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[...] Part III: Resource Utilization Considerations Posted By: Paul D. Spudis — Lunar Exploration,Lunar Resources,Lunar Science,Space Politics,Space Transportation,Space and Society | Link | Comments (27) [...]

Pingback by Destination: Moon or Asteroid? Part I: Operational Considerations | The Once and Future Moon — September 2, 2011 @ 4:08 am

This is really an excellent set of articles which makes a clear and convincing for the Moon over a NEO as out first step. The one thing I would add is each transporting craft would be tied up for longer for each trip and so more craft would be needed to make the same rate of deliveries from a NEO than the Moon. This is important, because a fair amount of the expenses will be the cost of the craft divided by the number of deliveries before the craft becomes inoperable. So, if you want a delivery of water ice once a week, you would need only one between the Earth and the Moon but 24 or more between Earth and an NEO.

Comment by JohnHunt — September 2, 2011 @ 10:25 pm

In addition I would say the Moon has it’s own market.
There could be many different customers for rocket fuel coming to the Moon.

Whereas an asteroid is not a destination for customer. With Asteroid your market will be cis-lunar and/or LEO- not at the asteroid itself.
In addition the delta-v penalty of the Moon requires more rocket fuel to be used- more demand for rocket fuel.

The lunar surface has the highest cost to get rocket from earth to, this also means rocket fuel could sell for a higher price and compared to High earth orbit or LEO.
Once one is producing hundreds to thousands of tonnes of rocket per year on the Moon, the moon will probably be the cheapest rocket fuel in space. But in start up phase were one might be making small quantities of rocket fuel per year [less than 100 tons] you have higher highest price you could charge.
The biggest factor which will affect lowering lunar rocket fuel price is demand for rocket fuel in lunar orbit, L-1 or elsewhere in High Earth orbit. To provide rocket fuel to High earth orbit will require lowering the cost to make lunar rocket, so that the cost of shipping the rocket is at or at lower price than rocket fuel which could shipped from earth.
Or in sense rocket fuel has a kind tariff, for start up business that allow higher local price, but then really turn a profit it needs to export lunar rocket fuel which phases out this “tariff”.

Comment by gbaikie — September 2, 2011 @ 11:48 pm

There was a little discussion thread about bringing an asteroid into Earth orbit over at NSF. As I pointed out there, even if the risk of an actual collision with the Earth was minimal, there would still be a big problem with orbital debris released from an unconsolidated asteroid. This problem would be especially acute in Earth orbit, but it’s a non-negligible consideration even if the asteroid isn’t in Earth orbit IMHO. People used to think that debris in Low Earth Orbit would never be an issue either, because space is so damned BIG.

Conversely, that’s another advantage of the Moon: you knock a chunk off, it will fall back to the ground.

Comment by Warren Platts — September 3, 2011 @ 10:52 am

Dr. Spudis wrote:
“The water in carbonaceous chondrites is chemically bound within mineral structures.”

In a previous discussion I asked if Carbon and Nitrogen existed on the Moon in sufficient concentrations to be used both for life support and industrial purposes and you replied that they did.

Can you give a comparison of the availability of these elements in the carbonaceous chondrite (or other)asteroids as opposed to the Moon?

Comment by Joe — September 3, 2011 @ 1:36 pm

[...] Spudis cuts to the heart of the matter in this entry in “Destination: Moon or Asteroid.” Share this:FacebookDiggTwitterEmailLike [...]

Pingback by Destination: Moon or Asteroid Part 3 is up « Once Upon A Time in Heaven — September 3, 2011 @ 2:41 pm

Can you give a comparison of the availability of these elements in the carbonaceous chondrite (or other)asteroids as opposed to the Moon?

Carbonaceous chondrites have significant amounts of all of the light elements, much more than the typical equatorial lunar regolith. However, we suspect that these elements are present in great abundance in the polar dark cold traps (being mostly volatile cometary residue) and in much greater concentration than in any meteorite. For C1 chondrites, C is about 3-4 wt.% and N about one-tenth of that amount. Water is highly variable, between 3-20 wt.%, with the lower number being more common. In contrast, ice in the polar craters is >90 wt.% water and a few percent C and N (mostly in the form of methane, organics, and ammonia).

As mentioned in the post, also note that water in chondrites is chemically bound, mostly in clays and other hydrous mineral phases. It requires much more energy to extract that water than it does to melt polar ice.

Comment by Paul D. Spudis — September 3, 2011 @ 3:48 pm

Dr. Spudis,

Have you heard of this process yet?

http://www.ibtimes.com/articles/206995/20110901/new-alloy-to-revolutionize-clean-energy-by-generating-hydrogen-on-the-cheap-hydrogen-water-sunlight.htm

Would this help lower costs for producing hydrogen on Luna?

