Indian ASAT Test

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NRao
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Re: Indian ASAT Test

Theeran wrote:
NRao wrote:
a) Yes, it will land exactly into "your hand" (not accounting for wind, etc.
b) You know v and v0, so use v = v0 + at to compute t ( a= 9.8 ), then use x - x0 = v0t + 1/2at^^2 to get the height
c) yes, the verticle speed at the top will be 0. wrt to the person on the ground, whatever speed the earth is spinning at?

Ok the calc flew over my head. But common sense the ball will land to the west? With the earth rotating you will be long gone before the ball lands.

Unfortunately, physics trumps (NOT the US prez, thankfully), common sense.

Here are equ of motion (the "calc"). Hope it helps.
Last edited by NRao on 10 Apr 2019 09:18, edited 1 time in total.

Prem Kumar
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Re: Indian ASAT Test

I was also intrigued by the EOvideo grab of the ASAT missile knocking out Microsat. This is the other video grab - not the IIR image taken from the ASAT missile itself. Where was this EO camera positioned? If its from the ground, that's an impressive zoom!

Maybe the Cartosat camera was repurposed for this?

UB: to answer your question, we just showed the world that we can take a high resolution video of an ASAT kill (possibly from the ground). Of course, not a centimeter sized hittile. But still a very impressive capability!
Last edited by Prem Kumar on 10 Apr 2019 09:19, edited 1 time in total.

UlanBatori
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Re: Indian ASAT Test

In that case it was tracked with a dedicated camera. Still looks pretty fuzzy. You just don't have that sort of resolution when you are looking at wide swaths of sky in 3-D.
I suppose if an astronomical telescope (huge dish) is used, one can see quite clearly, if one has fast tracking. But the tradeoff is between resolution and overall size of the volume scanned.
Last edited by UlanBatori on 10 Apr 2019 09:23, edited 1 time in total.

Prem Kumar
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Re: Indian ASAT Test

Correct. So, quite possibly, resolution in scan mode is not great but in a track mode, smaller objects can be tracked. When Khan claims he is tracking centimeter sized debris of ASAT kill, he is probably operating in track mode, because he knows where to look.

In scan mode, perhaps things can get interesting with a SAR type swath coverage, backed up by heavy duty digital signal processing to spot "anomalies"

For our ASAT test, the dedicated camera need not even track the missile, it just needs to be pointed to the "box" where we know the impact will occur. Similar to Brahmos missile test target-hitting videos. Still the resolution is impressive!

UlanBatori
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Re: Indian ASAT Test

Maybe they put a big telescope on an aircraft flying at 14000 meters. Much less atmospheric interference that way. I think in Khanistan after STS Columbia crash, COTUS mandated that no STS would return unless and until heat shield tiles had been verified to be still in place. EVA was not an option (would kill more astronauts by radiation if not other accidents) so they devised an imaging system to do this. Uses a C-130 over the Gelf de Mexico. The STS is asked to turn upside down and right side up so that the whole surface can be scanned for missing tiles. So yes, with dedicated zoom and big-\$\$ telescope many things can be done. BTW, they also used those cameras to do imaging in other parts of the spectrum, so those data have now disappeared from public view. So much for "NASA openness".

Prem Kumar
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Re: Indian ASAT Test

Very interesting!

Our investments in deep space, tracking quasars/pulsars, sun's corona etc will all produce technologies that can be re-used. Enable deep-dekho across the EM spectrum

sanjaykumar
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Re: Indian ASAT Test

This was not a purely ballistic intercept. I find it difficult to believe microsecond accuracy is achievable over 300 km and 180 seconds flight time. Intersecting parabolas is too facile an approach. An accuracy of 1 in 5 orders of magnitude may be achievable for an orbiting satellite but accounting for variability in fuel combustion,rocket fuel pump pressurization, the effect of undefined cross winds, thermal layers in the atmosphere, the mass variation of these custom built rockets, would lead to chaotic effects that would preclude a predictable 1 in 100 000 accuracy. Indeed otherwise everyone would be doing it. The key seems to be the terminal approach feedback loops with the tracking and pointing systems. As seen in the IR pictures of the final approach the correcting cybernetics are exquisitely finally tuned, seemingly rapidly responsive. Although the response time, I am only quessing based on the displacement of the IR image and relative sizes of the images. To get a rapid response in pitch and yaw would imply they have counter reaction propulsion rockets for every action to negate the effects of inertia.

Amber G.
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Re: Indian ASAT Test

Folks, thanks to those who took time and responded to my question about throwing the "ball straight up" a few posts above. The problem is, of course. very much related - in understanding our discussion about ASAT and provides logical thinking. The orbital motions are VERY much different than parabolic trajectories of "thrown balls" one reads in high-school.

Please keep reading if interested in technical analysis and details and how this is related to ASAT but here is a spoiler answer. The ball will actually land about a kilometer away and the the velocity at the top will *not* be zero. In fact, if the velocity of the ball is little greater - like 12 Km/sec, the ball will never return. .
(I will leave the calculation for quantitative values of the answers as a problem so solve it if interested. Of course, this is standard physics - one can look up any good place for further details.

