[Ship Design] Mercenary Transport & Dropship x2

[AnotherDilbert]

I guess we can agree to disagree here.

Sure, but I'm not sure what we actually disagree about.

Cattle-class is cramped?
APCs are very cramped, but still manage to fit combat troops?
Acc. benches provide much more space than either?

I've ridden in a lot of aircraft, especially the 737. It's cramped, but seats six crossways. I've never sat in an acceleration bench so I cannot say how that one works. But the standard eco omy seat with legroom is about, realistically, three feet in depth. 1.5m rounded up is five feet. As I said it's cutting things damn close, if not going over. And a soldier equipped with his gear cannot easily get out of that seat with so little room. Hence I am citing what I've seen and touches as reality, not what's written in the book.

Cubic space means nothing for seating, it's width and depth.

OK, take a United 737-700: (https://www.seatguru.com/airlines/United_Airlines/United_Airlines_Boeing_737-700_A.php)

Economy seat pitch is 31" ≈ 79 cm, width is 17.2" ≈ 44 cm. Cabin width (6 seats + aisle) is 3.5 m.
One such row covers an area of 3.5 m × 0.79 m ≈ 2.76 m² including aisle or 0.46 m² per seat.


One Dt of acc.benches covers an area of 4.7 m² for 4 seats or 1.17 m² per seat.
Scaled to the same 3.5 m cabin width that is a seat pitch of 1.34 m (~53").

Acc. benches are much more spacious than cattle-class. Agreed?


In the same aircraft, first class is four seats per row with a pitch of 38" ≈ 96.5 cm.
One such row covers an area of 3.5 m × 0.965 m ≈ 3,38 m² including aisle or 0.84 m² per seat.

Acc. benches are more spacious than first class (on this particular aircraft configuration). Agreed?


The passenger bay on a M113 is very roughly 2 m × 3.5 m (estimated) ≈ 7 m², nominally for 12 people (commander + 11 passengers) or 0.54 m² per seat.

Acc. benches are much more spacious than this particular APC. Agreed?


Given that acc. benches provide 250% as much area as cattle class and much more area than any APC or IFV it might be possible to seat combat troops, even armoured, so that they can exit reasonably quickly. Agreed?

 

[Anonymous]

It's a bit hard to define, as Traveller doesn't make you pay for corridors and door access. I don't have a problem with the classic Traveller allowance for an acceleration couch (1.5m x 1.5m per seat) but I did have a problem with how they were drawn in deck plans, literally 1 per square.

While we're on the subject, it's incredible how much space inside a combat vehicle is taken up by crew and how this is ignored by most game design systems.

The photo is a Leopard-1.

 

[phavoc]

Here's where we started to drift:

quote=AnotherDilbert post_id=933253 time=1545210398 user_id=364622]
Airline seat pitch is about 80 cm, width about 45 cm. (https://en.wikipedia.org/wiki/Airline_seat#Seat_pitch) With a deck height of 2 m that is 0.8 × 0.45 × 2 = 0.72 m³ or 0.05 Dt or ~20 seats per Dt. To get down to 10 people per Dt we have to add in aisles, kitchens, and toilets. [/quote]

The size of the seat itself is not the only thing you have to factor into things. You also must have access space. The inside usable space of a 737 (all variants) is approximately 1 DT in width. So that's two squares on a deck plan. And economy seating is 3x3. If you take into account the seat space, the very narrow space to get into the seat AND the amount of space have underneath the seat in front of you, that equates to about 3ft deep. 1.5m is roughly 5ft deep. So that leaves us only 2ft left to add the 2nd row. And that's not enough space. I realize I'm being a bit unfair here because as you add more seats you start getting more wastage space that you can increase seat numbers. But strictly speaking 1Dt gets you seating for 6, but that also gives you something more like 1st class legroom - which I think we can both agree troops don't get.

So breaking this down by individual Dton is a limitation. If you increase your spacing to just 3 Dtons you would increase seating from 18 to 30 because you can reclaim that space and get back to cattle class. And therein lies the rub - when we break designs down to specific tonnage then we lose certain flexibilities. Here is that I am talking about graphically, with each X being one seat, and occupying 1 square on a map (.5Dton):

1Dton - XXX XXX

2Dton - XXX XXX
XXX XXX
XXX XXX (bonus)

3 Dton - XXX XXX
XXX XXX
XXX XXX
XXX XXX (bonus)
XXX XXX (bonus)

Having seating for troopers at 4 per Dton is reasonable. I think we also need to differentiate between assault craft that operate in space and drop from orbit and grav vehicles such as APC's. These are two different crafts that operate in somewhat similar fashions, but that they are also two very different classes of vehicles.

One of the issues with talking about cubic space is that it's not all usable, or applicable. I always try to break designs down into how they would fit on a deckplan. It's very confusing when you try to draw what the stats say and they don't match (yes, I'm aware of the 20% wiggle room for designs). I still try to make things match the stats as much as I can.

 

[AnotherDilbert]

Here's where we started to drift:
...
The inside usable space of a 737 (all variants) is approximately 1 DT in width. So that's two squares on a deck plan.
...
So breaking this down by individual Dton is a limitation.

OK, now I see. We tried to calculate the same thing different ways, I used per seat and you used per Dt square.

To avoid the quantisation effect you have noted, we can take as large an area as possible: The entire Economy area. It has six seats per row in 11 rows for a length of about 9 m, let's call it 6 squares long by 2 squares wide for a total of 6 × 2 = 12 squares or 6 Dt. Agreed so far?

66 seats in 6 Dt is 11 people per Dt which is 0.41 m² per person (roughly the same as the 0.46 m² per seat I calculated). I think we agree.


In that same area we could fit 6 Dt × 4 = 24 Acc. bench seats. That gives each acc. bench passenger 66 / 24 = 2.75 times as much space as an Economy passenger.


(Note that two squares on the aircraft is not really one Dt, since the cabin is not 3 m tall, but only about 0.7 Dt.)

 

[AnotherDilbert]

That's mainly a function of the vehicle rules requiring too much space per person, as well as the ridiculous armor rule for small spacecraft vs the more realistic rules for vehicles.

It's the same system? A fixed percentage of the craft per point of armour?

 

[Old School]

I’ll let you do the math since that’s your thing:

What percentage of total space would a small, TL14 spacecraft need to get 10 points of protection using bonded superdense armor? Now, design a grav tank of the same size and TL. How much of its total space does it need to get the same armor protection? Please keep in mind the different scale used for spacecraft vs ground weapons.

 

[AnotherDilbert]

What percentage of total space would a small, TL14 spacecraft need to get 10 points of protection using bonded superdense armor? Now, design a grav tank of the same size and TL. How much of its total space does it need to get the same armor protection?

OK, the spacecraft would use 10 × 0.8% = 8% of the craft.
The vehicle would use ( 100 - 4 ) × 0.4% = 38.4% of a part of the craft. Note that only the payload is considered, not the drives etc.

Both system would use the same percentage, whether the craft is tiny or a megaton behemoth. Both are equally unrealistic, even if they are optimised for different size craft.