Comment by Vladislaw — September 3, 2011 @ 4:16 pm

No, I have not. Looks promising but if it doesn’t work out old fashioned electrolysys is available to dissociate water into its component gases.

Comment by Paul D. Spudis — September 3, 2011 @ 4:40 pm

Comment by Paul D. Spudis — September 3, 2011 @ 3:48 pm

Thanks.

If you will indulge me, I will state what I think I just learned. Please correct me where I mess up:

- Water in the polar dark traps of the Moon is believed to be at least 4.5 times the concentration as that available in the best case in the asteroids and in a more accessible form.
- Carbon in the polar dark traps of the Moon is believed to be at least equivalent to the concentration as that available in the best case in the asteroids and in at least as accessible a form.

- Nitrogen in the polar dark traps of the Moon is believed to be about 10 times to the concentration as that available in the best case in the asteroids and in at least as accessible a form.

Comment by Joe — September 3, 2011 @ 5:19 pm

Yes, that’s pretty much it, as best as we can tell. I fully admit that these estimates need verification by in situ measurements on the ground at the lunar poles.

Comment by Paul D. Spudis — September 3, 2011 @ 5:21 pm

While I agree that mining the Moon is likely to happen before mining of NEO’s, I think there are a few points not being fairly covered here:

If you’re extracting water with the intent of dissociating it for rocket fuel the energy taken to extract it is going to be minor compared to that used in the electrolysis of it.

I don’t think you can rule out the existence of subsurface deposits of higher purity volatiles in NEO’s.

Applying solar thermal methods to extract valuables seems likely to be far easier on a small body in space than at the Lunar poles.

In reply to Warren Platts, I suggested at NSF that the whole NEO should be bagged, both to avoid the escape of debris, and to catch volatiles, the bag could be designed as a heat trap, lifting the temperature of the NEO and vaporising the volatiles, which could then be easily collected, no earth moving required.

Comment by Andrew W — September 3, 2011 @ 5:56 pm

so much gold was produced during the 1849 California Gold Rush that the world market price of gold decreased by a factor of sixteen.

What the link actually says is:
The Gold Rush to California in 1849 resulted in such large quantities of gold found that the value of gold became less. Previous to this, gold was 16 times more valuable (16x more silver in a silver dollar than gold in a gold dollar).

Which sounds to me more like the price of gold dropped from being 16 times that of silver, not necessarily a claim that the silver/gold price dropped to parity (which I doubt).

Obviously if large quantities of PGM’s came onto the market from asteroid mining the price would drop, dropping the profit margins of the miners – but once started I think it’s fair to argue that rapid improvements in such a new field would also see rapid declines in the cost of mining, and obviously lower cost raw material inputs would be beneficial to the global economy.

Comment by Andrew W — September 3, 2011 @ 6:39 pm

Comment by Paul D. Spudis — September 3, 2011 @ 5:21 pm
“I fully admit that these estimates need verification by in situ measurements on the ground at the lunar poles. “

Thanks. That helps me a lot in formulating what specific policies I would support as priority in moving forward (like anybody cares). I was already pretty sure as to the HSF components. Now I can add to the list robotic assessment of the exact nature of the resources in the polar dark traps of the Moon.

Comment by Joe — September 3, 2011 @ 6:40 pm

We need the Moon as a renewed manned destination, much the same way as Project Apollo needed Project Gemini. Everything that the Mars zealots want to do on the Red Planet can and must be tested for viability, prior. A dusty planetary surface is needed, as the testing ground. More endless circling in LEO will teach us NOTHING! Does America have an astronaut corp, just to keep them from ever having to get their boots & gloves dirty??! I mean: there is no dust, no regolith, no grainy sands to ever have to deal with in LEO. Plus, you can neither stand, nor walk, nor drive a roving vehicle in LEO. Nor for that matter, on an NEO. The Moon wins out in this “debate” hands down! NEO’s were merely picked out of the blue as a beyond-LEO destination in order to denigrate & exclude the Moon. Those who had a phobia over the U.S. ever doing a Lunar Return are the same ones who came up with all this Asteroids-versus-Luna jazz. When Lewis & Clark came back from their far-West adventure, did the nation decide to skip ever having to go back?! Of course not! [Zebulon Pike lead another far-West surveying expedition in near the same time frame; but of course, there were other missions sent out to the American West of the 18oo's.] Folks out there: COME ON! The Moon is the primary planetary destination for us to deal with beyond LEO. NEOs can wait! Keeping astronauts alive beyond the Van Allen Belts, beyond the Ionosphere, for any appreciable length of time….THAT IS THE intermediate OBJECTIVE OF THIS GAME.

Comment by Chris Castro — September 4, 2011 @ 12:04 am

If you’re extracting water with the intent of dissociating it for rocket fuel the energy taken to extract it is going to be minor compared to that used in the electrolysis of it.

