Ares 1: Lift Off Drift

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kyle_baron

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<p>http://www.orlandosentinel.com/news/space/orl-ares2608oct26,0,561055.story</p><p>The issue is known as "liftoff drift." Ignition of the rocket's solid-fuel motor makes it "jump" sideways on the pad, and a southeast breeze stronger than 12.7 mph would be enough to push the 309-foot-tall ship into its launch tower.<br /><br />Worst case, the impact would destroy the rocket. But even if that doesn't happen, flames from the rocket would scorch the tower, leading to huge repair costs.<br /><br />"We were told by a person directly involved [in looking at the problem] that as they incorporate more variables into the liftoff-drift-curve model, the worse the curve becomes," said one NASA contractor, who asked not to be named because he wasn't authorized to discuss Ares.<br /><br />"I get the impression that things are quickly going from bad to worse to unrecoverable."<br /><br />NASA says it can solve -- or limit -- the problem by repositioning and redesigning the launchpad.<br /><br />Engineers say that would take as much as a year and cost tens of millions of unbudgeted dollars.<br /><br />What happens with Ares I is crucial to the future of the U.S. manned space program -- and of Kennedy Space Center. KSC is looking at thousands of layoffs after the space shuttle is retired in 2010. Its work force won't grow again until a new rocket launches.<br /><br />In addition, huge expenditures on the rocket could bankrupt the agency's moon plans and prompt a new president to halt the program, delaying America's return to space.<br /><br /><strong>Work in progress</strong><br /><br />NASA officials are now looking at ways to speed up the development of Ares and are reluctant to discuss specific problems. But they insist none is insurmountable.<br /><br />"There are always issues that crop up when you are developing a new rocket and many opinions about how to deal with them," said Jeff Hanley, manager of the Constellation program, which includes Ares, the first new U.S. rocket in 35 years.<br /><br />"We have a lot of data and understanding of what it's going to take to build this."<br /><br />Still, Ares' woes have created unprecedented rifts inside the agency.<br /><br />Now several engineers are speaking out, saying Ares should be canceled because it's expensive and potentially dangerous.<br /><br />"It's time for a rethink," said Jeff Finckenor, an award-winning NASA engineer who last month quit the Ares program in frustration over the way the program is being managed.<br /><br />Internal documents and studies obtained by the Orlando Sentinel appear to support concerns expressed by Finckenor and others. Nonetheless, NASA's leaders maintain that Ares will be ready for launch in 2015.<br /><br />"At the highest levels of the agency, there seems to be a belief that you can mandate reality, followed by a refusal to accept any information that runs counter to that mandate," said Finckenor, whose farewell letter to his colleagues denouncing NASA management was posted (without his permission) on NASAWatch.com, an independent Web site.</p><div id="related-topic-article" style="margin-bottom:5px"><h3 class="article-related-topics"><span class="tag-title">Related topic galleries:</span> <span>Cape Canaveral, Rocketry, National Government, George Bush, NASA, Kennedy Space Center, Engineering </span></h3><div id="related-all-topics" style="font-size:90%;margin:-8px5px2px0px">All topics</div></div><span class="promo-msg"></span><p>&nbsp;</p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>http://www.orlandosentinel.com/news/space/orl-ares2608oct26,0,561055.storyThe issue is known as "liftoff drift." Ignition of the rocket's solid-fuel motor makes it "jump" sideways on the pad, and a southeast breeze stronger than 12.7 mph would be enough to push the 309-foot-tall ship into its launch tower.Worst case, the impact would destroy the rocket. But even if that doesn't happen, flames from the rocket would scorch the tower, leading to huge repair costs."We were told by a person directly involved [in looking at the problem] that as they incorporate more variables into the liftoff-drift-curve model, the worse the curve becomes," said one NASA contractor, who asked not to be named because he wasn't authorized to discuss Ares."I get the impression that things are quickly going from bad to worse to unrecoverable."NASA says it can solve -- or limit -- the problem by repositioning and redesigning the launchpad.Engineers say that would take as much as a year and cost tens of millions of unbudgeted dollars.What happens with Ares I is crucial to the future of the U.S. manned space program -- and of Kennedy Space Center. KSC is looking at thousands of layoffs after the space shuttle is retired in 2010. Its work force won't grow again until a new rocket launches.In addition, huge expenditures on the rocket could bankrupt the agency's moon plans and prompt a new president to halt the program, delaying America's return to space.Work in progressNASA officials are now looking at ways to speed up the development of Ares and are reluctant to discuss specific problems. But they insist none is insurmountable."There are always issues that crop up when you are developing a new rocket and many opinions about how to deal with them," said Jeff Hanley, manager of the Constellation program, which includes Ares, the first new U.S. rocket in 35 years."We have a lot of data and understanding of what it's going to take to build this."Still, Ares' woes have created unprecedented rifts inside the agency.Now several engineers are speaking out, saying Ares should be canceled because it's expensive and potentially dangerous."It's time for a rethink," said Jeff Finckenor, an award-winning NASA engineer who last month quit the Ares program in frustration over the way the program is being managed.Internal documents and studies obtained by the Orlando Sentinel appear to support concerns expressed by Finckenor and others. Nonetheless, NASA's leaders maintain that Ares will be ready for launch in 2015."At the highest levels of the agency, there seems to be a belief that you can mandate reality, followed by a refusal to accept any information that runs counter to that mandate," said Finckenor, whose farewell letter to his colleagues denouncing NASA management was posted (without his permission) on NASAWatch.com, an independent Web site.Related topic galleries: Cape Canaveral, Rocketry, National Government, George Bush, NASA, Kennedy Space Center, Engineering All topics&nbsp; <br />Posted by kyle_baron</DIV></p><p><strong>Ok, more negitivism for Ares 1.&nbsp; Let's just deal with it.&nbsp; Maybe a longer swing arm than Apollo had?&nbsp; Maybe the hold down arms that Apollo had?&nbsp; Any other ideas?</strong></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Ok, more negitivism for Ares 1.&nbsp; Let's just deal with it.&nbsp; Maybe a longer swing arm than Apollo had?&nbsp; Maybe the hold down arms that Apollo had?&nbsp; Any other ideas? <br />Posted by kyle_baron</DIV></p><p>IF the problem is real:</p><p>&nbsp;I expect the solution will simply be a wind speed/direction constraint to launch as we had on the Saturn Five and that we have on the Shuttle.</p><p>Hold down restraints that hold the vehicle down after T-0 are not a good option because it would cut into performance and because the SRBs start at max. thrust. </p> <div class="Discussion_UserSignature"> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>IF the problem is real:&nbsp;I expect the solution will simply be a wind speed/direction constraint to launch as we had on the Saturn Five and that we have on the Shuttle. <br />Posted by shuttle_guy</DIV></p><p><strong>A 12.5 mph breeze, isn't much of a wind.&nbsp; Maybe Nasa&nbsp;can "kill 2 birds with 1 stone".&nbsp; Remove the 50' center grass path between the crawlerway, and add&nbsp;stone for the Ares V mass problem.&nbsp; Take that fill from the center path and put it around the perimeter of the Ares 1 launch pad, as berms to redirect the winds.&nbsp; It wouldn't even have to be a complete circular berm.&nbsp; A segmented circle with openings (for roads, pipes, etc.).&nbsp; There appears to be a lot of empty space around the pad 39B:</strong></p><p>&nbsp;http://www-pao.ksc.nasa.gov/kscpao/images//large/06pd0390.jpg</p><p><strong>I'm guessing that the segmented berms would have to be at least 200' high, which is about the height of the SRB.&nbsp; The winds would move up the berms, and over the rocket, from any direction.</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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tanstaafl76

