Author Topic: Ease of Access to NEO's?  (Read 9228 times)

Offline Darkseraph

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Ease of Access to NEO's?
« on: 09/22/2014 12:30 PM »
I've heard a lot of press releases, websites and reports say: Some NEO's are more accessible than the MOON!!

But I've been wondering that that actually means. I assume they mean Delta V to match the orbit of the NEO. But I'm not sure if they're making a comparison with how much energy it take for a spacecraft to orbit the Moon, or whether they mean to land on the Moon, and take off again. Also, they say "some" which is a quantity above 0% and below 100%...but not more specific than that. What percentage of these NEO's are in orbits that are more accessible than either lunar orbit or landing? Are the characteristics of those easier to access NEO's particualry interesting to us in terms of resources, science and so on?

Mission to the Moon can be done in just over a week round trip. I don't know of any NEO that can be reached in that time. Is Delta V the only interesting measure of ease of access?


*just realized the apostrophe in the title was completely pointless. Think some cosmic rays caused a wrong neuron to fire in brain when i was typing.
« Last Edit: 09/22/2014 12:34 PM by Darkseraph »
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Offline QuantumG

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Re: Ease of Access to NEO's?
« Reply #1 on: 09/22/2014 12:34 PM »
They mean delta-v to the surface of the Moon compared to the delta-v to a near-Earth asteroid. Both prospecting on the Moon and time to retrieve material are easier and faster. However, it's typically accepted that asteroids will have much more interesting ores - even if you're planning on mining asteroidal materials deposited on the Moon, impacts are less likely to be as rich.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline JasonAW3

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Re: Ease of Access to NEO's?
« Reply #2 on: 09/22/2014 01:06 PM »
In some cases, I think they are referring to the NEOs that dip below Geosync orbit.  As I understand it, it takes as much Delta Vee to reach GEO as it does to get to the moon.

     While rendevousing with said NEO might not take alot of Delta Vee, matching velocities may be an entirely different kettle of fish...
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Offline Darkseraph

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Re: Ease of Access to NEO's?
« Reply #3 on: 09/22/2014 04:35 PM »
Okay, taking it that they mean delta V for a moon landing and return as their comparision...


And even if some NEOs have more interesting materials than the Moon...

What percentage of NEOs are actually more accessible than the lunar surface in DeltaV? Are which of them in those accessible orbits are large enough to be a viable source of material?

I've done a good few web searches of this, can't find any clear answers...
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Offline Proponent

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Re: Ease of Access to NEO's?
« Reply #4 on: 09/22/2014 06:23 PM »
Have a look at arxiv.org.  Attached are three papers I found there.

P.S.  The last attachment is "Easily-Retrievable NEOs" by Sánchez, Yárnoz & McInnes.  I don't know why the file name does not appear in the link.
« Last Edit: 11/08/2014 08:32 AM by Proponent »

Offline Robotbeat

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Re: Ease of Access to NEO's?
« Reply #5 on: 09/24/2014 12:51 PM »
Okay, taking it that they mean delta V for a moon landing and return as their comparision...


And even if some NEOs have more interesting materials than the Moon...

What percentage of NEOs are actually more accessible than the lunar surface in DeltaV? Are which of them in those accessible orbits are large enough to be a viable source of material?

I've done a good few web searches of this, can't find any clear answers...
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Offline Nilof

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Re: Ease of Access to NEO's?
« Reply #6 on: 09/24/2014 11:26 PM »
Capturing an asteroid into a lunar retrograde orbit requires far less delta-v than lifting the same ammount of material to the same orbit from the lunar surface, because you use repeated gravity assists for the capture. Getting the capture spacecraft to the asteroid has a lower delta-v cost too.

To give you a reference, the NASA asteroid capture mission will use a Delta-IV launched spacecraft (~20 tons fully fueled) and could retrieve NEO's weighing 1000 tons using only the reaction mass it launched with. That is a very large ammount of materials in lunar orbit for a very small ammount of mass to LEO. A stony-type asteroid is likely to be processable to 250 tons of LOX at a minimum, and better asteroids will likely be processable into more easily stored reaction mass such as water which could be used as SEP fuel.

