Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[mainiac]

No, ion engines use propellant.  Unlike a rocket the propellant does not need to contain chemical energy however you are still shooting stuff out the back end.  However a mass accelerator (such as a steam catapult, similar to those on aircraft carriers or an electromagnetic accelerator) uses no propellant.  This is why I keep repeating NO PROPELLANT.

[palsch]

No, ion engines use propellant.  Unlike a rocket the propellant does not need to contain chemical energy however you are still shooting stuff out the back end.  However a mass accelerator (such as a steam catapult, similar to those on aircraft carriers or an electromagnetic accelerator) uses no propellant.  This is why I keep repeating NO PROPELLANT.

OK, my original post on this topic was;

The are two main options with mass drivers. Either you sacrifice the vast majority of your interesting mass and energy rich material to make a launch platform or you use a smaller fraction of mass as reaction mass during transit, with the driver acting as the engine.

In the latter case things reduce the ion engine problem.

In the former case you are extremely limited in the amount of mass you can send back. I'd actually go with this option if a belt mining operation were established, simply because I'm not interested in sending much back to earth. But for those who want a significant return on a commercial investment you aren't talking about a good option.

And frankly it doesn't change the energetics of the problem at all.

[mainiac]

Send half the mass on a "direct" route.  Send half the mass on a "reverse" route.  Both get to earth, one just gets there a lot faster.

[Rose]

Stream starts in 10 minutes.

http://www.planetaryresources.com/
http://www.spacevidcast.com/live/

[Knight of Fools]

I hope they'll be hiring lots of impressionable college kids for this. I'm all for venturing into space to catch asteroids.

[Rose]

http://youtu.be/7fYYPN0BdBw

[timotheus]

Could we use an orbiting solar farm (orbiting earth), and have it transfer energy via laser to super efficient solar panels on the mining ships? It could reduce the need for fuel.

A laser that keeps focus for long distances isn't very feasible now, but maybe in the future?

[palsch]

A laser that keeps focus for long distances isn't very feasible now, but maybe in the future?

Lasers have fairly fundamental properties that determine their divergence. You can't get around that, but you can put a lens in front of them. The difficulty would be in getting a laser/lens setup that would work with the energies and distances involved. I'd look at projects like LISA where lasers are supposed to maintain focus over significant spacial distances, although at lower power.

Or just dig into laser propulsion in general. I'd always start with the sceptical sources so you can find the problems that need to be addressed.

[RedKing]

Can't seem to view the stream, and I had to ditch out of there before I began raging at all the stupid comments in the UStream chat feed. At this point, I'd volunteer to work in space for them just to get the f--k away from people in general.

[andrea]

that was great! thanks for posting the livestream.

[RedKing]

I've been boning up on various propulsion methods over the last few days since this news broke, and I have to say I'm intrigued with the VASIMR design, even though it definitely has its vociferous critics.

Also fascinated with some work being done on the use of a thin "shield" of magnetized plasma to act as a portable magnetosphere and deflect solar radiation. The more sci-fi becomes sci-fact, the happier I get.

[PTTG??]

China's going to shoot him down, if the Austraila doesn't. Well, I may be wrong- I'm thinking more about rare earth minerals, not platinum group metals, I'm not sure who mines them on earth.

If they go for the Earth Trojans, they won't even need to ship them very expensively to get them here... though those are probably less wealthy than the Asteroid Belt rocks.

They're probably going to use ion engines. I can't wait for Magentoplasma to get developed, then we'd seriously be driving these things.

[mainiac]

In any case, this is the study they are basing the early stages on. Targeting a C-class near earth asteroid, approximately seven meters in diameter and with a total mass of around 500,000 kg. The goal is to bring it into lunar orbit. Estimated costs there are ~$2.6bn

....

3) Even so, how cost effective this is depends on the useful mass fraction. The same costs would put ~20 Heavy Falcon rockets into lunar orbit, worth 320,000kg of payload. You get an extra 180,000kg from the asteroid mission, but if it's more cost effective depends on just how useful that mass is.

That $2.6bn price tag is based on the Atlas V launch costs.  But your 320,000 kg payload is based on the Heavy Falcon launch costs which are projected to be lower.  This is rather crucial because the Heavy Falcon is projected to have lower launch costs at high orbits.  So this is not quite an apples to apples comparison.

Also this would probably involve some serious economies of scale.  Launch costs are ~128 million since this is designed to fit on a single Heavy Eagle.  I doubt that much of the remaining 2.5 billion are costs of your capture vehicle.  These costs are instead going to be thinks like asteroid location (the initial space telescope should identify about 5 targets a year), hardware and software development, etc.  A lot of that is going to be non-reoccurring.