NASA's OSIRIS-REx probe to space rock Bennu

GW Johnson · 2020-11-09 09:20:32

Bear in mind that a rubble pile will have little or no cohesion due to materials strength, especially if it is too small and too warm to have any ice to glue the pieces together. Only the micro-gee gravity provides any "cohesion". It doesn't take a lot of centrifugal force to overwhelm that gravitational "cohesion". Which is why they fly apart when they spin up too fast.

There may be a cavity in the middle, but you cannot directly pressurize that to create habitable space. It would blow apart like a bomb the first second your atmosphere gas got in there. To use that space as a radiation shelter, you must put a real pressure vessel in there, that you can pressurize. "Stick-built", you can do that, but it is quite inconvenient to do so.

GW

tahanson43206 · 2020-11-09 10:08:08

For GW Johnson re #26

Thank you for providing Tobin with guidance in the nozzle topic!

For Post #26, and ** this ** topic, thank you for adding to the discussion ... I agree that the interior cavity would need to be lined with a liner to hold pressure, and I would expect a balloon fabric would be suitable. However, if a space-faring community were interested in setting up safe zones here and there around the Solar System, Bennu would seem to provide a model for what might be done.

That said, I am intrigued by your closing line ...

"Stick-built", you can do that, but it is quite inconvenient to do so.

Would you be willing to develop that thought a bit? Imagine that a young person were to stumble across this forum, and this topic in particular. Can you suggest a course of action to make a shelter for humans inside one of these rubble piles?

I'm not sure what "inconvenient" means in this context << grin >>. Seems to me ** everything ** we are trying to do away from Earth is inconvenient.

(th)

tahanson43206 · 2020-11-09 10:13:13

This post is for anyone:

Given that Bennu appears to be a rubble pile that is at risk of colliding with the Earth, it would seem (to me at least) reasonable to collect the contents and move same to a location where the material can be prepared for sale to customers in space.

The mass of Bennu is known (I'm pretty sure). That mass can be collected in manageable quantities (Calliban's bag would seem the right tool) and moved gradually to a useful solar orbit.

Does someone have the time and energy and resources to work out what that would cost in today's monetary units?

The investment would (presumably) pay off multi-fold when the processed materials are delivered to customers.

Edit#1: For clarification ... Calliban's bag was originally offered as a way to corral an entire asteroid. I'm suggesting using multiple smaller bags to collect subsets of the rubble pile, until the entire collection has been corralled and set on its way to a useful solar orbit. This would be highly comparable to the US Western practice of gathering steers on the open range and taking them to market., except that in this case, Nature has kindly collected all this material into a (roughly) spherical corral. All the range hands (robotic of course) need to do is to lasso an individual steer and start it on it's way to the harvest site.

(th)

GW Johnson · 2020-11-09 17:13:38

Tahanson43206:

I'm just guessing, of course, but I'd hazard the guess that the best pressure vessel to put inside a hollow rubble-pile asteroid (like Bennu) would be an inflatable. Not the thick-walled, armored, and insulated designs like the Bigelow models with the hard cores, but simpler, so that it can be crumpled-up small and inserted through a very modest mine shaft like an inner tube.

Otherwise, you have to haul in a hardbody pressure shells plate by plate and frame section by frame section, and weld or bolt the thing together inside the cavity, piece-by-piece. That is "stick-built".

And by the way, the mineshaft into the asteroid will have to be reinforced in some way, as well. I suppose a hard tube could be inserted, and connected to whatever pressure shell is in the cavity.

These rubble-pile things are subject to sudden shifts of the pieces without warning, precisely because there is no cohesion other than trivial microgravity, and impacts randomly occur.

I'd also say any "bag" used to contain all or part of such a body for transport had better be a bag without any porosity at all. A "solid-wall" bag. A net will NOT do! The moment you pull on the bag, the pieces of the asteroid will sieve out through any porosity. ANY force you care to apply is far larger than microgravity "cohesion"!

Imagining what no material cohesion really means is quite hard, but you have to do it, to think up schemes that might actually work. These rubble piles are quite literally small pieces "flying in formation", but only because of gravity that is weaker than the push of a human hand.