So you could use a small SEP vehicle to retrieve a small asteroid(possibly a boulder from a larger one), use that to demonstrate ISRU, and use the results of that to fill up larger SEP capture vehicles with reaction mass. If your maximum capturable asteroid size increases by a factor of ten after each capture, you fairly quickly get to the point where you can capture ridiculously big NEO's like this one into a convenient orbit.

The advantage to the whole thing is that you can start small and get a decent ammount of propellant out of it. The disadvantage is that capturing asteroids takes a lot of time.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline QuantumG

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Re: Ease of Access to NEO's?
« Reply #7 on: 09/24/2014 11:36 PM »
To give you a reference, the NASA asteroid capture mission will use a Delta-IV launched spacecraft (~20 tons fully fueled) and could retrieve NEO's weighing 1000 tons using only the reaction mass it launched with. That is a very large ammount of materials in lunar orbit for a very small ammount of mass to LEO.

Love to see your math on that. (BTW, it's "amount".)

The other important figures of merit are: mission duration, repeatability, development cost, mission cost, etc.

For example, if a reusable lunar lander can carry 10 tons from the surface to lunar orbit every day, then your NEO mission better take less than 100 days, and that's pretty unlikely if you're planning on using SEP.

I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline Nilof

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Re: Ease of Access to NEO's?
« Reply #8 on: 09/25/2014 12:35 AM »
Love to see your math on that. (BTW, it's "amount".)

The other important figures of merit are: mission duration, repeatability, development cost, mission cost, etc.

For example, if a reusable lunar lander can carry 10 tons from the surface to lunar orbit every day, then your NEO mission better take less than 100 days, and that's pretty unlikely if you're planning on using SEP.

I was rounding off the numbers from the Keck report. It assumes 18.8 tons to LEO launched on an Atlas, to capture a "typical" 1300 ton NEO.

Lunar mining definitely has the advantage of being possible to scale up, but that requires a significant budget. Your lunar lander needs refueling, and even with oxidizer ISRU, the amount of mass you can put up into orbit is never going to be more than ~5 times the fuel mass you have to import from Earth. Asteroid mining gives a much larger mass multiplier than lunar mining with a chemical lander.

If you are considering using lunar hydrogen from polar craters, that implies a substantial scaleup of lunar activities. To begin with, it'll have to start with several exploration missions in a very challenging environment(no sunlight). So either you need the political will to develop a radioisotope rover to explore these craters, or you'll be limited to very short mission durations. While the rest of the moon allows for fairly easy prospecting, the interesting regions near the poles are notable more difficult. On the other hand, if you happened to have 250 tons of LOX already in lunar orbit from an asteroid capture, manned exploration missions would be quite a lot simpler...

Considering that small NEO retrieval is fairly near term and requires a smaller budget than an apollo-style moon landing, I see it as a logical stepping stone to a sustainable presence on the moon. An O'Neill style lunar mass driver would be a very nice thing to have but it requires landing large loads on the moon, and the cost of doing that could be greatly reduced with a prior infrastructure.
« Last Edit: 09/25/2014 12:36 AM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline QuantumG

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Re: Ease of Access to NEO's?
« Reply #9 on: 09/25/2014 12:54 AM »
That seems like a reasonable trade.

Thanks.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline gbaikie

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Re: Ease of Access to NEO's?
« Reply #10 on: 10/01/2014 09:57 AM »
Love to see your math on that. (BTW, it's "amount".)

The other important figures of merit are: mission duration, repeatability, development cost, mission cost, etc.

For example, if a reusable lunar lander can carry 10 tons from the surface to lunar orbit every day, then your NEO mission better take less than 100 days, and that's pretty unlikely if you're planning on using SEP.

I was rounding off the numbers from the Keck report. It assumes 18.8 tons to LEO launched on an Atlas, to capture a "typical" 1300 ton NEO.