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<p>&nbsp;</p><p>I don't think 200' berms are realistic in that environment.&nbsp; Wouldn't it be easier to build a fence or structure?&nbsp;&nbsp; Won't be cheap in any case.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>A 12.5 mph breeze, isn't much of a wind.&nbsp; Maybe Nasa&nbsp;can "kill 2 birds with 1 stone".&nbsp; Remove the 50' center grass path between the crawlerway, and add&nbsp;stone for the Ares V mass problem.&nbsp; Take that fill from the center path and put it around the perimeter of the Ares 1 launch pad, as berms to redirect the winds.&nbsp; It wouldn't even have to be a complete circular berm.&nbsp; A segmented circle with openings (for roads, pipes, etc.).&nbsp; There appears to be a lot of empty space around the pad 39B:&nbsp;http://www-pao.ksc.nasa.gov/kscpao/images//large/06pd0390.jpgI'm guessing that the segmented berms would have to be at least 200' high, which is about the height of the SRB.&nbsp; The winds would move up the berms, and over the rocket, from any direction. <br />Posted by kyle_baron</DIV></p><p>But the 12.5 mph wind must be from a very tight direction. The chance of this happening is small. Currently the Shuttle can not launch if the cross wind component on the run way exceeds a similar velocity.&nbsp; </p> <div class="Discussion_UserSignature"> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Hold down restraints that hold the vehicle down after T-0 are not a good option because it would cut into performance and because the SRBs start at max. thrust. <br />Posted by shuttle_guy</DIV></p><p>IIRC, Apollo's hold down restraints held the rocket for multiple seconds (2-3?).&nbsp; Because SRB's start at max. thrust, this causes a kick (movement)&nbsp;in the nozzle?&nbsp; I don't think anyone would complain, if the SRB were held for 1/2 sec. do you?<br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;I don't think 200' berms are realistic in that environment.&nbsp; Wouldn't it be easier to build a fence or structure?</DIV></p><p><strong>I don't think so, however a fence on top of a berm is an idea.&nbsp; They could also put a larger berm outside the perimeter fence of Pad 39B.&nbsp; 50' wide, 4-6 ft. deep, by 2.5 mi. is a lot of fill!</strong></p><p>&nbsp;Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;&nbsp; Won't be cheap in any case.&nbsp; <br />Posted by tanstaafl76</DIV></p><p><strong>Agreed.&nbsp; But it's just moving earth.&nbsp; No physics problems here!</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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kyle_baron

