Star Wars RPG supplement, D6: Black Ice

[Mr. Oragahn]

Ok, straight to the point: there's interesting stuff in that Black Ice book, in terms of details and numbers, BUT it will take some time to get through all of it. It has surprising references about the engines of the Death Star, fuel density, potential power of such fuel, firepower of a large Torpedo Sphere (there are two sizes), etc.

[Mike DiCenso]

Interesting find, Mr. O. It should be easy to calculate the size and volume of the fuel container spheres in that comparison chart, and then divide the fuel density into it. Unless Imperial fuel has weird super-density requirements, of course. Is it stated what kind of fuel this thing hauls?
-Mike

[Mr. Oragahn]

Typical ship fuel, liquid and with a density iirc that came around 1 kg/m³, but that was done very, very quickly. There are some issues about the size of the ship itself, and I went looking for more info on Wookieepedia and observed that things were even more complicated.

[Mike DiCenso]

Then simply pick the smallest size for the vessel, recalculate the sphere sizes and volumes, and then divide the fuel tonnage figures into it for a more favorable density.
-Mike

[Mr. Oragahn]

Oh don't worry, I got there but I'd rather go through it with other more important matters settled first, instead of picking a bit here and there and treating them really too sporadically.
Besides, the calculation of the volume requires the extraction of other internal volumes first, and that requires a bit of scaling-on-picture work. I already have a couple of PSDs ready to be updated for that, but as I said, I'd rather deal with a whole chunk of it at a time. Besides, I would have to read the whole thing first, because I really skimmed it thus far, my mind clamping to some shiny beacons of interest, sort of.

[Mr. Oragahn]

Here we go, as promised, here are the commentaries on the RPG supplement Black Ice, by West End Games.

The first part of the adventure deals with a woman Alliance field mission commander, Major Lawra Mers, sending a team of rebels plus a droid to infiltrate a low-defense Imperial Intelligence TSB outpost, hack some computers and get back with the info to prepare for a raid against an Imperial convoy.

The Alliance HQ Sector of that adventure is located on Fangol, a deadly ice planet covered with a mist saturated with metal particles. It makes the base undetectable and any flying through the mist hazardous and most entirely done by sight. A single small artificial moon floats there, operated by droids which can be entirely deactivated, and takes care of communications. It has a proper comm-suite to punch through the mist and reach the deeply buried base, although it's possible sensors are located at the surface.
There are around three thousand Rebel operatives at that time in the base of Fangol. It also hosts 100 starfighters, 5 corvettes and 6 light cargos.
The Rebels see with Lawra to assault a resupply convoy at Refrax.

So we start with picks from the briefing and hours preceding the attack.

Several weeks ago, Sector HQ acquired two Imperial Spiral-class ship assault vessels -Lawra doesn't say how. These are small, needle-shaped craft, specially designed to bre their way through an enemy vessel's particle shields and straight into the side of the ship. Then the assault team emerges and captures the vessel before its crew knows what hit them.

More details about those crafts come through the next episode (that's how an adventure was divided).

Assault Ship
The Spiral-class in a single-use, small-unit boarding craft, designed for the rapid insertion of special forces into non-military vessels or space stations. The ship is equipped with no ranged weapons at all, instead relying on stealth technology to keep targets from spotting it until it is too late.

When the Spiral hits the target's particle shielding, the shaped proton charge detonates, disrupting the shields for a fraction of a second - long enough for the Spiral to burn through and bury itself into the target's side.

The Spiral's nose cone is composed entirely of sublimating tekonite, which vaporizes upon collision, absorbing nearly 92 percent of the kinetic energy of the impact, insuring that the ship's cabin survives the collision virtually intact. Additional protection to the passengers and crew is provided by inertial-damping grav couches.

Once inside the target, the vac-suited passengers exit and overwhelm the stunned crew of the boarded vessel.