GW

tahanson43206 · 2020-11-09 18:33:05

For GW Johnson re #29

Thank you for your reply regarding (possible) installation of a pressure holding membrane inside Bennu.

I like the idea of a solid tube for access from the outside to the interior of the rubble pile. A rocket body could serve that function. I'm thinking here of the Apollo second stage that served as an entire space station for a while, after the Apollo missions ended.

1973 WOULD SEE THE LAUNCH OF SKYLAB, WHICH INCLUDED THREE CREWED MISSIONS

Regarding bags to collect material from bennu ... kbd512 has been reminding the forum periodically, of progress made in recent years with carbon nanotubes and related structures. Here is a snippet from Google ...

Nanosheet - Wikipedia
https://en.wikipedia.org/wiki/Nanosheet
A nanosheet is a two-dimensional nanostructure with thickness in a scale ranging from 1 to 100 nm.. A typical example of a nanosheet is graphene, the thinnest two-dimensional material (0.34 nm) in the world. It consists of a single layer of carbon atoms with hexagonal lattices

Graphene would ** seem ** to be a good candidate for the wall of a bag for this material. It is porous in the sense that it can filter water, but anything larger than a water molecule is blocked, as I understand the advertised capabilities of the material.

Here's another Google snippet about use of Graphene to filter water:

Graphene sheets (perforated with miniature holes) are studied as a method of water filtration, because they are able to let water molecules pass but block the passage of contaminants and substances.
Graphene and water treatment: introduction and market ...
www.graphene-info.com/graphene-water-treatment
www.graphene-info.com/graphene-water-treatment

(th)

tahanson43206 · 2020-11-10 07:12:04

For GW Johnson re Bennu mining robot ...

There are three members of the forum who have contributed posts about rocket operation and design ....(that I remember ... there are surely others)

Yourself, kbd512 and clark ...

Calliban has posted on a variety of engineering subjects, including asteroid harvesting.

I'm hoping there might be interest in this forum to work up a preliminary design for a Bennu harvester.

The discussion about a bag made of material capable of retaining the fine material of which Bennu is composed led me to imagine a structure consisting of ribs holding fabric, that would slowly fold over a set of material on the Asteroid, and collect it for movement to a processing location such as Lunar L1.

816loDQcALL._AC_UL160_.jpg

The space navigation part of the project would include meeting Bennu and then relocating to Lunar L1.

The robotics component would include navigation around the asteroid (much as the NASA probe did), and then performing the material collection maneuver.

The finance and marketing component is a critical part of the project, and several members of the forum have shown an interest in that.

(th)

GW Johnson · 2020-11-10 09:29:50

Moving an asteroid from one orbit to another means you have to apply a force to accelerate it in the appropriate direction. How do you apply a force to a rubble pile with zero material cohesion, only "bound" by microgravity?

You could do this to a body with some cohesion, such as an ice-bearing body, or something actually solid (and unfractured). But not a loose pile of rubble.

For a rubble pile, the only force you could successfully apply without disrupting the asteroid is a body force like gravity. In other words, the only way to change the orbit of a rubble pile like Bennu is by the "gravity tractor". Sure will be hard to enter a desired orbit is cislunar space when the "gravity tractor" requires years of exposure to effect a rather modest velocity change.

Of course there is a slightly stronger body force you could add to gravity: electrostatic attraction. That was my poster paper at the 2009 asteroid defense meeting in Granada, Spain. But it still takes enormous exposure times to effect "significant" velocity changes. Those are quite small for asteroid defense.

It's one thing to deflect an Earth impact threat years ahead of the encounter with a velocity change of several 10's of cm/s, it's quite another thing indeed to move an asteroid to a desired orbit with a velocity change on the order of 10's of km/s. That's velocity changes that are many orders of magnitude larger.

GW

Last edited by GW Johnson (2020-11-10 09:30:55)

tahanson43206 · 2020-11-10 09:43:03

For GW Johnson re #32

Thank you for helping with this topic!

