Refuelling Times

George Kelln

Mongoose
Greetings,

As I having yet found any information on refuelling time at Starport; I have come up with the following: Does it make sense in the Traveller Universe? Is there some information that I may have missed or yet found.

Today, on 21st Century Earth, a Boeing 747-8 has a fuel capacity of 238,609 litres (17.67 dtons). An airport fuel truck using one pressurized hose usually refuels an airplane at around 1135 liters per minute and it takes 3h 30mins to refuel the Boeing 747-8. If a second hose is used (2270 litres/minute) the time is halved (1h 45mins). A Boeing 747 using two fuel trucks with dual hoses (4540 litres/minute) would be refuelled in around 52 minutes. The cost to refuel the plane would be (US) $315,170.

Adapting this standard to the Traveller universe, the standard speed (abiding to all safety regulations) to refuel a ship is 1000 litres of liquid hydrogen per minute through a 100mm (4 in) diameter pressurized steel braid hose. At a Class A and some Class B starports this amount is increased to 2000 litres per minute with the addition of a second hose.

In a Class A and most Class B Starport, on each dock there is one hose per 500 dton of ship able to docked in the berth. At other lesser quality starports/spaceports there will be a refuelling point and possible line ups.

1 Displacement Ton (dton) = 13.5 cubic metres (13,500 litres) of liquid Hydrogen

The standard Type S Scout Courier holds 40 ton (540,000 litres) of fuel

Therefore, the standard time to refuel a bone-dry Type S Scout Courier is:

270 minutes (4h 30m) in a Class A/B Starport
540 minutes (9h) in any other class starport/spaceport

The standard Type T Patrol Corvette holds 120 ton (1,620,000 litres) of fuel

Therefore, the standard time to refuel a bone-dry Type T Patrol Corvette is:

405 minutes (6h 45m) in a Class A/B Starport
810 minutes (13h 30m) in any other class starport/spaceport

Does it many sense?

Cheers
 

Geir

Cosmic Mongoose
Ballpark, it makes sense.
In the core rulebook (2022 Update) on page 156 it says:
"Either way, it typically takes 1D hours to refuel a typical ship."
(Either way refers to refined versus unrefined fuel)
It would make sense that there would be more or bigger fuel ports for bigger ships and in bigger landing/docking berths, allowing parallel refueling operations to the ship's tanks. Since that's a pretty wide range, you could just assume 3-4 hours for normal operations and call it good.

This assumes a starport refueling. Local conditions, such as inadequate facilities, a fuel operator strike, a need to bribe someone to move up in the line, etc., could obviously delay refueling further. But unless you like to annoy your players, complications should only happen when they're important to the adventure in some way.
 

Condottiere

Emperor Mongoose
Depends on the equipment involved, at either end of the transaction, and in the middle.

At the upper end, Tigress two hundred kilotonne fuel tanks emptied within six minutes.

At the lower end, ship's boat floating on top of a lake, siphoning off the top through a rubber hose.

Underway replenishment, as far as I'm aware, does offer clear guidance on transfer rates; the default fuel filler pipe is probably inconveniently located.

Fuelling could take place directly from the dock, or through a separate spacecraft; separate tanks probably have separate fuel filler pipes, or may be interconnected.
 

PsiTraveller

Cosmic Mongoose
UNREP system allows for 20 tons of fuel transfer per hour per ton of UNREP installed pg 47 of Highguard. So a refuelling ship could move a lot of fuel per hour if they had enough UNREP tonnage installed.
 

phavoc

Cosmic Mongoose
For refueling might be better to look at rockets rather than aircraft - or at least the smaller scale starships might be around avgas. But some things to consider is the nature of hydrogen and the need to purge gas while filling, and you are still have some limits due to the need to not create lots of gas that may get trapped and have to be purged.

As in interesting aside, for the main fuel tank of the shuttle, if they had to go into a tank after fueling it took them 20hrs to do a helium purge before it was safe to go in. I'm guessing opening to vacuum might be a bit different though.

This sort of detail is always a nice add to round out the gaming setting. More information is useful to create scenarios for players. And you can skip it if you want, but often the little details can really help sometimes.
 

AnotherDilbert

Cosmic Mongoose
Traveller Companion said:
A ship can skim fuel equal to 1% of its hull tonnage per pass, with a pass typically requiring 2D minutes. Thus, a vessel wanting to obtain 20% of its hull tonnage in fuel in the Deep layer will need 20 passes averaging about seven minutes each, for a total of 140 minutes. Skimming would take twice as long in the Shallow layer but would also be safer.

