Asteroid/Comet Resource Utilization

[oldAtlas_Eguy]

Let's see :
1. 10m sphere has a volume of (4/3)*pi*r^3 = 4188,79 m3 (approximately)
Assuming density of 2 kg/l, or 2 t/m3 = 8377,58 t

2. Abusing Tsiolkovsky's rocket equation, assuming ΔV = 3 km/s, Isp = 30 000 s and starting mass from above, gives
8377,58 t * e^( (-3000m/s) / (30 000s*9.81m/s2) ) = 8292,53 or difference approximately 85 t.

3. Assuming 250 $/kg this is worth 2 073 132 500 $.

4. Using SpaceX Falcon 9 to put 100t in GTO = 1 196 581 196,58 $

Adjust accordingly.

btw., i think that Zenit would be cheaper.

If you use the Falcon 9 rates the infrastructure launch costs makes it so that even processing 20 asteriods you will still loose money. Using the rates for a Falcon 9 Heavy and 30,000 ISP it is still marginal. Until launch rates get down to $2000 or less the cost of the infrastructure to process the material will cost so much that you cannot make money off of using asteriod material or even lunar mmaterial. The studies done by O'Neil in the 70's knew this as well.

 

[HopDavid]

Using engines with only 450 ISP will never be economical. That is why all of the economic studies for use of resources in space use electric propulsion with 10000 to 30000 or more ISP engines.

Electric propulsion thrust to mass is pretty anemic even with ordinary spacecraft. And you're going to push an 8000MT asteroid with ion drives? How long do think it would take to impart 3 km/sec delta V?

 

[oldAtlas_Eguy]

Using engines with only 450 ISP will never be economical. That is why all of the economic studies for use of resources in space use electric propulsion with 10000 to 30000 or more ISP engines.

Electric propulsion thrust to mass is pretty anemic even with ordinary spacecraft. And you're going to push an 8000MT asteroid with ion drives? How long do think it would take to impart 3 km/sec delta V?

209 days per 1km/sec delta v or 630 days total with a 10MW VASIMR or 45kgf.

 

[neutrino78x]

I still think non-rocket propulsion to LEO will help a lot. Like huge railguns or maglev catapults. It involves high acceleration, 60+ g, so it is for cargo only, but most of these methods use electricity rather than propellant, so in theory it should be cheaper.

--Brian

 

[neutrino78x]

Yes, the vehicle would obviously have a rocket to use once it is in space, to get in the desired orbit. I'm talking about flinging it into space, so it doesn't have to push out of the gravity well using rocket fuel.

--Brian

 

[oldAtlas_Eguy]

Here's a quick delta V map that HopDavid found:

I found it very useful. It makes delta V assessments and comparisons easy for proposed architectures, especially Earth Lunar ones, but can be used as guide on asteroids as well by using the delta V values for Demos which may be higher or lower depending on the actual asteroid involved.

An old electric propulsion method dating back the original O’Neil colony studies is the Rotary Pellet Launcher (RPL). An RPL with an arm length of 10 meters and RPM of 10,000 would have an ISP of about 1068. It is possible in a vacuum to get it to rotate faster, limited only by the power input, motor size and dynamic bearing resistance which increases when RPM increases. Maglev bearings could enable very high RPM’s. Computer Hard Disks spin at up to 10,000 RPM without MagLev bearings. The bearing lifetimes of hard disks are 5 years continuous use.

10,000 RPM at 6cm radius = 62 m/s rim speed

By increasing the radius in a vacuum to 60 cm you would get 620 m/sec tip speed. For one gram ejected per sec you would get:

1(g/sec)*620(m/s)/9.8(m/sec*sec) = 64g of force or ISP = 64

Disadvantages: 1) How to get the material released at the right point in the rotation. 2) Sand or pebbles instead of gas is being thrown out into space for someone else to run into. 3) Vibration and side force loads on the bearing. 4) Wear and equipment lifetimes

For getting the material to be released at the right point in the spin although difficult to solve is in the realm of existing engineering capability.

For an asteroid the chances of the sand being a menace to others is extremely small, most if not all will end up in the sun. For maneuvering closer to earth another propulsion method could be used.

