OT: First attempt at a planet-buster (DART mission)

[pete...@gmail.com]

I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
if it could alter the asteroid's orbit.

https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034

I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.

While last night we could only see until the probe hit, ending transmissions, the plume of debris was seen by earth based telescopes, and a European cube sat should download closer images later today.

[Jack Bohn]

The cubesat photos: closer than Earth, but farther than the impactor, that's what I'm waiting for!

--
-Jack

[Michael F. Stemper]

On 27/09/2022 08.21, pete...@gmail.com wrote:
> I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
> if it could alter the asteroid's orbit.
>
> https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034

'twas quite cool. Especially the last minute or so, when the
target suddenly became quite (visually) large. And then the
transmission stopped.

> I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.

I missed that one. I guess that my parents weren't interested. To
their credit, they did get me up to watch the launch of Shepard's
sub-orbital flight.

> While last night we could only see until the probe hit, ending transmissions, the plume of debris was seen by earth based telescopes, and a European cube sat should download closer images later today.

I had been expecting the view to immediately switch to the
cube-sat after the impact, or possibly even have side-by-side
video.

ObSFW: In Heinlein's "The Man Who Sold the Moon", the technology
for communicating from the Moon to Earth didn't exist, or was too
massive to include, or something like that. Now, we have live
video from 11 million km away!

--
Michael F. Stemper
Deuteronomy 24:17

[Paul S Person]

n Tue, 27 Sep 2022 06:21:44 -0700 (PDT), "pete...@gmail.com"

I thought the idea was to see if we could divert killer asteroids and
so protect the Earth that way or not.

Planet-busting is surely a very long-term goal, if a goal at all.
--
"In this connexion, unquestionably the most significant
development was the disintegration, under Christian
influence, of classical conceptions of the family and
of family right."

[peterw...@hotmail.com]

On Tuesday, September 27, 2022 at 11:51:16 AM UTC-5, Paul S Person wrote:
> n Tue, 27 Sep 2022 06:21:44 -0700 (PDT), "pete...@gmail.com"
> <pete...@gmail.com> wrote:
>
> >I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
> >if it could alter the asteroid's orbit.
> >
> >https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034
> >
> >I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.
> >
> >While last night we could only see until the probe hit, ending transmissions, the plume of debris was seen by earth based telescopes, and a European cube sat should download closer images later today.
> I thought the idea was to see if we could divert killer asteroids and
> so protect the Earth that way or not.
>
> Planet-busting is surely a very long-term goal, if a goal at all.

Planet-busting is an ideal whose existence we infer from the fact that there is variation in the size of craters.

Peter Wezeman
anti-social Darwinist

[peterw...@hotmail.com]

On Tuesday, September 27, 2022 at 8:21:46 AM UTC-5, pete...@gmail.com wrote:
> I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
> if it could alter the asteroid's orbit.
>
> https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034
>
> I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.
>

I have a vague memory of reading about a group of people watching the Ranger 9 live coverage, and one
of them shouting, "Pull up, pull up!"

Peter Wezeman
anti-social Darwinist

[Robert Carnegie]

On Tuesday, 27 September 2022 at 17:51:16 UTC+1, Paul S Person wrote:
> n Tue, 27 Sep 2022 06:21:44 -0700 (PDT), "pete...@gmail.com"
> <pete...@gmail.com> wrote:
>
> >I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
> >if it could alter the asteroid's orbit.
> >
> >https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034
> >
> >I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.
> >
> >While last night we could only see until the probe hit, ending transmissions, the plume of debris was seen by earth based telescopes, and a European cube sat should download closer images later today.
> I thought the idea was to see if we could divert killer asteroids and
> so protect the Earth that way or not.
>
> Planet-busting is surely a very long-term goal, if a goal at all.

From documentary, _Armageddon_ - " That's what we call
a global killer." I hope they actually don't, but who knows?

[Jay E. Morris]

MY GOD! Don't these people realize the impact[1] they are having on our
ability to produce accurate astrology charts?![2]

[1] yes, that was on purpose
[2] before a previous asteroid impact exercise an astrologer did sue in
(IIRC) federal court on such a basis.

[David Johnston]

https://pbs.twimg.com/media/Fdoa63EUcAAeIXq?format=jpg&name=large

[Paul S Person]

IMDb doesn't seem to have that one.

It /does/ have, of course, the Bruce Willis 1998 non-documentary,
which I saw but found ... a waste of time. I think it was Mr Cranky
who noted that, every time Liv Tyler got sad, we got Yet Another
Aerosmith Song.

/Deep Impact/ did the "big rock hits Earth" story better, and /Space
Cowboys/ did the "old fogies in Space" story much much better.

Both IMHO, of course.

[Paul S Person]

Can we take it that the astrologer was treated with all the respect
they deserved, if not rather more respect than was strictly
appropriate?

[Lynn McGuire]

On 9/28/2022 11:39 AM, Paul S Person wrote:
> On Tue, 27 Sep 2022 13:53:56 -0700 (PDT), Robert Carnegie
> <rja.ca...@excite.com> wrote:
>
>> On Tuesday, 27 September 2022 at 17:51:16 UTC+1, Paul S Person wrote:
>>> n Tue, 27 Sep 2022 06:21:44 -0700 (PDT), "pete...@gmail.com"
>>> <pete...@gmail.com> wrote:
>>>
>>>> I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
>>>> if it could alter the asteroid's orbit.
>>>>
>>>> https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034
>>>>
>>>> I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.
>>>>
>>>> While last night we could only see until the probe hit, ending transmissions, the plume of debris was seen by earth based telescopes, and a European cube sat should download closer images later today.
>>> I thought the idea was to see if we could divert killer asteroids and
>>> so protect the Earth that way or not.
>>>
>>> Planet-busting is surely a very long-term goal, if a goal at all.
>>
>>From documentary, _Armageddon_ - " That's what we call
>> a global killer." I hope they actually don't, but who knows?
>
> IMDb doesn't seem to have that one.
>
> It /does/ have, of course, the Bruce Willis 1998 non-documentary,
> which I saw but found ... a waste of time. I think it was Mr Cranky
> who noted that, every time Liv Tyler got sad, we got Yet Another
> Aerosmith Song.
>
> /Deep Impact/ did the "big rock hits Earth" story better, and /Space
> Cowboys/ did the "old fogies in Space" story much much better.
>
> Both IMHO, of course.

You mean you were not impressed by the two space shuttles in formation
flying past the Moon in "Armageddon" ?

Looked cool but not real.

