
Australians lead efforts to move space junk with lasers - srikar
http://www.bbc.com/news/world-australia-29847830
======
tribaal
Could somebody explain to me (non-physicist) what the principles at play are?

Is it "simply" that they fire a strong laser at the front of the object to
slow it down, so that orbital mechanics do the rest and make it burn up?

Do lasers really allow you to "push" things?

~~~
thegp
not a physicist, but an electrical engineer.

At least 2 principles that I know allow a laser to push things:

1) photons do have impulse, given by its energy divides by the speed of light.
This causes Radiation pressure (see
[https://en.wikipedia.org/wiki/Radiation_pressure](https://en.wikipedia.org/wiki/Radiation_pressure)
) 2) if a laser vaporises part of a structure, the resultant gas will push
against the structure, delivering momentum

~~~
FreeFull
Both principles have an impact, and in this case, I think the second one is
the one that causes most of the impulse.

------
imurray
Wikipedia tells me that lasers have been considered before to fight off the
[https://en.wikipedia.org/wiki/Kessler_syndrome](https://en.wikipedia.org/wiki/Kessler_syndrome)

------
panzagl
Nice press release- this is all old news. If you know where something is well
enough to hit it with a laser, you're probably better off leaving it where it
is and tracking it.

------
juedcuIcZi
why don't somebody build a net and a parachute to pull it down with high
velocity ?

~~~
nine_k
What could work might be a purpose-built spacecraft with a low-power but
efficient engine (e.g. ion drive). This spacecraft would align velocities,
then touch and bind every piece of space debris along its orbit. Eventually it
would snowball enough to just let smaller pieces of debris hit it and stick.
After it has become too heavy to maneuver, or when the propellant is depleted,
the spacecraft would go down and burn in the atmosphere.

The problem is the way to properly bind the pieces of debris.

~~~
JoeAltmaier
Sounds a bit like rain formation: nucleation and aggregation. But space is
big, and the spacecraft is not attracting anything (too small for gravity to
matter). Not sure even a big snowball is going to collect much debris. A solar
sail perhaps? Cross-section has to be key.

------
YungLean
And nothing was heard from this ever again.

~~~
aaron695
For those who don't get it see -

[http://content.time.com/time/specials/packages/article/0,288...](http://content.time.com/time/specials/packages/article/0,28804,1934259_1934610_1934634,00.html)

~~~
discardorama
Their website would seem to indicate that they're still in business:
[http://www.enviromission.com.au/EVM/content/home.html](http://www.enviromission.com.au/EVM/content/home.html)

But I couldn't find any information about the solar tower they were building.

------
simonmales
Australian sharks with frickin laser beams

------
authatheist
Feel like playing with laz0rz and shit? How about using your own money to
arrange for that? Don't wanna? Well, good thing you can just use shitloads of
money that's been forcefully taken from people!

~~~
noonespecial
I'd totally and completely voluntarily pay extra taxes if I knew it was going
to be spent _blasting junk out of orbit with giant lasers_. Hell, I'd buy
tickets just to watch.

