Another aspect of the project's challenge is funding. While technically plausible in principle to develop such system, the total funding needed is on the order of $5-10 Billion. There is a relevant discussion about this on [Metaculus](http://www.metaculus.com/questions/208/to-the-stars-1-will-t...), for those who are interested.

There is actually a "Beam Propulsion Series" on Metaculus(http://www.metaculus.com/questions/#/search/series--beam-pro...) addressing relevant questions about the Starshot Project.

Charlie Stross wrote recently about the threat of beta radiation to these small probes[1]. This isn't discussed at all in this article or the associated paper[2] which focuses on purely mechanical collision effects. Anyone know if this is a separate consideration for another research group?

[1] http://www.antipope.org/charlie/blog-static/2016/08/san-trom...

[2] http://arxiv.org/pdf/1608.05284v1.pdf

Alpha, not beta (beta radiation is just electrons):

> Roughly 1% of the ISM consists of helium atoms, and we have a technical term for an ionized helium nucleus travelling at roughly 2% of the speed of light—6000km/sec—we call it an alpha particle.

The article pretty much debunks [1] by concluding that heavier atoms do most damage, but are still manageable.

Thanks for the correction! Bad memory on my part.

So the article refutes [1] because the relatively easy to manage mechanical effects of those alpha particles on the spacecraft exterior mean that it actually functions as an effective, long-term shield against alpha particles?

> The main problem with running into an atom isn't the physical collision but rather the energy deposited in the spacecraft by the impact

Where is the difference? I don't see none except for level of detail.

They mean the physical damage isn't the big issue, but added heat from the collision is - You don't want a spacecraft to accumulate heat - it's hard to get rid of.

> how dangerous

I would think it's just as dangerous as having something traveling at 20% the speed of light relative to you.