400 dt fuel shuttle design test

[Annatar Giftbringer]

Greetings,
I decided to try to design a fuel shuttle for fun, and to test my understand of the ship design rules.

From the Azhanti page in high guard we know its size, 400 dton, and I seem to recall reading somewhere that he original version could carry 350 dtons of fuel.

A 400 dton ship requires a 20 dton bridge, which combined with 350 dton cargo leaves us with 30 dtons for everything else.

Assuming my calculations are correct, the space needed for m-drive, power plant and fuel should be 13, 20 or 26 dtons depending on its thrust performance.

This would leave us with 4, 10 or 17 dtons for other systems, such as cargo, passenger space or crew accommodation - or weapons! This is a military support vessel, after all.

In order to increase the usefulness of the design, I'm thinking the fuel could be stored in bladders. This way almost all of the 350 dton fuel space could be used to haul cargo and supplies when needed.

The question is where to draw the line between extra capacity and m-drive performance. The main use for fuel shuttles in published material is to refill the fuel tanks of a large ship, something that requires lots of trips, meaning higher thrust will save lots of time in the long run, so I'd say thrust 3 is warranted.

Fuel scoops are needed, but if we streamline the hull they're automatically included, and in other hulls they cost money, not space.



Thoughts or comments so far?

 

[Condottiere]

Seven fifty tonne holding tanks.

Or maybe twelve thirty tonne fuel modules, which would allow them to be switched with more specialized yet generic modules.

 

[phavoc]

For the AZL, the shuttles were the primary method for frontier refueling, so I think that would mean they don't need to be modularized to fulfill other purposes. I would look at variants depending upon speed, maximum fuel vs performance, and possibly one that is middle of the road, that carries say 200 tons fuel and sets aside the rest for cargo (much like the KC-10 does for the USAF).

 

[AnotherDilbert]

The first thing about refuelling is that you MUST ALWAYS be able to refuel EVERYWHERE there is a scrap of hydrogen.

So the shuttle should be fully streamlined, perhaps even with heat and rad shielding.

I would assume we position the ship as close as convenient to the fuel source and then let the shuttle shuttle back and forth. I guess the distance travelled by the shuttle is rather short, so performance is not that critical, so perhaps 2 G drives would be enough.

Bladders would be a great fit. A few tons of UNREP equipment would allow the shuttle to transfer the fuel to the ship quickly.

We need fuel purifiers somewhere, but they are better placed in the ship?

A few turrets never hurts, but the combat value of something slow and unarmoured is limited... (No comment on the AHL itself, of course).



The AHL has 33000 dT tanks and 4 fuel shuttles carrying 350 dT fuel each? Each shuttle would have to make 33000 / 350 / 4 ≈ 24 trips to fully refuel the ship. Each sweep through a gas giant atmosphere takes a few hours, let's say 3 h. So, best case, to refuel the shuttles would have to work non-stop for 3 - 4 days to fully refuel the ship. Relying on fuel shuttles limits your strategic speed significantly.

By streamlining the ship we would save at least 3 days per jump and 1760 dT (= 3% of the ship). Relying on fuel shuttles is a bad idea...

 

[wbnc]

Greetings,
I decided to try to design a fuel shuttle for fun, and to test my understand of the ship design rules.

From the Azhanti page in high guard we know its size, 400 dton, and I seem to recall reading somewhere that he original version could carry 350 dtons of fuel.

A 400 dton ship requires a 20 dton bridge, which combined with 350 dton cargo leaves us with 30 dtons for everything else.

Assuming my calculations are correct, the space needed for m-drive, power plant and fuel should be 13, 20 or 26 dtons depending on its thrust performance.

This would leave us with 4, 10 or 17 dtons for other systems, such as cargo, passenger space or crew accommodation - or weapons! This is a military support vessel, after all.

In order to increase the usefulness of the design, I'm thinking the fuel could be stored in bladders. This way almost all of the 350 dton fuel space could be used to haul cargo and supplies when needed.

The question is where to draw the line between extra capacity and m-drive performance. The main use for fuel shuttles in published material is to refill the fuel tanks of a large ship, something that requires lots of trips, meaning higher thrust will save lots of time in the long run, so I'd say thrust 3 is warranted.

Fuel scoops are needed, but if we streamline the hull they're automatically included, and in other hulls they cost money, not space.



Thoughts or comments so far?

I have a 500 ton version of an in system tanker ...if you tweak that down to 400 Dton it comes up to having around 300 tons for fuel. Using a streamlined hull and adding a fuel processor isn't that big of an impact on the capacity so yeah it would be fairly practical. I need to convert this over to 2E, for now it's in the book I released a while back.