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<strong>"Reaction control and roll control will direct the vehicles roll and attitude durring ascent".&nbsp; I got that from a Nasa web page.&nbsp; I'm not sure if this affects pitch or yaw.&nbsp; If it does, why can't this be used to tip the rocket in the opposite direction of drift at liftoff?</strong><br /> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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Zipi

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>IIRC, Apollo's hold down restraints held the rocket for multiple seconds (2-3?).&nbsp; Because SRB's start at max. thrust, this causes a kick (movement)&nbsp;in the nozzle?&nbsp; I don't think anyone would complain, if the SRB were held for 1/2 sec. do you? <br />Posted by kyle_baron</DIV><br /><br />Ares 1 is already underpowered and holding it down will underpower it more. Also think about the impact it will create if you hold it down because it starts&nbsp;at the full power. Since Apollo's booster was liquid powered it could start with lower thrust (I don't know for sure did it start at lower thrust). If you decide to hold down SRB booster it will need massive restraints and perhaps you will need to enforce its casing as well - /> which will cause more mass to the booster as well as you lost power when its firing at the restraints.</p><p>Since I'm not a rocket scientist my comments could be wrong, but I personally feel very confident about this. <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /></p> <div class="Discussion_UserSignature"> </div>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>"Reaction control and roll control will direct the vehicles roll and attitude durring ascent".&nbsp; I got that from a Nasa web page.&nbsp; I'm not sure if this affects pitch or yaw.&nbsp; If it does, why can't this be used to tip the rocket in the opposite direction of drift at liftoff? <br />Posted by kyle_baron</DIV></p><p>&nbsp;</p><p><strong>ROLL</strong> control thrrusters control <strong>ROLL</strong> not pitch or yaw !</p> <div class="Discussion_UserSignature"> </div>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Ares 1 is already underpowered and holding it down will underpower it more. Also think about the impact it will create if you hold it down because it starts&nbsp;at the full power. Since Apollo's booster was liquid powered it could start with lower thrust (I don't know for sure did it start at lower thrust). If you decide to hold down SRB booster it will need massive restraints and perhaps you will need to enforce its casing as well - /> which will cause more mass to the booster as well as you lost power when its firing at the restraints.Since I'm not a rocket scientist my comments could be wrong, but I personally feel very confident about this. <br />Posted by Zipi</DIV></p><p>&nbsp;</p><p>You are correct. That is what I said in different words in&nbsp;an above post.</p><p>This is not a big dea guys. just a wind speed and direction constrain...as i said above as well.</p> <div class="Discussion_UserSignature"> </div>
 
