by Chris Peterson » Fri Sep 16, 2011 2:24 pm
bacon55 wrote:Because rocket debris will fall in trajectories that cross through launch sites. Not satellites, but things like casings, primary engine stages, etc.
That is not so. Debris falls downrange, which in the case of Vandenburg launches is over the Pacific Ocean. No more reentering debris is observed around launch sites than anywhere else. Keep in mind that if this was debris, it came from orbit, or else it would not have been moving fast enough to ablate.
No matter what direction you launch a rocket, unless there's a very unusual change in trajectory at an extreme altitude, you'll have a path that specific debris is traveling around the Earth cross through facilities like Cape Canaveral, Vandenberg, and Baikonur. The latitudes of the launch sites has a direct connection with debris concentrations as well.
The fact that the orbits have inclinations that cover the latitude of the launch site does not result in more space junk being observed near launch sites. The orbital ground paths are far too long for that.
The colour comes from the atmosphere? Absolutely not. Well, er, it comes from the materials burning in the oxygen of the atmosphere (otherwise all meteorites and space debris would burn the same colour, the atmosphere has a near universal composition.) Different materials burn in different colours. Sure you can get some prismatic effects, but if you toss a big chunk of magnesium into the atmosphere from orbit it's going to burn a bright white. Copper will burn a bright green, etc. The ionized gas you're seeing is the material of the asteroid being burned and vapourized. The ionization trail is what's left of that meteorite.
You are mistaken. Certainly, you can spectroscopically observe all sorts of elemental and chemical species in burning meteoroids. But the bulk color observed is not closely related to the material composition. The head color is primarily just the product of black body radiation, and of an integrated mix of many thermally broadened emission lines. Normally it is white, but may shift towards the red for low speed, cool meteoroids. This is also why red or orange is often reported by observers just before the meteoroid burns out. Other than the white or cooler colors seen in the head, the other color that is commonly reported in meteors is green or blue-green, which is caused by ionization of atmospheric oxygen. Ionized nitrogen also adds to the mix. Colors from meteoroid constituents- silicon, sodium, iron, nickel- are usually subtle and not well observed. There is little or no correlation between the observed colors of a meteor event and the actual composition when it can be determined by a meteorite recovery. The same holds true for space debris.
From wiki:
The visible light produced by a meteor may take on various hues, depending on the chemical composition of the meteoroid, and its speed through the atmosphere. As layers of the meteoroid are stripped off and ionized, the color of the light emitted may change according to the layering of minerals. Some of the possible colors and the compounds responsible for them are: orange/yellow (sodium); yellow (iron); blue/green (copper); purple (potassium); and red (silicate).
The Wiki article is not very good. Meteoroids don't have layered materials. What I believe this article is (badly) referencing is a phenomenon called differential ablation, which occurs with small meteoroids (the sort that produce ordinary meteors, not fireballs), where different species are produced at different times as the temperature changes- refractory materials being the last to burn. This is seen spectroscopically, and in radar studies. It isn't normally a visual phenomenon.
I've seen the first results now of camera-based speed estimates, and this fireball appears to have been moving too fast to be reentering space junk. Also, the only candidate decay object has been confirmed to have decayed south of the equator. So this fireball was almost certainly a natural meteoroid, of either stony or iron composition.
[quote="bacon55"]Because rocket debris will fall in trajectories that cross through launch sites. Not satellites, but things like casings, primary engine stages, etc.[/quote]
That is not so. Debris falls downrange, which in the case of Vandenburg launches is over the Pacific Ocean. No more reentering debris is observed around launch sites than anywhere else. Keep in mind that if this was debris, it came from orbit, or else it would not have been moving fast enough to ablate.
[quote]No matter what direction you launch a rocket, unless there's a very unusual change in trajectory at an extreme altitude, you'll have a path that specific debris is traveling around the Earth cross through facilities like Cape Canaveral, Vandenberg, and Baikonur. The latitudes of the launch sites has a direct connection with debris concentrations as well.[/quote]
The fact that the orbits have inclinations that cover the latitude of the launch site does not result in more space junk being observed near launch sites. The orbital ground paths are far too long for that.
[quote]The colour comes from the atmosphere? Absolutely not. Well, er, it comes from the materials burning in the oxygen of the atmosphere (otherwise all meteorites and space debris would burn the same colour, the atmosphere has a near universal composition.) Different materials burn in different colours. Sure you can get some prismatic effects, but if you toss a big chunk of magnesium into the atmosphere from orbit it's going to burn a bright white. Copper will burn a bright green, etc. The ionized gas you're seeing is the material of the asteroid being burned and vapourized. The ionization trail is what's left of that meteorite.[/quote]
You are mistaken. Certainly, you can spectroscopically observe all sorts of elemental and chemical species in burning meteoroids. But the bulk color observed is not closely related to the material composition. The head color is primarily just the product of black body radiation, and of an integrated mix of many thermally broadened emission lines. Normally it is white, but may shift towards the red for low speed, cool meteoroids. This is also why red or orange is often reported by observers just before the meteoroid burns out. Other than the white or cooler colors seen in the head, the other color that is commonly reported in meteors is green or blue-green, which is caused by ionization of atmospheric oxygen. Ionized nitrogen also adds to the mix. Colors from meteoroid constituents- silicon, sodium, iron, nickel- are usually subtle and not well observed. There is little or no correlation between the observed colors of a meteor event and the actual composition when it can be determined by a meteorite recovery. The same holds true for space debris.
[quote]From wiki:
[quote]The visible light produced by a meteor may take on various hues, depending on the chemical composition of the meteoroid, and its speed through the atmosphere. As layers of the meteoroid are stripped off and ionized, the color of the light emitted may change according to the layering of minerals. Some of the possible colors and the compounds responsible for them are: orange/yellow (sodium); yellow (iron); blue/green (copper); purple (potassium); and red (silicate).[/quote][/quote]
The Wiki article is not very good. Meteoroids don't have layered materials. What I believe this article is (badly) referencing is a phenomenon called differential ablation, which occurs with small meteoroids (the sort that produce ordinary meteors, not fireballs), where different species are produced at different times as the temperature changes- refractory materials being the last to burn. This is seen spectroscopically, and in radar studies. It isn't normally a visual phenomenon.
I've seen the first results now of camera-based speed estimates, and this fireball appears to have been moving too fast to be reentering space junk. Also, the only candidate decay object has been confirmed to have decayed south of the equator. So this fireball was almost certainly a natural meteoroid, of either stony or iron composition.