How long to fuel up a starship?

[Caelarch]

In my new MT game I have the players running just hours ahead of a warrant for their arrest. They have just jumped into a system with a Class B port. They know the fuzz is right behind them but they have no idea how long they have.

My question is, on a Pop 5, Ni world with a Class B starport, how long does it take to land, load up on 210 kl of high grade refined H2 and dust off? I want to time the fuzz's arrival to just as they are screwing the gas cap back on. So assuming the crew lands and gets H2 ASAP, how long should it take?

It doesn't make sense to me that there would be that many ships arriving and being fueled all at once, so I can imagine that it is more a matter of pump time, which I'd be prepared to say is minutes, and certainly less than 1/2 hour. If anything, I'm thinking they raise suspicions with the authorities when they show up and demand "Fuel; right now. No, I don't want to talk about buying cargo or taking on passengers or deal with customs. I'm not getting off the boat. Just fill 'er up and make it snappy!"

 

[Icosahedron]

Probably even less is said about this in CT. It's an omission that I've tripped over several times. AFAIK no edition answers it (I could be wrong there, it's a long time since I waded through the TNE tome).

You could say that it's up to the Referee:
"Just as the pipes are withdrawn and your fuel-cock closes, you are hailed on the comm..."
but it wears a little thin, sometimes. It would be good to find some filling-times for RL ocean-going ships and/or aircraft, just to get a ball-park figure, but I could easily imagine the transfer taking several hours, possibly more than a day for capital ships. A Free Trader, probably much less, but I don't think it would be anywhere near as quick as filling your car...

 

[aramis]

I figure a single 10cm flow channel, probably 15cm exterior, armored and chilled pressure hose probably dumps about 10KL/min (this is 2.5x the nominal flow pressure limits for a 5" fire hose). This is only going to have a reasonable reach of about 50m at this flow...

I also figure that a typical tankage has one feeder port per 20Td (280kl), so if the locals can and will hook up multiples, you're looking half an hour.

Why one per 20Td? Because a fuel hit is 20Td of lost fuel in CT Bk2.

 

[BlackBat242]

Lets see here...

Using TL6 example, "up to" 1000 US gallons per minute for the boom on a KC-135 tanker [307 gal/min for the hose]... and 3.89 liters per gallon, we get 3,890 liters per minute possible fill rate [1,194 l/min for the hose].

Using TL7 example, 1,100 US gallons or 4,279 liters per minute for the boom on a KC-10 tanker.



Using a KC-135 boom rate, we get 53.98 minutes (or basically an hour) to transfer 210kl.

Using a KC-10 boom rate, we get 49.07 minutes.

Using an aerial refueling hose rate, we get 175.85 minutes... or basically 3 hours!


What TL is the refueling equipment at the Class B starport?

 

[aramis]

Typical class B is at least TL9... because the yard can fix drives A-D.

 

[by_the_sword]

My question is, on a Pop 5, Ni world with a Class B starport, how long does it take to land, load up on 210 kl of high grade refined H2 and dust off?

About two minutes before the cops show up.

My opinion: Do some fake calculations behind the screen, roll some dice and get a surprised look on your face before you tell the PC's that they finished fueling and are headed for the Jump Point just as the opposition shows up in system to chase them down.

 

[far-trader]

Somewhere (had a quick look but couldn't find it) in CT is a reference to the fastest x-boat turnaround on record. ISTR it was a few minutes, which implies a speed of refueling for up to 40tons of fuel.

I don't see that one can really compare pumping avgas or any other room temp liquid to transferring LH. I'd dig around for NASA fueling of the space shuttle instead.

And I'd not worry about it, as others have suggested make it up to create the tension you desire. Though I can understand wanting a figure for refueling time for a number of reasons.

The bigger issue for timing this is the random jump time for the involved ships. Even if the PC's jumped first there's a fair chance the chasers will arrive in the system before they do and be waiting for them. Presuming they know where to go in the first place.

 

[aramis]

NASA pushed LHyd 179kl/min through the 43.18cm diameter fixed line of the Shuttle ET umbillical, at 220-235kPa. They pushed LOx at 66.5kL/min at 137-152kPa

Note that fire hose pumps can often operate up to about 1700kPa; but that the shuttle ET is acceleration and pressure fed, not pumped, at the above rates.

my 10cm channel at 10kL/min should be about the same flowrate as the shuttle external tank per unit cross-sectional area, so the pressure isn't that high.

Refs:
http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html
http://www.firehouse.com/forums/showthread.php?t=100761

 

[rancke]

My opinion: Do some fake calculations behind the screen, roll some dice and get a surprised look on your face before you tell the PC's that they finished fueling and are headed for the Jump Point just as the opposition shows up in system to chase them down.

Um... if the pursuers arrive at the jump limit two minutes after the pursuee lifts off from the ground, you're looking at a hazardous jump just outside the 10 diameter limit if they want to avoid a confrontation, which would give them plenty of time.