Some of it will be dissociated, some of it will not (we need water for life support and radiation shielding). But for propellant production, the energy to break down water still has to be spent regardless of whether you get the water as ice or as clay — in the latter case, you have already used significantly more energy to get the feedstock to begin with. My argument is that the total energy expended is higher from NEOs than from lunar polar ice.

I don’t think you can rule out the existence of subsurface deposits of higher purity volatiles in NEO’s.

There’s not much in planetary science that can be “ruled out” but there is no evidence for any free water in NEOs either.

Applying solar thermal methods to extract valuables seems likely to be far easier on a small body in space than at the Lunar poles.

We have constant sunlight at the poles as well as in free space, so the descriptor “far easier” is entirely a matter of perspective.

Which sounds to me more like the price of gold dropped from being 16 times that of silver, not necessarily a claim that the silver/gold price dropped to parity (which I doubt).

Actually, it means that the intrinsic price of gold was less than it was before because the market was flooded with new supply. This devaluation occurs with every new major gold strike. All I am saying is that dreams of bringing tons of platinum back to Earth and selling it at the current market price (about $1900 per ounce) is not likely — the infusion of vast new supply would make the price plummet.

In any event, these are minor points — its the accessibility of the resources and the difference in processing streams that differ between NEOs and the Moon and make the Moon the most attractive target.

Comment by Paul D. Spudis — September 4, 2011 @ 4:19 am

Andrew W: “Applying solar thermal methods to extract valuables seems likely to be far easier on a small body in space than at the Lunar poles.”

Dr. Spudis: “We have constant sunlight at the poles as well as in free space, so the descriptor “far easier” is entirely a matter of perspective.”

Well, not exactly “constant sunlight” on the lunar poles, but how about “fairly constant in some places”. Maybe Andrew W means that due to it being a small enough body (less height variation), the poles might have truly constant sunlight. I know they have spin rates and poles but how those are oriented to the Sun I haven’t looked at. Intuitively, it seems unlikely the poles for such small bodies would be aligned normal to the elliptic, but maybe that’s how orbit mechanics works it out to be.

Of course, if he is suggesting having a big solar concentrating mirror orbiting near the asteroid, then that would be a totally different story.

Comment by James Fincannon — September 4, 2011 @ 12:29 pm

The exploitation of NEO asteroids for resources is a good idea, IMO, since any resource that can provide water, oxygen, hydrogen, carbon, and nitrogen or even simple mass shielding from radiation to the regions within cis-lunar space cheaper than from Earth would be of great economic value. However, I think its obvious that sending humans out to exploit NEO asteroids would not be economically viable which is another reason why a manned mission to a NEO asteroid would be a huge waste of tax payer dollars.

Using unmanned light sails to capture small 100 to 1000 tonne NEO asteroids and transporting them to Earth-Moon L4 or L5 for exploitation or sending out chemical or nuclear rockets to shift small asteroids into Earth-Moon Lagrange point halo orbits would be options that would be far more economical than any manned missions.

However, once humans can send out fully shielded manned vessels deep into interplanetary space then the resource exploitation of large asteroid belt worlds by human industrial colonies on asteroids such as Ceres, Vesta, Pallas, and Hygeia should be economically viable.

Comment by Marcel F. Williams — September 4, 2011 @ 1:49 pm

Comment by James Fincannon — September 4, 2011 @ 12:29 pm
“Of course, if he is suggesting having a big solar concentrating mirror orbiting near the asteroid, then that would be a totally different story.”

Comment by Marcel F. Williams — September 4, 2011 @ 1:49 pm
“Using unmanned light sails to capture small 100 to 1000 tonne NEO asteroids and transporting them to Earth-Moon L4 or L5 for exploitation or sending out chemical or nuclear rockets to shift small asteroids into Earth-Moon Lagrange point halo orbits would be options that would be far more economical than any manned missions. “

The problem with both these scenarios is that “these rocks are irregularly shaped, rotation is not the smooth, regular spin of a planet, but more like that of a wobbling toy top” (per part one of this series of articles). To make both work this wobbling spin would have to be negated and the asteroids roll/pitch/yaw stabilized.

I am not suggesting this is impossible, but it will require considerable more in space propulsion capability than we now have available and almost certainly the presence of humans at the work site. Once we have sufficiently developed lunar resources to develop these capabilities, working on both these techniques for asteroid resource utilization will be very desirable.

Comment by Joe — September 4, 2011 @ 3:23 pm

Maybe Andrew W means that due to it being a small enough body (less height variation), the poles might have truly constant sunlight.

With a small asteroid you could bag the whole thing and have very light mirrors floating close to it to heat it all.

At the lunar pole your mirrors have to be rigid to hold their shape against gravity and be mounted on a rotating mast to track the Sun, they’ll have to focus the sunlight onto the patch of ice several km away, that ice once vaporised has to be collected and piped out of the near absolute zero temperatures of the crater to storage.

