Tug Concept

[Sageryne]

Hi all,

I am working on a project and I came up with an idea for a tug/boarding 20-dTon launch. I think that tugs are a very useful and practical type of sub-craft that we don't typically see in Traveller games.

My concept is that the launch has engines far out of proportion to its size. To move a 100-dTon ship at 1G costs = 1% or 1-dTon. If you placed a 1-dTon manoeuvre drive on a 20-dTon launch it would go 5Gs (since 1-dTon engine = 5% of 20-dTons = 5G drive). The next thought I had was what if you put more than one of those engines on the launch?

The maximum gravitic manoeuvre drive at TL15 is 9G, so it is clear to me that you can't "stack" gravitic drives (i.e. a 20-dTon tug with 4-dTons of manoeuvre drive cannot go 20Gs). However, it seemed to me that 4 x 1-dTon drives could have a greater cumulative pushing power.

I have attached my design as a screen-shot.

It is expensive, but based on my logic above:

1. The tug alone could go 5Gs (quick response time to get to a ship in need of help).

2. The tug could push a 100-dTon ship at 3.33G (4-dTons of manoeuvre drive moving 100+20 = 120-dTons)

3. The tug could push a 400-dTon ship at 0.95G (4-dTons of manoeuvre drive moving 400+20 = 420-dTons)

4. The tug could push a 1000-dTon ship at 0.39G (4-dTons of manoeuvre drive moving 1000+20 = 1020-dTons)

Thoughts?

- Kerry

 

[AnotherDilbert]

It is expensive, but based on my logic above:

1. The tug alone could go 5Gs (quick response time to get to a ship in need of help).

2. The tug could push a 100-dTon ship at 3.33G (4-dTons of manoeuvre drive moving 100+20 = 120-dTons)

3. The tug could push a 400-dTon ship at 0.95G (4-dTons of manoeuvre drive moving 400+20 = 420-dTons)

4. The tug could push a 1000-dTon ship at 0.39G (4-dTons of manoeuvre drive moving 1000+20 = 1020-dTons)

Thoughts?

Yes, absolutely. You can even use a completely oversized drive, acceleration is just limited to the TL max.

You would need some connector like a tow cable or a docking clamp to get a grip on the ship.

 

[Sageryne]

My concept uses a forced linkage apparatus to connect to the ship. I visualized this as a large "pusher plate" that had an electromagnet in it for connecting with metallic hulls. It would also have grapples for connecting to non-metallic hulls and a tow cable.

I do envision these tugs as working in pairs (or more), like you see assisting ocean going vessels.

 

[Geir]

My concept uses a forced linkage apparatus to connect to the ship. I visualized this as a large "pusher plate" that had an electromagnet in it for connecting with metallic hulls. It would also have grapples for connecting to non-metallic hulls and a tow cable.

On the forced-linkage apparatus, the HighGuard Update sort of killed it for smallcraft:

The ship attempting forced linkage must have a Thrust advantage of at least one over the opposing ship and may not be less than half the
tonnage of the target ship. (p.57)

Invalidated a lot of my boarding craft designs, so I don't like the clarification much... but it is there.

 

[Arkathan]

Yeah, I use cargo nets (hauler nets) and tow cables for that purpose.
Seems to me, it would be too easy for a forced linkage to buckle under the strain of maneuvering with a largish ship, since the linkage volume is not dependent on ship size.

 

[rinku]

It still works as a tug, as the towed ship isn't trying to resist. That High Guard gear is basically for a hostile grab.

Outside of the combat rules it's also not unreasonable to use fractional G thrusts. You likely don't want to be moving a big ship around the highport or spacedock at very high velocities. It only takes a 0.1G thrust (1 metre per second per second) a few seconds to get things moving at faster than walking speed, which feels about as fast as you'd want a starship to be moving around near port facilities.

If you need to move hulls serious distances, you'd likely want a ship sized tug.

 

[ottarrus]

Certainly tug boats are necessary. Any high port is MUCH happier with IN cruisers or mega-freighters being nudged into docking position by their employees in tugs than some random pilot they don't know.
Tugs would be more efficient movers of cargo containers or 30-ton cutter modules too. I can see tugs coming in sizes from 20 tons to a couple hundred tons [you need lotsa power to move warships and bulk freighters around].
I don't think tugs are ignored so much as they are background... everybody sees tugs, worker bee pods, and other 'harbor craft' all the time, but they're just not the craft adventurers interact with all the time.

 

[Sageryne]

If anyone is reading this from Mongoose, it would really be nice if there was an official "pusher plate" (preferably with an electro-magnet) addition.

I agree, the Forced Linkage Apparatus isn't exactly what I was looking for.

I also think that tow cables are a bit suspect, as they are based on a percentage of the ship they are on, not the ship they are trying to two.

Cargo nets also seem a little bit kludgy if a 20-dTon tug was trying to move a 1000-dTon vessel.

