[Space] Gliese 581

[strange7person]

Let's say Earth has late TL 10 orbital economic activity in the $10^12 per month range, with limited superscience, vast reserves of antimatter which need to be disposed of in some appropriately symbolic way as part of disarmament in the aftermath of a cold war, a similar surplus of frightfully competent people who find themselves unable to adapt to peacetime, and public sentiment backing the idea that humanity faces certain existential risks so long as it's confined to a single star system. So, there's a push to colonize Gliese 518, even if doing so makes little or no sense economically.

Here's the initial concept for the colony ship (or rather, one of the human-habitable ships sent out as part of a larger colony project):
front hull: [1] nanocomposite armor,
[2!] reconfigurable system: ramscoop/magsail,
[3] reconfigurable system": open space/science array/solar panels,
[4-6] hangar bays,
[core] control room
center hull: [1] nanocomposite armor,
[2] de-rated fusion reactor,
[3-6 habitats (500 cabins, 10 establishments, 100 automed sickbays, 100 Science! labs 400 tons steerage cargo),
[core!] robofac,
rear hull: [1] nanocomposite armor,
[2-5 fuel tanks (3000 tons antimatter-boosted hydrogen),
[6] reconfigurable system: antimatter plasma rocket/fusion torch
features: unstreamlined, lacks automation

All the reconfigurable systems are TL 11 prototypes, but even with all those multipliers the actual hull & machinery of the ship cost less than half as much as the antimatter fuel. Science array and solar panel both attempt to catch infalling photons and convert them to electricity; the former takes measurements, while the latter simply channels the power. The same equipment transforms into an open space for farming and claustrophobia relief by delaminating and inflating various membranes.
The engines both mostly take individual high-energy particles in one end and spit hydrogen plasma out the other.
The magsail and ramscoop are both mostly enormous superconducting hoops.

mission profile: Load up with five hundred to a thousand troublesome young heroes and disgruntled veterans, hundreds of tons of personal belongings and lifebanks, and load the hangar bay full of whatever pre-packaged parts seem likely to come in handy. 17000 hours accelerating with the magsail to just under Sol escape velocity.
6552 hours accelerating with antimatter plasma rocket to 1815 mps.
? hours ramscoop-fed fusion torch up to relativistic speed and back down.
81900 hours decelerating from minimum ramscoop velocity to orbital insertion.
Overall travel time depends on how close to C you're willing to push. No less than 35 years, likely 60 or more if front armor ablation is a concern. In any case, all the antimatter is expended before relativistic velocities are attained, as a safety measure.

Please poke holes in this plan.