The ball returns in your hand if you live on a flat, non-spinning, earth where value of "g" remains constant no matter how high you go. The type of equations you learn in high-schools of falling body, an approximation, may be okay on a cricket field where the deflection is *very* small. But even high-speed cannons have to take earth-rotation into account. ( Look up coriolis force)

Tanaji wrote:AmberG,

Could you please provide your explanation of the physics behind ASATs as you disagree with UB?

TIA.

One of the main point behind physics is recognize the absurdities of those ideas which tries to "explain" ASAT as a "ball" going-up - waiting till sat comes etc.

Apart from the fact that many/most satellites will NEVER be "over-head" from any given point on earth. Indian geostationary sats are not visible from US) but even if they were, orbital mechanics is not a trivial silly thing.

Hope this answer some the questions here and encourage others to look up real technical details.
Last edited by Amber G. on 10 Apr 2019 11:09, edited 1 time in total.

negi
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Re: Indian ASAT Test

Indranil wrote:Even more unlikely. China has a fairly advanced DEW program. But if you use a DEW, you don't blow up a satellite.

Well there is only fleeting reference to a debris generating event near the satellite nothing more nothing less , also if there was a ASAT launch via air/surface such an event cannot go unnoticed we would have known from one or other sources by now . I don't know enough to have a firm idea however ASAT theory is a bit shaky ,another possible theory is we triggered a self destruction after the job was done because we had to lower the orbit for higher resolution imagery (sounds crazy , alright but a possibility) ? Biggest counter to ASAT theory is had it been ASAT we would have known directly/indirectly (via NOTAM notices etc) and secondly we would have publicly named China for this act , EMP/DE attack is harder to detect so it could be a possibility , I have no explanation for debris though , however I would say that one cannot 'guarantee' that there won't be a debris in case of DEW attack for it also depends on how malfunction takes place . For all we know even a meteor can be responsible for this , however if it's someone from this planet then they have some neat capabilities .
Last edited by negi on 10 Apr 2019 11:18, edited 1 time in total.

Amber G.
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Re: Indian ASAT Test

This was not a purely ballistic intercept. I find it difficult to believe microsecond accuracy is achievable over 300 km and 180 seconds flight time. Intersecting parabolas is too facile an approach. An accuracy of 1 in 5 orders of magnitude may be achievable for an orbiting satellite but accounting for variability in fuel combustion,rocket fuel pump pressurization, the effect of undefined cross winds, thermal layers in the atmosphere, the mass variation of these custom built rockets, would lead to chaotic effects that would preclude a predictable 1 in 100 000 accuracy. Indeed otherwise everyone would be doing it. The key seems to be the terminal approach feedback loops with the tracking and pointing systems. As seen in the IR pictures of the final approach the correcting cybernetics are exquisitely finally tuned, seemingly rapidly responsive. Although the response time, I am only quessing based on the displacement of the IR image and relative sizes of the images. To get a rapid response in pitch and yaw would imply they have counter reaction propulsion rockets for every action to negate the effects of inertia.

Sanjay - Feynman was great. I have actually attended his lecture and enjoyed him. I remember him (70's ?) once bringing up in a lecture for demo - precision intertial gyroscopes/accelerometers (costing millions of dollars) from some-where telling how great they were. India's ASAT has many fold better capabilities than those things.

Some of the technology and software, after Mars mission, everyone knew is great. The ASAT test is really very impressive.

One thing no one has talk about here, is orbit calculation and maneuvering to hit the target is quite complex - I guess it will need fast computers, sensors to detect, say, variation in gravitational field in real-time. It is very awe-inspiring.

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Re: Indian ASAT Test

<Poof>

Indranil
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Re: Indian ASAT Test

Amber ji,

It's a good question and I don't mind it being in this thread. It is related to understanding suborbital and orbital paths and hence very much related to ASAT and a satellite.

[[ OT ]]
However, I am not going to answer your question. Let others solve it while I share a related anecdote. Around Class IX or X, I had read this interesting story of two boys, one sitting in a train traveling at the speed of light and the other standing outside. Both are observing the time taken for a pulse of light traveling from a torch placed at the ceiling of the train, traveling downwards to reflect off a mirror on the floor and then back up to the ceiling. At that time, I did not understand why they would observe different times. I asked for an explanation from my father. His understanding of relativity was as dabba-gol as mine and so he did what any self respecting father should do. He posed an alternate question in classical physics. Suppose the train was traveling much slower but at speeds comparable to the speed of point on the earths surface. What would happen to a ball tossed straight up by a boy on the train. Does the direction of the train and longitude matter? As you can see, your question is a special case of his question. He did not know the answer, but it was fun to work it out. I remember being consumed by that question for weeks then.

