Ares I safety conundrum and alternate launchers

T.Neo

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As we all know, Ares I was sold on its supposed safety performance, which was said to be better than the EELVs studied in ESAS.

But I got thinking: Orion was of the size range that only the EELV heavies could lift it. The heavies had more engines, and more seperation events. A smaller vehicle could be lifted on something like the Atlas 401 or Delta IV Medium, which would be simpler vehicles.

But in keeping with that sort of payload mass...

Imagine taking the second stage of Ares I, with its J-2 engine. Instead of mounting it atop an SRB, mount it atop a kerolox liquid core stage, powered by an engine such as the F-1A. The core stage could either share 5 m Delta tooling, or tooling with the upper stage.

This vehicle could be substantially safer than the EELV heavies, but could be more flexible, have advantageous features, and not be so... nice to Utah.

Now imagine, as a "CaLV" to this "CLV", a THREE CORE HEAVY variant of this single-core launcher, perhaps with crossfeed, as well as an 8.4 meter EDS.

Just as a fun brain-doodle, what advantages and disadvantages would such a system have had?

Also, which is the safer way to design a launch vehicle? With the fewest propulsion elements (a la Liberty) for the lowest chance of catastrophic failure, or with redundant propulsion elements (like Falcon 9) to enable continued flight after non-catastrophic failure?

Would engine-out capability lower LOM rates, but make LOC rates higher, if the LES was relatively reliable?
 

Wishbone

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Need numbers on performance margins and probabilities, cost of engines, and a helluva lot of experiments/numerical simulations. Engine explosions come in a wide variety of grades, with shrapnel/debris flying in different directions, and definitely not following the usual "bomb-derived" distributions.

How critical is the mission? Can you recover the crew and quickly launch another rocket (of a different type, perhaps)?
 

T.Neo

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Need numbers on performance margins and probabilities, cost of engines, and a helluva lot of experiments/numerical simulations. Engine explosions come in a wide variety of grades, with shrapnel/debris flying in different directions, and definitely not following the usual "bomb-derived" distributions.

Indeed... there would need to be at least a lot of categorisation of information such as failure rates, etc, to quantify this sort of thing.

How critical is the mission? Can you recover the crew and quickly launch another rocket (of a different type, perhaps)?

Well, the thing is carrying people... obviously it is bad if it fails in a way that would kill them... :shifty:
 

cymrych

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Correct me if I'm wrong, but doesn't NASA require engine-out capability when man-rating a launcher to preserve an ATO option?

On 2nd thought: I suppose the answer must be "No", otherwise Ares-1 wouldn't have been mounted on a single SRB 1st stage.
 
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RisingFury

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Is there an O-F filter capable of excluding EELV, Space shuttle and Constellation / SLS threads?

The endless ranting, "THIS LAUNCH VEHICLE SUCKS" and constant "I KNOW BETTER THAN EVERY ENGINEER" suggestions are really getting old and the same old smelly pile gets peddled around in every thread...
 

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To T.Neo - by "critical" I mean time-critical - e.g. is it part of a mission to Mars that has to fit into a small window, or is it just crew rotation in LEO? If you desperately want to get to LEO today, engine-out capability is preferred. If you can wait for another launch campaign, or there's a stand-by rocket (of a different type), simplicity wins.

To Rising Fury - in this thread T.Neo has not (yet) attempted to ignite anything, so your criticism while possibly prescient is currently unfounded. Launcher discussions are perfectly legit here, or so I've heard...
 

T.Neo

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Is there an O-F filter capable of excluding EELV, Space shuttle and Constellation / SLS threads?

The endless ranting, "THIS LAUNCH VEHICLE SUCKS" and constant "I KNOW BETTER THAN EVERY ENGINEER" suggestions are really getting old and the same old smelly pile gets peddled around in every thread...

:beathead:

Where is the "I like certain concepts a lot and intensely dislike people questioning them in any way" filter? :dry:

Also, this is no "HUR I KNOW BETTER" assertion, but rather a question: would a single core launcher of this type be considerably safer than the EELV heavies and thus an alternative (safety-wise) to the Ares I, a launch vehicle that ended up having a more complex development than originally intended and garnered considerable criticism from qualified people- including those from within NASA itself.

To T.Neo - by "critical" I mean time-critical - e.g. is it part of a mission to Mars that has to fit into a small window, or is it just crew rotation in LEO? If you desperately want to get to LEO today, engine-out capability is preferred. If you can wait for another launch campaign, or there's a stand-by rocket (of a different type), simplicity wins.

Ok, fair point. But would a potentially higher LOC number (from more engines) be acceptable if the risk of LOM were too high?

A delayed Mars mission could potentially be billions down the drain. And maintaining a technologically distinct launcher system for redundancy would also cost more...
 
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Wishbone

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Ok, fair point. But would a potentially higher LOC number (from more engines) be acceptable if the risk of LOM were too high?

A delayed Mars mission could potentially be billions down the drain. And maintaining a technologically distinct launcher system for redundancy would also cost more...

LOC numbers are stipulated by man-rating documents as a constraint. Either you meet the standard or not. This said, reckon that it is possible to add ceramic armor or kevlar mesh to reduce the potential for fatal debris strikes.
 

RisingFury

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You could at least stick to one of the existing mega threads. It's becoming increasingly difficult to avoid the dark cloud of cynicism that surrounds threads like these. :facepalm:
 

Wishbone

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It takes a stoic to tolerate the cynics. Try to be an epicurean...
 