Lynn

[Robert Carnegie]

On Wednesday, 28 September 2022 at 17:39:15 UTC+1, Paul S Person wrote:
> On Tue, 27 Sep 2022 13:53:56 -0700 (PDT), Robert Carnegie
> <rja.ca...@excite.com> wrote:
>
> >On Tuesday, 27 September 2022 at 17:51:16 UTC+1, Paul S Person wrote:
> >> n Tue, 27 Sep 2022 06:21:44 -0700 (PDT), "pete...@gmail.com"
> >> <pete...@gmail.com> wrote:
> >>
> >> >I'm surprised no one has mentioned this yet. Last night, NASA slammed a probe into an asteroid at 4 miles per second, to see what would happen, and
> >> >if it could alter the asteroid's orbit.
> >> >
> >> >https://abcnews.go.com/Technology/nasas-dart-spacecraft-expected-collide-asteroid-watch/story?id=90523034
> >> >
> >> >I watched live. Brought back memories of watching Ranger 9 do the same to the Moon in 1965, as a little kid.
> >> >
> >> >While last night we could only see until the probe hit, ending transmissions, the plume of debris was seen by earth based telescopes, and a European cube sat should download closer images later today.
> >> I thought the idea was to see if we could divert killer asteroids and
> >> so protect the Earth that way or not.
> >>
> >> Planet-busting is surely a very long-term goal, if a goal at all.
> >
> >From documentary, _Armageddon_ - " That's what we call
> >a global killer." I hope they actually don't, but who knows?
> IMDb doesn't seem to have that one.
>
> It /does/ have, of course, the Bruce Willis 1998 non-documentary,

This is the work to which I refer.

[Paul S Person]

The only thing that impressed me was its resemblance to a very large
cow-pie.

The theater I saw it in summarized it best: on the poster outside they
had a card with a typed line:

Manly men doing manly things. In space.

[Quadibloc]

On Wednesday, September 28, 2022 at 10:41:18 AM UTC-6, Paul S Person wrote:
> On Tue, 27 Sep 2022 15:55:55 -0500, "Jay E. Morris"
> <mor...@epsilon3.comcon> wrote:

> >MY GOD! Don't these people realize the impact[1] they are having on our
> >ability to produce accurate astrology charts?![2]

> >[1] yes, that was on purpose
> >[2] before a previous asteroid impact exercise an astrologer did sue in
> >(IIRC) federal court on such a basis.

> Can we take it that the astrologer was treated with all the respect
> they deserved, if not rather more respect than was strictly
> appropriate?

Of course, if astrologers are able to predict the orbits of planets that
haven't been discovered yet, no doubt they can predict when asteroids
will be sent out of their accustomed orbits...

Myself, I am just happy that today, after searching for quite some time,
I have finally discovered the symbols that *some* astrologers have used
for G. E. Sutcliffe's hypothetical planets Isis and Osiris...

http://www.quadibloc.com/other/as02.htm

Still, I'm certainly glad that the astrologer did not win his case, as I think
that preventing the Earth from being hit by an asteroid is rather more important.

John Savard

[Quadibloc]

On Tuesday, September 27, 2022 at 10:51:16 AM UTC-6, Paul S Person wrote:

> I thought the idea was to see if we could divert killer asteroids and
> so protect the Earth that way or not.
>
> Planet-busting is surely a very long-term goal, if a goal at all.

You're quite right.

But Carl Sagan, writing during the Cold War, recommended strongly against
developing a capability to divert asteroids heading to Earth... because such
a capability would inevitably also include the ability to send asteroids to
Earth, thus adding a dangerous new dimension to the arms race.

John Savard

[Quadibloc]

On Wednesday, September 28, 2022 at 10:41:18 AM UTC-6, Paul S Person wrote:
> On Tue, 27 Sep 2022 15:55:55 -0500, "Jay E. Morris"
> <mor...@epsilon3.comcon> wrote:

> >[2] before a previous asteroid impact exercise an astrologer did sue in
> >(IIRC) federal court on such a basis.

> Can we take it that the astrologer was treated with all the respect
> they deserved, if not rather more respect than was strictly
> appropriate?

I think I found the news item.

It had to do with the Deep Impact mission to comet Tempel 1.

The astrologer was Marina Bal; she sued in a _Russian_ court
for $300 million in moral damages because this upset the
natural balance of the universe.

John Savard

[Quadibloc]

On Friday, September 30, 2022 at 11:39:37 PM UTC-6, Quadibloc wrote:

> The astrologer was Marina Bal;

Oops, Marina Bai. The story was originally carried in Izvestia, but made
it to CBS News and then Slashdot...

John Savard

[Quadibloc]

"The Marsh of Camarina", Chapter 18 of _Pale Blue Dot_.

John Savard

[Quadibloc]

On Friday, September 30, 2022 at 11:39:37 PM UTC-6, Quadibloc wrote:

> she sued in a _Russian_ court

And, given that, no doubt the court found the case invalid due to a lack
of jurisdiction, and thus it did not need to address the case on its merits
or lack thereof.

John Savard

[Nils Hammer]

> I thought the idea was to see if we could divert killer asteroids

Indeed, as compared to the plan where you dock with the asteroid and fire jets for carefully controlled vectors, or blast it with nukes at a carefully planned distance that ought not to break it up.

[Paul S Person]

But docking makes for very exciting movies!

And, for a killer asteroids, breaking up is not hard to do -- in
movies.

[pete...@gmail.com]

On Monday, October 3, 2022 at 11:16:09 AM UTC-4, Paul S Person wrote:
> On Sun, 2 Oct 2022 14:38:43 -0700 (PDT), Nils Hammer
> <sledgem...@gmail.com> wrote:
>
> >
> >> I thought the idea was to see if we could divert killer asteroids
> >Indeed, as compared to the plan where you dock with the asteroid and fire jets for carefully controlled vectors, or blast it with nukes at a carefully planned distance that ought not to break it up.
> But docking makes for very exciting movies!
>
> And, for a killer asteroids, breaking up is not hard to do -- in
> movies.

It seems that a lot of asteroids are 'dust bunnies', unconsolidated collections of dust, gravel, and rocks with almost no internal strength. There's a lot of void space inside. Hitting one kicks out a *lot* of material, and hitting it too hard may completely disrupt it.

pt

[Jay E. Morris]

Thanks. Appears my misrememberer was in full force.

[Robert Carnegie]

...Without really solving the "deadly rock from space"
problem. Just altering it to "a vast rain shower of
burning gravel".

[Dimensional Traveler]

Pop it far enough out and most of it should miss the planet.

--
I've done good in this world. Now I'm tired and just want to be a cranky
dirty old man.

[Scott Lurndal]

All you need is to slightly slow it down, or speed it up
and its orbit and earths orbit will no longer intersect.

[Quadibloc]

On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:

> ...Without really solving the "deadly rock from space"
> problem. Just altering it to "a vast rain shower of
> burning gravel".

Since it's only very big rocks that don't completely burn up
before hitting the ground, I'd say that blowing up an asteroid
into little pieces is seriously underrated as a solution.

And any asteroid that's a "dust bunny" wasn't a problem to
begin with.

The problem is that a big chunk of rock could be blown up into
a number of harmless small fragments, and a piece or two big
enough to do real damage. So deflecting the whole thing is a
certain solution, and to be preferred.

John Savard

[Quadibloc]

On Monday, October 3, 2022 at 5:08:06 PM UTC-6, Scott Lurndal wrote:

> All you need is to slightly slow it down, or speed it up
> and its orbit and earths orbit will no longer intersect.

Not really.

As an example, let's take an asteroid in an orbit that is at 4 AU at
aphelion, and at 0.85 AU at perihelion.

If you slightly slow down, or speed up, the orbit of that asteroid
at perihelion, its orbit will *continue* to intersect the orbit of the
Earth, only the distance from the Sun at aphelion will change.