By using a disk that continually or near continually throws out a stream of sand, vibration can be minimalized. Side force loads is dependent on the amount of material released per second. These two are also within the realm of current mechanical engineering.

Wear is a problem related to what type of material is used as propellant, the abrasiveness of it and the ability of the container to withstand the wear. The design should be one that is a tradeoff of wear time and expense/weight of the arm/disk being abraded.

 

[csmyth3025]

This is the only SDC thread that seems to fit my dilema. I need help!

In another discussion group (spacesettlers) there is an ongoing debate that Near Earth Asteroid mining is cheaper and, generally preferrable to the establishment of Lunar mining operations. The proponents of NEA mining quote a source that tells them that 4 meter diameter meteors strike the Eath's atmosphere on average about once per year. By this bit of information they surmise that there must be a dozen or more of these passing between the Earth and the Moon each year. They feel that these small asteroids can be easily "nudged" into a circular orbit approximating that of the ISS and that the ISS (with some additions and modifications) can process the material in these asteroids and fabricate these processed materials for space-based construction of other facilities in the pursuit of establishing a robust space imfrastructure.

To my mind there are several problems that they seem to gloss over. The seem to feel that we have the capability (or will have the capability) to find and track 4 meter diameter asteroids making close approaces to Earth so that we can rendevous with them. They seem to feel that we can launch a rocket (chemical or ion drive) with sufficient fuel to alter the orbit of a 100-200 meteric ton asteroid into a LEO similar to that of the ISS (some have suggested aerobraking in Earth's atmosphere). They seem to feel that we can do this with a variety of "found" NEA's on a regular basis.

My questions are these:

1) Do we (or will we ) have the capability to observe these small NEA's in a timely manner and project their orbits so we can plan a mission to rendevous with them in years (or, perhaps, months) - not decades?

2) Hopefully, one of the proponents of this plan will propose a known NEA candidate asteroid. If one is found, do we generally have accurate enough information to calculate the composition and mass of 4 meter diameter known NEA's?

3) If we have the requisite mass and orbital characteristics of the NEA, do we have computer programs (or other means) by which to determine the the mass of the fuel, the rocket or ion engine and "grappling" equipment that it will take to renedous with the NEA and then the amount of fuel it it will take to change it's existing orbit to an Earth-centric orbit at an altitude of about 375 KM?

My instinct is that the answer to these questions is "no". But I'm no expert on these things. I'm hoping that some of my fellow SDC forum members are more knowledgeable than me and can provide more than just a one-sylable instinctive response to these questions.

Chris

 

[Boris_Badenov]

This is the only SDC thread that seems to fit my dilema. I need help!



Chris

NEAR-EARTH ASTEROID DISCOVERY STATISTICS

 

[MeteorWayne]

This is the only SDC thread that seems to fit my dilema. I need help!

To my mind there are several problems that they seem to gloss over. The seem to feel that we have the capability (or will have the capability) to find and track 4 meter diameter asteroids making close approaces to Earth so that we can rendevous with them. They seem to feel that we can launch a rocket (chemical or ion drive) with sufficient fuel to alter the orbit of a 100-200 meteric ton asteroid into a LEO similar to that of the ISS (some have suggested aerobraking in Earth's atmosphere). They seem to feel that we can do this with a variety of "found" NEA's on a regular basis.

My questions are these:

1) Do we (or will we ) have the capability to observe these small NEA's in a timely manner and project their orbits so we can plan a mission to rendevous with them in years (or, perhaps, months) - not decades?

Larger ones, yes. Asteroids that small are not routinely discovered....in fact I know of none that small that have been.

2) Hopefully, one of the proponents of this plan will propose a known NEA candidate asteroid. If one is found, do we generally have accurate enough information to calculate the composition and mass of 4 meter diameter known NEA's?