T.Neo

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You could at least stick to one of the existing mega threads.

I don't see any "Ares technical issues" mega threads. There are threads about Ares, but they're years old and still don't quite fit the topic here, which is: could an alternative to Ares I (liquid propellant on both stages) still have a very low LOC rate?

LOC numbers are stipulated by man-rating documents as a constraint. Either you meet the standard or not.

What is the standard, then?

This said, reckon that it is possible to add ceramic armor or kevlar mesh to reduce the potential for fatal debris strikes.

Only if you have excess lift capability... I believe DIRECT proposed to use the huge excess lift capacity of their J-130 to fit armor plate between Orion and the rest of the vehicle...

Still, maybe something similar could be possible with a little bit more lift capacity (for a 35 ton capable vehicle, for example).
 
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n122vu

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It's becoming increasingly difficult to avoid the dark cloud of cynicism that surrounds threads like these.

For what it's worth, I'm not seeing any of that here. I am enjoying reading a completely technical discussion about a proposed current-tech launch vehicle concept. I have seen no criticism, negative bias, or cynicism thus far.

To me it seems the OP has a specific idea/question, and doesn't want it to get lost in the 'same old smelly pile.'
 

Wishbone

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Page 12 of 39
CCTS Certification Requirements
Document No: ESMD-CCTSCR-12.10
Revision: Basic
Effective Date: December 8, 2010

5.2.2 The CCTS shall safely execute the Loss of Crew (LOC) requirements
specific to the NASA Design Reference Mission (DRM). The Programs shall
determine and document the LOC risk when DRMs are specified. The
following are current:
a. The LOC probability distribution for the ascent phase of a 210 day ISS mission shall have a
mean value no greater than 1 in 1000
b. The LOC probability distribution for the entry phase of a 210 day ISS mission shall have a
mean value no greater than 1 in 1000
c. The LOC probability distribution for a 210 day ISS mission shall have a mean value no greater
than 1 in 270

Source: http://www.nasa.gov/pdf/504982main_CCTSCR_Dec-08_Basic_Web.pdf
 

RisingFury

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For what it's worth, I'm not seeing any of that here. I am enjoying reading a completely technical discussion about a proposed current-tech launch vehicle concept.

Oh, just wait a page!

Every SLS, Constellation, Space Shuttle and NASA decision thread has turned ugly.
 

T.Neo

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Oh, just wait a page!

Every SLS, Constellation, Space Shuttle and NASA decision thread has turned ugly.

It seems to me that the only person suggesting this thread will "turn ugly" is you.


Hmm, that is interesting. With the figures in ESAS, Delta IVH would meet those requirements, right? And Atlas VH would only miss them by a small margin...

This document by ULA gives a LOC rate for Atlas V heavy of 1/1000, and 1/800 for Delta IV Heavy (interestingly enough, opposite of ESAS, which gave 1/957 for Atlas V and 1/1 100 for Delta IV- though both were given upper stages).

In the same document, the LOC rate for Atlas 401 is given as 1/2500, higher than all "stick" launchers shown in the ESAS, and a LOC rate for Atlas 402 of 1700/1 (I believe the DEC does not afford engine out capability as the engine gimbals cannot compensate for the torque produced by only a single engine running).
 

agentgonzo

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Oh, just wait a page!

Every SLS, Constellation, Space Shuttle and NASA decision thread has turned ugly.
If you keep on butting in every third post to moan that you don't like the thread then you're going to get on people's tits and of course it's going to turn ugly - except that it'll be because of you rather than any other reason. Go tout your drivel somewhere else and let those folks on this thread continue with their discussion however they like.
 

Urwumpe

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Man-rating is not about engine out, but about how you handle an engine-out. A loss of vehicle can be acceptable, if it is no loss of crew.

Also engine-out capability on a SRM is pretty easily deduced: Once the SRM ignites, it will keep on burning until it is destroyed or runs out of fuel.

That is why you will find SRMs everywhere, where you rely on safety: Ejection Seats, Launch escape systems, even gas generators for your airbags are actually small SRMs.

The chance that a segmented SRM will fail fatally is pretty low, on the scale of manufacturing errors that you can't prevent by any quality assurance. Even a broken segment seal is not the end of the mission, though the thrust force of the leak and the resulting loss of performance of the SRM can be a threat to the success of the mission.


Worse for any SRM are case bursts, which are sudden ruptures of the propellant casing. There are extremely rare and can be prevented by proper ultrasonic/X-Ray testing of the propellant case (even automatic tests are good enough now), but when they happen, they are highly explosive. Not only the pressure inside the case is then causing explosive force, it is also augmented by fuel fracturing while the pressure is still high enough to sustain combustion. The increase of burning surface is stronger than the drop of combustion rate by temporarily increasing pressure.

Important is reacting early enough to a case burst to trigger automatic abort. The length of the second stage is not unimportant there - even if a case burst would destroy the second stage, it buys you time to react.


You should for the assessment of different launchers etc, maybe try it with an extended risk matrix, making a large plot with two dimensions: The X axis should be how dangerous a risk is, with LOC being the highest danger (collateral damage is hard to predict), the Y axis plots the probability. This plot should be divided into 4 or more zones, for example highly probable but harmless risks.
 
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