The asteroid NASA will slam into in September is right where scientists expected...

[Fred Bloggs]

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range! It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

 

[Anthony William Sloman]

On Monday, August 29, 2022 at 10:48:20 PM UTC+10, Fred Bloggs wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range! It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

\"Scenic route\"? 6.7 million miles isn\'t all that far away as astronomical distances go, and ten months would mean 930 miles per hour, which isn\'t all that slow, and has probably got more to do with the orbit around the sun which would get it to the right place at the right time to hit Dimorphos.

--
Bill Sloman, Sydney

 

[Fred Bloggs]

On Monday, August 29, 2022 at 9:32:44 AM UTC-4, bill....@ieee.org wrote:

On Monday, August 29, 2022 at 10:48:20 PM UTC+10, Fred Bloggs wrote:
Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range! It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit
\"Scenic route\"? 6.7 million miles isn\'t all that far away as astronomical distances go, and ten months would mean 930 miles per hour, which isn\'t all that slow, and has probably got more to do with the orbit around the sun which would get it to the right place at the right time to hit Dimorphos.

930 is a snails pace for space travel, it could easily do 50,000. It might have to do with making allowance for the response times to corrections at the last minute for a direct hit. Propagation time of EM to Earth will be 37 seconds. I don\'t think they\'re relying on open ended trajectory measurements to make an exacting impact like this- it will need human intervention at some point.

--
Bill Sloman, Sydney

 

[server]

On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

>Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!

There is probably terminal guidance involved.

It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

Sounds like an interesting and expensive way to verify Newtonian
mechanics.

 

[Fred Bloggs]

On Monday, August 29, 2022 at 10:59:11 AM UTC-4, jla...@highlandsniptechnology.com wrote:

On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit
Sounds like an interesting and expensive way to verify Newtonian
mechanics.

LOL- the main result they will be measuring is the degree of change in the orbit of that moon. They will discern this from change in orbital time period which they expect to shorten by 2 minutes.

 

[Anthony William Sloman]

On Tuesday, August 30, 2022 at 12:59:11 AM UTC+10, jla...@highlandsniptechnology.com wrote:

On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

Sounds like an interesting and expensive way to verify Newtonian
mechanics.

The details of the collision may be interesting. If the smaller asteroid turned out to be soft and fluffy, there might not be much momentum transfer at all.

--
Bill Sloman, Sydney

 

[Martin Brown]

On 29/08/2022 15:59, jlarkin@highlandsniptechnology.com wrote:

On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!

There is probably terminal guidance involved.

Almost certainly but their course by dead reckoning is spot on. That is
quite a remarkable achievement. There are a lot of perturbations.

It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

Sounds like an interesting and expensive way to verify Newtonian
mechanics.

The intention is to see what happens when you smash into a small
asteroid with a fast kinetic energy round. Outcomes are hard to predict.
If it is rocky or iron then it will pretty much bounce off but if it is
a dirty snowball or weakly bound then it might fragment the thing.

One other minor point the target will be 6.7 million miles from Earth
when it gets intercepted but the transfer orbit to reach that
interception point from an Earth launch is considerably greater.

It will hit Dimorphous at 4 miles/sec if all goes to plan. See:

https://blogs.nasa.gov/dart/2021/11/24/nasa-spacex-launch-dart-first-planetary-defense-test-mission/

It is using a xenon ion thruster.

--
Regards,
Martin Brown

 

[server]

On Mon, 29 Aug 2022 08:08:23 -0700 (PDT), Fred Bloggs
<bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, August 29, 2022 at 10:59:11 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit
Sounds like an interesting and expensive way to verify Newtonian
mechanics.

LOL- the main result they will be measuring is the degree of change in the orbit of that moon. They will discern this from change in orbital time period which they expect to shorten by 2 minutes.

Which of course couldn\'t have been calculated.

Another expensive NASA stunt.

 

[Fred Bloggs]

On Monday, August 29, 2022 at 11:15:18 AM UTC-4, bill....@ieee.org wrote:

On Tuesday, August 30, 2022 at 12:59:11 AM UTC+10, jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect..

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

Sounds like an interesting and expensive way to verify Newtonian
mechanics.
The details of the collision may be interesting. If the smaller asteroid turned out to be soft and fluffy, there might not be much momentum transfer at all.

Similar to EM waves, if the surface texture is large compared to the size of the DART, then however it fragments, an unknown fraction will not be at a steep enough angle to penetrate and are deflected. Deflection reduces the momentum transferred to the target, I would think.

--
Bill Sloman, Sydney

 

[Fred Bloggs]

On Monday, August 29, 2022 at 11:20:36 AM UTC-4, Martin Brown wrote:

On 29/08/2022 15:59, jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!

There is probably terminal guidance involved.
Almost certainly but their course by dead reckoning is spot on. That is
quite a remarkable achievement. There are a lot of perturbations.