Anyhow fast forward 2 years, and I was in class XI. My physics teacher in school was teaching us inertial frame of reference and noticing my inattention made me stand up to ask what would happen if I was traveling in a train and threw a ball up. I really did not like him because I thought was always trying to impress the girl I had a crush on . I replied that it depended on how fast the train was traveling, its direction and how high I could throw the ball. He did not get what I meant and first ridiculed me. Then came my chance to shine. He did not let finish my explanation, but he never made an example out of me again. None the less, nobody got the girl.
[[ END OT ]]

Now, that I have shared my stupid story, may I ask you and UB ji to stop this stupid side swiping at each other. It is really way below both your credentials and further below your real selves.

UlanBatori
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Re: Indian ASAT Test

Since v r into this and speculation on The Problem is halal: The sounding rocket will not drift West. If anything it will drift East.

While I am only a humble yak herder, my evil 6th coujin (thrice removed by polis) studied in the Balakot Madarssa under Mullah Majeed Azhar (pbuh) and was sent across the LOC. He threw his aam-Laxman Mark 666 grenade, but unfortunately it went westwards instead of eastwards so it hit the ISI Brigadier standing there beeing. Fortunately it was Made In USA and would not go East of LOC or explode, but Prigadier had bad damage to both front and back of uniform pants. However my coujin escaped the Indian polis and registered in Srinagar University in Ore-Betel Mechanics to better understand this very problem and operate MANPADS in future. So here is his explanation, apologies for the pingreji because it comes directly from him.
When raakeet eej launched, it haj a radial acjelerashun w.r.t. Earth center, but also a tanjenshul velocity corresponding to apout Mach 1.36 @ sea-level. Eastwards. Because it was sitting on Earth. As it goes up, the atmosphere of Earth is also moving with the Earth, and over 1,732,000,000 years since Earth ishtarted spinning, the Atmosphere has come to equilbrium with the solid/liquid Earth surface and itself, the mean "shiyar" eej zerros, so it eej moving like "Saaleed Body Rotation" (Imagine Gola Musharraf rotating) about Earth's center.
As someone posted, for a 300km altitude, it drifts about 0.5 km (Oooooh!!! that eej an error worth 95 lashes @ Balakot Madarssa).

BUT.. at Binori Madarssa he larned something called AERODYNAMIC DRAG. Not taught in Little Jihadi Montessori school pissiks.

As the radius to Earth's center increases (raakeet eej rijing) the Saaleed Baady rotation of the atmosphere means that there is increajing wind speed directed EASTwards w.r.t. raakeet.

Raakeet eej TFTA, slender and long like (never mind). It eej like cylinder in crass flow. Coepheejient -e- Drag oph nearly 1. Put phortunately air denjity decreases with height aj wind speed increejes. So this pushes the raakeet back towards the East but only partly: it is still drifting west of the launch site. So now the error may become, say 0.5 km overall, unless it is at night and there is a land breej coming in from the West. So only 10 lashes for the Error at Balakot Madarssa.

Or monsoon winds blowing north-east could blow the thing off by 5 miles. This error is FAAAR more than any due to the Earth's rotation, which is why the whole "debate" is beyond silly.

To a yak standing on the ground in Juhu from where the raakeet was launched, that will still look directly overhead. Dung falling from there will probably hit right in the face or be scattered over a square kilometer.

Assuming raakeet-jehadi is smart, the raakeet will be stable, so this wind drag will not cause any TILT of the nose, just pushes raakeet sideways.

******************

BUT... that eej peefore my coujin took courses @ Srinagar U that were not taught in Binori pissiks course. There he larned something called Giyas Dynamics. Taught by Mullah Niyas. Why when a goat **ts, there is a loud noij like those heard sitting in Crore Kamandus meeting after lunch.

Apparently raakeets have something called "Thrust". This eej genarated by blowing hot gas out through a "nojjel". Nojjel haj very narrow "throat" but then expands into a wide bottom with a bum as wide as that oph Haseena Atim-Bum.

As the raakeet rijes, the Den-City decreases, so does the "brejjur". The nozzle exhaust being "soubeer- jonik", does not know that brejar eej lower at exit so it rushes out soubeer-jonik". Then, like jehadis coming through hole in LOC fence, exhaust expands into this low pressure. As a result, some of the Momeen-en-Tum goes sideways and eej lost.

There eej a phaktor called "Thrust Coed-bijjient" which eej less than 1.0 which describes this effect.

BUT: The wind stagnates against the WEST side of the nozzle exhaust. Thij eej called Jat-In-Craaj-Phlo Ephekt.

So the brejjar there on the WEST side of nozzel eej higher than on EAST side. So phlo eej straighter there than on East side. So momentum lost to sideways flow eej less. So, thrust coebbijient is higher on west side of Nozzel than on East side. So the thrust eej higher on WEST side.

Now [b]THIS effect is like thrust-vectaring[/b]: it tilts the nose SLIGHTLY Eastwards. Like Kutb Minar with Haseena climbing the East side ladder.

