Spirit of 1977
Cosmic Mongoose
This thread is in response to views that MegaTraveller (MT) made too many compromises from its Classic Traveller (CT) origins. Specifically, MT starship construction was initially based upon Book 5 High Guard (HG), but made many changes that did not sit well with many older players. While my initial view was that the MT changes were fine, I was intrigued enough to take up the challenge of trying to bring MT back to something more like HG. The results are very interesting, as I will show in future posts.
TL;DR: Unless you are very familiar with MegaTraveller and CT High Guard starship construction rules, you can safely ignore all of this!
In preparation for some example starships I will be posting based upon MegaTraveller (MT) rules but modified to retain as much of the CT High Guard (HG) rules as possible, these are the conversion rules I am using. You will need to be familiar with both HG and MT. I would appreciate any commentary or error detection so that I may incorporate them into my examples.
HG to MT assumptions (note that ton always means 1000 kg; the volume D-ton will always be specified and equals 13.5 kl):
1) Maneuver Drives (MD) and Power Plants (PP): HG assumes that MDs consume a certain volume of hull per G rating, and PPs of sufficient size will both power the MD and supply excess energy points (EP), and Striker tells us that 1 EP = 250 MW.
In MT, PPs supply some fixed amount of MWs. MDs are constructed from maneuver units with fixed parameters, except for the actual thrust produced. This is because MT wanted to maintain the MD = % of hull logic. We will dispose of this, and by consulting the grav drive data for vehicles, it is easy to see that a maneuver unit (anti-grav or thruster) produces 675 tons of thrust. We will then compute Gs of thrust as (tons of maneuver thrust)/(loaded craft tonnage). This produces interesting results, particularly at high TLs. Note that under this construction, 1G MDs may not be able to land on worlds with gravity > 1G, though Agility would allow it.
1a) Agility: HG Agility (<= max Gs of acceleration) = excess EPs per 100 D-tons of hull. MT Agility = 5.4 x excess MW / loaded tons. While these may seem unrelated, the MT formula is a completely faithful translation of the HG formula assuming that 1 D-ton in HG = 13.5 tons on average in MT. Thus the move from HG to MT is from volume to mass, which is appropriate, and all acceleration calculations in my examples use mass. This produces different results from HG, but they make sense (e.g., lower TL craft require larger PPs to obtain maximum Agility).
1b) Minimum PP Size: In HG, the PP number had to be the larger of the MD number or Jump number. To replicate this, the minimum size of the PP that powers the MD is 67.5 MW per MT jump unit. The PP is assumed to run while in jumpspace and reinforces a 30 day fuel requirement. Such a PP may have excess MWs vis a vis the MD and thus might add to Agility.
2) Fuel Usage: MT PP fuel consumption is much higher than HG, and so jump fuel was reduced to compensate. For these examples, we restore the HG jump fuel requirement of 10% hull volume x jump number. It turns out that once a MT PP is at least 1 D-ton and gets the full 3x efficiency bonus, MT PPs and HG PPs are almost identical with respect to MW, tons, and D-tons. Only fuel consumption is different: MT fusion PPs consume 6.67x the fuel of HG PPs. Thus, all that is required to replicate HG is to multiply MT fuel consumption by 0.15. I'm still debating whether this should apply to all fusion PPs, including vehicles, but I might do so given the alternative of fuel cells produces interesting tradeoffs (this is otherwise beyond the scope of this exercise).
3) Armor Volume: There is a strong view that armor ought to take up hull space. I'm adding this back though honestly it does not matter much for adventure class ships. It is likely much more meaningful for capital ships, which may feature in later examples.
In HG, armor A is a factor starting at 0. Armor takes up V(1+A)% of hull volume, where V=4 for TL 7-9, 3 for TL 10-11, 2 for TL 12-13, and 1 for TL 14-15. For MT, the minimum Armor Factor is 40 for spacecraft, corresponding to a mass multiplier of 33.6 for hard steel in Striker (and MT). Let A be our Armor Factor >40 and M the corresponding mass multiplier. Then armor takes up the following percentage of the hull: [8 x Armor Type Mass Multiplier x M/33.6]%. The corresponding V values for MT are 3.5 for TL 7, 2.8 for TL 9, 2.5 for TL 10, 2.1 for TL 12, and 1.1 for TL 14, so rather close overall and more generous at lower TLs. The advantage of this MT method is we can compute armor density and perhaps use that.
4) Bridge: HG imposed a 2% of hull volume bridge requirement, 20 D-tons minimum. I am using a more flexible rule via Duty Stations. A Duty Station is 2 D-tons (like a small stateroom), and all starships require a minimum of (10/active crew) Duty Stations. The active crew requirement is based upon the MT rules for crew count and could produce deviations from the 2% of hull requirement, which I think is fine given the better model of Duty Stations. But for ships <=1000 D-ton, the bridge is always 20 D-tons (10 Duty Stations).