It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

Sounds like an interesting and expensive way to verify Newtonian
mechanics.
The intention is to see what happens when you smash into a small
asteroid with a fast kinetic energy round. Outcomes are hard to predict.
If it is rocky or iron then it will pretty much bounce off but if it is
a dirty snowball or weakly bound then it might fragment the thing.

One other minor point the target will be 6.7 million miles from Earth
when it gets intercepted but the transfer orbit to reach that
interception point from an Earth launch is considerably greater.

It will hit Dimorphous at 4 miles/sec if all goes to plan. See:

https://blogs.nasa.gov/dart/2021/11/24/nasa-spacex-launch-dart-first-planetary-defense-test-mission/

It is using a xenon ion thruster.

INMARSAT used a 500kW (IIRC) ion thruster to put their latest and greatest communications satellite in geostationary orbit, it took them 7 months to park that thing.

--
Regards,
Martin Brown

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Mon, 29 Aug 2022 08:08:23 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, August 29, 2022 at 10:59:11 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7
million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the
rendezvous. That seems like really long time, it must have
taken the scenic route, probably to accumulate the speed of
travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit


Sounds like an interesting and expensive way to verify Newtonian
mechanics.

LOL- the main result they will be measuring is the degree of change
in the orbit of that moon. They will discern this from change in
orbital time period which they expect to shorten by 2 minutes.

Which of course couldn\'t have been calculated.

Another expensive NASA stunt.

It\'s a long shot, but it might someday be necessary to move an
Earth-crossing asteroid to avoid a nasty impact.

AFAIK nobody knows the mechanical details of how one of those is likely
to react to a high-speed impact. Having one break apart might exchange
a single 1000-MT impact for 500 1-MT impacts.

That would not be an improvement.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[ehsjr]

On 8/29/2022 9:32 AM, Anthony William Sloman wrote:

On Monday, August 29, 2022 at 10:48:20 PM UTC+10, Fred Bloggs wrote:
Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range! It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

\"Scenic route\"? 6.7 million miles isn\'t all that far away as astronomical distances > > go, and ten months would mean 930 miles per hour, which isn\'t all that slow,

\"Isn\'t all that slow\"? They had to *slow it down* by over 24,000 mph
to get it down to 930 mph - assuming your number is correct.

Ed

and has probably got more to do with the orbit around the sun which would get it to the > right place at the right time to hit Dimorphos.

 

[John Larkin]

On Mon, 29 Aug 2022 12:11:39 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

jlarkin@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 08:08:23 -0700 (PDT), Fred Bloggs
bloggs.fredbloggs.fred@gmail.com> wrote:

On Monday, August 29, 2022 at 10:59:11 AM UTC-4,
jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7
million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the
rendezvous. That seems like really long time, it must have
taken the scenic route, probably to accumulate the speed of
travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit


Sounds like an interesting and expensive way to verify Newtonian
mechanics.

LOL- the main result they will be measuring is the degree of change
in the orbit of that moon. They will discern this from change in
orbital time period which they expect to shorten by 2 minutes.

Which of course couldn\'t have been calculated.

Another expensive NASA stunt.


It\'s a long shot, but it might someday be necessary to move an
Earth-crossing asteroid to avoid a nasty impact.

The ISS and nukes - both liabilities now - could be combined into an
asteroid defense system.

AFAIK nobody knows the mechanical details of how one of those is likely
to react to a high-speed impact. Having one break apart might exchange
a single 1000-MT impact for 500 1-MT impacts.

That would not be an improvement.

Cheers

Phil Hobbs

 

[Phil Hobbs]

Fred Bloggs wrote:

On Monday, August 29, 2022 at 11:15:18 AM UTC-4, bill....@ieee.org
wrote:
On Tuesday, August 30, 2022 at 12:59:11 AM UTC+10,
jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7
million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the
rendezvous. That seems like really long time, it must have
taken the scenic route, probably to accumulate the speed of
travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit




Sounds like an interesting and expensive way to verify Newtonian
mechanics.
The details of the collision may be interesting. If the smaller
asteroid turned out to be soft and fluffy, there might not be much
momentum transfer at all.

Similar to EM waves, if the surface texture is large compared to the
size of the DART, then however it fragments, an unknown fraction
will not be at a steep enough angle to penetrate and are deflected.
Deflection reduces the momentum transferred to the target, I would
think.

