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Old 09-06-2018, 02:42 PM   #41
hal
 
Join Date: Aug 2004
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Default Re: Collapsibles and Drop Tanks

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Originally Posted by ak_aramis View Post
Mike, you're neglecting that Marc has again reiterated that dropped tanks are generally not reusable. Until TL15, they are automatically destroyed by being dropped - the issue is clarified in T5, as anything smaller than the jumping vessel is damaged by the jumping vessel.

Essentially, you're arguing a point that the designer himself responded against; you are neither advancing rules as intended nor setting as intended.

Fine grist for an ATU, but unreflective of the OTU as Marc Miller sees it.
Hi Aramis,
Based on your later clarification, I thought I'd go back to the above quote and then reference what you suggested.

I believe the quote you intended to use in support of your statement is this one:

"The ship with its Jump Drive almost always operates properly; other objects within the bubble suffer Jump Mishaps."

I'm guessing that the damage to objects within the jump field but not part of the ship making the jump, suffer damage per page 340. Not exactly an easily understood process at first glance, but at least it is there (took a while for me to find it).

In the end? It doesn't really support the statement "Until TL 15" as far or as best as I can see. Unless Jump Grid hulls aren't possible until TL 15, it would seem that a simple jettisoning of the tank beyond the effect of the jump field would be sufficient for them to survive the jump initiation.

Frankly, I don't much worry about it - largely because the only ship to be outfitted with Drop tanks in all of the history of Traveller and documented hulls is the 300 dton Close Escort.

My one point when I brought this up to the CT-Starships mailing list - is that the implications of Drop tanks would have made sense for jump ships such as the scout ship, to have a single dTon drop tank added to its 99 dTon hull. The moment it goes into combat, it becomes a hull size zero hull, granting it a +2 defensive bonus against attacks instead of a +1 defensive bonus under High Guard rules.

High Guard came out in 1979 and in 1980. Fighting ships came out in 1981 as did Traders and Gunboats. Since then, there hasn't been ANY other ship design published with drop tanks, despite the obvious implication that using drop tanks for a scout ship is useful. When I built ships for the Billion Credit Squadron game on CotI - I used almost 100 dton hulls for the fighters, included a small stateroom to insure that I'd have longer endurance for the fighters - a move that paid off when I went up against someone who had the same idea that I did (using hard to hit fighters to both attack and screen against enemy ships). Between the best computers, highest agility, and smallest hull possible, those buggers were hard to hit!

In any event - the only published material in JTAS regarding ships with drop tanks are from the convention competition for High Guard's Billion Credit Squadron. (I think JTAS 10). That doesn't count as a Third Imperium design so much as a wargame design for a competition.

So - as far as that goes, that's why I don't bother with worrying much about Drop tanks. Nearly 40 years of published material and they still don't have anything outside of the Gazelle?

Just as a side note? One discussion we're having now is whether or not the El Dorado from TRILLION CREDIT SQUADRON's Islands Cluster back story, could have gotten back (it was a strike cruiser if that helps) to the Third Imperium despite the fact that it would have had to jump 7 parsecs back.

It states that it arrived by means of a misjump, and through auxiliary tanks, was able to return. So, I created a Strike Cruiser based off of the T20 version of the Strike Cruiser on 70,000 dtons. There was talk about mounting external auxiliary tanks to add more fuel capacity - but doing that decreases the jump capacity of the ship's engines and increases its fuel consumption for the same jump amount. An interesting conundrum if you will. Is this a case where the writer wrote something not supported by the rules?

If the ship is able to use its 100 dton bays as cargo spaces for internal fuel bladders, can take out staterooms and convert them into cargo space, and remove the spinal mount - it can assign 70% of its internal hull to fuel carrying capacity and still retain jump 3 capabilities. Perhaps a combination of external tanks plus removing internal stuff might make the task easier for the El Dorado to return. <shrug>
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Old 09-07-2018, 03:04 AM   #42
ak_aramis
 
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Default Re: Collapsibles and Drop Tanks

The reason for TL 15 is the reuse roll - which is in MGT (somewhere, but I'm too lazy to look it up at 0200.