If you speed it up *enough* at aphelion so that its perihelion is
greater than 1 AU, _then_ its orbit will no longer intersect the
Earth's. Slowing it down slightly won't achieve that.

The easiest way to ensure such an asteroid will at least miss the Earth
*this* time would be with an off-center impact about halfway between
perihelion and aphelion, so that the tilt of its orbit is changed, and it is
well below, or well above, the plane of the ecliptic for the entire part
of the orbit that is near perihelion.

The thing is, though, that the nodes of orbits usually precess due to
perturbations, so even that won't permanently remove the risk.

But if you can change an impact with the Earth into a close encounter with
the Earth, then the Earth's gravity will drastically change the asteroid's orbit
during that encounter. The bad news is that the new orbit will still intersect
the Earth's orbit.

The _good_ news is that since the change is drastic, a very slight change in the
parameters of the encounter will affect that change in a big way. So now is
the chance, with a small input of energy, to change the asteroid's orbit so that
it will have a close encounter with Mars. (Or some other planet.)

That close encounter *could* change the asteroid's orbit so that it will never
again come anywhere near the Earth (at least until it has _another_ close
encounter with Mars, which could change its orbit to just about anything).
Of course, if it hits Mars, the problem is permanently solved.

John Savard

[Quadibloc]

On Tuesday, October 4, 2022 at 7:30:56 AM UTC-6, Quadibloc wrote:

> The easiest way to ensure such an asteroid will at least miss the Earth
> *this* time would be with an off-center impact about halfway between
> perihelion and aphelion, so that the tilt of its orbit is changed, and it is
> well below, or well above, the plane of the ecliptic for the entire part
> of the orbit that is near perihelion.

Even that, though, might be difficult.

Let's take, say, a sphere 10 kilometres in diameter, with a density of 2.65
grams per cubic centimetre. (That's about right for a stony asteroid;
a nickel-iron one would be heavier, a carbonaceous chondrite would be
lighter.)

This would be a mass of 5.236 * (10^14) kilograms.

Now, if we made a two-stage hydrogen bomb, where an ordinary
hydrogen bomb replaces the atomic bomb as the trigger for a bigger
hydrogen bomb, perhaps a yield of one gigaton or more could be
achieved. Would that be enough to produce any noticeable change
in the motion of such a large object?

Perhaps dinosaur-killers are usually somewhat smaller than that, so
we would have a chance... but I couldn't find a figure on how much
momentum a nuclear explosion might provide. The only thing I did
see was that a 1.2 megaton warhead ought to deflect an asteroid
enough with 5 years advance notice.

John Savard

[pete...@gmail.com]

Yes, the debris DART kicked out are already forming a 20,000 mile tail.

If you can make it miss entirely, thats clearly the best result. But even
making a lot of it miss would help.

pt

[pete...@gmail.com]

On Tuesday, October 4, 2022 at 9:30:56 AM UTC-4, Quadibloc wrote:
> On Monday, October 3, 2022 at 5:08:06 PM UTC-6, Scott Lurndal wrote:
>
> > All you need is to slightly slow it down, or speed it up
> > and its orbit and earths orbit will no longer intersect.
> Not really.
>

> If you slightly slow down, or speed up, the orbit of that asteroid
> at perihelion, its orbit will *continue* to intersect the orbit of the
> Earth, only the distance from the Sun at aphelion will change.

If a rock has been intersecting our orbit for billions of years, and only *now*
is on an impact vector, making it miss *now* will almost certainly mean it
won't do so again for more billions of years. That's a pretty good solution.

Don't let the best be the enemy of the good.

pt

[Paul S Person]

While not the best film on this topic, /Greenland/ does have a scene
illustrating that "burning gravel". Since all the actual Big Rock Hits
look the same, this scene provides something refreshingly different to
look at.

[Quadibloc]

On Tuesday, October 4, 2022 at 8:38:54 AM UTC-6, pete...@gmail.com wrote:

> If a rock has been intersecting our orbit for billions of years, and only *now*
> is on an impact vector, making it miss *now* will almost certainly mean it
> won't do so again for more billions of years. That's a pretty good solution.
>
> Don't let the best be the enemy of the good.

That's a good point. But my point was to note that if one is going to nudge a
body into a different orbit that poses no hazard to the Earth, there are some
ways to do that which are more effective than others.

I'm sure that the people in charge at NASA, should they be faced with deflecting
a body that poses a threat, will have a sound grasp of orbital mechanics, and they
will be willing to settle for anything they can achieve that will avoid a disaster as
well.

John Savard

[Robert Carnegie]

AIUI, in the burning gravel scenario, if the rocks don't
reach the ground, the best does. Ask a dinosaur
oh you can't.

[Robert Carnegie]

Meaning "the heat". My tablet finger slipped, probably.

[Paul S Person]

On Tue, 4 Oct 2022 16:03:59 -0700 (PDT), Quadibloc <jsa...@ecn.ab.ca>
wrote:

The people in charge at NASA, presumably, devised and implemented the
test under discussion precisely to get a handle on what might or might
not work. Before they have to bet the planet on it.

[William Hyde]

On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
>
> > ...Without really solving the "deadly rock from space"
> > problem. Just altering it to "a vast rain shower of
> > burning gravel".
> Since it's only very big rocks that don't completely burn up
> before hitting the ground, I'd say that blowing up an asteroid
> into little pieces is seriously underrated as a solution.

And you'd be wrong.


William Hyde

[James Nicoll]

In article <2560ba81-c58c-453d...@googlegroups.com>,

What, there's a downside to a cloud of small debris hitting the
upper atmosphere at 30 km/s and heating the sky to the temperature
of a kiln? Are plants and animals suddenly flammable?
--
My reviews can be found at http://jamesdavisnicoll.com/
My tor pieces at https://www.tor.com/author/james-davis-nicoll/
My Dreamwidth at https://james-davis-nicoll.dreamwidth.org/
My patreon is at https://www.patreon.com/jamesdnicoll

[pete...@gmail.com]

Depends, but Quaddies probably correct.

It greatly depends on how much material you're dealing with.

The problem is that an entering meteor heats up the air around it to plasma
temperatures as it falls. Its BRIGHT, which is why a pea-sized meteor can be
seen 60 miles away on the ground.

When the Chicxulub impactor hit, it was about 4200 km^3. But it may have
ejected another 250,000 km^3 from the crater it made. Some of this was
ejected into space, and minutes or hours later rained down again over the
whole earth.

That volume is enough to cover the planet 50 cm deep. Now, most of that
landed nearby, only a small fraction was blasted into ballistic orbits outside
the atmosphere.

But that small fraction enough to create disaster. Its enough to occupy ever
single bit of sky visible above your horizon with a plasma-hot meteor trail,
simultaneously.

It would be like standing next to an unshielded blast furnace, everywhere on
earth. That's why the world burned, and no animal that wasn't in a burrow or
deep water perished.

Now, in the disrupted asteroid situation, we're dealing with far less material.
Even for Chicxulub, the initial meteor was only 2% the volume of the total
material that could have contributed to the fallout. The vast majority of asteroids
being disrupted would be orders of magnitude smaller, and even if some fragments
reach the ground, would not be able to blast craters capable of
multiplying the problem.

