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#26 2012-04-29 18:15:12

louis
Member
From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Planetary Resources Inc.

Surely the obvious thing for PRI to do is to rely on Space X to get them there and just concentrate on the mining technology.


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#27 2012-04-29 19:24:20

Rune
Banned
From: Madrid, Spain
Registered: 2008-05-22
Posts: 191

Re: Planetary Resources Inc.

GW Johnson wrote:

Hi Rune!!  How are you?

Glad to be back smile Other than that, quite busy with exams sad

Mark Friedenbach wrote:

Take a closer look at the names involved. It's a roll-call of PRI's known employee roster.

I knew there was something fishy... smile Well, PR is PR. Might as well get used to it.

Mark Friedenbach wrote:

Also, the $2.4bn costing of the retrieval mission was by NASA costing standards. PRI has stated that they think that their unique operational structure and other cost savings could reduce that price tag by 1 or 2 orders of magnitude, putting it presumably between $24MM and $240MM, which seems more sustainable. No one outside of PRI knows if they can actually achieve that, but it's not impossible and it is what they claim.

Well, at $24M a mission, it would be pretty much free fuel, and the best business in the history of ever... However, I doubt that. For one thing, it's a lengthy mission, meaning lengthy payrolls. Also, lots of ground support/telescope time involved to blow the budget way over the hundreds of millions. Though I have to admit they have gone the smart route and gone about the business of decreasing the price of telescope time first, otherwise their business would have been a no-go from the start. Kudos for that. Have I mentioned a single mission uses up 12 years worth of current worldwide xenon production? That has to be expensive. Yeah, it can be done more cheaply, that's for sure. Nevertheless, I'll buy a two-order magnitude reduction from forecasts for a first mission when I see it. Can it be profitable? I hope so, but I have no idea, which probably means it's close call in search of the right approach to pull it off.

Mark Friedenbach wrote:

It wasn't me that said it, but I'll concur that mass drivers are a severe navigational problem--the ejected masses would be large enough and moving fast enough to destroy any future space craft that crosses paths. It'd be a simple solution today, but certainly come back to bite us in the future.

Hum. Think about the problem for a second. When you are using a mass driver, you are throwing away rocks with masses on the order of kilograms, of which the solar system is literally full of, at several km/s away of your present orbit. Considering where you would use it, the "propellant" either burns in the atmosphere of some inner planet or attains independent solar orbit. I mean, we are talking about going to hunt asteroids at, at most, hundreds of m/s away of earth orbit. You are throwing the rocks kms/s away... No freaking way you are increasing the meteoroid threat in interplanetary travel. Which, considering today's sensor systems, is quite insignificant IMO, but ever present. You could say there is more rubble out there, and more dangerous, than we could ever throw. Fortunately, space is BIG.

Mark Friedenbach wrote:

Otherwise, great analysis. Have you submitted your resume to them yet?

Thanks! And I have half a mind to do so, once it's a bit more finished. Not like I am going to get a really interesting aerospace job here in Spain any time soon... sad

Mark Friedenbach wrote:

I have said for a long time that the only thing holding back a true opening of the space frontier is 1) cheap access to space, and 2) in-situ resources once you get there. SpaceX & competitors are definitively solving #1, and if nothing else PRI is removing the giggle factor from asteroid mining, which solves #2. We are finally on the verge of a real entrepreneurial space frontier, and the accompanying gold rush.

Hear, hear!


Rune. I hope to have bragging rights for hearing here about your space startup some day! wink


In the beginning the universe was created. This has made a lot of people very angry and been widely regarded as a "bad move"

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#28 2012-04-29 20:47:18

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Planetary Resources Inc.

Rune wrote:

Well, at $24M a mission, it would be pretty much free fuel, and the best business in the history of ever... However, I doubt that. For one thing, it's a lengthy mission, meaning lengthy payrolls. Also, lots of ground support/telescope time involved to blow the budget way over the hundreds of millions. Though I have to admit they have gone the smart route and gone about the business of decreasing the price of telescope time first, otherwise their business would have been a no-go from the start. Kudos for that. Have I mentioned a single mission uses up 12 years worth of current worldwide xenon production? That has to be expensive. Yeah, it can be done more cheaply, that's for sure. Nevertheless, I'll buy a two-order magnitude reduction from forecasts for a first mission when I see it. Can it be profitable? I hope so, but I have no idea, which probably means it's close call in search of the right approach to pull it off.