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MarkStanaway

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<p>&nbsp;<br /> <BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> Since Apollo's booster was liquid powered it could start with lower thrust (I don't know for sure did it start at lower thrust).Posted by Zipi</DIV></p><p>Here is an excellent description of a Saturn V liftoff from Davd Woods book 'How Apollo flew to the Moon'.</p><p>'At 8.9 seconds a lift-off command was sent to the Saturn V to begin the ignition sequence for the five F-1 engines at the base of the first stage. The Saturn's instrument unit then sent commands to each engine their timing slightly staggered in order to prevent the launch vehicle sustaining a single jarring ignition transient. First to be commanded was the centre engine followed at quarter second intervals by diagonally opposed pairs of engines. Each engine then went through an elaborate sequence that was carefully choreograohed to minimise rough starting, with all engines having reached full thrust by T-1 second..... The release of the Saturn-V was not instantaneous: it was once described as more an ooze-off than a lift-off. This was in part due to a number of tapered pins mounted to the launch platform which were pulled through dies affixed to the bottom of the S-1C. Their deformation controlled the acceleration of the rocket during the first 15 cm of ascent...... As 3000 tonnes of metal and volatile propellant rose past the umbilical tower it could be seen to lean disconcertingly away as though it were about to go out of control. This was an entirely planned yaw rotation designed to manoeuvre the rocket away from the launch tower in case a swing arm were to fail to retract or a gust of wind were to push the vehicle back towards the unyielding tower. It took about 10 seconds for the entire length of the space vehicle to clear the tower....' </p> <div class="Discussion_UserSignature"> </div>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp; Here is an excellent description of a Saturn V liftoff from Davd Woods book 'How Apollo flew to the Moon'.'At 8.9 seconds a lift-off command was sent to the Saturn V to begin the ignition sequence for the five F-1 engines at the base of the first stage. The Saturn's instrument unit then sent commands to each engine their timing slightly staggered in order to prevent the launch vehicle sustaining a single jarring ignition transient. First to be commanded was the centre engine followed at quarter second intervals by diagonally opposed pairs of engines. Each engine then went through an elaborate sequence that was carefully choreograohed to minimise rough starting, with all engines having reached full thrust by T-1 second..... The release of the Saturn-V was not instantaneous: it was once described as more an ooze-off than a lift-off. This was in part due to a number of tapered pins mounted to the launch platform which were pulled through dies affixed to the bottom of the S-1C. Their deformation controlled the acceleration of the rocket during the first 15 cm of ascent...... As 3000 tonnes of metal and volatile propellant rose past the umbilical tower it could be seen to lean disconcertingly away as though it were about to go out of control. This was an entirely planned yaw rotation designed to manoeuvre the rocket away from the launch tower in case a swing arm were to fail to retract or a gust of wind were to push the vehicle back towards the unyielding tower. It took about 10 seconds for the entire length of the space vehicle to clear the tower....' <br />Posted by MarkStanaway</DIV></p><p>Those were VERY very long 10 seconds !! The first Saturn Five I worked on was the booster for Apollo 14. I had started work at KSC 6 months before. I will never forget those launches. A wonderful experience to see from 3 miles away. The last&nbsp;saturn Five&nbsp;I worked on, the Skylab booster,&nbsp;I did not see launched since I was in the Launch Control center.</p> <div class="Discussion_UserSignature"> </div>
 
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nimbus

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Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Those were VERY very long 10 seconds !! The first Saturn Five I worked on was the booster for Apollo 14. I had started work at KSC 6 months before. I will never forget those launches. A wonderful experience to see from 3 miles away. The last&nbsp;saturn Five&nbsp;I worked on, the Skylab booster,&nbsp;I did not see launched since I was in the Launch Control center. <br /> Posted by shuttle_guy</DIV>That's gotta be pretty itchy, to work so hard on something so cool that needs to function almost perfectly to be successful.. And then to have to watch it ignite and take off from <em>miles </em>away :)<br /> <div class="Discussion_UserSignature"> </div>
 
