Here comes a new batch of quotations.
p. 26 wrote:
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.
p. 27 wrote:
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.
p. 31 wrote:
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."
p. 36 wrote:
"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:
p. 37 wrote:
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:
Imperial Sourcebook, Fleet chapter, p. 108 wrote:
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.