So a contact proton shaped burst can put a hole into a particle shield for a fraction of a second.
This proves enough for the craft to fly through it.
We're dealing with the equivalent of a plasma burst here, at best occuring within microseconds.
So that would be th equivalent of a small charged nuke, firing up a proper mixture into a forward cone.
We don't know the yield, but it's hard to believe that it would surpass a proton torpedo's 1 kiloton yield (figure from the Star Wars Technical Journal).

The ship comes with "Shields 2D+2". So it does have shields.
Some other various details:

The Spiral

Gren Lavorn, the base's spacecraft maintenance officer, shows the Rebels the ship they will use in the assault, a Spiral-class vessel designed to penetrate hull and shielding. Over 70 percent of the ship is subspace engines and shield generators, giving the Spiral power but no grace

A cabin on large engines; I'm puzzled by the "subspace" thing though. That would logically mean it's hyperspace capable, but I wonder if the author didn't mean realspace instead, or sublight.

Equipment

The Spiral is severely limited in cargo space, allowing each passanger to carry only a few small items in an overhead bin and not much more in a rear cargo compartment. There's only enough room inside the craft for each of the Rebels to stow a knife, blaster pistol, two space ammunition packs, and a medpac. All other equipment must be stored in the rear cargo compartment, which will hold any two of the following: two weeks' emergency rations, up to four blaster carbines and extra ammo packs, six medpacs, 24 grenades, and QT-7.

QT-7 is the hacking suitecase sized droid that is transportable.
Globally, there's not much place even in the larger rear hold.
Clearly, a Spiral is not a large craft at all.

Arrival

It's no fun going into battle blind, stowed aboard a slow, virtually defenseless freighter.
[...]
Within seconds, the after hatch on the freighter opens, sending both assault ships into space.
[...]
You bring your mind back to business and find your prey, the huge, black string of pearls directly ahead. It's bigger than you expected, and it appears to be about 500 kilometers away.
You check your instruments.
Then you recheck them.
The schematics were correct. That thing out there is 7,800 meters long - five times the length of an Imperial-class Star Destroyer.
More details become apparent as you close with the train. The Ice is composed of three main sections: two huge engines pods, and between them, the cargo fields, nine shimmering black balls of force, each containing 110,000,000 tons of high-grade starship fuel. You try not to think about what would happen if you missed your target and crashed into one of them...
Your sensor beeps: 10 seconds to impact. You make your final course adjustments and activate the inertial couches - your're now totally helpless until you slam into the vessel or miss...
... eight, seven... the shielding lowers over the transparisteel, leaving you blind... six, five, four... you hear a "click" as the proton charge arms itself... three, two -WHUUMMMMP!!! Screeeeee!
You're through the shielding! One second to impact -
There's a sudden wrenching shock to your body. Everything goes black.

Wow, what a ride!
So, what can we take from that?
Well first of all, we can obtain a speed estimate, as well as an idea of how far the particle shield extends from the Black Ice. We can reasonnably guestimate a kinetic energy for the boarding crafts. it will be interesting because we'll know that only a special alloy, used in supposedly a sufficiently large quantity to protect the ship's bow, can only cope with 92% of that energy.
Meaning that pretty much anything else will be of inferior resistance against impacts, and that without counting the much likely fact that, as said, the nose of such a one-use ship would have quite a lot of armour.

The particle shield is more than one second offset from the engine pod's hull.
Shields in Star Wars, especially starship shields, tend to hugg the hulls.

Let's try to obtain the highest speed possible. Assuming no deceleration, we know that the distance to cover was rougly 500 kilometers, and that it took more than ten seconds, at least.
Make that 11 seconds, then. That's an average speed of 45.454 km/s.
The Spirals are launched from freighters. The book said that the HQ had "six light freighters".
Looking at Wookieepedia's light freighters page, I see that in general, cargo capacity stands around 110 metric tons, sometimes much less, sometimes up to 200 tons. Or 250 tons for the YU-410, but this one is 44 meters long and quite bulky. There are other big models though, such as the VCX-350 and some YZ models. They come with cargo capacities above 200 metric tons.
No matter what, a Spiral is only going to mass a fraction of that cargo capacity. But let's pick 250 tons, though.

