Efficient space only freighter design

[MasterGwydion]

So in your view, when a ship is maneuvering in space, no one feels anything?

I haven't extensively thought about it, but my assumption has always been that artificial gravity does two things - it provides an 'up', which is uniform across the ship, and it can negate specific gravity created by the M drive, in one direction.

Turning, turbulence, reactions to an explosion, all continue to feel to the passengers how they would feel in a car; just like in a large bus, you can accelerate and move quite fast forward, without noticing, but if you go through a sharp corner, even slowly, you have to hold on to avoid falling over.

If you're a large ship, it takes you longer to turn. This is why there are piloting checks - if you dont feel anything, and size doesn't matter, you could adjust perfectly and 95% of piloting checks wouldn't be required. The only ones that would matter are where you are aiming for a relatively small spot, in a very limited amount of time.

Again, i could be missing things as i usually just operate under this assimption without thinking about it, but i dont think gravitics and inertial compensators imply perfectly granular perfectly real time gravity control.

One of the "common gravity trap" types are the airlocks or whole passageways where you can alter the gravity to repel borders. Crank it up to 6Gs or change its direction so that up becomes down or down becomes left, switch it up every round and beat the to death against the walls of your ship. Pretty sure that was in High Guard, but I do not have My books in front of Me at the moment.

This would indicate that gravity can be individually controlled in different parts of the ship.

 

[J. L. Brown]

One of the "common gravity trap" types are the airlocks or whole passageways where you can alter the gravity to repel borders. Crank it up to 6Gs or change its direction so that up becomes down or down becomes left, switch it up every round and beat the to death against the walls of your ship. Pretty sure that was in High Guard, but I do not have My books in front of Me at the moment.

This would indicate that gravity can be individually controlled in different parts of the ship.

Yeah; "Gravity Pong" -- it was one of the standard tactics for repelling boarders. Another was getting everyone into their vacc suits as part of going to battle stations; then turn off all the lights, on-board gravity, life support, etc & get the whole ship down to vacuum. Voila! No sudden explosive decompression, no fires to fight from combat damage, and anyone coming onto the ship (and, presumably, are not intimately familiar with its' layout) is at a disadvantage against the defenders. Also, no noise from on-board shooting, fighting, or booby-traps. Naval vessels made this routine practice, but civilians (and pirates) often do not.

Another point of distinction was that navy ships were all tail-sitters -- it gave the option of performing beyond the limits of your Inertial Compensators.

I don't remember where it comes from, though -- I cannot swear that was Traveller.

 

[phavoc]

Your explantion does not actually answer the question. Vacuum and 0G are not the same thing. The vast number of cargo ship designs have the cargo in areas with life support and (artificially supplied & controlled) gravity. Gravity can be turned off or knocked out without affecting any other functions of the ship, including life support.


That is what you are trying to prove, yes. Your assertion is poor support for itself. I disagree; there seem to be strong economic incentives for using gravitics to make manipulating cargo easier, faster, and more efficient. While prototype gravitic technology may lack the refinement to do anything fancy, at TL 9 gravitics are mature and commonly available -- later TLs will show some refinements (just how much per TL is a matter of some controversy) probably by getting rid of redundant lower-TL methods which had been retained as 'back-ups' as gravitics becomes more reliable and accepted.




Okay, so you two are on the same page, then.

Imagine a ship at or above TL 9 -- where gravitics becomes commonly available. The ship is a cargo craft, and designed as a belly-lander; an Empress Marava or Fat Trader are perfect examples. The cargo is in an area with life support, artificial gravity, and 'inertial compensators'. The ship accelerates straight ahead at 1G -- unless all of the contents are accelerated at the same rate, anything not accelerated flies backwards; which is where our 'inertial compensators' enter the picture. The IC gravitics make sure everything in the volume gets the same acceleration, cancelling out the felt effect of the 1G drive inside the ship. So far so good.

Now, the ship is on approach to the high-port, and has to turn to port. The bow moves to the left, while the stern moves to the right; the center of the ship twists counter-clockwise but does not experience a lateral acceleration. Stuff in the center of the ship does not need lateral acceleration by the IC gravitics -- but the stuff 1.5m ahead of the center does. So does the stuff 15m ahead of the center of the ship -- and it needs much more acceleration than the stuff closer to the center; while stuff aft of the center need acceleration in exactly the opposite direction. If the ship is accelerating or braking while turning, then the center of rotation changes.

The artificial gravity already handles all this, even at TL 9.

