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#31
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On Jan 6, 7:43*am, jkochko68 wrote:
There was a requirement that it had to have about 200 miles of cross range min. so it could make use of different fields not directly along its glidepath. This might be true (I've never heard of a AOA abort site in Alaska, but I wouldn't be surprised if there was one) but it was not the main imposition on cross range that the USAF put in. The USAF demanded over a thousand miles of cross range for Reference Mission 3A and 3B. Those two missions were for a spacecraft to take off from VAFB, going south, either release or recover a satellite, and land back at VAFB after a single orbit. The 200 mile cross range was b/c thats roughly how far away one pt. on Earth would be after a 90 minute orbit. You can see just from first principles that this must be wrong. The earth takes 24 hours to rotate all the way around. So 90 minutes would be 1/16th of the total rotation. The earth's mean circumference is 40,041 KM. 1/16th of that is 2,502 KM, or 1,555 miles. That is roughly how far away one point on earth would be after a 90 minute orbit. The farther away from the equator you go, the smaller the number, until you get to the Pole (best case) where it's 0, but that's the worst case; average case would be half that, or 777 miles. Perhaps 200 miles of cross range would be enough for an abort to Alaska- but Reference Mission 3A and 3B required landing at VAFB, from whence the Shuttle had come. That was because there simply wasn't enough time to release a sat (or recover one) if you were going to make a landing in Alaska.[1] And at VAFB's latitude, one needs about 1200 miles of cross range to account for the rotation of the earth and have a bit of a safety factor. So that was a major design constraint on the space shuttle. Yeah but dodging multiple sats.,,, and I seriously doubt Is not that hard. For the infamous NORPAC '82 exercise, the USS Midway and USS Enterprise operated for 4-5 days about 200 nm off Petropavlovsk, launching alpha strikes each day (but on the reciprocal heading to the Soviet naval base) without being detected by airplanes, sats, or subs (as best we can tell by Soviet reaction). And that was against the Soviet ship detection capabilities: they invested a heck of a lot more in that than we did, because they were far more threatened by the USN than we were by the fUSSR Navy. They had a great number of Bears, launched quite a few satellites (both RADSATs and Ferrets), etc. So it is surely not impossible. Its likely the task force would not be using the shipping lanes so they would further stand out. Why do you think that? If the enemy knows that avoiding shipping lanes makes you stand out, why wouldn't they use shipping lanes? It's not that hard to be on a shipping lane but not seen by any green ships if you have a 10+ knot speed advantage over them and can run your civ nav radars. Also, bad weather and night are quite handy for hiding in. [1]: RM-3 was built around the concern that multiple orbits by the big huge shuttle would make it easy for the Soviets to figure out the exact orbit of the spy sat, so we wouldn't give them much time to get their tracking perfect by simply doing it so quickly: one pass over the USSR and back down. Now, by 1977 the USAF/NRO seems to have decided that RM-3 wasn't important any more, and focused more on RM-4 (a bit more payload, but not the tight single orbit requirements) after they thought more about how to use spy sats, but the shuttle design was already finalized at that point. Faget's original design track, which would have provided much less cross range (on the order of a few hundred miles) had been binned, in favor of the big heavy delta wings necessary to provide enough lift in the hypersonic region of the flight to get 1500 miles of cross range that the military demanded for RM-3. Chris Manteuffel |
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On Jan 6, 11:43*am, Chris wrote:
On Jan 6, 7:43*am, jkochko68 wrote: There was a requirement that it had to have about 200 miles of cross range min. so it could make use of different fields not directly along its glidepath. This might be true (I've never heard of a AOA abort site in Alaska, but I wouldn't be surprised if there was one) but it was not the main imposition on cross range that the USAF put in. The USAF demanded over a thousand miles of cross range for Reference Mission 3A and 3B. Those two missions were for a spacecraft to take off from VAFB, going south, either release or recover a satellite, and land back at VAFB after a single orbit. The 200 mile cross range was b/c thats roughly how far away one pt. on Earth would be after a 90 minute orbit. You can see just from first principles that this must be wrong. The earth takes 24 hours to rotate all the way around. So 90 minutes would be 1/16th of the total rotation. The earth's mean circumference is 40,041 KM. *1/16th of that is 2,502 KM, or 1,555 miles. That is roughly how far away one point on earth would be after a 90 minute orbit. The farther away from the equator you go, the smaller the number, until you get to the Pole (best case) where it's 0, but that's the worst case; average case would be half that, or 777 miles. Perhaps 200 miles of cross range would be enough for an abort to Alaska- but Reference Mission 3A and 3B required landing at VAFB, from whence the Shuttle had come. That was because there simply wasn't enough time to release a sat (or recover one) if you were going to make a landing in Alaska.