If it has peaks, they have adjacent valleys. If the probe were to hit
perpendicular to the surface and bounce off elastically, the momentum
transfer would be doubled.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Fred Bloggs]

On Monday, August 29, 2022 at 3:19:15 PM UTC-4, Phil Hobbs wrote:

Fred Bloggs wrote:
On Monday, August 29, 2022 at 11:15:18 AM UTC-4, bill....@ieee.org
wrote:
On Tuesday, August 30, 2022 at 12:59:11 AM UTC+10,
jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7
million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the
rendezvous. That seems like really long time, it must have
taken the scenic route, probably to accumulate the speed of
travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit




Sounds like an interesting and expensive way to verify Newtonian
mechanics.
The details of the collision may be interesting. If the smaller
asteroid turned out to be soft and fluffy, there might not be much
momentum transfer at all.

Similar to EM waves, if the surface texture is large compared to the
size of the DART, then however it fragments, an unknown fraction
will not be at a steep enough angle to penetrate and are deflected.
Deflection reduces the momentum transferred to the target, I would
think.
If it has peaks, they have adjacent valleys. If the probe were to hit
perpendicular to the surface and bounce off elastically, the momentum
transfer would be doubled.

Three hundred years later and he\'s still making invaluable contributions:

https://en.wikipedia.org/wiki/Impact_depth

It looks like the most effective way to get 100% transfer of momentum, and a hard projectile won\'t be deterred by surface irregularities. Looks like they need to keep it at under about 700 MPH-ish for this approximation to apply. 930 MPH must be better as determined by more accurate modern calculations. It may answer the question as to why the DART speed is so slow. The hyperfast shock wave/ crater regime is not as effective as a penetration.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

Fred Bloggs wrote:

On Monday, August 29, 2022 at 3:19:15 PM UTC-4, Phil Hobbs wrote:
Fred Bloggs wrote:
On Monday, August 29, 2022 at 11:15:18 AM UTC-4,
bill....@ieee.org wrote:
On Tuesday, August 30, 2022 at 12:59:11 AM UTC+10,
jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at
6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make
the rendezvous. That seems like really long time, it must
have taken the scenic route, probably to accumulate the
speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit






Sounds like an interesting and expensive way to verify Newtonian
mechanics.
The details of the collision may be interesting. If the
smaller asteroid turned out to be soft and fluffy, there might
not be much momentum transfer at all.

Similar to EM waves, if the surface texture is large compared to
the size of the DART, then however it fragments, an unknown
fraction will not be at a steep enough angle to penetrate and are
deflected. Deflection reduces the momentum transferred to the
target, I would think.
If it has peaks, they have adjacent valleys. If the probe were to
hit perpendicular to the surface and bounce off elastically, the
momentum transfer would be doubled.

Three hundred years later and he\'s still making invaluable
contributions:

https://en.wikipedia.org/wiki/Impact_depth

It looks like the most effective way to get 100% transfer of
momentum, and a hard projectile won\'t be deterred by surface
irregularities. Looks like they need to keep it at under about 700
MPH-ish for this approximation to apply. 930 MPH must be better as
determined by more accurate modern calculations. It may answer the
question as to why the DART speed is so slow. The hyperfast shock
wave/ crater regime is not as effective as a penetration.

Crapola. More momentum will always be better. Can you really envisage
a situation where the same mass, impacting faster from the same given
direction, will cause _less_ of a course change? If it\'s delta-v you
want, hitting it harder will always give you more. 100% transfer of 1%
of the possible momentum is not a win.

It really ain\'t that complicated. Anything ejected back towards the
general direction the impactor arrived from _increases_ the delta-V
applied to the asteroid, which (other things being equal) is a win.

The thing we care about in orbital corrections is momentum, not energy.
The energy required for a given delta-V varies all over the place
depending on where in the orbit you are, but the momentum for a given
delta-V doesn\'t.

For orbital transfers, you want to burn at periapsis to change the major
axis of the orbit, and at apoapsis to circularize.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Anthony William Sloman]

On Tuesday, August 30, 2022 at 1:54:48 AM UTC+10, jla...@highlandsniptechnology.com wrote:

On Mon, 29 Aug 2022 08:08:23 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

On Monday, August 29, 2022 at 10:59:11 AM UTC-4, jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit
Sounds like an interesting and expensive way to verify Newtonian
mechanics.

LOL- the main result they will be measuring is the degree of change in the orbit of that moon. They will discern this from change in orbital time period which they expect to shorten by 2 minutes.

Which of course couldn\'t have been calculated.

If you knew the composition and structure of the smaller asteroid. John Larkin clearly thinks he does, if he can be said to think.

> Another expensive NASA stunt.

Another unjustified slur from John Larkin who thinks his designs are insanely good. He may be be right about the insanity.

--
Bill Sloman, Sydney

 

[Anthony William Sloman]

On Tuesday, August 30, 2022 at 2:17:00 AM UTC+10, ehsjr wrote:

On 8/29/2022 9:32 AM, Anthony William Sloman wrote:
On Monday, August 29, 2022 at 10:48:20 PM UTC+10, Fred Bloggs wrote:
Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range! It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

\"Scenic route\"? 6.7 million miles isn\'t all that far away as astronomical distances go, and ten months would mean 930 miles per hour, which isn\'t all that slow, and has probably got more to do with the orbit around the sun which would get it to the > right place at the right time to hit Dimorphos.

