Ship Construction idea: Piggyback external Mounts

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PsiTraveller
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Ship Construction idea: Piggyback external Mounts

Postby PsiTraveller » Sat Oct 19, 2019 1:14 am

I am looking for input on an idea to increase cargo capacity.

If you had a Type 2 Docking Clamp (pg 43 Highguard) the clamp would cost 1 Million Credits and take up 5 tons. This would allow you to clamp ships from 31- 99 tons.

This got me to thinking of 2 different applications for the Docking Clamp.

1: What if you did not want to clamp onto a ship, but a means of carrying more cargo. If you built a cargo pod of 99 tons with a clamp connector and then stuffed the pod with 99 tons of cargo you could increase cargo by 99 tons, (-5 tons for the clamp volume on your hull, but still a more profitable operation.)
Pods of varying sizes could be built to move only the cargo you wanted to take. A 40, 50, 60 tons etc pod. This would allow you to select the pod needed and save the fuel on not moving an empty volume of pod. This would require a station to have the appropriate sized pods in stock. The cost of the pods could be a problem if you demanded hull metal pods, but using the same material as the cargo containers for external cargo mounts could reduce the cost. Or you use hull metal and the pods would last a long time.

2: What if you built a Clamp connection and then did not build a pod, but built a framework for external cargo mounts. You could still carry 99 tons of cargo, but your volume would not actually be increased to 99 tons unless you actually loaded 99 tons worth of containers onto your external cargo mounts. The clamp would be holding a flat framework of external cargo mounts that did not take up all that much volume. Once the external cargo mounts were loaded you would calculate the new volume and adjust Thrust and Jump numbers accordingly. Until they were loaded you would just lose the 5 tons of volume from your ship.

Version 2 would be more fuel effective if less than 99 tons of cargo was loaded since only the actual volume transferred would affect the fuel usage for the Jump.


Such a system would lose the 5 tons for the Clamp. (or more or less depending on what Type of docking clamp you used), but would allow more cargo to be carried when a ship needed to carry more.

Any thoughts on this idea?
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Re: Ship Construction idea: Piggyback external Mounts

Postby Linwood » Sat Oct 19, 2019 1:51 am

I’ve been assuming for a while that interplanetary (non-jump) freighters are built like Option 1 - dispersed structures with lots of docking clamps for cargo modules.
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Re: Ship Construction idea: Piggyback external Mounts

Postby PsiTraveller » Sat Oct 19, 2019 2:03 am

For a developed system with a highport I can see that. At some point I am guessing a streamlined orbit to ground delivery ship.

The volume only not weight of grav control makes it all about the cubage. For both shipping point to point in-system and through Jumpspace. Freight is all about moving as many paying tons as you can per Jump.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Sigtrygg » Sat Oct 19, 2019 7:52 am

It's not a new idea, see LASH traders in GURPS Traveller and the modular ships of the RCES in TNE for a couple of examples.
Back in CT days there was A GW supplement with some ships detailed - one of which is a merchant that carries cargo pods.
Moppy
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Re: Ship Construction idea: Piggyback external Mounts

Postby Moppy » Sat Oct 19, 2019 9:05 am

Many discussions before about how external cargo takes damage, and if it acts as armor. Realistically they should, but pragmatically they shouldn't since it would affect military ship design with specialised clip-on plates.

I've always thought open frame ships would make the best cargo carriers, but containers can be cheaper if you don't have to vacuum seal, pressurise and reinforce them. Several goods you don't want to carry unpressurised or exposed to the temperature extremes of space.

Maybe they will have some covered, and some uncovered spaces?

Today container ships have power connections for container refridgeration, and containers have their own refrideration system if they are designed to be used for that.
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Re: Ship Construction idea: Piggyback external Mounts

Postby AnotherDilbert » Sat Oct 19, 2019 10:17 am

PsiTraveller wrote: 1: What if you did not want to clamp onto a ship, but a means of carrying more cargo. If you built a cargo pod of 99 tons with a clamp connector and then stuffed the pod with 99 tons of cargo you could increase cargo by 99 tons, (-5 tons for the clamp volume on your hull, but still a more profitable operation.)
Agreed with previous posters, it can easily be done, but you haven't gained much. As you note you lose (at least) 5% cargo space compared to a normal ship. The fuel saving is quite small, the dominating cost is the mortgage on the drives.