[1] And at VAFB's latitude, one needs about 1200 miles of cross range to account for the rotation of the earth and have a bit of a safety factor. So that was a major design constraint on the space shuttle. Yeah but dodging multiple sats.,,, and I seriously doubt Is not that hard. For the infamous NORPAC '82 exercise, the USS Midway and USS Enterprise operated for 4-5 days about 200 nm off Petropavlovsk, launching alpha strikes each day (but on the reciprocal heading to the Soviet naval base) without being detected by airplanes, sats, or subs (as best we can tell by Soviet reaction). And that was against the Soviet ship detection capabilities: they invested a heck of a lot more in that than we did, because they were far more threatened by the USN than we were by the fUSSR Navy. They had a great number of Bears, launched quite a few satellites (both RADSATs and Ferrets), etc. So it is surely not impossible. *Its likely the task force would not be using the shipping lanes so they would further stand out. Why do you think that? If the enemy knows that avoiding shipping lanes makes you stand out, why wouldn't they use shipping lanes? It's not that hard to be on a shipping lane but not seen by any green ships if you have a 10+ knot speed advantage over them and can run your civ nav radars. Also, bad weather and night are quite handy for hiding in. [1]: *RM-3 was built around the concern that multiple orbits by the big huge shuttle would make it easy for the Soviets to figure out the exact orbit of the spy sat, so we wouldn't give them much time to get their tracking perfect by simply doing it so quickly: one pass over the USSR and back down. Now, by 1977 the USAF/NRO seems to have decided that RM-3 wasn't important any more, and focused more on RM-4 (a bit more payload, but not the tight single orbit requirements) after they thought more about how to use spy sats, but the shuttle design was already finalized at that point. Faget's original design track, which would have provided much less cross range (on the order of a few hundred miles) had been binned, in favor of the big heavy delta wings necessary to provide enough lift in the hypersonic region of the flight to get 1500 miles of cross range that the military demanded for RM-3. Chris Manteuffel Smaller distance at higher latitudes. One source gives 9,905.2 miles, ie your 1/16th would be 619 miles. If you are only going the distance from Vandenberg to Alaska the distance is something like 1500 miles. The speed of an orbital launch is about 26000 feet per second, traveling that 1500 miles in about 5 minutes. Your precession is then in the 165 mile region, fudging makes it 2000 miles. |
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#34
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"tankfixer" wrote in message
... In article 01fc4d1c-6a6e-4840-b78a-f85f58d971a7 @j19g2000yqk.googlegroups.com, says... On Jan 5, 9:04 pm, "David E. Powell" wrote: On Jan 5, 8:14 pm, Dan wrote: Chris wrote: On Jan 5, 6:15 pm, frank wrote: SOSUS was retired and shut down. Little thing with Walker giving away the candy store to the SU on how we tracked subs. Completely wrong. SOSUS is still operational, though there are fewer NAVFAC's operating and now SURTASS is generally preferred: both because of the operational flexibility that the T-AGOS have and the vastly easier maintenance (and upgrade) opportunities that they provide. Really? Then how come the SURTASS fleet has been retired? We once had over 24 ships, now there are 4. And Walker doesn't really match the timelines for when the IUSS (the acronym for the combination of the two) started to decline: the fall of the USSR and the dramatic drop in the number of submarines we needed to track in the open ocean does (the drawdown seems to start in the mid 1990's). Chris Manteuffel Back during the depths of the Cold War I thought it would have been fun to tweak the Soviet's version of SOSUS by deliberately sinking a retired U.S. submarine in such a way the Soviets would detect it. It would have been a gas to sit back and watch the Soviets going nuts trying to figure out what happened. Dan, U.S. Air Force, retired Like a retired GUPPY (Or pre Guppy) sunk in a deep spot right near their cable? And reveal that we knew where their cable was, what it was used for and perhaps that we were running submarines they couldn't detect into their defense zone? Not that we would EVER do such things.. ;') SOSUS has been integrated into IUSS (Integrated Undersea Surveillance System), a small part of a larger network. So, SOSUS is still alive, but much smaller due to a much smaller ASW threat. Also, newer systems had to be developed to counter quieter submarines. http://www.fas.org/irp/program/collect/iuss.htm Mark |
#36
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