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Atlas5 vs Shuttle ( launch window)
On 12/5/15 12:17 AM, JF Mezei wrote :
On 2015-12-04 20:50, Alain Fournier wrote: relatively slowly. Then go to a LEO that isn't over the equator but closer to the equator than the launch site. So in this particular case, it is the second stage or even Cygnus that has the added performance that gives a 30 minute window ? I was responding to the question about geostationary satellites. In the case of a rocket launch to ISS, the difference in orbital speeds at ISS and at very low Earth orbit is not that big. Once in orbit, you do save some by doing a plane change at apogee but not much. In this case the plane change would be done in early launch phase. But it doesn't do much of a difference where the added performance comes from. If you do your plane change right after lift-off, your first stage won't get your second stage quite as fast. This can be compensated by having a more powerful first stage or by a more powerful second stage, or some other stage. Also, it isn't only a matter of how much power the rocket has. If you do your plane change early in the launch phase you can run into aerodynamic problems. One way that you could *theoretically* do the plane change is to go due east right after launch, then when you are at the right plane you go up, after what you resume your acceleration to achieve orbit. If it wasn't for the atmosphere that wouldn't be too bad a way to do it (not good, but not too bad). But since there is an atmosphere you can't do that. The shuttle probably needed to stay further away from that flight plan than Atlas 5 does. In other words, I think that the shuttle had to go up higher before taking care of the plane change than Atlas 5 does. Alain Fournier |
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Atlas5 vs Shuttle ( launch window)
On 12/5/15 8:43 PM, JF Mezei wrote :
On 2015-12-05 11:32, Alain Fournier wrote: problems. One way that you could *theoretically* do the plane change is to go due east right after launch, then when you are at the right plane you go up, after what you resume your acceleration to achieve orbit. But in the case of ISS, when you launch late, the orbital plane is west of you, so you don't want to launch east, you want to launch north to intersect with orbital plane and then veer to 51°. The problem with launching "north" is that there is something called "land" on which your spent rockets (or possibly self desruct (aka range safety) will result in debris falling on homes, cows and highways. It seems they were skirting with that problem. There has been a sighting of the fall of the booster in Halifax. So yes, they did launch quite northward. See: http://www.cbc.ca/news/canada/nova-s...here-1.3354598 Alain Fournier |
#3
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Atlas5 vs Shuttle ( launch window)
In sci.space.policy message , Tue, 8 Dec
2015 19:39:12, Alain Fournier posted: The problem with launching "north" is that there is something called "land" on which your spent rockets (or possibly self desruct (aka range safety) will result in debris falling on homes, cows and highways. It seems they were skirting with that problem. There has been a sighting of the fall of the booster in Halifax. So yes, they did launch quite northward. The Shuttle, when destined to ISS, launched roughly along but offshore from the (American) East Coast. One day, soon after effective sunset, I saw, from outer SW London, both the Orbiter and its External Tank passing separately not far from overhead and to the north of me; they must have crossed over populous parts of North London, including where I lived as a young child with my parents and with their parents, siblings, and other family nearby. -- (c) John Stockton, nr London, UK. Mail via homepage. Turnpike v6.05 MIME. Web - FAQqish topics, acronyms and links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. |
#4
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Atlas5 vs Shuttle ( launch window)
On 12/10/15 6:36 PM, Dr J R Stockton wrote :
In sci.space.policy message , Tue, 8 Dec 2015 19:39:12, Alain Fournier posted: The problem with launching "north" is that there is something called "land" on which your spent rockets (or possibly self desruct (aka range safety) will result in debris falling on homes, cows and highways. It seems they were skirting with that problem. There has been a sighting of the fall of the booster in Halifax. So yes, they did launch quite northward. The Shuttle, when destined to ISS, launched roughly along but offshore from the (American) East Coast. One day, soon after effective sunset, I saw, from outer SW London, both the Orbiter and its External Tank passing separately not far from overhead and to the north of me; they must have crossed over populous parts of North London, including where I lived as a young child with my parents and with their parents, siblings, and other family nearby. Obviously they have to accept to fly over populated areas after some time. I wonder what is considered to be safe. Maybe the launcher is considered to be high enough once over Nova Scotia to go over populated areas. Does anyone know who decides what is safe in that regard and what are the guidelines? Alain Fournier |
#5
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Atlas5 vs Shuttle ( launch window)
In sci.space.policy message
web.com, Thu, 10 Dec 2015 20:13:37, JF Mezei jfmezei.spamnot@vaxinatio n.ca posted: On 2015-12-10 18:36, Dr J R Stockton wrote: One day, soon after effective sunset, I saw, from outer SW London, both the Orbiter and its External Tank passing separately not far from overhead and to the north of me; they must have crossed over populous parts of North London, including where I lived as a young child with my parents and with their parents, siblings, and other family nearby. By the time it flies over England, the orbiter and the tank are orbital. No "range safety" (aka self destruct) risk and no risk of major malfunction causing debris to fall. Agreed to that, as written. But a failure to complete the desired acceleration earlier, at the final stage of SSME-powered flight would lead to failure to quite achieve orbit, with re-entry along some part of the intended track. The probability of anything coming down along the UK portion of that track was non-zero, but small. -- (c) John Stockton, nr London, UK. Mail via homepage. Turnpike v6.05 MIME. Web - FAQqish topics, acronyms and links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. |
