Ares 1: Lift Off Drift

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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The flexseal surrounds the nozzle, near the throat (forward).&nbsp; The actuators are about midway down the nozzle, The flexseal serves to determine the pivot poiint of the nozzle, and in the case of the shuttle is a bit aft of the flexseal itself -- the flexseal basically consists of a set of sections of concentric spherical shells and the center of those spheres is the pivot point.&nbsp; The actuators serve primarily to apply a force normal to the axis of the nozzle, creating a torque which causes the nozzle to rotate about the pivot point.&nbsp; The construction of the flexseal serves to maintain a gas seal on the combustion chamber.During the ignition transient the chamber is pressurized and a portion of that pressure is reacted by the nozzle structure and flexseal internal to the motor.&nbsp; That pressurization compresses the flexlseal a bit, and thereby causes the actuators, which are fixed in length at that time, to exert a force with a resultant torque on the nozzle.&nbsp; That torque causes a small rotation, which is the difference between cold null and hot null.&nbsp; Once the motor has reached operating pressure there is no longer a change in the torque from the fixed actuators and things progress from there in a normal fashion.&nbsp; So the question of the duration of the rotation caused by the difference between cold null and hot null is equivalent to the question of the duration of the ignition transient.&nbsp; I don't have the SRB ignition transient curve in front of me, but I think it ought to be over in&nbsp;less than a second (I am not certain of this however).&nbsp; My guess, lacking hard data, is that your 1/2 second estimate is in the ball park. The actuator is not at all a shock absorber.&nbsp; It is in fact very very stiff and needs to be.&nbsp; The best everyday analog would be a hydraulic jack.&nbsp; It really is basically a hydraulic jack with a high pressure fluid source and an electrically conntrolled valve to control the forces.Holding down the vehicle while the motor is firing has other implications.&nbsp; It comes up to pressure pretty fast and is exhausting a lot of very hot gas.&nbsp; It the vehicle is held down that hot gas will impinge on the aft end of the motor and heat things up pretty quick -- rather a hurricane of gas and glowing alumina that can cut metal pretty quickly.&nbsp; You might have a problem that is more severe than the fishtailing that you are trying to cure.&nbsp;&nbsp;If one accounts for the difference between cold null and hot null it is possible to create a straight trajectory during ignition.&nbsp; On the Peacekeeper missile we did that and managed a hot fly-out of the third stage with a very large nozzle from the interstage.&nbsp; That required a very straight fly-out, almost any significant tip-off would have damaged the nozzle, which was a relatively fragile carbon-carbon design.Dealing with the actual dynamics is probably preferable than trying to eliminate them and living with unintended consequences. <br />Posted by DrRocket</DIV></p><p><strong>Thank you.&nbsp;&nbsp;&nbsp;That's an excellent analysis to further clarify the flexseal, actuator, nozzle (TVC) system.&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /></strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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MeteorWayne

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<p>Thanx Dr Rocket. An incredible (well actually credible!) amount of detail in the process.</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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lampblack

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The flexseal surrounds the nozzle, near the throat (forward).&nbsp; ...<br /> Posted by DrRocket</DIV></p><p>Thanks... it's very nice to read these sorts of detailed explanations from guys who actually know what they're talking about. </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> <font color="#0000ff"><strong>Just tell the truth and let the chips fall...</strong></font> </div>

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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Holding down the vehicle while the motor is firing has other implications.&nbsp; It comes up to pressure pretty fast and is exhausting a lot of very hot gas.&nbsp; It the vehicle is held down that hot gas will impinge on the aft end of the motor and heat things up pretty quick -- rather a hurricane of gas and glowing alumina that can cut metal pretty quickly.&nbsp; You might have a problem that is more severe than the fishtailing that you are trying to cure.&nbsp; Dealing with the actual dynamics is probably preferable than trying to eliminate them and living with unintended consequences. <br />Posted by DrRocket</DIV></p><p><strong>A couple more questions:</strong></p><p><strong>1.&nbsp; Is the exhaust from an SRB motor hotter than the exhaust from an LOX-LH2 motor?&nbsp; </strong></p><p><strong>2.&nbsp; "Hot gas impinging on the aft end of the motor....that can cut metal pretty quickly".&nbsp; I assume that you are talking about back pressure.&nbsp; Therefore, how much (and how long) the back pressure remains in the SRB (with out damage) is an unknown variable?</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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Testing