That's a kinetic energy of 61.725 kilotons, and that's the high end of it.
Of course a craft that travels space at a speed of 45 km/s and slams just as fast into a ship is not only very Star Warsish, but simply never observed. We've also seen enough ship disintegrate due to physical contacts with objects of various sizes at considerably lower velocities.
That's for the average velocity mind you. The final one would be 90 km/s, and the KE 241.99 kilotons.

As pointed out before, shields tend to be projected very close to the hulls in general, but the fact that in that case, it took the Spiral more than one full second to crash into the engine pod would tell us that the shields was closer to the kind of force field present on the first Death Star, even if that battle station actually had rudimentary passive defense systems.

Still, it's not an easy thing to sell such as a gap between the shield and the hull that's greater than one kilometer, and one kilometer per second is already fast.
I wouldn't expect the Spiral to mass more than one or two dozen tons at best.
At 20 tons, and 1 km/s, we get an impact of 10 GJ. That would be in line with what's generally observed in Star Wars.

Moving on.

On page 16, we learn that a landing bay uses magnetic shielding which a ship can fly through to land safely.

About Black Ice

Black Ice is a container train, designed and built by Rendili StarDrive, builders of the Victory-class Star Destroyers. At full size, with all force containers active, the Ice is 7,800 meters long, with a weight of 1,210,000,000 metric tons.

Cargo Holds: Most of the Ice is cargo space. The nine black balls, 600 meters in diameter, are force fields, each contained between field projectors. The balls are filled with refined fuel for power cells - 110,000,000 tons each. A large conduit runs down the center of each hold, carrying power from the engine units to the force fields and connecting the engine units with each other. Balls can be added or removed to change the size of the train.

Although I guess the mass that's given is for the fuel, it's not clear enough here. Fortunately, from the excerpt taken earlier on, we know the 110 million tonnes figure corresponds to the fuel's mass. So we know we'll have to remove two things to get the real fuel density here: the two force field projectors, which as you'll see, are part of the sphere. The projectors are solid spherical caps that take some volume of the whole sphere. There are opposite caps on either side of a sphere.
Then there's the large conduit that passes through each sphere as well.

Still, as a quick idea, if we used the mass as that of the entire sphere, the bulk density for a volume of 1.131 e8 m³ would be 0.9726 ton/m³.
The real figure will be superior to that.

Engine Pods: The two engines pods are huge, dwarfing even the engines on Star Destroyers and rivaling those on the Death Star. The fore and aft engine pods are identical (as the ship moves in either direction with ease, the terms "fore" and "aft" change from trip to trip, depending upon which way the vessel is moving).

The engines of those engine pods are huge, close in size to those used on the Death Star.
This shall prove extremely interesting, since the Death Star's sublight ion engines are located somewhere in the large equatorial trench. We'll come back to that later on.

Command Capsules: The crew spends most of its time in the command capsules which sit atop the engine pods. These are 330 meters in length and 75 meters wide, about the size of a frigate. The entire ship is controlled from these capsules, and the crew is rarely required to enter the engine pods, and almost never visits the cargo balls.

There's a discrepancy between the two schematics provided in the book, and the figures above only fit with one of them.
We will also get back to that later on.

Crew: Despite its huge size, the Black Ice virtually runs itself, requiring a standard crew of only 200 - 100 in each capsule. As half of the Ice's crew is on shore leave, there are only 50 crew-members currently in each, the highest ranking being second lieutnants.
[Stats and stuff about local labour droids]

Transport: The ship is crisscrossed by a complex system of walkways, repulsortubes, and crawlspaces. In addition, each engine pod contains a low-powered shuttle for longer journeys and for carrying heavy loads. The shuttle travels through the cargo balls, connecting the fore and aft engine pods.

There. That's enough info about the BI for now.

[Mr. Oragahn]

Time for pictures.



Here comes the first schematic view of the Black Ice. Well, a portion of it, but it's supposed to be representative of the entire craft.
This is where the first errors creep up.

