I was taught that E=(+-)MC2. (This implies antimatter)

I'm disappointed he wasn't totally clear that all he was doing was adding kinetic energy to the base equation. Of course that adds energy to the system, but the base equation is about mass/energy (how much total energy a certain resting mass contains) not all energy. Heat the mass, you need another equation. Make it radioactive, another.

Also, maybe it's been proven wrong by now, but I recall experiments showing photons do have at least a pseudo mass, proven by their ability to move objects (like the spinning black and white squares inside a vacuum toy and theoretical solar sails).

I'm confused. They imply a 3 day trip to mars is possible, but is that at the maximum speed photonic propulsion can deliver, or do they include the acceleration and deceleration times? As I understood it, photonic propulsion can deliver extreme speeds, but only at a minimal acceleration. That means that maximum speed is much faster, but accelerating to that speed takes immensely longer, and the same goes for deceleration. Maybe they've invented a new method I've not heard of with much higher acceleration, but that's not really mentioned in the video.
They actually seem to imply they plan to use the same tech as cyclotrons, which means essentially a huge rail gun (and that's not photonic propulsion BTW, it's magnetic). Again, the amount of propulsion is miniscule, but the top speed is high with that method. Yes, you can expel matter at near speed of light, but only in tiny amounts and using huge amounts of energy.
Yes, it may take 10 minutes to achieve 30% the speed of light....with single molecules or atoms.
There are MANY reasons why we can't do this at macro sizes. Just look at the size of a cyclotron needed to accelerate an atom to those relativistic speeds. Now think about sizing that up to accelerate enough matter to move a spaceship instead of a single atom and it's likely near the size of the entire planet. We won't be building a cyclotron that size ever, nor will we likely ever shrink the accelerators to a size where they can fit inside a spaceship to shoot trillions of atoms out like a light speed gun. They are just too big and use too much power. Maybe once fusion is perfected and miniaturization also perfected it could work for interstellar travel, but never for local space travel, the acceleration levels are just too small.
Also, it seems solar sails give the same or better acceleration to the same top speeds without the impossible technology....but they don't work too well for stopping except at other stars.

I'd like to see how they stop once they got to the star. Simply turning the sail around would not be enough. A combination of solar sail and ion propulsion (ion not in the acceleration phase, but for the deceleration phase). It is unclear whether the flight time is direct at maximum speed the entire way.

~3200+ years though. That is a LONG time. If we can someday get the travel time down to decades or even a century, there may be potential for a mission. Send it off. Get it into orbit.. and have it send back data. Of course, the thing would need to be completely automated. AND we'd need to have someone back at Earth with an ear to the sky, waiting for a signal.

I wonder how practical sending data such a distance would be. The energy required. You'd need one heck of a powerful transmitter.

I suspect technology would improve in time (especially 3200 years) that would obsolete the mission to begin with. Imagine sending such a ship... to have a faster one PASS it on the way to the star 1000 years later.

Very cool. As close to free propulsion as you can get. I always feel a twinge of sadness when I realize I probably will not see colonization in my lifetime. Then again, maybe that sadness is just the Phillip Glass score in the background. The one serious issue concerning solar sails are tears due to micro-meteorites and other space trash. I heard that they are thinking about self healing sails but that is all I've heard.