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<p><br />Posted by DrRocket[/QUOTE]</p><p>Thankyou Sir for the accurate and &nbsp;descriptive&nbsp; rendition of what occurs at ignition. Carry on.</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'>I am not talking about back pressure in the motor.&nbsp; In fact the exhaust gasses from the rockets are moving at the local speed of sound at the throat, and there is essentially no gas dynamic communication between anything downstream of the throat and the combustion chamber upstream&nbsp;of it.I am talking about the effects of gas that&nbsp; would impinge on the launch pad and rebound back towards the motor, or radiation from the plume back to the aft dome region as a result of back pressure in the flame duct of the launch pad or near the nozzle exit plane.&nbsp; I am also talking about radiation from nearby structure as it is heated by the plume and together with the plume creates a little radiation oven.&nbsp; <br />Posted by DrRocket</DIV></p><p><strong>Thanks once again Dr. Rocket.&nbsp; Therefore, it is the area directly beneath the nozzle, which would cause the backpressure, if the SRB is held down.&nbsp; This area is a concrete or fire brick, or a combination of both, I assume.&nbsp; One way is to modify that area beneath the nozzle.&nbsp; A deep narrow hole, the diameter of the SRB (12') should do the trick.&nbsp; Maybe 100' deep, assuming the speed of the gas discharge slows and cools the farther it is from the nozzle.&nbsp; Line it with the fire brick-problem solved.&nbsp; Feel free to criticize at this time, I know you don't have a problem with that!&nbsp; Just keep in mind, we're talking a 1/2 second time interval.</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thanks once again Dr. Rocket.&nbsp; Therefore, it is the area directly beneath the nozzle, which would cause the backpressure, if the SRB is held down.&nbsp; This area is a concrete or fire brick, or a combination of both, I assume.&nbsp; One way is to modify that area beneath the nozzle.&nbsp; A deep narrow hole, the diameter of the SRB (12') should do the trick.&nbsp; Maybe 100' deep, assuming the speed of the gas discharge slows and cools the farther it is from the nozzle.&nbsp; Line it with the fire brick-problem solved.&nbsp; Feel free to criticize at this time, I know you don't have a problem with that!&nbsp; Just keep in mind, we're talking a 1/2 second time interval. <br />Posted by kyle_baron</DIV></p><p>Holding it down</p><p>1) Won't do a lot of good land is not necessary if you simply extend the actuators to hot null and let the nozzle center itself as the motor pressurizes. As I mentioned that has worked quite well in the past.</p><p>2)&nbsp; Might be a bit harder to do than you think.&nbsp; That motor produces a lot of thrust very quickly -- a few milliseconds and the thrust is pretty high.&nbsp; The explosive bolts that hold the SRBs down on the shuttle failed to fire on launch -- didn't slow things down much.&nbsp; There is potential to tear up thing that you didn't plan on.</p><p>3)&nbsp; Has the potential to be counter-productive if you actually do hold the motor down while the hot gasses are exhausting.&nbsp; There are potential gas dynamic effects that might well damage the nozzle or actuators.&nbsp; We had issues with that on Titan -- did not damage the nozzle, but were a bit lucky in that regard and modified the design for later launches to avoid problems.</p><p>As usual, it would be better to let the professionals handle this and stifle the urge for bad junior engineering by amateurs who don't know what they are doing.</p> <div class="Discussion_UserSignature"> </div>