It's also been discussed for 5.10 (which I have a partial draft for, but can't quote the same way, because it's a working draft, not a final.).

For drop tanks to be reusable changes the nature of trade.
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Old 09-07-2018, 04:18 AM   #43
hal
 
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Default Re: Collapsibles and Drop Tanks

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Originally Posted by ak_aramis View Post
The reason for TL 15 is the reuse roll - which is in MGT (somewhere, but I'm too lazy to look it up at 0200.

It's also been discussed for 5.10 (which I have a partial draft for, but can't quote the same way, because it's a working draft, not a final.).

For drop tanks to be reusable changes the nature of trade.
Playtest material being what it is, we'll have to wait until it gets published. The Errata in T4 concerning Drop tanks - would largely be missed by anyone who doesn't have it (despite Don McKinney's work).

When I went looking for the scatter rules for jumps that involve using a Flux roll, I was shocked at the potential for ships to be months away from their intended target (assuming I understood the rules from T5 correctly) and the Mongoose Traveller rules involving accuracy of jump could result in millions of kilometers being off target for a jump (per the introductory short story). In other words, there isn't much uniformity at this point in time where rules are concerned between the versions of Traveller. I suspect that the Drop tank rules are going to be of a similar vein - different between versions. T5.10 will hopefully fix some of those issues, but when I looked at the scatter rules for the jump within system from a somewhat accurate astrogation roll, I thought that appearing outside of Pluto's orbit would be so unappealing that few GM's would use it. Hopefully, T5.10 will avoid that issue.

(note: when aiming directly for a mass such as a planet or star - the scatter rules don't come into effect. When aiming for an orbit on the other hand, the result is equal to a flux roll plus the orbit aimed for. So aiming for orbit 12, could result in reaching orbit 5 or as far away as orbit 17. Nasty!)

Since I no longer frequent Citizens of the Imperium due to issues there (Left a message with the moderator there and explained why I was leaving) and have since run into others with issues with the Moderator - I don't have the ability to discuss T5 material with those who seem to love it best. <shrug>

On that note, thanks for the reference specifics and the MgT reference. I'll see if I can find the Mongoose Reference in either of the 1st edition core rule book or the 2nd edition High Guard book - those are the only real reference books I have for MgT. :(
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Old 09-08-2018, 03:26 PM   #44
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Default Re: Collapsibles and Drop Tanks

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Originally Posted by ak_aramis View Post
Drop tanks are going to have to clear the field or be effectively destroyed.
Does T5 go into detail as to exactly when and how the fuel in the jump tanks gets used?

Clearing drop tanks would be pretty easy. They effectively have the same acceleration as the ship, because the ship can just turn them loose and then decelerate. If you have to jump from a dead stop (relative to what?), then it's still not an issue, as you can just add a vector, release, then decelerate.

So the question isn't where the tanks are, but where the fuel is. If it's LBB style, so all that fuel gets turned into energy stored in jump capacitors, then you can easily empty the tanks and clear them before you jump.

If it's the later style, where fuel is continually bleeding out over a week to form a shield in jumpspace, then you can't drop the tanks at all. They'll have to be inside the jump field to be taken along, effectively part of the volume of the ship, as they're not empty until you reach your destination.

You could take out the notion of capacitors, and say that all that fuel gets burned at once to enter into jumpspace, but that happens immediately, so there's no time to clear your drop tanks. (Such ship designs wouldn't include the tanks in the lump field, so most of them don't come along, which automatically damages the tanks. Proper design would keep that damage minor, though, maybe just a couple of struts with pipes that are intended to be replaced. If a jump field has a reasonably sharp and predictable boundary, that is.) This style implies a huge surge capacity in your power plant output, though.
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Old 09-08-2018, 06:05 PM   #45
hal
 
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Default Re: Collapsibles and Drop Tanks

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Originally Posted by Anaraxes View Post
Does T5 go into detail as to exactly when and how the fuel in the jump tanks gets used?

Clearing drop tanks would be pretty easy. They effectively have the same acceleration as the ship, because the ship can just turn them loose and then decelerate. If you have to jump from a dead stop (relative to what?), then it's still not an issue, as you can just add a vector, release, then decelerate.

