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Classic Traveller Discussion on the granddaddy of them all, Classic Traveller!

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  #21  
Old December 24th, 2018, 03:55 PM
sabredog sabredog is offline
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I checked the pages in AHL Book 1 to see what the deal was with frontier refueling something like that and got different info from TCS and other (albeit skimpy) sources.

The AHL has 35,000 tons of fuel. The four fuel shuttles can skim and process (with their onboard refineries as they fly to and from the AHL) 350 tons each in 3 hours. If all four skim at once they can tank up the AHL in 27 four-shuttle trips, or 3 days total.

Refueling using free water from a world takes twice as long (6 hours per load). Using ice takes 9-10 hours per shuttle load.



The AHL can skim herself, but it is risky given her size. The rules don't say how long it takes, other than the ship just dives in, opens her scoops, and slurps it up. It is pretty dramatic, though.

The ship, due to size and design, and be damaged or even lost doing this.
The ship can have fuel tanks collapse from hull stress and buckling. The Maneuver Drives can be buffeted and damaged to even the point of failure - which then results in the loss of the entire ship.

All this sounds weird considering how routine all the rest of the Traveller rules, editions, and games that mention it make it sound. It is discussed as routine procedure when fleets Jump into a system, and the AHL is the only ship in the lists that I've ever seen that mentions having to use fuel shuttles to do this safely. How bad would it be to skim a Tigress and lose the thing because the drive get knocked around?
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  #22  
Old December 24th, 2018, 04:07 PM
sabredog sabredog is offline
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Quote:
Originally Posted by mike wightman View Post
Not quite, the rules are a little fuzzy on if you need all three drives. You definitely need a power plant for your maneuver drive, but it doesn't explicitly state like it does in future editions that you need a power plant at least equal to the jump drive - this is how the x-boat began.

Also, the '77 edition (the one I have right here) specifically states the power plant is for internal power and the maneuver drives, and that it has to be the same size as the M-drive, accordingly. There isn't anything fuzzy about it.

In the Fighting Ships supplement it says the X_boats don't have a power plant. Only a jump drive.


It changed, like you said with the '81 edition.
I remember I had to do a lot of remodeling lists of ships when the '81 edition came out to fix that. Same with HG2 for different reasons.
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  #23  
Old December 26th, 2018, 04:59 PM
whartung whartung is offline
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Quote:
Originally Posted by sabredog View Post
I checked the pages in AHL Book 1 to see what the deal was with frontier refueling something like that and got different info from TCS and other (albeit skimpy) sources.

The AHL has 35,000 tons of fuel. The four fuel shuttles can skim and process (with their onboard refineries as they fly to and from the AHL) 350 tons each in 3 hours. If all four skim at once they can tank up the AHL in 27 four-shuttle trips, or 3 days total.

Refueling using free water from a world takes twice as long (6 hours per load). Using ice takes 9-10 hours per shuttle load.

The AHL can skim herself, but it is risky given her size. The rules don't say how long it takes, other than the ship just dives in, opens her scoops, and slurps it up. It is pretty dramatic, though.
Right, the question is does the shuttle take 3 hours because it's 350 tons? Or just because it's a shuttle? i.e. if it was a 1000 ton fuel shuttle, would it also take 3 hours? Do the scoops scale with the ship? Does the AHL ship fuel up in 3 hours if extra excitement?

It's not a bad baseline ruling. You could make the ship refuel time be something like the cube root of the fuel volume in hours. 10,000 tons in 100 hours. Seems kind of high.

Mind, the 3 hours for the fuel shuttle includes travel, skimming, travel, and transfer.
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  #24  
Old January 2nd, 2019, 02:43 PM
ffilz ffilz is offline
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One thing of note is that the 1977 rules don't mention WHAT star ship fuel is, just that it can be skimmed from gas giants (unrefined) or purchases (refined and unrefined) from star ports.

I'm inclined to take that at its word. Sure, I'm using deck plans based on 1 dTon is the volume of 1 ton of liquid hydrogen, but that doesn't mean the fuel has to strictly be liquid hydrogen.

Doing this I don't have to allow water or ice as fuel sources...

Since I run a Books 1-3 campaign, I don't have to worry about fuel purifiers (and note that per the 1977 rules, a military ship isn't totally immune to issues of unrefined fuel, so it doesn't necessarily have fuel purification, it just can more safely use unrefined fuel).

