What a great shot ! (?)

[Michaelangelica]

What a great shot ! (?)

Saturday, Jan. 20, 2007



Starwars is finally here!

Japan sees security threat
Staff report

Top Cabinet officials expressed concern Friday over China's reported firing of an antisatellite weapon to destroy an aging Chinese satellite.

"We're concerned from the viewpoint of security and the peaceful use of outer space," Chief Cabinet Secretary Yasuhisa Shiozaki said Friday.

Foreign Minister Taro Aso told a separate news conference that China's firing of a ground-based medium-range ballistic missile in what was considered an antisatellite weapon test on Jan. 11 posed various security problems.

Japan sees security threat | The Japan Times Online

[Jay-qu]

bo-ya now every satellite that goes up will have to be fitted with an anti-antisatellite laser

[CraigD]

ASAT weapons have been tested since the late 1950s. A system that caught the public fancy (or at least the aviation enthusiast public fancy) was the US’s F-15 “satellite killer” configuration, in which the superb F-15 fighter jet functioned as a completely reusable ASM-135 ASAT 3-stage rocket, which successfully killed an orbiting US research satellite on 9/13/1985. Although public information about the continued availability of this ASAT system is limited, it's widely believed that the US military has “enough around” to destroy a sizable constellation of satellites, should it be so ordered.

Like the 1985 F-15/ASM-135 test, but unlike the 1958 nuclear explosive missile test, China’s KT-1-based system, is a “kinetic kill” system, essentially a non-explosive bullet. To the best of my knowledge, former USSR test of ASAT systems where limited to maneuvering “hunter-killer” satellites without actually striking and destroying any target satellites, and produces only minimal debris.

The US government’s (eg: State Department deputy spokesman Tom Casey) condemnation of the Chinese test seems to this US citizen hypocritical, especially those claiming that this single test has somehow “littered low Earth orbit” with more debris than its own two (1958 and 1985) tests, a clear case of “do as we say, not as we do”.

This is not to say that space debris is not a significant problem. I hope that, like the US, China realizes this, limits itself to the single test to prove, to themselves and the world, that its system works, is faithful to its pledge to use this capability only to defend against attack by space based weapons, and that other spacefaring nations see this as additional reason to not put offensive weapons in space.

[infamous]

It has been brought to my attention that this topic has very little to do with Astronomy and or Cosmology. Agreeing with this I think it only proper to move this thread to Social Sciences forum where the politics about this issue can more appropriately be discussed.........................Infy

[CraigD]

Originally Posted by infamous

It has been brought to my attention that this topic has very little to do with Astronomy and or Cosmology. Agreeing with this I think it only proper to move this thread to Social Sciences forum where the politics about this issue can more appropriately be discussed.........................Infy

I'd recommend the Space forum, as the subject involves spacecraft. Of course, all technology has a social component, but this subject seems to me more connected to the technology than the sociology.

[infamous]

Originally Posted by CraigD

I'd recommend the Space forum, as the subject involves spacecraft. Of course, all technology has a social component, but this subject seems to me more connected to the technology than the sociology.

Agreed Graig, but if this turns into a political debate I'll be very tempted to move it back to Social Sciences....................Infy

[theblackalchemist]

It gives me pleasure
finally some one to get rid of space junk
TBA

[Boerseun]

Originally Posted by theblackalchemist

It gives me pleasure
finally some one to get rid of space junk
TBA

What - by producing more? I very much doubt the effectiveness of "ballistic killers" of the non-explosive type. When seen face-on, the biggest part of a satellite is its solar panels. A ballistic non-explosive rocket will just punch a hole through something, like a very expensive bullet. And chances are it'll go through a solar panel (dummys can be fitted, of course, for this exact same reason) and only bring down the satellite's power supply by a few percent. To reduce the odds of this, they'll have to make the ASAT rockets explosive.

The problem with this, of course, is that in the resulting explosion, a sphere of debris will fly away from the explosion point. Most of it at the right angle and velocity to either go down to Earth and burn up in the atmosphere, or away into space, with sufficient velocity to escape Earth. But quite a lot of it will have the perfect velocity and orbit away from the explosion point to have a stable Earth orbit. Where there was only one satellite in orbit, there is now thousands of little pieces of metal, glass, flecks of paint, random crap from a single explosion, and it'll be there for years to come, making space a very dangerous place, becoming more lethal to both astronauts and satellites with each new explosion.