Alternatively I suppose the ice could be loaded and transported frozen to a processing facility on a peak, but that I think would be more expensive.

Another advantage of asteroid mining over lunar is that you can get pretty good Isp from just water using only solar thermal steam rockets, the lower T/W ratio of such a system is less important when you don’t have to launch out of a gravity well.

Comment by Andrew W — September 4, 2011 @ 6:53 pm

If extracting a mole of water chemically from asteroids requires 2-3 orders of magnitude more work than heating it, that’s minimum 1.3 MJ/mol (assuming the ice keeps at 100 K for a melting heat of at 13 kJ/mol). Electrolysis pegs at 260 kJ/mol.

Comment by Prez Cannady — September 4, 2011 @ 10:51 pm

@James Fincannon

“The problem with both these scenarios is that “these rocks are irregularly shaped, rotation is not the smooth, regular spin of a planet, but more like that of a wobbling toy top” (per part one of this series of articles). To make both work this wobbling spin would have to be negated and the asteroids roll/pitch/yaw stabilized.

I am not suggesting this is impossible, but it will require considerable more in space propulsion capability than we now have available and almost certainly the presence of humans at the work site. Once we have sufficiently developed lunar resources to develop these capabilities, working on both these techniques for asteroid resource utilization will be very desirable.”

Small asteroids that are 100 to 1000 tonnes in mass should be way less than 10 meters in diameter. So it shouldn’t be too difficult to capture them within rotating containers with lengths and diameters that are nearly 10 meters designed to match the rotation of the intended asteroid and stopping the asteroid’s rotation once it is captured. Asteroids that size should also be easy to process within structures deployed at L4 or L5 by heavy lift vehicles from Earth.

To minimize delta-v requirements, you’d probably need a reusable one or two kilometer in diameter light sail weighing 35 tonnes or less operating between the Earth-Moon Lagrange points and the NEO asteroid regions to transport the 10 meter in diameter asteroid capturing vehicle (5 to 10 tonnes?) to the NEO asteroid and back to Earth-Moon L4 or L5 with its captured asteroid.

Comment by Marcel F. Williams — September 5, 2011 @ 2:31 pm

I have to confess that I misread “2-3 orders of magnitude” as “2-3 times”, so I went to the link inThe processing of natural materials to extract water has many detailed steps…

Was that the right link Paul? It said there was water in asteroids in the form of ice, I saw nothing about detailed steps to extract water.

Comment by Andrew W — September 5, 2011 @ 3:34 pm

The link I refer to above is actually a pretty good refutation of Dr Spudis’ claim that the Moon is easier to mine than asteroids, it can’t be the link he intended. So, expecting him to change it for the link he intended, here it is: http://www.scienceclarified.com/scitech/Comets-and-Asteroids/How-Humans-Will-Mine-Asteroids-and-Comets.html

Comment by Andrew W — September 5, 2011 @ 3:43 pm

Comment by Marcel F. Williams — September 5, 2011 @ 2:31 pm
“@James Fincannon”

Hi Marcel,

Actually that was me, not Mr. Fincannon.

“Small asteroids that are 100 to 1000 tonnes in mass should be way less than 10 meters in diameter. So it shouldn’t be too difficult to capture them within rotating containers with lengths and diameters that are nearly 10 meters designed to match the rotation of the intended asteroid and stopping the asteroid’s rotation once it is captured. Asteroids that size should also be easy to process within structures deployed at L4 or L5 by heavy lift vehicles from Earth.”

I am not trying to give you (or anyone else) a hard time, but there are a number of scenarios for dealing with potential asteroid mining being discussed and what they (to me at least) all seem to have in common is a need to negate the asteroids ‘wobbling’ rotation and stabilize it. I was therefore restricting my questions to that issue, to see what ideas were put forward to achieve that task.

While the 100 to 1000 tonne asteroids may be small in volume that is still a mass of 220,000 to 2,200,000 lbs. that has to be captured and de-spun. Again I am not saying that it cannot be done, but the ‘containers (especially if the mission is to be totally automated) would have to be very sophisticated and have a lot of delta-v for all of the reaction control thrusters.

Still seems to me this would be something better attempted after achieving the increased capabilities made possible by lunar resources. As I have mentioned (probably to many times) I started out (a long time ago) an’ Asteroid first’ advocate, but as I worked on actual operations requirements became a’ Moon first’ advocate. My last holdout position was the availability on the asteroids of certain resources that were not available on the Moon (mainly Water, Carbon and Nitrogen). With the discovery that all those exist in abundance on the Moon, I am even more convinced ‘Moon first’ is the way to go.

Please not I said ‘Moon first’ not ‘Moon only’, the time for use of Asteroid resources will certainly come.

