95ton Gravas Class Support Tender

[Patron Zero]

Developing an article to appear in Freelance Traveller, presenting the Gravas Class Support Tractor, a 95ton 'tug' intended to support the IISS Express Boat Network.

The Gravas Class tug was developed for duties of ferrying x-boats to-from their jump-points as well as refueling said vessels in frontier zones where 'improved' XBS facilities are not available.

When hard-docked to an x-boat, a support tractor can skim fuel from gas giants, using integral fuel scoops and onboard fuel processors, directly replenishing an XB's empty reserves.

Not routinely done, a support tug can 'hitch' a ride with an x-boat if said ship is being returned to a naval facility for refit or retirement. Essentially now a near-200ton starship, the docked tug-XB enjoy a J-2 range of travel, further if refueling maneuvers are done.

 

[savage]

cool. I look forward to it.

 

[RandyB]

Fun concept!

 

[wbyrd]

Tender pilot: "Oh crap pirates!!!"
X-boat pilot: "hold on ta ya hats boys! It's gonna get bumpy...."

 

[Selandia]

exactly my understanding of an excellent symbiosis between a Jumper and a M tug

eager to see it

have fun

Selandia

 

[Patron Zero]

Just a brief update to share a WIP image depicting the deckplan overlay of the 95ton Support Tractor once docked to an X-boat.

Not shown are the docking clamps or anchor points for such on the X-boat.

Again, a WIP so subject to adjustments both cosmetic and technical.

 

[Patron Zero]

Just sorting a few things out and something doesn't look right here.

Below is a roughed-out size comparison between a 100ton X-boat hull and two (2) small craft, a 50ton cutter and a 30ton Ship's Boat.

This was put together from the deckplans in GDW's Traders & Gunboats so know such is considered canon as such goes.

My problem is that the pair of small craft look pretty large compared to the x-boat but according to the grid in said drawings, all on the same scale.

Am I missing something here ?

http://www.travellerrpg.com/CotI/Gallery/index.php?n=2026

 

[whulorigan]

Just sorting a few things out and something doesn't look right here.

Below is a roughed-out size comparison between a 100ton X-boat hull and two (2) small craft, a 50ton cutter and a 30ton Ship's Boat.

This was put together from the deckplans in GDW's Traders & Gunboats so know such is considered canon as such goes.

My problem is that the pair of small craft look pretty large compared to the x-boat but according to the grid in said drawings, all on the same scale.

Am I missing something here ?

The dimensions as shown in that particular drawing may or may not be off, but one thing to remember is that since displacement-tonnage is a measure of volume and not of linear dimensions, an increase in volume can look deceptively smaller or larger depending on the actual configuration.

Since volume increases as a cube as compared to linear dimensions, doubling the volume/displacement of a craft only increases its linear dimensions by the cube-root of the volume increase (all other things being equal).

So, for example, if you have two vessels, one that is 100dton, and the other 800dton, if they are the exact same configuration, the 800dton vessel will only be twice as long/wide/deep as the 100dton vessel. When comparing vessels of different configurations, things can appear even more odd (especially if one of the vessels has a configuration with extreme parameters, such as a long cone/needle).

For the deckplans you referenced above, remember that those vessels are not relatively "flat" in the plane of the page, but have an axial symmetry about their long axis, meaning that each of those vessels is just as deep into/out-of the page as the width shown in the plans.


As a real-life example, think of times when you have gone into a store to buy a 1.0 liter bottle of soda, and two 1.0 liter bottles that are right next to each other for different soda brands each have a container with a different shape, and you are certain that the one bottle must be less than or greater than 1.0 liter. The eye assesses size via linear dimensions; it is not as good at assessing size via volumetric dimensions.

 

[atpollard]

Just sorting a few things out and something doesn't look right here.

Below is a roughed-out size comparison between a 100ton X-boat hull and two (2) small craft, a 50ton cutter and a 30ton Ship's Boat.

This was put together from the deckplans in GDW's Traders & Gunboats so know such is considered canon as such goes.

My problem is that the pair of small craft look pretty large compared to the x-boat but according to the grid in said drawings, all on the same scale.

Am I missing something here ?

I did some quick and dirty volume calculations (just using bounding boxes) and the plans appear to match the correct volumes. The visual problem is that you can't see how much further the X-boat sticks out of the page than the 50 dTon or 30 dTon small craft. Print out the plan and start to model it, in 3D by cutting it out and placing two plans at right angles to each other.