\"Isn\'t all that slow\"? They had to *slow it down* by over 24,000 mph
to get it down to 930 mph - assuming your number is correct.

My number is just 6.7 million miles divided by ten months.

The escape velocity from earth is 25,000 mph. The actual velocities along DART\'s path to the target will be a lot less than that over most of the path - the earth\'s gravity will do most of the deceleration. I was just being satirical about Fred\'s choice of words.

--
Bill Sloman, Sydney

 

[Fred Bloggs]

On Monday, August 29, 2022 at 9:42:12 PM UTC-4, Phil Hobbs wrote:

Fred Bloggs wrote:
On Monday, August 29, 2022 at 3:19:15 PM UTC-4, Phil Hobbs wrote:
Fred Bloggs wrote:
On Monday, August 29, 2022 at 11:15:18 AM UTC-4,
bill....@ieee.org wrote:
On Tuesday, August 30, 2022 at 12:59:11 AM UTC+10,
jla...@highlandsniptechnology.com wrote:
On Mon, 29 Aug 2022 05:48:15 -0700 (PDT), Fred Bloggs
bloggs.fred...@gmail.com> wrote:

Nothing short of phenomenal to hit a 560 ft wide target at
6.7 million mile range!
There is probably terminal guidance involved.
It will have taken DART almost exactly 10 months to make
the rendezvous. That seems like really long time, it must
have taken the scenic route, probably to accumulate the
speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit






Sounds like an interesting and expensive way to verify Newtonian
mechanics.
The details of the collision may be interesting. If the
smaller asteroid turned out to be soft and fluffy, there might
not be much momentum transfer at all.

Similar to EM waves, if the surface texture is large compared to
the size of the DART, then however it fragments, an unknown
fraction will not be at a steep enough angle to penetrate and are
deflected. Deflection reduces the momentum transferred to the
target, I would think.
If it has peaks, they have adjacent valleys. If the probe were to
hit perpendicular to the surface and bounce off elastically, the
momentum transfer would be doubled.

Three hundred years later and he\'s still making invaluable
contributions:

https://en.wikipedia.org/wiki/Impact_depth

It looks like the most effective way to get 100% transfer of
momentum, and a hard projectile won\'t be deterred by surface
irregularities. Looks like they need to keep it at under about 700
MPH-ish for this approximation to apply. 930 MPH must be better as
determined by more accurate modern calculations. It may answer the
question as to why the DART speed is so slow. The hyperfast shock
wave/ crater regime is not as effective as a penetration.
Crapola. More momentum will always be better. Can you really envisage
a situation where the same mass, impacting faster from the same given
direction, will cause _less_ of a course change? If it\'s delta-v you
want, hitting it harder will always give you more. 100% transfer of 1%
of the possible momentum is not a win.

It really ain\'t that complicated. Anything ejected back towards the
general direction the impactor arrived from _increases_ the delta-V
applied to the asteroid, which (other things being equal) is a win.

The thing we care about in orbital corrections is momentum, not energy.
The energy required for a given delta-V varies all over the place
depending on where in the orbit you are, but the momentum for a given
delta-V doesn\'t.

For orbital transfers, you want to burn at periapsis to change the major
axis of the orbit, and at apoapsis to circularize.
Cheers

I realized that right after I stumbled across it. The only other explanation for the slower impact speed is to achieve a a better controlled Newtonian impact penetration yielding a momentum transfer known with much greater precision than a high speed slam-bam type of collision and all of its indeterminate energy dissipation forms- light, heat, kinetic. They\'re not looking to crack the asteroid into pieces, they\'re looking to give it a little nudge.

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Jasen Betts]

On 2022-08-29, ehsjr <ehsjr@verizon.net> wrote:

On 8/29/2022 9:32 AM, Anthony William Sloman wrote:
On Monday, August 29, 2022 at 10:48:20 PM UTC+10, Fred Bloggs wrote:
Nothing short of phenomenal to hit a 560 ft wide target at 6.7 million mile range! It will have taken DART almost exactly 10 months to make the rendezvous. That seems like really long time, it must have taken the scenic route, probably to accumulate the speed of travel it needs to have a kinetic effect.

https://www.space.com/dart-asteroid-mission-preparatory-observations-didymos-orbit

\"Scenic route\"? 6.7 million miles isn\'t all that far away as astronomical distances > > go, and ten months would mean 930 miles per hour, which isn\'t all that slow,

\"Isn\'t all that slow\"? They had to *slow it down* by over 24,000 mph
to get it down to 930 mph - assuming your number is correct.

Climbing Earth\'s gravity well will do that.

--
Jasen.