(Or do you? What if the PCs head for the jump limit on the side away from where the pursuers arrived? That gets into orbital mechanics, which is way beyond me. But my main point remains: The answer depends on a lot more than just the respective arrival times.)

And Dan is right about the jump variance being very important. Try rolling 140+8D6 or 147+6D6 (or 143.5+7D6 ) for each ship a few dozen times; add the number of hours' head start (one?) the PCs had and see how often the pursuer arrives before them anyway.


Hans

 

[by_the_sword]

To the OP:

Where do you want the game to go? Do you want the players to get caught? do you want the chase to take place on the planet or do you want the authorities to pursue them through space? If you are up for any option (even one that I haven't thought of) then just make a roll to see what happens?

1D to see what happens to the players:
1-2 They can't refuel fast enough and the cops get the drop on them.
3-4 They can't refuel fast enough but are able to escape the starport on foot/in an ATV/air-raft/ect.
5 The PC's finish fueling and they make it into orbit just as the cops jump in-system.
6 The PC's make it to the jump point and may jump before the cops arrive.

I am not telling you that my way is the right way. I am just offering an alternative to calculating pump rates for liquid Hydrogen. You as Referee, know what works best for your group. If they are the types to complain about "railroading" then maybe this option won't work for you.

 

[Caelarch]

NASA pushed LHyd 179kl/min through the 43.18cm diameter fixed line of the Shuttle ET umbillical, at 220-235kPa. They pushed LOx at 66.5kL/min at 137-152kPa

Note that fire hose pumps can often operate up to about 1700kPa; but that the shuttle ET is acceleration and pressure fed, not pumped, at the above rates.

my 10cm channel at 10kL/min should be about the same flowrate as the shuttle external tank per unit cross-sectional area, so the pressure isn't that high.

Thanks! This is exactly what I was looking for. I think I'll just ballpark fueling at 10kl/min. Maybe higher tech planets could do it faster, but this is probably a safe and reasonable way to do it- just like we don't fill out cars with the 1000 gal/min hoses that we Earth humans are technically capable of doing in certain circumstances.

I also figure that a typical tankage has one feeder port per 20Td (280kl), so if the locals can and will hook up multiples, you're looking half an hour.

Also great little nugget of color to add to the scene.

Um... if the pursuers arrive at the jump limit two minutes after the pursuee lifts off from the ground, you're looking at a hazardous jump just outside the 10 diameter limit if they want to avoid a confrontation, which would give them plenty of time.

Worse. I make jumping from within a jump shadow* vastly more dangerous than RAW-indeed bordering on simply suicidal. This particular star the players have arrived at is a dim, puny little M9 and the mainworld races around it at mere .015 AU mean orbital distance. I use a tidal model for jump distances and the math means that the star's jump shadow extends out to around .3 AU. The PCs have a solid 4 hour slog maxing out their tricked out 4G trader before they can jump.

* Not precisely the same as the canonical "jump-shadow"ing/masking. Instead the Jump shadow is the area where space is so churned up by gravity that the jump drive cannot safely engage. It is in essence my in-universe term for the "100d limit", since there is not a precise 100d limit in my universe.

The bigger issue for timing this is the random jump time for the involved ships. Even if the PC's jumped first there's a fair chance the chasers will arrive in the system*before*they do and be waiting for them. Presuming they know where to go in the first place.

I considered this. To calculate jump duration, I use 4d6 where 14 =100% (of 168 hours) and each point above or below adds or subtracts 1% of that time. The players rocked there roll, and the one pursuer who was ready to jump jumped to the wrong system. Or possibly the right one, as I am pretty sure it is where the PCs plan to jump next. I gave the pursuers a roll at a +4 advantage on the roll to represent multiple ships that left at some point after the player's jump. The players still managed to eke out around a 10 hour total head start.

As for

My opinion: Do some fake calculations behind the screen, roll some dice and get a surprised look on your face before you tell the PC's that they finished fueling and are headed for the Jump Point just as the opposition shows up in system to chase them down.

and the other suggestions like it:

I totally get where this is coming from, and from time to time I do make arbitrary plot decisions to fit the drama or keep the store going or the like. But I fall pretty hard on the "simulationist" side of the RPG gamer spectra, especially with Traveller. I do my best to keep the verisimilitude level really high on things like this. But, such decisions can be totally valid, and indeed invaluable in certain instances. If we had not been right at a stopping point when the PCs jumped last session, I probably would have rolled with something along these lines to keep the action going- but now that I can work it out, I want to be as accurate as reasonably possible.

Thanks for all the replies!

 

[Mithras]

Good call, By the Sword.

