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

[darkenfast]

This has come up before. The problem seems to be with the word "expode", which is a bit imprecise. A rupturing SRB would sure look like a big explosion, but there is a difference between what happens there (or in a ruptured External Tank) and in what happens when a chunk of plastic explosive goes off. The difference is in the speed of the chemical reaction. The launch escape system will be designed to get the (fairly rugged) CEV free and clear. Yes, if the SRB exploded on or just above the pad, it would be an expensive clean-up, but the SRB has such high thrust that the vehicle is on a trajectory clear of the launch complex fairly quickly. The idea posted above, of using the second stage stage for aborts, simply won't work with a liquid fuel engine. The engine would take too long to start and would not provide the acceleration to get the CEV clear, (the specs for the LES call for 10-g's). However, the Russians have talked about using the escape rockets (solids) on the proposed Kliper as a final stage, so it can be done in theory. As I've mentioned before, there is a report available on the 'net: "Reliability and Crew Safety", prepared by SAIC for ATK. This addresses the SRB/J2S version of the CLV, but I don't think the numbers will change a lot for the upper stage with the SSME. Although the report was paid for by ATK, it still gives an interesting look at how the engineers are analyzing the chances of a failure of the "stick". I'm sure some members of this forum won't bother to look at it. They'd rather post ridiculous accusations instead.

 

[drwayne]

"the aborted Shuttle launch is ONLY an example to start a discussion about liquid/solid 1st stage CLV engine"<br /><br />The problem is that if you do not understand the circumstances of an event beyond the top level, then you can draw the wrong conclusions from it.<br /><br />Wayne<br /><br /> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[gaetanomarano]

<br />as I've explained in my posts, SRB may be perfect... but the "abort-order" may come from a malfunction of one of thousands parts and sensors of the entire (completely new and never launched before) 1st stage/2nd stage/SM/CEV/LAS/astronauts "system"<br /><br />if the SRB is perfect but the launch NEED to abort at lift-off, a liquid engine CAN stop while an SRB can't<br /><br />at every launch, the astronauts hearts "runs" at up to 160 beats/minute<br /><br />just imagine that, due to launch stress, one astronaut's body telemetry will signals an high heart's stress that may be too dangerous for his life... this is only an example to explain that a "lift-off problem" that need a launch-abort may come from many hardware and human sources<br />

 

[gaetanomarano]

<br />true.. the second stage need time to burn... too much time to use it to save the crew... the BETTER way to save the crew is to STOP the engines BEFORE the lift-off or use the LAS when the 1st stage (or the 2nd stage) is already burning and the rocket is miles away from earth<br />

 

[tap_sa]

<font color="yellow">"the main problem is: CLV must have an engine that CAN stop at lift-off or an engine that CAN'T? "</font><br /><br />No, the main problem is you failing to realize that while liquid engines have ability to stop during relatively long (seconds) start-up sequence solid <i>motors</i> don't need such feature because their start-up sequence happens instantly and doesn't involve complex sequencing. The possibly outcomes of solid motor ignition are a) grain lights up and off we go or b) grain doesn't light up and we go nowhere. There's no in between like the grain lights up but produces only half the thrust etc. unless there's been some royal f-up at the factory replacing half of the rubber with sawdust or something.

 

[gaetanomarano]

<br />with these critics to me you can (try to) "cancel" me but CAN'T cancel the (TRUE) problems I post<br />

 

[tap_sa]

<font color="yellow">"if the SRB is perfect but the launch NEED to abort at lift-off, a liquid engine CAN stop while an SRB can't "</font><br /><br />SRB doesn't need to stop 'at lift-off' aka T-0 because that's when SRB ignites, <i>capisci</i>?

 

[gaetanomarano]

<br />you don't realize that a problem at lift-off may come from hundreds different CEV/CLV system sources... the 1st stage (liquid or solid) rocket may work PERFECTLY but a solid-engine CAN'T stop, if necessary... consider that CEV/CLV will be a 99% NEW "system", so, the probability that some unknown and unexpected "problems" will happen is very very high (expecially with early flights)<br />

 

[gaetanomarano]

<br />read my last post<br />

 

[kdavis007]

blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah blah.....

 

[najab]

<font color="orange">read my last post </font><br /><br />(If only it was...)

