Establishing a colony at TL8

[acrosome]

If I were planning this operation one thing I'd worry about is reliable power. Solar cells have a short lifetime- the best ones last maybe 30 years at a decent efficiency. They'd work in the short term but windmills or micro-hydro are better options and much easier to maintain with simple (low-TL) tools. Micro-hydro is more reliable than wind and any easily human-habitable world will have flowing water. It also doesn't really need a dam or anything, just a decently-sized waterfall and some pipe, so it could be up and running quick. A few hobby steam-engines would provide power as long as you can find something that burns.

With enough power a lot is possible. You won't be replacing broken computer chips anytime soon but just powering the electronic gizmos for a few decades would make a big difference. Include a number of simple electric motors for the colonists to use to improvise to meet unanticipated needs. With strong magnets and copper wire you can build your own electric motors.

If the gate is big enough I'd be driving trucks full of grain and dried legumes and petroleum through it into a marshaling yard and just parking them. There are actually specialized trucks for this that could load vast quantities at the nearest grain elevator or refinery. It's the End Of The World- no need to hold back. Even if you never use the trucks again they are a source of refined metal. Given your time constraints you would need to figure out how fast trucks can be transshipped through the gate. Also, tractors, combines, etc. The petroleum is to fuel the farm machinery for the first couple of years to get you on your feet and build a surplus and allow time for your livestock to breed until you can have horse- or ox-drawn plows, harvesters, etc. Throw in a couple of old plows and other horse-drawn farm equipment requisitioned from museums as examples.

Instead of semitrailers use flatbeds with conexes for other supplies. You can probably just pick up conexes already loaded with useful stuff at any port or railyard, and once empty the conexes have hundreds of uses- primarily as housing but they can also be used to place a wall around your compound. Include a couple of truck-mounted cranes or forklifts to move them around. A few welded shut and bolted together would be a barge. Heck, the US military has a widget called a CHU- Containerized Housing Unit (pronounced "chew"). It is basically a conex with a normal door on it instead of the large cargo doors, maybe a window or two, an AC/Heater, and pre-wired for power. Throw in bunk beds and it is housing for four soldiers or two humans. :) Containers come in different sizes and are stackable- just have a carpenter build stairs and decks or balconies for the higher levels. There are also office CHUs (stacked into office buildings), latrine CHUs, shower CHUs, etc. And they are already in stock and available to be driven through your stargate. Or just raid the nearest mobile home dealer and drive THOSE through the gate. Maybe a few RVs, too (heck, they are self-propelled and thus easy to get through the gate even if they never move again, and the engines are salvageable for metal).

With a metal lathe you can make almost any other machine tool. A well-built electric motor will last almost forever, but you could also send belt-driven machines and run them off a primitive waterwheel. So, machine tools, definitely, and stocks of industrial metals (no one will be smelting aluminum anytime soon). Brass in particular comes to mind, for drawing cartridge cases and because it is easy to machine to whatever random little fittings you need- that's why navy ships still stock a lot of brass. Some specialty steels, too, especially stainless alloys. Iron stocks needn't be large, though. Iron is very common in the universe, plus you have the trucks to mine.

Since the operation is a rush I might just drive in a few truckloads of printers, toner, and paper and send a few copies of the Library of Congress on DVD-ROM. Then the colonists could look up and print what they need on the fly as long as the computers and printing supplies hold out. That would get them through a decade or two at least and minimize the likelihood that the planners forgot to include a vital manual. This would also handily include OLD books about farming in the 1800s using draft and other useful "primitive" information, like primitive medical care. I once looked through some fascinating medical textbooks from the 1920s that included a LOT of old-school methods that I would never think of. You could include patent office files, too, for the designs of the machines. For that matter the US Military publishes all their manuals as CD-ROM collections. Certainly a few truckloads of obvious books could be included- survival manual, medical texts, everything know about the invaders, etc. Books on metallurgy, refining, agriculture (any agricultural college could have it's library looted to produce a great collection), engineering (especially civil and chemical), gunsmithing, machining, guerrilla warfare. Oh, and basic textbooks for the children and children to come!

I'd include a stock of flintlocks and books about making gunpowder, just in case TL falls farther than anticipated. A few compound bows and crossbows, too, to allow hunting with the primitive weapons to reserve the modern ammo for the fight against the aliens or other more serious threats (including internal rebellion?). It's easier to make arrows than cartridge casings. Also, a decent bolt-action rifle will function until you wear the rifling out of the barrel, whereas many modern gee-wiz combat rifles require routine arsenal-level maintenance. Also, as a general rule the barrels for larger and slower rounds last longer than those for smaller and faster rounds- i.e. .308 barrels have a longer life than .223 barrels, and pistol barrels can last a very long time so submachine guns might be popular, and perhaps Winchester rifles firing pistol cartridges would be included as utility rifles. The .22LR is so slow that those barrels last a long time, too.

A decent supply of clothing (from military uniform stocks or the nearby outdoor stores) would also be nice so that for at least the first few years valuable labor isn't being consuming making it when it could be better used making food. But throw a few looms in, too, for the future.

Stills. If the local vegetation is edible then you can brew alcohol from it, and that's fuel for vehicles or stoves or lamps even if the world has no petroleum. It is also an important industrial chemical, and a medical antiseptic. And recreational drug...

Personally, I think it would be pretty straightforward to include among the colonists a bunch of military members and their families. There are significant numbers of families living in on-post housing on almost any military base. If the aliens really trounced us then the only military members available in great numbers might be rear-echelon types rather than the combat guys (who are all dead). But at least they would have the discipline needed to get the colony started. There is always the danger of degenerating into despotism if there is a charismatic senior military guy around, though. On the other hand- in the US military at least- there might certainly be some soldiers who would resist that VIOLENTLY.

So, I think I'd include a constitution of some sort. If the Earth is truly getting fully taken over I'd include whatever was left of the government among the colonists and call it a government-in-exile, even if it's just a few federal judges, a couple of congressmen, and the Secretary of Labor is now president- then you just include the U.S. Constitution and let it be known that it stands as the law of the land. (It worked for an agrarian society with an isolationist government once before, after all!) By retaining that legitimacy and legal framework you might stand a better chance of preserving civilian control of the military, especially since a high proportion of the scientists/academicians/doctors (even military ones!) that you include will be liberal in outlook.

Speaking of which, where can one find a decent supply of scientists/academicians/etc. on short notice? The nearest community college? Heck, herding the student body out of their dorms would provide a great gender-equal, young (breeding age), healthy stock of bright, motivated people who know how to learn. They would also make ready troublemakers- always questioning authority, petitioning the government-in-exile, etc. And they'd also have a liberal majority to counterbalance the military element.

The U.S. military has pre-stocked kits for medical units- these are called Medical Equipment Sets (MES sets). Including one for a Forward Surgical Team, one for a Battalion Aid Station, one for an Area Support Medical Company, and maybe a few others would be a ready-made way to include a decent medical capability, and the MES includes drugs though usually only a small supply. If the operation was big enough an entire Combat Support Hospital or Fleet Hospital can be loaded on trucks, too- that could be hundreds of beds!

A couple of books by S.M Stirling come to mind. "Conquistador" involves the building of a technological society on the other side of a gate as part of the back story and mentions the problem of "how fast can you cram stuff through the gate?". The Nantucket Trilogy involves the island of Nantucket thrown back to 1250BC and improvising along.