Reconstructing the 400 Td SDB in MT

[Major B]

This discussion convinced me to give another try at converting CT ship designs to MT. I had run into the snags others have described in the Ship Design thread when trying to convert CT ships and finally gave it up to focus on some new vehicles for my next campaign. I was struggling to design a communication and SIGINT unmanned vehicle and found the idea of multiple power plants in the above thread. Getting that idea to finally work right convinced me to try again with converting the CT 400 Td System Defense Boat from Supplement 7 to MT statistics.

This link shows the (expanded) UCP for what I came up with. (edit: changed link to go to file library)

I was able to get what I think is a pretty good approximation of the CT design. All around it is a good (not great) TL12 design for what the vessel is intended for. If I was designing from scratch I would do many things differently, but the point of this exercise was to try to recreate the original...

Here is a list of the things I considered and what came up in the process (not in any particular order):

- Using the MT crew calculations I have a crew of 12 when the original had ten. I kept the individual staterooms for each crew member so they will have some privacy on long patrols.

- I was only able to save 10.6 Td for cargo space – the original had 27 Td for cargo.

- I counted 4 air locks in the drawing in Supplement 7 so went with that for this one. The drawing isn’t the best reference though as it doesn’t show the ten staterooms the text says are there.

- I put basic environment, grav plates, and inertial compensators in the entire hull. Basic and extended life support are in all of the hull except the fuel tankage, saving a little space, weight, and expense. - I kept the same weapon mix as the original. For the missile magazine I guessed at an appropriate number to be 30 battery-rounds and used nuclear missiles to calculate the space and weight (HE missiles take up the same volume but weigh less).

- I kept the model 5/fib computer and installed two backups. I don’t remember any mention of backups in Supplement 7 but it may have been somewhere else.

- I had heads-up holodisplays for all 12 crew stations and then realized they were not available until TL13. I also had to switch from holographic linked control panels to Dynamic linked for the same reason. I decided to put a large holodisplay on the bridge and another in engineering and gave regular (non-holo) heads-up displays to each of the two gunners. This gave me well over the required control points and actually saved me almost MCr2 off the total price. IIRC the cost of this will be a reduction in the tactics pool available for the vessel.

- Total cost for the original was MCr 777.54 and mine came out to MCr 790.76 so I came out pretty close.

- I took a SWAG (scientific wild-assed guess) at the sensors and electronics, taking the best available at TL12 but restricting range to in-system. I also installed a commo suite of four systems; 2 maser, 1 laser, 1 radio to keep with what I learned early in the Army - to plan commo using the PACE acronym (Primary, Alternate, Contingency, Emergency).

- I had to SWAG at the armor value too. The original had armor 9. I doubled that and added 40 for an armor value of 58. I tried higher values (the starship design example tripled the LBB5 armor value) but was struggling with the agility so had to keep it lower.

- I thought the maneuver drives were huge until I started trying to figure the power requirements. Powering the maneuver drive itself was easy but there was no way to get the agility up to 6 because the power plant by itself exceeded the available hull space and that was without putting in any fuel. First I separated out the power plant into five pieces (this made it easier to calculate the fuel requirements later). I made one plant to provide half the base power needed by the 6G maneuver drive (giving the vessel 3G and agility-0 for cruising). Then I made another plant for the additional power required for combat maneuver (the other half of the 6G m-drive’s minimum power and all of the excess power to provide agility). For the combat drive I built in a meaningless variable (in the ‘f’ column) just so I could go back later and make adjustments without having to mess with the formulas. Then I made drives for the weapons, sensors/commo, and life support/bridge. Last, I put in the fuel tankage for each of the drives and used column ‘f’ for hours of operation (so I could fiddle with the endurance and see the results). Note that I could have simplified this with just two power plants (one for cruising and one for combat), but that is hindsight. I’ll remember that next time.

- When I adjusted the variables on the combat drive and hour settings on the fuel tanks to get the best fit, I came up with 360 hours (15 days) of endurance for cruising and 24 hours for combat maneuver and weapons. The best agility I was able to get was 2.6 because I wanted to maximize endurance and still maintain some cargo space. Also, bumping up the engine size not too much more than they are now added an extra engineer and a maintenance crewmember (and two staterooms) so I kept what I had.

