Trying to replicate/understand a ship design (MgT2 High Guard)

[Prodromoi]

This morning I saw a link on Facebook to a ship design with some very lovely deckplans. Unfortunately I can't find the original post now, so I can only include the link to the design itself which was included in that post.

https://blog.jonbrazer.com/2019/01/28/traveller-reidian-flyer-poster/

I was curious about the design as it's way faster than any ship I've seen in Traveller before (being familiar with CT, but not with the new versions that have included alternatives to the standard M-drives), so I had a look at the rules in High Guard and tried to replicate it. And this is where I've stumbled. I cannot figure out how the fuel tankage for the 7-G High Burn Thruster takes up so little tonnage (63 dtons in the ship stats).

The way I worked it out was, according to page 16 of High Guard, which states (referring to the ships total tonnage), the fuel requirements are "2.5% per Thrust per hour".

So, for a 300 dton ship, fitted with a 7-G High Burn Thruster intended for 3 hours of operation:

(300 * 2.5%) * 7 * 3 = 157.5 dtons

I also tried replicating the design in MgT2 ship design spreadsheet that I found online; this agreed with the listed stats on most points, but did not match the thruster fuel capacity (coming up with 157.5, matching my manual calculation). (This spreadsheet was unhappy with including 3 turrets, strangely, considering it to be exceeding the maximum by one. It's still one hardpoint per 100 dtons, if I read the new books correctly.)

Have I missed something about fuel compression or tech level? Is there some factor in this ship design that I haven't accounted for that would reduce the thruster tonnage to 63 dtons, instead of the 157.5 that I worked it out to require?

 

[Anonymous]

Your calculations are correct when checked against standard rules.

Perhaps they forgot the 2.5x, or they use variant rules?

Mechanically under standard rules it might be better to install a faster maneuver drive and a smaller rocket.

Their artist has seen Babylon-5.

For 100 dtons and over, 1 hardpoint per 100 dtons is correct.

 

[Prodromoi]

Your calculations are correct when checked against standard rules.

Perhaps they forgot the 2.5x, or they use variant rules?



Their artist has seen Babylon-5.

Thanks. Glad I'm not going mad there...

I do rather like the design and am going to build something around it, but not quite so swift!

 

[AnotherDilbert]

See HG, p48 "Primitive and Advanced Spacecraft".

For reaction drives we can use the advantage Fuel Efficient which reduces fuel consumption by 20% per TL above the minimum.

A Reaction drive-7 is available by default at TL-9, so by TL-12 we can build it with 3 applications of the advantage Fuel Efficient at 20% each, for a total of 60% reduction.

So, in this case we reduce fuel consumption down to 40%.

157.5 Dt × 40% = 63 Dt.

 

[Prodromoi]

See HG, p48 "Primitive and Advanced Spacecraft".

For reaction drives we can use the advantage Fuel Efficient which reduces fuel consumption by 20% per TL above the minimum.

A Reaction drive-7 is available by default at TL-9, so by TL-12 we can build it with 3 applications of the advantage Fuel Efficient at 20% each, for a total of 60% reduction.

So, in this case we reduce fuel consumption down to 40%.

157.5 Dt × 40% = 63 Dt.

Ah, that's it, I see... Presumably that should have appeared in the ship stats against the Reaction drive (in the same way the Fusion power plant notes Reduced Size x3).

 

[AnotherDilbert]

Presumably that should have appeared in the ship stats against the Reaction drive (in the same way the Fusion power plant notes Reduced Size x3).

Agreed, it should. You can look at the price of the reaction drive, it should have been increased by 50% to pay for the advantages.

 

[Prodromoi]

Presumably that should have appeared in the ship stats against the Reaction drive (in the same way the Fusion power plant notes Reduced Size x3).

Agreed, it should. You can look at the price of the reaction drive, it should have been increased by 50% to pay for the advantages.

Ah, I've just seen that it does note that already, I missed it/didn't recognise it when first looked at it. While I get the non-standard drives in concept, it's something I need to get my head around!

Do many designs utilise reaction drives and things like that, or do most 'current' MgT2 designs stick the standard drives? (And is a ship with a 4G and 7G drive just bonkers, or has "tech creep" resulted in things like that being more normal?)

 

[Anonymous]

Presumably that should have appeared in the ship stats against the Reaction drive (in the same way the Fusion power plant notes Reduced Size x3).

Agreed, it should. You can look at the price of the reaction drive, it should have been increased by 50% to pay for the advantages.

Ah, I've just seen that it does note that already, I missed it/didn't recognise it when first looked at it. While I get the non-standard drives in concept, it's something I need to get my head around!

I didn't see that note for the reaction drive. Did they update the plan?

 

[AnotherDilbert]

Do many designs utilise reaction drives and things like that, or do most 'current' MgT2 designs stick the standard drives?

I would say most stick with fairly standard drives. Reaction drives still take a lot of space. M-drives are a lot more space efficient.

(And is a ship with a 4G and 7G drive just bonkers, or has "tech creep" resulted in things like that being more normal?)

We have a lot more options to play with now than in CT, so we can build more extreme designs.

But 11 G is just a start, how about 25 G?
http://forum.mongoosepublishing.com/viewtopic.php?f=89&t=119159

 

[dmccoy1693]

See HG, p48 "Primitive and Advanced Spacecraft".

For reaction drives we can use the advantage Fuel Efficient which reduces fuel consumption by 20% per TL above the minimum.

A Reaction drive-7 is available by default at TL-9, so by TL-12 we can build it with 3 applications of the advantage Fuel Efficient at 20% each, for a total of 60% reduction.

So, in this case we reduce fuel consumption down to 40%.

157.5 Dt × 40% = 63 Dt.

This is correct. Yes, the higher TL/reduced fuel note should be there, but we deleted it off the poster for space reasons. It is in the PDF of the ship.

Thank you for discussing our ship.

 

[dmccoy1693]

Do many designs utilise reaction drives and things like that, or do most 'current' MgT2 designs stick the standard drives? (And is a ship with a 4G and 7G drive just bonkers, or has "tech creep" resulted in things like that being more normal?)

This ship is far from normal. The PDF of the ship goes into detail if it's origins. It is a blockade runner, needing to zoom past anything that chases after it, including missiles. The 4G is what it normally runs on. The additional 7G is only for when it absolutely needs it.