A big enough cloud of white hot gravel would not be something to look at,
and if you know its coming, you might want to head indoors at the appointed
time, but its unlikely to cause serious damage.

Note that despite millions of meteorites falling since Chicxulub, we have no
record of any of them causing widespread fires by thermal radiation.

pt

[pete...@gmail.com]

On Wednesday, October 5, 2022 at 3:30:28 PM UTC-4, James Nicoll wrote:
> In article <2560ba81-c58c-453d...@googlegroups.com>,
> William Hyde <wthyd...@gmail.com> wrote:
> >On Tuesday, October 4, 2022 at 12:33:24 AM UTC-4, Quadibloc wrote:
> >> On Monday, October 3, 2022 at 4:23:37 PM UTC-6, Robert Carnegie wrote:
> >>
> >> > ...Without really solving the "deadly rock from space"
> >> > problem. Just altering it to "a vast rain shower of
> >> > burning gravel".
> >> Since it's only very big rocks that don't completely burn up
> >> before hitting the ground, I'd say that blowing up an asteroid
> >> into little pieces is seriously underrated as a solution.
> >
> >And you'd be wrong.
> >
> What, there's a downside to a cloud of small debris hitting the
> upper atmosphere at 30 km/s and heating the sky to the temperature
> of a kiln? Are plants and animals suddenly flammable?

Not much. The numbers matter, and I run them in a nearby post.

pt

[Lynn McGuire]

I thought the big meteor that fell in Russia 50 or 70 years ago started
many fires on the ground.
https://en.wikipedia.org/wiki/Tunguska_event

Lynn

[pete...@gmail.com]

You're right. I was mistaken.

Pt

[Dimensional Traveler]

It was also apparently large enough to get deep into the atmosphere
which I would think had something to do with it.

[William Hyde]

I may be behind the times, but I've never seen a reliable calculation that showed
the radiative effect to be this extreme, while we do know that shocked quartz
existed over a thousand miles from the impact, and there is clear evidence
of an "asteroid winter".

Examinations in the teapot dome area by Jack Wolfe, published in Nature,
established the time of the hit as June/July. Evidence, IIRC is for two
debris falls (hypothesized to be one from the main event, more from
a secondary crater), followed rapidly by freezing damage. The site was a
pond so it doesn't really address the burning issue. But we do know
that a fair part of the world did not burn.

That's why the world burned, and no animal that wasn't in a burrow or
> deep water perished.

Not that deep, crocodiles for example. Extinction appears to have been a function of
size, with all large animals that were not sheltered going extinct. Small creatures
survived, including birds.

> Now, in the disrupted asteroid situation, we're dealing with far less material.
> Even for Chicxulub, the initial meteor was only 2% the volume of the total
> material that could have contributed to the fallout. The vast majority of asteroids
> being disrupted would be orders of magnitude smaller, and even if some fragments
> reach the ground, would not be able to blast craters capable of
> multiplying the problem.

It does not matter whether an intact bit of rock reaches the ground. What matters is
the kinetic energy of whatever hits the ground, one rock or a mass of pebbles and
gas.

The smaller the asteroid the smaller the problem, of course.

>
> A big enough cloud of white hot gravel would not be something to look at,
> and if you know its coming, you might want to head indoors at the appointed
> time, but its unlikely to cause serious damage.

As you said, mass is the issue.


I do not think that the integrity of the impactor is terribly relevant at this point. The energy
and momentum do not go away because the components are small. We cannot scale
up the effects of a grain-of-sand sized meteor to an asteroid impact. It's not at all
the same situation: the effects on the planet of the impact of a large mass are going to
be catastrophic, whether it is one rock or one million.

William Hyde

[pete...@gmail.com]

I've shown that the amount of ejected material could lead to plasma-hot reentry trails
covering the entire sky, over the entire earth. The wikipedia article on Tunguska shows
that that far smaller meteor radiativly scorched trees and started fires for miles.

As for birds, there are many species that nest in burrows.
https://www.birdsandblooms.com/birding/attracting-birds/bird-nesting/ground-nesting-birds/
...and which could thus survive.

> The smaller the asteroid the smaller the problem, of course.
> >
> > A big enough cloud of white hot gravel would not be something to look at,
> > and if you know its coming, you might want to head indoors at the appointed
> > time, but its unlikely to cause serious damage.

I posted that before I read the accounts of the Tunguska event, which did cause
a lot of burning, just by radiation. I was mistaken.

> As you said, mass is the issue.
>
>
> I do not think that the integrity of the impactor is terribly relevant at this point. The energy
> and momentum do not go away because the components are small. We cannot scale
> up the effects of a grain-of-sand sized meteor to an asteroid impact. It's not at all
> the same situation: the effects on the planet of the impact of a large mass are going to
> be catastrophic, whether it is one rock or one million.

The big differences are whether it reaches the ground, and then if it can loft crater material
well out of the atmosphere to reenter as secondary impacts.

Disrupting it may prevent it reaching the ground, but all that kinetic energy instead leads
to a white hot air burst.

Pt

[pete...@gmail.com]

On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:

NASA in the last hour has announced the first results.

The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
shortened by 35 minutes. A 10 minute change would have been regarded as
a success.

pt

[Paul S Person]

So now we know it /can/ be done.

Of course, the target has to be fairly solid. A bunch of loosely-bound
rubble might not produce the same happy result.

[Robert Woodward]

In article <aordkhd6kbl77elr1...@4ax.com>,

Paul S Person <pspe...@old.netcom.invalid> wrote:

> On Tue, 11 Oct 2022 12:19:41 -0700 (PDT), "pete...@gmail.com"
> <pete...@gmail.com> wrote:
>
> >On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:
> >
> >NASA in the last hour has announced the first results.
> >
> >The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
> >shortened by 35 minutes. A 10 minute change would have been regarded as
> >a success.
>
> So now we know it /can/ be done.
>
> Of course, the target has to be fairly solid. A bunch of loosely-bound
> rubble might not produce the same happy result.

I believe that Dimorphos is a loosely-bound rubble pile. There was,
after all, a plume over 1000 kilometers long. AFAIK, the observed effect
was significantly larger than the pure momentum transfer. I suspect that
the kinetic energy of the impact resulted in ejecta that increased the
amount of deceleration.

--
"We have advanced to new and surprising levels of bafflement."
Imperial Auditor Miles Vorkosigan describes progress in _Komarr_.
-------------------------------------------------------
Robert Woodward robe...@drizzle.com

[Paul S Person]

On Wed, 12 Oct 2022 21:45:51 -0700, Robert Woodward
<robe...@drizzle.com> wrote:

>In article <aordkhd6kbl77elr1...@4ax.com>,
> Paul S Person <pspe...@old.netcom.invalid> wrote:
>
>> On Tue, 11 Oct 2022 12:19:41 -0700 (PDT), "pete...@gmail.com"
>> <pete...@gmail.com> wrote:
>>
>> >On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:
>> >
>> >NASA in the last hour has announced the first results.
>> >
>> >The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
>> >shortened by 35 minutes. A 10 minute change would have been regarded as
>> >a success.
>>
>> So now we know it /can/ be done.
>>
>> Of course, the target has to be fairly solid. A bunch of loosely-bound
>> rubble might not produce the same happy result.
>
>I believe that Dimorphos is a loosely-bound rubble pile. There was,
>after all, a plume over 1000 kilometers long. AFAIK, the observed effect
>was significantly larger than the pure momentum transfer. I suspect that
>the kinetic energy of the impact resulted in ejecta that increased the
>amount of deceleration.