I think we are close in our views, but still some disagreement. Vacuum and zero-G are not the same thing - but typically occur together unless one is in an artificial environment. And if that's the case then you are probably not going to experience either (at least not in a Traveller TL9+ setting. A cargo hold with environmental controls will have both gravity and atmosphere. Moving a container does not require zero-G conditions - and even in zero-G that container still has mass that must be overcome to move it. There are a multitude of devices available to do so, and none require vacuum or zero-G conditions. With gravity-lifting thrown into the mix you have even more ways to do so - and no need to put the container or its' contents into a zero-G condition that may cause the cargo inside to shift.

Gravitic's is certainly not a requirement for moving cargo - however it does give you some features that today you can only get with mostly fixed infrastructure. But that's not germane to having cargo experience zero-G conditions while in transit. Those two ideas are very much separated from one another.

As I understand the grav tech in Traveller that's not well explained, both gravity and inertial dampening are created in a ship. The people in the ship experience a gravity field that is basically the same as what a person on a planet does - and they feel none of the acceleration or maneuvering effects of the ship. That is also extended to all objects within the ship. The books do a poor job of explaining the how's and why's of this, but that's the general effect. And that field has a limited strength (which gets murkier in MGT where you have high-burn thrusters that can add greater accelerations to ships). But the general rule of thumb is that everything and everyone inside the ship experiences gravity and acceleration at 1G and on the same plane regardless of the movement of the ship itself - even if it's violent movement. This occurs regardless of the direction or location of any part of the ship, so long as power is maintained to the onboard gravity / intertial dampening field.

 

[Nelphine]

I had stepped out of the discussion, as i generally disallow gravity pong (and therefore extend that to disallowing control of gravity in very granular spaces), but i realize it is a common trope.

However, I would rather have gravity control in large chunks (one of which could be the entire cargo hold, but anything less than about 1/4 of the ship irks me). This could still be plenty for 0g gravitic loading and unloading.

So my next question is: how do you synchronize the unloading or loading between the ship and whatever its docked with? My thought is that a rail system within one or the other could work very effectively. 0g is in place, rails are locked, cargo containers dont move. Click button, rail for identified container unlocks. Click button, energy is exerted, and container moves along the rail to its destination, very simple and smooth, with very little anything needed. Destination outputs some energy to slow the container down. Great.

But that rail system is effectively unique to every ship or station. Even more, it has to be extraordibarily precise to avoid being launched and damaged without a way to slow it down. So, when the container leaves the ships rail system, it gets launched into the other ship/station, without that precise method to slow it down.

How do we overcome that, that doesnt end up simply being just as slow as the previously quoted time to load or unload?

 

[phavoc]

I had stepped out of the discussion, as i generally disallow gravity pong (and therefore extend that to disallowing control of gravity in very granular spaces), but i realize it is a common trope.

However, I would rather have gravity control in large chunks (one of which could be the entire cargo hold, but anything less than about 1/4 of the ship irks me). This could still be plenty for 0g gravitic loading and unloading.

So my next question is: how do you synchronize the unloading or loading between the ship and whatever its docked with? My thought is that a rail system within one or the other could work very effectively. 0g is in place, rails are locked, cargo containers dont move. Click button, rail for identified container unlocks. Click button, energy is exerted, and container moves along the rail to its destination, very simple and smooth, with very little anything needed. Destination outputs some energy to slow the container down. Great.

But that rail system is effectively unique to every ship or station. Even more, it has to be extraordibarily precise to avoid being launched and damaged without a way to slow it down. So, when the container leaves the ships rail system, it gets launched into the other ship/station, without that precise method to slow it down.

How do we overcome that, that doesnt end up simply being just as slow as the previously quoted time to load or unload?

If you put your cargo container in zero-G, then you put the load inside it in zero-G. Which means unless your load is secured for that sort of thing you run the risk of it shifting and getting damaged when it come under gravity conditions again. That could occur multiple times during it's entire time in transit, thus you'd be forced to accommodate that. Not impossible at all, but it does mean more time and effort in the loading process and then ensuring it's fully secured at all times. Some loads will easily accommodate that effort, others it will add time and expense to making it so. One could make the assumption that any load destined for space transit will automatically get loaded/tied down that way then this issue becomes immaterial. It's just been my experience with cargoes that everyone involved will do the minimum required (including those who are paying for it). The exception I have (usually) seen is with aircargo - a load shifting in-flight can literally cause the plane to crash (ex - the 747 crash in Bagram when cargo broke loose during takeoff, shifted the center of gravity and plane crashed). I have seen LOTS more truck cargo shift and loads collapse on themselves due to poor loading, incorrect straps being placed, etc. Much more rare for trucks to crash due to load shifts, but not unheard of. Space craft characteristics make that very unlikely, but cargo's getting damaged in transit due to that sort of thing are more likely. Thus the idea that keeping cargos under gravity during transit at least will eliminate that possibility.