Well you seem to have independently identified the two limiting factors they are currently working on. There's been conflicting reports, but it seem they have either received or a seeking funding from NASA for developing two technologies: in-space laser communication and some sort of advanced propulsion technology. A mesh network of laser communicating probes could relay data to one of their telescopes in Earth orbit, which could then be inexpensively downlinked to Seattle with a DIY setup. I have no real data on what the propulsion is about, but I would presume it would be for some sort of small solar-electric engine using water, amonia, CO2, or some other volatile they expect to find. Brownie points to anyone who can track down these proposals, probably under the name Arkyd Astronautics.

As for mass-drivers, you'd be putting it into a different orbit of course, but it'd still cross it's original orbit at high speed (unless you targeted it to hit an atmospheric object, but the celestial mechanics of doing that accurately and to achieve thrust in the right direction just don't seem plausible). And maybe it's true that the added hazard would be lost in the noise, but at the same time I'm sure that's what people said about industrial pollution in the 18th and 19th centuries. In any case, it could be a public relations problem for PRI, which is billing asteroids as a 100% environmentally friendly, non-polluting source of resources. I guess if you can get it going fast enough to eject it from the solar system (or burn it up in the Sun), that'd be a different story.

Last edited by Mark Friedenbach (2012-04-29 20:48:18)

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#29 2012-04-29 21:29:22

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,418

Re: Planetary Resources Inc.

Space based laser communications http://en.wikipedia.org/wiki/Free-space … munication

http://www.nasa.gov/home/hqnews/2012/ap … posal.html
http://news.yahoo.com/nasa-seeks-game-c … 07442.html

The NASA solicitation will cover two acquisition phases and involve a competitive selection process. During Phase I, proposers will design, analyze and test a scalable solar array system capable of generating more than 30kW of power. The Phase I teams also will identify the most critical technological risks of extending their concept to 250 kW or greater power levels. The intent of Phase II is to prove flight readiness through an in-space demonstration of an advanced, modular and extendable solar array system. After Phase II, follow-on applications will range from high power communications satellites to solar electric propulsion systems.

NASA Solar Electric Propulsion Study Being Conducted By Boeing
http://www.aero-news.net/index.cfm?do=m … 1d73dd032c

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#30 2012-04-30 20:00:34

clark
Member
Registered: 2001-09-20
Posts: 6,374

Re: Planetary Resources Inc.

Okay, problem reduction time.

What is the *existing* demand in LEO?
What commodity is the easiest to produce beyond the LEO space for use in LEO, if you had to?
What the hell do you do with a multi ton metal rock in space anyway?
What are the fabrication requirements for basic onsite construction in LEO/NEO/GEO?

Want to take a short-cut? It's not about where you are, it's about where you want to go.

Couple points to help ponder what the little emperors so clearly see...

We are 25-50 years from in-space fabrication. look it up. We don't even know what we don't know at this point. Even if we could boot strap it tomorrow, we wouldn't, cause the capital costs are, pardon me, astronomical. Amortization through generations does not a business plan make.

A great deal of launch costs are tied up in fuel. Play with the magic numbers when you have a gas station waiting up above. Mass goes down. rockets to the moon start looking a little more attractive. higher orbits get a little closer.

Make it cheaper to get to the moon and you create more demand. You create a built in, long term, customer base. Moon pies, mmmmm.

Extra points if you watch the lobby arm of PRI. Wait for the tax breaks, loop holes, etc. Wait for the spin on how the telescopes are going to also be used for an earth based asteroid detection system. Watch for the sale of telescope time in part, or wholesale, as part of the exo-planet program.

And don't for one second thing that Space-X is the only horse in this game.
fun times, but what do i know.

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#31 2012-04-30 20:41:15

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
Website

Re: Planetary Resources Inc.