 

[Hemdian]

This is probably not applicable (for a number of reasons) but looking over the notes on the Azhanti High Lightning class cruiser in CT I see its 400 dton fuel shuttles can each skim 350 dtons of fuel from a gas giant in 3 hours, or from an ocean in 6 hours, or from an ice cap in 9 to 10 hours. These are round trip times.

Meanwhile, for a sub-1000 dton ship in a starport my wet finger in the air estimate would run something like this:

• Land
• Short cooling off period
• Clearance by customs/medical/SPA engineering
• Hook up to external power and shut down power plant
• Examine and perform remedial maintenance of the fuel tanks (and other systems) ... including inspection of tank interiors (venting trace gases and/or pumping residual fuel from one tank to another to facilitate this)
• Attach hoses for fuel/water/life support gasses
• Signal port authority to open valves for that landing pad ... then something like 7 to 10 seconds per kilolitre of fuel
• ...

So, even though the actual refuelling wouldn't take that long, with all the paperwork and so on we’re probably talking the best part of a day, at least, otherwise it looks funny.

 

[boomslang]

So, even though the actual refuelling wouldn't take that long, with all the paperwork and so on we’re probably talking the best part of a day, at least, otherwise it looks funny.

There was a rule back in CT TCS that any necessary amount of fuel could be transferred between two vessels in two 1000-second game terms.

So from an engineering standpoint, it probably takes 30-to-40 minutes for a competent crew, but from a bureaucratic standpoint, I think you make good points and half a day is probably a reasonable bare minimum. (Do not forget Bribery and Admin skills as DMs, et cetera.)

I would use the d6 table by_the_sword helpfully provided, and work the practical details backward from there as best suits the dramatic tension and storytelling.

 

[fredofmars]

The T20 "Traveller's Handbook" gives a figure on p267:

"Once the ship has landed near such a water based fuel supply, the crew may begin pumping the unrefined fuel aboard, a process that will take approximately 4 hours to complete."

That's for pumping from an unregulated source, such as a lake, ocean, or river. I'd assume that getting fuel at a starport - even unrefined fuel - will be significantly faster (for the pumping activity anyway). As previously stated, I think the bureaucracy part of the activity is likely to take quite a bit longer.

 

[Sir Brad]

Starships are refuled at the speed of Plot, unless their are rules that suspificaly preclude it or common scene (even with Belief Suspenders set to overload) tells you otherwise.

 

[Lategaming]

It has to be the "Speed of Plot" as Sir Brad says.

Otherwise..
How long does it take them to get from Jump point to starport B? More than a few hours I'd wager. So by the time they're landing, the pursuers have arrived and transmitted the warrant to local authorities (at light speed). Which will likely overtake the ship and have them flying straight into a reception party from the planet with their pursuers scant hours behind.

So unless they do something clever with transponders, land off Starbase and have the fuel shipped to them...OR you want them to get away by the skin of their teeth?

 

[Caelarch]

Thanks to everyone for the ideas and help.

I have done the math on the PC's lead time versus the time their pursuers will arrive in system. Assuiming the PCs head straight for the starport they will land around 6 hours before the first vessel with word of the warrant arrives in system. I'm going to give the players a Difficult Admin, Liason Task to see how quickly they can cut through starport red tape, and assuming success they should be breaking atmo about the time the law is jumping insystem.

Failure means they are sitting at the port when word arrives. Exceptional Failure means they are still waiting on fuel, or are sitting with hoses attached when word arrives.

Borrowing from a thread I saw here earlier, If they are still on the ground when the word arrives, the starport will attempt to lock them down with its nuclear damper. The PC's will have to power down the tractor b...er...nuclear damper to escape while the local law enforcement tries to take them into custody. Should be awesome either way!

 

[far-trader]

...Should be awesome either way!

Presuming the players don't pull the usual "throw a wrench in the ref's plans" by doing something totally unexpected

Like...

...pirate another ship in the system to steal their fuel.

...dip fuel from a local body of water (avoiding red tape and hassles with the law) and risk the misjump. Of course if it's a desert world you can strike this one off, unless the players spot a farmer's dugout,some large oasis, or a small town's water tower/cistern :smirk:

...abandon the ship on the pad and book/stowaway on the first ship leaving.

...or who knows what. Players are frustratingly clever at times. Maybe they'll even hack into the port commo and just wait for the pursuers to make contact and feed them a story about how the ship just jumped for X world, wait for the pursuers to give chase then quietly jump for Y world.

 

[Caelarch]

All of which would only be even cooler than what I expected! Some of these I know they aren't going to try. Thier ship is probably too emotionally valuable for them to abandon; even if it not the best idea I see them as standing by it to the end. Piracy is probably out, given the low traffic nature of the world. But, then again, with a deep jump shadow around the world, and thier high acceleration ship they could give it a go! I'd frankly love adding "Piracy" to the warrant against them. Maybe I'll have to mention that 1g freighter slowly lumbering toward jump as they pop in system and see how they react... <evil laugh>.