How the interface works between two ships gravity fields is a big unknown. The question(s) there would be if there is any sort of disturbance/shift when crossing from one field to the next. Passenger traffic is a good example of where that would be more or less unacceptable to happen if there was a way to prevent it. We really have no idea how the fields work other than they can be projected from an emitter in floor plating. So if we go with the simplest example, crossing one plate to another is probably a non-issue if they are relatively set to the same level. I forgot where in the literature it talked about being able to rapidly shift or alter the grav field on floor plating as a way to defeat / slow down boarders, and somewhere else it had talked about how you could set individual rooms to different grav field strengths, so it does tend to indicate that you should be able to cross fields without too much disruption or issue.

One could use multiple types of systems to move cargo. A lifting-type device works, as would say grav forklifts/loaders, or even something as simple as putting retractable wheels in the floor and simply rolling the cargo out. That last method is very simple, and elegant, and with very little engineering you can make an entire room like that and lift/lower any combination of wheels to move the items. We did it with air cargo containers and one person could move 4,000lbs by themselves that way (mass, of course, remained... braking could be interesting if you let it get away from you!).

There are many, many ways to move it, including rail-type devices. So very much depends on your setup. Assuming a container-only area, then fixed infrastructure like a rail system makes a lot of sense. It's cheap, it's easy to maintain, and it's simple. Other methods work equally as well for general cargo types, and the addition of grav tech gives you a full 360 degree movement capability.

 

[J. L. Brown]

If you want to avoid gravity pong, you might declare that interior gravity can only be changed slowly; perhaps from 0G to maximum G in six minutes. That leaves the ships able to maneuver, but makes the change in gravity per 6s too small to be a threat. Of course, dedicated military ships might be able to disable or overcome that particular 'safety feature'. But 'acceleration compensators' are still going to be problematic.

For cargo it is still easy, since the entire cargo hold is affected. Whatever gets accelerated requires as much time (and distance) to stop (at an equal deceleration) as it took to get up to speed. So the cargo ship decides to unload with 0.01G of 'compensation'; it first communicates this to the dock. The dock sets up for deceleration of 0.01G in a patch of deck plates immediately in front of the ship -- and everything in that area is now being accelerated towards the ship's cargo hatch at ~10cm/s^2. Some few (carefully calculated) grav plates between the ship and the designated 'recieve cargo' area along the path are left at normal (uncompensated) 0G -- this needs to be at least half the length of the cargo bay (less if you are doing fancy stuff like using different accelerations on each end) on the cargo ship.

Meanwhile the loadmaster on the cargo ship makes sure everything is clear, all the remote-release twist-locks securing the cargo to the deck are released, all the remote-release twist-locks holding the cargo together are secure, all personnel are accounted for, and etc, and waits for the 'ready' signal from the dock. When the dock signals ready, then the entire cargo bay 'compensates' for 0.01G of acceleration.

The cargo moves to the dock in five phases:
1} the entire load is accelerated at 0.01G (this is very breif, as the lead parts of the cargo should exit the cargo bay almost the moment the cargo starts moving),
2} the rear of the load is accelerated at 0.01G, and the rest in not in active acceleration,
3) the front of the load is being decelerated at 0.01 G, the middle is under no acceleration, but the rear portion is still being pushed at 0.01G,
4} the cargo is entirely out of the cargo area of the ship, and the rear is in 0G, while the front is being slowed at 0.01G,
5} the entire cargo is in the designated area & being decelerated at 0.01G -- but this is momentary, and the cargo is either stationary or moving very slowly. At this point the station can cease the 'compensation' and restore normal 1G conditions.

The cargo deck of a subsidized merchant is 46.5m long, so it should be emptied in less than a minute. This supposes that the tiny little subby will be completely loaded with containers (which can be & are secured together) as opposed to palletized or break-bulk cargo (which is not), and (along with the dock) is familiar with the standard practices of the big-fish cargo liners. A medium freighter (delivering 6k dTons in 250 dTon 'cubes' of 25x 10dTon cargo containers) might have a cargo deck 360m long, and be emptied in three minutes.

 

[Nelphine]

Thats.. not quite what i was envisioning. Its one thing to make everything 0g, and then use some force to move the containers. But youre not, youre making gravity go in a direction that isnt 'natural', and under my assumptions, this means it affects everything, including things like the operator and nearby life support or plumbing systems.

I dislike that idea. Im not against gravity pong because of the sudden changes - im fine with sudden changes. I dont like gravity pong because of the idea of localized control.