The fuel bladder idea might be doable. seems like f its a dedicaed fuel skimmer the multi role aspect might not be needed...but ya never know.

 

[AnotherDilbert]

Using a streamlined hull and adding a fuel processor isn't that big of an impact on the capacity so yeah it would be fairly practical.

Adding a fuel processor that can refine the entire fuel tank in a few hours take something like half the volume of the tank, so instead of 300 dT fuel we could carry 200 dT fuel and 100 dT processor. Not very practical.

The fuel bladder idea might be doable. seems like f its a dedicaed fuel skimmer the multi role aspect might not be needed...but ya never know.

If the ship is unstreamlined (like the AHL), it needs smaller craft for cargo and personnel transfers. A craft with a cargo hold, foldable acceleration benches, and fuel bladders can replace three different specialised craft, saving a lot of space on the ship. Very practical.

 

[wbnc]

Using a streamlined hull and adding a fuel processor isn't that big of an impact on the capacity so yeah it would be fairly practical.

Adding a fuel processor that can refine the entire fuel tank in a few hours take something like half the volume of the tank, so instead of 300 dT fuel we could carry 200 dT fuel and 100 dT processor. Not very practical.

If I read it right, the AHL has its own integrated processors so evidently the shuttles just skim te fuel and bring it back to the ship for processing.which seems to be the most efficient way to go about it. The ship can afford the lost tonnage far better than the smaller shuttles

The fuel bladder idea might be doable. seems like f its a dedicaed fuel skimmer the multi role aspect might not be needed...but ya never know.

If the ship is unstreamlined (like the AHL), it needs smaller craft for cargo and personnel transfers. A craft with a cargo hold, foldable acceleration benches, and fuel bladders can replace three different specialised craft, saving a lot of space on the ship. Very practical.

good point, so perhaps the idea of using bladders in the cargo space would be a good idea. a multi role shuttle might be a good buy.

 

[Annatar Giftbringer]

hanks for the replies everyone!

As some have noted, using four (relatively) small shuttles to refuel a ship as large as the AHL looks like a slow solution, especially since the ship has fuel scoops.

My theory is that the Azhanti often operates alone, in (potentially) hostile systems. Diving into a gas giant without anyone assuming the high guard position can be risky, and thus the ship carries fuel shuttles.

When time is of the essence, or the local area is deemed safe, the ship can use its own fuel scoops to fill the tanks.

My reasoning for suggesting fuel bladders was that, as has been noted in the thread, it offers versatility. At the small cost of a few extra credits and no drawbacks it lets the fuel shuttle do so much more than simply haul fuel. It could carry supplies to and from the ship, and with a few extra tweaks it can transport people as well.

Versatility is rarely a bad thing, especially when it comes to a multi-purpose ship like the Azhanti.

Giving the fuel shuttle a wider scope of roles to fill also means that the same design can be so much more useful for other users than AHL ships. Stationed at a space port it could transport fuel from a nearby gas giant to the port for refining and sale, and with the ability to carry cargo it could help load/unload freighters in orbit.

I do agree that streamlining is very helpful for a craft like this. Weapons might not be necessary, but a couple laser turrets are never a bad idea.

Compartmentalizing the cargo hold is a good idea, though my idea was to simply have multiple small bladders rather than one large. Having the cargo hold consist of several 30 dton (cutter) modules would be interesting, and really allow for customization!

I do have an idea regarding acceleration benches, that I was gonna save for a thread of its own, but I might as well put it here. The description for this item states that thy are designed to fold away when not in use, which I interpret as the area can be used for other things, such as cargo. A 10 dton cargo hold could, in my mind, be 6 dton cargo and 4 dton acceleration benches, meaning that the area could transport 20 people plus 6 dtons of cargo, or 10 dtons of cargo.

Assuming that my interpretation isn't totally off, this'd mean that in the case of the fuel shuttle we could install say... 50 dtons of benches and have 300 dtons of pure cargo, and 3,5 dtons of collapsed fuel bladders. This way the shuttle could carry up to 200 passengers plus 300 dtons of fuel or 296,5 dtons of cargo OR 350 dtons of fuels - useful!

50 dtons of benches in each of the four shuttles means they could carry more or less the entire crew complement if needed, for short periods of time.

Finally, allowing the fuel shuttle to carry cargo means that an Azhanti leaving port could carry an extra ~1,400 dtons of supplies, for itself or to restock a colony or remote base.

 

[wbnc]

hanks for the replies everyone!