 

[aramis]

Just sorting a few things out and something doesn't look right here.

Below is a roughed-out size comparison between a 100ton X-boat hull and two (2) small craft, a 50ton cutter and a 30ton Ship's Boat.

This was put together from the deckplans in GDW's Traders & Gunboats so know such is considered canon as such goes.

My problem is that the pair of small craft look pretty large compared to the x-boat but according to the grid in said drawings, all on the same scale.

Am I missing something here ?

http://www.travellerrpg.com/CotI/Gallery/index.php?n=2026

the XBoat as shown is a cone and a hemisphere.
v_cone=πr²h/3
v_sphere=πr³4/3
r=6
h=15.5

Subbing in:
v_cone=π6²*15.5/3
v_sphere=π6³4/3

v_cone=π36*16.5/3
v_sphere=π216*4/3


v_cone=π198
v_sphere=π288


v_cone=622
v_sphere=905

So V_xboat=622+(904/2)=1074 cubic meters - undersized for the design.

But note also - the actual cone is truncated, and so I need to actually rework it as two cones - the first including the missing, and the second the subtraction for the missing.

V_{long cone}=π6*6*19.5/3
V_{long cone}=735

V_{short cone}=π*1*1*3/3
V_{short cone}=3
so truncated cone vol 732
Ship vol = 732+452=1184
Or a mere 85 Td. More than 10% off.


The cutter, by comparison, is a cylinder and rotated ellipse
V_Cylinder=πr²l
r=3
l=17
the cylinder is thus 480
THe elipse is 3x3x4.5
and
V_{eliptical ovoid}=4πr₁r₂r₃/3
thus 170
Half that for hemiovoid -85
add to the ellipse 566. (Note that I worked it on the calc without rounding hence the difference)

Now, 566 m³ is 40.4 Td.

Big caveat here: the X-boat can be made compliant by increasing the radius by 0.5m
V=535+860=1395 which is 99.6 Td.

 

[kilemall]

As a real-life example, think of times when you have gone into a store to buy a 1.0 liter bottle of soda, and two 1.0 liter bottles that are right next to each other for different soda brands each have a container with a different shape, and you are certain that the one bottle must be less than or greater than 1.0 liter. The eye assesses size via linear dimensions; it is not as good at assessing size via volumetric dimensions.

Actually, I find I can quickly assess the square footage of a building at a glance, largely because of the mental apparatus constructed in my head at a young age for building Traveller starship deck plans.

 

[Patron Zero]

My thanks for everyone chiming in on what is now best understood as an optical 'illusion'.

-Aramis, as always your command of computations is impressive.

 

[aramis]

-Aramis, as always your command of computations is impressive.

Thanks... realize, I do this with just high school pre-algebra, college statistics, and Math Methods. (I filled my undergrad math skills with BASIC programming; we used Vax Basic, and tested out of my math requirements for my MAT.)

I'm also dyslexic.

So I show much of the work so that (1) others can see how it's done and (2) people can double check my math for transcription and calculation errors.

I often take the long way, because I don't have the extra toolkit of shortcuts from Algebra II and Trig. (Every time I wind up subbing in Trig classes, I learn a new shortcut.)

Anyway, the disparity of volume is an issue of a 2-dimensional map of a 3 dimensional item. Sometimes you don't REALIZE it until you crunch the numbers.

 

[Patron Zero]

Woo-Hoo, first look at the 3D model of the Gravas Class Support Tractor.

Mind some minor tweaks to the ship for surface textures, paint and registry markings but it's the concept I've had in mind from first putting pencil to paper.

Render by my friend Christian from DeviantArt for such visual wonderment.

http://www.travellerrpg.com/CotI/Gallery/index.php?n=2028

 

[Shadowrunner]

That is lovely, I'm putting my vacc suit on and grabbing my welding gear right now. It's such a logical aspect of the Traveller universe, well done on a great job!

 

[Patron Zero]

That is lovely, I'm putting my vacc suit on and grabbing my welding gear right now. It's such a logical aspect of the Traveller universe, well done on a great job!

Many thanks for the kind words, I've had some great input from many persons here at the board, as always very appreciative of such support on my often 'renegade' ideas.