COOL! I'm having a very hard time understanding exactly what it does. The other scary thing is that it only made 35uN of thrust from 'off the shelf components.' I wonder what kind of power it took to make that thrust? Propulsion is nice, but if it isn't efficient, it isn't useful. The satellite aspect is intriguing though. Satellites that don't have an effective life 'limit' because of fuel running out.
I too am interested in it's efficiency.
The main downside is that the efficiency (not power input) is achieved by bouncing the beam many, many times between the laser bearing spacecraft (or base station) and mirrors many many times allowing the photons in the laser to be "reused" over and over for momentum transfer.
This will be AWSOME for ultra precise station keeping for interferometry observatory satellite formations, probably allowing for the eventual resolving of earth-like/earth sized worlds around other stars.
While technically possible, using this to drive a probe within a week to Mars is a much more daunting task engineering wise. Although there would be no problem with the G-forces on the crew. The thrust from such a photon drive would be miniscule. The crew would be unable to detect the acceleration with thier bodies, and it would seem indistinguishable from microgravity.
However, the miniscule thrust would be constant, and would build up over time, every second of every minute, every minute of every day for the duration of the mission, at least until they reached "turnaround" and would need to start breaking for insertion into Mars orbit.
Think of it this way, what if you had a car that could only accellerate (and brake) at one mile per hour, per hour? That would suck. But what if you had to go a million miles? On that trip I'd much rather have that car than one that could go from 0-60 in 3 seconds, but only had a maximum speed of 200mph.
Besides consumables, food, water oxygen, or the weight penalties of closed-loop recycling sytems and gardens etc. the main advantage of rapid transit times is radiation. The shorter the trip, the shorter the time the crew is exposed to solar radiation, the possibility of solar flares, and cosmic ray activity. You can configure the ship in interesting ways to add shielding by using propellant tanks, water tanks, or moon rock for shielding, but all also have considerable weight (more appropriately mass) penalties, and if consumable tanks are used as double duty radiation barriers, the protection factor obviously decreases as the consumables are, well consumed.