Im not against gravity pong because you can slam your opponents around, im against it because of the granular control. I dont like the idea of perfectly controlling a sliding gravity control that allows you to slowly slip just the containers you want from one place to the other.

If we have that level of gravity control, dont fire missiles at each other. Throw gravity bombs that rip the ship to pieces. Throw objects at relativistic speeds from bizarre directions.

I dont like the can of worms that opens.

You want to set the whole area to zero g, sure, i can accept that, but it leaves you with how to catch it. Using modulated perfect gravity control, i dont like.


But i accept it is a reasonable interpretation to the game rules. Just not one im happy with.

 

[J. L. Brown]

Thats.. not quite what i was envisioning. Its one thing to make everything 0g, and then use some force to move the containers. But youre not, youre making gravity go in a direction that isnt 'natural', and under my assumptions, this means it affects everything, including things like the operator and nearby life support or plumbing systems.

I dislike that idea. Im not against gravity pong because of the sudden changes - im fine with sudden changes. I dont like gravity pong because of the idea of localized control.

Im not against gravity pong because you can slam your opponents around, im against it because of the granular control. I dont like the idea of perfectly controlling a sliding gravity control that allows you to slowly slip just the containers you want from one place to the other.

If we have that level of gravity control, dont fire missiles at each other. Throw gravity bombs that rip the ship to pieces. Throw objects at relativistic speeds from bizarre directions.

I dont like the can of worms that opens.

You want to set the whole area to zero g, sure, i can accept that, but it leaves you with how to catch it. Using modulated perfect gravity control, i dont like.


But i accept it is a reasonable interpretation to the game rules. Just not one im happy with.

Sure, and your TU reflects how you envision the workings of the universe; every TU is different, because all the players & GMs are different and prioritize different things. That was one of the early strengths of Traveller -- it did not originally have an 'official universe', and groups could play Star Wars, or Lensman, or a host of other sci-fi backgrounds. There are still rules for warp drives and hyper-drives and other exotic stuff in the rules, even if they are never intended to show up in the OTU. One of the strengths of applying GURPS Ultra-Tech to GURPS Traveller is they explicitly had options for various 'tech pathways' -- some universes had 'safe-tech' where AI was deliberately crippled so that it could never run wild; some had an emphasis on medicine and biotech, some had no cybernetic enhancements at all, some had gravitics only at much later TLs, and some had it at lower TLs & included probability manipulation technologies, some had personal deflectors but no energy weapons, etc, etc, & etc. The GM could choose their preferred path (or paths) and use them as a handy template to adjust TL, availability, and sophistication of wide swathes of various technologies. It was a neat tool.

Anyhow, I don't think the way the Third Imperium stuff talks about gravitics implies serious gravitic weaponry like you are envisioning. It looks like (from High Guard) the best that gravitics can do at TL 15 is 9G of acceleration and compensation -- and 9G makes for an incredibly wimpy weapon. NATO 5.56 bullets move at ~990 m/s, and reaches that speed in less than a meter, so ~100k Gs of acceleration; people generally pass out around 4G (unless especially hardy or properly equipped), and the skeleton probably won't fail until around 90G. If someone really wants to fling stuff super fast, then the rules already have Gauss weapons, rail-guns, and mass-drivers.

 

[MasterGwydion]

I had stepped out of the discussion, as i generally disallow gravity pong (and therefore extend that to disallowing control of gravity in very granular spaces), but i realize it is a common trope.

However, I would rather have gravity control in large chunks (one of which could be the entire cargo hold, but anything less than about 1/4 of the ship irks me). This could still be plenty for 0g gravitic loading and unloading.

So my next question is: how do you synchronize the unloading or loading between the ship and whatever its docked with? My thought is that a rail system within one or the other could work very effectively. 0g is in place, rails are locked, cargo containers dont move. Click button, rail for identified container unlocks. Click button, energy is exerted, and container moves along the rail to its destination, very simple and smooth, with very little anything needed. Destination outputs some energy to slow the container down. Great.

But that rail system is effectively unique to every ship or station. Even more, it has to be extraordibarily precise to avoid being launched and damaged without a way to slow it down. So, when the container leaves the ships rail system, it gets launched into the other ship/station, without that precise method to slow it down.

How do we overcome that, that doesnt end up simply being just as slow as the previously quoted time to load or unload?

Simple, UNREP System. Use the hostile boarding airlocks as an example. At higher tech levels, there is no physical passageway between the ships, it is basically done with gravity manipulation or at least the description written there may help this conversation.

