once the battle is done.

This can leave our players, adrift, drives or power plant off line and only a few days air left as they franticly try to patch up some systems to get moving again :twisted:

 

[DFW]

A;so, a fuel hit doesn't go all the way through to the inner hull.

 

[Rikki Tikki Traveller]

Standard Practice is to put everyone in Vacc Suits (passengers to staterooms with Rescue Balls ready) and remove the air from the hull to avoid any loss of air or explosive decompression.

I make this part of the standard actions taken to prepare the ship when going to "Battle Stations".

In several Traveller novels I have read, it is also common to vacuumize (?) the ship when precipitating out of Jump Space since you don't know what the local environment is like. YMMV

 

[rust]

I make this part of the standard actions taken to prepare the ship when going to "Battle Stations".

It is also standard in most serious military science fiction novels, for example in the Honor Harrington series.

 

[Jak Nazryth]

Thanks everyone for the help.
I started playing Traveller in 1982/83 but took a long, long break from it.
I tried out the T20 rules and then GURPS, but until I moved to Dallas I didn't find many people who were interested. Now I've got 6 guys chomping at the bit to get into the campaign scenario!
I find that I keep "borrowing" rules from past systems when I need to make a snap judgment, but the more I get used to Mongoose, the smoother things will go.

Going to start a "Why are bridges so big?" thread soon, and life support ties into the question.
Thanks again guys!

 

[DFW]

and life support ties into the question.
Thanks again guys!

Considering that decks are spec'ed at 3 meters high; ceilings are probably no more than 2.1 meters high. Most of that extra space from staterooms I use for the life support tonnage...

 

[far-trader]

I make this part of the standard actions taken to prepare the ship when going to "Battle Stations".

It is also standard in most serious military science fiction novels, for example in the Honor Harrington series.

I never have fwiw. I think one of the funniest arguments I've heard about how ridiculous the idea is along the lines of "...and it was standard practice for wet navy ships to open sea-cocks and flood all compartments before battle to avoid rapid sinking in case of a hit in combat."

First off, rapid decompression isn't going to be that rapid from something that a self-sealing hull or slap patch can fix. In fact the best reason for a self-sealing hull is because those kinds of leaks can be difficult to find or get to to fix. You won't lose air so rapidly as to worry about having to get into a vacc-suit.

Second, hits that would cause rapid decompression are going to be such that the last thing you would be worried about is the lack of air. You might even be blessing the fact since you won't be on fire or suffer from the horrendous wounds for long. And if you happened to already have your vacc-suit on it would probably be so shredded as to be useless.

Thirdly, just where do you put your air when you decompress routinely for battle (or Jump precipitation)? If you just vent it how long does it take to recompress and from where do you create this replacement air volume? And if you store it in some compressed form it will require serious warming again to be of use. And you have to factor in the possible damage effects of your highly compressed air safe being damaged in combat.

In my opinion the reason for a self-sealing hull is to reduce or eliminate the need for damage control parties and extra maintenance/repair personnel and gear. It would be common on civilian ships, less so on merchant ships, and unlikely on military ships.

For combat effects I would say you loose atmosphere/integrity entirely only when your hull points reach 0. No amount of patching then will help. You need a shipyard for repairs and your streamlining (if any) is destroyed as well.

For all other hits only Turret, Bridge, and Hold would cause rapid decompression, in those areas only. The Bridge hit already includes crew effects (to answer the did they suit up fast enough question). Turret gunners would probably be the only crew routinely buttoned down in combat armour for battle. These hits would not permit a save from self-sealing hull or slap patches as above and require shipyard repairs and reduce streamlining.

Crew hits may or may not be decompression related. They are as likely to be secondary effects.

Without a self-sealing hull each hit will cause minor atmospheric integrity loss. Eventually you will have no air unless you apply patches manually. How long? That's a ref call I guess...

I'd go on but I've got to run.

 

[rust]

It is not only about the conservation of air and the prevention of a rapid
decompression, it is also about the prevention of fires, since without any
oxygen present there is not much which could burn, while with oxygen
present and battle damage from lasers and similar "incendiary" weapons
quite a lot can start to burn, beginning with hydrogen fuel leaking into
the ship's interior after a hit - and a "Hindenburg desaster reenactment"
is not much fun for the crew.

 

[DFW]

It is not only about the conservation of air and the prevention of a rapid
decompression, it is also about the prevention of fires, since without any
oxygen present there is not much which could burn, while with oxygen
present and battle damage from lasers and similar "incendiary" weapons
quite a lot can start to burn, beginning with hydrogen fuel leaking into
the ship's interior after a hit - and a "Hindenburg desaster reenactment"
is not much fun for the crew.