If skimming can be done in an hour or two, normal refuelling shouldn't take days, but that is just an opinion.
 

phavoc

Cosmic Mongoose
Also keep in mind how the fuel tanks are structured in aircraft - often the fueling is done directly into the tank. The pipes between the different tanks are the limiters in transfer speed. The shuttle main tank had fueling lines that were 17" in diameter. And you are limited by just how much pressure you can put into the pipes - they aren't going to engineer them to take insane pressures to speed refueling since it's not really needed.
 

Condottiere

Emperor Mongoose
That's where the plumbing comes in.

In theory, you could keep the jump drive turned off and use that as the fuel hub or distribution system.
 

Arkathan

Cosmic Mongoose
phavoc said:
Also keep in mind how the fuel tanks are structured in aircraft - often the fueling is done directly into the tank. The pipes between the different tanks are the limiters in transfer speed. The shuttle main tank had fueling lines that were 17" in diameter. And you are limited by just how much pressure you can put into the pipes - they aren't going to engineer them to take insane pressures to speed refueling since it's not really needed.

It's a starship. They ARE going to over-engineer the Hell out of it. Like a nuclear power plant, where some valves that are the size of a man's forearm cost $.25 Million to replace, due to the need to keep the zoomies on the inside. You've just got a tech reduction of cost as TLs exponentially improve your manufacturing capabilities.
 

phavoc

Cosmic Mongoose
Arkathan said:
phavoc said:
Also keep in mind how the fuel tanks are structured in aircraft - often the fueling is done directly into the tank. The pipes between the different tanks are the limiters in transfer speed. The shuttle main tank had fueling lines that were 17" in diameter. And you are limited by just how much pressure you can put into the pipes - they aren't going to engineer them to take insane pressures to speed refueling since it's not really needed.

It's a starship. They ARE going to over-engineer the Hell out of it. Like a nuclear power plant, where some valves that are the size of a man's forearm cost $.25 Million to replace, due to the need to keep the zoomies on the inside. You've just got a tech reduction of cost as TLs exponentially improve your manufacturing capabilities.

That's true. Standard practice would have them design it to take stress - but a reasonable amount of stress. A 200-300% stress increase is not out of line for aircraft (that doesn't translate into building wingboxes able to take 27G of stress though - it's not always linear and not always applicable to everything).

But that costs money for materials/engineering and space. So if the average pressure for it might be 10lbs/sq in, the failure point may be around 25lbs/sq in. There are a number of variables here. The space shuttle was a starship (well, a spaceship, we can't currently build starships) and it had limitations that the engineers had to live with. Sure, they might have been able to use titanium and exotic alloys everywhere and increase the capabilities and decrease weight - but that would have made the cost too high. Because players don't actually have to deal with the costs (let alone the long-term implications of it and the maintenance) they tend to ignore that sort of thing. Iridium crappers belong in every head on a yacht sounds something like an uber wealth client would do... till they got the bill.
 

Arkathan

Cosmic Mongoose
phavoc said:
. The space shuttle was a starship (well, a spaceship,

The space shuttle is more of a prototype spaceship than a standard Traveller spaceship.
We're halfway to TL 8.
 

phavoc

Cosmic Mongoose
Arkathan said:
phavoc said:
. The space shuttle was a starship (well, a spaceship,

The space shuttle is more of a prototype spaceship than a standard Traveller spaceship.
We're halfway to TL 8.

So what constitutes getting beyond a prototype? The SS was a small production run,but the only planned prototype was the Enterprise. All the other ones operated as planned (well, there were two exceptions...)
 

Arkathan

Cosmic Mongoose
phavoc said:
Arkathan said:
phavoc said:
. The space shuttle was a starship (well, a spaceship,

The space shuttle is more of a prototype spaceship than a standard Traveller spaceship.
We're halfway to TL 8.

So what constitutes getting beyond a prototype? The SS was a small production run,but the only planned prototype was the Enterprise. All the other ones operated as planned (well, there were two exceptions...)

Enterprise had a wood frame, IIRC.
I meant from a High Guard pov.
 

phavoc

Cosmic Mongoose
Arkathan said:
Enterprise had a wood frame, IIRC.
I meant from a High Guard pov.

I have never read anything about Enterprise having a wood frame. For everything I've ever read it was originally built with the idea that it would, at some point, be refitted with real equipment to make it launch worthy. I know they didn't install some systems, most of the tiles were fake, etc, but never have I heard that the Enterprise itself had a wood frame. Are you perhaps referring to a pre-pre-production mockup and not the actual one that was used to test the air transport and mate to the main fuel tank?