- I think I should point out that I don’t think the vessel would have five different power plants. Calculating the separate power plant requirements is only a tool to calculate the required fuel correctly. I think this vessel has one power plant capable of producing 15,652.64 Mw at full capacity, but for normal (cruising) operations it is powered-down to only produce 2,789.28 Mw.

This is a link to the worksheet showing all of the calculations as they stand right now. I hope the example is instructive and I would like to hear any constructive feedback or suggestions that will bring this closer to the CT design. Again, I could probably have come up with a better-performing design if I had started from scratch rather than trying to recreate the CT vessel, but this was something I wanted to try just to see how close I could get.

Anyway, enough for now. If anyone would like a copy of the spreadsheet send me a PM with your e-mail address. It doesn’t calculate everything I want it to yet (it will continue to evolve) but I’ll gladly provide it to anyone who can make use of it. The only cost is that I’ll expect feedback for proposed improvements.

 

[Major B]

Just as additional food for thought, here is a list of some shortcomings of this design (that I'll try to correct when I design another from scratch):

- There is no launch/ships boat. The description in Supplement 7 said that one of the uses of an SDB was for customs inspections but that would be difficult when the only way to get between ships was EVA. I'd think the boat itself would prefer to stand off (in overwatch) rather than docking with the vessel to be boarded for inspection.

- The design should be configurable for the different missions the boat will be used for. Maybe build in the ability to plug a berthing/equipment module into the cargo hold so a Customs Inspection boarding team can be placed onboard for the customs mission. Or to add a Marine fire team to support anti-piracy missions. Search and Rescue would require some specialized gear, maybe a treatment bay, and emergency medical personnel.

- Other than the armoring, the vessel lacks defensive thought. Well, at least the re-calculation of it does. If stuck with the same hull volume I think I'd drop the M-drive down a G or two in order to increase the agility (and get a bigger Def DM). I'd also consider trading a laser turret in for a triple sandcaster to give it better survivability. Have to balance the loss of firepower versus the protection gained to see if it is worth the trade, but something to consider.

- The separate staterooms are a nice touch for the crew but it may be an unaffordable luxury until higher tech levels. Double occupancy staterooms are a better use of the available space. Maybe it would be better to divide the extra space - half devoted to additional fuel and the other half to crew recreational space to help alleviate morale difficulties.

 

[far-trader]

Just a few thoughts re the first post (haven't looked at the second one yet), for what they're worth (I'm always glad to see another gearhead struggling to make things work )

Re the crew, it's been a while since I've played with MT so I'm foggy on details but could any of the crew positions be doubled up to get it back to 10?.

Re cargo, no biggie really, as a combat vessel doesn't really need it. But, in the PC's world cargo is one of the most important items, so it'd be nice to see that retained at spec.

Re airlocks, did you count the total squares to arrive at the airlock sizes? If not try that way. If you did, divide it by two (just a guess since many deckplans are over by that factor).

Same for staterooms. Check the total shown tonnage, including common areas, and you'll probably find more than the 40dtons it should be. Even more than the +10% allowance. I also think the "staterooms" were creatively interpreted in this design (well within the rules) so you have officers with nice quarters and an office, while the ratings have cramped bunk rooms. My take on the assignment of quarters is:

Rooms 1 and 2 are the Nav/Medic* and Chief Engineer (junior officers) staterooms.

* really just Medic imo

Rooms 3 and 9 are the ratings bunk rooms.

Room 7 is the sickbay.

Room 5 is the Pilot (officer) stateroom.

Room 6 is the wardroom.

Re environ etc I always worked it out for the full hull just as an easy way of doing it and rationalized that it had to be done or you'd have issues. Like without inertial comp in the fuel tanks what do you do when you're swinging 6g around and the fuel all goes flying one way while you want to go another. And without basics in all areas you can't perform routine maintenance. The savings are so small and the reasons and ease outweigh that, for me anyway.