The mining robot I am proposing would collect 1 ton of material, and transfer that ton to Lunar L1

The idea of moving an asteroid with gravity is certainly interesting, and it would certainly work over several thousand years of steady pulling.

When I asked Google for the mass of Asteroid Bennu, it came up with

78 billion kg

That is 78,000,000,000 kg, or 78,000,000 tons

To move Bennu to Lunar L1 would require 78,000,000 trips, if the payload for each trip is one ton.;

A single robot could make more than one trip, and the payload could be increased.

The investment required to make that move is X. The value of the material is Y.

The investment is justified if Y is greater than X.

Edit#1: For reference, the total number of automobiles manufactured on Earth in 2019 approached 92,000,000.

92 million motor vehicles
Worldwide automobile production through 2019. In 2019, almost 92 million motor vehicles were produced worldwide. This figure translates into a decline of around 5 percent, compared with the previous year. China, Japan, and Germany were the largest producers of cars and commercial vehicles in 2019.
• Car production: Number of cars produced worldwide 2018 ...

(th)

GW Johnson · 2020-11-10 13:27:00

We don't yet know what those materials in a C-type asteroid really are. There is carbon there, but exactly what compounds those are is not yet known. If the material identity is unknown, then its value is as yet unknown, too.

The stony ones have pretty much the same minerals that we have in Earthly rocks, although the physical forms are not the same. Seemingly not just a whole lot of value there.

The metal ones seem to be a mixture of nickel and iron, contaminated perhaps with some rocky minerals. Those might be a source of really high-grade iron "ore".

I would think you would want to process any "ores" in-situ at the asteroid, then ship only the higher-value products home. But that means you have to do a melt and a separation, or some other refinement, in vacuum and in zero-gee. We do NOT yet know how to do that. Or even WHAT to do.

All in all, predicting revenues from asteroid mining is probably very, very premature. It would help if we had better ground truth information about these bodies, and if we had some experiences trying to conduct that kind of industrial processing in vacuum and zero gee.

GW

SpaceNut · 2020-11-10 17:43:35

With regards to making use of the empty space within the lose ruble pile is what might not be a regular round cavity but one that can and might be irregular shaped. The inflatables so far are very regular in that they have a thickness and general round shape. If inflation where to cause an out of round shape contact then it could break the asteriod apart. Another thing is movement while its somewhat isolated by the material thickness its still can see that force along a larger area of contact to the ruble pile and it still could force it appart.
To remove these we must encapsulate it before even attempting to do any thing else.

tahanson43206 · 2020-11-10 18:39:29

For SpaceNut re #35

Your point about the sensitivity of the material comprising the wall of the asteroid makes sense to me, to it would (perhaps) behoove the astronauts to try not to disturb the wall. They will have already done quite a bit of mischief by poking a hole from the surface into the interior.

I'd have to go back to be sure, but I ** think ** it was GW Johnson who described the asteroid as a myriad tiny objects "flying" in formation. If a fixed tube is poked into the wall of the "sphere", the movement of particles would be obstructed to some extent. Slow speed eddy's might appear in the wall of material.

Altogether, this would be an "other worldly" experience for an astronaut ? lucky ? enough to take part in an expedition.

(th)

tahanson43206 · 2020-11-10 18:55:54

For GW Johnson re value of material in Bennu ....

Bennu may contain atoms other than Carbon, but even if it were composed of nothing ** but ** Carbon, it would be immensely valuable to a community wanting to set up shop on the Moon.

***
I ran a quick check on the number of automobiles manufactured on Earth in 2019 ... Google came up with an estimate of 92,000,000.

It is entirely feasible for the people of Earth to make 78,000,000 asteroid mining robots in a year, if the incentive were present to do so.

Launching that many devices is not currently possible, but I expect the time will come when it will be.

Removing threatening asteroids or other objects by gnawing them to death seems (to me at least) a much better strategy than trying a gravity tractor for a thousand years.

(th)

GW Johnson · 2020-11-10 23:54:32

The gravity tractor is an asteroid defense option only when you have months to years warning. The velocity change needed to deflect one that far out is only cm/s. Fortunately enough, that's the magnitude of the effect you can get with the gravity tractor, on that long a timescale.