The article I read also points to the plume as helping explain the
better-than-expected result.

But it also contained a statement that this might not work if the
whole thing was just rubble: nothing to push on!

[Dimensional Traveler]

On 10/13/2022 9:04 AM, Paul S Person wrote:
> On Wed, 12 Oct 2022 21:45:51 -0700, Robert Woodward
> <robe...@drizzle.com> wrote:
>
>> In article <aordkhd6kbl77elr1...@4ax.com>,
>> Paul S Person <pspe...@old.netcom.invalid> wrote:
>>
>>> On Tue, 11 Oct 2022 12:19:41 -0700 (PDT), "pete...@gmail.com"
>>> <pete...@gmail.com> wrote:
>>>
>>>> On Friday, October 7, 2022 at 12:03:57 AM UTC-4, pete...@gmail.com wrote:
>>>>
>>>> NASA in the last hour has announced the first results.
>>>>
>>>> The asteroid's orbit around its primary, 11 hours and 55 minutes, has been
>>>> shortened by 35 minutes. A 10 minute change would have been regarded as
>>>> a success.
>>>
>>> So now we know it /can/ be done.
>>>
>>> Of course, the target has to be fairly solid. A bunch of loosely-bound
>>> rubble might not produce the same happy result.
>>
>> I believe that Dimorphos is a loosely-bound rubble pile. There was,
>> after all, a plume over 1000 kilometers long. AFAIK, the observed effect
>> was significantly larger than the pure momentum transfer. I suspect that
>> the kinetic energy of the impact resulted in ejecta that increased the
>> amount of deceleration.
>
> The article I read also points to the plume as helping explain the
> better-than-expected result.
>
> But it also contained a statement that this might not work if the
> whole thing was just rubble: nothing to push on!

Or too many individual things to push on.

[Quadibloc]

On Thursday, October 13, 2022 at 10:04:37 AM UTC-6, Paul S Person wrote:

> But it also contained a statement that this might not work if the
> whole thing was just rubble: nothing to push on!

And that is quite a reasonable argument, despite the wording having
an unfortunate resemblance to a fallacious argument that rockets
can't work. (You know, the one which requires never having heard of
Newton's Third Law.)

John Savard

[pete...@gmail.com]

No.

If there was 'nothing to push on' the probe would pass through the asteroid
without slowing.

I note that the Wikipedia article on the target 'Dimorphos' characterizes it as
a 'low-density rubble pile'.

Even a rubble pile provides resistance, and kinetic energy is transferred from
the probe to the material of the asteroid, similarly to how mere air can slow
a bullet.

Dimorphos is only about 170 meters across (hitting it at >4 miles/sec is quite
a feat). The impact was the equivalent of several tons of TNT, and is though to
have blown a crater 150 meters across - ie, it blew out a whole side of the asteroid.
We'll get photos in a few years on a follow-up mission.

Blowing stuff out in the opposite direction of the probe's path increased the
amount by which the asteroid's velocity changed, over what would happen
if the probe just entered the asteroid without kicking stuff up.

pt

[Scott Lurndal]

Quadibloc <jsa...@ecn.ab.ca> writes:
>On Thursday, October 13, 2022 at 10:04:37 AM UTC-6, Paul S Person wrote:
>
>> But it also contained a statement that this might not work if the
>> whole thing was just rubble: nothing to push on!
>
>And that is quite a reasonable argument,

Is it? What is the effect of the rubble flying off in all
directions on the orbit of the object?

[Paul S Person]

On Fri, 14 Oct 2022 13:43:51 GMT, sc...@slp53.sl.home (Scott Lurndal)
wrote:

If it is /really/ "all directions", it might well net out to ... none
at all.

An actual space scientist/physicist made the statement, BTW.

[Dorothy J Heydt]

In article <7b3c4a88-31ae-431c...@googlegroups.com>,

(Hal Heydt)
One might also expect there to have been considerable heating
from the impact energy, which could create a "jet" of material
adding to the delta-v.

[Quadibloc]

On Friday, October 14, 2022 at 7:18:03 AM UTC-6, pete...@gmail.com wrote:
> On Friday, October 14, 2022 at 3:40:10 AM UTC-4, Quadibloc wrote:
> > On Thursday, October 13, 2022 at 10:04:37 AM UTC-6, Paul S Person wrote:
> >
> > > But it also contained a statement that this might not work if the
> > > whole thing was just rubble: nothing to push on!

> > And that is quite a reasonable argument, despite the wording having
> > an unfortunate resemblance to a fallacious argument that rockets
> > can't work. (You know, the one which requires never having heard of
> > Newton's Third Law.)

> No.
>
> If there was 'nothing to push on' the probe would pass through the asteroid
> without slowing.

If the "whole thing was just rubble", then there would be no way to transfer
momentum to the entirety of the asteroid in a uniform way - unless you
had a tractor beam or antigravity. So while you are correct if one takes the
wording in a precise literal sense, it is still the case that there is no convenient
handle to grab with which to move the asteroid - no place where one can push,
and push the whole asteroid as a unit as the result.

That was what was _meant_, as ought to have been obvious.

John Savard

[pete...@gmail.com]

A rubble pile asteroid still has self binding by its own gravity. As long as most
doesn't experience acceleration beyond its escape velocity, it will all experience
the bulk acceleration, and hang together, perhaps with a little rearrangement.

Pt

[Robert Carnegie]

On Friday, 14 October 2022 at 17:00:29 UTC+1, Paul S Person wrote:
> On Fri, 14 Oct 2022 13:43:51 GMT, sc...@slp53.sl.home (Scott Lurndal)
> wrote:
> >Quadibloc <jsa...@ecn.ab.ca> writes:
> >>On Thursday, October 13, 2022 at 10:04:37 AM UTC-6, Paul S Person wrote:
> >>
> >>> But it also contained a statement that this might not work if the
> >>> whole thing was just rubble: nothing to push on!
> >>
> >>And that is quite a reasonable argument,
> >
> >Is it? What is the effect of the rubble flying off in all
> >directions on the orbit of the object?
> If it is /really/ "all directions", it might well net out to ... none
> at all.
>
> An actual space scientist/physicist made the statement, BTW.

You'd apply a force, or an impulse, that accelerates
some or all of the mass out of a collision course
with Earth (if that's what you're attempting), so it
would be different from the asteroid somehow
spontaneously exploding but, mathematically as
a whole, not accelerating.

However, you could fire a space bullet at the
flying rock heap and see the bullet and some of the
rocks fly out of the back of the heap, while the
rest of the asteroid continues in the original course.
Like cutting the core out of an apple.

So maybe we need to start thinking about wrapping
the heap in a big net, first. Or use duct tape.

[pete...@gmail.com]

No need. We have proof of concept.

We *know* that the asteroid had its orbit changed, and
by more than expected.

The 'flying in all directions' video was taken by a cubesat
trailing behind the DART probe, so yes, it looks symmetrical.