You gain speeding up port turnover time and having a flexible jump range. Using the same jump frame for several routes should simplify logistics.

PsiTraveller wrote: 2: What if you built a Clamp connection and then did not build a pod, but built a framework for external cargo mounts.
External Cargo Mounts (HG p39) needs no clamp. Only actually carried cargo affects performance. Very profitable.


Either way the ship is unstreamlined and dependent on external cargo handling equipment, hence major starports.
Moppy
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Re: Ship Construction idea: Piggyback external Mounts

Postby Moppy » Sat Oct 19, 2019 11:56 am

I'm not really sure why space freighters can't jettison cargo into a stable orbit or known trajectory, and then fly off.

Cargo handling time to unload: near zero.
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Re: Ship Construction idea: Piggyback external Mounts

Postby phavoc » Sat Oct 19, 2019 3:11 pm

For the cargo to survive in space the containers would need to be built of the same hull materials as ships/small craft. That would vastly increase your sunk costs for containers. Containers today are relatively cheap, designed with the minimal materials and structural support. Dunno what the material cost would be, maybe 10% of the cost of a hull now?
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Re: Ship Construction idea: Piggyback external Mounts

Postby GamingGlen » Sat Oct 19, 2019 3:53 pm

I designed a 400 ton salvage/tow ship with Jump-3/Man-3 performances. It can haul a 200 ton ship (free/far traders) at drive-2 performances, and up to 800 ton ship at drive-1 performances. The operating plan is that it's subsidized by some mega-corp/financial institution to retrieve ships that are company-owned or mortgaged out and are so damaged they need a tow back to a yard for fixing. Due to lack of FTL comms, the salvage ship has a scheduled freighter run so HQ knows where it is at any given time to send the salvage orders. What it normally hauls is a 200 ton automated maneuver-1 cargo pod with a small bridge for a pilot if necessary. There are several cargo pods along the route so they can be loaded up prior to the ship reaching the system for quick turn around. On the salvage ship I also put in a larger medical bay and a young (read: cheap to hire) doctor is usually part of the crew in case there's stranded crew aboard the ship to be salvaged. I also put in four turrets in case they have to beat off someone trying to salvage the stranded ship. (ideas came from Archer 1999 animated show, including room for my version of a much improved light fighter :D)

As for hull, the weakened hull isn't enough as I think there should be something even lighter. I went with "weak" hull at 50% cost for the cargo pod, but haven't come up with what effects that has on combat (it wasn't going to matter for the campaign I just started). Apollo capsules' hulls were very thin but then they were made for one mission.
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Re: Ship Construction idea: Piggyback external Mounts

Postby phavoc » Sat Oct 19, 2019 6:24 pm

GamingGlen wrote:
Sat Oct 19, 2019 3:53 pm
As for hull, the weakened hull isn't enough as I think there should be something even lighter. I went with "weak" hull at 50% cost for the cargo pod, but haven't come up with what effects that has on combat (it wasn't going to matter for the campaign I just started). Apollo capsules' hulls were very thin but then they were made for one mission.
Yeah, book hull costs include a multitude of things beyond just a shell. 10% is probably too much as well.

The thing about Apollo capsules is that they just needed to survive re-entry (mostly heat). The ISS has to deal with external dangers that may hole it, but it also is very protected being in low orbit. It also doesn't travel through space at the speeds ships can reach. The Traveller hull has always been magically resistant to micrometeroid damage while travelling at high speeds.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Old School » Sat Oct 19, 2019 9:49 pm

phavoc wrote:
Sat Oct 19, 2019 6:24 pm
The Traveller hull has always been magically resistant to micrometeroid damage while travelling at high speeds.
This is true of all science fiction starships is it not? Excepting those that have magical navigation shields, of course.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Moppy » Sat Oct 19, 2019 10:41 pm

Some of today's probes have reached low Traveller speeds. They're protected by something called a Whipple shield. Unlike a Traveller hull this shield will deteriorate.