The biggest error is the huge difference of size between the command capsule and a fuel ball. The CC is 330 meters long, and a ball 600 meters wide. However, using the scaling ruler there of 40 meters that's provided on the page, the CC is found to be 337 meters long, which we'll say is correct, but a ball comes out at about 1330 meters wide!
Slight problem here.
The Millennium Falcon is around 39 px long, thus around 33 meters long. That one is accurate as long as you ignore the mini Falcon used for outdoor shots in TESB. For those who remember the long and detailed MF page at Bob Brown's website, it was painfully obvious that the ship needed to be bigger, and sufficiently pointed out how Chewie was completely squeazed inside the cockpit during those "repair" shots inside Echo Base.
I didn't verify the Corvette, and I know that ROTS didn't simplify this at all.



The second schematic offers a closer view to one of the Command Capsules. Both engine pods have one. The profile offers a view of a capsule which can be pallpark at over 346 meters long, but considering the Milllennium Falcon discrepancy where, now, we suddenly get the mini version that's some 23 meters long, the difference or ~16 m for the CC's length compared to the value given earlier in the text is rather minor, percentage wise.



The third schematic, much more interesting, is probably the best to use here, although like the first one, it has a CC that's either too small, or a container ball that's too big.
This one contains more information than the others. Notice, though, that both the first and third ones show the engine pods to have three engines stacked upon each other, while ALL illustrations featuring the Black Ice show engines arranged in two rows of three, the middle assemblies being larger.
I still put an engine height for good measure, but I may need to work out an engine's dimension differently.

For the final volume of fuel, I considered that the cap were not shallow (not dishes).
We get a volume of 1.086627 e8 m³. So the high-grade fuel density here would be 1.0123 ton/m³.
Not exactly very massive, and certainly nowhere the density that would be acrobatically required to legitimize ICS figures.

With shallow caps, I'd have to ignore them and instead work from a conduit that reaches the opposite extremities of the sphere, and find out the volume of a cylinder with two round faces on each end (a "capsule" primitive in 3D). The height of the domes on either end of such a capsule being 3 px on the schematics - that is, negligible - it would be simpler to remove the volume of a simple cylinder that's 600 meters long and 69 meters wide.
The difference for fuel density wouldn't be spectacular anyway, so you would still be right to work from 1 ton per cubic meter.

Now, the Wookieepedia page makes things a bit more complicated.
It sports a link to the FSCV ships.
It cites a maximum length of 10.4 km for the Rendili ship. The Loronar is even longer. But we know that the Rendili FSCV can only transport up to nine sphere, and the ship's total length is only 7800 meters in such a configuration.
A garland of 9 balls is 5400 meters long. That makes each engine pod 1200 meters long.
That's another problem with the schematics, since it shows that an engine pod (without the first ball that's connected to it) is more like 830 meters long (very rough pick with the graphic ruler, based on the silhouette of the ISD, and ported to the silhouette of the entire Black Ice and her nine spheres - nothing biblical btw).

The Wookieepedia pages sources two books, the recent all in one Atlas, and the Imperial Sourcebook. I don't have the former, but I found the reference in the later source. I will use it later on.

[Jedi Master Spock]

Nice catch on fuel density! It's rare we get anything in written form that indicates density.

[Mr. Oragahn]

Here comes a new batch of quotations.

Into Hyperspace
[...]
Once two Rebels make the roll, Ice moves out.
The ship is incredibly slow and unwieldy, but the Rebels can cold jump the hyperdrive once they clear the gravity well...
[...]
Space suddenly expands in the familiar pattern - stars blur, colored lights shoot by - as Black Ice jumps to lightspeed.

1.21 billion metric tonnes are very hard to drive and push forth, even with six large thrusters worth those found on the Death Star.
I'll get to that later on, for the last part of this STL propulsion topic.

Continuing...

We learn that the ship has a plasma forge that is used to build spare parts. The large conduits inside the balls are solid. They're metallic tubes, and attacked by droids trying to kill the Rebels. Droids have been reprogrammed by the captain of the ship, Skolos, who was hiding aboard. There's a sequence of battles and infiltrations to find this guy while the Ice moves through hyperspace.