If you look at a side view, such as that taken by to James
Webb, it's abundantly clear that most of the ejecta went
In one direction:

https://www.youtube.com/watch?v=P1zukXq4NDc

Pt

[Victor Vasylyev]

It is possible that not the change in the orbit of Dimorphos did play the main role in the observed post-impact features of the mutual asteroid shadowing.
This role could be played by an asymmetric and optically dense near-surface "meteoroid cocoon", consisting of its recoiled debris as a part of material ejected into the hemisphere. Therefore, yet it cannot be ruled out that after the dissipation and fallback of this material onto the surface of Dimorphos, its orbit will be partially or almost completely “restored”.

[Victor Vasylyev]

On Saturday, October 15, 2022 at 11:16:27 PM UTC+3, pete...@gmail.com wrote:

[pete...@gmail.com]

I don't think that's consistent with the two side-on views we have of the post-collision cloud.
You are, as William of Occam would say, 'needlessly multiplying entities'.
Also, a great deal of the material has exceeded the (very low) escape velocity of the Didymous/
Dimorphos system, and much that didn't will wind up on the much larger Didymous.

It will be interesting to see what actually happens.

Pt

[Victor Vasylyev]

The specified "entity" is obvious. Please see the abrupt "swelling" of Dimorphos against the background of a smooth ejection of finer material in the video (starting from the 51st second):
https://groups.google.com/g/rec.arts.sf.written/c/nLwm0ZdZrqw

[Paul S Person]

That wouldn't matter ... provided the potential planet-killer missed
the planet!

Let's keep the eye on the ball here -- this isn't about changing the
orbit for All Eternity; it is about changing it on it's next pass past
our planet. So that it misses.

If it comes back on the same path in the future, we can nudge it
again.

[Dimensional Traveler]

Okay, there's some really bad English here. I'm not sure what Victor
Vasylyev was trying to say. Nitpick: If you change an asteroid's orbit
enough to miss a planet (or, frankly, AT ALL) when it was otherwise
going to hit it, you _HAVE_ changed its orbit for all eternity. Now,
that NEW orbit may intersect your planet next time when it wouldn't have
hit it on the next orbit before you nudged it. (At least partially
because it would have smacked into your planet and no longer be around
to have an orbit but details, details. :P ) In that situation ya,
you're going have to slap it around again.

[Scott Lurndal]

I believe Valylyev was suggesting that the moonlet was not solid,
but rather had a shell of debris (cocoon) orbiting a smaller core. I can't
reconcile that idea with the photographs just prior to impact,
or the 10km trail of debris which is unlikely to re-coalesce
with the damaged moonlet.

[pete...@gmail.com]

I thought he was trying to suggest that the surface of the asteroid
was not uniform, with part of it darker, and invisible when ejected.
This means that the cloud could have been more spherically symmetrical.
He also suggested that it might later fall back to the Dimorphos,
negating most of the orbital change.

When I accused him of 'multiplying entities', I was suggesting that
this multi-toned approach was overly complicated; the straightforward
'most of the ejecta was from one side' is simpler, and consistent with all
the available evidence: the views of the impact from the side, and the change
in the orbit (which was much larger than it would be if the ejects was a
symmetric shell)

The suggestion that the ejecta will fall back on Dimorphos faces two problems
1. Some part of the ejecta is above escape velocity for the Dimorphos/Didymos
system, and isn't ever coming back. 2. A good deal of it will instead collide with the
much larger Didymos instead.

There's an intended followup mission in 2026 by ESA, "Hera", which will show us
what happened. I'm not expecting a big crater, I suspect a rubble pile will
settle and self-heal to some extent.

pt

[pete...@gmail.com]

On Monday, October 17, 2022 at 3:26:46 PM UTC-4, Scott Lurndal wrote:

BTW: Googling Victor Vasylyev turns up a Ukrainian astrophysicist,
along with a Russian mathematician.

pt

[Jack Bohn]

Well, there's a collaboration made in Higher Dimensions!

--
-Jack

[Paul S Person]

A nitpick to your nitpick: the person I was responding to was positing
that the orbit might change back as (in effect) the dust settled.

My point was that it wouldn't matter, so long as it missed this time.

And, clearly, you are correct: it also wouldn't matter if the new
orbit was a problem next time.

[Dimensional Traveler]

I don't see how an object could "revert" to its previous orbit after it
had been pushed into a new one absent another push.

I also don't think it is possible to have a shell of debris "orbiting"
around an asteroid. A ring, sure, but not a sphere like shell, because
different pieces would have to be orbiting at different speeds at the
same distance from the primary. Which from what I understand of physics
simply isn't possible.

[Robert Carnegie]

There is a ton of assorted space junk pieces orbiting
Earth closely in many random directions as I write.
I think we're meant to be imagining a cloud of stuff,
and not a "shell" such as an egg has.

And I haven't done the calculations, but the quantity of
stuff flying off the little asteroid evidently /has/ been
accelerated, I think.

[pete...@gmail.com]

Vlad described his hypothetical shell as 'optically dense', ie, too thick
to see through. I don't think that's stable in the long term. I expect
it would first settle into a ring, and then into a ridge on the surface, like
Iapetus.

pt

[Victor Vasylyev]

Trying to add some clarity to my founded hypothesis...
Most of abruptly formed asymmetric "cocoon" (consisting not of "dust", but of relatively large fragments - that's why it did not fly off so far! – see again 50+ seconds in https://www.nature.com/articles/d41586-022-03130-8) should have been concentrated on the side of the main component, where its attraction maximally contributed to the rebound of large fragments of the Dimorphos as loosely-bound rubble pile (such its internal structure was known and became evident after the impact). This asymmetry could shift the center of the summarised "albedo spot" (determined owing to eclipses) towards a shorter orbit relative to the mass center of the parent body. As a result, when interpreting, you can get the illusion of a change in the asteroid's orbit instead of its true change. Up to "cocoon" dissipation and/or fallback.

[pete...@gmail.com]

Why do you think the change in the orbit is an illusion?

The stated change is not based on short term observation, but over two weeks of
consistent measurements. The methodology was explained at the follow-up NASA briefing:
https://youtu.be/tuGMST5vgP4?t=1828

All the data is consistent with the probe hitting, and kicking out a large quantity of debris
(now stretched over 1000s of km, and growing), creating a permanent change in Dimorphos' orbit
around Didymous. This data has held up over more than two weeks of observations.

