This subject was covered recently on the science channel. The end consensus was that the only thing holding it all back is feasibility. The amount invested into such a project will never have a return for those investing. Of course, there will be some technology researched and developed in the process that will benefit in some way, but the end product is a one way trip measured over the course of one lifetime.
As to the craft design. It will have to be highly compartmentalized , interconnected at several points and large enough to sustain several groups of people. It will have to be designed to either spin as a whole craft or have special areas that spin to help prevent what medical condition occur due to zero G. I suggest the entire craft. less moving parts.
It will have to have any and all gear needed to mine, refine and create materials from interstellar objects such as asteroids.

I knew what I was about to read in detail just from reading the title. It's creative accounting. If they can't have a real plan within the next two weeks, I'm calling fake on this one. And even though I like the idea, I disagree with tax payer's money getting involved. I'm that stupid and DARPA knows this. Even they must be trolled once in a while.

We are hundreds of years out from doing this. Maybe one day if we stop killing each other every country will help in this project. Until then it is just talk.

Perhaps the best thing to so would be to snag a small asteroid, excavate chambers and corridors inside it, fit it with all the mechanisms and life support that any other spacecraft would require, then send it on its way. Aesthetics should be the least of our concerns.

We'll have to get to work on a space elevator before we could possibly build an interstellar ship, but I believe both are entirely doable!

This opens the door to thinking outside the "sphere." Who knows what we might find between the stars within the next 100 years. Perhaps we will develop the technology to create a space station in the Oort Cloud and that will be the next step; to go there and build it. Perhaps we will discover something between our solar system and another that will be the next step after that. The point is, we've started. We've created a dream, a vision.

It does not sound like DARPAs Mandate but it is better than blowing the money paying people to be poor and there is the spin off technology. ...........................................................................................................
re; Pat Burneson
Constant acceleration could provide "gravity" for the crew as well but I suspect that the trusts will be too low for that. ............................................................................................................
re; Nitrozzy Seven
Did you even read the article? It is not until the middle of September until their first screwy idea symposium. Assuming an earth type destination and a star ship with less than one G acceleration. what kind of landers do you use? Do you hope to find a dry lake bed like Rogers Lake at Edwards AFB or maybe a frozen lake instead for landers like the space shuttle? Or perhaps shuttles designed to land on water? Ballistic with parachutes and hope you can gather everybody back together? Have the star ship turn into an orbital tower? Blimps?

I suggest a colaborative site be set up so as to receive info and help from all over the world to solve all issues that arrise.
From grown ups to school kids, all should be able to contribute to resolve issues.
Such as that collaborative site where people fold atomic structures to come up with inovative strands of chemicals that help cure diseases and so on.
So for example - say we need a formula to work out some kind of physics problem, like teletransportation or something. The site can have all the currently available stuff on there and in various formats, either written down or in graphic format. This way anyone on earth can work to solve snags.
The same could work for all other issues.
Usually things get discovered where you least expect and genius isn't taught in school.
Some people have incredible spatial capabilities and are able to picture solutions to problems without knowing how they did it. So if a problem were to be shown in some kind of spatial form just like in that atom folding site I am almost sure all things can be solved.

A space elevator is not that practical actually. It's not a matter of engineering. It is just a really BIG target for some nut bag to blow up. And should that happen, think about the outcome. The cable alone would be made of diamond and wrap 3-4 times around the world. That'll make the dinosaur killing asteroid look like a peble in a pond. A sling shot or rail gun makes more sense. As for this, no direct return on investment, but in developing the tech, we start mining the asteroids and reaping unknown benifits. Absolutely go for it.

The picture of interstellar space that is slowly emerging definitely works in our favor for interstellar travel. That is, interstellar space may have many planet-sized objects in it.
That could make interstellar travel a series of manageable hops, rather than a single very long voyage.
Once you are at the outer edge of the solar system, you might already be halfway to the next stopping point.