Everything changes now: there is an actual EAST-wards acceleration which causes an increasing eastward velocity. Not very big, but enough to cancel out the Westward drift and more. Anyone interested can calculate precise quantities using Nagaraj bin Shapiro's Giyas Dynamics and Combrejjibal Phlow pook unless they already burned it.

*****************

In other words, Confucios' brother Imran bin Kublai say:

Never mind. Better to swig some zamzam cola and go back to watching Pak Team play Australia
(oh! but I threw the TV set after the last 5-match sweep).

Q.E.D. (Qaid-e-Duh!)
Last edited by UlanBatori on 10 Apr 2019 20:17, edited 7 times in total.

vnms
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Re: Indian ASAT Test

I'm very confused onlee.

If a plane takes off from Mumbai towards noo York, but goes slowly, the plane doesn't have to travel all the way. Noo York will come to the plane. But, this is not possible.

So, how will a ball going straight up fall 1 km away?

Very confused...

PS: Physics wasn't an area of strength. And neither was Math.

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Re: Indian ASAT Test

vnms wrote:I'm very confused onlee.

If a plane takes off from Mumbai towards noo York, but goes slowly, the plane doesn't have to travel all the way. Noo York will come to the plane. But, this is not possible.

So, how will a ball going straight up fall 1 km away?

Very confused...

PS: Physics wasn't an area of strength. And neither was Math.

why not possible without winds if the Plane defies gravity may be it will go to New york hain ji

For refernce

http://curious.astro.cornell.edu/the-universe/40-our-solar-system/the-earth/climate-and-weather/68-why-do-airplanes-take-longer-to-fly-west-than-east-intermediate

https://stratus.ssec.wisc.edu/courses/gg101/coriolis/coriolis.html

Indranil
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Re: Indian ASAT Test

vnms wrote:I'm very confused onlee.

If a plane takes off from Mumbai towards noo York, but goes slowly, the plane doesn't have to travel all the way. Noo York will come to the plane. But, this is not possible.

So, how will a ball going straight up fall 1 km away?

Very confused...

PS: Physics wasn't an area of strength. And neither was Math.

Because of the same reason that UB is specifying. The plane stays in atmosphere which has zero(if no winds) angular velocity with reapect to the surface of the earth (assuming earth is a perfect sphere).

The question being asked here is different.

UB, I haven’t fully understood how the atmosphere would affect the flight both in terms of drag and propulsive efficiency due to change in density, but I believe what you said above.

But, I don’t think Amber ji is wrong that a ball thrown in an atmosphere-less earth would land due west.

UlanBatori
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Re: Indian ASAT Test

Back to regular programming pls.
As I specified many times, all this high-funda stuff is way beyond us at UBCN. Our emphasis is still on WHY Modi came out with that highly advertised Announcement. Now that we have sort-of ruled out the RISAT Revenge as the message, what is left is that it was intended to cause tummy problems in Pindi. And add to that the mystery of the vanished IRBM Test NOTAM.

So get back to the ABM mission and the fact that
a) it takes only a sounding-rocket Mass Ratio to hit a satellite - and
b) the Shakthi has enough oomph left to hit something far far beyond - and
c) the computing power to do that with an extreme closing speed.
Not to forget:
d) the use of an ancient BISon to kill the F-16. Maybe this was the Standing Order all along, has anyone considered this? Any chance, kill an F-16 using a MiG21 or Sopwith Camel.
e) Pakis' American-made mijjiles don't work this side of LOC.

Now we have the complete explanation. The message is also to Major-City Urban desis to quit dhoti shivering about Paknukes. 2 of 3 legs of the Triad are broken: I am sure IN is out with a cricket bat to break the third leg before they even develop it.

IOW, there is much there beyond "Modi using scientists for political gain" or "DRDO forced to reveal too much detail". Note that ISRO is largely silent.
The real danger is also that Pakis may try something close to election, that their friends in the Opposition will cynically use like the crowds in Dilli in Dec. 1999 demanding capitation to Paki terrorists re: Kandahar atrocity.
Or Dilli/Mumbai BigWigs bullying GOI during Op. Parakram citing nuke fears.
Last edited by UlanBatori on 10 Apr 2019 20:45, edited 2 times in total.

ramana
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Re: Indian ASAT Test

And consider it a warning.
And you and I know who you are.*
Thanks.

* vnms
------
Say what you want or call me.

I see you are back to regular programming!

ASAT is physics with engineering taking secondary role.

Can this ASAT kill vehicles be mounted on launcher bus and used for intercepting MIRVs?
One ASAT for one MIRV makes it expensive.

Amber G.
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Re: Indian ASAT Test

Amber ji, ...It's a good question ... It is related to understanding suborbital and orbital paths and hence very much related to ASAT and a satellite.

So, how will a ball going straight up fall 1 km away? Very confused...

But, I don’t think Amber ji is wrong that a ball thrown in an atmosphere-less earth would land due west.

etc.. Let me make a few comments. If interested please read carefully, do not take my word for it or debate it for debate's sake do check out any reputable sources if interested.