Lunar mining definitely has the advantage of being possible to scale up, but that requires a significant budget. Your lunar lander needs refueling, and even with oxidizer ISRU, the amount of mass you can put up into orbit is never going to be more than ~5 times the fuel mass you have to import from Earth. Asteroid mining gives a much larger mass multiplier than lunar mining with a chemical lander.

If you are considering using lunar hydrogen from polar craters, that implies a substantial scaleup of lunar activities. To begin with, it'll have to start with several exploration missions in a very challenging environment(no sunlight). So either you need the political will to develop a radioisotope rover to explore these craters, or you'll be limited to very short mission durations. While the rest of the moon allows for fairly easy prospecting, the interesting regions near the poles are notable more difficult. On the other hand, if you happened to have 250 tons of LOX already in lunar orbit from an asteroid capture, manned exploration missions would be quite a lot simpler...

Considering that small NEO retrieval is fairly near term and requires a smaller budget than an apollo-style moon landing, I see it as a logical stepping stone to a sustainable presence on the moon. An O'Neill style lunar mass driver would be a very nice thing to have but it requires landing large loads on the moon, and the cost of doing that could be greatly reduced with a prior infrastructure.

So you saying it takes a 20 ton spacecraft to get 1000 tons of rock to lunar orbit [or LEO- I don't think  we want dusty rock on LEO, btw].
And you saying this require less spacecraft mass to lift 1000 tons of rock from the Moon.
No argument but I don't think it makes much sense to lift 1000 ton of lunar rock to Lunar orbit- unless it was a total of all the lunar samples which you intended to return to Earth.
But you saying one can get LOX from the rock. So a rock could have 40% mass being oxygen, but it seems one talking getting water from a carbonaceous asteroid and having this extracted water be the source of LOX.
So 20 ton spacecraft bring back 1000 ton rock and one can get 250 tons of water.  Or 20 ton spacecraft brings 1000 tons worth of water ore. Which again is not what I would think is a good thing to ship off the Moon [lifting damp lunar soil].
So with the Moon, one goes to location at lunar surface which within 1/2 km distance would be, say 1 million tons of water ore.
One could ask how much is 1000 ton of water ore at lunar orbit [or LEO] worth vs million tons of water ore on lunar surface?
It seems one difference, is we seem to be going in direction of establishing property rights for space rocks, and not doing this in regard to the Moon. So loosely speaking one say the million tons of water ore is worthless without property rights- unless one explores the Moon and keeps the results of exploration a secret and sells it as  information.
But anyhow what makes lunar water ore have value would be establishing of mining operation which one then may or may not have property rights in regard to it.
But dragging back a rock could have less problems in terms of who owns it, and therefore one could have the ability to sell it.
But question remains how much is the rock worth?
See, what the 20 ton spacecraft is doing, is not making water, but rather it's providing the rock a more favorable location- one still has mine it, which will require more than this 20 tons sent from Earth.

One could turn it around, and ask if someone had 1 billion or 10 billion to spend what kind of rock would they want to buy?
And they would want a rock in LEO for number of reason, and most obvious reason against that being it could a high cost liability if it damages other satellites. Another aspect is 100 tons of water or LOX is worth more at lunar orbit, than at LEO- assuming there is any demand for LOX or water near the Moon [going to Moon, or for use at GEO, or for going beyond Earth Moon system {ie, Mars}.
Or if what one mostly wants the 250 tons of water at Lunar orbit, how much does it cost to simply ship the 250 tons of water from Earth.
Or if one going to buy a rock in order to mine 250 tons water from the rock, spend more millions mining rock, how does it compare to shipping the 250 tons of water from Earth, instead?
Another aspect is one might *eventually* want 250 tons of water at lunar orbit, but you might not need much water in the nearest term. So maybe you want 50 tons in first couple of year then 100 tons [and 100 tons and more in the years after this]. So in terms of buying water ore, one want to buy some now, and have option to buy more later. Or one might only pay for water ore, once one has processed it into water- and so the whole purchase is future option [or how royalties are normally paid on Earth].
Because with water shipment from Earth, one also only pays when the water arrives and one can have as little water as one needs if shipped. Of course another option is simply shipping rocket fuel from Earth- or just LOX.