If you don't have that much warning, the only options are impactors and nukes. And they will almost invariably disrupt rubble-pile objects, which is what nobody wants to admit in public. And you'd better do it early enough that the cloud of debris you produce when you disrupt a rubble pile (the most common type) will have spread out larger than the Earth's diameter when it reaches the Earth. Otherwise, you made the problem even worse by converting a bullet strike (one region) to a shotgun blast (half the planet).

Mining asteroids is quite the different problem. Whatever it is that you bring home has to undergo enormous velocity changes to make the trip. Something like 4 or 5 orders of magnitude larger than the long lead time deflection for defense. That mining application is not (and will never be) a gravity tractor application. But, if it's a rubble pile body, you will have to fully contain it to move it at all, and it will arrive in fully broken-up condition. Your "bag" needs to be rather stout.

That mining stuff is quite distinct from a science/sample-gathering mission. Those bring back samples that are very small. They still have to undergo the same large velocity changes, so the gravity tractor could never serve for that. It's rocketry and electric propulsion that serve. And, you noticed (I hope) the sample is fully enclosed, precisely because it is all broken up into tiny pieces, if it came from a C-type asteroid or a comet.

The other thing to notice is that the sample recovered at Bennu was larger than the expected, precisely because the surface was so fragile. The probe went in deeper than they expected, and broke loose a shower of particles much bigger than they expected. It got jammed open by the multitude of pieces, so they lost some, before they could get it into the return capsule.

All that goes to support (not prove) what I said about these near-Earth C-type bodies. They are non-cohesive rubble piles. Almost like debris particles flying in formation, instead of solid bodies. The popular epithet "space rocks" is quite wrong about these objects! It applies to the far less numerous stony objects, and the rarer-still metallic objects. But not these.

The bigger ones much farther out in the outer solar system probably have some-to-lots of frozen volatile content, which would cement them together, sort of like concrete. Those really would be solid bodies resembling "space rocks". But not the near-Earth objects. Any volatiles in those volatilized long ago, if it was ever there in the first place. And we simply don't know that there ever was.

GW

Last edited by GW Johnson (2020-11-11 00:02:44)

tahanson43206 · 2020-11-11 06:37:42

For GW Johnson re #38

Thank you for your guidance! I'd like to focus on the middle section of your post, in an effort to see if there is the potential for a project this small group can tackle.

Mining asteroids is quite the different problem. Whatever it is that you bring home has to undergo enormous velocity changes to make the trip. Something like 4 or 5 orders of magnitude larger than the long lead time deflection for defense. That mining application is not (and will never be) a gravity tractor application. But, if it's a rubble pile body, you will have to fully contain it to move it at all, and it will arrive in fully broken-up condition. Your "bag" needs to be rather stout.
That mining stuff is quite distinct from a science/sample-gathering mission. Those bring back samples that are very small. They still have to undergo the same large velocity changes, so the gravity tractor could never serve for that. It's rocketry and electric propulsion that serve. And, you noticed (I hope) the sample is fully enclosed, precisely because it is all broken up into tiny pieces, if it came from a C-type asteroid or a comet.

If the entire asteroid consists of Carbon, that material would be valuable to a community setting up shop on the Moon.

Such a colony would also need large quantities of Nitrogen, and that can be harvested elsewhere in the Solar System.

In both cases, mining can (and I believe ** will ** be done) precisely the same way it is done on Earth. On Earth, truck loads of material are transported from the source location to locations where refinement and other processing is performed. In earlier posts in this topic, the space equivalent of trucks were introduced as a concept for removing material from a collection that threatens the Earth. On Earth, thousands of years ago, it was considered absurd to imagine removing a mountain, so it was recommended that humans go to the mountain. In the current age, and for quite some time, it is common practice to dis-assemble mountains and to transport desired material to other locations.

A space going dump truck will look different from an Earthly hauler, but the function will be exactly the same. I have proposed designing a one ton capable loose material transporter because the scope of the project is readily imaginable to ordinary persons. In the evolution of this undertaking, much larger transporters will be imagined, designed, built and deployed.

