NASA's Asteroid redirect/retrieval mission; should it be cancelled?

SpaceNut · 2021-11-23 18:08:55

NASA set to launch spacecraft to kick an asteroid off course

NASA is preparing to launch a mission to deliberately smash a spacecraft into an asteroid -- a test run should humanity ever need to stop a giant space rock from wiping out life on Earth.
It may sound like the stuff of science fiction, but the DART (Double Asteroid Redirection Test) is a real proof-of-concept experiment, blasting off at 10:21 pm Pacific Time Tuesday (0621 GMT Wednesday) aboard a SpaceX rocket from Vandenberg Space Force Base in California.
Its target object: Dimorphos, a "moonlet" around 525 feet (160 meters, or two Statues of Liberty) wide, circling a much larger asteroid called Didymos (2,500 feet or 780 meters in diameter), which together orbit the Sun.
Impact should take place in the fall of 2022, when the pair of rocks are 6.8 million miles (11 million kilometers) from Earth, the nearest point they ever get.
"What we're trying to learn is how to deflect a threat," said NASA's top scientist Thomas Zuburchen in a press call, of the $330 million project, the first of its kind.
To be clear, the asteroids in question pose no threat to our home planet.
But they belong to a class of bodies known as Near-Earth Objects (NEOs) -- asteroids and comets that approach our planet within 30 million miles (50 million kilometers).
NASA's Planetary Defense Coordination Office is most interested in those larger than 460 feet (140 meters) in size, which have the potential to level entire cities or regions with many times the energy of average nuclear bombs.
There are 10,000 known near-Earth asteroids 460 feet in size or greater, but none has a significant chance to hit in the next 100 years. One major caveat: only about 40 percent of those asteroids have been found to date.
- 15,000 mph kick -
Planetary scientists can create miniature impacts in labs and use the results to create sophisticated models about how to divert an asteroid -- but models rely on imperfect assumptions, which is why they want to carry out a real world test.
The DART probe, which is a box the size of a large fridge with limousine-sized solar panels on either side, will slam into Dimorphos at just over 15,000 miles an hour (24,000 kilometers per hour), causing a small change in the asteroid's motion.
Scientists say the pair are an "ideal natural laboratory" for the test, because Earth-based telescopes can easily measure the brightness variation of the Didymos-Dimorphos system and judge the time it takes Dimorphos to orbit its big brother.
Their orbit never intersects our planet, providing a safe way to measure the effect of the impact, scheduled to occur between September 26 and October 1, 2022.
Andy Rivkin, DART investigation team lead, said that the current orbital period is 11 hours and 55 minutes, and the team expects the kick will shave around 10 minutes off Dimorphos' orbit.
There is some uncertainty about how much energy will be transferred by the impact, because the moonlet's internal composition and porosity isn't known.
The more debris that's generated, the more push will be imparted on Dimorphos.
"Every time we show up at an asteroid, we find stuff we don't expect," said Rivkin.
The DART spacecraft also contains sophisticated instruments for navigation and imaging, including the Italian Space Agency's Light Italian CubeSat for Imaging of Asteroids (LICIACube) to watch the crash and its after-effects.
The trajectory of Didymos could also be slightly affected, but it would not significantly alter its course or unintentionally imperil Earth, scientists say.
- Nuclear blasts -
The so-called "kinetic impactor" method isn't the only way to divert an asteroid, but it is the technique that is the most ready with current technology.
Others that have been hypothesized include flying a spacecraft close by to impart a small gravitational force.
Another is detonating a nuclear blast close by -- but not on the object itself, as in the films Armageddon and Deep Impact -- which would probably create many more perilous objects.
Scientists estimate 460 feet asteroids strike once every 20,000 years.
Asteroids that are six miles wide (10 kilometers) -- such as the one that struck 66 million years ago and led to the extinction of most life on Earth, including the dinosaurs -- occur around every 100-200 million years

Mars_B4_Moon · 2021-11-28 15:07:22

NASA launches first ever asteroid deflection mission

https://news.sky.com/story/nasa-launche … n-12476454

SpaceNut · 2024-09-13 16:42:48

Earth’s New Visitor: Asteroid to Become Temporary Mini-moon for Two Months

Starting on September 29, 2024, Earth will briefly have a second "moon" as a small asteroid, 2024 PT5, gets captured by our planet's gravity. This mini-moon will stick around for nearly two months before continuing its journey through space.

AA1qw9iX.img?w=768&h=466&m=6

tahanson43206 · 2024-09-13 19:48:40

For SpaceNut re #53

Thanks for alerting us to this opportunity. Apparently it is too early for humans to jump on a visiting object like that. It doesn't sound dangerous. It sure would be a good place to put a radio beacon that would act like a buoy attached to a floating wreck in the open ocean.

(th)

GW Johnson · 2024-09-15 12:31:08

There's other discussions in other threads about the actual result from smacking into Didymoon. Yes, they changed its orbit, and by more than they expected. I've heard that a lot.