One advantage of shipping water is one is preparing for a business to process water from other sources other than from Earth. So your business model is to capture market for use of water for selling rocket fuel in space.
So you aren't going to mine water ore, you will buy water which has been distilled. So for that purpose, one might want only a small quantity of water shipped- say 5 tons. And you would demonstrate you can make rocket fuel from water in space. So with knowledge of someone getting rock which could be mine for water, one get 5 tons of water shipped from earth and you will show can use whatever water is mined in the future from the rock. But in any case, such a party is not going to pay more for water than the cost of it being shipped from Earth.

Now the advantage of mining water on the Moon is you can have more demand for water. Demand can include their stuff which can shipped off the Moon and send to Earth. People might want to come to the Moon and need water and need rocket fuel to leave the Moon. And largest demand could be exporting water and LOX to Cislunar space [same market available to the the space rock] and this includes any rocket fuel needed to get to the lunar surface.
Now anyone who wants to mine water on the Moon would start out as a buyer of rocket fuel at lunar orbit- so they could be buyers the water/rocket fuel made from space rock. And like the water buyer they don't care where it's coming from, they happy to buy rocket fuel shipped from earth if cheaper than from a rock. But they will want the amount they need when they need it.
And unless a lunar miner wanted a large operation [meaning there would be a large demand would could be met] I can't see them needed more than total 50 tons of rocket fuel at lunar orbit to land 50 tons of gear on the Moon. And unless the rocket fuel is hopeless cheap, once they start operation they would making their own rocket fuel, by shipping it to orbit.
And the need for the equipment to extract water could be far less than 50 tons. What could be more massive need is the power supply- landing acres of solar panels for use of splitting water and electrical power for other types of mining operations- though again depends expectation of amount market for electrical power.
If want some kind mass driver which would have a mass greater than say +50 tons, one would probably mine lunar iron for any need for the iron or steel for the mass driver [whatever type it is]. And one need iron for other mining operation including water mining. So bigger the scale, more likely it's more profitable to mine simpler components needed from the Moon.

But I generally think of lunar water mining starting out small scale, but if one is mining space rocks and providing cheap rocket fuel, this tend to drive lunar operations into larger scale. So tend to think in first few year one is only mining and making about 50 tons of rocket fuel per year, which within say 5 years is scaled up to 100 tons per year, and within decade or two 1000 of tons per year
And at 100 tons per year scale, one would have lunar water at about $500 per lb and LOX at $1000 per lb.
And shipped LOX in lunar orbit at about $3000 per lb. So if space rocks can from the start provide LOX at $3000 per lb, that be in range of it being hopeless cheap as far small scale lunar water mining at the beginning planning on competing with space rock water- though starting with out with large scale lunar mining may be a way to do it.

I tend to think only when there already a large market for water in high earth [or low earth] that one can profitable mine water for space rocks [one drag a 1 million ton rock into lunar orbit or Mars orbit]. And for small scale, I think PGM would better for space rocks. Though shielding for space stations and simply for use as gravitational masses could also have small scale market
« Last Edit: 10/01/2014 10:21 AM by gbaikie »

Offline A_M_Swallow

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Re: Ease of Access to NEO's?
« Reply #11 on: 11/08/2014 02:46 AM »
Shipping items from Earth to the Moon will cost an estimated $100,000 per kg (or $45,400 per lb).  So initially a Moon base will probably be willing to pay about $44,000 per lb of water.  Write the business plan around those two figures.

As time goes on people living on the Moon will want cheaper water.  The same applies to water products such as LOX and breathable oxygen.  There will have to be very big price reductions before merchants can afford to ship lunar water to LEO.

