Musings about ship Armor....

[infojunky]

Was flipping through FF&S and stopped at the armor for ships section... A 1g ship requires 5cm (armor 10) of steel as it's base armor... Well then I figure lets look at that thickness in Striker, that same thickness there is a armor of 18....

Related I have always thought that the perceived hull strength of ships was a bit high, well a lot high, as in the real world ships are tough, but not that tough in relation to all the weapons available. Actually modern ships the hulls aren't that thick, but rely on void spaces to contain the damage that should get through...

With all that I probably will say in my games that unarmored ships will have a "armor" of 18 or 20... Leaning towards 18, as that is 5cm or 2 inch plate in steel.

I must note I use the penetrations from AHL instead of Striker mostly....

 

[Spinward Flow]

I have always thought that the perceived hull strength of ships was a bit high

Impact energies at orbital velocities tend to be ... high ... carrying ridiculous amounts of kinetic energy.
Also, in the Traveller context, you're going to have to assume that craft will "go places" where ... significant micrometeroid impacts ... will need to be "tanked" by the hull, rather than necessarily being something easily avoided.

 

[infojunky]

Impact energies at orbital velocities tend to be ... high ... carrying ridiculous amounts of kinetic energy.
Also, in the Traveller context, you're going to have to assume that craft will "go places" where ... significant micrometeroid impacts ... will need to be "tanked" by the hull, rather than necessarily being something easily avoided.

Depends. Really consider this, the number of Satellites in orbit with less than an airliners thickness of skin on them. Also really consider how much 2 inches of steel really is. You average Panamax or Malaccamax Container/Tanker only has 15mm or so hull thickness.

Also consider the actual structure of the hull, a thin outer layer with a gap before the main hull will shrug off most of what you are concerned about. As High velocity small objects (i.e. smaller than you navigation radar can track) will expend most of their energy at the initial impact point with the thicker hull underneath being relatively unharmed.

Then there is that bit in Beltstrike stating any ship with a active maneuver drive is immune to Micrometeoroids...

And finally I am talking about Merchant Hulls here for the most part.

 

[Grav_Moped]

Impact energies at orbital velocities tend to be ... high ... carrying ridiculous amounts of kinetic energy.

Not just orbital -- interplanetary, and those running jumps from deep gravity wells too.

Not a whole lot out there to hit, but at those speeds it doesn't take much.

 

[Spinward Flow]

consider this, the number of Satellites in orbit with less than an airliners thickness of skin on them

I have.
Satellites in orbit around Terra are in a KNOWN environment that has been well examined, charted and is relatively well understood. That means that satellites that orbit around Terra have a KNOWN set of constraints on how rugged their hulls need to be (not very) due to how relatively uncluttered the orbits they occupy are (meaning, no active Kessler Syndrome). If those satellites deal with an atmosphere, it's a SINGLE TYPE of atmosphere.

Now send those same satellites to other star systems.
Proxima Centauri
Alpha Centauri
Barnard's Star
etc. etc. etc. etc.

What kinds of space environments will they encounter there?

What if a star system is "relatively dusty" (in the astronomical sense of "dust") rather than being a place that has been swept clean by sunlight and gravity wells?
Think clouds of lunar regolith blown off the surface of the moon by rockets if it helps.

What if the planetary atmosphere you need to deal with can range from vacuum through insidious?



Space is EMPTY ... except where it isn't ... and where space isn't empty, it's potentially hazardous to be there.
At orbital velocities, what we ground pounders think of as a sniper rifle round is effectively a water pistol (with a leaky squeeze pump) in terms of comparative penetration power.



If you're dealing with a SINGLE KNOWN LOCATION that is well charted, you can probably get away with "skimping on the hull" materials, like you've alluded to (at the risk of a catastrophic failure in the event of an impact). The engineering calculus changes when you've got lives and a life support system to protect ... and it changes yet again when you need robust protection from the radiation of a wide variety of natural sources (planetary magnetospheres, stellar winds, etc.) that a starship might encounter in ANY star system, not just in a single one.

Due to the sheer variety of potential environmental conditions a starship might be subjected to, when it comes to hull protection, there is going to be a bias towards "bulking up" even for Armor: 0.