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samkent

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<p><font size="2">Myabe they can glue a long tube down the side of the booster and push a long rod inside the tube&nbsp; into the ground ??</font></p>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Myabe they can glue a long tube down the side of the booster and push a long rod inside the tube&nbsp; into the ground ?? <br />Posted by samkent</DIV></p><p>&nbsp;</p><p>Or a very very very large coke bottle.<br /></p> <div class="Discussion_UserSignature"> </div>
 
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tanstaafl76

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<p>&nbsp;</p><p>According to the article linked below, the wind would need to be 39mph, not 12.</p><p>http://www.breitbart.com/article.php?id=D944CCKG0&show_article=1</p><p><span class="lingo_region"><p> <em>NASA has been struggling with ways to make the new rocket safer and has come up with possible solutions for controlling its vibrations to prevent injuring the crew, and preventing the rocket from drifting into the launch tower at liftoff. Cook said the latter problem is remote&mdash;<strong>a southerly wind would have to be blowing 39 mph or more</strong>&mdash;and could be controlled through the steering system or with tight wind constraints. </em></p><p><em> Space shuttle commander Brent Jett, director of flight crew operations, said he's sought dissenting opinions from his fellow astronauts, but no one is willing to scrap the Ares rocket.&nbsp;</em> </p></span></p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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JonClarke

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;According to the article linked below, the wind would need to be 39mph, not 12.http://www.breitbart.com/article.php?id=D944CCKG0&show_article=1 NASA has been struggling with ways to make the new rocket safer and has come up with possible solutions for controlling its vibrations to prevent injuring the crew, and preventing the rocket from drifting into the launch tower at liftoff. Cook said the latter problem is remote&mdash;a southerly wind would have to be blowing 39 mph or more&mdash;and could be controlled through the steering system or with tight wind constraints. Space shuttle commander Brent Jett, director of flight crew operations, said he's sought dissenting opinions from his fellow astronauts, but no one is willing to scrap the Ares rocket.&nbsp; &nbsp; <br />Posted by tanstaafl76</DIV></p><p>the phraseology that the media use to report is often subtle but can have a huge impact.&nbsp; for example, the sorty above says:</p><p>"NASA has been struggling with ways to make the new rocket safer" implying that that rocket is unsafe and making it safer is problematic.</p><p>If they had said "NASA has been looking at&nbsp;ways to make the new rocket even safer&nbsp;safer" it would have given a very different impression.</p><p>In such cases you ned to look behind the story and ask "why is such an angle being taken".&nbsp; Who gains, who loses from such reporting?</p><p>In this case there is a clear anti NASA, anti Ares slant.</p><p>Jon<br /></p> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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MarkStanaway

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Those were VERY very long 10 seconds !! The first Saturn Five I worked on was the booster for Apollo 14. I had started work at KSC 6 months before. I will never forget those launches. A wonderful experience to see from 3 miles away. The last&nbsp;saturn Five&nbsp;I worked on, the Skylab booster,&nbsp;I did not see launched since I was in the Launch Control center. <br /> Posted by shuttle_guy</DIV></p><p>When you read the complete description of the elaborate sequence of events involved at lift-off it gives you a new appreciation of the Public Affairs Officer's announcement:&nbsp; "We have cleared the tower!" I always find it fascinating to think that with those five F-1's consuming fuel and oxidizer at a rate of 15 tonnes per second, Saturn V was 150 tonnes lighter by the time it had cleared that tower!</p><p>I envy you for having the privilege of seeing one of these beauties lift-off. The footage and sound from recordings gives me some impression of what it must have been like.</p><p>Mark </p> <div class="Discussion_UserSignature"> </div>
 
