Apr 13, 2016 03:20 Dan Ward Posted on: Breakthrough Initiatives

Here's a very uninformed question/suggestion: if the sail is a reflective material, doesn't the incident light produce a sidewards pressure component on an angled surface? In effect, can't a mirrored sail be used to 'tack' within the laser beam? No need then for thrusters.
Unless the thrusters are to re-angle and stabilize the sail. In that case, why not use voltage-controlled shuttered sections (varied opacity with LCD-type material) along the sail's edges. Assuming the sail is spun to maintain it's shape, those shutters would be timed to precess and stabilize the whole craft to the desired angle. That would draw a lot less current than diode lasers.

Apr 13, 2016 13:49 lolix3345@gmail.com Posted on: Breakthrough Initiatives

Do you always speak about solar sail ? Would they say 'solar sail' and no 'photon thrusters' ?

Apr 13, 2016 15:21 John McLean Posted on: Breakthrough Initiatives

Dan - you can't "tack" in the sense sailors use, i.e. to travel upwind (towards the light source in this case). But yes you can introduce a component of accelerative force perpendicular to the beam, i.e. adjust course

Apr 14, 2016 15:42 Michael Atkinson Posted on: Breakthrough Initiatives

How about altering the charge on the spacecraft and using interaction with interstellar magnetic fields and target star magnetic fields to alter the trajectory?

Apr 14, 2016 22:05 Tiago Medeiros Posted on: Breakthrough Initiatives

Dan, I imagine that once there you will need to slow down, and perform maneuvers of navigations for flyby, I think it would be the function of thrusters.

Apr 14, 2016 23:20 Tom Bonofiglio Posted on: Breakthrough Initiatives

Actually, I imagine at this point they are not concerned with slowing down. Just fly by, observe, and send data back.

Apr 16, 2016 23:03 Ioannis Xydous Posted on: Breakthrough Initiatives

As Tom Bonofiglio writes "Actually, I imagine at this point they are not concerned with slowing down. Just fly by, observe, and send data back.".
In other words, it is one-way ticket. Two fundamental technical problems cannot be overcome by the Light Sail-Nanocraft concept:
a) It cannot carry its own thrust engine. Weight versus Energy and vice versa issues.
b) It is impossible to execute direction corrections especially when the Nanocraft travels at 0.2 c as also there will be no thrust engine to make such corrections.

I would suggest in place of attempting to solve all these technical challenges (it is a huge waste of time just to flyby and take some photos) for the next 20 years, just focus on the core issues, namely New Propulsion and Energy Methods. I predict within the next 10 years the idea of a Light Sail or even a Solar Sail will be discarded as primitive and impractical for real applications.
The Star Shot Project mentions the following inaccuracy: “No ‘dealbreakers’ have been identified by the team of expert scientists and engineers leading the program.”. Why is it an inaccuracy? Because we have place our faith on what is already established by ignoring alternatives.
What I suggest? I suggest something although improbable is not impossible. I speak about finding a solution about the two core issues. Precondition: It is required to prove experimentally a new claim that leads to the solution. This claim requires of conducting an experiment that may prove the deviation from the expected relativistic electrostatic deflection or on another where a red shift may occur with increased opposed power density (Michelson Interferometer). Any serious laboratory can do this. Then, you need to have the courage to read where all these lead.
Ioannis Xydous
Web Site: https://www.ioannisxydous.net.gr/
Paper: https://vixra.org/abs/1604.0039

Apr 17, 2016 04:46 Karen Pease Posted on: Breakthrough Initiatives

"(it is a huge waste of time just to flyby and take some photos) "

Then almost all of what NASA has done throughout its history is meaningless - going places, gathering data, etc (and - very rarely - taking samples back to Earth for more data-gathering). Getting spatially-varied spectral data and precise physical / orbital parameters - plus data such as the density of the interstellar medium, the stellar neighborhood of the other star, etc - is not only important to learning about our universe (we don't exactly have a large sample size of earthlike bodies to study in our own solar system). It's critical if we ever want to launch a larger mission to other stars. You don't just take off and go somewhere with humans without knowing *precisely* what they're getting into.

Part of the point of these craft, additionally, is that once you develop the hardware, they're very cheap to launch. Each craft should be very cheap, even if the materials are extremely expensive per unit mass, because they're so small - and the energy requirements for the launch are only in the 5-6 figure $USD range per craft. So you can send whole fleets of them out.

And while you're developing the whole project and not yet achieving the design speeds, the same advantages apply to exploring our solar system. There's a tremendous amount to explore that we've never seen, but it's hard to get 9 figures per celestial body for exploration.

Apr 17, 2016 05:55 darrell sellers Posted on: Breakthrough Initiatives

what about parts effects under radiation effects ?
TID, SEU ?

Apr 17, 2016 11:08 Ioannis Xydous Posted on: Breakthrough Initiatives

Karen you "You don't just take off and go somewhere with humans without knowing *precisely* what they're getting into.".

Actually they already know from the Moon Missions. The problem is named "Cosmic Deadly Radiation" and addresses humans. How we cope with that?

I mean in case of Human Missions what will happen when a burst of Cosmic Radiation crosses their path. In place of "Deadly" use "Extreme Power Density of gamma-rays". In that case besides that all electronics will be damaged, humans would be already dead and "baked" on the way to Alpha Centauri.

Our technology cannot do anything about it (only a limited shielding through absorbing material is today possible) using conventional Quantum Physics and technology, they will never solve the problem. It is not a matter of material Science it is a matter of used Science.

Karen you wrote "And while you're developing the whole project and not yet achieving the design speeds, the same advantages apply to exploring our solar system. "

Great! Then what? Do you have the means to go and land on Pluto or even Mars. Just the Moon Missions showed us what are the major problems we face for Space or Interstellar Travel.