Also, any streamlined hulls are going to need to remain structurally sound when "stationary parked" inside a gravity well, which could range from 0-1.5G under nominal circumstances ... and that's before needing to deal with Max-Q velocities inside of atmosphere.



Note that according to CT Striker 2, p41:

6. Armor: A vessel's Striker armor rating depends on its High Guard armor rating, as shown on the table below. If a vessel is hit, roll damage on the High Guard damage table, using the weapon's penetration as a negative DM and the ship's armor rating plus 6 as a positive DM.

Armor Rating​

High Guard	0	1	2	3	4	5	6	7
Striker	60	64	67	70	72	74	76	77

Add one to the Striker armor rating for each High Guard armor level over 7.

CT Errata, p36 revises the above table by literally -20 across the board:

Armor Rating​

High Guard	0	1	2	3	4	5	6	7	+1
Striker	40	44	47	50	52	54	56	57	+1

Other editions of Traveller will (understandably) use different methods of deciding this question.
I'm merely citing CT here for convenience and as an historical starting point for thinking about the question.

Also consider that "when taking a Striker style approach" to this question, the tech level of the starship is going to make a TREMENDOUS difference in the actual hull thickness.

TL=7-9 is Composite Laminates, which are x2 toughness of hard steel for armor purposes.
TL=10-11 is Crystaliron, which is x4 toughness of hard steel.
TL=12-13 is Superdense, which is x7 toughness of hard steel.
TL=14-15 is Bonded Superdense, which is x14 toughness of hard steel.

According to CT Striker, Armor Rating 40 = 33.6cm of hard steel.
Taking the above toughness factors into account, you get the following hull thicknesses:
TL=7-9 is Composite Laminates ... 33.6/2 = 16.8cm hull thickness.
TL=10-11 is Crystaliron ... 33.6/4 = 8.4cm hull thickness
TL=12-13 is Superdense ...33.6/7 = 4.8cm hull thickness
TL=14-15 is Bonded Superdense ... 33.6/14 = 2.4cm hull thickness

 

[mike wightman]

I thought I would dig out the m-drive quote since it doesn't get enough attention:

Ships under power are not affected - part of the M-drive generates a low-power screen against radiation and meteorite impact

 

[Condottiere]

That should be interesting trying to implement.

Though you do need to account for acceleration factor plus three percent, which is almost triple that of the current one percent, in the form of additional features.

 

[Spinward Flow]

Excessive pruning of quotes can potentially miss important context (as a matter of general principle).
Here is the more complete context of the quote that @mike wightman was citing.

CT Beltstrike, p2:

AT ALPHA
The only settlement on Alpha is Gerrison. with its accompanying starport and a scout base. The starport, scout base. and settlement at Alpha are buried into one side of the irregularly shaped pfanetoid. Alpha is held in a tIdal lock by Bowman Prime, with one side always facing the gas giant; the inhabited section of Alpha is on the opposite side from the primary. This gives extensive natural shielding against the dangerous radiation which is found this close to Bowman Prime. (Ships under power are not affected--part of the M-drive generates a low-power screen against radiation and meteorite impact--but a power failure during approach within about a million kilometers of the gas giant would be fatal.)

The basic notion here being that "hull alone is insufficient protection against natural hazards" and that a POWER ON (and operational maneuver drive!) condition is required for a crew (and computers lacking a fiber optic backup?) to survive the harsh/hazardous environmental conditions.

However, it would be foolish to overly interpret this quote.
Don't think that a powered up maneuver drive is "all you need" and that a "tin foil hull" is all you need so long as you've got power for your maneuver drive.

I would interpret it as being that Armor: 0 hull PLUS an actively powered maneuver drive are required (an AND condition) ... rather than some kind of OR condition. The idea here being that an Armor: 0 hull in combination with a powered maneuver drive provides sufficient environmental protection against meteorite impacts and the gas giant's radiation belt(s) ... but that's a matter of the powered up m-drive being able to "soak most" of the incoming energies (kinetic, photonic, etc.) and then letting the hull "tank the rest" of those incoming energies (provided there is sufficient minimum hull to do so). Remove either part of the engineering equation and you're back to having problems (of the potentially fatal variety).

