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#21
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Why Christer and not Suni for EVA-4?
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#22
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Why Christer and not Suni for EVA-4?
"Danny Deger" wrote Does anyone know if the ground radars have a track on the camera? Yes, I do. grin From today's on-orbit status report: Lost EVA Camera Update: The Kodak DCS 760 still camera lost overboard during EVA-3 is tracking below and in front of the station. After tomorrow's (FD11) Shuttle undocking, it will be approximately 100 nmi in front of Discovery, opening with 50 nmi per revolution. |
#23
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Why Christer and not Suni for EVA-4?
The camera may or may not be a collision issue for the Space
Station depending on which way the camera fell relative to the space station. If the camera has less drag, it fell up and may be a collision issue in the future when the Space Station does a reboost. If the camera fell down, more drag, then it's not an issue as I doubt the Space Station is going to deliberately lower it's orbit below the camera. If the camera fell up, then when the Station does a reboost it will have to cross the altitude of the camera. Any future collision problem really has to to with the angle between the velocity vectors. The difference in the velocity vectors will most likely be very small, but the angle between them will most likely be significant. The relative velocity will be huge. Up or down, the camera gets a new number in the database. Worst yet, nobody get to see the pictures. -- Craig Fink Courtesy E-Mail Welcome @ -- On Tue, 19 Dec 2006 02:43:20+0000, George Evans wrote: OTOH, I don't see the camera being a collision issue. It can't build up enough relative velocity. |
#24
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camera tracking
didn't anybody read the report, below?
"Jim Oberg" wrote "Danny Deger" wrote Does anyone know if the ground radars have a track on the camera? Yes, I do. grin From today's on-orbit status report: Lost EVA Camera Update: The Kodak DCS 760 still camera lost overboard during EVA-3 is tracking below and in front of the station. After tomorrow's (FD11) Shuttle undocking, it will be approximately 100 nmi in front of Discovery, opening with 50 nmi per revolution. |
#25
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Why Christer and not Suni for EVA-4?
Starting, undocking, rendezvous would be another level of redundancy. But
how many levels of redundancy are required. Failure one, the tether breaking. The SAFER looks like it has two nozzles for each direction, dual systems? That's two more failures to strand one astronaut. Spacewalking is usally done with the buddy system, that add another three failures to strand two astronauts. Six failures deep before "starting" a Soyuz or Shuttle to go get stranded astronauts. Four without the tethers. And that's not the only way to get a part or astronaut that is slowly drifting away. Boating, nets are handy. Throw lines are specifically designed for that purpose of getting someone back on board. I would think NASA might actually have more of a problem with astronauts accidently on purpose dropping something so they can take a little tethered SAFER cruise. Like someone standing during entry when NASA had no reasonable way of punishing the guy, it was his last mission. Using up a little SAFER propellent at the end of the last spacewalk might even be considered a nice reward for a sucessful mission. Plus, it would make SAFER-2 even safer than SAFER. Use would show faults which leads to better design. -- Craig Fink Courtesy E-Mail Welcome @ -- On Tue, 19 Dec 2006 01:57:57+0000, Danny Deger wrote: How long would it take to "start" the Soyuz or the shuttle? My guess is too long |
#27
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Why Christer and not Suni for EVA-4?
I agree with you about the short term, and the low velocity impacts on the
order of it's initial departing velocity. I was talking about longer term. If the two are at different altitudes for any length of time, precession become the main problem that gives the relative velocity of the two a huge magnitude. Drag is the determining factor, not initial velocity. If the object fell down (more drag) it's gone forever as far as the Space Station is concerned. If it fell up (less drag), then the Space Station has to cross it's altitude again at some point in the future, depending on the reboost magnitudes and time intervals, it may cross multiple times after spending a large amount of time at different altitudes. One on an ascending pass, the other descending would give a maximum of 114 degrees closing angle for an impact at equator. Faster than the orbital speed of either, and the amount of damage would be tremendous. Luckily it can be tracked. Something smaller, like a nut or a bolt, it's just random luck when they pass though each other's altitude. Remember last flight, after the Shuttle left the Station and before the deorbit burn. I wonder if the debris they saw was just a normal part of the debris field leaving the Space Station, they just happened to be parked in it for a while. -- Craig Fink Courtesy E-Mail Welcome @ -- On Wed, 20 Dec 2006 05:35:17 +0000, George Evans wrote: in article , Craig Fink at wrote on 12/19/06 3:31 AM: The camera may or may not be a collision issue for the Space Station depending on which way the camera fell relative to the space station. If the camera has less drag, it fell up and may be a collision issue in the future when the Space Station does a reboost. If the camera fell down, more drag, then it's not an issue as I doubt the Space Station is going to deliberately lower it's orbit below the camera. The initial velocity relative to the station is more important than drag. If the camera's initial velocity was generally forward and that it's relative speed was a tenth of a foot per second, then, during the first orbit, will loop up and back about 300 feet above the station, and end about a quarter mile roughly behind the station. Each orbit would take it another quarter mile behind. By the end of just the first day the camera would be six miles back. From the perspective of the station, if the camera has less drag, this pattern will be exaggerated, placing the camera even farther back and somewhat higher each day. In this case, when reboost occurs, it will take the station forward and up above the orbit of the camera. If the camera has more drag that component will eventually cause the camera to cross the station orbit far behind and then safely under the orbit. The only way the camera could even conceivably end up in the vicinity of the station is initially going generally backward with less drag. In this case the camera would loop forward six miles a day but then cross and begin drift back and up. Reboost could conceivably cause the station to converge with the camera. Another interesting possibility is an initial direction perpendicular to the station orbit. In this case the camera will make a close pass ever 45 minutes until differential drag removes it from the area. Of course each pass will be at a tenth of a foot per second. If the camera fell up, then when the Station does a reboost it will have to cross the altitude of the camera. Any future collision problem really has to to with the angle between the velocity vectors. The difference in the velocity vectors will most likely be very small, but the angle between them will most likely be significant. The relative velocity will be huge. There is no way the relative velocity will ever be huge. At the very worst I'm guessing there may be enough to take out an antenna, but nothing life threatening. Up or down, the camera gets a new number in the database. Worst yet, nobody get to see the pictures. This is the worst part of losing the camera. George Evans |
#28
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Why Christer and not Suni for EVA-4?