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>but a solid-engine CAN'T stop, if necessary<p><hr /></p></p></blockquote><br />The operative word being <b>IF</b>. Unfortunately for you, gaetanomarano, neither the facts nor operational history of the SRB support <b>ANY</b> kind of necessity to stop a SRB boosting. The critical design flaw identified by the tragic loss of Challenger <b>WAS</b> corrected, and the SRB's have since performed flawlessly.<br /><br />While I agree with the premise that solids are <i>theoretically</i> more dangerous than liquids, <b>operationally</b> the risk has been shown to be zero. Given the choice, I would take the 'simplicity' of a solid-powered vehicle over the 'complexity' of a liquid-powered one in a heartbeat.<br /><br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>consider that CEV/CLV will be a 99% NEW "system", so, the probability that some unknown and unexpected "problems" will happen is very very high (expecially with early flights)<p><hr /></p></p></blockquote><br />Two things. First, as I understand the development process, the early flights will be unmanned as the integrated vehicle/booster package is shook-down. Second, can you describe a scenario by which something at the payload end of the vehicle would cause a catastrophic failure of the SRB (which I presume you are identifying as the 1% of 'old and proven' part of the vehicle design)? <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>

 

[najab]

<blockquote><font class="small">In reply to:</font><hr /><p>you don't realize that a....<p><hr /></p></p></blockquote>And what you seem incapable of seeing is that even with a liquid engine there comes a point at which you are committed to launch - with solids it comes when you send the ingition command, with liquids it comes when you fire the hold-down bolts. Shut the engines down after the bolts are gone and the vehicle just falls over sideways.<br /><br />It's called "launch commit" for a reason.

 

[gaetanomarano]

<br />about your first reply...<br /><br />the problem that need a flight-abort don't need to come only from 1st stage engine... it may be PERFECT but may NEED to stop for many, different and unexpected problems<br /><br />about your second reply...<br /><br />I've read in some articles and graphical timelines that CLV will have only ONE unmanned flight with "full hardware" (and some tests with "dummy" 2nd stage and CEV)<br /><br />this is probably due to the very high cost of each (manned or unmanned) CEV/CLV flight... but, also after TEN flights, the CEV/CLV due can't be "tested" like Shuttle, Soyuz and ready available rockets<br /><br />we can know the CLV realiability now... it may be 99% or 50%... engineers can only TRY to INCREASE its reliability with a good and redundant design<br />

 

[gaetanomarano]

<br />in last 50 years 100% of manned spaceflight was (successfull) made with (reliable) full-liquid or most-liquid engines' systems... now many want to launch a completely new vehicle (that may have dozens of unexpected problems who need the launch to stop!) and up to SIX astronauts with a big mortar's projectile under their bottoms... and they call it "a rational choice"...<br />

 

[frodo1008]

You seem to assume that there will be no prior testing of the components of the single stick CEV launch system. This is totaly incorrect! The individual components will be tested, and tested, and tested. In fact this is quite probably the main reason why any new system is very expensive at first, and needs many production flights to help spread this early costs over the entire length of the program.<br /><br />When the first launch of the shuttle was made back in 1982 the individual components of the system had been tested so very much that the first flight was actually made with John Young and Bob Crippen on the complete shuttle system even though it had never been tested together as a complete system before!! <br /><br />Even though the individual components of this single stick SRB CEV will have also been tested many times, and the propulsion components are already known to be very safe, it has been proposed that the entire system be first tested as a complete system without any risk to astronauts at all! I can't imagine a safer way to go to the eventual first flight with astronauts on board!! Your fears here have been far more than adequatly addressed by NASA! So would you quit wasting time and cyberspace resourses in something that has already been addressed!! After awaile you DO sound like a broken record going blah, blah, blah!!!

 

[najab]

Liquid or solid - once you are committed to the launch you are committed.

