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Invictus class weight questions

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Invictus class weight questions
Post by BrigadeΔ   » Wed Jun 22, 2016 9:39 am

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According to Wikipedia an invictus class podnaught can carry 1074 pods, assuming these are mk 23 flat pack pods that is 10,740 missiles which weight 94 tons per missile. Assuming that the pod itself, mass driver and all weighs nothing that is 1,009,560 tons of missiles. Or about 10% of the ships weight assuming the 8,786,500 tons of an invictus given on the wiki is the weight with no missiles if this is so a fully loaded one weighs at least 9,796,060 tons and probably weighs more then 10,000,000 tons with the pods weight included. If this is loaded weight then a podnaught with no missiles but that still has pods weighs 7,776,940 tons. Either way missiles are about 10% of the ships weight. F=M/A still seems to apply to inertial compensation in the honorverse to some extent, if a ship uses all of it's missiles why do they not seem to get faster? The acceleration at 80% power does not seem to change between full and empty and also, why does putting pods inside a ships wedge help with acceleration, the possible acceleration of an impeller wedge is apparently nearly infinite while inertial compensation is not so why does bringing more mass inside your inertial compensation field and making it work harder make you able to go faster?
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Re: Invictus class weight questions
Post by The E   » Wed Jun 22, 2016 9:51 am

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Compensator efficiency is tied to the volume of the ship, not its mass.
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Re: Invictus class weight questions
Post by Weird Harold   » Wed Jun 22, 2016 10:19 am

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BrigadeΔ wrote:... ships weight assuming the 8,786,500 tons of an invictus given on the wiki ...


Bad assumption: That is the displacement, not the weight. (or more accurately, mass.) As The E noted, it is a measure of volume, not mass.
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Re: Invictus class weight questions
Post by Lord Skimper   » Wed Jun 22, 2016 10:24 am

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It gets all screwy in the tonnage of the LAC's. A Shrika has less tonnage than a 282 and it is less than a Highlander.
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Re: Invictus class weight questions
Post by BrigadeΔ   » Wed Jun 22, 2016 10:28 am

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Weird Harold wrote:
BrigadeΔ wrote:... ships weight assuming the 8,786,500 tons of an invictus given on the wiki ...


Bad assumption: That is the displacement, not the weight. (or more accurately, mass.) As The E noted, it is a measure of volume, not mass.

So in the 44th century they classify ships by how much water they would displace? Why not just say Cubic meters?
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Re: Invictus class weight questions
Post by Weird Harold   » Wed Jun 22, 2016 10:34 am

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BrigadeΔ wrote:Bad assumption: That is the displacement, not the weight. (or more accurately, mass.) As The E noted, it is a measure of volume, not mass.

So in the 44th century they classify ships by how much water they would displace? Why not just say Cubic meters?[/quote]

That would be a question to ask RFC. FWIW, read up on the "Great Resizing" for the exact fluid used for figuring displacement of spaceships; it isn't water is all I remember.
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Re: Invictus class weight questions
Post by Theemile   » Wed Jun 22, 2016 11:58 am

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BrigadeΔ wrote:According to Wikipedia an invictus class podnaught can carry 1074 pods, assuming these are mk 23 flat pack pods that is 10,740 missiles which weight 94 tons per missile. Assuming that the pod itself, mass driver and all weighs nothing that is 1,009,560 tons of missiles. Or about 10% of the ships weight assuming the 8,786,500 tons of an invictus given on the wiki is the weight with no missiles if this is so a fully loaded one weighs at least 9,796,060 tons and probably weighs more then 10,000,000 tons with the pods weight included. If this is loaded weight then a podnaught with no missiles but that still has pods weighs 7,776,940 tons. Either way missiles are about 10% of the ships weight. F=M/A still seems to apply to inertial compensation in the honorverse to some extent, if a ship uses all of it's missiles why do they not seem to get faster? The acceleration at 80% power does not seem to change between full and empty and also, why does putting pods inside a ships wedge help with acceleration, the possible acceleration of an impeller wedge is apparently nearly infinite while inertial compensation is not so why does bringing more mass inside your inertial compensation field and making it work harder make you able to go faster?