What is NOT mentioned in the above quote (because it wasn't exactly relevant for the types of craft being used in the scenario) was how much armor value is sufficient to not need a powered up maneuver drive ... probably because the typical Type-J Seeker that was provided for the module simply doesn't have any hull armor (so the question was largely moot).

Just as a rule of thumb, I'm thinking that a Buffered Planetoid (Configuration: 9) with a default Armor: 6 starting point may be sufficient to dispense with the need for the addition of powered maneuver drive protection ... but that's an exercise in judgement left to Referees should they be so inclined to pursue the notion.

 

[infojunky]

Space is EMPTY ... except where it isn't ... and where space isn't empty, it's potentially hazardous to be there.
At orbital velocities, what we ground pounders think of as a sniper rifle round is effectively a water pistol (with a leaky squeeze pump) in terms of comparative penetration power.

Again I suspect you don't get how much armor even 2 inches of steel or the equivalent is.... I.e. a 3 inch Tank (re, Naval) guns will have issues with penetration in that realm.

The Armor 40 of Striker is over 12 inches thick, think battleship levels of armor. Hint a modern Aircraft-carrier's flight deck is only 4 inches thick...

Then consider the nature of the Micrometeriods, they have mass but structurally they are frangible in nature. As such they have a much lower amount of penetrating power. So it is more about effective design rather than sheer thickness.

As for radiation placement of your fuel tanks is probably more important than sheer armor thickness.

Again, the base hull is what I am talking about, actual armor is above and beyond that...

 

[whartung]

The other considerations are the armor as a structural member for an ungainly, perhaps not perfectly balanced ship undergoing potentially high G loads, not to mention torsion forces.

 

[AnotherDilbert]

The Armor 40 of Striker is over 12 inches thick, think battleship levels of armor. Hint a modern Aircraft-carrier's flight deck is only 4 inches thick...

Sure, it's the equivalent of 336 mm hard steel, but no-one is actually using that (I hope).
It's about 168 mm TL-9 armour, 84 mm (~3.3") of TL-10 armour (crystaliron), or 24 mm (<1") of TL-15 armour.

Still a bloody lot of armour to cart around, but far less than 13".

E.g. by MT a TL-12 100 Dt Scout would have ~350 tonnes of armour of a total of perhaps 1500 tonnes.


Current tanks have far better protection in the front, up to 1000 mm RHA equivalent (TL-6 armour) [officially, perhaps?].

 

[Spinward Flow]

The Armor 40 of Striker is over 12 inches thick, think battleship levels of armor.

If it's made out of TL=6 Hard Steel ... sure.
Remind me again what the "usual" tech levels are for starships again ...?

TL=6 is Hard Steel ... 33.6/1 = 33.6cm of hull thickness
TL=7-9 is Composite Laminates ... 33.6/2 = 16.8cm hull thickness.
TL=10-11 is Crystaliron ... 33.6/4 = 8.4cm hull thickness
TL=12-13 is Superdense ...33.6/7 = 4.8cm hull thickness
TL=14-15 is Bonded Superdense ... 33.6/14 = 2.4cm hull thickness

33.6/2.54 = 13.29 inches thickness of Hard Steel @ TL=6
16.8/2.54 = 6.62 inches thickness of Composite Laminates @ TL=7-9
8.4/2.54 = 3.31 inches thickness of Crystaliron @ TL=10-11
4.8/2.54 = 1.89 inches thickness of Superdense @ TL=12-13
2.4/2.54 = 0.95 inches thickness of Bonded Superdense @ TL=14-15

As for radiation placement of your fuel tanks is probably more important than sheer armor thickness.

Best shielding against radiation is "lots of hydrogen atoms" ... which conveniently enough translates into L-H₂ fuel tanks for our starship engineering purposes. So wrapping fuel tanks around habitable spaces on deck plans is a good idea, so long as you can keep a decent "width" of fuel tankage to keep things relatively efficient from a thermal management perspective (liquid hydrogen likes to "boil off" at some pretty low temperatures).

Again, the base hull is what I am talking about, actual armor is above and beyond that...

For (war)gaming purposes, I'm thinking the foundational intent at the game design level was to make space ships and starship hulls "sturdy" against man portable weapons fire (think bulkhead damage absorption values) rather than making them as flimsy as possible (sneeze next to it and you break it). That presumption only works if hulls built using the starship construction rules are "structurally beefy" by default ... and then armor just makes them even tougher on top of that.