Every day, as part of my morning activities, I light up a screen that shows views of the Panama Canal locks on the Atlantic and Pacific sides. In the morning, both locks are busy as huge ocean going vessels enter the locks to make their passage throughout the daylight hours. Hundreds of years ago, only a person like Jules Verne could have imagined such massive vessels routinely traversing a waterway cut into the Isthmus of Panama.

Now, today, in the special circumstances of the NewMars forum, it is possible to imagine fleets of automated mining transporters collecting material from asteroids and transporting that material to locations where it would be useful. I'm hoping members of this forum (and new members with the appropriate education, experience and interests) will undertake development of ideas that would lead to deployment of such mining equipment.

We have a suitable NewMars project in early stages in RobertDyck's Large Ship topic. In that case, the opening gambit calls for transporting 1000 passengers in a single vessel. In this topic, the size of the vessel is smaller, but the mission is similar. It is to transport mass from one location in the Solar System to another, and to make a profit in the transaction.

(th)

GW Johnson · 2020-11-11 09:25:30

Tahanson43206:

We simply don't yet know what this stuff is. It has carbon in it, which is the interpretation of spectral data (according to the science journal reports), but no one knows what compounds that carbon is in. Not until the sample return missions (ours and Hayabusa2) get home. Just remember that ground truth has always differed from remote sensing, sometimes drastically, sometimes not so much.

If you have ever had the opportunity to look inside a fired composite propellant solid rocket motor, there is a high-carbon low-density residue in there that looks somewhat similar to the stuff in the photos of these C-type asteroids, and the couple of comets we have visited. The stuff I am talking about is crusty texture, very fragile, and full of voids. It is mostly amorphous carbon, but highly contaminated with other compounds. That description should sound quite similar to what we have seen so far at these asteroids.

As for mining, these asteroids are physically very far apart from each other, even in the main belt. Certainy the near Earth objects are "loners" flying through space. So you are faced with only two possibilities: (1) bring the entire body somewhere else in the solar system that is convenient for processing, or (2) process it for usable products in-situ. Option 1 involves moving potentially large masses with very large velocity changes. Option 2 involves (a) processes that we have no idea yet as to what they are, (b) processes operating in vacuum when we have very little experience with that (most of our stuff is high-pressure, not low), and (c) processes that must operate in zero-gee where the physics (and chemistry?) are different, when we have zero experience with that yet.

With that picture in mind, I think your one-ton mover idea is probably a short-range item to move one ton of material from the body to an adjacent processing factory, floating nearby in space, just far away enough to avoid a collision. That might be a practical thing to design with technologies and materials we already have in hand.

This is much more probably something we might be doing out in the main asteroid belt, and probably only on the larger bodies a few miles in dimension. Those are the ones big enough and cold enough to have frozen volatiles inside, buried under a fragile dessicated outer "crust". Those volatiles would be valuable for processing into air, water, and propellant.

But you ain't going to find such in tiny NEO's, and probably not Phobos either. Too small, too warm. Even the comets we have visited have turned out to have very little volatiles and mostly crusty solids. The tails seem to be more dusts than gases.

GW

Last edited by GW Johnson (2020-11-11 09:26:11)

tahanson43206 · 2020-11-11 12:46:56

For GW Johnson re #40

Thank you for your thoughtful (and helpful) reply!

I appreciate the (cautious to be sure) endorsement of an effort to design a rubble bagger robot. At this point, that is a starting point for creative thinking.

With that picture in mind, I think your one-ton mover idea is probably a short-range item to move one ton of material from the body to an adjacent processing factory, floating nearby in space, just far away enough to avoid a collision. That might be a practical thing to design with technologies and materials we already have in hand.

(th)

SpaceNut · 2020-11-11 13:20:50

Seems he mineral make up of the loss asteriod regolith is on hold until the scientists get the sample back.
Hopefully its a big haul and not a tiny little bit that makes its way back home safely.

tahanson43206 · 2020-11-13 13:23:24

This is an addition to the theme that Carbon would be highly valued by a community permanently settled on the Moon.

