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Efficiency of planetoids as ships?

Fans of Colin Maclntyre and the great starship Dahak should take a minute to stop in here for discussions about one of David's best-loved series.
Efficiency of planetoids as ships?
Post by Belial666   » Sat Jan 25, 2014 7:04 am

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They are horribly inefficient IMHO. Consider this; Dahak is a million times the size/mass of one of the evil alien command ships. It is eighty trillion times the size/mass of a megaton-range battleship.

Even a sublight parasite way below the 1-megaton mark can fire Hyper missiles and take at least one hit from such a missile without being destroyed (evidence: Heirs of Empire). Taking only the most important resource into account -crew- you could build ten thousand parasites for every Dahak, with much less than a billionth the industrial resources. In a Dahak vs smaller ships battle, the smaller ships fire, say, 10 hyper-missiles each in a salvo. Dahak is targeted with 100.000 hyper missiles at once. 1% hits and a thousand gravitonic warheads overwhelm its shields and obliterate it.





So why did the Imperium ever start building planetoids? They're a huge waste of resources IMHO.
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Re: Efficiency of planetoids as ships?
Post by jchilds   » Sat Jan 25, 2014 1:09 pm

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Some of the technology they prefer to use may have size minimums. The sub-light parasites you mention don't seem to mount things like core taps, Enchanach drives or hypercoms. Even if those installations aren't extremely massive, they may be volume intensive and/or require particular geometries - if say, Enchanach drive nodes need to be placed a minimum of 100 km away from each other and you need 12 of them to make it work, a smaller ship just won't work. FTL command and control and the reactive mobility to take advantage of it and a way to power both may have simply required ships that big.

There's also a logistics component. The planetoid size ships were designed to be capable of the power projection necessary to conduct search and hopefully destroy missions across a significant chunk of the galaxy - the Imperium simply miscalculated how far they needed to go to find the Achuultani. As a bonus, the planetoid ships were quite capable civilization sized lifeboats, in the event Battle Fleet wasn't up to taking out the Achuultani. Even if only one got away, Humanity could rise again.

One final thing to consider is that it's hard to judge, based on the existing textev, how efficient or inefficient Imperial doctrine actually is/was. We have not seen anything resembling one or more "fully armed and operational" planetoids with full crew and parasite complements in action.
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Re: Efficiency of planetoids as ships?
Post by munroburton   » Sat Jan 25, 2014 9:19 pm

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Contrast how 120 sublight BBs and a further 650 smaller parasites performed against 1728 Aku'Ultan ships during the Siege of Earth with the later clashes between the 60-odd planetoids and the 2.5 million strong Aku'Ultan fleets.

10,000 sublight parasites instead of a planetoid? Okay, that means 600,000 of them. If 770 vs 1728(1:2.2) is a losing proposition, then how is 600,000 vs 2,500,000(1:4.2) better?

Throw in the logistical nightmare of coordinating that many ships(the Aku'ultan split up into groups for a reason) and it's easier to see why a handful of planetoids beats an armada of fleets.

The way to approach is to look at what the designers were thinking of. Based on semi-apocryphal legends of previous Visits and with absolutely no real intelligence about the enemy, the Fourth Imperium had to push everything up to 11. Constantly.

Given time and better bio-filters, they might have eventually ended up building mobile Dyson spheres. Of ever-increasing size...

http://www.youtube.com/watch?v=IJJEMmzKzR4
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Re: Efficiency of planetoids as ships?
Post by cralkhi   » Sun Jan 26, 2014 2:54 am

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Maybe it's a core tap thing. Dahak might be mostly hollow. They were really worried about the Indian Ocean being affected by an Antarctic core tap failure, so if you put everything important a thousand+ miles from the core tap... you start getting into Dahak size ranges.


munroburton wrote: and with absolutely no real intelligence about the enemy, the Fourth Imperium had to push everything up to 11. Constantly.



Well... I do kind of wonder about this because several times in TAI Dahak does display some significant knowledge, e.g. when he's able to identify Sheskar's ruins as not being Achuultani-caused. So he knows they don't have gravitonic weapons.

There's also a statement that the force was twice as big as expected -- in the Siege of Earth, it's stated that they've killed nine-hundred-something Achuultani ships, which should have been all of them. That's before Dahak cracks the captured Achuultani computers, so they must have known the normal size of a Great Visit beforehand.

And that may be the answer to the original question. If they knew the normal size of a Great Visit, even multiplying by a hundred to be super-safe doesn't get you remotely close to a million planetoids (with proper resupply, Colin's ships would have done much better; so 10,000 should have easily trounced an Achuultani force fifty times bigger than what we saw in the books=100x standard). So efficiency clearly wasn't really a concern...
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Re: Efficiency of planetoids as ships?
Post by Garth 2   » Sun Jan 26, 2014 6:41 am

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not really, with out some better understanding of the technology limits e.g. volume, mass, capability, power demands, material requirements etc. its very hard to make an informed choice.

