My background: I am a physicist, ex high school science teacher (Monaro High School, Cooma, Snowy Mountains area, New South Wales) then six yrs as university physics lecturer (University of Papua New Guinea, Port Moresby, PNG), then did a Masters in Health Physics which catapulted me into the position of first professional Uranium Mine Radiation Safety Officer in Oz, that was in 1977...
I have been in the mining industry ever since, advancing to Corporate Manager Health and Safety for Western Mining Corporation, then going freelance in 1995 as a consultant, at which time I incorporated Rad Advice & Solutions..
I spent 3 months of 1995 at U of Arizona, with John Lewis et al (Lebovsky, Bottke, Mark Sykes, Tom Gehrels, etc..) picking their brains and working on my thesis on Technical and Economic Feasibility of Mining the Near Earth Asteroids (which gained an Honours MSc at University of Wollongong in 1998). This, and a subsequent paper presented at IAF in Turin and later published in Acta Astronautica, are the documents which Shane Ross quoted extensively.
I incorporated Asteroid Enterprises in 1986, after giving my first asteroid resource recovery talk at an Aussie Space Engineering Conference (Sydney 1986).
My asteroid thesis and subsequent presentation at SFF won me a FINDS grant which enabled further work, including on studies of mining and processing alternatives, and some practical hands-on stuff making and testing cometary simulant material; these studies were reported in Space Frontier Foundation conferences and ASCE Albuquerque Conferences.
My mining industry connection (by having been on the project management team, several times around - Jabiluka U mine and mill, Olympic Dam Cu-U-Au underground mine with complete on site treatment to final products, Beverley U In-Situ Leach, Mt Keith Nickel open pit and concentrator, Mulga Rocks U and Base Metals ISL and open pit, and Nolans Bore rare earths project among others) has given me insight into the non-obvious nature of Project Concept Development. I emphasise, it is often quite hard to decide just what it is one wants to, or ought to do, in advancing some project.
In other words, what product, at what production rate, will give us a high enough rate of return *and* low enough capital cost (Capex) to gain investor commitment?
Multi-product mines present two sides: they are inherently more robust against changes in market conditions; but they are more demanding in metallurgical terms: getting best recovery of commodity 'A' often will compromise good recovery of commodity 'B'. At project startup, you will possibly be faced with the necessity of foregoing revenue from one of your products, just to get started.
It is really, really important to spend quality time on thinking through just what we want the Project to Do.
This is where our conversation is now: for example: - do we want to bring back a whole asteroid, or bags of regolith, or separated processed product? - what is our (a) present market, and (b) future market?? - what mass delivery rate into HEEO will the market accept? now, in 10 yrs, in 20 yrs, etc? - how do we decide which of the multiple alternatives to choose between, in target choice, production size / recovery rate, propulsion method, energy source, product and processing option, etc...
I suppose there is no argument that the commercial support for asteroid resources recovery is likely to come from either SSPS construction, or Orbital Commercial Tourism and support services ie Bigelow etc (or both).
I think we all agree that capture via Lunar Flyby is (by virtue of it being able to deliver up to approx 1.5 km/sec d-v) a "Mission Enabler" and thus I support Jim's desire to find a general trajectory solving methodology as a 'generic need'.
Unlike the case of mining on Earth, where for a copper mine, for example, the valuable metal is maybe 1% by mass of ore and much less when you consider the waste which must also be removed, virtually *all* of the material which we might recovery (scoop up?) from an asteroid will be of significant value.
Say the asteroid regolith contains 10% H2O, 5% other volatiles, 10% reducible Ni-Fe, 10% complex kerogen like hydrocarbons, and the rest silicates, with maybe 50 ppm Platinum Group Metals... Well Bloody Hell, it's all valuable!! Even the crap silicates, which can be used for ballast and radiation shielding, at least..
Virtually ANY Earth-approaching NEA can therefore be considered a potentially valuable target (in a future where there is a market for mass-in-orbit).
As an aside here, note that the value of water or nickel-iron alloy delivered into HEO or into GEO from Earth surface is presently, by virtue of its launch cost, about $40,000/kg. Even with Falcon 9 Heavy, this will still be something like (?) $10,000/kg. (dropping again by another factor of (say) 10 when we get RLVs). So this will also be the upper bound of what we can demand for bulk asteroidal water or iron. Every tonne of asteroid regolith returned to high orbit then contains $1,000,000 worth of water, and $1,000,000 worth of iron. Noting that PGMs have a value of something like $2,000 per ounce, and that an ounce is about 30 grams, then at 50 ppm, the tonne of asteroid regolith contains about $(2000 x 50 / 30) = $3,000. This means that people who think they are going to make money *primarily* out of asteroidal PGMs haven't done their sums. PGMs will only ever be a by-product.
