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  #11  
Old 12-19-2013, 01:17 AM
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Quote:
Originally Posted by Chas Russell
I believe that the ejection seats were for a low-level, low-speed abort. At a certain part of the envelope they would use the four retro rockets as abort motors to initiate a safe abort.


I'll bet THAT idea must have brought hoots from the astronaut corps.

The Gemini-Titan packed some serious acceleration (8+Gs)

No way in flaming hell the retrorockets would generate enough thrust to push the capsule free of the launch vehicle before it was overtaken by the expanding conflagaration of a presumably breaking-up booster.

So essentially that meeting must have ended with the astronauts being told, "if anything goes wrong during this phase of the mission, you guys are dead, but we will tell the public a nice happy-sounding story to make them think we have made some minmal provision for you not to get killed."

Essentially the same thing the astronauts were told when the final design of the shuttle was decided upon.
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  #12  
Old 12-19-2013, 07:29 AM
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"The escape tower used for Mercury was deleted; the propellants used in the Titan II launch vehicle, while toxic, corrosive, poisonous, and self-igniting, did not explode in the manner of the Atlas or Saturn LOX/Kerosene combination."
Encyclopedia Astronuatica

Gemini's retro pack consisted of four solid rockets, fired one at a time for de-orbit. Each had 4.45 Kn (about 1,000 lb) of thrust, for a total of 4,000 lbs thrust. The Capsule itself weighed around 8,000 lb. So the retro bottles were not going to move the capsule very far.

John Young said in an interview that there was no way he would have ejected from Columbia during ascent. He used the term "crispy critter".
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  #13  
Old 12-19-2013, 05:23 PM
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Quote:
Originally Posted by Ironnerd
"The escape tower used for Mercury was deleted; the propellants used in the Titan II launch vehicle, while toxic, corrosive, poisonous, and self-igniting, did not explode in the manner of the Atlas or Saturn LOX/Kerosene combination."
Encyclopedia Astronuatica

Gemini's retro pack consisted of four solid rockets, fired one at a time for de-orbit. Each had 4.45 Kn (about 1,000 lb) of thrust, for a total of 4,000 lbs thrust. The Capsule itself weighed around 8,000 lb. So the retro bottles were not going to move the capsule very far.

John Young said in an interview that there was no way he would have ejected from Columbia during ascent. He used the term "crispy critter".


I do remember reading a story (which might have contained these quotes from Young) which essentially said the ejection seats on the first shuttle flights would only have been useful for a couple of VERY brief moments in any abort scenario -- mainly in the final minutes of a RTLS abort before a reasonalbly stably-gliding but non-landable shuttle (due to landing gear problems or inability to reach a landing strip) would have to ditch in the ocean.
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  #14  
Old 12-19-2013, 08:48 PM
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Quote:
Originally Posted by JStarStar
I'll bet THAT idea must have brought hoots from the astronaut corps.

The Gemini-Titan packed some serious acceleration (8+Gs)

No way in flaming hell the retrorockets would generate enough thrust to push the capsule free of the launch vehicle before it was overtaken by the expanding conflagaration of a presumably breaking-up booster.

So essentially that meeting must have ended with the astronauts being told, "if anything goes wrong during this phase of the mission, you guys are dead, but we will tell the public a nice happy-sounding story to make them think we have made some minmal provision for you not to get killed."

Essentially the same thing the astronauts were told when the final design of the shuttle was decided upon.


Yes, Titan II had some serious G loadings on the astronauts, but remember, it was a LIQUID vehicle and could be shut down, unlike the SRB equipped shuttle-- once those big SRB's are lit, they're burning until 1) they burn out or 2) they're blown up. That's it.

Also, as mentioned, the Titan II was powered by room storable hypergolic propellants... they don't "explode" as such, they burst into flame when mixed together...

Once you're into the flight far enough that the second stage burn is underway, the abort requirements as far as thrust is concerned lighten up. Remember on the Saturn V they were sitting on top of the still fully fueled third stage as well as nearly a million pounds of propellant in the second stage, plus the hypergols in their own SM and the LM... yet the tower was jettisoned shortly after the second stage startup. Yes, the G-forces on a Saturn V launch were less, BUT, again, it's a liquid rocket-- if the stage is failing, it's shut down and the abort would take place... you don't have to "outrun" it-- just get away from it. With it's engine shut down, it's not accelerating-- and the retrorockets on the Gemini or SPS engine on Apollo was sufficient to provide the push needed to get away from the failed rocket.