And just as a fun little aside ... where have I heard the numbers "6 inches" versus "1 inch thick" in a sci-fi(ish) pop culture context outside of Traveller before?

16.8/2.54 = 6.62 inches thickness of Composite Laminates @ TL=7-9
2.4/2.54 = 0.95 inches thickness of Bonded Superdense @ TL=14-15

Oh yeah, that's right ...

And before you think I'm just being facetious about Transparent Aluminum ... realize that it's a REAL WORLD material that was actually patented in 1984 in the US (hence why it showed up in a sci-fi movie released in 1986) and has in fact been known about since the 1960s.

ALON was used as the material for the cupola dome window on the Inspiration 4 private mission in Crew Dragon launched by SpaceX just a couple years ago. If memory serves, at the time it was the largest pressurized window ever launched into space by humans Solomani.

Your turn.

 

[infojunky]

Ok, to be even more clear, realistically my goal is to remove starship immunity, I want the players to sweat when the ground armor rolls up.

The whole thickness bit is just a descriptor for me. As I was saying I was flipping through and the thought occurred to me was how thick is a ship's hull, not what the armor value was.

Also my generic assumption is the vast amount of shipping hulls are flavor of Composites... But as I trend towards CT ship construction that covers a lot of ground.

 

[AnotherDilbert]

Ok, to be even more clear, realistically my goal is to remove starship immunity, I want the players to sweat when the ground armor rolls up.

A TL-9 tank shouln't have much problem penetrating a basic spacecraft:


1D + 44 (Pen) - 40 (armour) is a third chance of a major hit, according to Striker.

 

[Spinward Flow]

thought occurred to me was how thick is a ship's hull, not what the armor value was.

In that case, you're asking the wrong question ... because as already demonstrated (twice!) "how thick is a ship's hull" is going to vary dependent upon technology level. There is no "singular one size fits all" answer to your question as stated. The answer is not "1 inch at all tech levels" like you were hoping for.

Also my generic assumption is the vast amount of shipping hulls are flavor of Composites

If they're TL=7-9 they are made of Composite Laminates.
If they're TL=10-11 they are made of Crystaliron.
If they're TL=12-13 they are made of Superdense.
If they're TL=14-15 they are made of Bonded Superdense.
Even at Armor: 0.

Any questions?

 

[Condottiere]

Currently, by default, the spacecraft hull would be titanium steel.

And you can divide zero percent by volume to find out the thickness, when no armour factor is mentioned.

 

[kilemall]

Sure, it's the equivalent of 336 mm hard steel, but no-one is actually using that (I hope).
It's about 168 mm TL-9 armour, 84 mm (~3.3") of TL-10 armour (crystaliron), or 24 mm (<1") of TL-15 armour.

Still a bloody lot of armour to cart around, but far less than 13".

E.g. by MT a TL-12 100 Dt Scout would have ~350 tonnes of armour of a total of perhaps 1500 tonnes.


Current tanks have far better protection in the front, up to 1000 mm RHA equivalent (TL-6 armour) [officially, perhaps?].

I think modern tank armor merits the ceramic description and thus higher TL.

 

[kilemall]

A TL-9 tank shouln't have much problem penetrating a basic spacecraft:
View attachment 3896

1D + 44 (Pen) - 40 (armour) is a third chance of a major hit, according to Striker.

Working backwards from the joules of the impact of a missile at typical speed vs hits a la the missile supplement, I worked out that a typical 1-10 ton single hit in CT is equivalent to a 120mm tank round hit on the Atomic Rockets boom table.

Therefore our lasers need to do the same.

As I recall, the errata bumped up armor into the 60s- requires more juice, but certainly ground force doable at close range.

 

[AnotherDilbert]

I think modern tank armor merits the ceramic description and thus higher TL.

Certainly, but it's not 1000 mm either, it's the equivalent strength of 1000 mm Rolled Homogenous Armour (~TL-6 Hard Steel).

 

[AnotherDilbert]

As I recall, the errata bumped up armor into the 60s- requires more juice, but certainly ground force doable at close range.

Other way around, it was originally 60, errata down to 40.


I never used the errata fully, otherwise Striker grav tanks could easily carry more armour than HG battleships...