To be fair, physics needed (and specially math involved) is not covered in High-school or even UG physics/math courses. Generally one learns the full math treatment in Graduate level but this is fundamental stuff for ISRO or anyone interested in understanding ASAT or orbits.
(One good book, I liked was Goldstein's classical Mechanics)

To be clear, and remember we are neglecting effects due to air
(As NRao pointed out earlier) -
- In a sense, as we study in high-school- (if ball being thrown on a cricket field) the ball thrown straight up falls back down in "your hand". A plane, flying , similarly behaves in a way, what normal high school physics courses teach us. BUT this is so because we neglect complications as their effect is negligible at low velocities.

In other words, an ordinary ball thrown straight up (even a ball regraded "fast" in cricket) will deflect so little (less than a millimeter) that it can't be measured and can be ignored.

At around 200 m/s (which is fast but still a cannon can throw this fast).. the deflection is about a few meters, still hard to measure - ( presence of wind may have more effect) but this fact is used by our armed forces in their calculations for artillery shells trajectories

In fact, India's high-speed sniper rifles correct for this as it requires accuracy.

At higher speeds things are even more counter-intuitive.

If you throw a ball faster than 11.2 Km/sec - The ball is NOT even going to return back to you.
(Q: What will happen to it ? Think about it)

Similarly for planes (which are rather slow) one can ignore this "Coriolis force" .. but for missiles and ASAT type vehicles this effect is quite large.

****

Here is some intuitive way to understand:

When I talk about straight "up" there is generally no confusion between me and my neighbor. We don't have to worry about earth's roundness or spin.
This is not so if distances are large. "Up" in India is in different direction than "up" in USA.

This is what happens when we study motion of bodies under gravity on earth.

Another factor is, higher you go, value of "g" decreases. We can assume it is constant if we are talking about altitude of a few Km, but for sats the altitude is high and one has to take this into account.

And still another factor is:
The "rotating frame of reference" is not "inertial" and if you really have to understand ASAT type trajectories you need more physics/math than ordinary "ball" trajectories.

Hope this is helpful. For more, if interested, read up, there are plenty of good resources.

Indranil
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Re: Indian ASAT Test

Amber ji,
Here’s how my high school brain worked it out.

To stop mother earth from coming in the way, let us replace it with a point of equal mass at the center of earth. Let's use a stick of negligible width to stand on to throw the ball. The other end of the stick is fixed at earths center and the stick is rotating with the same angular velocity as that of earth. Now throwing a ball from the surface of the earth is basically injecting it into an orbit around the earth point-mass. The velocity vector v defines the shape of the orbit it enters. When v is small, the point of injection is near the apogee and the perigee is almost coincidental with the center of earth. Therefore, on its way down, the ball will barely miss the top of the stick. The degree of miss will be smaller than human perception. Start throwing the ball faster and faster and the eccentricity will start growing smaller and smaller. The perigee is going to become larger and larger. Consequently, the ball is going to miss the top of the stick by more and more.

Finally, we will reach a point, where the ball enters a perfectly circular orbit and will never touch earth even if whole of earth was present. At this point, we can reintroduce mother earth as it will no longer come in the way. As v increases further, we again start to have elliptical orbits, except that the point of injection is nearer the perigee instead of the apogee. At 11.2 m/sec you can forget that the ball will ever return to you.

Not too far off, or am I?

ramana
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Re: Indian ASAT Test

11.2km/sec is escape velocity for Earth hence ball won't come back.

disha
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Re: Indian ASAT Test

Since I proved that I could sometimes horribly fail physics, let me first attempt Amber G's question in simple terms as I understand. Let's take out the velocity for moment. We can add it back in later.

1. A kid throws a ball straight up standing on Juhu beach. From the Kids' frame of reference, the ball will be vertical and will land vertically.

2. However, since the earth is rotating at a given velocity, that velocity is also being imparted to the ball (a projectile) tangentially and the ball will trace a parabola - there is vertical velocity component and there is horizontal velocity component. This is from a frame of reference outside of earth and on the same level able to watch the kid throwing the ball say by a powerful telescope.

3. As the Kid eats more spinach and develops the strength of super man, the ball goes higher and higher up. Remember at "apogee" where vertical velocity is zero there is still the tangential velocity that is making the trajectory of the ball a parabola on its way down.

4. At one point the eccentricity of the parabola (or the curve of the parabola) is larger than the curvature of the earth. That is the ball is in a constant state of falling down and the ball becomes a satellite.

As the kid gains more strength, say now kid reaches the strength of hanuman (the kid in question is actually hanuman who wanted to get back the baby-sun-ball after throwing it high up <- this part is not written in puranas yet) and throws the ball at 11.2 Kms/sec the curve instead of parabola becomes hyperbola (some hand waving - just note that the eccentricity of parabola increases and as the eccentricity of the curve becomes greater than 1 it becomes hyperbola), and the moment it becomes hyperbola the sun-ball thrown by hanuman escapes earth's gravity.