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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Nasa doesn't know this???&nbsp; Then why all the concern?&nbsp; "Let the nozzle center itself as the motor pressurizes."&nbsp; At this point, I assume&nbsp;(milliseconds)&nbsp;there isn't enough thrust to cause the fish tailing?&nbsp;Between #1 and #2 it seems that you're contradicting yourself.&nbsp; Now with in a few milliseconds, the thrust is high.[/quote]</p><p>It doen't take very long to get an appreciable thrust when your steady state is over 2 million pounds.</p><p>
&nbsp;There are actually 2 sets of (qty-4) studs.&nbsp; One set on the&nbsp;MLP and one set on the aft skirt.&nbsp; An explosive nut is held in between.&nbsp; Info from this link:&nbsp; &nbsp;http://www-pao.ksc.nasa.gov/kscpao/nasafact/count3teaf.htmYes, it would tear a hole in the skirt, but that wouldn't be life threatening, unless the hole was near a actuator arm or bracket (which I doubt is the case).&nbsp; The real issue, is the amount of thrust that the studs and skirt can take.&nbsp; The 3 SSME's produce 1.2 million lbs.(the studs are holding for several seconds here)&nbsp;while a single SRB produces 2.8 million lbs.&nbsp; Info from this link:&nbsp; &nbsp;http://en.wikipedia.org/wiki/Space_shuttleIMO, <strong>1/2 sec. out of 120 isn't that counter productive</strong>.
</p><p>What is that supposed to mean?&nbsp; The issue is not TIME, it is potential damage to mission-critical hardware.&nbsp; What I said is that you can't hold the SRB for very long agains the thrust generated with a few explosive bolts.</p><p>&nbsp;</p><p>
&nbsp;And remember, there are 1,000's of gallons of water that is dumped and sprayed on the MLP to mitigate the hot gasses.&nbsp; Did the Titan missle have that?Professionals seldom follow the KISS Principle, and that's where us amateurs really shine. <br />Posted by kyle_baron</DIV></p><p>Titan had LOTS of water.&nbsp; But the issue was reflected pressure waves in the flame bucket which can create large loads on the structure of the nozzle.&nbsp; That is not amenable to analysis, and we had some world-class experts try to perform such an analysis.</p><p>Professionals do in fact follow the KISS principle.&nbsp; Amateurs, do not seem to recognize the difference between an idea that is simple and effective and one that is just siimple.&nbsp; Being simple, Kyle, is not always a virtue.&nbsp; Siimple people tend to be, simple.&nbsp; </p><p>If you feel that you are shining, I suggest some immediate professional help.&nbsp; Been around radiation lately ?<br /></p> <div class="Discussion_UserSignature"> </div>

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vulture4

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<p>>>>Professionals do in fact follow the KISS principle.</p><p><strong>>>Give me an example.</strong> </p><p>1. Ed Heinemann and the A-4 Skyhawk</p><p>2. John R. Boyd and the F-16 </p><p>3. Burt Rutan and the Spaceship 1 and 2</p><p>&nbsp;</p>

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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>>>>Professionals do in fact follow the KISS principle.>>Give me an example. 1. Ed Heinemann and the A-4 Skyhawk2. John R. Boyd and the F-16 3. Burt Rutan and the Spaceship 1 and 2&nbsp; <br />Posted by vulture4</DIV></p><p><strong>Interesting, that you didn't mention any examples&nbsp;for Nasa.&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-surprised.gif" border="0" alt="Surprised" title="Surprised" /></strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I'm sure you did have some world class experts perform an analysis.&nbsp; However, that sounds like a dumb problem to have.&nbsp; Why isn't the launch pad and flame trench designed to remove the gasses and pressure waves?&nbsp; Maybe my deep narrow hole beneath the nozzle (the nozzle that &nbsp;sits 10-20' above the hole, on a MLP) would do the trick?</DIV></p><p>No Kyle the people who designed the rocket and the launch pad were not dumb.&nbsp; And the flame bucket and acoustic supression system were quite a bit larger than what you suggest.&nbsp; It is a matter of complex gas dynamics.&nbsp; You really do need to learn some physics.&nbsp; The people involved in addressing this problem had much more education and were one hell of a lot smarter than you.&nbsp; On a bad day.&nbsp; With a headache.&nbsp; And no sleep.&nbsp; With one hand tied behind their back.&nbsp; </p><p><br /><br />&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'>No Kyle the people who designed the rocket and the launch pad were not dumb.&nbsp; And the flame bucket and acoustic supression system were quite a bit larger than what you suggest.&nbsp; It is a matter of complex gas dynamics.&nbsp; You really do need to learn some physics.&nbsp; The people involved in addressing this problem had much more education and were one hell of a lot smarter than you.&nbsp; On a bad day.&nbsp; With a headache.&nbsp; And no sleep.&nbsp; With one hand tied behind their back.&nbsp; &nbsp; <br />Posted by DrRocket</DIV></p><p><strong>Making broad (general) statements without specific examples, adds up to zilch.&nbsp; Lay some complex gas dynamics on us.&nbsp; Your insults were amusing.&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-tongue-out.gif" border="0" alt="Tongue out" title="Tongue out" />&nbsp; </strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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nimbus