I still don't quite understand your hypothesis. But can you give a reason why it should be
considered? What is the evidence supporting it? (Your URL doesn't work).

pt

[Scott Lurndal]

"pete...@gmail.com" <pete...@gmail.com> writes:
>On Wednesday, October 19, 2022 at 5:20:24 AM UTC-4, Victor Vasylyev wrote:

>> On Wednesday, October 19, 2022 at 12:42:23 AM UTC+3, pete...@gmail.com wr=
>ote:=20

>> Trying to add some clarity to my founded hypothesis...=20
>> Most of abruptly formed asymmetric "cocoon" (consisting not of "dust", bu=
>t of relatively large fragments - that's why it did not fly off so far! =E2=
>=80=93 see again 50+ seconds in https://www.nature.com/articles/d41586-022-=
>03130-8) should have been concentrated on the side of the main component, w=
>here its attraction maximally contributed to the rebound of large fragments=
> of the Dimorphos as loosely-bound rubble pile (such its internal structure=
> was known and became evident after the impact). This asymmetry could shift=
> the center of the summarised "albedo spot" (determined owing to eclipses) =
>towards a shorter orbit relative to the mass center of the parent body. As =
>a result, when interpreting, you can get the illusion of a change in the as=
>teroid's orbit instead of its true change. Up to "cocoon" dissipation and/o=

>r fallback.
>
>Why do you think the change in the orbit is an illusion?
>

>The stated change is not based on short term observation, but over two week=
>s of
>consistent measurements. The methodology was explained at the follow-up NA=
>SA briefing:
>https://youtu.be/tuGMST5vgP4?t=3D1828
>
>All the data is consistent with the probe hitting, and kicking out a large =
>quantity of debris=20
>(now stretched over 1000s of km, and growing), creating a permanent change =
>in Dimorphos' orbit=20
>around Didymous. This data has held up over more than two weeks of observat=
>ions.
>
>I still don't quite understand your hypothesis. But can you give a reason w=

>hy it should be
>considered? What is the evidence supporting it? (Your URL doesn't work).
>
>pt
>

Works for me. The silly 'flowed' format breaks the URL.


https://www.nature.com/articles/d41586-022-03130-8

It's an editorial, entitled:

"Deflecting asteroids is not enough - we need to know when they approach"

[Dimensional Traveler]

Well the truth of that title strikes me as obvious since we can't
deflect them or even know we need to if we don't know they are
approaching. That's why NASA has been systematically mapping as many of
the Earth-crossing objects as they can.

[Paul S Person]

On Tue, 18 Oct 2022 11:53:39 -0700, Dimensional Traveler

Perhaps you should take it up with the person who made the claim.

Here's a clue: it wasn't me.

[pete...@gmail.com]

> "Deflecting asteroids is not enough - we need to know when they approach.j

I really don't want to return to the 'formatting' discussion. People should
break lines at 60 characters.

Victor's post implied that there was a video at the URL, and we should
look 50 seconds in. I can't find a video on the page.

pt

[Dimensional Traveler]

Comments weren't aimed at you in particular. Just discussing the
subject, apologies if it seemed personal.

[Victor Vasylyev]

I will give a few specific arguments that could cause the illusion of changing the orbit:
1. The abrupt occurrence of a "meteoroid cocoon" from relatively large fragments of Dimorphos did not lead to their distant expansion. On the previously cited video https://www.youtube.com/watch?v=bfqVqOl9S9w (sorry, an another link was given in the previous post by mistake), you can see that the summarised albedo spot "Dimorphos + сocoon" approximately doubled in about a second in the direction perpendicular to its orbit. During the next 10 seconds, its dimensions practically did not change, in contrast to the ejection dust flow.
2. Measurements of the orbital parameters were, of necessity, made by an indirect method, that is, by the position of the asteroid's shadow. This method is sensitive only to optical quantities (albedo), which in this case did not characterize the position of the center of mass of Dimorrphos.
3. Estimates show that the expansion of the summarised albedo spot "Dimorphos + cocoon" of about half of its asteroid size towards the main component is sufficient to distort the real orbital velocity of the asteroid's center of mass by the value given in the NASA results.
4. During several weeks of measurements, the configuration of the summarised albedo spot, most likely, did not change. Therefore, multiple fixation of the position of the summarised albedo spot "Dimorphos + cocoon" is not an argument in favor of the reality of the interpretation. For final conclusions, more long-term observations are needed - up to "cocoon" dissipation, transformation and/or fallback.
5. Impulse transmission to Dimorphos (exactly as a whole!) is impossible either directly by impact of a small impactor or by material ejection. This follows from the laws of shock wave physics (absolutely inelastic impact) when applied to a loosely-bound rubble pile target.

[pete...@gmail.com]

Do you actually understand how occultation timings are used to demonstrate the
orbit has changed?

I'm sorry, but I'm coming to the conclusion that I can no longer take you seriously.

pt

[Victor Vasylyev]

It is probably that my hypothesis today does not look convincing enough. Future observations will clarify the situation. But the probability that a PhD in astrophysics with many years of university teaching experience does not understand the method of orbital period, determining from observations of the mutual occultations of binary system components, looks less than the probability of impulse transfer in a perfectly inelastic collision ...
To complete the discussion, I can recommend my article on improved approach to the to the more effective asteroid deflection:
https://link.springer.com/article/10.1007%2Fs11038-012-9410-2
as well as:
https://en.wikipedia.org/wiki/Asteroid_impact_avoidance#Focused_solar_energy

[pete...@gmail.com]

In that case, I'll continue to pay attention. Understand that this newsgroup has, over the years,
received many posts from people pushing non-scientific fringe theories, much more than actual
experts.

What predictions can you make for the Didimous/Dimorphos system that would support your
hypothesis?

pt

[pete...@gmail.com]

I've gone back and reread your post.

I've watched the video you linked, with your explanation in mind.

Will you do me the favor of watching the NASA follow-up briefing?
https://www.youtube.com/watch?v=tuGMST5vgP4&t=1828s
You only need watch for 5-6 minutes.

The presenter gives two independent sets of observations.

1. Dimorphos at one point in its orbit passes into Didymous's shadow, and at another point,
casts its own shadow on Didymous. Even if a ground based telescope can't resolve the two
bodies from each other, it *can* observe the change in light level caused by these eclipses.

This was the technique used before the impact to nail down where the two bodies were in
regard to each other, so the probe could adjust its speed and direction to hit Dimorphos
head on. Many telescopes observed the dips in the light curve afterwards, and their timing
was entirely consistent with a 35 minute shortening of the orbital period.

2. Direct radar observation from Goldstone and another site *could* resolve the two
bodies, and the position of Dimorphos relative to Did ymous was also consistent with
a shortened orbit.

I'm curious how you dismiss this evidence. Your argument that 'momentum transfer could
not occur' seems to be incorrect.

pt

[Quadibloc]

On Wednesday, October 19, 2022 at 2:55:54 PM UTC-6, Victor Vasylyev wrote:

> 5. Impulse transmission to Dimorphos (exactly as a whole!) is impossible either directly by impact of a small impactor or by material ejection. This follows from the laws of shock wave physics (absolutely inelastic impact) when applied to a loosely-bound rubble pile target.

If by "impulse", you mean momentum, since momentum is conserved, the difference between inelastic
impact and elastic impact is that the momentum transferred is not _doubled_ by the impactor bouncing
off in the opposite direction. At least for a rigid body.
But we don't have a rigid body, as you note. However, for the DART spacecraft to transfer no
momentum to the asteroid, the requirement would be that its own momentum would be
unchanged by the collision. Which means it would have to go through the asteroid and come
out on the other side. Preferably undamaged.
So I am puzzled by your claims, although it is certainly possible I have misunderstood them.
In the perfectly elastic case, we have the situation where both momentum and energy are
conserved. This constrains the result of a collision, and leads to the toy where a row of metal
balls are suspended from a framework. With inelastic collisions, energy is turned into heat,
but momentum remains strictly conserved. This is simple physics, and while it can have more
complex consequences, more complex physics (i.e. the physics of shock waves) can't come
back and overrule the basic facts upon which it is built.