Giotto reached 245,000 km/h relative to its target, which is about 2 hours at 1-G, or potentially similar to jump point (100D) speeds.

https://en.wikipedia.org/wiki/Giotto_(spacecraft)

https://www.esa.int/Science_Exploration ... o_overview

https://www.esa.int/spaceinimages/Image ... ple_shield
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Re: Ship Construction idea: Piggyback external Mounts

Postby Condottiere » Sun Oct 20, 2019 6:05 am

1. Battle tenders.

2. Multiple clamps can cluster a larger container.

3. Optimum ratio is one to a hundred at twenty tonnes, or possibly infinity at fifty.
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Re: Ship Construction idea: Piggyback external Mounts

Postby PsiTraveller » Sun Oct 20, 2019 6:22 am

I was thinking along the same lines Condottiere, converting what the military use into an economic system. Hence my Jump Station TAS product (blatant plug!) that uses Drop tank technology to move more cargo along a defined route.

Using clamps allows cargo to be moved as needed, but allows fuel to be saved if there is no cargo. Interior cargo volume costs fuel to move. Exterior volume only costs if it exists. It costs no fuel if there is nothing there.

Fuel/Cargo tanks from the DSE book take up 5% extra space.

A type 1 clamp is 3.33 % space at 30 tons
type 2 is 5.05 at 99 tons volume
type 3 is 3% at 300 tons
Type 4 is 2% at 2000
and type 5 is infinite as you mentioned.

The cost of the clamps might be considered as a permanent loss to the ships volume, but does it have to be? Who is clamping whom?
What if the cargo pod had the clamp on it, built into the pod assembly or cargo mount framework. You would lose the storage value of the Docking clamp, but so what? The 99 ton cargo pod has a 5 ton Docking clamp built into it. This leaves 94 tons for cargo. A tender comes to the pod, connects power to the clamp assembly and tows the pod to the ship. The pod clamps onto the ship and the power and control connections are connected to the ship.

The ship now has 99 tons attached to it. Thrust and Jump could be recalculated based on the new tonnage. Once the journey is complete the pod is disconnected from the ship. A tender would then be needed to move it away.

Hmmm, I am going to think about that for a bit. Could save some tonnage there. More efficient than using modular hulls. No connection tonnage lost. Put everything on the pod to be moved. The core ship loses no tonnage.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Linwood » Sun Oct 20, 2019 11:33 am

I would expect that the designers would go with external mounts on the transporting vessel to keep modules as cheap as possible. An express cargo service seeking to minimize turnaround times might be willing to pay a bit more for modules, but I don’t know if clamps offer advantages over external mounts there.

Module construction should vary according to the cargo transported. Fragile might serve well for general cargo. Some bulk cargoes may be vacuum-resistant (although there are phenomena like vacuum welding to consider) so modules for those might be cheaper still. Conversely features like those found on railway hopper cars for quick bulk cargo unloading might add to the module cost.

Most general cargo would travel best with some level of atmosphere and heat, but it may not be at the level needed for passengers and crew so there may be savings there. Organics may need true climate control. Gravity control is an interesting one - some modules might not require grav plates at all, unless they’re considered essential for inertial dampening.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Moppy » Sun Oct 20, 2019 11:58 am

Not just heat but cooling. Temperature on the I.S.S. varies from about -150 to +120 C depending on “night” vs “day”. For modern space craft, cooling is more of a problem than heating.

Pressure would explode your milk cartons, too.

Stuff like sand could be carried unprotected.

Tthe Traveller high tech hull and life support are rather good.
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Re: Ship Construction idea: Piggyback external Mounts

Postby PsiTraveller » Sun Oct 20, 2019 3:29 pm

I agree that external cargo mounts are excellent. My only concern is how many tons you can create mounts for on a ship.

1st edition Scoundrel book has a couple of pages of cargo handling and external cargo mounts. Page 87 has a ship construction example of deciding between a 1200 ton ship or a 400 ton ship with 800 tons of external cargo mounts. So there is an example in 1st edition of a ship having a 2:1 ratio of hull to mounts.

The External Cargo Trader ship on page 97 of Scoundrel shows a 300 ton ship with 470 tons of external mounts. The external mounts even have a fuel tank attached, which is allowed to fuel a Jump. The ship is 50 MCr cheaper than a Heavy Freighter while carrying almost as much cargo. This would make a difference in profitability to the company carrying it. Saves a bunch of money on mortgage costs at the very least.