So the question isn't where the tanks are, but where the fuel is. If it's LBB style, so all that fuel gets turned into energy stored in jump capacitors, then you can easily empty the tanks and clear them before you jump.

If it's the later style, where fuel is continually bleeding out over a week to form a shield in jumpspace, then you can't drop the tanks at all. They'll have to be inside the jump field to be taken along, effectively part of the volume of the ship, as they're not empty until you reach your destination.

You could take out the notion of capacitors, and say that all that fuel gets burned at once to enter into jumpspace, but that happens immediately, so there's no time to clear your drop tanks. (Such ship designs wouldn't include the tanks in the lump field, so most of them don't come along, which automatically damages the tanks. Proper design would keep that damage minor, though, maybe just a couple of struts with pipes that are intended to be replaced. If a jump field has a reasonably sharp and predictable boundary, that is.) This style implies a huge surge capacity in your power plant output, though.
T5 states that the fuel is used Quickly and stored in the capacitors, such that the drop tanks can then be used and discarded. So, it seems that the answer to your question regarding when the fuel gets used is before the jump.

My problem with this whole mess is thus:

If the jump field surrounding the ship conforms to the ship due to a jump grid based jump drive - the field only extends to about a meter from the surface of the ship. When it enters into jump space, it is highly unlikely that the drop tanks will be within the jump field for such a ship.

If on the other hand, the jump field is a globe shape - then the size of the field generated is dependent upon how many cubic meters the ship has. It is essentially the cube root of cubic volume in meters if the ship, times 20

The problem I have is this...

If the drop tanks are not within the jump field, no harm, no foul. If your ship is accelerating at 1 G for 10 seconds, you will have reached a velocity of 98 meters per second. Displacement (distance travelled) is equal to 1/2 Acceleration * time^2, then it would only take about 7 second's worth of 1 g acceleration to pull ahead by 220+ meters. Those drop tanks shouldn't even be taking damage if the whole process to enter jump takes 20 minutes or 40 minutes (at least for a 100 dton hull). A 50,000 dton hull, at 1 G, would only need some 19 seconds to accelerate at 1 G to get outside of its field.

I honestly don't think being within a jump field is an issue UNLESS the jump occurs at precisely the moment that the fuel was drained from the tank itself.

Mind you, that only happens when dealing with a globe shaped jump field instead of a ship that was designed with a jump grid.

Your mileage may vary.
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Old 09-10-2018, 11:38 AM   #46
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Default Re: Collapsibles and Drop Tanks

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My problem with this whole mess is thus:
Pretty much my thought in my second paragraph. Given M-drive performance, it's easy to arrange any reasonable separate you want from the drop tanks before jump without affecting your travel time -- even in terms of combat turns. The tanks won't be in the jump field when you jump.

The answer would thus have to be that you can't store that energy for very long, so there's not much time for the tanks to clear the ship before you have to jump (or dump that energy somewhere less useful, like into the capacitors themselves, or the power planet, or something else lethal).

At least you could also use that same handwavium to (mostly) explain why those high energy density, yet unstable, jump capacitors aren't used anywhere else. It'd be a lousy way to power your Air/Raft. Might see them in pulse lasers or such technology.
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Old 09-10-2018, 12:23 PM   #47
Fred Brackin
 
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Default Re: Collapsibles and Drop Tanks

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The answer would thus have to be that you can't store that energy for very long, .
I want to warn you against having every Free Trader in the 3I turning 20 tons of hydrogen into energy every time they jump. Per p. 82 of UT annihilating a single gram of antimatter (+ a gram of normal matter) can produce a 43 kiloton explosion.

So if you're talking about total conversion of 20 tons instead of 2 grams you're looking at 2,000,000 x that or 86 gigatons of TNT.

If you only fuse that H2 you're looking at 2 orders of manitude less but have to ask what you did with the fused hydrogen and what about the waste heat? It's easier to think of total conversion being 100% efficient but a fusion power plant that can fuse that quatity of hyrdrogen in 1 Traveller turn and produce
no waste heat is at least two miracles instead of just one.

Jump capaciters are also mentioned in the description of the Black Globe where you can charge your Jump capaciters from the BG but still require "fuel" to Jump.