We don't have a mass on the MK 23. The Mk 16 DDM masses 94 Tons.

The accel issue has been mentioned before and the answer is evident if you have Jayne's PRN. Both Mars A and B are shown in the issue and both have vastly different masses (the B model masses 25,500 tons more), though the same exterior dimensions.

Simply, the mass is not the factor which is compensated - it is the volume that is the factor being compensated. A more massive ship USUALLY takes up a larger volume, requiring a larger compensator - the mass is rather pointless, as long as it fits in the volume being compensated. The modern LACs, which have a higher density than normal starships because they do not have many internal spaces, have smaller external dimensions, and the higher compensation factor that allows.

In the side "Manticore Ascendant" series, there is a thread throughout the first book about ship compensation. Namely, ships at the time were designed to have a spin section to simulate gravity. This required a different compensation field shape to include the protruding spin section - but the maximum accel for this field shape was less than the modern spindle shaped ships. So it is possible to have different shapes to the compensated field, but they will be less efficient than the maximum the spindle shape allows.

If you notice, Jonathan S and I have occasionally spoke of Manticore's CLACs, whose dimensions are "fat" in comparison to a normal dreadnaught of the same size. They also seem to have a lower accel than the mass curve would suggest, meaning their designers accepted a less efficient compensator to get that width in a smaller ship than normal.
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Re: Invictus class weight questions
Post by Jonathan_S   » Wed Jun 22, 2016 12:27 pm

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Theemile wrote:If you notice, Jonathan S and I have occasionally spoke of Manticore's CLACs, whose dimensions are "fat" in comparison to a normal dreadnaught of the same size. They also seem to have a lower accel than the mass curve would suggest, meaning their designers accepted a less efficient compensator to get that width in a smaller ship than normal.
Yep, Tom Pope (head of BuNine) informally agreed that he seemed to recall that that hull form was at least part of the reason for their lower accel listed in House of Steel (compared to same-year classes).



Though comparing post-Grayson compensator acceleration rates is tricky because House of Steel has some gotchas in it. Ship specs (unless otherwise noted) are "as designed", not as built. And this include its acceleration; when the plans were made that's what a then current compensator could give on that displacement.

However when there was a delay between design and introduction to service even the lead ship might have gotten a better compensator than existed when the plans were drawn up (and nothing in HoS talks about what a given class might do "today" if they'd gotten refit with a newer gen compensator - we see ships in the books that a quicker than HoS's design specs - the advantages of updating to newer hardware). Now if HoS listed design dates (and we could assume every warship designed in a given year used the same generation of compensator) we could still do head to head comparisons. (Even better would be if compensator generation was an explicitly listed spec) But since we don't have that info you're stuck with a situation when two ship classes introduced in the same year might have several generations difference in their compensators - so their acceleration data can't be directly compared. We can't know 100% if the ship has lower accel because of some intrinsic factor in its hull shape, or because it was designed with an older gen (less efficient) compensator.


(Sorry for the info dump - I once spend way too much time reverse engineering the compensator curves and then stumbling over extending them to post-Grayson designs. I ended up having to take it on faith that the newer compensators were just a linear improvement because I didn't have enough data points to even really spot check their fit)
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Re: Invictus class weight questions
Post by Kytheros   » Wed Jun 22, 2016 8:52 pm

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The Impeller Drive and the associated inertial compensation appear to work similarly to an Alcubierre Warp Drive.

It's not exerting force on the ship itself, it's manipulating space-time around the ship.
Mass of ship is thus irrelevant - only how much space-time needs to be manipulated matters.
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Re: Invictus class weight questions
Post by pnakasone   » Wed Jun 22, 2016 9:29 pm

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BrigadeΔ wrote:So in the 44th century they classify ships by how much water they would displace? Why not just say Cubic meters?


Tradition can be a very strong force even when it no longer makes any sense to do so.

The real reason is so that we can look up real world ships as examples of what ships of various sizes look like.
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