Hi Kurt,

IMTU containers are just standard containers; they are 3x3x6m or 3x3x12m (4 ton or 8 ton) boxes made of iron/steel and/or crystaliron. I've likely posted them to the list before.

I've done standard ones and open toped ones and open framed ones, refrigerated ones with diesel generators (the generator being a separate add on), solar powered refrigerated ones, refrigerated ones with fusion generators (@TL6 and TL10 (with TL8 for the solar powered ones))

These are mostly completely disposable (the refrigerated ones less so) ish; they come in at Cr 1,745 each or Cr 1,919 for the crystaliron ones

You put these on a boat (or ship) and you unload them onto a lorry (truck) with a flatbed trailer or train with flatbed carriages with fittings to secure them and then you freight them to where they need to go.

Trying to make the standard containers have their own batteries is not an issues (that's how the refrigerated ones power the basic life support (cooling)), making them have grav units that can counteract their mass and the cargo is another matter entirely especially if you use the MT design system (MT being my ruleset of choice).

So that's where the grav trailers come in. They are the flatbed trailer with the fittings for the standard containers to sit on, and as you can see they are quite expensive so if you want to freight your containers by grav vehicle it needs to be cost effective (where the high value, time sensitive cargos come it), and which is why I did an unpowered trailer as well in order to cut the cost of the trailer.

I expected, but haven't worked out, that it would be cheaper to create a grav vehicle with excess power to pull multiple trailers than it would to provide power and fuel for each individual trailer however that would negate Jeff's suggestion of the trailers tracking the vehicle pulling them because they are effectively dumb although I could look at putting a computer 0 back in an unpowered one (at an additional Cr60,000) to see where that leaves us. Also there's the issue of duration. A vehicle with excess power is likely to have a greater duration than you can individually put in a trailer, and as it's the vehicle's duration you don’t need to worry about each individual trailer's duration (although the computer would tell you what it was).

Basically what it comes down to is the containers themselves aren't the issue it's the grav units that offset their weight/mass and the weight/mass of the cargo they contain that is the issue.

Firstly you need to define the amount of weight/mass of cargo you can put in a container; so I got this from the standard allowed vehicle weight rules of the UK (I looked at the US rules, but hay I'm British ... and it turns out the UK allows more weight)

Then you need to work how you use grav units and inertial compensators and a power source to be able to move them, and it made more sense to me to make the trailer and/or the vehicle to do this as opposed to put them in the containers themselves.

The main considerations are weight and cost. The more it weights the more grav units you need the more power you need power plant you need to put in to achieve what you want.

I played around with different power sources quite a lot to see if others were better, but nothing fits at this type of scale and TL better than fuel cells, and I was looking for a 72 hour duration, but didn't quite have enough space in 1 ton to achieve it. I could have made them 1.05 tons or some such, but I though that was just a little churlish so sacrificed 4 hours of fuel.

Adding or removing the sensors makes little difference it's the fuel cells and their fuel (i.e. the power supply) that is the biggest headache. Now as you go up the TL's your power supply will get better, but the grav units won’t change much. You're TL12 ones weight the same (ish) much and don’t take much power but cost an absolute fortune as do fusion plants to power them.

So from an MT design point of view a container with 5 minutes of battery with enough grav units to move 29 tons (including the weight of the container and the internal grav units) isn’t going to be pretty; although it might be fun to see what/how it turns out ...

Best regards,

Ewan
--
For the fallen in the cause of the free:
 "When I go home I will tell of them and say,
 For our tomorrow, They gave their today."

 My spelling is entirerly due to dyslexia, typos, and poetic license

-----Original Message-----
From: xxxxxx@simplelists.com <xxxxxx@simplelists.com>
Sent: 02 June 2026 14:37
To: xxxxxx@simplelists.com
Subject: Re: [TML] Grav Trailers

On 6/1/26 3:13 PM, Jeff Zeitlin - editor at freelancetraveller.com (via tml list) wrote:
> Yes, but 5 minutes isn't going to get you from Paulo Down (southwest
> US) to the Manhattan district of the East Coast megacity, and even if
> you use local grav freighters to get from Paulo to JFK, you've still
> got to get from JFK to the final destination...
>
> Which brings up a potentially interesting question, both for EDQ's
> grav trailers, and for present-day wheeled trailers, especially for
> road trains in .au: Is there any sort of mechanism so that the
> trailers "track" the path of the "tractor"?  I know in the US, there
> isn't (universally, as far as I can tell), so that the driver of a
> single cab+trailer has to swing wide to make sharp turns (like when
> delivering to retail establishments in urban/suburban areas), and
> tandems (2 trailers) or triplexes (3 trailers) are prohibited in areas
> off most interstate-grade highways - but in a lot of SF, the trailers
> *do* track, so that the entire "train" acts like it's on rails. (For
> an example of such a "tracking" train, see _Wheelworld_ by Harry
> Harrison.)

IMO, I would think (dangerous for me) that just like we've standardized container types and sizes today, that the same would be done in Traveller.  The limited battery idea makes perfect sense, but I'd go one step past that and eliminate them entirely.  The "mover" (perhaps an air/raft frame with just a connection frame and controls for one) would connect and directly power the container. Containers should be cheap, viewed as disposable, and cheap.  A lot of containers today last one, maybe two uses before they're sold/scrapped.  As for a control module to make them track like a train, that could probably be done by something akin to a Raspberry Pi (that also draws power from the prime mover).

A further argument could be made that the container itself would not be anything more than a container and that like today, the hardware to move it any distance would be connected to the container at the port much like a semi frame for an ISO container or a flatbed rail car.

Again, the idea is sound, just too expensive.  How much would it add to the dton cost/parsec?  What is the container's lifespan?  How durable is it?

--
Kurt Feltenberger
xxxxxx@thepaw.org/xxxxxx@yahoo.com
“Before today, I was scared to live, after today, I'm scared I'm not living enough." - Me

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