The real key, obviously, is cost. If a Falcon Heavy (not reusable) can launch mass into orbit for $1000 per pound ($2 million per tonne), you'd have to get your asteroidal volatiles to low Earth orbit, already processed, for that price. I doubt that's possible any time soon. Just running ground control for six years would probably make the costs too high. If the Falcon Heavy becomes reusable and the price falls another factor of ten, forget it. You'd have to turn to platinum group metals, I think.

As asteroidal body in high lunar orbit or at a Lagrange point is a great idea from the point of view of exploration, radiation shielding, experimental mining, and a significant space development project. But all those reasons sound like reasons for government funding, not private funding.

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#32 2012-04-30 21:48:49

clark
Member
Registered: 2001-09-20
Posts: 6,374

Re: Planetary Resources Inc.

Thanks for playing RobS.

Law of diminishing returns. Even with order of magnitude drops in costs to launch, you have an upper limit on total launch weight. Even with entirely separate launches dedicated to nothing more than fuel, you have an order of magnitude of cost and complexity that kills any potential long range space mission.

Processing of volatiles will be in the order of multi-ton.  It will be a volume business, and rocket launches are not a volume business.

Ground control as we know it will be entirely different. Platinum group metals only make sense if they are planning on playing the futures market.

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#33 2012-05-01 00:43:12

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Planetary Resources Inc.

It's a chicken-and-the-egg problem. There will never be viable large-scale space ventures if we have to haul everything up with chemical rockets, reusable or not. But asteroid (or Lunar) mining is so massive a proposition that it doesn't make sense unless there are viable, demonstrated large-scale space ventures to sell to. Chicken and the egg.

That doesn't mean it isn't possible to chart a path which leads us ultimately to asteroid prospecting and resource extraction as a consequence of a series of shorter-term ventures. Take SpaceX which has a similarly grandiose vision of homesteading Mars--way too long term to be done by private enterprise. But technology development contracts, low-cost satellite launches, and ISS resupply missions seem to be bringing them down that path just fine. PRI seems to be taking a similar route.

Last edited by Mark Friedenbach (2012-05-01 00:44:20)

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#34 2012-05-01 04:52:39

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 29,418

Re: Planetary Resources Inc.

We already do have the chicken in orbit its a matter of using it...We have experimented greatly but now we need to stop doing science and get to the chore of using the technology and new techniques to build while in orbit.
Shortly there will be the alternative to getting here by Russian vehicle by using the SpaceX dragon but who will be  the first to use it....(not from Nasa)....

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#35 2012-05-01 05:14:04

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,418

Re: Planetary Resources Inc.

I find it interesting to visit other space sites to see what they are discussing and here is the link for this topic...much like our forum duplicate threads can get started and this forum is no different with this topic which the mods have merged.

http://www.bautforum.com/showthread.php … s-Inc-quot

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#36 2012-05-01 17:04:48

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

A part of what y'all are debating here (costs of ground control) is something I have written posts about before.  The result you get depends upon whether PRI uses the NASA model,  the ULA model,  or the Spacex model.  If it takes the population of a major American city to support your launches and flights,  when you add up all the contractors and vendors too,  that's the NASA model,  and it is precisely why a shuttle launch was $1.5 B.  At 25 metric tons max payload,  that's $27,000/lb. 

On the other hand,  there's Spacex,  who for the first time in history uses the population of only a small Texas country town to support launches and missions.  This is why Spacex is charging about $2500/lb for a 10.1-max metric ton payload on Falcon-9.  Factor-ten better is no mean feat!  Three cheers for visionary-led private enterprise!

There is a launch vehicle scale effect that applies here:  bigger rockets should lead to lower per-lb payload costs when delivering max payload.  Now,  ULA's Atlas V,  in the -551 and -552 configurations,  is priced at 2400/lb at a max 25 metric ton payload size.  (All of this is LEO from Canaveral.) 

But,  Falcon-Heavy is projected at 53 metric tons for $800-1000/lb on Spacex's website.  Conclusion:  ULA is too high for the payload size,  they ought to be nearer $1500-1700/lb.  Boeing and Lockheed-Martin are gigantic corporations,  while Spacex is not.  Does anybody else see the advantage of a small, lean company here?  (Or the advantage of any for-profit company over a government agency?)

