General Drop Tank Tender?

[Condottiere]

I don't necessarily think there's only the option of one size fits all.

If it were, you'd have a series of clamps, to keep the docked spacecraft in place.

 

[kilemall]

Which was quite obviously designed for a LBB2 Small Ship Universe.

This is why in my most recent thinking, external docking and towing has taken on such a prominence in what I do and post on these forums. If you can DOCK with another ship externally, you don't NEED to "pull it inside and close the doors" necessarily, so all of the "what shape is the volume of internal space?" questions get sidestepped (rather than needing a trash compactor to make stuff fit into deck plan images).

With respect to the Corsair "stowing" a 100 ton ship into its 160 ton cargo bay ... I figure that's a case of only needing to get the prize "partially" into the bay, rather than "entirely" into the bay (and shut the doors). So long as the prize can be "clamped in" and is unable to escape, that's all that's really needed. It would probably require leaving the (big) bay doors open to vacuum, but so long as the Corsair can "plug the prize" MOSTLY into the bay, that's enough. It's okay if some of the prize taken sticks out past the (open) doors.

Yet another example of why I'm of the opinion that external docking and towing rules are needed for CT.

There are, but it’s made clear it’s an engineering activity and not a routine commercial activity.

 

[Spinward Flow]

I don't necessarily think there's only the option of one size fits all.

If it were, you'd have a series of clamps, to keep the docked spacecraft in place.

Bare minimum, there's going to be a "standard" for docking connections. This may or may not vary by polity group (for reasons various and sundry).

Here is an early Solomani example undergoing static testing on the ground.

 

[AnotherDilbert]

Yet another example of why I'm of the opinion that external docking and towing rules are needed for CT.

Sure, but there are none.

We can house-rule something, e.g. add docking clamps from MgT2 (or just use MgT2 completely):

Docking Clamp
A docking clamp allows a spacecraft to carry another vessel on the exterior of its hull, typically a small craft such as a ship’s boat or fighter. This permits a ship to carry auxiliary craft without consuming valuable interior space.

A ship’s Thrust and jump capability must be recalculated when another ship occupies its docking clamp, using the combined tonnage of both ships. This will likely mean the manoeuvre drive will be operating at a lower Thrust and the jump capability may be reduced.

The size of a docking clamp dictates the tonnage of the ship it may attach as shown in the Docking Clamp table.

A ship holding another ship in a docking clamp will become unstreamlined. It takes three full rounds to release or clamp a ship of less than 2,000 tons, during which time neither ship can expand any Thrust or make any attack rolls. Larger ships take D3+3 rounds.

Note that ships held in a docking clamp can be targeted separately by an attacker. Any evasive action employed by the mothership can be applied as normal.

Note that there are some disadvantages, in addition to all the advantages.

MgT2 has a lot of other cool options, e.g. breakaway hulls, reaction drives, sensors and jamming.

 

[TamsinP]

MgT2 says 300%:

I'm guessing that reference is to the Docking Facility for space stations; for Hangars on ships it is 200%, although that could be taken as for a specific vessel rather than for any vessel of that tonnage.

 

[Condottiere]

For space stations it's three hundred percent, which sounds a bit more plausible.

If the spacecraft has odds and ends, or dispersed configuration, it should be more.

 

[AnotherDilbert]

I'm guessing that reference is to the Docking Facility for space stations; for Hangars on ships it is 200%, although that could be taken as for a specific vessel rather than for any vessel of that tonnage.

Yes, it's the Docking Facility for stations. I don't see any reason why it can't be used on ships.

The Full Hangar at 200% from the ship chapter is for a specific craft, but with plenty of space around it for maintenance.

I tend to combine minimal Docking Spaces with a few Full Hangars for maintenance.

 

[kilemall]

Just for completeness, I’ll mention the LBB5 distributed hull type that has no hangar/bay/launch tube requirement- I would assume most battle riders use that sort of jump carrier.