---

Yes, ASAT test is intersectopm of two trajectories. Though calculating the exact trajectory and maintaining it under all conditions is the challenge. Further challenge is to calculate it from any point of earth (remember, ASAT can be launched from submersible platforms as well). And further challenge is to come up with responsive systems that are slaved to complex algorithms that calculate the position at every point of time and follow the right trajectory to termination.

It is not just the science behind this but the engineering and infrastructure and team and managerial and ideas and solutions and bringing this all the infrastructure together in a single point of success is the multi-dimensional challenge.

That is why doing an ASAT test as a science experiment is easy. Doing it on quasi-operational basis, I think only US and India have it.

ramana
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Re: Indian ASAT Test

Guys
ASAT is not like throwing balls in the air.
Or hitting a mango with a stone like in school days*
That's what FizzleYa does. Take it physics thread.

*Nowadays you go to a store.

SriKumar
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Re: Indian ASAT Test

'Ball in air' is very simplistic relative to ASAT test. A ball thrown 'straight up' will land west of the thrower because: even though the tangential velocity of the ball remains the same as what was imparted to it on earth, it needs to traverse a longer path to 'stay overhead' of the thrower (since it is at a larger radius from center of rotation than thrower) and therefore lags (circumferentially). Coriolis effect comes into play only if traversing across latitudes (e.g. long range artillery, sniper fire, ICBMs but not ball vertically going up- since it is on same latitude).
Last edited by SriKumar on 11 Apr 2019 06:36, edited 3 times in total.

sanjaykumar
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Re: Indian ASAT Test

SriKumar wrote:'Ball in air' is very simplistic relative to ASAT test. In response to question, a ball thrown 'straight up' will land west of the thrower since the tangential velocity of the ball remains constant; however, it needs to traverse a larger distance (since it is at a larger radius from center of rotation) to 'stay overhead' of the thrower. Hence it lags (circumferentially) the thrower on the earth. Coriolis effect comes into play only if traversing across latitudes (e.g. long range artillery, sniper fire, ICBMs but not ball vertically going on- since it is on same latitude).

Thanks, I was puzzled why it would lag if it had the same tangential velocity.

Singha
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Re: Indian ASAT Test

Someone in neighbouring school has hit a sixer that is flying overhead

You are standing below with another ball and need to hit it head on

Its much more tough than hitting the sixer ball with a bullet because your ball is 3 times slower

So you must “lead” your aim by a lot and start climb into head on intercept course when sixer ball is a long way out like edge of bay of bengal

Amber G.
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Re: Indian ASAT Test

SriKumar wrote:' Coriolis effect comes into play only if traversing across latitudes (e.g. long range artillery, sniper fire, ICBMs but not ball vertically going on- since it is on same latitude).

This is NOT correct. Coriolis effect is valid for any rotating co-ordinate system - that is on our spinning earth. NOT restricted to (and DEFINITELY valid for object going vertically up) any direction or latitude (except at a pole where effect is zero). The trajectory bends "perpendicular to the velocity so a horizontal going missile or vertical going ball or any other direction for that matter.

***
Points here are:
- it is sometimes convenient to have earth (rotating surface) as our coordinate system. In this system coordinates of Mumbai or tracking systems do not change as time passes.

But now we no-longer have simplicity of inertial frame where physics is easier
.
- So people introduce two "fictitious" forces to do math and program computers on ASAT in addition to "real" force of gravity and then solve the differential equation of motion.

These are called " centrifugal force " and "coriolis" force. These are not real forces, just pretend forces just to make math simple.

Centrifugal force's, depends only on angular velocity of earth and object's altitude. Its effect is to make vale of "g" a little lower (than it will be for a stationary earth) to feed in a ASAT computer. (This difference, for example, depends on latitude and . Artillery shells (and sniper rifles) certainly takes them into account by "modifying" the value of g. (see note 1). This makes a trajectory "dip" a little less than it would have on a non-spinning earth.

Coriolis force is little complicated as it depends on the velocity of the missile as well as angular velocity of earth. It is negligible at low velocities but it will tend to "bend" trajectory a little "side ways.

(Note 1: g is no longer GM/r^2 but additional term r w^2 is added)
This makes so that one may have to modify the famous falling-body problem and the equation (height = h = v - 1/2 gt^2) as g is no longer a constant and changes with respect to h. Thus all those assumptions (parabolic orbits / constant acceleration ) need a little modifications if more accuracy is desired.

Amber G.
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Re: Indian ASAT Test

ramana wrote:11.2km/sec is escape velocity for Earth hence ball won't come back.

Yep, and it will become something a "planet" (like Mangalyaan )- orbiting around the Sun.