As some have noted, using four (relatively) small shuttles to refuel a ship as large as the AHL looks like a slow solution, especially since the ship has fuel scoops.

My theory is that the Azhanti often operates alone, in (potentially) hostile systems. Diving into a gas giant without anyone assuming the high guard position can be risky, and thus the ship carries fuel shuttles.

When time is of the essence, or the local area is deemed safe, the ship can use its own fuel scoops to fill the tanks.

My reasoning for suggesting fuel bladders was that, as has been noted in the thread, it offers versatility. At the small cost of a few extra credits and no drawbacks it lets the fuel shuttle do so much more than simply haul fuel. It could carry supplies to and from the ship, and with a few extra tweaks it can transport people as well.

Versatility is rarely a bad thing, especially when it comes to a multi-purpose ship like the Azhanti.

Giving the fuel shuttle a wider scope of roles to fill also means that the same design can be so much more useful for other users than AHL ships. Stationed at a space port it could transport fuel from a nearby gas giant to the port for refining and sale, and with the ability to carry cargo it could help load/unload freighters in orbit.

I do agree that streamlining is very helpful for a craft like this. Weapons might not be necessary, but a couple laser turrets are never a bad idea.

Compartmentalizing the cargo hold is a good idea, though my idea was to simply have multiple small bladders rather than one large. Having the cargo hold consist of several 30 dton (cutter) modules would be interesting, and really allow for customization!

I do have an idea regarding acceleration benches, that I was gonna save for a thread of its own, but I might as well put it here. The description for this item states that thy are designed to fold away when not in use, which I interpret as the area can be used for other things, such as cargo. A 10 dton cargo hold could, in my mind, be 6 dton cargo and 4 dton acceleration benches, meaning that the area could transport 20 people plus 6 dtons of cargo, or 10 dtons of cargo.

Assuming that my interpretation isn't totally off, this'd mean that in the case of the fuel shuttle we could install say... 50 dtons of benches and have 300 dtons of pure cargo, and 3,5 dtons of collapsed fuel bladders. This way the shuttle could carry up to 200 passengers plus 300 dtons of fuel or 296,5 dtons of cargo OR 350 dtons of fuels - useful!

50 dtons of benches in each of the four shuttles means they could carry more or less the entire crew complement if needed, for short periods of time.

Finally, allowing the fuel shuttle to carry cargo means that an Azhanti leaving port could carry an extra ~1,400 dtons of supplies, for itself or to restock a colony or remote base.

I don't see anythign in your thinking that jumps out as being off base. I think you have a good grasp on wha you are wanting to build. Id consder the shuttle a good investment for any ship that needs a heavy fueler, or trasnport shuttle.

 

[AndrewW]

My theory is that the Azhanti often operates alone, in (potentially) hostile systems. Diving into a gas giant without anyone assuming the high guard position can be risky, and thus the ship carries fuel shuttles.

In emergencies, the ship can utilize its limited streamlining to allow a direct fuel skim of a gas giant. This procedure will not work with an ocean or ice cap, but it does give the ship the ability to refule in most star systems. The ship deives into the gas giant's atmosphere and opens its fuel scoops, loading up with hydrogen directly from the atmosphere. There are three dangers to this procedure; all are called for by the very design of the ship, by the costs of the design, and the realities of structural integrity."
1. Loss of the Fuel Shuttles.
2. Loss of Fuel Deck Integrity.
3. Internal Damage to Drives.

I do have an idea regarding acceleration benches, that I was gonna save for a thread of its own, but I might as well put it here. The description for this item states that thy are designed to fold away when not in use, which I interpret as the area can be used for other things, such as cargo. A 10 dton cargo hold could, in my mind, be 6 dton cargo and 4 dton acceleration benches, meaning that the area could transport 20 people plus 6 dtons of cargo, or 10 dtons of cargo.

Even folded though they are still going to consume some space.

Normally, one or more shuttles are diverted to administrative uses, complete with passenger seats installed...

 

[Annatar Giftbringer]

Even folded though they are still going to consume some space.

Ah, you have a Point there, of course... The next question would be how much space do they require when folded? 10%? 5% And also, is the area practically useable as cargo space when the benches are folded away? Or perhaps it's better to just not meddle with details like that, and settle for a small area dedicated to passengers, or as Supplement 5: Lightning Class Cruisers seems to suggest, install passenger facilities in one of the shuttles, reducing the fuel capacity of that specific shuttle with 50-100 dtons in order to carry up to 400 passengers.