The Rebels discover that the force field is in place because the conduit in the next cargo sphere has been breached. Fuel has been spilled into the conduit, making passage impossible. The force field is all that keeps the fuel from rushing into the first sphere.

That's when the players' team try to use the shuttle to return to the forward engine pod where there's another Rebel team under attack. The shuttle uses the conduits that go through the balls.
If a conduit is breached, fuel will fill it. Obviously the artificial gravity is cast beyond the limits of the tube itself.

This high-grade fuel is a liquid. It fills volumes, it drips.
It is, for all intents and purposes, pretty much like the translucent fuel seen in the Dark Forces II: Jedi Knight game, when you boarded the large freighter Sulon Star through the fuel pipes while it was docked at Barons Hed.

That's certainly no gas, even less some form of antimatter, exotic or not.

Episode Five
The Blitz

Summary

The Rebels have unwittingly allowed the Imperials to discover Sector HQ's location. Sector HQ decides to evacuate. It will take a week to get everybody off; the Alliance must hold off the Imperials for that long. The PCs take part in the battles, which grow in frequency as the week passes. The episode climaxes with the arrival of a torpedo sphere.

The emergency distress beacon sent a signal to the Empire, so they know where the secret base is.
It takes a full week for the Empire to be able to send a torpedo sphere. The Imperial Sourcebook says that there were only six torpedo sphere in service.
Could that mean that those few defenses would be capable to repel attacks from cruisers such as ISDs, so much that only a torpedo sphere could get the job done?
Mind you the sphere was escorted by small frigates. Lancer-class, if we go by the picture on the cover.

The first day, the first wave amounts to one frigate and a flight of TIEs scanning the region.
The second day sees the arrival of an identical force.
Day four, Imperials finally manage to send Spacetroopers.

Rebel anti-atmospheric guns are given the following ranges:
Short: 10 to 300 m.
Medium: 301 to 1500 m.
Long: 1501 to 8000 m.

It ends with the torpedo sphere entering the system, and heading for the base, "ETA three hours."

"The torpedo sphere is less than three hours away. We've got a few damaged starfighters and a half-dozen virtually unarmed freighters.
Nothing we have will even put a dent in the sphere.
"When the sphere arrives in orbit, it will reduce the base to slag in mere hours. The planet's atmosphere is toxic; even with breath masks - which we don't have enough of anyway - people exposed to the atmosphere will die painfully.

The base was deeply buried.
Still, it will takes hours for the mighty torpedo sphere to reach and slag it.

Following is the plan, ramming the Ice into the sphere:

Once on board the ship, the Rebels will wait until the torpedo sphere is in position to bomb the base. Then - and only then - they will power up the engines and slam the ship into the sphere. The Ice is very, very slow and very vulnerable to enemy fire. They must wait until the torpedo sphere is close to the planet's gravitational pull, and quite close to the Ice, if they are to have any chance to ram it.

So I think it's clear by now. The BI is damned slow. It's sluggish beyond hope.

Therefore, even without even going into complex calculations, I'll point out the obvious: even when having a nice view of the Death Star as it approached Alderaan, we couldn't spot any glow from any idling engine.
The battle station's waistband being of limited width, the engines would appear very small compared to the overall volume anyway.
Now compare that to the engines of the BI which are rather large.
Shall we compare volumes and engine numbers then?

Say the Black Ice is a huge cylinder, 7800 meters long and 700 meters large/hiogh (it should be more like 600 meters high and 700 meters wide since it's larger than it's high after all, but I'm going for some easy comparison here).

The volume would be 3.0018 e9 m³.
The engines take roughly 40% of the engine pod's aft surface area.
So with a circle that's 700 m wide, the thrusters' total aperture area would be 40% of 3.8485 e5 m², or 7.697 e4 m². The aperture of an ion engine is particularly important as to how much thrust one can hope to obtain.

Here, 7.697 e4 m² of combined nozzle apertures push 3.0018 e9 m³ at a very slow pace and make maneuvering extremely difficult.