I think the scale of needs/production would dictate a prototype or not. The shuttle was always meant to be a small fleet and we are not yet at the level of regularly launching to space (Though we COULD be, we just don't see the actual need as of yet - politically and socially at least. We certainly, as a planet, could benefit from it).
 

Condottiere

Emperor Mongoose
Well, I've speculated on the possibility of using wood as hulls.

Considering the alternatives, graphite, titanium and/or aluminum, unless there's some physics reasons regarding the structural strength and/or flexibility of wood during reentry or launch, hard to imagine.
 

Arkathan

Cosmic Mongoose
phavoc said:
Arkathan said:
Enterprise had a wood frame, IIRC.
I meant from a High Guard pov.

I have never read anything about Enterprise having a wood frame. For everything I've ever read it was originally built with the idea that it would, at some point, be refitted with real equipment to make it launch worthy. I know they didn't install some systems, most of the tiles were fake, etc, but never have I heard that the Enterprise itself had a wood frame. Are you perhaps referring to a pre-pre-production mockup and not the actual one that was used to test the air transport and mate to the main fuel tank?

I think the scale of needs/production would dictate a prototype or not. The shuttle was always meant to be a small fleet and we are not yet at the level of regularly launching to space (Though we COULD be, we just don't see the actual need as of yet - politically and socially at least. We certainly, as a planet, could benefit from it).

A distinct possibility. I remember being disappointed back in the late seventies when they said the Enterprise wouldn't be going to space, and that it was just a glide tester. It was probably the fiberglass I was thinking of with a forty+ year memory gap.

What I mean is performance wise. Limited effectiveness when compared with a High Guard standard design. Making an expensive and less effective version at a lower tech level than normal.
 

phavoc

Cosmic Mongoose
Arkathan said:
A distinct possibility. I remember being disappointed back in the late seventies when they said the Enterprise wouldn't be going to space, and that it was just a glide tester. It was probably the fiberglass I was thinking of with a forty+ year memory gap.

What I mean is performance wise. Limited effectiveness when compared with a High Guard standard design. Making an expensive and less effective version at a lower tech level than normal.

The shuttle performed as expected, utilizing the tech available at the time. Like many expensive vehicles, some things are just too expensive to retrofit. The original design for the shuttle came from the UK and it was supposed to be a "space truck". NASA took ahold of it and made it much more complex and grandiose. Once they started building it they stuck with the design even though newer tech came around. The original computing power was pretty damned low. It wasn't until much later in the fleet's lifetime did they upgrade the computer systems to something approaching modern. You regularly see this, especially in large fleets.

So by all the standards I would say the shuttle shouldn't be considered a prototype, just a small-build fleet. This is not at all unreasonable with big and expensive vehicles - again, look to the military and see how they build very expensive but small fleets - the Forrestal class of US carriers (and the later Kitty Hawk upgrade). The Kidd class (4 ships built for Iran but taken over by the US). One could say the Gerald Ford class carrier is a prototype, bu it's just the first of it's class. Enterprise is a prototype nuclear carrier, since it's a one-off and the Nimitz-class made a lot of changes based upon what was learned with Enterprise.

But the Space Shuttle didn't fall within that sort of category. It was just a small run of vessels. For Traveller one might argue the Kininur-class was somewhat the same, however that design just turned out to be faulty and was discontinued after a very small production run. I think scale really plays into the definition.
 

phavoc

Cosmic Mongoose
I get your point, but when a gaming system takes a real world idea/concept and significantly nerfs / increases it, that's a failure on the gaming system.

And there is always good ol fashioned common sense that should be used - hopefully by game designers PRIOR to them publishing rules.

And that's the point I'm trying to make here.
 

feld

Banded Mongoose
To the OP: this might be more Real World (tm.) information than you want but here's some stuff for inspiration.
1. NASA Kennedy Space Center Liquid Propellants Safety Handbook from 1965
https://ntrs.nasa.gov/api/citations/19650018358/downloads/19650018358.pdf

2. (now cancelled) NASA Safety Standard for Hydrogen and Hydrogen Systems
https://www.energy.gov/sites/prod/files/2014/03/f11/871916.pdf

Both of these seem like they're more detailed than you'd like but perhaps they will be of use.

I like to humbly advocate for less "analogous" and more "real world" science in the science fiction but your desires may vary.

v/r
feld
 
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