Re the missile magazine. 30 battery rounds is probably way too much, especially for such a small ship. Battle lifetime I once figured at typically less than (don't recall the actual number but it was low in most cases) 6 combat turns (win or lose) so anything more than that is superfluous in all but a design expected to make repeated guerrilla strikes without resupply. Which may actually be part of the role of the SDB so I can see an exception. But don't forget you also need the life support supplies (cargo space) to pull that off too. I'd probably figure on no more than 6 months deployment and maybe 12 battery rounds.

EDIT: Same for combat power duration, 24 hours seems excessive, 3 hours would be lots. Think long quiet lurking or slow steady patrols, with short occasional combat strikes. Maybe that'll help you get back some cargo and agility?

No backup computers in CT, though the rules for damage are different than MT (iirc). I think I treated the CT single computer as equal to the MT/TNE triple redundant system.

Everything else looks pretty well thought out as well and much the way I'd have gone. Gotta agree too that the multiple powerplants and endurance as a calculation ease (rather than actual physical reality) is the way to go too.

 

[Major B]

Thanks for the feedback far-trader.

On the room assignments, I had similar ideas except the sickbay was in room 23 on the lower level and I had 5 pegged as the CO's cabin since it didn't open out into the rest of the ship (so the exec or senior chief can screen access to the boss).

On the environments, I only removed life support from the fuel tanks. There is still basic environment, grav, and inertial comp throughout the hull. Yes, the savings aren't much but every little bit counts and I thought that not having life support in the tanks might take some complication out of refueling. Not that important though, either way.

The reduced missiles make sense, especially given the mention in the text about prepositioning reloads in the asteroid belt. Reducing the combat power hours makes sense too. It would drive the ships to use some sort of "shoot and scoot" tactics rather than stand and fight long engagements which is in keeping with their design intent, I think.

I'm doing some re-working based on your feedback and also consolidating the power plants into just two to make things simpler. I'll post the new sheets when they are done.

 

[far-trader]

...except the sickbay was in room 23 on the lower level...

D'oh, that's right it is there

Always seemed an awkward place for it though. I think I may have made 23 and 24 ship's stores (cargo). I don't recall. Be nice if the canon source had labeled all the numbered features in all the designs instead of missing so many

You're welcome for anything in my shoot from the hip rambling that might have accidentally helped

 

[Major B]

Far-trader, that worked out better than I'd hoped.

- I condensed the power plants into two - had some spread sheet issues to overcome there because all the calculations produced a circular error. I also noticed that I was missing part of the fuel tankage when calculating the hull volume requiring life support so I saved some space there.

- I split the staterooms making 4 single-occupant and four double-occupant for a total of 12 personnel.

- Reducing the missile magazine to 12 battery-rounds freed up more space. I also reduced the combat fuel load to 6 hours. Three hours seemed too short for me. Guess that's my infantry upbringing coming out - its hard for me to decide how much ammo or fuel is enough because I always want more.

- All this allowed me to increase to 20 days cruising endurance and retained 24.1 Td for cargo. Big difference and at reduced cost - the new total is MCr 788.15 versus 790.75 prior to these changes.

I'll scan the new worksheet and post it some time over the weekend.

Thanks again.

 

[far-trader]

Sounds good Yeah, I was thinking right after posting the 3 hour suggestion that's not a lot of dashing about time if you get into a chase scenario, and like you I usually don't mind extra* "expendables" just in case

* there's the low of minimum projected, an average of routinely expected and the high of more is never too much right

 

[Major B]

Something like that but for me it was usually easier because it boiled down to the decision you make when you pack your ruck...

Then again, those decisions were easier back in the day - when in training, the ammo pouches have everything but ammo in them.

 

[Major B]

I finally posted the UCP and worksheet showing the revisions.

Here is the UCP (expanded). (edit: link now leads to file library)

I call it the expanded UCP because I have some extra stuff in there that I really need to put somewhere else. I plan to make some changes to the spreadsheet so it provides a better play aid. I should probably do that before I mess around with the design any more.

Here is the design worksheet. This shows the reduction in calculations to just "two" power plants and the fuel requirements calculated from that. (edit: link now leads to file library)

I'm still not happy with the low agility but when I added to the power plant it generated a requirement for one additional engineer and one more member of the command crew. I guess I'll have to keep at it until I get something closer to the original.