If you think and act like a Spacex,  asteroid mining could actually be profitable.  If you think and act like a ULA,  maybe not.  If you think and act like NASA,  never.  That's the real lesson of what we have seen for the last 50 years or so.  It's hard to argue with numbers interpreted in the light of actual history. 

Comments?

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#37 2012-05-01 22:55:52

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Planetary Resources Inc.

GW Johnson wrote:

Comments?

Preaching to the chior wink

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#38 2012-05-02 08:33:31

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

Just singing like a canary,  I guess.

Do y'all really think they'll find things like platinum in ore bodies rich enough to process in these NEO's?  That's the sort of product with value down here.  The volatiles would have value in LEO,  not down here.  At least to my way of thinking. 

What about the stony minerals?  Any use for them that anyone can see?

I'm not sure about the nickel-iron.  Whether there's any value down here is questionable,  I suppose,  since we have so much recyclable steel.  But for steel construction on the moon,  Mars,  and elsewhere,  it could be quite valuable,  once there's folks there on those places who need it.  Not yet,  but "soon". 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#39 2012-05-02 08:51:10

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

As for chicken-and-egg problems,  that has always obtained with new commercial ventures of any size at all. 

You solve it by bootstrapping and "leverage" (really,  financial cheating).  Do things by increments,  etc.  Things eventually happen,  it's just not nearly as fast as most of us would like. 

Sometimes,  you get public-private partnerships that help by financing some of it with tax money.  Sometimes not (for the next few decades,  I think not,  conditions are just too strained right now to count on that). 

Lately,  I've been betting more on the likes of Spacex,  XCOR,  and several others.  Now there's PRI looks promising,  too.  Vision is not yet dead among us.  That's hopeful. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#40 2012-05-02 11:28:12

Mark Friedenbach
Member
From: Mountain View, CA
Registered: 2003-01-31
Posts: 325

Re: Planetary Resources Inc.

GW Johnson wrote:

Do y'all really think they'll find things like platinum in ore bodies rich enough to process in these NEO's?  That's the sort of product with value down here.  The volatiles would have value in LEO,  not down here.  At least to my way of thinking. 

What about the stony minerals?  Any use for them that anyone can see?

I'm not sure about the nickel-iron.  Whether there's any value down here is questionable,  I suppose,  since we have so much recyclable steel.  But for steel construction on the moon,  Mars,  and elsewhere,  it could be quite valuable,  once there's folks there on those places who need it.  Not yet,  but "soon".

In short, yes. Nickel-iron and other achondrite asteroids are the remains of the core and mantel from a differentiated body that's been broken up. The Earth's crust is mostly light elements because it's the scum that floated to the top of the magma ocean and solidified. If you could make a drill hole to the center of the Earth, you would naturally find the concentration of heavier elements increasing the deeper you go. Ore deposits here on Earth that are not of asteroidal origin are typically put there as a result of volcanic activity, particularly if the magma comes from an upwelling deep under the Earth's surface where rare and valuable metals and minerals are plentiful.

Trouble is, accessing the mantle is near impossible (although that hasn't stopped the Russians from trying), and getting anywhere near the core is science fiction. But S- and M-class asteroids are pre-packaged, bite-sized chunks of such a similarly differentiated body, waiting in sometimes convenient orbits for us to go up there and get them.

Do we expect to find valuable concentrations in NEO asteroids? Yes, absolutely. In fact we expect (and meteoritic evidence backs this up) that nearly all differentiated asteroid fragments are by their nature what we would think of as rich, valuable ores here on Earth. Statistically speaking, it would be rare indeed to find one that is just a regular chunk of ordinary crustal material.

Last edited by Mark Friedenbach (2012-05-02 11:28:48)

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#41 2012-05-02 19:20:32

clark
Member
Registered: 2001-09-20
Posts: 6,374

Re: Planetary Resources Inc.