So you don't turn your fuel into energy and store it in the Jump capacitors.
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Old 09-10-2018, 01:10 PM   #48
hal
 
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Default Re: Collapsibles and Drop Tanks

As Fred's response so amply suggests - no one ever really asked "What happens to the hydrogen" and it more or less slide for a LONG long while.

Sadly, there are inconsistencies involved over the various versions, and the implications are rather staggering.

That is largely the reason I think, that drop tanks as a whole, were left alone for the ship designs since 1981, and has (to the best of my knowledge) only been included for "legacy" reasons (someone created the Gazelle and it was never decanonized - so we have to include it too).

In the end? If you want it for your Traveller Universe, go for it. If you want it for the OTU, then we either go with the presumption there really ARE other ship designs with Drop tanks and they are in steady use, or there aren't, and it all ended with the Gazelle.

My serious problem with it is that now, if you jump within the 100 diameter radius of a larger ship, it affects your jump.

If you go with THAT presumption, does it not also mean that if you attempt to jump anywhere NEAR a large ship, that you will automatically end up 100 diameters away from the ship? If you have a busy port world that has HUGE freighters constantly arriving in port from other worlds, how often will a ship's exit point be shunted away like a ping pong ball when you have large amounts of Ships heading In or out from port, or in parking orbits away from the high port simply because they don't want to worry about congestion or what have you?

Life was sure simpler in CT days! ;)
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Old 09-11-2018, 11:27 AM   #49
Mike Wightman
 
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Default Re: Collapsibles and Drop Tanks

In the OTU by 1105 drop tank equipped merchants have been used for over a decade in the core sectors of the Imperium.
In the OTU drop tanks are single use if they are dropped.

Remember the OTU is not perfectly described by the rules as written, the rules are modified to describe the OTU setting. If the setting contradicts the rules change the rules to match the setting. The possible exception to this are the rules in T5 which describe MWM's vision of the OTU, but even then there are contradictions between his novel and the rules, and he has mentioned during interviews setting material that isn't in the T5 rules as yet.

As to how the hydrogen is used by the jump drive during jump, the original article said this:
Quote:
When the jump drive is activated, a large store of fuel is fed through the ship power plant to create the energy necessary for the jump drive. In the interests of rapid energy generation, the power plant does not work at full efficiency, and some of the fuel is lost in carrying off fusion by-products, and in cooling the system.
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Old 09-13-2018, 05:50 PM   #50
ak_aramis
 
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Default Re: Collapsibles and Drop Tanks

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Originally Posted by Anaraxes View Post
Does T5 go into detail as to exactly when and how the fuel in the jump tanks gets used?

Clearing drop tanks would be pretty easy. They effectively have the same acceleration as the ship, because the ship can just turn them loose and then decelerate. If you have to jump from a dead stop (relative to what?), then it's still not an issue, as you can just add a vector, release, then decelerate.

So the question isn't where the tanks are, but where the fuel is. If it's LBB style, so all that fuel gets turned into energy stored in jump capacitors, then you can easily empty the tanks and clear them before you jump.

If it's the later style, where fuel is continually bleeding out over a week to form a shield in jumpspace, then you can't drop the tanks at all. They'll have to be inside the jump field to be taken along, effectively part of the volume of the ship, as they're not empty until you reach your destination.

You could take out the notion of capacitors, and say that all that fuel gets burned at once to enter into jumpspace, but that happens immediately, so there's no time to clear your drop tanks. (Such ship designs wouldn't include the tanks in the lump field, so most of them don't come along, which automatically damages the tanks. Proper design would keep that damage minor, though, maybe just a couple of struts with pipes that are intended to be replaced. If a jump field has a reasonably sharp and predictable boundary, that is.) This style implies a huge surge capacity in your power plant output, though.
The prior canon is that jump fuel is used in under 20 minutes, and is spent whether or not the jump happens; you don't have time to drain empty and eject, as you finish using it as you enter jumpspace.

I don't have time at the moment to dig the T5 answer out accurately, but...

IIRC, the JDrive is actually an overdrive on the PP, coupled to the astrogation and initiator; the fuel has to be fed steady rate, and once started, there's no delay.
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