Australians lead efforts to move space junk with lasers | Hacker News Reader

Australians lead efforts to move space junk with lasers

bbc.com

33 pointssrikar19 comments

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?

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 ) 2) if a laser vaporises part of a structure, the resultant gas will push against the structure, delivering momentum

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

Wikipedia tells me that lasers have been considered before to fight off the https://en.wikipedia.org/wiki/Kessler_syndrome

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.

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

Space debris is in orbit, which means it's travelling fast. Space debris travels at 7 km/s. That would destroy any net you put up. Space debris that isn't travelling that fast just falls out of orbit.

http://orbitaldebris.jsc.nasa.gov/faqs.html#7

Assuming I haven't misunderstood... the cost of launching 200,000+ nets into orbit would be high (in my opinion, maybe someone has a sneaky solution).

Assuming you could get each net (including guidance and propellant) down to about 1kg (not sure how realistic that is), and you can launch them into orbit for $4000/kg, then that'd be an expenditure of $800+ million not including R&D, manufacture, salaries, etc.

It'd also mean increasing the number of objects in orbit for while.

One of the pie in sky ideas that gets floated is a large aerogel object that can slow down/trap the particles without creating a bunch of new ones.

It would be put in an orbit that crosses orbits with a lot of debris.

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.

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.

Sort of an orbital Katamari Damacy.

And nothing was heard from this ever again.

For those who don't get it see -

http://content.time.com/time/specials/packages/article/0,288...

Maybe they could try badass projects of a slightly smaller scale? Keep going with the badass projects though!

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

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

Australian sharks with frickin laser beams

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!

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.

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