Comment by Joe — September 5, 2011 @ 4:00 pm

The link I refer to above is actually a pretty good refutation of Dr Spudis’ claim that the Moon is easier to mine than asteroids, it can’t be the link he intended.

No, it is the link I intended. It was not to substantiate the “many steps” to process water — that’s my contention and I outline it in the words that follow the reference. I simply linked it to provide a general reference on mining asteroids. In fact, there is much in that article that airily glosses over the difficulties of using NEOs for resources. For example, it mentions melting ice for water and contends that we can get those from NEOs. Some of it is simply wrong — no NEO shows any evidence for water ice. In fact, ice in any asteroid has only been recently found and it is in main-belt object, inaccessible to human missions (at least for the foreseeable future). My statements about having to break down clays and other water-bearing minerals is correct.

Comment by Paul D. Spudis — September 5, 2011 @ 4:01 pm

Agreed 100% on the Moon vs. near-Earth asteroids. For manned exploration I would ideally like to see the Moon first, followed by a destination like 24 Themis (200 km diameter, lots of ice water, same orbital plane as the planets), or cloudtops of Venus / surface of Mars. If we have truly become a spacefaring civilization by then though there’s no reason we couldn’t do all three.

One other obvious reason for the Moon first: other countries are focusing there anyway, and such countries (China/Japan/India/etc.) are at the level that they would be able to assist with Moon exploration but not likely to be as much of a help in more difficult locations.

Comment by Mithridates — September 5, 2011 @ 5:53 pm

At 1AU from the Sun any ice on the surface of an NEO would soon sublimate, so ice is unlikely to be detectable on such bodies, however the lunar soil temperature one meter below the surface is around -20C, so any ice deposits at that depth or deeper within NEO’s would likely be at a similar temperature and stable. We know of a couple of asteroids in the main belt with surface ice, so I think it likely that some NEO’s have significant ice content. In fact, in all likelihood some NEO’s will be of cometary origin.

Comment by Andrew W — September 7, 2011 @ 9:02 pm

any ice deposits at that depth or deeper within NEO’s would likely be at a similar temperature and stable.

The difference between a NEO and the Moon is that the asteroids have undergone a complex fragmentation history, ranging from minor disruption at impact antipodes to complete disaggregation and re-assembly in some cases. The only “ice” in them is primordial – there is no process to deposit water on their surfaces as occurs on the Moon. So any ice in a NEO must be original solar nebula, it must have survived 4.5 billion years of cratering and impact disruption, and subsequently remained undisturbed beneath a thermally insulating layer of regolith, all this on bodies orbiting the Sun within a couple AU. I find such a scenario highly unlikely.

Comment by Paul D. Spudis — September 8, 2011 @ 4:15 am

“The difference between a NEO and the Moon is that the asteroids have undergone a complex fragmentation history, ranging from minor disruption at impact antipodes to complete disaggregation and re-assembly in some cases. The only “ice” in them is primordial – there is no process to deposit water on their surfaces as occurs on the Moon. So any ice in a NEO must be original solar nebula, it must have survived 4.5 billion years of cratering and impact disruption, and subsequently remained undisturbed beneath a thermally insulating layer of regolith, all this on bodies orbiting the Sun within a couple AU. I find such a scenario highly unlikely.”

Probably few NEOs have been NEOs for more than billion year.

“There are many physical mechanisms that can limit the dynamical lifetime of a comet (or in other words the period of time the comet is active). In fact, the typical dynamical lifetime of a comet is about 1/2 million years. After this period, the comet is no longer active, and becomes a dead comet.
…
Today, there is an increasing evidence that there might be a significant population of dead comets occupying Halley Type orbits. In fact, many asteroids have orbits that can’t be distinguished from the orbits of some comets, as the graph below shows. Furthermore, scientists think that perhaps half of the near-Earth asteroids may be “dead” comets.”
http://spaceguard.rm.iasf.cnr.it/NScience/neo/neo-what/com-life.htm

“NEAs survive in their orbits for just a few million years. They are eventually eliminated by orbital decay causing collision with the Sun or planets, or ejection from the solar system by close approaches with the planets. With orbital lifetimes short compared to the age of the solar system, new asteroids must be constantly moved into near-Earth orbits to explain the observed asteroids. The accepted origin of these asteroids is that main belt asteroids are moved into the inner solar system through orbital resonances with Jupiter. The interaction with Jupiter through the resonance perturbs the asteroid’s orbit and it comes into the inner solar system.”
http://en.wikipedia.org/wiki/Near-Earth_object#Near-Earth_asteroids

Comment by gbaikie — September 8, 2011 @ 5:16 am

Probably few NEOs have been NEOs for more than billion year.

The duration of a NEO lifetime is not well known, but they’ve been asteroids for the duration of the age of the Solar System. Lots of opportunities for collision, fragmentation and loss of primordial water.