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tanstaafl76

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>the phraseology that the media use to report is often subtle but can have a huge impact.&nbsp; for example, the sorty above says:"NASA has been struggling with ways to make the new rocket safer" implying that that rocket is unsafe and making it safer is problematic.If they had said "NASA has been looking at&nbsp;ways to make the new rocket even safer&nbsp;safer" it would have given a very different impression.In such cases you ned to look behind the story and ask "why is such an angle being taken".&nbsp; Who gains, who loses from such reporting?In this case there is a clear anti NASA, anti Ares slant.Jon <br /> Posted by jonclarke</DIV></p><p>Sorry jon I wasn't trying to make commentary on the tone of the article, just thought it was valuable for the 39mph figure, which is obviously a whole lot different than 12mph, and I figure the reporter must have heard it somewhere.&nbsp; Doesn't seem as negative as that Orlando Sentinel article though.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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shuttle_guy

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;According to the article linked below, the wind would need to be 39mph, not 12.http://www.breitbart.com/article.php?id=D944CCKG0&show_article=1 NASA has been struggling with ways to make the new rocket safer and has come up with possible solutions for controlling its vibrations to prevent injuring the crew, and preventing the rocket from drifting into the launch tower at liftoff. Cook said the latter problem is remote&mdash;a southerly wind would have to be blowing 39 mph or more&mdash;and could be controlled through the steering system or with tight wind constraints. Space shuttle commander Brent Jett, director of flight crew operations, said he's sought dissenting opinions from his fellow astronauts, but no one is willing to scrap the Ares rocket.&nbsp; &nbsp; <br />Posted by tanstaafl76</DIV></p><p>&nbsp;</p><p>Your reference article is not correct.&nbsp;</p><p>The 39 mph was the design point for the vehicle before the potential tower impact was found. Now thw requirement is 39 mph as long as thevind speed component into the tower is greater than 12.5 mph.</p> <div class="Discussion_UserSignature"> </div>
 
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tanstaafl76

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Your reference article is not correct.&nbsp;The 39 mph was the design point for the vehicle before the potential tower impact was found. Now thw requirement is 39 mph as long as thevind speed component into the tower is greater than 12.5 mph. <br /> Posted by shuttle_guy</DIV></p><p>Hah, well so much for the Associated Press!</p><p>Happy Friday in any case, I'm sure they'll figure it out. </p> <div class="Discussion_UserSignature"> </div>
 
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shuttle_guy

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<p>As a side note.....wind from the south east is rare at KSC since the launch pads are on the coast where the sea breeze has a major influence.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>As a side note.....wind from the south east is rare at KSC since the launch pads are on the coast where the sea breeze has a major influence.&nbsp; <br />Posted by shuttle_guy</DIV></p><p><strong>Hey SG, care to comment on this article?&nbsp; Apparently, it's a little more complicated, than just wind speed:</strong></p><p>http://www.nasaspaceflight.com/2008/11/ares-i-lift-off-drift-curve-tvc/</p><p>At the base of the rocket, the hot gas flow from the first stage Solid Rocket Booster (SRB) is controlled by a directional nozzle which can gimble to steer the vehicle on a designated path through flight.</p><p>This nozzle is attached in three locations, via a large bearing deep inside the SRB, and two hydraulic actuator rams mounted 90 degrees apart.</p><p>One of these rams controls the pitch angle of the nozzle and the other controls the yaw angle.</p><p>Like balancing a pencil on the end of your finger, the TVC system must balance the thrust as it launches, but at the moment of ignition the 3.6 million pounds of thrust all push against the nozzle.</p><p>On the two sides where the rams are attached, the rams hold the nozzle firmly in place, but on the opposite side of the nozzle, where there are no such devices providing support, the nozzle deflects/rotates by a significant amount.</p><p>This ignition deflection means that the rocket starts its launch with its nozzle pushing the rocket off-center, and the TVC must start to fight this effect from the first moments of the flight. As the rocket begins to climb, the rocket pivots around its center of gravity (near the top of the first stage) and the aft of the rocket is pushed off-line. This is known as &ldquo;fish tailing&rdquo;.</p><p>The TVC computers then counteract that move by gimbaling the nozzle to produce a force to bring the bottom of the rocket back into line, but in the few seconds that takes to occur, the rocket may already have drifted closer to its launch tower.</p><p><strong>I'll say it again, that holding down the skirt for a 1/2 sec. can't be all that bad......when compared to increasing the distance of the vehicle to the tower, or beefing up the tower.</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>
 
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