The ratio Volume/Thruster Area, V/TA, is 38,999.61 m³ per square meter.
Assuming a ship uses the same engines, the smaller the ratio, the faster the ship. Indeed, if the ship's volume increases, the performance per thruster will decrease. Likewise, if the volume is constant but there are less thrusters, the performance will drop like a rock as well.

Now let's look at the Death Star.
Using Robert's scaling, the equatorial trench is 1.23 kilometer wide (for a battle station that's 120 km wide).
The total surface area of the trench's "floor" would be 2.3083 e10 m², while the battle station's volume would be 9.0478 e14 m³.

Let's be generous and assuming that each single square meter of half of the trench's floor is part of a large engine. Obviously, since it's a circle, you will only obtain the maximum forward thrust if the entire engine complex is perfectly ejecting matter along one unique aft vector.

A 120 x 1.23 km wide rectangular thruster would have a nozzle area of 1.476 e8 m².
Compared to the battle station's volume, 9.0478 e14 m³, we get a V/TA ratio of 6,129,945.8.

So now, compare the former Black Ice ratio to the Death Star ratio, and we see that the Death Star's ratio is 157.18 times greater than the Black Ice's.
Doing so reveals that moving a Death Star with the same kind of engines would be a disaster, and remember that I'm assuming the Death Star has just one giant thruster here, not an array of countless thrusters with large gaps in between... which would make the situation even worse.

With this, saying the Death Star has the mobility of a mountain would be an understatement.

That said, the RPG supplement implies that maintaining the force field takes its toll on the FSCV's power generation, so the difference can be mitigated.

We have more details here:

Support fleet has at least 500 vessels, a quarter of which are corvette class or smaller, while a quarter of them are the huge Loronar FSCVs (Field Secured Container Vessels). FSCVs always travel in pairs, their main ion engines faced in opposite directions. On the side opposite the ion engines are gargantuan Prexton double-field generators; these create force fields which are then surrounded by a hyperspace field when the ships make the jump to lightspeed. Each force field sphere is about 800 meters in diameter for 250 million cubic meters of cargo space. Cargo containers are held in place by the force fields. The force fields may be bubble-chained if enough power is available, and 20 or more field spheres are not uncommon.

As the vast majority of an FSCV's power is going through the Prexton, it is no surprise that the ion engines are underpowered. FSCVs at full throttle can take 35 hours and over 600,000,000 kilometers to come to a stop from normal sublight speed, and a liketime to accelerate the ships again. FSCVs are therefore flown on paths tangent to the orbits of planets whose depots are being resupplied. Smaller ships unload and reload the cargo as the FESC flies by, never losing more than a third of their sublight velocity.

Fleet ordnance is responsible for equipping all Navy and Army units with needed weapons and ammunition. Ordnance will use a ship as dangerously insecure as the FSCV only if a huge operation has been ordered suddenly by High Command, not giving ordnance sufficient time to resupply ships and depots. Ordnance usually conduits resupply operations by using available cargo space on more secure vessels, and has priority of the use of such space.

So a FSCV would be, under this definition, an engine pod, or the locomotive on a train that usually counts two of them on each end.
We see that powering the force fields taxes the engines a lot, the Loronar being the more powerful variant, capable of chaining up to 20 cargo spheres, each 800 meters wide.
We can only imagine the size of the engine pods on such trains.
What is interesting is that in theory, the forces required to prevent fuel from drifting into space, at a density of around one ton per cubic meter, is only the force that's related to the ship's change of momentum and direction. Which is kinda circularly funny, since the ship is limited to slow speeds and slow accelerations, and thus forces fields wouldn't have to apply considerable forces to their cargo.
Which means keeping their cargo in place will require the same application of force as to match the acceleration, since the Prexton force field takes the role of a solid shell (a solid shell would transmit the force automatically, since it's linked to the engines - superstructure stress non withstanding). And that's assuming that the ship would have no mass lightening at play, which I believe has been mentioned in the EU recently to explain linear accelerations.

All in all, you couldn't really expect the Death Star to be anything more than a glorified mobile station instead of a scaled up starship.