The answer is that they expect to find high value ore, and they *eventually* expect science to catch up and figure out a way to process the ore. PRI is expecting NASA or private groups to buy access to the mineral body/mass and figure out how to do it. It's all outlined in the feasibility study.

The intial target asteroids will largely be stony due to a variety of competing reasons; even the base mass of rock is considered a solution to solve the galactic radiation problem with long term long distance human space travel.

At the end of the day, all material- stony, volatiles, or high value metals, has value in LEO/NEO. There is almost no realistic business model for returning anything back to earth (aside from small amounts of material for scientific research).

You have to look at all of this with the assumption that NASA's next step is not mars. If our next step is a return to the moon, or a trip to an asteroid (or some combination of both) then an asteroid in lunar orbit helps in a variety of ways. Nasa will subsidize most of what PRI wants to do. DOD will purchase most of what happens in LEO.

If I were a smarter man, I would watch how PRI leadership fund political parties in the US and the subsequent space policy decisions and directives for Nasa.

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#42 2012-05-03 10:02:03

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

If you trust NASA's findings on radiation exposures and risks,  they had a report defining all that stuff,  which was on the internet.  It appears to date to about 1992.  I abstracted the "meat" and put it together in a single terse article on my "exrocketman" site.  To me it looks like the radiation issues can be handled fairly easily for voyages maybe up to several years,  with very practical shielding made out of stuff you have to carry anyway.  The shielding is primarily to save you from solar flare events.  But,  it will be career limit exposures to cosmic rays that ultimately limit the duration of such voyages.  http://exrocketman.blogspot.com

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#43 2012-05-03 21:58:19

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 29,418

Re: Planetary Resources Inc.

The contents of water, hydrogen plastic and maybe magnetic fields....

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#44 2012-05-04 09:21:06

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

How to reach an NEO with what we have this year or next,  to support prospecting for mining?  Hmmmmm. 

How about launching two Falcon-Heavies?  One has the unmanned spacecraft (whatever it is) that will go to the NEO.  The other payload is nothing but a giant propellant tank made out of a Falcon second stage,  but without engines.  The vehicle with the NEO spacecraft keeps its second stage,  using it to circularize in LEO at near-depletion of propellant.  The second vehicle is just a refuelling tanker. 

Once refueled in LEO,  the spacecraft uses the refueled Falcon second stage as its propulsion for departure and rendevous,  much like we used the Saturn S-IV-B stage decades ago.  Except,  I'd plan to use it for the rendezvous with the NEO,  too,  that's typically a significant delta-vee.  Then the spacecraft itself can prospect the NEO,  collect samples,  and perhaps return. 

I'm thinking we'll need men to oversee the refuelling transfer in LEO.  Certainly to safely dock the two big "spacecraft" and make the fluid hookups.  So,  the tanker probably has a manned Dragon on its nose.  Crew of 2? 

This is not an idea for sending men to an NEO,  just a prospecting robot.  Sending men requires a different kind of vehicle,  one resembling a manned Mars transfer vehicle.  That's a different problem,  but the same basic transfer vehicle assembled in LEO could serve.  The difference is that you don't need a lander to visit NEO's. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#45 2012-05-04 10:18:53

Rune
Banned
From: Madrid, Spain
Registered: 2008-05-22
Posts: 191

Re: Planetary Resources Inc.

GW Johnson wrote:

What about the stony minerals?  Any use for them that anyone can see?

To make the radiation problem go away for any long-term habitat outside the Van Allen belts takes about 10-20mT/m^2 of any relatively light element... honestly, I can't think of a better use. And I mean go away as in it's as safe to live there as on the surface of Earth. Well, maybe you could also use some for glass for the windows in the greenhouses. Or dirt for the plants to grow in. I see it at least as crucial a resource as water, really.

So, you know, not to make or refuel ships. To make homes. The gravity wells are well stocked with radiation shielding, but any really good orbital location has this single defect of lacking... well, stuff. Fix that, and planetary chauvinism has a much harder case in colonization discussions.

GW Johnson wrote:

How to reach an NEO with what we have this year or next,  to support prospecting for mining?  Hmmmmm.