Additional point just to show how sophisticated math (computer programs) for ASAT would be. For such accuracy, one need not only consider effects due to earth's spin but even earth's rotation around sun and Sun's position. (My example of 11.2 was just to show when the V>escape velocity to point-out the obvious - but the effect due to sun has to be taken in doing orbit calculations to achieve high accuracy even at lower velocities.

Our scientists certainly perfected this (demonstration Mangaalyaan ) but this is still amazing - something these ddm's and other experts who like to trivialize the importance of the success of ASAT.

Amber G.
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Re: Indian ASAT Test

Indranil wrote:Amber ji,
Here’s how my high school brain worked it out.

To stop mother earth from coming in the way, let us replace it with a point of equal mass at the center of earth. Let's use a stick of negligible width to stand on to throw the ball. The other end of the stick is fixed at earths center and the stick is rotating with the same angular velocity as that of earth. ...
<snip>

Not too far off, or am I?

Very nicely explained. Thanks.

disha
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Re: Indian ASAT Test

I have to add this., the RLG developed and used by DRDO appears to be very very very sophisticated and accurate. Same goes for ISRO (Mangalyaan) but if at all things are working for our missiles, one singular attribution can be made to RLG.

Austin
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Re: Indian ASAT Test

Good Review of Global Counter Space Capability but written a month before Indian ASAT test but still covers India

https://swfound.org/media/206408/swf_gl ... 19_web.pdf

Indranil
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Re: Indian ASAT Test

Interesting.

In this thread, a summary of my OSINT analysis of a DRDO video of the Mar 27 Indian #ASAT test. I will show that the kill vehicle hit #Microsat-r in an upwards direction, not "head on" as the DRDO claims.
The Indian DRDO released a video documentary on #MissionShakti. Part of this video is imagery from an earth-based IR camera, that shows the missile hit and destroy Microsat-r.
The video gives us an accurate time of the intercept (5:42:15.5 UT), and from that a position, but interestingly enough the frames also contain missile telemetry (range, azimuth and elevation)! They cover the final 2.7 seconds of the missile trajectory.
I first thought the range and azimuth data concerned the satellite (and for the impact moment it by definition does), but after noting the range data went up instead of down, it was clear that these data actually concern telemetry from the missile (!).
And what is more: these telemetry data provide proof that the missile did *not* hit the target satellite "head-on", i.e. contradicting what DRDO chairman Sateehs is claiming.
From the azimuth, range and elevation listed in the video frame showing the impact moment, I could determine where the IR camera that filmed the sequence was approximately located (accurate to +- 1 km). This location is some 15 km SW of Chandipur ITR.
Knowing that position, the telemetry data (azimuth, elevation and range) from the other video frames can then be used to map the missile location, and in doing so reconstruct the final part of the missile trajectory!
The positions I report here are Cartesian positions with reference to a flat plane through the camera location, tangent to the earth surface. This avoids having to bother about earth curvature, as we are only interested in positions relative to the satellite vector.
Hence, it is important to realise that altitudes in the diagrams below, are *not* altitudes with respect to Mean Sea Level or the WGS84 geoid: but altitudes (in km) above this flat reference plane. These are lower than the MSL altitudes (how much, depends on the range)!
From azimuth, elevation and range information extracted from the video frames, I calculated delta X, delta Y distances relative to the IR camera sensor location, as well as the altitude Z above the flat reference plane.
From the orbital data, I did the same for Microsat-r.
Here is the result in the horizontal plane (i.e. seen from "above"). X points east, and Y points north.
Here it indeed looks like an almost frontal "head-on" hit (in fact it comes slightly from the west under a very small horizontal angle).
BUT..... (drumroll....)
...But: in the vertical plane (i.e. seen from the side), the situation is quite different! The trajectory then clearly is *not* head-on, in this plane. It is in an oblique, notably upwards direction, under an angle of ~135 degrees with the satellite movement vector.
In other words: the Indian claim of a "head-on" hit minimizing the risk of debris ejected to higher altitudes, rather than upwards hit, seems to be contradicted by the telemetry data in the video they themselve released.
(note that TLE's, the orbital elements of Microsat-r, have an intrinsic uncertainty in position of about 1 km. This is indicated by the gray area around the nominal positions for the satellite. Within the error margin, the missile and satellite trajectories meet).
Interestingly, as part of that DRDO video there is an animation which also shows a non head-on impact.
The same video also has footage of the targetting IR camera on the missile itself. In the last frames, it shows the outline of the satellite including solar panels. These appear to be seen almost full-on, which again speaks against a "head-on" hit
Because: a head-on hit would show the solar panels edge on, given the relative position of the sun at that moment and the fact that solar panels usually face the sun. An oblique hit would show them more full-on, as in the video.
So multiple lines of evidence point to it having not been a head-on hit, but an upwards moving oblique hit instead.
As we know the camera position, we can also reconstruct the projected satellite's trajectory in the impact footage FOV. Here it is projected on one of the frames (movement is upwards). Note how the debris cloud is oriented along the movement vector of the satellite:
The telemetry from the DRDO video, shows that in the Cartesian XY plane, the kill vehicle hit it under a very slight angle with the satellite movement vector (crossing the satellite path coming from slightly east and then homing in slightly from the west).
That same thing is borne out by the distribution of the orbital inclinations of the debris fragments that are being tracked by CSpOC. These fragments have somewhat lower orbital inclinations than the satellite's original orbit, meaning an impact coming slightly from west.
Finally, using tracking data from CSpOC on these debris fragments, I calculated the delta V (the extra ejection speed relative to the original Microsat-r speed) necessary to get them into these orbits, taking into account changed orbital altitudes & the inclination change.
The resulting delta V's have this distribution, with most of it in the 10 to 300 meter/second range.
That's it, as far as the current state of my OSINT analysis is concerned. As said, I will write this up more comprehensively as a more formal publication, but that might take a few days.

