Newbie question about ship engines

[Jumpp (OP)]

Hi guys.   I'm real new so I apologize if this is in a FAQ somewhere.   I couldn't find it, but I might not know where to look:

I just got Magneto-plasma drive tech, and I'm designing a new line of engines to use it.   I'm going to do a 10,000-ton missile cruiser, and I want it to do around 2,500 kps with a range of 50 billion km.   I did a little spreadsheet to help me choose the efficiency setting that'll minimize the amount of tonnage I spend on engine and fuel.

That spreadsheet is telling me that what I want to do is a single size-32 512-EP engine with a power mod of 1. 00.   (Actually, it's telling me to go for 1. 05, but I don't have the tech for that. )

I was thinking I might save some research time by using the same drive in my 5,000-ton escorts and the 10,000-ton cruiser, and just use two of them in the cruiser.   That cuts the research load way down.   Spreadsheet says to make a size-20 256-EP engine with a power mod of 0. 8 in that case.

Now, if I use two of those smaller engines instead of one bigger one, I lose around 600 tons, but that's not the end of the world.

I notice that nobody does this single-engine thing.   When I look at people's sample designs, I usually see large stacks of smallish engines.   One guy, who seemed to really know what he was talking about, had 17 smaller engines on one of his monster ships.

So my question is: What does everyone else know that I don't know?  Is this about battle damage?  Is a one-engine ship more vulnerable to crippling failures?  Is this about not wanting to spend piles of RP on the larger engines?

[icecoldblood]

Single engine ships have the chance of being diabled by one lucky meson shot. Its also because smaller engines can be used on more ships a very large engine (32hs in your case) will only be used  on a few large ships and also makes fine tuning your ships engine power to size ratio impossible. Also, if you intend to have ships of different sizes, you're going to need to have several different engines. The large rp cost is also a major disadvantage. imagine waiting several years just for the engine every time you complete the next engine tech.

[Charlie Beeler]

Just to add a little to this.

Odds are that most of those other designs you've been looking at are from games prior to v6.0.  V6.0 has a major change to engines.  Those changes take some time for various players to find what they consider optimal design protocols. 

[metalax]

I've certainly been running with the single large engine, as the fuel efficiency compared to multiple smaller ones is quite noticeable. A single size 50 engine is just the right size for a destroyer at 25% of it's tonnage. Smaller engines are typically only much use for fighters and gunboats. I suppose if you regularly fight using little "toy boats" for your ships then smaller engines may be usefull.

I've never found the research costs particularly excessive, although that may be because I've almost invariably had some good propulsion scientists and push the research multiplier up early.

[Conscript Gary]

Yeah, I bet a lot of those designs are simply old.
In my current game I'm going with 25% engines by tonnage for my warships, and class sizes in increments of 6,000 tons. So a single size-30 engine serves the majority of my fleet, just using two in the vessels twice as large and so on like you are.
As for survivability, I had a carrier with four of those engines overcome by a horse of meson-armed craft, and the engines lasted longer than everything else despite taking a dozen hits.

[Prince of Space]

I did a little spreadsheet to help me choose the efficiency setting that'll minimize the amount of tonnage I spend on engine and fuel. 

Could you share your math with us? This sounds useful.

[Jumpp (OP)]

Could you share your math with us? This sounds useful. 

Sure.

It's pretty raw.   You know how it is when you're quickly cobbling together a tool for your own use, rather than something that's presentable for the public.   Also, I've only played this game for about 50 hours so far so I'm super new and it's very likely I've made serious errors here.

With all that said, here's the link:

Code: [Select]

https://docs.google.com/spreadsheet/ccc?key=0AkCOvP4HxWr-dG54NGpKdVUwc05VWldjLUNidFpTQ3c

[Prince of Space]

My google-fu is weak, at least with google docs. I was unable to view or copy the formulas out of your spreadsheet, but I was able to reverse engineer the math. It doesn't appear that your spreadsheet accounts for ships that would need multiple engines to acheive the desired speed. I think I've figured out how to do that, though. Attached is my revision of your work, prettied up a smidge with multiple engine compatibility.

I've kept your approach of specifying the available tech, the ship size, and the ship speed. This works well for designing ships whose tonnage you've already determined, like ships in a survey fleet who would ideally match their jump tender's size exactly. However, many of my commercial designs are as big as they need to be, tonnage budgeting be damned. I would have liked to design an alternate calculation that takes a specified non-engine, non-fuel tonnage and a specified speed, then outputs the combination that optimizes for minimum engine and fuel mass, but my attempts result in circular references and a headache.

So here's what I got. Maybe I'll come back to this in a week and crack that nut. If anybody finds an error, please let me know. Like I said, my eyes keep crossing as I review it at this point.

Edit: attachment troubles. Sigh.

Edit 2: Fixed it.

[niflheimr]

Attachment wont work - It only download a 0kb archive but based on the google doc sheet ... me likes. I've been manually getting the fuel/engine tonnage so far , this is way better

[Prince of Space]

Yeah I've been trying to figure out why it won't attach properly. I'll repost it when I figure it out.

When I initially looked at it I was intrigued, so I threw in the basic specs of a 150,000 freighter I was playing around with. That recommended engines that were bigger than 50 HS, so I tinkered and felt like sharing. Of course all this doesn't optimize for minimal fuel consumption or minimal construction cost, but it's all something for the admiralty to consider.

Edit: Attachment is fixed in original post.