Comment by Paul D. Spudis — September 8, 2011 @ 9:14 am

I am a member of a NEO community, so I can clarify some disputes here mentioned (data hereby mentioned is fresh from the latest planetary defense conference, which I attended this May):
1. Dynamical lifetime of a NEO is on the order of 10 Ma.
2. Almost all NEOs are rubble piles: solid bodies are easily broken by collision. Most of the mass reaggregates into a rubble pile, which is afterwards robust against further collisions – the rubble dumpens the hits.
3. Rubble piles are vulnerable to YORP effect and undergo frequent fissions due to this effect, perhaps every few hundred ka. Each fission is a total disruption and reaggregation, which sheds few percents of the mass and makes a binary (15% of NEOs), which lasts about 1 Ma before being separated by an encounter with a terrestrial planet.
4. Many NEOs have ventured close to the Sun at some point and have experienced very high temperatures. Throughout the diameter, since most of them are rather small. Only some dormant comets may contain water, but there are very few of them – comets smaller than 3 km swiftly desintegrate when exposed to intense sunlight.
5.The astrodynamical issues over asteroid capturing will be discussed later this month in a workshop on Caltech University.

Question to Dr. Spudis: If I show you here that a visit to one particular NEA can lower the cost of reaching the Moon by 90% in every subsequent mission, would that be enough to you to do the unthinkable – change your opinion on NEO 1st/Moon 1st debate ?

Comment by Zoran M. Ilitz — September 8, 2011 @ 12:26 pm

Question to Dr. Spudis: If I show you here that a visit to one particular NEA can lower the cost of reaching the Moon by 90% in every subsequent mission, would that be enough to you to do the unthinkable – change your opinion on NEO 1st/Moon 1st debate ?

I change my mind a lot, so it’s not “unthinkable.” Post a link to your study.

Comment by Paul D. Spudis — September 8, 2011 @ 2:04 pm

Comets seem to have interior water which is “erupted” as they get nearer to the Sun. Rather then just having water at surface.
To have water vent from a comet from the interior seems to indicate the water is water ice rather than hydrates. As it requires little increase in interior temperature to cause this to occur.
It seems to me that a dead comet could be “dead” relative to it’s orbital distance from the sun- if has more interior heating it could result in water erupting from it.

Comment by gbaikie — September 8, 2011 @ 2:10 pm

Dormant or extinct comets may be among the NEO population, but they certainly are not predominant. Their non-volatile make up should be C1 chondrite, which make up only about 7% of recovered falls. And even if these are extinct comets, there is no assurance that they contain free water; the recovered C1 chondrites all have their water within chemically bound minerals.

Comment by Paul D. Spudis — September 8, 2011 @ 2:41 pm

“Post the link to your study.”

I was told that the paper would be out in mid-september, but the abstract can be found on the conference web site if you google ‘Ilitz 2006 WB Einstein’. The idea is to retrieve a boulder from 2006 WB in Nov 2024, which appears to be feasible. Once you have a massive boulder (600 tons minimum, 10,000 tons budgeted), you can propellantlessly sling ships away from it with tethers (as a hammer), all the way to the Mars or Moon (NASA has studied the issue a decade ago). Enabling factor is the large ballast mass. If provided, the launching station will be able to throw ships away over and over again, while loosing very little of its own momentum in the process. (MV = – mv)

The astrodynamics of capturing are tricky, however, and I hope that the workshop in Caltech at the end of this month will sort out the feasibility of this.

Comment by Zoran M. Ilitz — September 9, 2011 @ 5:13 pm

(Looking up orbital elements 2006 WB…)

e = .18
a = .85

I get a Vinf of around 3 km/sec. Depending on how massive this boulder is, it would take a substantial momentum change to park it.

Comment by Hop David — September 9, 2011 @ 8:52 pm

“there is no assurance that they contain free water;”

Brin’s model of cometary evolution suggests an insulating mantle can accumulate after repeated outgassings, if the perihelion’s not too close to the sun. Thus some extinct comets might have volatile ices preserved within an insulating exterior.

Comment by Hop David — September 9, 2011 @ 8:56 pm

“I was told that the paper would be out in mid-september, but the abstract can be found on the conference web site if you google ‘Ilitz 2006 WB Einstein’.”

So, go to a space rock, get a smaller rock which could be on that rock, bring back smaller rock.

You want to use a sling. Why not use dynamite? Or maybe something better. But a stick of dynamite seems as good or better than a sling. Or if I had to choose between a box a dynamite and lots of rope, I would pick dynamite to move a rock.
So I like getting little rocks from a bigger rock. It’s a easier way to find little rocks. Or maybe dirt if you bring a container or something make dirt into object that sticks together.
Though not sure this 2006 WB has smaller rocks or how many to select from.

Now assume we get a small to Cislunar. Not sure how this would help getting to the Moon. How is a rock better then a spent rocket stage or dead satellite in graveyard of GEO?

