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Anti-satellite weapon test?, Is this true?
Thu
post Jan 19 2007, 02:39 PM
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According to this link, China fired a missile to destroy an orbiting weather satellite last week: http://www.spacewar.com/reports/China_Tras...e_Test_999.html

I am curios about what kind of projectile could be used? A "smart" one with on board guidance system or just a dumb one? How close did the "killer satellite" came to the target?

Does anybody have an idea?
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djellison
post Jan 22 2007, 09:01 PM
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Just thinking in terms of 'impact window' - i.e. the time taken for the target to cover it's own size in terms of distance - the variable that identifies how accurate something has to be to hit something rushing past - not totally analogous ( you could drive 'down' the velocity vector for instance ) - but it gives you a sense of the scale of the problem.

Car - 4.3 metres - 26 m/sec - window is 0.165 seconds.
Jumbo Jet - 57 metres - 223 m/sec - window is 0.255 seconds ( this is why a jumbo 'looks' so slow in the sky - it covers it's own length slower than a small car rushing past). F22 - .030 seconds.

Satellite - 3 metre sized bus - 7500 m/sec - window is 0.0004 seconds

i.e. stood watching the thing fly past - you've got to be 412 times more accurate hitting a spacecraft than a car doing 60 mph. 637 times more accurate than hitting a flying jumbo - and 75 times more accurate than hitting an F22 raptor.

It's a big ask - I don't know how hard it actually is - but this isn't "let's modify a sidewinder' type thing.

Doug
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helvick
post Jan 22 2007, 09:24 PM
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Your calculations are only valid for an orthogonal impact, that's probably not the ideal way to do this.

Taking x-axis to be cross track relative to the target, y-axis to be on track and z-axis to be vertical. If you are going to rely on kinetics alone to do the work for you the ideal approach would be to lob your "warhead" into a z-axis ballistic curve that tracks along the targe's y-axis (so x-axis velocity relative to the target is negligable) timed to reach zenith just ahead of the target's arrival (so the z-axis velocity relative to the target is very small). The high y-axis relatively velocity then becomes an advantage as the probe will impact the "warhead" if it intersects the probe at any stage during it's "hang time". For a 25cm "warhead" that impact window is almost a quarter of a second assuming you can target the orbital track and altitude with the same precision. That is obviously not a trivial task but I think it should be simpler than active targetting with a 0.4 microsecond window.
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Posts in this topic
- Thu   Anti-satellite weapon test?   Jan 19 2007, 02:39 PM
- - climber   QUOTE (Thu @ Jan 19 2007, 03:39 PM) Accor...   Jan 19 2007, 03:06 PM
- - Lorne Ipsum   Nobody really knows the details, but most reports ...   Jan 19 2007, 06:51 PM
- - nprev   Anybody know what the inclination of the target sa...   Jan 20 2007, 01:59 AM
|- - OWW   QUOTE (nprev @ Jan 20 2007, 02:59 AM) I g...   Jan 20 2007, 12:12 PM
- - Thu   Thank you all for your information. Still no offic...   Jan 22 2007, 04:42 PM
- - djellison   Very very close to becoming a political thread her...   Jan 22 2007, 04:53 PM
|- - Chmee   The US did develop an anti-satellite weapon back i...   Jan 22 2007, 05:55 PM
|- - djellison   QUOTE (Chmee @ Jan 22 2007, 05:55 PM) lik...   Jan 22 2007, 06:29 PM
- - tty   Actually a satellite in LEO is not a particularly ...   Jan 22 2007, 07:34 PM
|- - Bob Shaw   QUOTE (tty @ Jan 22 2007, 07:34 PM) It wo...   Jan 22 2007, 08:18 PM
|- - helvick   So with a bit of luck they might now consider that...   Jan 22 2007, 08:46 PM
|- - climber   QUOTE (helvick @ Jan 22 2007, 09:46 PM) (...   Jan 23 2007, 08:55 AM
||- - Bob Shaw   QUOTE (climber @ Jan 23 2007, 08:55 AM) M...   Jan 23 2007, 11:42 AM
|- - Bob Shaw   QUOTE (helvick @ Jan 22 2007, 08:46 PM) (...   Jan 23 2007, 11:31 AM
- - djellison   Just thinking in terms of 'impact window' ...   Jan 22 2007, 09:01 PM
|- - helvick   Your calculations are only valid for an orthogonal...   Jan 22 2007, 09:24 PM
|- - tty   QUOTE (djellison @ Jan 22 2007, 10:01 PM)...   Jan 23 2007, 07:32 AM
- - djellison   You don't need fusing - this was a kinetic imp...   Jan 23 2007, 08:47 AM
|- - Bob Shaw   QUOTE (djellison @ Jan 23 2007, 08:47 AM)...   Jan 23 2007, 11:11 AM
- - mchan   There was an article quoting unamed sources that t...   Jan 24 2007, 04:39 AM
|- - Bob Shaw   QUOTE (mchan @ Jan 24 2007, 04:39 AM) The...   Jan 24 2007, 12:11 PM
|- - tty   QUOTE (Bob Shaw @ Jan 24 2007, 01:11 PM) ...   Jan 24 2007, 07:46 PM
|- - Bob Shaw   QUOTE (tty @ Jan 24 2007, 07:46 PM) The n...   Jan 24 2007, 09:14 PM
|- - tty   QUOTE (Bob Shaw @ Jan 24 2007, 10:14 PM) ...   Jan 25 2007, 07:07 AM
- - climber   Interesting article on this topic on Aviation Week...   Jan 24 2007, 03:56 PM
- - Thu   Finally, we have an official announcement from Chi...   Jan 25 2007, 01:07 AM
- - CosmicRocker   I rarely stray into this section of the Forum, and...   Jan 25 2007, 06:13 AM
- - nprev   Just to put a bit of (hopefully) UMSF-related spin...   Jan 26 2007, 02:35 AM


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