We also know that a beast like a Loronar FSCV, say at full capacity, takes 35 hours and 6 e8 km to come to a full stop, and about the same time to accelerate.
The average velocity here is 4,761,905 m/s, final velocity is 9,523,809 m/s, for a constant, linear acceleration of 75.6 m/s², or roughly 7.7 g.

The garland of 20 balls would be 16 km long, so that's well above the Black Ice's own length, but there's no reason to believe the Black Ice's own acceleration would be much different.
The fact that they're kept on tangents to orbits is logical, and would tend to mirror the Death Star's orbit around Yavin.

I'm sure some people would love to take a look at those numbers and compare them to ISD accelerations, although we would need to know how much ejecta is produced from the consumption of 1 kg of that fuel, in order get some interesting figures regarding fuel consumption, fuel stock and energy production, based on conservation of momentum.

[Mr. Oragahn]

One more piece...

Finally realizing their peril, the Imperials aboard the torpedo sphere begin serious jamming operations, totally overwhelming Ice's sensors. Then, several TIE fighters make kamikazi runs against the ship - targeting both the command capsule and the highly-volatile cargo sphere.

Globally, the torpedo sphere is incapable of firing at a slow ship which despite its powerful shields that are enough to block standard TIE fire, is threatened by TIEs ramming into it and plowing through those same shields.

The torpedo sphere is taken down while cargo hold 8 collapse and blows up, probably triggering the destruction of the other balls.

Then we have the "highly-volatile" adjective that's applied to the cargo sphere. Earlier on during the briefing, the characters were written as concerned about the idea of missing the engine pod and hitting one of those spheres instead, but that doesn't tell much.
It's difficult to know if the volatile adjective applies to the force field, which then we should believe is just asking to burst violently, or if its content, the fuel, that is highly-volatile. And then, again, would it mean the fuel evaporates fast, or reacts explosively?

But there's a little fragment of information that is of interest. At some point, two TIE fighters decide to ram the Ice, realizing that their weapons can't take down the shields (clearly putting the emphasis on the KE and probably having started away from a good distance).
Apparently the Ice had several sets of shields. In this case, two are said to be necessary to block one kamikaze TIE, and they only have two such shields to cast in order to intercept any of the two TIEs. One TIE is aimed at a Command Capsule, the other at a sphere.
A single shield is clearly said to be incapable of stopping a TIE.

If the TIE heading toward the cargo area gets through, a muffled whuumppp! runs through the Ice, and emergency lights and alarms begin flashing all over the bridge. The TIE has hit and breached one of the force balls, igniting the fuel inside. The fuel ball is beginning to glow bright red; it will blow in about two minutes and there's not a thing anyone can do about it.

A direct hit to the sphere manages to pierce it - as put a hole in it - but does not totally "smash" it into fragments (read total collapse of the field): the force field still largely remains in place, it's even possible that the force field repaired the hole made by the energy bolts. All in all, we still have a sphere which content is progressively burning, up to the point it will actually explode.
I can't really explain why that self-oxidizing fuel wouldn't explode right away, but I think the explanation is that the force field may be capable of absorbing some of the energy, or limiting the expansion of the fuel that's under reaction, thus acting as a buffer and preventing a total runaway reaction (it would explain the red hue instead of a hot white), until it will be overwhelmed and the entirety of the fuel will explode all at once.

As for the torpedo sphere and her shields, we can read this:

Finally, the pilot must attempt to compensate Ice's course for possible evasive maneuvers by the torpedo sphere.
[...]
Once the final course adjustment is made, it's time to get out. The ship is going to impact the torpedo sphere in under a minute, and there's nothing anybody can do about it. At this point, even if the Imperials manage to destroy Ice, its wreckage will seriously damage or destroy the sphere. The Rebels have succeeded — now all they have to do is try to get out alive.

As per the plot, chances of evasion by the torpedo sphere are slim: "If Ice's sensors are operational, this is an Easy starship piloting roll; if not, this is a Difficult roll. If this roll is failed, the pilot may try again in subsequent rounds, but each failure incurs a +3 to the difficulty number."