What no one wants to talk about in public is the amount of debris flung free into space from Didymoon, and that it almost came completely apart, despite the very small size of the impacting craft. The extra debris spalled into space is EXACTLY why they got more orbit change than they expected. They did NOT expect to nearly break up the asteroid the way they very nearly did.

But they SHOULD have expected this!

Didymoon was C-type, not S-type, and certainly not M-type. Everything we have visited that was classifiable as C-type has been dry fragments held together by NOTHING but vanishingly-weak gravity. Why on Earth anyone would be surprised that a suddenly-applied force threatens disruption is totally beyond my understanding.

How can you push on a cloud of particles when the forces binding them together are weaker than your slightest possible touch? How can you attach anything to a cloud like that?

If one can go find those other threads with the impact mission discussions, you will see that I have been predicting that very outcome for some years now. I learned about this disruption problem when I went to the asteroid defense conference in Granada, back in 2009. This stuff is not a secret.

GW

tahanson43206 · 2024-09-15 14:10:53

Here is a link to GW's prediction in 2017....

It is close to the actual result.

http://newmars.com/forums/viewtopic.php … 69#p134269

It seems to me that an experiment on some part of the Real Universe is worth doing, even if the result is what you expected.

Often results are different from predictions.

Here's an example of a prediction from 7 years ago that was close to correct.

(th)

GW Johnson · 2024-10-01 10:51:20

The real problem with asteroid/comet defense of Earth is detecting the threats in time to be able to do anything about it. That detection capability still demonstrably does not exist, and the solution has been known for several years, but never built. Multiple in-space detection satellites looking outward in the far infrared, and located well inward of Earth, orbiting the sun.

Once you have some years of warning, you have the option of going out there and trying to deflect the threat with a "small push", which way far out like that, is not a problem even if the body disrupts. If it does, the cloud of fragments will have spread to a size far larger than Earth, so that most of the fragments will miss, even in a dead-center hit.

M-types (metal) are mostly one big solid piece. You can "push" on that pretty hard and not break it up. Which makes a last ditch defense with a big impactor or a nuclear weapon feasible. S-types ("stony") may not be one big piece, perhaps several large chunks. It is still unknown how hard a "push" you can use on it and not break it up, so it is still unknown whether a last-ditch "big push" defense is even feasible with those.

The most numerous by far are the C-type (carbonaceous chondrite) types, which so far have been devoid of ices to bind their small particles together, even when coming from as far out as the main asteroid belt. These are loose rubble piles bound only by mutual gravity, which is vanishingly weak. No last-ditch defense is feasible: you just end up converting the single bullet strike to a small dense shotgun blast, if you try.

If you have multiple years warning (AND you have developed the right kinds of spacecraft and ion engines !!!), you can employ the gravity tractor. But ONLY if you have multiple years of warning! That kind of deflection does not significantly disrupt even the C-types, because the applied "push" is the same magnitude of strength as the binding force.

I see absolutely no progress since the 2009 meeting that I attended, toward fielding ANY of the right equipment to accomplish any of this defense need. With one (and only one) recent exception: NASA is (finally !!!) launching an infrared asteroid detection satellite, to be at one of Earth's LaGrange points. That's the right detection method, but not yet the right place to put it.

And, until you have multiple years of warning, you are faced with only last-ditch "big push" defense, which cannot work with the vast majority of these objects, those being C-types that are dry and thus loose rubble piles.

GW

Last edited by GW Johnson (2024-10-01 10:58:06)

Calliban · 2024-10-02 04:06:57

This is useful for anyone interested in asteroid missions.
https://cneos.jpl.nasa.gov/nhats/

I'm not sure how mission dV is calculated. Is this dV to get to the asteroid and back from LEO, or is it dV after achieving Earth escape? It would also be interesting to know what mission requirements would be if setting out and returning to L5. This is ultimately where space based industries are likely to be established.

Most of these asteroids are quite small, ranging from <10m in diameter to 100m in diameter.
******

This asteroid is particularly interesting.
https://en.m.wikipedia.org/wiki/(341843)_2008_EV5

Semi-major axis comparable to Earth: 0.96AU. Perihelion is 0.88AU, Aphelion is 1.04AU. Inclination is 7°. This would be easy to visit by spacecraft, easier to reach propulsively than the lunar surface. What is more, the asteroid appears to a carbonaceous condrite and should therefore be enriched in volatiles not easily sourced from the moon. Estimated diameter is 400m. Assuming a density similar to water, that would imply a mass of about 30 million tonnes. That is a lot of very useful material.

Last edited by Calliban (2024-10-02 05:18:06)

GW Johnson · 2024-10-02 08:20:44

The "water" in a C-type asteroid that close to the sun will NOT be ice, but hydrated minerals. The thing will be a dry rubble pile which will not hold any stake you try to drive into it. You can recover water from the hydrated minerals ONLY if you apply a lot of heat energy to it. There is NO easily recoverable resource there!