Offline ThereIWas3

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Re: Ease of Access to NEO's?
« Reply #12 on: 12/07/2014 03:26 AM »
Aren't most NEO asteroids in solar orbits, and moving at a pretty good Earth-relative speed as they go past?  Even if you could see them coming with enough time to get ready, then launch and match course and velocity with them, by the time you were done with whatever you wanted to do there you would find yourself a very long way from home.   And still moving away at solar-orbit speed.

So you wait to come around the sun again (in the meantime perhaps a year has gone by...) and are approaching the Earth again - now you have to slow down enough to get captured by the Earth/Moon gravity field and spiral back home.

This sounds very expensive in either delta-vee or in time, compared to just working on the surface of Luna, which isn't going anywhere.
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Offline Nilof

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Re: Ease of Access to NEO's?
« Reply #13 on: 12/09/2014 11:22 AM »
Aren't most NEO asteroids in solar orbits, and moving at a pretty good Earth-relative speed as they go past?  Even if you could see them coming with enough time to get ready, then launch and match course and velocity with them, by the time you were done with whatever you wanted to do there you would find yourself a very long way from home.   And still moving away at solar-orbit speed.

So you wait to come around the sun again (in the meantime perhaps a year has gone by...) and are approaching the Earth again - now you have to slow down enough to get captured by the Earth/Moon gravity field and spiral back home.

This sounds very expensive in either delta-vee or in time, compared to just working on the surface of Luna, which isn't going anywhere.

This is addressed in the Keck report that I linked earlier, with explicitly simulated trajectories and a table of times for already discovered candidates. The capture does take a few years, but a SEP spacecraft capturing an asteroid 50+ times it's own mass is demonstrably doable.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Hop_David

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Re: Ease of Access to NEO's?
« Reply #14 on: 01/07/2015 05:02 PM »
I've heard a lot of press releases, websites and reports say: Some NEO's are more accessible than the MOON!!

But I've been wondering that that actually means. I assume they mean Delta V to match the orbit of the NEO. But I'm not sure if they're making a comparison with how much energy it take for a spacecraft to orbit the Moon, or whether they mean to land on the Moon, and take off again. Also, they say "some" which is a quantity above 0% and below 100%...but not more specific than that. What percentage of these NEO's are in orbits that are more accessible than either lunar orbit or landing? Are the characteristics of those easier to access NEO's particualry interesting to us in terms of resources, science and so on?

Mission to the Moon can be done in just over a week round trip. I don't know of any NEO that can be reached in that time. Is Delta V the only interesting measure of ease of access?

An oft cited paper for NEO delta Vs is Shoemaker and Helin's 1978 paper. I went to the ASU library, copied their microfiche and transcribed the paper. PDF is attached.

They compare delta V with landing on an asteroid vs landing on the moon.

You are correct in your observation there's other metrics besides delta V. For their low delta Vs they assume a Hohmann like orbit and rendezvous with the asteroid at aphelion. Such launch windows are vanishingly rare as the authors acknowledge. Trip time is usually around 6 months for a one way trip.

Asteroid mining is something we have zero experience with. It is bound to be a trial and error process requiring multiple trips. If launch windows to an ore body are decades apart, acquiring experience would progress at a glacial pace.

They also assume high thrust impulsive burns (in other words burns with chemical rockets). So in some ways the paper doesn't apply to proposals for retrieval employing ion rockets and lunar swing bys
« Last Edit: 01/07/2015 05:06 PM by Hop_David »

Offline TrevorMonty

Re: Ease of Access to NEO's?
« Reply #15 on: 09/20/2017 09:29 AM »
Just read John s Lewis Asteriod mining 101. Good book, definitely must if interested in asteriod mining. One interesting point he had was about using asteriods as stepping stones for solar exploration. Fly to NEA from LEO, extract water for fuel while NEA travels to asteriod belt then jump off to a belt asteriod. Do same thing again to go further out or return with processed resources.

In distance future we could see people using this method to travel to belt and back. Have Oneil colonies attached to large NEAs and belt asteriods. Most of travel time which could be years, is in 1G low radiation habitat with occasion 0G spaceship short hop to next colony.
« Last Edit: 09/20/2017 09:35 AM by TrevorMonty »

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