One answer is it more massive:
“Once you have a massive boulder (600 tons minimum, 10,000 tons budgeted)”

But what the total tonnage in graveyard?
“Although most GEO satellite operators have not taken advantage of removing their old spacecraft, there are over 100 already there. This number will continue to grow, because some 20 GEO birds expire each year, and some of these will be sent to the graveyard”
http://www.spacedaily.com/reports/The_GEO_Graveyard_May_Not_Be_Permanent_999.html
So probably more than 100 tons- maybe not 600 tons

How millions of dollars is a ton of scrap or rock worth in cislunar space. If a million per tons 600 ton is 600 million dollars and 10,000 tons is 10 billion

Comment by gbaikie — September 9, 2011 @ 9:38 pm

1. One needs <10 m/s (depending on when you start) to cross 2.3 LDs gap between 2006 WB and the Moon. Gravity assistance by Moon trims the remaining 3.68 km/s (can trim upto 5 km/s). On the day of the encounter, the Moon is in a once in a decade favorable position for this maneuver (on ecliptic, on node and on equator). This is one of the 12 reasons why 2006 WB. Of initial 10 m/s, up to 8 m/s would be provided propellantlessly by a sling.

2. Almost all NEAs are rubble piles (find a close up image of Itokawa to get a picture) – it is almost certain to find a suitable boulder on a pile of rocks. 2006 WB is 70 to 130 m in diameter.

3. The intention of using a sling is that you have to launch a selected boulder only – precisely on a trajectory to Moon, and with a precisely determined velocity. By using a sling we can do this slowly (within a few hours), using a simple fishing rod and a motor to power it (1 kW). Only 3 kWh of energy is enough. The boulder would be fetched by a lasso, and then pulled into orbital speed (few cm/s). Once in orbit, we simply add angular momentum until desired speed is reached, then release in the desired direction. Upon release the NEA would move in the opposite direction. This is very effective method of planetary defense, comparable to nuclear – the dynamite is not nearly enough.
In every aspect, there is nothing better than a sling.

4. The optimal final orbit is intended to be highly elliptical equatorial one, with perigee near LEO, and apogee below the orbit of geostationary satellites, in order for not to interfere with them.

5. Sling on a captured boulder (envisioned as a launching station) can throw ships by gradually adding momentum over a few days. Upto 3 km/s relative to station can be achieved with current materials. Upon release change of stations velocity is
V = 3,000 m/s * (mass of spacecraft/mass of station) ~ few m/s.

Such kick from an elliptical orbit is enough to go to Mars or Moon. If safety factors are reduced severely, even to Jupiter.

Since you need no propellant to do this, the price of space travel to anywhere would hence drop by 80 to 90%. The station would be able to serve for several decades, launching weekly.

6. The problem for collecting defunct sats for this purpose is that these objects are private property with classified content.

Comment by Zoran M. Ilitz — September 10, 2011 @ 9:47 am

To exploit the asteroid’s perigee momentum, the asteroid’s perigee would have to be at the right place and time during a launch window. It seems to me this would be a rare occurrence.

Comment by Hop David — September 10, 2011 @ 3:15 pm

The tether anchored to this asteroid would impart substantial momentum changes. Have you investigated Moravec’s tether equations to see if a tether of plausible materials could take the stress?

Momentum exchange tethers are interesting. If a tether makes super orbital catches as well as suborbital catches, momentum losses can be balanced with momentum gains and the orbit can be preserved. If we’re importing propellant from the moon, that would provide the needed super orbital catches.

Comment by Hop David — September 10, 2011 @ 3:25 pm

1. The best material for this purpose is M5. It has been studied.

2. Hoytethers would be used to prevent severing by micrometeors.

3. I am not talking about momentum exchange tethers which use catching from suborbital/superorbital flights. This is still, IMHO, problematic from the dynamic point of view. Instead, we would have a station which looks like a wheel. S/C docks with it slowly, as on ISS, and is then tethered to a winch on the outer rim. The winch can rotate all the way around and reel out the tether as it does. The spacecraft would be spiralled away within a few days and finally released when the station is in perigee.
This way, the stress is controllable and always within limits.
This approach is not as effective as catching, but is feasible and very safe.

Momentum losses are on the order of 1 m/s per launch (almost negligible, considering that the station would have initial access of momentum on the order of few km/s). The losses can also be balanced by electrodynamic momentum exchange tethers, where an electrical current in the tether pushes the station against the magnetic field of the Earth. This is very effective propulsion, and needs no propellant.

3. As a bonus, space station of this type would have the benefits of the variable artificial gravity (again by pushing against the asteroid). No more problems with microgravity, and loss of time for exercising. Instead, we can study the living conditions on lunar or martian type of gravity, which was impossible thus far.