As to the fine gravity control, it is a requirement. If you only can control the gravity on your ship in "blocks" then you kill your entire crew everytime you maneuver under thrust as the G-forces will literally crush your crew. This is simple to explain. A crewmember stands in the bow of the ship. Another crewmember stands in the stern of the ship. You have been accelerating from your jump point to the Starport for the last hour or so and need to turn to avoid another object (ship, rock, pirate, etc.). How do you turn your ship? Almost any move you make will exert different forces on the crewmembers in different parts of the ship. For that reason, you need finely controllable gravity controls, because if you do not have that, you all die. It also has to be controllable in 3 dimensions.

In any game that includes gravity manipulation as a common trope of the game, it requires Newtonian thinking for how that effects the game on a macro and micro scale, more so when gravity control devices can be made small enough to hide on a person such as a custom gravbelt.

 

[J. L. Brown]

As to the fine gravity control, it is a requirement. .... How do you turn your ship? Almost any move you make will exert different forces on the crewmembers in different parts of the ship. For that reason, you need finely controllable gravity controls, because if you do not have that, you all die. It also has to be controllable in 3 dimensions.

In any game that includes gravity manipulation as a common trope of the game, it requires Newtonian thinking for how that effects the game on a macro and micro scale, more so when gravity control devices can be made small enough to hide on a person such as a custom gravbelt.

That has pretty much been my point; the way the world of the game is explained, certain things seem like they already must be true.

If GMs do not examine the consequences of various technology choices ('Personal shield belt that makes you immune to all weapons? Sure, no problem!') ahead of time, overlooked stuff may cause problems down the line. For example -- TL9 elevators probably do not use cables & counter-weights (electric linear accelerators are cheaper, simpler, and more reliable, with maybe basic gravitics on the top-end models); so any plan by the PCs to rappel down the TL 11 elevator cables to quickly get to a lower level does not work, nor does a plan to install a sensor (or an explosive) 'on the cables'.

The kind of gravitic hand-waves used for 'acceleration compensators' and belly-lander ship designs shapes the rest of the world in ways that may not be instantly obvious; but can have big impacts in the background. This has come home to roost on the topic of freight handling, and what big cargo-line ships would look like -- because those ships (and how they operate) can be expected to influence the behavior of the parts of the game universe where the players interact.

 

[phavoc]

That has pretty much been my point; the way the world of the game is explained, certain things seem like they already must be true.

If GMs do not examine the consequences of various technology choices ('Personal shield belt that makes you immune to all weapons? Sure, no problem!') ahead of time, overlooked stuff may cause problems down the line. For example -- TL9 elevators probably do not use cables & counter-weights (electric linear accelerators are cheaper, simpler, and more reliable, with maybe basic gravitics on the top-end models); so any plan by the PCs to rappel down the TL 11 elevator cables to quickly get to a lower level does not work, nor does a plan to install a sensor (or an explosive) 'on the cables'.

The kind of gravitic hand-waves used for 'acceleration compensators' and belly-lander ship designs shapes the rest of the world in ways that may not be instantly obvious; but can have big impacts in the background. This has come home to roost on the topic of freight handling, and what big cargo-line ships would look like -- because those ships (and how they operate) can be expected to influence the behavior of the parts of the game universe where the players interact.

Bingo!

 

[Nelphine]

As to the fine gravity control, it is a requirement. If you only can control the gravity on your ship in "blocks" then you kill your entire crew everytime you maneuver under thrust as the G-forces will literally crush your crew. This is simple to explain. A crewmember stands in the bow of the ship. Another crewmember stands in the stern of the ship. You have been accelerating from your jump point to the Starport for the last hour or so and need to turn to avoid another object (ship, rock, pirate, etc.). How do you turn your ship? Almost any move you make will exert different forces on the crewmembers in different parts of the ship. For that reason, you need finely controllable gravity controls, because if you do not have that, you all die. It also has to be controllable in 3 dimensions.

In any game that includes gravity manipulation as a common trope of the game, it requires Newtonian thinking for how that effects the game on a macro and micro scale, more so when gravity control devices can be made small enough to hide on a person such as a custom gravbelt.

Or, turning subjects the passengers to Gs? Don't turn too fast? If you're big, you have more limited turns?

 

[J. L. Brown]

Or, turning subjects the passengers to Gs? Don't turn too fast? If you're big, you have more limited turns?

Military ships almost certainly turn very quickly; it is life-or-death. The Tigress maneuvers at 6G, has a crew of 2890, and is around 238m in the smallest dimension -- and other ships are famously less compact. It is not difficult to imagine such a ship undertaking maneuvers that would be very hard on the crew if the inertial compensators stop working.