Moot point, since we can't find them! Even for larger ones, we have almost no "accurate" information as to composition. We have meteorites that have landed on earth as samples, but none can be associated with a particular asteroid in space. We only have mass measurements for the handful we have flown by. For almost all asteroids, we don't even know the size, we only know how bright it is at a certain distance except for a few that are big enough and have come close enough to image by light or radar, or that have had occultations observed. For the rest, the size is then estimated based on assumed albedo from the brightness, and the estimate varies by a factor of more than 2. That means the volume then varies by a factor of more than 8. Meteorite samples vary in density by a factor of more than 4, so any mass estimate would vary by a factor of more than 32

3) If we have the requisite mass and orbital characteristics of the NEA, do we have computer programs (or other means) by which to determine the the mass of the fuel, the rocket or ion engine and "grappling" equipment that it will take to renedous with the NEA and then the amount of fuel it it will take to change it's existing orbit to an Earth-centric orbit at an altitude of about 375 KM?

We have the programs (in fact, the calculations aren't terribly difficult, you could do them by hand if you had to) but without the object's mass, it's an educated guess at best.

My instinct is that the answer to these questions is "no". But I'm no expert on these things. I'm hoping that some of my fellow SDC forum members are more knowledgeable than me and can provide more than just a one-sylable instinctive response to these questions.

Chris

Hope that helps.

Take a look at this thread for the size range of recent (Since Feb 09) newly discovered asteroids closely approaching earth:
viewtopic.php?f=12&t=4613

 

[Yuri_Armstrong]

For the asteroid mission why dont' we head out to Eros, or one of the larger asteroids? That may be more worthwhile than one only about 60-100 yards in diameter.

 

[HopDavid]

For the asteroid mission why dont' we head out to Eros, or one of the larger asteroids? That may be more worthwhile than one only about 60-100 yards in diameter.

Main belt asteroids generally have a semi major axis between 2 and 3.3 A.U. Trans asteroid insertion burn from LEO would be from 4.2 to 5.3 km/sec.

Most main belt asteroids have a healthy inclination. So you'd need to do a substantial plane change burn as well.

Once there, matching velocities with the asteroid will cost 4 to 5 km/sec.

Unless you can make in situ propellent from the asteroid, add another 4 to 5 km/sec for trans Earth insertion (the trip home).

So, from LEO, you're looking at a ~15 km/sec delta V budget.

One of the show stoppers for a Mars trip is protecting and providing life support for the astronauts during the 8 month journey.

Trip time (one way) for main belt asteroids would be 1 to 1.5 years.

 

[Space_pioneer]

Before we even attempt any mining, wouldn`t we have to find out a way which makes the mining effecient enough so that the reward from it is worth more money than actually getting there and building the spacesip? Otherwise, mining on other worlds is a useless practice, unless there is some extremely useful resource that can`t be found on earth or something like that.

 

[MeteorWayne]

For the asteroid mission why dont' we head out to Eros, or one of the larger asteroids? That may be more worthwhile than one only about 60-100 yards in diameter.

Main belt asteroids generally have a semi major axis between 2 and 3.3 A.U. Trans asteroid insertion burn from LEO would be from 4.2 to 5.3 km/sec.

Most main belt asteroids have a healthy inclination. So you'd need to do a substantial plane change burn as well.

Once there, matching velocities with the asteroid will cost 4 to 5 km/sec.

Unless you can make in situ propellent from the asteroid, add another 4 to 5 km/sec for trans Earth insertion (the trip home).

So, from LEO, you're looking at a ~15 km/sec delta V budget.

One of the show stoppers for a Mars trip is protecting and providing life support for the astronauts during the 8 month journey.

Trip time (one way) for main belt asteroids would be 1 to 1.5 years.

Well he was proposing using an NEA, AND placing it in earth orbit...

 

[MeteorWayne]

For the asteroid mission why dont' we head out to Eros, or one of the larger asteroids? That may be more worthwhile than one only about 60-100 yards in diameter.

The mass of Eros is 6.69 × 10^15 kg, so you ain't puttin' that in earth orbit

Also, the closest it comes to earth in the next century is 0.14 AU, at a relative velocity of 5.8 km/s.

MW

 

[Yuri_Armstrong]

Woah, woah, woah. Hold on there. I wasn't proposing we try to put an asteroid into our orbit. I was just curious about what it would take to explore a big asteroid like Eros. David has made quite a good case as to how this is not practical right now.

 

[MeteorWayne]

That's what csmyth3025 was proposing, but he was talking about a 4 meter sized asteroid

 

[HopDavid]

Woah, woah, woah. Hold on there. I wasn't proposing we try to put an asteroid into our orbit. I was just curious about what it would take to explore a big asteroid like Eros. David has made quite a good case as to how this is not practical right now.