Now, randomly going through the comments that I have seen, and my thoughts:
I agree with Al that seeking to alter the trajectory an entire 300 m diameter Earth-grazing asteroid will *not be allowed*. Except under the circumstances of the object actually being a proven Impact Threat.
That means if we want to return stuff from Apophis then it will likely be bagged regolith. Or simple semi-processed mass, like condensed volatiles (water snow), or magnetically separated Ni-Fe grains.
I have for many years thought that solar steam rocket concept is a good 'fit' with return of water, cos you use some of the extracted mass as your return propellant. Isp is low but you have plenty of reaction mass available. James Shoji at Boeing / Rocketdyne wrote on this, plus more recently L'Garde inflatable reflectors, and the INSTEP Shuttle experiment, suggest this is doable.
Another real 'enabler' (that word again) would be a *developed* mass-driver. This was pursued by GK O'Neill way back in the late 70s / early 80s, but I don't know what the present capability would be. Again, plenty of regolith for reaction mass.
I think any non US Govt program will be unable to access nuclear power. And given the lack of government discretionary money, there will be no Govt program... unless someone identifies an Impact Threat.
However, if we DID need to move an entire 300 m diameter asteroid, i.e. give it a d-v of 10 cm/s, it might not be all that difficult...
Required momentum change: 30 million tonnes x 0.1 m/s = 3 x 10e6 t.m/s
Required reaction mass, at ejection velocity of (say) 100 m/s = 30,000 tonnes.
In open pit mining, mine engineers plan to AVOID fly-rock; here, we WANT it. And a 30,000 tonne burden blast is small beans to the big-pit miners.
Maybe you don't do it all at once, but sequentially, pop-by-pop, so as to avoid possible instability. This could be done by firing sequential 'Deep Impact' type penetrating explosive charges, always hitting the hemisphere you want... How deep? I don't know, but I bet some Open Pit Blasting consultant would be able to give us a fair idea what depth will give maximum mass of maximum-velocity fly-rock.
(Noting here that Apophis is a slow rotator and hence almost certainly a rubble pile.)
Now, how about actually mining on the asteroid, and returning bags of stuff?
Augers, drag conveyors, enclosed scoops, all ought to work OK. Stuff will tend to 'float away' and that will need some thought. Quite complex pieces of equipment can handle many hundreds of times their own mass, on earth, per day. Example, a front-end loader can load something like its own mass in a cycle time of something like 3 minutes. This gives a daily throughput factor of (say) 24 x 60 / 3 = 480. Call it 500. Thus in our case, it is reasonable to visualize a half tonne 'scooper' that could conceivably load (say) 10,000 tonnes in 40 days.
See for example Sandvik Scooptram LH201E, which is about ten times bigger than this, just to get an idea of smallest scale in terrestrial mining. And note I am NOT suggesting this, because it clearly won't work in zero gravity, but this is just to get an idea of scale and throughput....
If all we want to do is load regolith then surely we just scoop it up and eject it (gently) into the bag... which has to be strong enough to resist tearing, and has to be restrained by anchors etc.
Bag mass: Have a look at Monarflex Scaffolding tarpaulin sheeting: areal density = 250 g/m2. A bag to contain a cube of 10m x 10m x 10m = 1,000 cubic metres and thus (say) about 2,000 tonnes of regolith (or about 5,000 tonnes of iron grains, or about 200 tonnes of snow) would mass (6 x 10 x 10 x 0.25) = 150 kg.
Launching such a bag from Apophis, especially given that you may only need a few cm per second, you would use some sort of catapult: the best possible reaction mass is the asteroid itself.
Power: has to be flexible film PV, I think....
Power is in fact a serious constraint.... it would be really nice to have plentiful (nuclear) power...
So what do I visualise: I am assuming remote operation, because manned takes us up in mass and complexity and cost by something approaching two orders of magnitude.
I visualise: mechanically collected regolith, bagged, despatched by some sort of catapult using electrical power to drive it, with Apophis's mass providing the Normal Reaction.
Or, bagged water 'snow', my long-term proposal, with solar steam rocket propulsion, for situation of return with much higher departure d-v requirement.
I visualise smaller total mass returned than the full scale situation described in earlier emails, chosen for colony construction etc. This alleviates concern re d-v imparted to Apophis, if launch is by catapult; and in fact, the lower mass throughput is demanded (constrained) by the reqt to minimize the Project Capex.
Problem: what do we do for in-transit trajectory trimming?? --each bag may need a little VASIMIR or Hall Thruster or something.... Size of this needs scoping out...
But, but, we are getting ahead of ourselves. We need first to figure out what is doable, and what is sellable, in the timeframe.
All the best,
“Keep everything as simple as possible, but no simpler” - A. Einstein
--This email was produced using recycled electrons--
Copyright ©2012 by AsteroidSettlementAndPower.com