4. Torroidal shape of the station would (hopefully) allow for creation of sufficient torroidal magnetic field which would protect against the radiation during passages through the Van Allen Belts. Alternatively, it can be shielded with material from the captured asteroid.

Comment by Zoran M. Ilitz — September 10, 2011 @ 5:15 pm

With a perigee in LEO and an apogee just below GEO, perigee velocity would be about 10.1 km/sec. For an S/C in LEO to dock with it slowly, it’d need to match velocities which would take about 2.4 km/sec from LEO.

I like the notion of a tether releasing from a body traveling 10.1 km/sec. That way less velocity suffices for injection to various orbits. With less velocity, less angular velocity and/or tether radius is needed and the stress on the tether is less.

However I still have reservations about the asteroid/tether perigee being in the right place at the right time.

A ship fully stocked with propellant at EML1 or EML2 covers 360 degrees of longitude each 28 days. Thus by dropping from these locations at the correct time, your perigee will be at the correct longitude when a launch window occurs. Further, from these high locations, plane changes are very cheap. Thus we’d have some control over the location and direction of the perigee velocity vector when a launch window occurs.

It is hard for me to imagine having this flexibility with an asteroid/tether.

Comment by Hop David — September 11, 2011 @ 12:39 pm

10.1 km/s + 3 km/s (added by tether) gives a C3 of 46 km2/s2. Mars and Moon require a C3 of about 15 (if I am not mistaking). Hence, we don’t really have to launch from perigee – the window is wider. This would cover a span of longitudes. Additionally, we may launch from perigee, but from different phase position of the tethered spacecraft, which is completely adjustable degree of freedom. Addition of velocities provides some longitude change.

The station would also have the ability to launch into any inclination relative to its plane of orbit, simply by reorienting its inclination against the asteroid. This can also be exploited.

Previous 2 options yield a 120 degrees longitude span for trips to Moon or Mars with options for plane changes (back of the envelope calculation – please check). It is fairly wide, I think.

If this is still not enough, there is also an option of having more than one station in various position – the spacecraft would be launched from the most suitable one for its destination and launch window combination. (There is likely more than one boulder available on 2006 WB for retrieval.) Considering the above, 2 or 3 of them would suffice. Besides, having a backup is always good.
One would cost as much as aircraft carrier. Affordable, I think.

Asteroid/tether station still has the advantage of variable artificial gravity – no other location posses the same. Besides, the ISS would expire by 2028 and would need a replacement with something preferably more advanced. The asteroid will be available from Nov 2024 (if captured). Very convenient for transition, I think.

2.4 km/s from LEO can be covered propellantlessly by electrodynamic momentum exchange tethers (which can also be used to reboost the station on asteroid). These are reasonably fast.

At later time the catching scenario would probably be revisited. (It is easier to do so when you already have a facility built that you can play with, so it has a potential to success, although I am still sceptical about it.)

Bottom line is the price of various options. It needs to be studied.

Comment by Zoran M. Ilitz — September 12, 2011 @ 7:54 am

Paul,

Thank you for three very interesting articles.

I agree that the moon is the more interesting scientific destination and likely to be a more valuable economic destination than a remote asteroid.

That said, there are possible reasons for a mission to even a small asteroid that you did not mention. It would be valuable to develop and to test technologies to alter the orbit or an asteroid. That mission might be more likely to be successful if astronauts were involved and would be likely to receive public support. Any mission to spend billions to collect rocks and dust from a small asteroid, which could be done more cheaply with a robotic vehicle, would be likely to attract derision not support.

For an asteroid mission brief exposure to dust is unlikely to be an issue. For a longer term presence on the moon it would be an issue that has to be managed. How difficult do you believe it will be to manage? Learning how to manage abrasive dust is one reason for an extened moon mission.

You make a convincing case that the moon is a higher value destination for a progam of both science and economic development missions.

Comment by Maurice Glover — September 22, 2011 @ 6:57 pm

Maurice,

Thanks for your kind remarks. In regard to two of your points:

It would be valuable to develop and to test technologies to alter the orbit or an asteroid. That mission might be more likely to be successful if astronauts were involved and would be likely to receive public support. Any mission to spend billions to collect rocks and dust from a small asteroid, which could be done more cheaply with a robotic vehicle, would be likely to attract derision not support.

The problem is that because of orbital mechanics, humans missions to a NEO will always have short loiter times, on the order of a few days to a week. That will make it extremely difficult to undertake any study that requires protracted access and capability.

For an asteroid mission brief exposure to dust is unlikely to be an issue. For a longer term presence on the moon it would be an issue that has to be managed. How difficult do you believe it will be to manage? Learning how to manage abrasive dust is one reason for an extened moon mission.

We already know how to handle the dust issue on the Moon. We don’t even know enough about the nature of the dust issue on asteroids to design mitigation strategies for it.

Comment by Paul D. Spudis — September 23, 2011 @ 6:14 am