As an aside, judging from the quotes from Supplement 5: Lightning Class Cruisers it seems I wasn't too far off with my guesses, and it sounds like I might need to get that book

 

[steve98052]

Here's another possible way to structure the fuel shuttles:

Design them so that the mother ship sees them as de-mountable fuel tanks, except that they're streamlined and equipped with a bridge and engineering section. Fly them into dedicated space docks, clamp on the fuel couplings, and you're good to go.

I'll look at the book and be back with a sample design a bit later.

 

[steve98052]

I'll look at the book and be back with a sample design a bit later.

Here's a sample design for a 1000 dton tanker designed for maximum fuel capacity and 3 G acceleration (chosen because skimming a gas giant for fuel requires being able to escape the gravity of a gas giant, and also for speed).

I used the ship design rules from the 2008 Mongoose Traveller core rule book, and even worked out the price. I find that I have a PDF of a February 2016 play-test draft of High Guard, but I didn't notice that I had that until after I had completed this; I'm not sure how close that is to the published edition or the 2008 books.

Tanker-1000
Hull 1000, code A, streamlined MCr110 (scoops included)
M-Drive L (3 G), 21 dtons, MCr44
Power Plant L, 34 dtons, MCr88
Bridge 20 dtons, MCr5
Computer Model 1, MCr0.030
Power Plant Fuel, 1 week, 11 dtons, MCr0
Scoop Fuel, 1000-21-34-20-11 = 914 dtons, MCr0
Total MCr203.030 = 110+88+5+0.030

Here's the start of a design for a 7500 dton fighting ship. (I chose that size because larger ships require a larger bridges, counter-intuitive as that seems to me.) It is built to Jump-4 and 4 G, with allowance for extra fuel in case the power plant is expanded to power weaponry (and because it makes the math easier with the above tankers' 914 dton fuel load). A figure that I found somewhat surprising was how large the fuel processors have to be to refine one Jump-4 worth of fuel during the time it takes to travel from a small gas giant to the 100 diameter limit.

I used the ship design rules from the first Mongoose edition of High Guard (except for the fuel processors, which I got from the 2008 core book, because I put the book away without remembering to look up the numbers for that).

Mother Ship
Hull 7500 dtons
M-Drive 4 G, 131.25 dtons
J-Drive 4, 375 dtons
Power Plant 4, 225 dtons
Jump 4 Fuel, 3000 dtons (included in tankers)
Power Plant Fuel, 8.7 weeks (?), 656 dtons (included in tankers)
Bridge, 75 dtons (!)
Computer
Software
Tanker-1000 in space docks (3), 3000 dtons
Tanker-1000 in hangar (1), 1300 dtons
Fuel Processors 600 dtons, refines 12000 dtons of fuel per day, which is equal to 3000 dtons per six hours, the approximate travel time from a small gas giant to the 100 diameter jump limit

Total of 7500-131.25-375-75-3000-1300-600 = 2018.75 dtons for everything else:
Staterooms
Low Passage Tubes (Frozen Watch and emergency)
Cargo Hold
Other vehicles (such as fighters)
Turrets
- Laser
- Missile Rack
- Sandcaster
- Particle Beam
Bays
- Missile Bank
- Particle Beam
- Fusion Gun
- Meson Gun
Spinal Mount
Nuclear Damper
Meson Screen

 

[steve98052]

Tanker-1000 in space docks (3), 3000 dtons
Tanker-1000 in hangar (1), 1300 dtons

This is another thing that deserves a little explanation. The mother ship is designed with close-fitting space docks for three of the tankers, plus one hangar, which allows maintenance access to one tanker at a time. If pilots qualified for gas giant skimming are not too scarce, it might make more sense to use a larger fleet of smaller tankers, to reduce the overhead of the hangar. For example, if a fleet of twenty 200-dton tankers provides as much fuel capacity as these four 1000-dton tankers, they could be housed in 19 space docks (200 dtons each) and one hangar (215 dtons). That saves 285 dtons of hangar space, at cost of 16 additional pilots, 64 dtons of officer staterooms, and the possibility that a 200-dton tanker carries a smaller percentage of fuel for the mother ship.

Also, I just found the rules for demountable fuel tanks. They aren't the right terminology for what this configuration needs, because they take four weeks to install or remove. Oops. Instead, the tankers are more like drop tanks, except that they are contained in their space docks and hanger rather than jettisoned. I see that the hardware for drop tanks costs 0.4% of the total fuel capacity of the drop tanks, or 12 dtons for the 3000 dtons of jump fuel. Power plant fuel doesn't need to be transferred rapidly like jump fuel, so whatever fuel is built into the mother ship to run the power plant while the tankers are skimming can be refilled without the 0.4% overhead (but on the other hand, counting all 3656 dtons of fuel as drop tank only increases the overhead to 14.624 dtons).