My observations were for main belt asteroids. Meteor Wayne noted Eros is an NEA. Which is more plausible (or should I say less implausible) than a main belt asteroid.

Please accept my apologies.

 

[EarthlingX]

Moving smaller asteroid and then process it in one of Lagrangian points might be better and safer than LEO. There would also be less ΔV needed.

For human travel LEO to L-points is not that far.

 

[MeteorWayne]

Well, the earth-sun L1 and L2 are ~ 1.5 million km from earth (~ 4X the Lunar Distance), L3 is ~ 2 AU (and very unstable), L4 and L5 ~ 1 AU away.

Earth Moon L1 is ~ 0.83 LD, L2 1.17 LD, L4 and L5 ~ 1 LD.

 

[Boris_Badenov]

Well, the earth-sun L1 and L2 are ~ 1.5 million km from earth (~ 4X the Lunar Distance), L3 is ~ 2 AU (and very unstable), L4 and L5 ~ 1 AU away.

Earth Moon L1 is ~ 0.83 LD, L2 1.17 LD, L4 and L5 ~ 1 LD.

Bigelow has plans for an EML-1 station. Maybe that would be the best place to move captured asteroids to & begin utilizing them.

 

[EarthlingX]

Well, the earth-sun L1 and L2 are ~ 1.5 million km from earth (~ 4X the Lunar Distance), L3 is ~ 2 AU (and very unstable), L4 and L5 ~ 1 AU away.

Earth Moon L1 is ~ 0.83 LD, L2 1.17 LD, L4 and L5 ~ 1 LD.

Bigelow has plans for an EML-1 station. Maybe that would be the best place to move captured asteroids to & begin utilizing them.

My thought exactly.

 

[csmyth3025]

Thanks for all the info. The proposals that are being made in the spacesettlers forum are to "capture" a NEA for the purpose of mining, processing, and fabricating its usable materials in LEO (presumably by an expanded and reconfigured ISS) for use in constructing space colonies, etc.

The apparent basis for the perceived ease with which this can be done is the use of a "gravity tractor" as described in the Wikipedia article linked below and the B612 site (http://www.b612foundation.org/index.html) sponsored JPL study summary linked directly below that:

http://en.wikipedia.org/wiki/Gravity_tractor
http://www.b612foundation.org/papers/t-GT_summary.pdf

I think the folks who are proposing to alter a NEA orbit into a parking orbit in the vicinity of the ISS are confusing that task with the much less energy-intensive task of slightly nudging a potential Earth impacting NEA so that it misses the "keyhole" pass that it's projected to make on a future orbit - presumably several years or decades in the future.

Chris

 

[MeteorWayne]

Just some rough calcs, a 4 meter diameter asteroid (100 m^3) would have a mass of 10,000 kg (pure water ice), 20,000 kg (lighter carbonaceous chondrites), to 80,000 kg (for an iron).
MW

BTW, that's 11 to 88 US tons, for the metric challenged

 

[Valcan]

Just some rough calcs, a 4 meter diameter asteroid (100 m^3) would have a mass of 10,000 kg (pure water ice), 20,000 kg (lighter carbonaceous chondrites), to 80,000 kg (for an iron).
MW

Yea i just dont see moving large asteroids around anytime soon. If you wanted to mine it there would need to be a mining barge of somesort. Drop it off with either a entirely robotic crew or a SMALL human crew. Rotate the crews in and out like they do for oil rig crews. Year onsite year off.


Really we simply dont have enough power to move these things much,....well we could if we didnt mine irradiating them....

These are Mountains we are talking about they just happen to float in the nether.

 

[HopDavid]

Moving smaller asteroid and then process it in one of Lagrangian points might be better and safer than LEO. There would also be less ΔV needed.

For human travel LEO to L-points is not that far.

When I give delta V budgets from/to EML1, I use a burn deep in earth's gravity well to exploit the Oberth effect.

So I assume a 300 km altitude perigee.

If, for safety reasons, you want a perigee as high as EML1, you lose about 2 km/sec of the delta V savings.