Most real world tugs seem to push their target. Sometimes they do take ships in tow, but that tends to be in open ocean rather than in port.

- Kerry

 

[rinku]

I'd go with assumed standard couplings, like the tow bar on cars. The starships have fittings that the tugs securely attach to. No special cost involved, just part of the hull cost.

Actually, the High Guard equipment you probably want here is a Docking Clamp. There's nothing there that says the ship equipped with the docking clamp has to be the bigger one. Big M-Drive plus a class III or IV Clamp would do the job.

You might want several tugs to maneuver a big ship. More efficient for applying counterthrust too.

 

[Galadrion]

Yeah, I use cargo nets (hauler nets) and tow cables for that purpose.

On this note, is there anything official on how much a cargo net can hold? I'm looking at designing a tug and/or a tug drone (for use with a mineral refinery, as mentioned in High Guard 2022), I can't seem to find anything about what a cargo net's capacity is.

 

[Arkathan]

On this note, is there anything official on how much a cargo net can hold? I'm looking at designing a tug and/or a tug drone (for use with a mineral refinery, as mentioned in High Guard 2022), I can't seem to find anything about what a cargo net's capacity is.

I edited, because I really wanted to talk about the interplanetary hauler nets and jump nets. Both are sized to fit whatever volume you design for.
The drone operated cargo net expands to gather lose containers from a volume not exceeding twelve cubic kilometers. The ship cannot jump with the net extended, and I would be hard pressed to allow maneuvering while the drones are deploying, other than to match vectors with the targets.
The haulers haul, the Cargo Net is a slow and careful cargo scoop that brings stuff to you for internal storage (or attached external cargo space).

 

[rinku]

Real pilots use cargo scoops, as Elite intended...

 

[Galadrion]

The drone operated cargo net expands to gather lose containers from a volume not exceeding twelve cubic kilometers.

*Blink* Twelve cubic kilometers? Unless I've slipped a digit (or several), that means that a single cargo net can hold on the close order of a BILLION displacement tons. Um... that seems a bit insane.

 

[rinku]

That's the extent it can go to haul things in. It's not intended to do anything other than bring cargo to the ship. Think trawler nets.

If you want a net to put things in and drag behind the ship you want the Jump Net. Either the jump capable one or the cheaper interplanetary one.

 

[Galadrion]

That's pretty much what I had in mind. I was planning for a tug equipped with some very hefty maneuver engines, a laser drill, and something to allow it to bring the material back to the mother mining ship. I was trying to work out how much a (for example) 100-ton mining shuttle could bring back in. If that twelve cubic kilometers is the capacity, then I can't see it needing any more than one net. That leaves most of the tug available for maneuver drives and the associated other equipment (power plant, fuel tankage, et cetera - the items which will need to be scaled with the M-drive). Of course, that means that a single mining laser is also going to take for freaking ever to reach the effective cargo limit...

Updated to add: Ah, the interplanetary jump net (extremely misleading name, there!) is a lot closer to what I had in mind. In fact, given the speed of a laser drill, the tug probably wouldn't even need a cargo net - just a couple of grappling arms to gather up the "harvest" and place it in the jump net.

Now to work out the balance between maneuver engines and cargo towing capacity - I don't think I want the minimum acceleration to drop below 1 G, nor have it go much above 2 G when fully loaded. Promises to be an interesting bit of number-juggling.

 

[Condottiere]

Easier to leverage a tow rope.

 

[AndrewW]

Easier to leverage a tow rope.

 

[rinku]

That's pretty much what I had in mind. I was planning for a tug equipped with some very hefty maneuver engines, a laser drill, and something to allow it to bring the material back to the mother mining ship. I was trying to work out how much a (for example) 100-ton mining shuttle could bring back in. If that twelve cubic kilometers is the capacity, then I can't see it needing any more than one net. That leaves most of the tug available for maneuver drives and the associated other equipment (power plant, fuel tankage, et cetera - the items which will need to be scaled with the M-drive). Of course, that means that a single mining laser is also going to take for freaking ever to reach the effective cargo limit...

Updated to add: Ah, the interplanetary jump net (extremely misleading name, there!) is a lot closer to what I had in mind. In fact, given the speed of a laser drill, the tug probably wouldn't even need a cargo net - just a couple of grappling arms to gather up the "harvest" and place it in the jump net.

Now to work out the balance between maneuver engines and cargo towing capacity - I don't think I want the minimum acceleration to drop below 1 G, nor have it go much above 2 G when fully loaded. Promises to be an interesting bit of number-juggling.

To be honest, a couple of mining drones would likely be best on a small craft for the gathering.

 

[rinku]

Easier to leverage a tow rope.

My concern with simple tow cables over a grapple or securely attached to the hull by nets is maneuvering. But I guess the ship can stop thrusting, detach, reposition, reattach and apply thrust.

 

[Condottiere]