Anti-satellite weapon test?, Is this true? Options

[Thu]

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?

[climber]

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?

OK, weather forcasts are sometimes very bad. I didn't thought China will get THAT angry about it

[Lorne Ipsum]

Nobody really knows the details, but most reports I've read say the satellite was hit with a kinetic warhead (i.e., no explosives, just a direct hit with the sensor head). This pretty much mandates a "smart" projectile.

Lorne

[nprev]

Anybody know what the inclination of the target satellite's orbit was? I got a sinking feeling that it might well have been in a polar orbit...worried a bit about the NOAA polar orbiters & that debris cloud...

EDIT: Yep, it was in a polar orbit, but a bit below the NOAA POES...

[OWW]

I got a sinking feeling that it might well have been in a polar orbit...worried a bit about the NOAA polar orbiters & that debris cloud...

EDIT: Yep, it was in a polar orbit, but a bit below the NOAA POES...

According to Jonathan's Space Report ( http://www.planet4589.org/space/jsr/latest.html ):

The FY-1C was in an 843 x 862 km x 98.7 deg orbit; the debris cataloged so far ranges from
165 x 850 km to 850 x 3500 km, a wide range of heights indicating an
energetic fragmentation with delta-Vs of -190 to +550 m/s. Of course,
we are missing the tail of dV significantly less than -190 since those objects
would reenter immediately.

Correct me if I'm wrong, but doesn't this put ALL satellites from 165 to 3500 km at risk and not just the ones around 850 km?

[Thu]

Thank you all for your information. Still no official speak from China yet so I do believe the test was real
There is no international law against this kind of test? How about the Outer Space Treaty?

[djellison]

Very very close to becoming a political thread here - but the USA recently refused to sign up to an agreement banning such tests.

Doug

[Chmee]

The US did develop an anti-satellite weapon back in the 1980's and actually shot one down in 1985. I beleive the weapon was actually carried on an F-15 and shot into space (Pagasus style). While the US has not conducted such tests since then (that we know of..) it is beleived they still have the capability.

As for the Chinese anti-sat weapon being 'smart' or 'dumb' it is hard to say. You would not have to do a 'bullet hits a bullet' type of kill vehicle to accomplish this. Rather, a 'dumb' weapon could be used to spray some material, over a large area, in the path of the intended satellite, like sand or ball bearings. The relative speed would between the objects would be all thats needed.

[djellison]

like sand or ball bearings. The relative speed would between the objects would be all thats needed.

That's what I was imagining this to have been. Launch - on a high sub-orb trajectory, and disperse a cloud of lead shot etc - through the satellite goes - 7.5k/sec impacts - the remaining shot just re-enters harmlessly but the sat is blown to pieces.

Doug

[tty]

Actually a satellite in LEO is not a particularly challenging target. Its position and trajectory is known in advance and it is usually a non-maneuvring target. Also it usually has a nice big cross-section in both the radar, IR and visual band and operates in a very uncluttered environment.

All that is needed is a reasonably precise suborbital rocket and a suitable warhead. However I doubt that the "ball-bearing/sand" solution is cost effective. Unless You release quite close to the target they would probably disperse too thinly to ensure a kill. It would probably be better to use a homing warhead with a proximity fuse. Anybody having the technology for the carrier rocket should be able to handle the guidance system and the warhead too.

tty

[Bob Shaw]

It would probably be better to use a homing warhead with a proximity fuse. Anybody having the technology for the carrier rocket should be able to handle the guidance system and the warhead too.

tty

It's a tad more difficult than it looks. Most aircraft missile systems don't use thrust to control attitude, but instead rely on aerodynamic forces. An exoatmospheric vehicle has to be precisely stabilised, and because it has to actively hunt down a target then spinning probably won't do. You're looking at 3-axis attitude control, plus an ability to change direction at very short notice. Some of the Star Wars kinetic kill vehicles not only were 3-axis stabilised, but also spun to deploy arms at the last moment and then also disintegrated to provide further frontal area. All this has to be arranged in a space of seconds, with space-hardened computers. All in all, it's a very tough call, and the US has done it only a very few times (and sometimes by moving the goalposts after the event). China's success is a major milestone, and speaks highly of their space technology.


Bob Shaw

[helvick]

So with a bit of luck they might now consider that they have successfully shown all interested parties that they are well in contention in LEO and that they now need to demonstrate some serious long range remote capability - expect Chinese Moon, Mars and outer planets missions to follow shortly.

So it's time to go and learn Chinese folks so we can stay on top of CNSA's PR department.

(Just looking for the bright side since this is my 1000'th post. )

[djellison]

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

[helvick]

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.

[tty]

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.

Well, not early Sidewinder at least since they used pursuit-curve logic. This would be a collision-course interception, preferably from nearly dead ahead and would probably use constant-bearing logic. That is: if You keep the bearing to the target constant you are bound to hit it sooner or later.
The main problem in this case is the very high closure rate which means that tracking and manoeuvring have to be precise at fairly long range otherwise very large and fast corrections will be needed at a late stage in the interception. The proximity fuse will also need to be fast and precise. The latter is more difficult than it sounds. Sufficiently precise fusing is one of the main challenges in building implosion-type nuclear weapons.

tty