 

[Major B]

Version 3 posted in the file library

I recently re-tooled the spreadsheet I’ve been using to design vehicles and ships and used the new format to revisit the SDB conversion. I was able to eke out more performance from the version 2 conversion I posted earlier.

By the way, I recently shut down the web site I was beginning to build because I didn’t like the advertisers there. I’ll probably rebuild it on a different host later but it will have to wait at least until after I move to Austin this summer. If anyone wants to compare this effort with my earlier effort, I’ve posted the second version and this third version in the file library here.

The most significant change between v2 and v3 is that I was able to get the ship up to an agility rating of 3. I had to use separate fuel calculations for normal maneuver, combat maneuver, and combat weapons power plants to accomplish that within the 400 Td hull. Now, over half of the vessel’s volume (2982 kl) is devoted just to the power plant although only roughly 10.1% of that plant’s capacity is used for normal maneuver and day-to-day ship’s systems.

To make space for the increased power plant and fuel, a number of adjustments were necessary. The most significant of these adjustments was the decrease in crew requirements realized by increasing the computer from a Mod 5 to a Mod 6. This cut the required crew from 14 down to 11 and saved a significant amount of accommodation space. Using small staterooms for two crewmembers and reducing the number of airlocks from 4 to 2 saved more space.

The vessel can operate in normal conditions (up to 2G, 0 agility) for 30 days with a 12-hour fuel reserve for combat maneuver and to power the laser turrets. Note that these endurance calculations are just a potential allocation, not a hard and fast limit. The vessel has a total of 748.9 kl of fuel so it can operate continuously at normal maneuver power for about 826.5 hours or 34.4 days. However, I’d think responsible commanders would only do this in extreme cases and would normally top off at every opportunity in order to be prepared for a long high-G burn if needed. Alternatively, the vessel could operate on combat maneuver power for 48 hours straight and still have 382.4 hours or just under 16 days normal maneuver endurance left over.

It has the best sensors available at TL12, retains the 6G thrust of the original (even though the agility is only 3), and has a respectable defensive DM of +10. Its armor DM of -6 offsets somewhat the lack of screens. However, there is no practical cargo space, with only .187 kl of unused space in the hull. This is because all available space is allocated to fuel tankage, which incidentally was another space savings as there is no life support installed in the fuel tanks.

Crew quarters are adequate with the commander and pilots in private staterooms while the junior officers and enlisted ratings are in double occupancy. Control requirements are more than met with two large holodisplays (one on the bridge and one in engineering) and two HUDs (for the gunners). The main drawback to this version is the costs associated with all of these changes – the vessel now costs MCr 850.66 where the original version in Supplement 7 cost MCr 777.54.

Although the converted design as it stands is a credible threat given the constraints inherent in a TL12 design, I think that upgrading the design to TL13 would result in a much more capable vessel. The weapons would both go up a UCP factor (from 3 to 4). The power plant multiple also increases from 2 to 3 so the power plant will require less space. This would be offset a little by the increased fuel consumption (.003 kl/hour increases to .005) but the smaller power plant may be enough to bump agility up to 4 or maybe higher.

I may work out an adjusted design to see the differences, but I have some original ships that I want to try first. I really intended this project to be practice before I designed some new vessels, so if any one sees any holes in this conversion please let me know.

 

[sfchbryan]

This is really, really good.

So when can you have FSOSI redone?........ :smirk:

 

[Major B]

This is really, really good.

So when can you have FSOSI redone?........

Didn't you say in another thread something about only giving that project to someone you don't like?

Seriously, that is part of the reason I got started with this project - I want to build stuff for players to use and want to be sure its done right.

But I'd kind of like to build up to redoing FSOSI, so let me try some other smaller designs first.

 

[Major B]

I've just posted the 4th version of the SDB conversion in the File Library.

This is the final version, unless someone spots something I left out or calculated wrong.

The main changes to this version are:

- Put back the electronic circuit protection that I somehow missed in version 3.
- reduced the commander's cabin to a small stateroom to accomodate the space taken by the circuit protection.
- added an illustration to the UCP that was kindly provided by Andrew Boulton.

I've started to work on converting the Kinunir for my next project. It is fitting together much more easily than the SDB did, but that is probably because it is a TL15 design. I'll post the results soon.