NO safe liftoff-abort-mode for 1st stage CLV solid fuel SRB

[haywood]

Excellent point Drwayne!<br />

 

[gaetanomarano]

<br />exactly... read the posts... they are about the 20 years ago Challenger disaster

 

[gaetanomarano]

<br />the discussion shifted to the Shuttle and Challenger disaster... but it was about liquid/solid engine for 1st stage of CLV... and about rockets that can stop at lift-off or can't

 

[tap_sa]

<font color="yellow">"and about rockets that can stop at lift-off or can't"</font><br /><br />Perhaps today you get it that SRB doesn't need the ability to stop 'at liftoff' because that's the very moment <i>it starts</i>?

 

[dobbins]

Historically rockets that stopped at liftoff when they weren't supposed to is the cause of the launchpad explosions that you were so worried about. This is something that won't happen with a solid fuel 1st stage.<br /><br />As usual you managed to get it backwards in your never ending quest to find some straw to grasp at in your campaign for a spaceplane that only interests a handful of spaceplane fanatics.<br /><br />

 

[gaetanomarano]

<br />true... the exact moment is "at 1st stage engine burning" (if some sensors or computers need a launch abort) like was (five times) with Shuttles' SSME... a liquid engine can stop (saving crew, capsule, rocket and billions, without any 10G LAS' ejection) ...SRB can't

 

[gaetanomarano]

<br />as I've explained a dozen times (same question, same answer) the "problem" that need a launch abort at lift-off DON'T NEED to be in the 1st stage (that may work PERFECTLY) but in one of the thousands parts of the (completely new) CEV/SM/CLV system<br /><br />the "problem" that may need a launch abort may happen at 1st test launch or at launch #8 (with crew)<br /><br />with Apollo the problems happen with #1 and, after some years of perfect work, with #13<br /><br />the first (both test & real in one launch) Shuttle's flight was perfect, a giant problem happen only FIVE years after<br /><br />NO ONE can predict the day when a severe problem will happen (that need a launch abort at lift off) ...an engine that can stop is for THAT (unknown) day... and five aborted Shuttles launches + two Shuttles' disasters clearly demonstrates that (unexpected) "problems" MAY HAPPEN with rockets' launches

 

[drwayne]

I believe I was told that there was a shake up at the weather team after Challenger...<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[dobbins]

An abort AT liftoff is the last thing you want. That all but insures damage to the vehicle.<br /><br />Liquid fuel rockets are fired PRIOR to liftoff to build up thrust. Solids are fired AT liftoff. They don't have to be shut down in those last few seconds before liftoff because they aren't lit.<br /><br />The problem with solids comes AFTER liftoff, not BEFORE it, not DURING it, AFTER it.<br /><br />The problem is they can't be shutdown in the early stage of flight if the vehicle is off course. With a liquid fuel rocket the Launch Abort System can shut down the booster so it's guidance system has a simple trajectory to use for the capsule. With a solid you have the extra complication of figuring a trajectory from an unstable starting point.<br /><br />

 

[gaetanomarano]

<br />I can only suggest you to read this post http://uplink.space.com/showthreaded.php?Cat=&Board=missions&Number=414018&page=0&view=collapsed&sb=5&o=1&vc=1<br /><br />the problem that need a launch abort DON'T NEED to come from 1st stage engine!

 

[tap_sa]

<font color="yellow">"There is not differance between a solid and liquid if you need to stop it one second after liftoff."</font><br /><br />Well, contrary to solid motors it is possible to shut down the liquid engine without effectively breaking it. Buuut after a few more seconds it doesn't matter anyway... <img src="/images/icons/wink.gif" />

 

[gaetanomarano]

<br />like with the five aborted Shuttles' launches... the engine must stop a few seconds after its ignition because, when it burns, the entire "system" (stages, capsules, sensors, computers, tanks, electronics, etc. etc. etc.) will receive a giant "shock" with "high vibration" and a "full system stress" that may damage "something" or simply EVIDENCE a problem, that, in last months, weeks, days, hours, minutes, seconds and microseconds before engine ignition, was COMPLETELY UNKNOWN and hidden in the dark<br /><br />why the five Shuttles' launches aborted in the last seconds?<br /><br />because the "problem" happen ONLY in the LAST seconds, AFTER engines' ignition!

 

[tap_sa]

<font color="yellow">"because the "problem" happen ONLY in the LAST seconds, AFTER engines' ignition!"</font><br /><br />For fracks sake, how difficult it is to understand that with solids you don't have such 'after ignition before lift-off' period? When you issue the ignition signal in CLV the doggone concoction <b>lifts off immediately</b>. People will shake and bang CLV components well before inaugural flight in order to be positive that it can handle the launch stresses.

 

[dobbins]

If you ever manage to get your head out of your butt long enough to listen to someone else you might learn something.<br /><br />All you do is keep repeating misinformation and outright lies over and over. WHY?<br /><br />Are you doing it to be a pest?<br /><br />Do you think you have some magic ability to alter reality by chanting the same thing over and over?<br /><br />

 

[josh_simonson]

Liquids shut down by turning off the pumps.<br />Solids shut down by un-confining the exhaust and stopping thrust.<br /><br />Both cases the escape tower blasts the crew away.<br />Both cases the rest of the rocket falls to the ground between 0.1 and 1000 miles away. <br /><br />The only difference is flames will still be coming out of the SRB, but the crew should be far enough away to be safe from this.<br /><br />Now if the CLV were held to the launchpad for a couple seconds check before liftoff, they could cancel immediately after launch and just hold it down and let the SRB burn out if something failed on ignition.