Now cargo mounts are vulnerable to combat. There is a table in Scoundrel that shows weapon damage to ships on page 87 as well.
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Re: Ship Construction idea: Piggyback external Mounts

Postby phavoc » Sun Oct 20, 2019 4:56 pm

Old School wrote:
Sat Oct 19, 2019 9:49 pm
phavoc wrote:
Sat Oct 19, 2019 6:24 pm
The Traveller hull has always been magically resistant to micrometeroid damage while travelling at high speeds.
This is true of all science fiction starships is it not? Excepting those that have magical navigation shields, of course.
Most Sci fi postulates shielding tech of some sort.

If people are looking for very fast turnarounds, then really ships would be nothing more than spines with control systems and drives that drop off cargo in system and pick up new ones. And your cargo / stations would be at the 100d limit to eliminate transit times.

Though I'd have to question if freight service is the pony express version, or something that's not so frenzied? Dwell times are the enemy of any merchant, since if you aren't moving cargo you are losing money.

But what we are proposing here is a frenzied movement of cargo that one would have to question is economical? We don't see the other costs, just the artificial construct of the game. In the 70s Sealand built 30knot container ships to race cargo across the Atlantic. They were financial losers because of the costs. 18kt ships operated with much lower costs and its quantity at 20kts that rules the waves today (even slower for bulk cargo and tankers).

Remember the Concorde? Efficient subsonic aircraft rule the sky today. Average speeds have actually decreased since the days of the707 because airlines want efficiency more than speed. And most passengers are fine with lower costs for lower speeds.

So I would assume that cargo in the future would be the same. Transported reasonably effeciently is the goal,not speed at all costs. Whether or not lash-style cargo would come back as the dominant method is best guess.

From a pure gaming perspective, keeping cargo moving in freighters and containers that have ships docking at stations and ground ports offers the most opportunity for RPG interactions. Unintended conflictions within the rules make for many board discussions, but head scratching elsewhere.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Moppy » Sun Oct 20, 2019 5:28 pm

phavoc wrote:
Sun Oct 20, 2019 4:56 pm
Old School wrote:
Sat Oct 19, 2019 9:49 pm
phavoc wrote:
Sat Oct 19, 2019 6:24 pm
The Traveller hull has always been magically resistant to micrometeroid damage while travelling at high speeds.
This is true of all science fiction starships is it not? Excepting those that have magical navigation shields, of course.
But what we are proposing here is a frenzied movement of cargo that one would have to question is economical? We don't see the other costs, just the artificial construct of the game. In the 70s Sealand built 30knot container ships to race cargo across the Atlantic. They were financial losers because of the costs. 18kt ships operated with much lower costs and its quantity at 20kts that rules the waves today (even slower for bulk cargo and tankers).

Remember the Concorde? Efficient subsonic aircraft rule the sky today. Average speeds have actually decreased since the days of the707 because airlines want efficiency more than speed. And most passengers are fine with lower costs for lower speeds.

So I would assume that cargo in the future would be the same. Transported reasonably effeciently is the goal,not speed at all costs. Whether or not lash-style cargo would come back as the dominant method is best guess.
Not 20. Container ships are down to 10-12 knots right now. Fuel costs. This means a new generation of ships with different engines. Container ships average 10 years olds for efficiency reasons, so the fleet is very modern.

However, ports are under great pressure to reduce turnaround times with ever faster loading and unloading.

Concorde's operator's economy was actually not that much worse than a regular plane (like x2 the cost or something). However the plane was narrow and uncomfortable, the passengers were charged a premium, and sonic booms made many routes unavailable.

I actually think passenger comfort was what killed it. You could have a suite in a 747 what you paid for a tiny seat in a concorde, the only real benefit of it being exciting because it was concorde. The time wasn't really a significant saving after all the airport hassle and the limited routes. Though back then airports were a lot less hassle than they are these days, though check-in time for first class (about 1/2 hr before takeoff) hasn't really changed much in most airports.
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Re: Ship Construction idea: Piggyback external Mounts

Postby Linwood » Mon Oct 21, 2019 8:46 am

Actually this makes sense. If the operating costs in transit are lower for a given voyage then the ship is more competitive. But time in port is different - you’re still paying the crew and the mortgage, but you’re also paying port fees and cost/hr for loading and unloading. Cargo modules should require less handling to transfer to and from the local (interplanetary) transport network, reducing costs there as well.

I would expect this to be very common in high-traffic areas where large/megafreighters on scheduled runs are the norm and volumes are high enough to justify purpose-built modules. Regions with less cargo traffic would likely use more flexible shipment methods.

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