Solids, on the other hand, create all sorts of problems-- since they cannot be shut down, they will continue to "chase down" the capsule after an abort, unless the casing is blown by a linear shaped charge or thrust termination ports at the same time as the abort takes place, which is highly dangerous. In fact, it's worse than that, because if you have to abort off a firing SRB/SRM, it's actually going to accelerate FASTER than normal because suddenly it's relieved of the additional mass of the spacecraft, tower, and probably the upper stage or core stage. If you blow it up with range safety charges, either a linear shaped charge like the shuttle SRB's, you've suddenly created a mile-wide fireball filled with burning chunks of APCP chasing the capsule on a ballistic trajectory, before slowing and falling back to Earth. That's why the Orion escape system is SO MASSIVE and powerful, and inflicts such loads oLaten the crew-- and still is dicey to get the capsule far enough away for the parachutes to not melt as the capsule drifts back down into the burning chunks of APCP filling the sky after the SRMs are unzipped by the LSC...

You're exactly right about the shuttle, and that's why basically the whole time the SRB's were firing, they had NO realistic options for aborting-- it was hope it holds or die. The SRB's couldn't be shut down, and they couldn't be jettisoned while burning (the thrust connection is sorta like a gigantic version of a truck and trailer ball hitch-- the "ball" is on the SRB and constantly pushing up into the socket on the SRB thrust beam on the ET... only when the thrust tails off does the SRB 'drop back' and the separation sequence allows the ball to slide back out of the socket and the SRB to be pushed away by its jettison motors). The RTLS abort depended entirely on the SRB's being gone, and then the SSME's were shut down, and the ET jettisoned-- then the orbiter had to fire its OMS engines to maneuver away, set up for a sort of "belly flop reentry" (depending on the height, speed, and location; if it was early enough in flight it had to basically flip over and roll out and start gliding back for the landing site). Basically I read early shuttle astronauts describe the "abort procedures" for the shuttle as "a series of miracles followed by an act of God"...

Not very probable IMHO... or theirs evidently...
Later! OL JR
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  #15  
Old 12-20-2013, 07:32 AM
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I don't think "Dragon" will have a tower either. If their system goes to plan, the Dragon will have eight 120,000 lb thrust side-mounted liquid-fueled engines for abort. As an added bonus they can be used for powered descent in the event of a parachute failure, or as the primary means of deceleration with the parachutes available in the event of an engine failure.

ARTICLE

The article is a little odd in that it shows Dragon performing a powered landing on Mars. But it does not show any way to get back off of the planet. Maybe it's just the supply ship...
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  #16  
Old 12-20-2013, 11:25 AM
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Quote:
Originally Posted by Ironnerd
I don't think "Dragon" will have a tower either. If their system goes to plan, the Dragon will have eight 120,000 lb thrust side-mounted liquid-fueled engines for abort. As an added bonus they can be used for powered descent in the event of a parachute failure, or as the primary means of deceleration with the parachutes available in the event of an engine failure.

ARTICLE

The article is a little odd in that it shows Dragon performing a powered landing on Mars. But it does not show any way to get back off of the planet. Maybe it's just the supply ship...


That's Red Dragon landing on Mars...

I haven't followed all that very closely, because it's really a lot of "gee whiz" type stuff at this point-- sorta like flying car concepts and ideas in the 50's...

Not sure it's even supposed to be manned-- just filled with instruments. IF they DO have a manned version, pretty sure they planned a separate ascent vehicle for leaving Mars...

Later! OL JR

PS. Correct, Dragon won't have a tower. Orion nearly didn't... back when Mike Griffin's people were desperately trying to shave every ounce off Orion to make up for Ares I's lousy performance, they looked at a pusher type escape system... even did a test flight of it... it's called "MLAS"... Quest even came out with a model of it...
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  #17  
Old 12-20-2013, 12:02 PM
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FYI, The Space Shuttle crew module was designed by the same folks who worked on the B1 and therfore it was originally going to be ejectable as a complete module. Weight became an issue, so they scrapped that idea. The extra weight would have included the retrorockets and huge parachutes for the module plus the guillotines to sever the wiring and tubing.
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Old 12-20-2013, 02:12 PM
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Quote:
Originally Posted by Shreadvector
FYI, The Space Shuttle crew module was designed by the same folks who worked on the B1 and therfore it was originally going to be ejectable as a complete module. Weight became an issue, so they scrapped that idea. The extra weight would have included the retrorockets and huge parachutes for the module plus the guillotines to sever the wiring and tubing.