Additionally, if the tankers' maneuver drives are exposed when they are docked, they could be used for additional thrust by the mother ship. However, that would require that they be armored up to the armor of the mother ship, at least on the exposed portion, which would cut into their fuel capacity.

 

[AnotherDilbert]

Additionally, if the tankers' maneuver drives are exposed when they are docked, they could be used for additional thrust by the mother ship.

There is a name and system for what you want to do: Breakaway hull. Only then can you use the fuel in the shuttles for jump fuel directly or combine thrust. It comes with a penalty of 2% of the combined volume of the ship for solid connections.

 

[wbnc]

Additionally, if the tankers' maneuver drives are exposed when they are docked, they could be used for additional thrust by the mother ship.

There is a name and system for what you want to do: Breakaway hull. Only then can you use the fuel in the shuttles for jump fuel directly or combine thrust. It comes with a penalty of 2% of the combined volume of the ship for solid connections.

hmmm 2% of total hull volume for a breakaway section...and gain the benefits of the shuttle's power and drives directly to the ship ... hmmm now that has some interesting applications...sorry sort of had a random thought....more on that when I refine it a bit.

The return on a breakaway section is sort of thin when just looking at the numbers but the tactical applications might be worth it. The Shutles can break off refuel and return while the Carrier stands High cover. You would Be saving space by using the shuttles as tankage for the ship itself since each shuttle would be removing 300 or so turns of cargo from the Main hull. As well as reactor space since the Shuttles reactors would feed power directly into the ships total power point supply when docked. ugh too much mental number crunching this early in the morning ...I'd need to look at the builds in detail to see if it were worth it to use them as breakaway sections.

 

[AnotherDilbert]

hmmm 2% of total hull volume for a breakaway section...and gain the benefits of the shuttle's power and drives directly to the ship ... hmmm now that has some interesting applications...sorry sort of had a random thought....more on that when I refine it a bit.

You might even do it on a wilderness trader: A cargo section, a fuel section, and a jump spine. The jump spine stays in orbit, the cargo section lands at a population centre, and the fuel section refuels.

 

[Annatar Giftbringer]

That wilderness trader sounds like a very interesting concept - could work as a reimagined Leviathan style ship in a way. I'm almost tempted to try to design one...

 

[AnotherDilbert]

I started to make an outline:

TL 13    Hull 5 600                                                 6 067,4    
                                       Desired    ∆TL    Rat    #    dTon    Cost    Power
Hull                                     14000                     14 000            2 800
Config           Streamlined                 2            2                   840    
Hull strength    Standard                    2            2                
Breakaway Hull                               1            1           280     560    
Repair Drones                                1            1           140      28    
                                
JumpD            Standard                    4            4     1   1 965   2 948    7 840
ManœuvreD        High Technology             1     3      1     1     137     412    1 960
PowerP  (TL12)   Advanced                          1            1     648     713   10 800
    Emergency Power                          1                  1      65      71    
                                
External Load     5 600 dT                   1                        
Drop Tank Collar  5 600 dT                   1            1     1      22      11    
Drop Tanks        5 600 dT                   4                                140    
Fuel, Jump                                   4            4     1            
Fuel, Power                                  4          4 w     1      65        
Fuel Purification                         48 h         48 h     1     140       7      140
                                
Bridge                                       1                  2     120     140    
Bridge, Small                                1                  1      40      35    
    Holographic                              1                  1              44    
Comp              CORE/40                    8           40     1              45    
Backup Comp       m/20                       4           20     2              10    
                                
Sensors           Improved                   9            3     3       9      13       12
Array             Distributed                9            3     0       6       9    
Signal Processing Enhanced                   9            2     1       2       8        2
                                
Staterooms, Luxury                           1                  1      10       2    
Staterooms, High                             4                  4      24       3    
Staterooms                                100%           38    33     132      17    
Escape Capsules                              1                 76      38       2    
Common Areas                               25%          25%     1      42       4    
Low Berths                                  10           10     1       5       1        1
Briefing Room                                1                  1       4       1    
Library                                      1                  1       4       4    
Medical Bay       5% of crew                 1                  1       4       2    
Workshop                                     1                  1       6       1    
Armoury                                      1                  2       2       1    
Cargo                                                              10 090

J-4, M-1, 10000 dT payload, MCr 6000
It has three bridges, computers, sensors for three breakaway sections.
It remains to divide the components into the three sections.