Clearly, the point is that the torpedo sphere is more or less locked into position, and can't avoid a convoy ship that will crash into it one minute later.
As for the torpedo sphere, even if it manages to blast the Ice within that minute, her debris "will seriously damage or destroy the sphere".
Clearly, a torpedo sphere is highly reliant on escort ships, as its shielding is minimal or improperly powered due to the sphere's mission goal, possibly powering the turbolasers at that time. But the fact that it would be incapable of powering both offensive and defensive systems would be rather telling. It is interesting, in fact, as it mirrors the words of Bevelisk when he voiced his opinion about certain concessions to make in the Death Star design, in terms of power, and how the Death Star's defenses, notably shielding, would be minimal considering the power requirements for everything else.

Anyway, you have 110 million tons of fuel, at the very least, that blow up and destroy the torpedo sphere.
However, one of the engine pods is still there, spinning. Clearly the explosion didn't cause an absolute chain reaction, so much that it didn't reach up to the engine pod in question, despite the fact that it's directly into contact with one of the nine cargo spheres.
Later on, countless chunks of metal are seen raining down on the planet.

[Mr. Oragahn]

To finish things on a good note, here's what such an amount of fuel allows the Empire to do;

Black Ice. It carries nearly one billion tons of starship grade fuel cells - more than a year's worth of power for an entire Imperial Main Battle Fleet.
Black Ice. If she remains in the Empire's hands, the Imperial Navy will cut a swath of destruction across the sector - and beyond.

We have an idea of the average power consumption of a main battle fleet, alongside an idea of the strategic implication over the control and loss of such a ship and its payload.

For the first, we know it's a liquid, and already under a high-grade enrichment state. It is ready to use, as described by the ISB.

Despite how unpopular the following idea is, I'll borrow on JMS' own extrapolations: If we consider that the fuel in question will be used in diesel fusion engines, as a mixture capable of providing around 100-280 TJ/kg, then 9.9 e11 kg would provide a total of 100-280 e23 J a year, or an average consumption of 316.887-887.285 PW over the entire main battle fleet.

As per the ISB, "a fleet is designed as a sector resource," and the smallest fleet unit is a superioty fleet, which comprises 6 Star Destroyers plus 390 other combat ships, and used in calm sectors.
This brings us to a total of 396 ships. Not counting other support ships and small attack crafts which are not counted as capital ships.
The description of assault fleets makes me think they're added to superiority fleets, since they're said to be used when superiority is precisely challenged. It counts 375 ships, no mention of ISDs.
Bombard fleets count 416 ships, and are the big muscles, used to level worlds.

Rather interestingly, we see that with those numbers, the average power consumption per ship comes around one digit petawatt at best, then falls under the petawatt range for the low end fuel energy density.
If we're dealing with a complete typical sector fleet, we'll have several thousand combat ships, which will bring down the figure into the terawatt range, no matter the initial value that's used.

That said, it's also an average, so the smaller capital ships will fall below that figure, and bigger ships like ISDs will reach above.
Also, the fuel in question may have some exotic properties that would allow it to possess a greater energy density than previously thought, but it couldn't be excessive. After all, one of the engine pods survived against the explosion of at least one of those spheres filled with high-grade fuel.

If the fuel hold in containers used to destroy a Republican outpost in the early TCWS episodes is anything to go by (Rookies I think), the energy density isn't exactly spectacular at all, and would even fall way below the energy density I used for my figures. That said, merely placing detonators on the side of a container would not logically allow the fuel to release any energy if it's meant to be used in a fusion furnace. But we know starship high-grade fuel is flammable, so there's something to work with here.

On the other hand, the efficiency used for that diesel fusion model is particularly high. Very high.

On a different note, the fuel is said to be used for starship power cells. I know the terms "fuel cells" can be applied to current avionics, but I always considered power cells to be batteries.
It would be logical, then, to think that the fuel is used to produce the energy which the power cells will be charged up with. That would fit both references from that RPG supplement.

I am sure there are several opportunities to joyfully explore here to recoup this info with other information from the EU and higher canon about a capital starship's range.