It is not yet known what percentage of Bennu is Carbon, but here is a report (courtesy of Google) about the amount of Carbon in soil on Earth:

58%
About 58% of the mass of organic matter exists as carbon. We can estimate the percentage of SOM from the SOC% using the conversion factor 1.72 (derived from 100/58). This conversion factor can vary in different soils, but 1.72 provides a reasonable estimate of SOM for most purposes.Sep 10, 2020
What is soil organic carbon? | Agriculture and Food

The mass of Bennu is estimated to be about 78,000,000 tons.

The mass of the Moon is given (by Google) as:

www.space.com › 18135-how-big-is-the-moon
Oct 28, 2017 — Mass, density and gravity The moon's mass is 7.35 x 10^22 kg, about 1.2 percent of Earth's mass. Put another way, Earth weighs 81 times more than the moon. The moon's density is 3.34 grams per cubic centimeter (3.34 g/cm3). That is about 60 percent of Earth's density.

Bennu is (approximately) 7.82 × 10^10 Kg.

The difference is (approximately) 1x10^12

While 78 million tons of carbon would go a long way toward supporting agriculture on the Moon, it would barely show up in a mass reading for the body.

Edit#1:
https://casfs.ucsc.edu/about/publicatio … mistry.pdf

What is soil organic carbon? | Agriculture and Food
... elements needed by plants: From water and air Carbon (C), hydrogen (h), oxygen (o)b) From soil Nitrogen (N), Phosphorus (P), Sulfur (S), Potassium (K), Calcium (Ca), magnesium (mg), Copper (Cu), Iron (Fe), manganese (mn), Zinc (Zn), Boron (B), molybdenum (mo), Cobalt (Co), Chlorine (Cl).

In the case of the Moon, CO2 would have to be made from Carbon by burning it with Oxygen.

(th)

GW Johnson · 2020-11-14 09:18:11

Bear in mind that raw carbon is not useful as fertilizer. You have to use chemistry to create "organic matter" out of it.

That being the case, would not the pre-existing organic matter in the sewage be far more valuable than raw carbon, even on the moon? That is a technique that goes back to the end of the stone age.

You can process it it some to lessen the disease potential (that's called a septic tank, or even a sewage treatment plant). You don't have to use it straight out of the toilet.

GW

Last edited by GW Johnson (2020-11-14 09:18:42)

tahanson43206 · 2020-11-14 09:33:19

For GW Johnson re #44 and subtopic of making soil on the Moon ...

This discussion is a perfect illustration of how the new admission policy for this forum can make a difference ....

It is now possible (and indeed obligatory) to bring in new members with the expertise needed to address various problems/challenges that are identified in the course of planning for settlement of Mars.

Asteroid Bennu is an example (of many) of useful resources wandering around the Solar System, ready to be harvested by enterprising human communities.

There are (on Earth) persons who specialize in biological processes that support agriculture. Such a person, or perhaps even an institution which employs them, could address the questions you've posed with authority, and (equally importantly) guide the decision making of the thousands of people who will be working to build up a viable self-sustaining community on the Moon, as well as on Mars, where the challenges are less severe but still significant.

My observation is that 78,000,000 tons of manure is quite likely to occur for a population as large as that of Earth.

If someone with posting access to this forum would be willing to investigate, I'd be interested to know approximately how many humans are needed and for what period of time they would exert themselves, to make 78,000,000 tons of manure.

(th)

GW Johnson · 2020-11-14 09:48:38

I'm no expert in this area. But I have observed many things in the course of a long life.

It was the custom in Korea during the time of the Korean War to use human sewage directly in the garden. This was in a country which at that time most people were small farmers. Such may still be true today, I don't know. More people there are city dwellers today.

But what it shows is a "circuit" on a small scale, from waste to produce. Not really a closed cycle, but almost. This is a technique that goes back to the stone age. We already know it works. And quite well.

Modified with a little sewage treatment to control disease, this should still work in smallish near-closed-cycle situations today.

I personally don't know how to do that, but observing how nearly-closed that cycle has been these last 10 millennia, says quite clearly that this will work. You only have to make up those differences traceable to it not being a fully-closed cycle. And that is really a rather favorable outcome.