 

[najab]

><i>... just hold it down and let the SRB burn out if something failed on ignition...</i><p>Show me the hold-down posts that can withstand 3.3 million pounds of thrust.</p>

 

[gaetanomarano]

<font color="yellow"> People will shake and bang CLV components well before inaugural flight in order to be positive that it can handle the launch stresses.</font><br /><br />true, but with many REAL rockets' launches (like the five aborted Shuttles' flights) may be NOT sufficient<br /><br />"engine's ignition" is like the last (and hardest!) rocket's "super-shock-reliability-test"... if it will fails, liquid engiens will save the rocket<br />

 

[tap_sa]

Are the ones for Saturn V still around? <img src="/images/icons/wink.gif" />

 

[gaetanomarano]

<br />it may be a solution... but the 1st stage SaturnV engines was liquid... then (probably) the "hold-down" system was designed to have the time to stop the engines (closing its pumps)<br /><br />when ignited, the SRB will burn its entire solid-fuel (and liquefying the launch pad)

 

[josh_simonson]

SRBs are held down for testing..

 

[gaetanomarano]

<br />engines' tests are made in a desert place, with special test-pads, the engine horizontal and without an expensive launch pad on its bottom and four astronauts on its top...

 

[drwayne]

I didn't think they did vertical testing of the SRB's, that it was done in horizontal test stands.<br /><br />Keep in mind that you can do things in testing with a test stand (vertical or horizontal) to secure the unit under test that are not really available to you on a launch pad.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[drwayne]

gaetanomarano,<br /><br />You are focusing on one factor, the ability to start and stop a liquid engine, and losing sight of other factors that are just as important.<br /><br />Remember, the capability that your are trumpeting, the ability to shut down a liquid engine if it does not come properly to thrust level, is not really a factor for a solid.<br /><br />My dissertation advisor was fond of saying that he liked digital electronics over analog because they either worked or the didn't. Solids are much like that, if they light, they go. There is little or no chance that they will not come to thrust.<br /><br />There are no moving parts in the combustion process, no complicated plumbing or rapidly spinning pump blades to come apart in a fit in a solid. There are no such wonderful features for solids that liquids, with great names like "hard start" have in their history.<br /><br />There are a lot of factors that go into the reliability analysis of solid versus liquids. Literally hundreds of safety and performace issues that need to be understood in detail. When people who have been working in the industry tell you that there is more to it than "but you can turn it off on the pad" - you don't have to take it as gospel, but at least try to show that you are given a moment of pause before preceeding to what seems like a pre-ordained conclusion.<br /><br />Its funny, this reminds me of an argument my father and I used to have. He used to tell me that cars, if they only have one air bag (and they did back then a lot of the time), should put that air bad on the passenger side, because the statistics showed that was the most dangerous place to ride. For him, that was the end of the discussion. I used to try and tell him - "Dad, I would say the probablity that a car in a wreck has someone in the driver's seat is pretty close to 100%, and it is probably somewhat lower on the other side. Shouldn't a factor in your thinking be having the airbag actually protect someone?" - he w <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>true, but with many REAL rockets' launches (like the five aborted Shuttles' flights) may be NOT sufficient <br /><br />"engine's ignition" is like the last (and hardest!) rocket's "super-shock-reliability-test"... if it will fails, liquid engiens will save the rocket<p><hr /></p></p></blockquote><br />gaetanomarano, once again you are around the subject like a yo-yo. On the previous page you are suggesting CEV booster shut-down might be needed due to some unspecified fault not related to a SRB 1st stage. In the above quote, you are back to supposed problems with the SRB at T-0. Which is it?<br /><br />I would also like you to expand on this idea that a crew might need immediate evac back to the Earth's surface, which appears to be your ratonale for a booster you can switch off. Such a situation has yet to manifest itself through the entire history of the US space program. Even on Apollo 13 they were able to keep a crew alive on a round trip to the Moon, and back to a controlled re-entry on Earth. Given the accumulated knowledge NASA has gained with crew module integrity/pressure suits/operating procedures and redundency related to both, your scenario does seem rather 'fanciful' at best. <div class="Discussion_UserSignature"> <p><em><font size="2" color="#ff0000">Who is this superhero?  Henry, the mild-mannered janitor ... could be!</font></em></p><p><em><font size="2">-------------------------------------------------------------------------------------------</font></em></p><p><font size="5">Bring Back The Black!</font></p> </div>

 

[gaetanomarano]

<br />probably... you (as moderator) don't have the time to read all posts, not even my post and not even may last ten posts... but, if you read them, you discover my opinion is that CLV may need a launch-abort NOT for 1st stage engine problems (that, I repeat again and again and again, may be PERFECT) but other problem that come from hundreds parts of the entire (and completely new) CEV/SM/CLV system<br /><br />the Shuttles' liquid engines' STOP saved five crews (up to 40 astronauts alive!) and five Shuttles (since they was only 3 or 4 in the same time... up to $20 billion saved) ... but this don't appear sufficient to you (and great part of uplink's users) to agree with me about this point!<br /><br />to uplink's users: please don't say me again and again that I suggest a liquid engine for a possible 1st stage failure... it's not true... I suggest it for ANY possible launch failure that need a launch-abort after engine ingnition!<br />