It'll be ironic if our access to space is completely and utterly removed for a few hundred years due to a short war in the early 2000's.

[CraigD]

Originally Posted by theblackalchemist

It gives me pleasure
finally some one to get rid of space junk
TBA

As Boerseun, and critics of the 1/11/2007 Chinese anti-satellite missile test point out, current ASAT weapons don’t get rid of space junk, but create it, transforming an intact satellite into an expanding debris swarm, each individual piece with a slightly different orbit. Though some of these individual orbits intersect the atmosphere, causing the debris to burn up (or, if big and durable enough, strike the ground), most remains in orbit for many years.

Most space junk is in low-Earth orbit, moving at about 8000 m/s. By comparison, the fastest muzzle velocity achieved by a conventional firearm is about 1800 m/s, making a severe space debris collision (the worst realistic case is an equatorial orbit intersecting a polar orbit) nearly 30 times more energetic than a point-blank collision with the same size projectile shot from the most powerful conventional gun. Not something you, or your spacecraft, wants to experience

Originally Posted by Boerseun

I very much doubt the effectiveness of "ballistic killers" of the non-explosive type. When seen face-on, the biggest part of a satellite is its solar panels. A ballistic non-explosive rocket will just punch a hole through something, like a very expensive bullet.

When I first read about “kinetic kill vehicle”, I was likewise skeptical, but some research and consideration of basic mechanics led me to conclude that the many weapon designers and military planners who’ve concluded that they’re equivalent to or better than explosive kill vehicles are correct. The 1985 and 2007 tests appear to support this

I think my initial impression was the result of some assumptions based on my hands-on experience with shooting stuff near the surface of good ‘ole planet Earth:

• Projectile speed I’m used to bullets with typical impact speeds of 300 (pistols) to 900 (rifles) m/s. (Growing up in rural WV, USA, I like most boys spent considerable time shooting up abandoned cars, appliances, and anything else that could be found in the woods ) An ASAT has a typical impact speed of greater than 10000 m/s (According to this page, 24000 m/s for the ASM-135), 100 to 5000 time the kinetic energy () of the same projectile at typical bullet speeds.
• Projectile integrity I’m used to bullets keeping their shape, or at worse splitting into a few twisted pieces. A bullet punching though a piece of paper transfers little of it’s kinetic energy to the paper (as was vividly illustrated for me one evening in the form of a .357 Magnum bullet that required a bale of Excelsior, the wall of a building, the sheetmetal of a nearby building’s porch skirt, and a centimeter or two of dirt to transfer all of its kinetic energy ) Very high speed bullets don’t do this, but fragment practically into dust, transferring all of their energy into even a fairly thin thickness of target material.
• Atmosphere I’m accustom to the ejecta – bits of paper, glass, sheet metal or what-have-you - from a bullet hole rapidly slowing due to air friction, and falling harmlessly to the ground. In vacuum, these ejecta, and the fine fragments of the bullet, encounter no air resistance, so continue until they hit something to transfer their energy to, and so on.
• Size ASAT bullets are big. The ASM-135’s is rumored to be about 200 kg – bigger than a tank gun’s (about 10 kg), but smaller than a battleship’s (about 1000 kg). Bullets this massive are incredibly beyond anything in my personal experience!

With physics like these, chemical explosives don’t add much to the destruction, other than a way, using a fairly small explosive charge, to spread the projectile over a larger area just before impact, increasing its chance of a hit. This “space shotgun” technique was popular in the late 1980s and early 1990s as a way to overcome guidance system inaccuracies, and was featured in several proposed US ASATs, and the Soviet “Istrebitel Sputnikov” (“Satellite killer”). These systems strike me as space debris nightmares!

PS: All of this gloom, doom, and talk of explosions is inspiring me to find and watch "Planetes", a 2003 animated sci-fi TV series about heroic astronauts clearing Earth/Moon space of space debris. Everything I’ve read about it praises it.

[TheBigDog]

It seems to me that a satellite could be built specifically for clearing space debris. Put it in a higher orbit, give it a powerful targeting radar and a fairly energetic laser. It would be shooting down at targets and the laser energy would push the targets down into the atmosphere where they would burn up.

Of course the owner of such a device would need to be trusted not to use it to destroy satellites of other parties, and that would be a political trick. But such a device could clear thousands of pieces of junk per year.

Bill