Also, blast concussion effect is greatly reduced when there is no atmosphere present. This would reduce internal damage further.

 

[rust]

And yet another, although minor point: The enemy's sensors can "see"
whether the ship is losing air, how much air it is losing and how fast it
is losing the air, because this air is warmer than space and easy to de-
tect with an infrared sensor. One usually does not want the enemy to
know that one has been hit, and how badly one has been hit, it could
attract additional unwanted attention.

 

[Captain Jonah]

Well it may sound good but having no air to stop fires presumes that aerosol fire suppression systems of just venting a single compartment has suddenly become a lost science.

For those of you quoting sci-fi games such as HH I seem to remember they wore the suits in case of a hull breach not because they were draining the air. They kept gloves off till the last minute because even high tech vacc suits were far less dexterous than bare fingers.

Putting on vacc suits before combat yes, blast damage spread by air is going to be a very minor problem. You are in a metal box that is being hit. Hull transfer of shock will shatter bones, spalling will cut you in half or shred your suit. Thermal transfer will roast you alive even if the bulkhead remains intact if it flash heats to a few thousand degrees.
A hit on the hull sends shrapnel across the room and shreds your suit, without air you are dead. A shock wave slams you into a deck or wall and your polymer helmet fractures, without air you die slowly. Your vacc suit (unless at very good tech levels) is clumsy and fragile compared to the combat going on outside. Not having air as the result of combat is a problem, not having air before the combat even starts is just plain silly in my opinion

Aside from the suicide jockeys in fighters just about every picture of ships crew in space battles has them in uniform or shirt sleeves, draining your air to prevent a few minor risks causes far more. Read some of the sections in the HH books or other stories about the difficulties of dealing with casualties when the ship is out of air. It’s far worse than treating wounded with air around.

So do you reduce crew efficiency and dexterity, significantly increase the lethality of any wound and decrease the ability of your medical crew to treat casualties in order to save on some fire suppression gas or to reduce blast damage?

I’ll stay with the fresh air and put my suit on with helmet and gloves close by just in case. :lol:

 

[Captain Jonah]

And yet another, although minor point: The enemy's sensors can "see"
whether the ship is losing air, how much air it is losing and how fast it
is losing the air, because this air is warmer than space and easy to de-
tect with an infrared sensor. One usually does not want the enemy to
know that one has been hit, and how badly one has been hit, it could
attract additional unwanted attention.

Well they would see a plume of ice as the water in that air froze. They would also see great sprays of fuel or lumps of hull or structure, they would see your sensor output or drive strength fall.

Plus with traveller visual sensors unless you are fighting at missile range they can see the damage they are casuing you, normal visual sensors give you shape and structure at Long range, that is optimum range for P-Beams and further away than you would want to fight with other weapons.

If you can see chunks of the enemy ship being blown out or in by your weapon hits you don't need to see a tiny cloud of frost to know you are hurting them. :wink:

 

[DFW]

Putting on vacc suits before combat yes, blast damage spread by air is going to be a very minor problem.

Unless it is an internal explosion. :lol:

Plus with traveller visual sensors unless you are fighting at missile range they can see the damage they are casuing you, normal visual sensors give you shape and structure at Long range

Actually, the IR sensors give heat sources, from whatever source, at that range.

 

[barnest2]

The point is that you can see the holes anyway... So its not a big deal if you can see the heat as well...

 

[rust]

The point is that you can see the holes anyway... So its not a big deal if you can see the heat as well...

I doubt that one could see holes at a distance of 2,000+ km, and the way
I read the sensor ranges in the rules the limit would be around 1,250 km,
when visual sensors can no longer show detail, while infrared sensors -
according to the rules - can show hot spots at up to 25,000 km.

 

[DFW]

I doubt that one could see holes at a distance of 2,000+ km, and the way I read the sensor ranges in the rules the limit would be around 1,250 km, when visual sensors can no longer show detail, while infrared sensors -according to the rules - can show hot spots at up to 25,000 km.

Correct. You may not be able to see the fissure in the hull but, you can note the IR sig of the leak caused by it.

 

[Jak Nazryth]

Until I find a better solution or official rule, how about this.
Each Hull hit looses 1d6 tons of air per turn until it's repaired by bulkhead patches or more permanent means etc... That equates to a max of 1 ton per minute of time. The more holes "hull hits" the more air escapes...

If hull is reduced to zero, all remain air escapes within the same round as the last point of hull is removed.

Sound ok or does anyone have a better idea on how to handle in game, roll playing in the middle of combat? It gives engineer types something to do besides keeping engines running... like saving EVERYONE'S life!

 

[rust]

Sounds okay to me.