 

[AnotherDilbert]

Just for completeness, I’ll mention the LBB5 distributed hull type that has no hangar/bay/launch tube requirement- I would assume most battle riders use that sort of jump carrier.

It's even better for fighter carriers, as you can dispense with both the 30% hangar overhead and the launch tubes.

Dispersed seems great at first glance, but has an Achilles heel: It's unstreamlined, so can't refuel...

It's generally cheaper to make a streamlined carrier, than to include a fuel tanker on a Dispersed carrier.

 

[whartung]

Towing is a real trick.

There's that example from 2010 when the Leonov is docked to the Odyssey, and they use the Odyssey's motors as part of the push to Earth.

But, it's connected by just a tube. And the torsional forces on that connection, particularly an ad hoc connection, had to be pretty crazy.

I didn't read the book, so perhaps by judicious throttling of the two craft to limit the discrepancies in momentum between the ships, they could pull it off (Task: Engineering -- Formidable, Disastrous).

Anyone who has had the excitement of trying to tow another vehicle with something like a chain can attest to the fun and games involved with starting, stopping, not snapping cables, chains, and such. "if only we had a hard mount!"

It's one thing to mandate standard docking collars, but docking collars do not a structural mount for towing make, necessarily.

 

[Spinward Flow]

It's one thing to mandate standard docking collars, but docking collars do not a structural mount for towing make, necessarily.

That's why the external towing capacity needs to be "built into the hull as part of the original hull design of the class" (or words to that effect). It's not something that can be retrofitted on later. Kind of like how hardpoints need to be specified in the original design for a class (at least in CT) and included in the baseline construction cost. Turrets and weapons can be retrofitted on later, but hardpoints cannot be retrofitted onto a class after it has been constructed.

Now, "copying an existing class" and adding hardpoints to the copy can certainly be done ... but then you've created a new class and get to pay the architect fees again to get the plans for the new class.

So I agree with you @whartung that you can't just "slap on a docking collar" and that's all it takes to enable external towing. It's not like you can just "buy a hardpoint" and plug another craft into it and tow it around without doing more to modify the hull (and re-balance of the drives performance profiles). That's why I take the view that external towing requires enumeration of "hangar capacity equivalence" in the class design, which costs the same as a hangar bay of that capacity ... the only difference is that the capacity is specified for external loading, rather than internal loading (in other words, No Free Lunch™).

 

[kilemall]

Consuming a hard point at least seems reasonable to me.

 

[Spinward Flow]

Consuming a hard point at least seems reasonable to me.

Nice theory (and I see where you're going with it).
The problem happens as soon as you start trying to convert hardpoints (and "turrets" without weapons) into docking points for external loads. A lot of ... weirdness ... shows up almost immediately, especially if the "docking turrets" need to compete for hardpoints with the (actual) weapon turrets. If you have to "spend a weapon hardpoint" on enabling this docking feature, then armed small craft can't do it (because then they lose their 1 hardpoint and turret that ought to be loaded with weaponry).

So certainly something that "sounds right" at first blush, but then as soon as you start diving down the rabbit hole, it turns into something that is very design rules UNfriendly.

 

[kilemall]

Nice theory (and I see where you're going with it).
The problem happens as soon as you start trying to convert hardpoints (and "turrets" without weapons) into docking points for external loads. A lot of ... weirdness ... shows up almost immediately, especially if the "docking turrets" need to compete for hardpoints with the (actual) weapon turrets. If you have to "spend a weapon hardpoint" on enabling this docking feature, then armed small craft can't do it (because then they lose their 1 hardpoint and turret that ought to be loaded with weaponry).

So certainly something that "sounds right" at first blush, but then as soon as you start diving down the rabbit hole, it turns into something that is very design rules UNfriendly.

Silly me, I am into having advantages cost.

This is less docking collar and more attachment point for linked power/control/towing, much more then simple docking egress.

I’ve been doing a lot of visualization of the spaces between decks and hulls and justifying the hardpoint rules.