If you will excuse my choice for words, just "food for thought".

GW (bad joke and all)

PS - first cut approximation: waste + wastewater output from a person ~ water + food intake into a person. ~5 pounds in, ~5 pounds out, each day. What could be simpler?

PPS: I have broached this same topic as "food for thought" in RobertDyck's large ship topic, as well.

Last edited by GW Johnson (2020-11-14 09:52:16)

GW Johnson · 2020-11-14 09:59:24

Here's a notion to consider. 16Psyche is thought to be largely made of nickel-iron alloy. It is a larger body. Say you locate some sort of refining plant upon it. IF you can separate the iron from the nickel in that process, AND you can import essentially amorphous carbon from C-type bodies like Bennu, then you have the means to create carbon steel and nickel steel alloys totally outside large gravity wells!

I know how steel is made here on Earth. Those processes will not work out in vacuum and near-zero-gravity. But there is bound to be a process that would work. The killer will be controlling impurities, especially in the carbon, not the steel-making process itself. We do that by coking the coal down here on Earth. You cannot do that in vacuum. But again, there has to be some process that would work.

What might it mean if large quantities of high-quality steel and steel alloys were available "out there" without resort to import from Earth? Lots of forum participants have wondered about that for a Mars colony? But this is outside even THAT gravity well!

GW

Last edited by GW Johnson (2020-11-14 10:02:36)

SpaceNut · 2020-11-14 10:08:49

The mars homestead waste recovery addresses the sewage use for growing in poor quality soils. see crop topics

http://www.marshome.org/

Building soil

4Frontiers

MarsHome project - seems to be well underway

Wastewater Treatment

tahanson43206 · 2021-08-12 12:17:52

Here's a CNN report on Bennu ...

https://www.cnn.com/2021/08/11/world/na … index.html

The report seems to be fairly well written for a general audience.

Dates of 2018 and 2035 are mentioned as of interest for "close encounters"

(th)

GW Johnson · 2021-08-12 15:39:35

Bennu is said to be a rubble-pile asteroid. It probably has little-or-no cohesion between its particles, only (incredibly weak) gravity. If you exert upon its surface a significant force, it will most likely fly apart. That pretty much rules out nukes and impactors as deflection means. That leaves only the gravity tractor, which requires decades of warning and years to apply. Fortunately, we now have that time with Bennu.

The only way out for nukes or impactors is to make the asteroid fly apart very far from Earth, so that the diameter of the shotgun blast of its particles will be very much larger than the diameter of the Earth. That is how you reduce the total mass impacting Earth, but at the cost of every patch of ground on the impact side of Earth getting hit.

Just food for thought. Lindley Johnson at NASA would agree with me. I met him in Granada in 2009 at that asteroid defense conference.

GW

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Re: NASA's OSIRIS-REx probe to space rock Bennu

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Re: NASA's OSIRIS-REx probe to space rock Bennu

#40 2020-11-11 09:25:30

Re: NASA's OSIRIS-REx probe to space rock Bennu

#41 2020-11-11 12:46:56

Re: NASA's OSIRIS-REx probe to space rock Bennu

#42 2020-11-11 13:20:50

Re: NASA's OSIRIS-REx probe to space rock Bennu

#43 2020-11-13 13:23:24

Re: NASA's OSIRIS-REx probe to space rock Bennu

#44 2020-11-14 09:18:11

Re: NASA's OSIRIS-REx probe to space rock Bennu

#45 2020-11-14 09:33:19

Re: NASA's OSIRIS-REx probe to space rock Bennu

#46 2020-11-14 09:48:38

Re: NASA's OSIRIS-REx probe to space rock Bennu

#47 2020-11-14 09:59:24

Re: NASA's OSIRIS-REx probe to space rock Bennu

#48 2020-11-14 10:08:49

Re: NASA's OSIRIS-REx probe to space rock Bennu

#49 2021-08-12 12:17:52

Re: NASA's OSIRIS-REx probe to space rock Bennu

#50 2021-08-12 15:39:35

Re: NASA's OSIRIS-REx probe to space rock Bennu

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