5) Computers: HG computers were gigantic, likely including other systems like control panels, comms, and sensors. In MT, the latter systems are explicit and computers are much smaller. We use the MT rules without modification, which likely results in lower overall volume than HG.
Example starships are forthcoming!
TL;DR: Unless you are very familiar with MegaTraveller and CT High Guard starship construction rules, you can safely ignore all of this!
In preparation for some example starships I will be posting based upon MegaTraveller (MT) rules but modified to retain as much of the CT High Guard (HG) rules as possible, these are the conversion rules I am using. You will need to be familiar with both HG and MT. I would appreciate any commentary or error detection so that I may incorporate them into my examples.
HG to MT assumptions (note that ton always means 1000 kg; the volume D-ton will always be specified and equals 13.5 kl):
1) Maneuver Drives (MD) and Power Plants (PP): HG assumes that MDs consume a certain volume of hull per G rating, and PPs of sufficient size will both power the MD and supply excess energy points (EP), and Striker tells us that 1 EP = 250 MW.
In MT, PPs supply some fixed amount of MWs. MDs are constructed from maneuver units with fixed parameters, except for the actual thrust produced. This is because MT wanted to maintain the MD = % of hull logic. We will dispose of this, and by consulting the grav drive data for vehicles, it is easy to see that a maneuver unit (anti-grav or thruster) produces 675 tons of thrust. We will then compute Gs of thrust as (tons of maneuver thrust)/(loaded craft tonnage). This produces interesting results, particularly at high TLs. Note that under this construction, 1G MDs may not be able to land on worlds with gravity > 1G, though Agility would allow it.
1a) Agility: HG Agility (<= max Gs of acceleration) = excess EPs per 100 D-tons of hull. MT Agility = 5.4 x excess MW / loaded tons. While these may seem unrelated, the MT formula is a completely faithful translation of the HG formula assuming that 1 D-ton in HG = 13.5 tons on average in MT. Thus the move from HG to MT is from volume to mass, which is appropriate, and all acceleration calculations in my examples use mass. This produces different results from HG, but they make sense (e.g., lower TL craft require larger PPs to obtain maximum Agility).
1b) Minimum PP Size: In HG, the PP number had to be the larger of the MD number or Jump number. To replicate this, the minimum size of the PP that powers the MD is 67.5 MW per MT jump unit. The PP is assumed to run while in jumpspace and reinforces a 30 day fuel requirement. Such a PP may have excess MWs vis a vis the MD and thus might add to Agility.
2) Fuel Usage: MT PP fuel consumption is much higher than HG, and so jump fuel was reduced to compensate. For these examples, we restore the HG jump fuel requirement of 10% hull volume x jump number. It turns out that once a MT PP is at least 1 D-ton and gets the full 3x efficiency bonus, MT PPs and HG PPs are almost identical with respect to MW, tons, and D-tons. Only fuel consumption is different: MT fusion PPs consume 6.67x the fuel of HG PPs. Thus, all that is required to replicate HG is to multiply MT fuel consumption by 0.15. I'm still debating whether this should apply to all fusion PPs, including vehicles, but I might do so given the alternative of fuel cells produces interesting tradeoffs (this is otherwise beyond the scope of this exercise).
3) Armor Volume: There is a strong view that armor ought to take up hull space. I'm adding this back though honestly it does not matter much for adventure class ships. It is likely much more meaningful for capital ships, which may feature in later examples.
In HG, armor A is a factor starting at 0. Armor takes up V(1+A)% of hull volume, where V=4 for TL 7-9, 3 for TL 10-11, 2 for TL 12-13, and 1 for TL 14-15. For MT, the minimum Armor Factor is 40 for spacecraft, corresponding to a mass multiplier of 33.6 for hard steel in Striker (and MT). Let A be our Armor Factor >40 and M the corresponding mass multiplier. Then armor takes up the following percentage of the hull: [8 x Armor Type Mass Multiplier x M/33.6]%. The corresponding V values for MT are 3.5 for TL 7, 2.8 for TL 9, 2.5 for TL 10, 2.1 for TL 12, and 1.1 for TL 14, so rather close overall and more generous at lower TLs. The advantage of this MT method is we can compute armor density and perhaps use that.
4) Bridge: HG imposed a 2% of hull volume bridge requirement, 20 D-tons minimum. I am using a more flexible rule via Duty Stations. A Duty Station is 2 D-tons (like a small stateroom), and all starships require a minimum of (10/active crew) Duty Stations. The active crew requirement is based upon the MT rules for crew count and could produce deviations from the 2% of hull requirement, which I think is fine given the better model of Duty Stations. But for ships <=1000 D-ton, the bridge is always 20 D-tons (10 Duty Stations).
5) Computers: HG computers were gigantic, likely including other systems like control panels, comms, and sensors. In MT, the latter systems are explicit and computers are much smaller. We use the MT rules without modification, which likely results in lower overall volume than HG.
Example starships are forthcoming!