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Making broad (general) statements without specific examples, adds up to zilch.&nbsp; Lay some complex gas dynamics on us.&nbsp; Your insults were amusing.&nbsp; &nbsp; <br /> Posted by kyle_baron</DIV><br />You really aren't giving someone with his experience and age the respect he's due, when you troll him with these off the wall assertions (e.g. that nasa engineers don't know what they're on about) and requests for supporting evidence while not making an ounce of effort to meet him halfway.</p><p>&nbsp;That and the large bold text with the same one-liner over and over again on every one of your posts..</p> <div class="Discussion_UserSignature"> </div>

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rubicondsrv

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The people involved in addressing this problem had much more education and were one hell of a lot smarter than you.&nbsp; On a bad day.&nbsp; With a headache.&nbsp; And no sleep.&nbsp; With one hand tied behind their back.&nbsp; &nbsp; <br />Posted by DrRocket</DIV><br /><br />that was a bit harsh.</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>that was a bit harsh.&nbsp; <br />Posted by rubicondsrv</DIV></p><p>No it wasn't.&nbsp; It was a sugar-coated and accurate response to one of Kyle's typical attacks on professionals.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><strong>Professionals seldom follow the KISS Principle, and that's where us amateurs really shine</strong></DIV></p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><strong>I'm sure you did have some world class experts perform an analysis.&nbsp; However, that sounds like a dumb problem to have.</strong></DIV></p><p>&nbsp;</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> </div>

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rubicondsrv

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>No it wasn't.&nbsp; It was a sugar-coated and accurate response to one of Kyle's typical attacks on professionals.&nbsp;&nbsp; <br />Posted by DrRocket</DIV><br /><br />nevermid.</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'>No it wasn't.&nbsp; It was a sugar-coated and accurate response to one of Kyle's typical attacks on professionals.&nbsp;&nbsp; <br />Posted by DrRocket</DIV></p><p><strong>No Dr. Rocket, it was just a response to you.&nbsp; Other professionals, don't DISRESPECT people who aren't professionals.&nbsp; Shuttle Guy is a perfect example.</strong></p><strong><p>&nbsp;</p><p>&nbsp;</p><p><br /><br />&nbsp;</p></strong> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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MeteorWayne

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<p>Mod Hat On:</p><p>-------</p><p>OK, that's enough. To both of you, lets please focus on the issue at hand, and tone down the personal stuff.</p><p>You cooperation in advance is appreciated. And highly recommended.</p><p>Thanx</p><p>MW</p><p>----------</p><p>Mod Hat Off</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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kyle_baron

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You really aren't giving someone with his experience and age the respect he's due,</DIV></p><p><strong>Wait a minute, back up.&nbsp; Dr. Rocket = Respect????&nbsp; Give me a break.&nbsp; He disrespects anyone who disagrees&nbsp;with him.&nbsp; Not just me.</strong></p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;when you troll him with these off the wall assertions (e.g. that nasa engineers don't know what they're on about) and requests for supporting evidence while not making an ounce of effort to meet him halfway.</DIV>&nbsp;</p><p><strong>I said the problem was dumb.&nbsp; He twisted my words around, to say that people were dumb. </strong></p><p><strong>Here's exactly what I said:</strong></p><p><strong>I'm sure you did have some world class experts perform an analysis.&nbsp; However, that sounds like a dumb problem to have.&nbsp; Why isn't the launch pad and flame trench designed to remove the gasses and pressure waves?&nbsp;</strong></p><p><strong>Here's exactly what he said:</strong></p><p>No Kyle the people who designed the rocket and the launch pad were not dumb.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That and the large bold text with the same one-liner over and over again on every one of your posts.. <br />Posted by nimbus</DIV></p><p><strong>Thank you for pointing that out.&nbsp; I've toned it down.</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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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Mod Hat On:-------OK, that's enough. To both of you, lets please focus on the issue at hand, and tone down the personal stuff.You cooperation in advance is appreciated. And highly recommended.ThanxMW----------Mod Hat Off <br />Posted by MeteorWayne</DIV></p><p><strong>I was writing my response to Nimbus as you were writing this (which I didn't see).&nbsp; Understood.</strong><br /></p> <div class="Discussion_UserSignature"> <p><font size="4"><strong></strong></font></p> </div>

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MeteorWayne

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Posted by kyle_baron</DIV></p><p>Mod Hat On:</p><p>----------<br />Uhummm, please read my previous message.</p><p>Wayne</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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MeteorWayne

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I was writing my response to Nimbus as you were writing this (which I didn't see).&nbsp; Understood. <br />Posted by kyle_baron</DIV><br /><br />I thought it might have been a timing issue.</p><p>Thanx</p><p>Wayne</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

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