How about launching two Falcon-Heavies?  One has the unmanned spacecraft (whatever it is) that will go to the NEO.  The other payload is nothing but a giant propellant tank made out of a Falcon second stage,  but without engines.  The vehicle with the NEO spacecraft keeps its second stage,  using it to circularize in LEO at near-depletion of propellant.  The second vehicle is just a refuelling tanker.

Once refueled in LEO,  the spacecraft uses the refueled Falcon second stage as its propulsion for departure and rendevous,  much like we used the Saturn S-IV-B stage decades ago.  Except,  I'd plan to use it for the rendezvous with the NEO,  too,  that's typically a significant delta-vee.  Then the spacecraft itself can prospect the NEO,  collect samples,  and perhaps return.

I'm thinking we'll need men to oversee the refuelling transfer in LEO.  Certainly to safely dock the two big "spacecraft" and make the fluid hookups.  So,  the tanker probably has a manned Dragon on its nose.  Crew of 2?

This is not an idea for sending men to an NEO,  just a prospecting robot.  Sending men requires a different kind of vehicle,  one resembling a manned Mars transfer vehicle.  That's a different problem,  but the same basic transfer vehicle assembled in LEO could serve.  The difference is that you don't need a lander to visit NEO's.

Doubtful. Progress seems to have no problem performing refueling operations on it's own, and I'm sure we can even improve on that. Other than that, a Falcon Heavy could launch a pretty hefty payload to Earth escape directly, and it's almost nothing from there to a particular asteroid. Whomever can't pack a decent robotic prospector in >10mT (or several if they haven't got to get samples back, or an orbiter/lander combo) deserves their aerospace engineering grade rescinded. I mean, an Atlas V with half the lift launched Curiosity, it's cruise stage, and the descent stage to Mars. Asteroids are closer, and Falcon H is way bigger. Keep it simple.

And Clark... well, I agree, nothing more really. smile


Rune. Must be one of these choir guys. ^^


In the beginning the universe was created. This has made a lot of people very angry and been widely regarded as a "bad move"

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#46 2012-05-04 11:09:12

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

Oh,  I know the easiest NEO's are not far from LEO,  but the bulk of them are tougher to reach,  having more elongated orbits.  That's why I suggested a pair of Falcon-Heavies,  to reach the more difficult targets,  and perhaps even travel from one to another to another to another ........  Plus,  the spacecraft itself can be bigger,  heavier,  and more capable.  If we're going to go prospect the NEO's,  let's look at a whole bunch of them.  They're all different,  or that's the way it seems,  anyway.  More likely to find what we want by visiting many.  I picked Falcon-Heavy for $800-1000/lb payload at max payload 53 tons.  It's 2.5 to 3 times cheaper than Atlas-V 551/552 at $2400/lb at 25 tons.  Thinking bigger is actually cheaper,  in many ways!!!!

Radiation shielding:  doesn't take very much dirt to shield solar particles.  I was thinking equivalent to 20 cm thickness of water.  At an effective sp.gr about 2 for "dirt",  that's only about 10 cm of said "dirt".  Cosmic rays,  that's also about as good as it gets,  unless you go with meters and meters of thickness,  due to the secondary particle shower.  There's going to be some sort of waste crap that can serve as "dirt" almost anywhere you go. 

It's the career limit on cosmic rays you worry about for long-term exposure,  since the thin shield only cuts it down crudely by a factor of 2.  Otherwise,  you have to have a really thick shield.  Solar minimum GCR is 60 REM/year.  Cut that in half to 30 with a thin shield.  If the astronaut is already old enough to take the high career limit of 400 REM,  it'll take over 10 years to accumulate,  as long as he doesn't go outside.  Younger people are allowed less,  and cannot stay as long. 

Refueling is "automated" with Progress,  I know,  but it's sort of a restricted case,  and not everybody is doing it yet.  Besides,  overseeing the tasks,  and making sure everything happens correctly with refueling,  is a good excuse for astronauts to fly.  So,  why not?

.... choir boy's singing again.......

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#47 2012-05-04 17:11:55

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 29,418

Re: Planetary Resources Inc.