It is not unbelievable. Actually, this makes the test results more outstanding. It is a more difficult intercept. But it does increase the risk of some debris to have orbits with higher apogee.

prasannasimha
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Re: Indian ASAT Test

Moderatr niote
I have deleted one unnecessary response, Any more will invite bans and deletes

prasannasimha
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Re: Indian ASAT Test

^^ Basic problem is he is assuming that the solar panel plane was unchanged . Actually it looks like the microsat was made to do a pitch maneuver and the solar panels were head on. Possibilities are to test for multipoint discrimination or something else as it had to hit main body and not just the solar panels

sanjaykumar
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Re: Indian ASAT Test

He is using telemetry data to locate the camera and then uses camera location to interpret telemetry data. This is a good example of how not to do science.

Karan M
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Re: Indian ASAT Test

Can someone with the patience write a rebuttal and puncture his claims? These hacks are all out to disparage Indian efforts in every field using specious interpretations.

Indranil
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Re: Indian ASAT Test

Karan,

Why care? If there is an ASAT test, there would be debris. Actually, head on collision creates the lowest chances of debris to reach higher apogee orbits. But, hitting the satellite on the way down would create the most atmosphere intersecting debris (if I am not wrong). Most debris from the KKV will enter the atmosphere in minutes, depending on the angle of interception.

When I wrote the article, I had made this assumption. Now a K4 class booster with the 1.8 ton KKV cannot reach apogee in 3 minutes. So, I knew I was wrong. But if they went for a depressed trajectory, they could have been very close to a head-on collision. That was what I was hoping for.

But, DRDOs imagery is either not a true depiction of what happened, or we hit the satellite on the way up. So, for example, it is completely true that if the satellite is moving almost due north, the KKV is moving almost due south, the time is around midday and the solar panels on the satellite are facing the sun, then in a head on collision you will see the solar panels almost edge-on. Kind of like you walking up to a person (of similar height) holding up an umbrella at midday. A bird swooping down on the person will see the top (full profile) of the umbrella.

But this takes nothing away from the capability standpoint. As I said earlier, AFAIK a side-on intercept is much more difficult than head on (you have significantly higher relative angular velocity). And definitely, the KKV can hit satellites flying much higher.

The simulations and true data show that the debris are decaying as desired. There will be a couple of debris out there for about a year. But most will decay within 2 months. Just like DRDO simulations showed.

The scientific space community will always look down on ASAT tests. And, IMHO it should. There is nobility there. So don't fight them. It is a necessary evil that we have to have. Just like a nuclear bomb.

nachiket
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Re: Indian ASAT Test

Indranil wrote:Karan,

Why care? If there is an ASAT test, there would be debris.

The scientific space community will always look down on ASAT tests. And, IMHO it should. There is nobility there. So don't fight them. It is a necessary evil that we have to have. Just like a nuclear bomb.

The proper response is not to try and claim the high ground by proving we created less debris than anyone else, but to tell the space community that most of you are sitting in the country which started this. Your country started the nuclearizing of the world a well and actually killed hundreds of thousands using those weapons. Just like they started the militarization of space. Now that they have already done it, we will make debris if we want to as well and if you have a problem you can go screw yourselves.

sudeepj
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Re: Indian ASAT Test

Karan M
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Re: Indian ASAT Test

Indranil wrote:Karan,

Why care?

************
If there is an ASAT test, there would be debris. The scientific space community will always look down on ASAT tests. And, IMHO it should. There is nobility there. So don't fight them. It is a necessary evil that we have to have. Just like a nuclear bomb.

Indranil, IMHO there is no nobility in these guys keeping silent on western tests and at the same time trying to run down our stated efforts by saying that we lied, hid data etc. This is then used to make up a case we are == China or any other totalitarian state. They have preconceived notions vis a vis India, Indians and take that idealogical bias into their so called analysis. I seriously urge you to counter his points via a published article.

We need more and more of our views out there, of Indians willing to show these guys that just because they write something, it does not become the gospel truth. Problem is most Indians will instinctively now the above guys have a tendency to put us down, but will respond with angry comments, which is then used to further portray an image of Indians being immature, angry, this was PR for national pride etc.