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>the problem that need a flight-abort don't need to come only from 1st stage engine... it may be PERFECT but may NEED to stop for many, different and unexpected problems<p><hr /></p></p></blockquote><br />Hmmm, I thought that was the original premise of this thread, but perhaps I have misunderstood. Nonetheless, your concern does not appear to be borne out by history. Once a launch reaches T-0, the evidence would tend to suggest that a vehicle is likely healthy enough for lift-off and the crew has a high probability of survival. Certainly survivability to orbit and the ability to plan a controlled return to Earth. Your concerns would therefore appear to be unfounded.<br /><br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>engineers can only TRY to INCREASE its reliability with a good and redundant design <p><hr /></p></p></blockquote><br />As most would appear to believe has been done with the 'stick/CEV' design. <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 />the full Shuttle was tested only WITH astronauts aboard for two reasons:<br /><br />- it was a very expensive vehicle to launch alone only "to try it"<br /><br />- its design lacks of a "auto-pilot" or "remote-control" flight mode<br /><br />I remember the first shuttle flight... and the difference of heart-beats between the (expert) Young and the (rookie) Crippen (the latter was much higher than first...)<br /><br />I think that the safest manned rocket is with full liquid engines and multiple engines per stage<br /><br />PRACTICE (SaturnV, Soyuz launcher and hundreds rockets) CLEARLY demonstrate that it's SAFE and RELIABLE<br /><br />only in next 20 years, after 20-30 CLV's launches, with "living experimental units" (astronauts...) on the top, we will know if the CLV's "mortar's projectile design" is really safer... CLV is an "experiment"... we only need to wait for experiment's results...<br />

 

[mattblack]

Yeah, what spacekiwi said!! <div class="Discussion_UserSignature"> <p> </p><p>One Percent of Federal Funding For Space: America <strong><em><u>CAN</u></em></strong> Afford it!!  LEO is a <strong><em>Prison</em></strong> -- It's time for a <em><strong>JAILBREAK</strong></em>!!</p> </div>

 

[gaetanomarano]

<br />don't forget that one of the MAIN (claimed) purpose of SRB/SSME choice was not its "better safety" but only the "reuse of ready available Shuttles' derived technologies and parts" (read: "technological refurbishment"...)<br />

 

[dobbins]

"Liquid or solid - once you are committed to the launch you are committed."<br /><br />The vast majority of launch pad explosions that have happened are a result of a shutdown shortly after you are committed to launch, the vehicle rises a few feet then falls back down on the pad rupturing the fuel tanks. This won't happen with a solid, once you fire it it will not shut down by the pad.<br /><br />Either a liquid or a solid fuel rocket can suffer loss of control after lift off. This is where liquids have an advantage because the launch abort system can shut down the liquid fuel rocket while has the extra task of dealing with an out of control booster that is still firing when it takes the CEV away from the stack.<br /><br />This means an advantage for solids during the first few seconds and an advantage for liquids after that.<br /><br />

 

[SpaceKiwi]

<blockquote><font class="small">In reply to:</font><hr /><p>don't forget that one of the MAIN (claimed) purpose of SRB/SSME choice was not its "better safety" but only the "reuse of ready available Shuttles' derived technologies and parts" (read: "technological refurbishment"...)<p><hr /></p></p></blockquote><br />gaetanomarano, you and I both know you are taking a far too literal and narrow translation of Griffin's rationale for incorporating the STS SRB into the CEV program. While I don't have the exact quotes to hand, the <b>essence</b> of what he said is let's not reinvent the wheel if we don't have to.<br /><br />It would matter not that NASA had 'Shuttle-derived-technologies' to hand in the form of the SRB, <b>if</b> the SRB had a 50% failure rate. The fact remains that the SRB's have a 100% operational record in their current iteration. It is <b>that</b> factor which likely swayed the design process most heavily towards their use, not reuse of existing technologies or protection of jobs, etc.<br /><br />Moreover, the way this SRB 'wheel' is going to be utilised in the new vehicle is, to carry on the poor analogy, the equivalent of providing the 'wheel' with ABS braking and traction control. The CEV crew will be many orders of magnitude safer in this vehicle, all the while being boosted by a SRB motor that has not yet failed.<br /> <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>

 

[mlorrey]

Gaetano,<br />If the test program is anything like the capsule test program with the Little John booster in the early 60's, there is little to worry about. Even if there is a problem with the upper stage after the SRB lights off, it is most likely not something that would be a risk until the second stage engines were started. All they'd have to do is wait until the SRB burned out, then activate the escape system, separate the capsule, and they'd be fine.

 

[gaetanomarano]

<br />sorry, but... modify the SRB, modify the SSME, build a new 2nd stage, test the new 1st stage, test the new 2nd stage, test both stages together, test both stages with dummy CEV, man-rate the rocket, etc. etc. etc. really ******** IS ******** like "reinvent the wheel"!!!!<br /><br />all this time and money lost only to launch an heavy six-seats CEV that (in 99% of flights) will be used with 3 or 4 astronauts!!!!<br /><br />ONLY if NASA will build a four-seats 12 tons CEV and launch it with a (man-rated) ready available (low cost and realiable) mid-rocket, they will NOT "reinvent the wheel"!!!<br />