I agree with you about the short term, and the low velocity impacts on the
order of it's initial departing velocity. I was talking about longer term. If the two are at different altitudes for any length of time, precession become the main problem that gives the relative velocity of the two a huge magnitude. Drag is the determining factor, not initial velocity. If the object fell down (more drag) it's gone forever as far as the Space Station is concerned. If it fell up (less drag), then the Space Station has to cross it's altitude again at some point in the future, depending on the reboost magnitudes and time intervals, it may cross multiple times after spending a large amount of time at different altitudes. One on an ascending pass, the other descending would give a maximum of 114 degrees closing angle for an impact at equator. Faster than the orbital speed of either, and the amount of damage would be tremendous. Luckily it can be tracked. Something smaller, like a nut or a bolt, it's just random luck when they pass though each other's altitude. Remember last flight, after the Shuttle left the Station and before the deorbit burn. I wonder if the debris they saw was just a normal part of the debris field leaving the Space Station, they just happened to be parked in it for a while. -- Craig Fink Courtesy E-Mail Welcome @ -- On Wed, 20 Dec 2006 05:35:17 +0000, George Evans wrote: in article , Craig Fink at wrote on 12/19/06 3:31 AM: The camera may or may not be a collision issue for the Space Station depending on which way the camera fell relative to the space station. If the camera has less drag, it fell up and may be a collision issue in the future when the Space Station does a reboost. If the camera fell down, more drag, then it's not an issue as I doubt the Space Station is going to deliberately lower it's orbit below the camera. The initial velocity relative to the station is more important than drag. If the camera's initial velocity was generally forward and that it's relative speed was a tenth of a foot per second, then, during the first orbit, will loop up and back about 300 feet above the station, and end about a quarter mile roughly behind the station. Each orbit would take it another quarter mile behind. By the end of just the first day the camera would be six miles back. From the perspective of the station, if the camera has less drag, this pattern will be exaggerated, placing the camera even farther back and somewhat higher each day. In this case, when reboost occurs, it will take the station forward and up above the orbit of the camera. If the camera has more drag that component will eventually cause the camera to cross the station orbit far behind and then safely under the orbit. The only way the camera could even conceivably end up in the vicinity of the station is initially going generally backward with less drag. In this case the camera would loop forward six miles a day but then cross and begin drift back and up. Reboost could conceivably cause the station to converge with the camera. Another interesting possibility is an initial direction perpendicular to the station orbit. In this case the camera will make a close pass ever 45 minutes until differential drag removes it from the area. Of course each pass will be at a tenth of a foot per second. If the camera fell up, then when the Station does a reboost it will have to cross the altitude of the camera. Any future collision problem really has to to with the angle between the velocity vectors. The difference in the velocity vectors will most likely be very small, but the angle between them will most likely be significant. The relative velocity will be huge. There is no way the relative velocity will ever be huge. At the very worst I'm guessing there may be enough to take out an antenna, but nothing life threatening. Up or down, the camera gets a new number in the database. Worst yet, nobody get to see the pictures. This is the worst part of losing the camera. George Evans -- Craig Fink Courtesy E-Mail Welcome @ |
#29
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Why Christer and not Suni for EVA-4?
Starting, undocking, rendezvous would be another level of redundancy. But
how many levels of redundancy are required. Failure one, the tether breaking. The SAFER looks like it has two nozzles for each direction, dual systems? That's two more failures to strand one astronaut. Spacewalking is usally done with the buddy system, that add another three failures to strand two astronauts. Six failures deep before "starting" a Soyuz or Shuttle to go get stranded astronauts. Four without the tethers. And that's not the only way to get a part or astronaut that is slowly drifting away. Boating, nets are handy. Throw lines are specifically designed for that purpose of getting someone back on board. I would think NASA might actually have more of a problem with astronauts accidently on purpose dropping something so they can take a little tethered SAFER cruise. Like someone standing during entry when NASA had no reasonable way of punishing the guy, it was his last mission. Using up a little SAFER propellent at the end of the last spacewalk might even be considered a nice reward for a sucessful mission. Plus, it would make SAFER-2 even safer than SAFER. Use would show faults which leads to better design. -- Craig Fink Courtesy E-Mail Welcome @ -- Craig Fink Courtesy E-Mail Welcome @ |
#30
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Why Christer and not Suni for EVA-4?
The camera may or may not be a collision issue for the Space
Station depending on which way the camera fell relative to the space station. If the camera has less drag, it fell up and may be a collision issue in the future when the Space Station does a reboost. If the camera fell down, more drag, then it's not an issue as I doubt the Space Station is going to deliberately lower it's orbit below the camera. If the camera fell up, then when the Station does a reboost it will have to cross the altitude of the camera. Any future collision problem really has to to with the angle between the velocity vectors. The difference in the velocity vectors will most likely be very small, but the angle between them will most likely be significant. The relative velocity will be huge. Up or down, the camera gets a new number in the database. Worst yet, nobody get to see the pictures. -- Craig Fink Courtesy E-Mail Welcome @ -- Craig Fink Courtesy E-Mail Welcome @ |
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