Frank
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  #25  
Old June 18th, 2019, 09:25 PM
AndyW AndyW is offline
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I've thought a bit about GG skimming over the years. It seems to me that the typical GG is a high G environment, often with winds that would shame a typical F11 tornado. Skimming must be a little like skipping a stone across a pond, too steep an entry and you dive deep and are lost, too shallow and you bounce off quickly, losing the efficient collection of Hydrogen. Come in too hot and you incinerate, come in too slow and you lose the momentum needed to get out unless you are running drives that top the gravitational acceleration. A great deal of handwavium is needed to justify the process on many fronts.

It occurs to me that a 1 G ship is playing Russian roulette to dive into a GG atmo at all. That said, I had a little take away from the Starship Operators Manual. It mentions overdriving an M-drive for the purpose of off axis thrusting, and that a competent engineer could do this to multiples of the drives rating for short periods. So I got to thinking that in addition to involving a pilot in the skill roles to successfully perform the maneuver, the engineer would play a crucial role in giving the necessary juice to get out.

Taking it further I conceived of a maneuver that dumps the high speed skimming process for something I call the "dunk and guzzle". Which is rather like submerging an empty glass, mouth up in a pool of water until the water starts pouring in.

The pilot/navigator chooses a relatively calm yet dense pocket of the GGs atmo, orients the vessel stern down and drops as low as safely practical in the atmo, opens the scoops and collects gas. The engineer strokes and coos and baby talks the M-drives all the while, thrusting at an appropriate multiple of its typical thrust. Enough to maintain the right depth. EMS and densitometers would provide "weather forecast" for the purpose of orienting the vessel's streamlining to minimize buffeting.

Hull stress and heating would be minimized and it would be easier to concentrate on regions and/or strata that are richer in hydrogen.

This is a process that I would include IMTU.
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  #26  
Old June 19th, 2019, 12:09 AM
Fovean Fovean is offline
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Very cool idea.

It would be quite a spectacle, sinking slowly into the mists with the occasional electrical or radiation storm on the horizon.

I would probably rule it takes an extra 2D hours or some such, to make the more difficult but faster “hot skim” (the skipping stone maneuver) a necessary option when under a time crunch during an adventure. But then the dunk n guzzle could lead to a cool submarine hunt scenario, all sweaty, tense sensor rolls with an occasional burst of fire... I wonder how missiles do in a GG atmosphere?
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  #27  
Old June 19th, 2019, 11:59 AM
pavel.k pavel.k is offline
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It sounds nice - slow sinking to the sun. But would the ship be able to escape? The Sun has gravity 27.9 G and escape velocity is 617.5 km/s.
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  #28  
Old June 19th, 2019, 12:51 PM
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Quote:
Originally Posted by mike wightman View Post
Nope. orbital mechanics doesn't work like that, especially when you have a magical maneuver drive that can provide a minimum of 1g continuous thrust for a month or more.
it's much easier just to find a lump of ice (water/methane/ammonia) to extract hydrogen from.
The problem is time whether a thrust of 9.8 m/sec^2 add enough delta-vee fast enough to overcome the loss from flying through an atmosphere. There will be a depth at which you lose so much per second that your maneuver drive can't counteract it.

The higher the thrust rating the deeper that depth is.

I created Traveller ships in Orbiter Space simulator and see what it took to fly them including flying through the atmosphere of a gas giant. The issue mostly cropped up with 1-G and 2-G maneuver drives.
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  #29  
Old June 20th, 2019, 06:37 AM
AndyW AndyW is offline
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Quote:
Originally Posted by pavel.k View Post
It sounds nice - slow sinking to the sun. But would the ship be able to escape? The Sun has gravity 27.9 G and escape velocity is 617.5 km/s.
You couldn't do that, but a 2-3G Gas Giant wouldn't pose too much of a problem if one is talking a few hundred degrees vs. several million.
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  #30  
Old June 20th, 2019, 06:43 AM
AndyW AndyW is offline
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Quote:
Originally Posted by Fovean View Post
. I wonder how missiles do in a GG atmosphere?
I would think that they would end up acting a lot like depth charges. They would have issues achieving a direct impact, due to cross winds, but could be set to go off when a proximity detonator detected a metallic substance nearby. That would take your sub hunt scenario up a few notches.
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