What would a ship with a 100 thousand tonne budged that needs to carry cryo-frozen cargo through 20 lightyears of interstellar space at 0.35C coasting velocity, using laser sails at both ends of the voyage, and putting the safety of the cargo above all else. (See "The Problem... Mk-2?" and "Edits")
Side-note, I absolutely love this format. Let's say we use that big tractor ship I ought to make another post to check the math on, which can reach 0.7C. Let's call her the ISV Not So Venture Star. It's like it, but bigger. A lot bigger. And it carries a small team of colonists and the required materials for colonizing a star system.
The 3D printers at their disposal cant make advanced microprocessors, sensors and other advanced machines, but they can print out the bulk of drones, vehicles and such, bringing the important bits from earth. They will stay in cryostasis for most of the voyage, a form of hibernation that slows metabolism to almost stopping, letting them sleep for decades.
With the equipment they have, they build a dyson swarm- Well no. That isnt the right word. Dyson swarm evokes the idea of an advanced civilisation. This isnt even close. It's just a bunch of orbital solar panels and mirrors in a nice, even ring around the sun-like star.
But theres a problem, they have a machine powered by suspension of disbelief, called a phase-gate. It works by some magical phenomena we have yet to discover and creates a region of spacetime that are linked. Go into one kilometer-wide door, come out of the other.
For some reason, it runs on a flow of virtual particles which are directed by mass-energy, which in turn is held in suspension by some kind of magnet-like system, never discussed in the book. The point is that it needs a lot of cooling, and energy. Like a lot of energy. And it's extremely advanced, thus needing to be imported. But it's huge.
How do we move this honking huge machine from earth, while being strangled to a wall by the tyranny of the rocket equation? We alleviated this with massive petawatt-power lasers to accelerate our ship, but we need to decelerate on our own when we arrive, which is a hairs-width from impossible, even when we use the most absurdly, stupidly dangerous fuel we possibly can. Anti-matter.
Simple! We don't move them at the same time! Who said we need to ship the colonists and all the frozen cryo-samples of earth-life on the same ship? We can ship it on a bigger, much slower cargo ship, lets say at half-speed. Sure, it will be hammered by radiation and we can't ship people because they couldn't survive cryostasis and cosmic rays for that long, but a bunch of frozen seeds and eggs definitely won't care as much.
But then we'ed still need engines to slow down... right? WRONG! If we got the ship up to moving at 0.35C with a massive laser-sail array powered by solar collectors around the sun, then we can do the same thing around the colony star, which we can call Ilus.
The new flight plan would be as follows. Launch the slow ship, Aurea, using the laser batteries. Then collect antimatter for the next 2 decades. Then launch the fast ship, Theia, on route to Ilus. After 3 decades transit, the Theia arrives at Ilus and starts a (not really) dyson swarm. After a decade, the Aurea opens its sail and prepares to end its 6 decade journey.
The small crew awaken in Trenton city and launch center, just to discover that they have 2 weeks left to fix a cascade of failures that have gotten progressively worse over their 9 years in cryosleep, waiting for the autonomous systems to finish building the dyson swarm, and with the one controller that was supposed to stand guard for their 6 month shift having vanished without a trace.
And they have to repair and engage the laser, lest the Aurea and their ticket back to earth dash past at over 100,000 kilometers per second. Fantastic drama setting, like The Martian but theres an entire crew and a planet to work with, and at stake.
The Problem... Mk-2?
This is fantastic and all, but what would the Aurea even look like? Since it would be moving slower, it would need a much less extreme shield, possibly a hybrid ablative-whipple type, directly mounted to the bow of the ship.
It would need cryogenic systems, which would make heat, and thus need large radiators. It would also need fusion reactors to power it, and thus fuel for it. It would need a small main hall-effect engine to keep at cruise speed, and some maneuvering engines and an onboard AI, and thus computers.
The phase-gate ring would be disassembled into 6 sections and folded into the core of the ship, with a rigid truss from the shield to the reactor at the rear, fuel tanks behind the reactor and cargo modules ahead of the phase-gate. Along the entire length would be radiator panels which could double as Whipple shields around the phase-gate.
What would be the best configuration for such a ship? (and is there any other considerations I need to make?)
This isn't strictly part of the question, but I want to say it. Thank you Sphennings, and you're getting me to drop the need for a scientific explanation, which would wreck any illusion of suspension-of-disbelief. To Starfish and Nosajimiki for their over-the-top math, and to BMF and many, many others for working out the technical details.
Thank you everyone! Im writing and working on my book every day, and this is special because I am only just starting the book, and I know what the book is about, but I'm not locked in yet, so I can change and add the things that you guys worked out. >(^-^)<
Edits and Tech Specs
For future reference, the distance it will cross is around 20 light-years, give or take a few. The phase-gate unit is a 0.7km-wide ring, split into 6 even sections and totaling in at 3k tonnes. It also has a power ballast that slowly accumulates energy and releases it quickly, weighing around 2k tonnes in shipping containers of machinery.
The weight budget of the starship is around 70k to 100k tonnes. The safety of the gate is the most important part of the mission, and the cryo-cargo is just a side-note.
The ship needs to have some mechanism to expose a reflector shield at the front and rear of the ship during the laser-sail driven phases, and hide them away to to minimize risk of being damaged. The ship should be resilient as possible and carry as much and the most efficient shielding it can.
The phase-gate will need a few months to upwards of a year be set up and the power system will also need time to charge and fire, after which more materials can be shipped in from earth, in the case that the cryo-cargo is damaged or lost. A loss nonetheless but not a big one, compared to loosing the phase-gate.
The ship should be designed to be as safe and redundant as possible. Thus, maneuvering engines and a backup main engine would be best, as the ship might need to do slingshots around planets and the star to loose speed.
There is almost 7 decades of work and preparation all hinging on this one ship, so it should be built like it.