The planetoids shape does give a major advantage in space combat, it can fire energy weapons and missiles in any direction with minimum movement.

The size of the ship, is probably a result of the equipment and the number of personnel its carrying. After all missile combat seems to be the main mechanism in this verse and therefore you need very large magazines (pushing up the size of the ship).

Though of course it could have been just a repeat of previous Imperium's/Empire's designs without actually wondering if it was the right one.
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Re: Efficiency of planetoids as ships?
Post by saber964   » Sat Feb 15, 2014 7:05 pm

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Here is something else to consider, with spherical planetoids you can rotate on any axis and rotate battle damage away from incoming fire and have time for repairs and prevent concentration of fire on previously damaged areas. IIRC during one of the battles a planetoid took a hit on a hit. This would lesson the chance of this happening.
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Re: Efficiency of planetoids as ships?
Post by Talonvor   » Tue Mar 18, 2014 12:52 pm

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Belial666 wrote:So why did the Imperium ever start building planetoids? They're a huge waste of resources IMHO.


Why did they build them? Because the engineering components require a massive amount of space. If you remember correctly when they were inspecting the ships of the emperors fleet they were shocked to find that the ships carried both hyper drive and enchanch engineered down to the size of Dahaks own enchanach drive.

Then there is the crew to think about. The ships were designed to carry 200,000+ crewmen. The area required for berthing, storage, entertainment, care and feeding of those crewmen would be massive. You also have to add into that the space needed for hydroponics, because the ships grew their own food.

After that comes the weapon systems. The energy weapons take up a lot of space, as do the launchers and ammunition storage. We never get hard numbers on the total amount of ammunition storage a planetoid has, but based on the sheer number of missiles fired during the engagements with the Achuultani in The Armageddon Inheritance, they would have to carry hundreds of thousands of missiles if not more. We know that capital missiles are massive because Horus tells us the size of those missiles and they are massive. Several meters long and a couple wide, which means that storage for those missiles and the equipment required to move the missiles from the magazines to the required launcher would take up more space than any other component.

Finally there are the sensors, parasites and their related equipment.

Based on all of those things, I am amazed that the ships aren't larger than they actually are.
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Re: Efficiency of planetoids as ships?
Post by svenhauke   » Fri Jul 11, 2014 8:12 pm

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armor ...

having 500km of outer armor is nice

id say it allows survival against weapons that would destroy ... anything else

so efficency gets a new perspective

as theres simply nothing else that can survive and keep fighting

with bigger weapons that can destroy more

i personaly belive in bigger is better
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Re: Efficiency of planetoids as ships?
Post by niethil   » Mon Jul 21, 2014 2:26 pm

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The ships were designed to carry 200,000+ crewmen. The area required for berthing, storage, entertainment, care and feeding of those crewmen would be massive. You also have to add into that the space needed for hydroponics, because the ships grew their own food.


That, at least, is wrong : compared to Dahak's size, the space taken by 200,000 crewmen and their entire life support equipement is almost insignificant.
To get a better idea, 200,000 is approximately the population of the city of Paris alone around 1300. Let's be crazy and say that we need the entire French territory to support Paris at that time. We have to take into account that it was a 2.5D structure though, while Dahack is a 3D structure. If the volume of space necessary to support Paris was the surface of French territory multiplied by something like maybe 100 meters in height, it only amounts to something like 5x10^8x10^2 = 5x10^10 m³. To be compared with Dahak's volume being well in excess of 4*(10^6)^3 = 4x10^18 m³.
So the volume of space required for the crew is probably on the order of 10 billionths of Dahack's volume. And the back of my envelope is screaming "hugely biased upward" back at me.

So, no, the size of the crew is not an acceptable explanation for Dahak's size, I believe.
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'Oh, oh' he said in English. Evidently, he had completely mastered that language.
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Re: Efficiency of planetoids as ships?
Post by JohnS   » Mon Jul 21, 2014 9:13 pm

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svenhauke wrote:armor ...

having 500km of outer armor is nice

id say it allows survival against weapons that would destroy ... anything else

so efficency gets a new perspective

as theres simply nothing else that can survive and keep fighting

with bigger weapons that can destroy more

i personaly belive in bigger is better

So very true. Here's a quote from Armageddon Inheritance (bolding my own):
Alarms screamed as a ten-thousand-megaton warhead exploded almost on top of Royal Birhat. The huge ship quivered as the furious plasma cloud carved an incandescent chasm twenty kilometers into her armored hull. Air exploded from the dreadful wound, blast doors slammed . . . and Birhat went right on fighting.

"Moderate damage to Quadrant Theta-Two," the sexy contralto said calmly. "Four fatalities. Point zero-four-two percent combat impairment."

At the battle of Earth, an entire Achuultani ship was twenty kilometers long. If I was going to be in a desperate battle, I know which one I want to be riding in!
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