Yeah, I always thought that would have been a good idea... sorta like the crew module on the FB-111 Aardvark... but the weight simply precluded the idea from happening.

We have good evidence that if it had, even a catastrophic failure like Challenger would likely have been survivable-- they know that at least part of the crew was probably conscious and likely all were alive when they hit the water...

Wouldn't have done much for Columbia though... a tumbling crew module after an orbiter breakup on reentry would burn up without a heat shield and stable entry...

Later! OL JR

PS... sounds like the same kind of engineering that argued that Titanic would be it's own lifeboat thanks to the watertight compartment bulkheads... and we all know how that turned out...
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  #19  
Old 12-20-2013, 02:46 PM
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Quote:
Originally Posted by luke strawwalker
PS... sounds like the same kind of engineering that argued that Titanic would be it's own lifeboat thanks to the watertight compartment bulkheads... and we all know how that turned out...
The 1997 movie was on this past Sunday. I'd never seen it before, but I'd been meaning to rent it

Anyway, after it was over, it occurred to me the fallacy of the builders' thinking. It's a bit easier to buy into the notion that 100% lifeboat coverage wasn't needed, but thinking that topless compartments were somehow adequate is pure stupidity. I call it "drinking the koolaid", or taking verbal drugs (believing the unbelievable).

When water started coming over the walls of flooded compartments into adjacent compartments, I'm sure it occurred to the folks in those spaces just how foolish a notion it was that open-top compartments were somehow a reasonable compromise

I've seen this before, where folks talk themselves into accepting a partial solution, only to realize later that half-@$$ed solutions usually amount to no solution at all. The Maginot line comes to mind...


Doug

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  #20  
Old 12-20-2013, 04:23 PM
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Quote:
Originally Posted by Doug Sams
:

I've seen this before, where folks talk themselves into accepting a partial solution, only to realize later that half-@$$ed solutions usually amount to no solution at all. The Maginot line comes to mind...


Doug

.



Sorta like SLS... which looks good on paper, but when you look at the price tag and what's being given up to pay for it... and what they're gonna be able to do with it... (or not do as the case may be... won't be doing much without modules, in-space propulsion stages, etc.)

Talk about your champagne tastes on a beer budget... and that never works long term...

Later! OL JR

Maginot Line is an interesting case... classic case of planning to fight thinking the next war will be fought like the last one, while the enemy learned the lessons of the last war and intends to fight it completely differently.

Maginot Line would have worked GREAT... in 1914... but in 1940, it was a completely different story... The French completely ignored the lessons learned in WWI, about the futility of trench warfare and the essential nature of movement and breakthrough to victory. After four years of stalemate, the war came to an end in a matter of months due to the employment of tanks to create breakthroughs in combination with the German Army not being backed up because Germany's economy was collapsing and demoralization of the populace. The Germans, who'd been on the receiving end of those early tank attacks, learned the capabilities of armored thrusts to break the lines of resistance and turn the tide of battle, and employed that as a cornerstone in their tactical thinking about how to fight the next war (Blitzkrieg) as spelled out by Heinz Guderian and others...

Whats interesting in hindsight is that NATO took much the same foolish stance for the defense of Western Europe during the Cold War. They assumed that the Soviets intended a massive armored invasion in a conventional war against the West if it came to war, since the Russians had all those dozens and dozens of tank divisions standing by in the Warsaw Pact. Thus, NATO intended to 'turn back the Red hordes' and destroy the massive conventional armored thrusts of Soviet tanks by the use of tactical nuclear weapons, neutron and enhanced radiation bombs, and such (which incidentally would have devastated Western Europe anyway, using them on their own soil). The Soviets were well aware of this, and their plans were completely different. If it came to war, the Soviets intended a full out nuclear first strike against NATO bases and assets in Western Europe as a PRELUDE to any other action-- IOW, nuke "everything" and then send the tanks in to secure what's left...

Later!
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