#6
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Atlas5 vs Shuttle ( launch window)
In sci.space.policy message , Thu, 10 Dec
2015 20:22:05, Alain Fournier posted: On 12/10/15 6:36 PM, Dr J R Stockton wrote : In sci.space.policy message , Tue, 8 Dec 2015 19:39:12, Alain Fournier posted: The problem with launching "north" is that there is something called "land" on which your spent rockets (or possibly self desruct (aka range safety) will result in debris falling on homes, cows and highways. It seems they were skirting with that problem. There has been a sighting of the fall of the booster in Halifax. So yes, they did launch quite northward. The Shuttle, when destined to ISS, launched roughly along but offshore from the (American) East Coast. One day, soon after effective sunset, I saw, from outer SW London, both the Orbiter and its External Tank passing separately not far from overhead and to the north of me; they must have crossed over populous parts of North London, including where I lived as a young child with my parents and with their parents, siblings, and other family nearby. Obviously they have to accept to fly over populated areas after some time. I wonder what is considered to be safe. Maybe the launcher is considered to be high enough once over Nova Scotia to go over populated areas. Does anyone know who decides what is safe in that regard and what are the guidelines? (1) Nova Scotia is not part of the USA. (2) Testing with a piece of string and a rather small globe appears to demonstrate that a great circle from any part of the Florida peninsula to any part of England does not cross any part of Canada. It might cross Saint Pierre et Miquelon, but one from CCAFS to London would not do so. (3) Can Google Maps or another such tool show great circle paths? It shows an air route London, United Kingdom to Melbourne, FL, USA - which seems to miss Canada by too much to be a Great Circle. -- (c) John Stockton, Surrey, UK. Turnpike v6.05 MIME. Merlyn Web Site - FAQish topics, acronyms, & links. |
#7
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Atlas5 vs Shuttle ( launch window)
On 12/12/15 6:35 PM, Dr J R Stockton wrote :
In sci.space.policy message , Thu, 10 Dec 2015 20:22:05, Alain Fournier posted: On 12/10/15 6:36 PM, Dr J R Stockton wrote : In sci.space.policy message , Tue, 8 Dec 2015 19:39:12, Alain Fournier posted: The problem with launching "north" is that there is something called "land" on which your spent rockets (or possibly self desruct (aka range safety) will result in debris falling on homes, cows and highways. It seems they were skirting with that problem. There has been a sighting of the fall of the booster in Halifax. So yes, they did launch quite northward. The Shuttle, when destined to ISS, launched roughly along but offshore from the (American) East Coast. One day, soon after effective sunset, I saw, from outer SW London, both the Orbiter and its External Tank passing separately not far from overhead and to the north of me; they must have crossed over populous parts of North London, including where I lived as a young child with my parents and with their parents, siblings, and other family nearby. Obviously they have to accept to fly over populated areas after some time. I wonder what is considered to be safe. Maybe the launcher is considered to be high enough once over Nova Scotia to go over populated areas. Does anyone know who decides what is safe in that regard and what are the guidelines? (1) Nova Scotia is not part of the USA. Yes, I think that is an important point (from NASA's perspective). (2) Testing with a piece of string and a rather small globe appears to demonstrate that a great circle from any part of the Florida peninsula to any part of England does not cross any part of Canada. It might cross Saint Pierre et Miquelon, but one from CCAFS to London would not do so. I think you are either misplacing St-Pierre et Miquelon or the limits of Canada. If it goes over St-Pierre et Miquelon, it will go over Newfoundland which is part of Canada. (3) Can Google Maps or another such tool show great circle paths? It shows an air route London, United Kingdom to Melbourne, FL, USA - which seems to miss Canada by too much to be a Great Circle. We aren't really talking of a rocket following a Great Circle here. We are talking of a rocket launching late in its launch window that has to do a plane change to get to the orbit of ISS. Early in launch it goes more northward and then turns a little eastward to do the plane change. After having completed the plane change, the trajectory still isn't really a Great Circle, it is a Great Circle that is slipping westward as Earth rotates. But if you find an app or web site that can overlay Great Circles over a map, I would like to see that. If you find an app or web site that can overlay orbital paths on a map it is even better. Alain Fournier |
#8
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Atlas5 vs Shuttle ( launch window)
On 12/12/15 10:05 PM, JF Mezei wrote :
Circles over a map, I would like to see that. If you find an app or web site that can overlay orbital paths on a map it is even better. Designed for flying but could be of use. http://gc.kls2.com/ (from there you can go to newer version of it). If you enter MCO-LHR (Orlando to London) you get a good great circle. London is at 51.5 which is pretty good approximation of the ISS orbit, but not clear if this represents the highest latitude in that path. Here is an example on the new interface: http://www.gcmap.com/mapui?P=MCO-LHR...SU=kts&RS=best Thank you JF. Alain Fournier |
#9
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Atlas5 vs Shuttle ( launch window)
In sci.space.policy message , Sat, 12 Dec
2015 20:10:23, Alain Fournier posted: (2) Testing with a piece of string and a rather small globe appears to demonstrate that a great circle from any part of the Florida peninsula to any part of England does not cross any part of Canada. It might cross Saint Pierre et Miquelon, but one from CCAFS to London would not do so. I think you are either misplacing St-Pierre et Miquelon or the limits of Canada. If it goes over St-Pierre et Miquelon, it will go over Newfoundland which is part of Canada. Agreed. My globe is too little to handle well the case of a territory so small with a name so long. -- (c) John Stockton, Surrey, UK. Turnpike v6.05 MIME. Merlyn Web Site - FAQish topics, acronyms, & links. |
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