Progress refuels with a hydrogel type fuels not cryrogenic...

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#48 2012-05-05 09:26:28

Rune
Banned
From: Madrid, Spain
Registered: 2008-05-22
Posts: 191

Re: Planetary Resources Inc.

GW Johnson wrote:

Radiation shielding:  doesn't take very much dirt to shield solar particles.  I was thinking equivalent to 20 cm thickness of water.  At an effective sp.gr about 2 for "dirt",  that's only about 10 cm of said "dirt".  Cosmic rays,  that's also about as good as it gets,  unless you go with meters and meters of thickness,  due to the secondary particle shower.  There's going to be some sort of waste crap that can serve as "dirt" almost anywhere you go.

It's the career limit on cosmic rays you worry about for long-term exposure,  since the thin shield only cuts it down crudely by a factor of 2.  Otherwise,  you have to have a really thick shield.  Solar minimum GCR is 60 REM/year.  Cut that in half to 30 with a thin shield.  If the astronaut is already old enough to take the high career limit of 400 REM,  it'll take over 10 years to accumulate,  as long as he doesn't go outside.  Younger people are allowed less,  and cannot stay as long.

Hey, just to be clear, I'm with you there. Ships don't need that much, you can probably make do with a water-lined storm shelter. But in the long run, you want to raise kids there (wherever there is), or we are forever confined to earth, so yeah, eventually slag used for rad shielding is going to be both valuable, and necessary. Perhaps even scarce compared to, say, metal alloys, if we go by the percentage of mass of virtually every proposed orbital habitat.

GW Johnson wrote:

Refueling is "automated" with Progress,  I know,  but it's sort of a restricted case,  and not everybody is doing it yet.  Besides,  overseeing the tasks,  and making sure everything happens correctly with refueling,  is a good excuse for astronauts to fly.  So,  why not?

I one word? Cost. Adding a manned capsule is adding about 7-10mT to the launch mass. Considering the size of current launchers, you would be throwing away between 50 and 15% of your payload each flight just for starters (and 15% is a slimmed Dragon in a Falcon Heavy, and none of those is flying), when a couple tons of service module can do the job. And we can make better refueling systems than those of Progress, or we haven't advanced anything since the eighties, and I don't accept that. And just to drive the point home: if it's an unmanned probe no one cares about, mission control can be 5 guys in a trailer. If it's manned... well, see Houston. That's the kind of thinking that got us the shuttle, the 125mT Heavy lift launch system that could deliver 25mT of useful cargo and risked people to do it.

If "you" (I love using this hypothetical "you", have you noticed?) want to take advantage of low launch costs, then please do: Mass-produce a fleet of 5-10mT unmanned probes, at the very least several tens of them, enough so each costs maybe 50M (and that would be at least an order of magnitude reduction in costs for each, so maybe hundreds to make that happen), and launch them in packs of three in Falcon Heavies in direct trajectories. There, triple-redundant asteroid prospecting at 300M a pop. Nasa might even buy some as low-cost missions. And in 5mT you pack as much mass as a geosync comm bird, so don't tell me you can't fit enough stuff to do a decent inspection, maybe even return samples, and certainly serve as communication relays for other probes if they are situated right. Hell, the probe that returns the 7m 500mT rock in the famous paper is about 17mT if memory serves right, and 13 of those are Xenon. So maybe some probes can have bigger tanks and electric drives and return sizable rocks to cislunar space directly (that would be a whole FH launch, but what the hell, 500mT of resources at perhaps 300M if you do enough of them).

All of that only works if you get enough volume to dilute the costs of extended ground support, however minimal it is. So the big problem is, as always, will there be enough customers?


Rune. It's funny how I switch from speaking about the far future and the present day in a couple of lines.


In the beginning the universe was created. This has made a lot of people very angry and been widely regarded as a "bad move"

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#49 2012-05-05 10:20:33

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 5,728
Website

Re: Planetary Resources Inc.

Aww,  Rune,  I was just looking for an excuse to fly.  smile

All this focus on the bottom line killed full-service gasoline stations,  too.  The dollars ain't everything,  but so many forget that,  these days. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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