IMO the hardpoint carve out has a lot to do with internal support structure, routing of multi failover fuel/power/control/life support/computer/fire control lines, and something allowing for hard attachment at speed and close enough for jump fields ought to cost.

 

[Spinward Flow]

I’ve been doing a lot of visualization of the spaces between decks and hulls and justifying the hardpoint rules.

IMO the hardpoint carve out has a lot to do with internal support structure, routing of multi failover fuel/power/control/life support/computer/fire control lines, and something allowing for hard attachment at speed and close enough for jump fields ought to cost.

And I'm right there with you.
At first blush it certainly LOOKS LIKE a promising option.

Then you run into the "theory vs practice" problem.

Already ahead of you on the hardpoint carve out representing internal support structure.
However, problems arise as soon as to you start wanting to do determine limits on external load towing (because there are going to have to be limits to the "linkage" and not just on the drive performance).

This also creates potential problems for deck planning.

For example, my 328 ton J3/3G SIE Clipper that I've been working on has 7 external docking points on it, accessed through grav lifts:

1. Dorsal wing port
2. Dorsal centerline midship
3. Dorsal wing starboard
4. Ventral wing port
5. Ventral centerline forward
6. Ventral centerline midship
7. Ventral wing starboard

External load capacity is up to 672 tons (because 328+672=1000 tons).
672 tons of hangar berthing capacity under LBB5.80 costs Cr2000 per ton (so MCr1.344 for 672 tons of external towing capacity).

Shoehorn that into some kind of "hardpoints and turrets" paradigm and things BREAK DOWN, really fast.

 

[kilemall]

Not really an issue long as you aren’t trying to do this partial/streamlined. Attach a dispersed structure to attach point, containers attach to the structure, make sure it’s centered.

Or engineer/streamlined section is tug attached to dispersed structure pushing.

 

[Spinward Flow]

Not really an issue long as you aren’t trying to do this partial/streamlined.

Yeah, not going there.

Makes things a lot easier to just assume that (just like with external demountable fuel tanks) ANY combination of craft via external docking arrangements yields an unstreamlined result until they undock from one another.

If you want to retain streamlining, you have to make use of internal berthing (cargo bay or hangar bay) in order to "put one craft INTO the other" so that the host craft can make use of its hull streamlining.

Thus, you can "dock and tow" a sizeable external load ... unstreamlined ... but if you need to do an orbit to surface transfer through atmosphere, you're going to need to "drop and marshal" that external load into "chunks" which can be parked in orbit until they can be sequentially loaded internally and shuttled down inside the hull of a streamlined ship in relays. Bring on the High Guard condition context while running that shuttle relay until everything has been moved from orbit to surface (or vice-versa).

 

[Condottiere]

Towing is probably more a piloting check.

Hull and cable stress would be pretty much dependent on how the cable or the hull section/component is rated for mass/volume.

 

[mike wightman]

Get rid of hardpoints and go with surface area.

The ship building in FF&S does this, but if you want a more "user friendly" version then use GT ISW which also used surface area as a factor in determining hardpoints.

Here is an old thread where I discussed this idea:

Hardpoints and surface area

What if hardpoints and their associated weapons were limited by available surface area only? No need to worry about EPs and all that, can you fit them on your hull and in your hull? A bit like LBB2 really ;) I dug out FF&S and put this together: hull..hp 100 2 200 3...

www.travellerrpg.com

 

[Spinward Flow]

Towing is probably more a piloting check.

For an "unprepared" docking and towing, absolutely. If you're trying to tow something that your ship has never docked with and towed before, there's going to be all kinds of variables involved (center of mass displacement, maneuver acceleration torque dampening, etc.) for a pilot to deal with.

For "known, standard" docking and towing, such as containers that are designed for it and the specs for doing the towing are already determined and in the computer library, it'll be a MUCH EASIER task (since most of the work will have been done and tested ahead of time). Mostly a case of "follow the known procedures and you should be fine" kind of deal.