The C-types that still have real water (and other volatile) ices in them, binding their particle together, are well beyond Jupiter. The sun drove the ices out by sublimation long ago in the smaller ones. Only the very large ones have any ices left. The further out you go, the more prevalent is remnant ice, even in the smaller ones.

Actual volatile ice is the easily-recovered resource, not hydrated minerals.

GW

tahanson43206 · 2024-10-02 11:52:46

For GW Johnson re #59

The energy needed to recover water from hydrated minerals is readily available, because the asteroids of interest ** are ** close to the sun.

It should be possible for today's engineers to figure out how to harvest the material in any solar system body. I think that the word "easy" is all too subjective. Anything is ** easy ** if you know how to do it, and you have the resources you need.

There is nothing "easy" about getting to locations where ice is still available in original solar system material.

it seems to me all these situations are a set of tradeoffs.

It's time for humans to start moving on some of these projects, and chances are some folks actually ** are ** working on early stage development.

(th)

Calliban · 2024-10-02 18:08:01

We have examined asteroid mining in some detail in other threads. Rubble pile asteroids behave like fluid drops when disturbed. They are incapable of sustaining sheer stress. Mining any small asteroid is going to require some kind of enclosing net or bag that prevents pieces from floating off and also provides a surface against which mining tools can exert reaction forces. In another thread, I examined the idea of a ballasted ring in stationary orbit around a small asteroid. Enclosing shovel tools would be mounted on the ring and would take bites from the surface. As the shovel pushes against the asteroid, the centre of mass of the ring is pushed away from the centre of gravity of the asteroid. This results in a net force, pulling the two back into alignment.

I take the point that we are unlikely to find ice in NEAs. Even if water or hydroxl make up 1% of mass, this still makes a NEA orders of magnitude richer in water than lunar regolith. We can release that water by baking material to a few hundred centrigrade in concentrated sunlight. But carbon is just as useful to us. In addition to its biological functions, carbon can be used as a reducing agent for metal ores and as an electrode material in aluminium and titanium production. If we have carbon, we can produce reduced iron, and from it steel. Steel is likely to remain the prefered material for constructing large components in space. Iron is abundant, easy to reduce and is even available as natural stainless steel in asteroids.

Last edited by Calliban (2024-10-02 18:11:20)

Void · 2024-10-03 18:52:00

You might want to study up on "Dark Comets": https://www.sciencealert.com/mysterious … th-objects A new idea that needs confirming.

Ending Pending

GW Johnson · 2024-10-04 08:30:52

This is only my opinion, but I think the distinction between "asteroid" and "comet" in our language was likely a mistake. These bodies are all rather similar, with wildly varying amounts of volatile ices. Some formed with lots of volatiles, others did not (likely forming closer to the sun). Over 4.5 billion years, the ones closer-in have lost their volatiles from sublimation: a bit higher temperature due to sunlight illumination. Way further out, they stay cold enough to retain significant volatiles.

Recovering a resource is only worthwhile if you can afford the costs of extracting it, and then the costs of refining it into something you can really use. There are always refining costs, particularly to create actually-useful metal alloys. But don't forget the up-front extraction costs: this is exactly why fossil fuels were preferred for centuries over anything synthesized. It's just easier to dig something up than it is to heat something up to high temperatures, and try to handle that hot stuff, to obtain what you desire.

Just because you can do something is no reason to believe that you should do that something. The world around us is not simple.

GW

Last edited by GW Johnson (2024-10-04 08:31:21)

Void · 2024-10-04 10:47:10

I was passing on claims that the asteroid belt used to be a source of comets, and that there might be some fossil ice in some of them. This is not yet confirmed, rather there seems to be a little bit of evidence for it.

Even so, getting ice from a core of an object is going to be a challenge, even if it turns out that some objects have it.

Ending Pending

GW Johnson · 2024-10-04 18:32:06

Void:

The conventional wisdom is that most comets come from the Oort cloud and the Kuiper Belt, both well outside the orbit of Neptune. But, who really knows?

There are some asteroids in the Main Belt that occasionally show comet tails. However, these are invariably among the larger asteroids. None of the little ones do that.

GW

New Mars Forums

Announcement

#51 2021-11-23 18:08:55

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#52 2021-11-28 15:07:22

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#53 2024-09-13 16:42:48

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#54 2024-09-13 19:48:40

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#55 2024-09-15 12:31:08

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#56 2024-09-15 14:10:53

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#57 2024-10-01 10:51:20

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#58 2024-10-02 04:06:57

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#59 2024-10-02 08:20:44

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#60 2024-10-02 11:52:46

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#61 2024-10-02 18:08:01

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#62 2024-10-03 18:52:00

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#63 2024-10-04 08:30:52

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#64 2024-10-04 10:47:10

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

#65 2024-10-04 18:32:06

Re: NASA's Asteroid redirect/retrieval mission; should it be cancelled?

Board footer