John Savard

[Victor Vasylyev]

To transfer the momentum from a small impactor (as well as from the accompanying ejection of material) to a big target as a whole, the arising shock wave must pass to the opposite boundary, be reflected with repolarization, and return to the impact zone with some damping. But for target like loose piles of gravel filled by rocks and dust, this is basically impossible. Since the shock wave will die out much earlier due to dissipation in the huge local transition zones of complex-shaped solid fragments with vacuum or dust cavities. Therefore, in fact, all the kinetic energy during the impact turns into heating and position redistribution of the fragments, which are closest to the impact zone. Wherein the momentum is of course conserved.

[pete...@gmail.com]

You've said that repeatedly. I believe I understand your argument.

Yet the observational data, both of timings of dips in the light curve, and direct observation
of Didymous and Dimorpos by radar, are in agreement that the orbit was shortened by the
impact, and it remains shortened weeks later.

In science, when observation and theory are in conflict, observation wins. The onus is
on you to explain the observations in a way consistent with your theory.

Did you watch the video I linked above? You only need to watch 5-6 minutes.
https://www.youtube.com/watch?v=tuGMST5vgP4&t=1828s

Pt

[pete...@gmail.com]

On Friday, October 21, 2022 at 2:45:44 PM UTC-4, Victor Vasylyev wrote:

To add to my other response, I suggest you consider other mechanisms that
could create a back jet of debris. The impact was the equivalent of several tons of TNT
The impactor was in no way streamlined, dense, or hardened, and traveling at >6 kps.
It is going to push stuff out of the way, hard. The jostling of fragments against each other
will certainly result in many being ejected to the rear, and Dimorphos' miniscule escape
velocity (< 10 cm/s) means most will never return.

Pt

[Dorothy J Heydt]

In article <6c9747c9-6a5d-496d...@googlegroups.com>,

(Hal Heydt)
Has anyone managed to determine the materials in the ejected jet?
Is it possible that there are volatile ices under the exposed
surface that would have been vaporized from the heat of impact
and increased the effective thrust from resulting ejected
material?

[Victor Vasylyev]

Of course, I carefully watched the NASA briefing, as well as everything that has been published on this topic. The information contained there does not negate the fact that the transfer of momentum at a given impact was impossible, in accordance with the physics of shock waves (see post above). Therefore, there is a need for an alternative interpretation of indirect observations of the position of Dimorphos, a variant of which I proposed.
I repeat that observations (both eclipsing and radar) recorded not the center of mass of Dimorphos, but the position of an asymmetrical spot-cocoon (total mass) created by both the asteroid and its near-surface ejected fragments. During the first weeks, this spot was dynamic, hiding the true position of the center of mass. This situation is similar to squid which distract attacking predators by ejecting a cloud of ink, giving themselves an opportunity to temporarily hide your actual location. So, there is no need to draw final conclusions yet, but wait for the dissipation, transformation and/or fallback of summarised cocoon.

[pete...@gmail.com]

I don't find it plausible that an 'asymmetrical spot cocoon' from a 160 meter object can create a
radar Illusion that it's on the opposite side of Didymous than it would be if the impact
had not occurred.

Nor do I find it plausible that this cocoon can explain the changed timing of the dips
in the light curve.

How long should we wait?

Pt

[Paul S Person]

I was going to say something about his statement, but then I realized
that that statement, itself, doesn't actually /say/ that he believes
the target to be a "loose pile of gravel".

The argument, itself, would seem to rule that out, given the observed
results.

But what do I know? I am not an astrophysicist. Then again, this guy
is (apparently) not part of the team evaluating the mission, and so
may not have all the data. Perhaps he should offer his services to
them.

And he doesn't seem to have ever explained why it /matters/ if the
nudged object resumes its orbit /if in the meantime it misses the
Earth/. Changing the orbit permanently is not the point of the
exercise; changing it enough (and long enough) to miss the Earth is.

Which, since there are a lot of space rocks out there with
(apparently) varying degrees of solidity, makes the ability to change
the orbit of /this/ one a "proof of concept" success. Even if it
eventually changes back.

And I don't want to hear about how it won't change back. I really
don't care if it does or not. The ability to get a large rock (however
dense or undense) heading to our planet to miss is all I am interested
in.

>Did you watch the video I linked above? You only need to watch 5-6 minutes.
>https://www.youtube.com/watch?v=tuGMST5vgP4&t=1828s

[Paul S Person]

This sounds a lot like saying that the observed facts don't agree with
your theory, so they must be something else.

[Robert Carnegie]

Earth is over 12,500 km wide and it has gravity,
so you want a really good miss. And you don't
want to have to /keep/ pushing it away each time.
What if it comes when Donald Trump is President
and he thinks he can wave it away with a Sharpie?

Having said that... After you convert the expected
impact to a near miss... the thing goes away, and then,
because of orbital mechanics, it comes back. So maybe
you have to deal with it again for that reason.

[Scott Lurndal]

Robert Carnegie <rja.ca...@excite.com> writes:
>On Saturday, 22 October 2022 at 17:04:27 UTC+1, Paul S Person wrote:

>> On Fri, 21 Oct 2022 19:50:11 -0700 (PDT), "pete...@gmail.com"=20
>> <pete...@gmail.com> wrote:=20
>>=20

>>=20
>> And I don't want to hear about how it won't change back. I really=20
>> don't care if it does or not. The ability to get a large rock (however=20
>> dense or undense) heading to our planet to miss is all I am interested=20

>> in.
>
>Earth is over 12,500 km wide and it has gravity,
>so you want a really good miss.

It is also moving at 30km/s. A very small (on astronomical
scales) target moving very fast; one does not need to alter
the velocity (or velocity vector) of a potentially intersecting
object by very much to effect a miss.

[Paul S Person]

As to that hurricane path map, I agree that Trump's Sharpie was a very
dumb idea.

Nonetheless, if you find it online and examine it closely, you will
see that the sharpie expanded the expected possible path of the
hurricane into the next State.

That doesn't sound too unreasonable. What else would you expect it to
do when it reached the border on the map but keep on going into the
next State? Teleport to Winipeg? Stop on a dime?

The /real/ problem, as I recall understanding it at the time, was that
the map he was using was an /old/ map, the implication being that a
more recent map would not have had those possible paths on it but
rather a path closer to the path actually taken.

The underlying problem, of course, was/is that he is Donald Trump. Who
appears to be having a very hard time adjusting to the realities of
life, now that they have come to call on him.

[pete...@gmail.com]

I wonder if the problem is that you're assuming the shock wave has to traverse the entire width of
Dimorphos before reflecting back. The asteroid seems to be made of many fragments, which are
not bound together. This makes it difficult for a shockwave to propagate from one fragment to
another, which means that a lot of energy is reflected back at the edge of each fragment. That may
be what allows a jet of debris even in loosely bound "dust bunny"

Pt

[Quadibloc]

This doesn't correspond to what I remember from what I saw at the
time, but my memory has been faulty before.

I know that I joked at the time that if his map inspired more people
to *pray* about the hurricane, then the additional power of all
those prayers might have averted disaster!

John Savard