Author Topic: CEV abort system gains a brain  (Read 16600 times)


Offline David AF

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RE: CEV abort system gains a brain
« Reply #1 on: 12/20/2005 09:40 PM »
How cool is this! This CEV is sounding better by the day. The new computers are going to be amazing by the read of info like this and I don't think anyone would be happy about another new vehicle without an escape.
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Offline Space101

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RE: CEV abort system gains a brain
« Reply #2 on: 12/20/2005 10:07 PM »
Sounds very interesting. Will it override human reaction? Suppose it would have to with the speed of a possible failure, just like Challenger, even if Challenger had no means to eject the crew out of the way.
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Online Chris Bergin

RE: CEV abort system gains a brain
« Reply #3 on: 12/20/2005 10:40 PM »
I think the system has to over-ride humans in an emergancy. It may also be the first alert of the astronauts and controllers.

I'm not sure how this would work. I would hope there would be some warning, as in such a situation, they are going to be fired out and away of the booster at X amount of G. I'd want to know about it!

I want to interview the people involved, so there's more to come I'm sure. I'll ask if they are open to it and see about setting up a  and A on the forum.

Offline STS Tony

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RE: CEV abort system gains a brain
« Reply #4 on: 12/21/2005 12:37 AM »
And if the first stage or second stage blows up, the Escape System can get the module out of the way fast enough? I don't see how it's much use apart from saving the need for a RTLS abort? Someone who knows these things better than me might know better.

Offline To The Stars

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RE: CEV abort system gains a brain
« Reply #5 on: 12/21/2005 12:59 AM »
Fantastic. Not only is the crew escape totally required to be back in NASA man-rated vehicles, I'm so encouraged such an established bastian of computer software intergration technology such as Texas Tech is involved in the programming of the new vehicle. This is superb news and thanks for bringing it to our attention!

Offline Jamie Young

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RE: CEV abort system gains a brain
« Reply #6 on: 12/21/2005 03:50 AM »
Damn, nearly missed this! A new system and even a new programming language, is this what they did with the Shuttles when they were first made?

Offline realtime

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RE: CEV abort system gains a brain
« Reply #7 on: 12/21/2005 05:02 AM »
Neither of the languages mentioned in the article are proven "real-time" languages, which means roughly, that if a program is written to perform task A in time T, and it can only perform the task in time T+n, then the program is broken.  Real-time languages support such tight scheduling deadlines.  They are commonly used to code flight control systems, data acquisition systems, medical systems, etc.

SequenceL is an experimental data-abstraction language which is another way of saying it's designed to "free the problem solver from much of the difficult effort required to produce algorithms that imply the data products they desire" (1).  Oof.  This language has never been used anywhere outside academia to my knowledge.  It supposedly does have a real time variant, but again, I can find no evidence of it having been used in any high-reliability industrial application.

A-Prolog (2) I cannot even find a reference to.  Prolog (plain old variety) has been kicking around for many years but never really caught on in industry.  It's used in some expert systems and database applications and as a batch database correlator for some real-time front-ends.

As far as I can tell, nobody writes in SequenceL except the guy who designed it and his grad students at UTexas.  Lots of people putz around with Prolog, but it's really used to generate masters' theses and hobby projects.

Maybe I'm too old-school, but this doesn't strike me as good news.  It sounds like somebody in NASA saw a "shiny object" and made a decision based on the glitz and glamor of these "natural language" tools.  The system they have presented here is, in my opinion, overblown.  It is based on specious theory and an untried language that, if carried to completion, will have as its first implementation our CEV abort system.

Personally, I would feel lots better if the abort system was a small program running on VxWorks and written in C by a few hard-core real-time programmers, but that's just me.  I like stuff that works.

(1) http://64.233.161.104/search?q=cache:cQP8Rz6oJycJ:www.cs.utep.edu/vladik/2002/tr02-24.doc+sequencel+language&hl=en

(2) http://kti.ms.mff.cuni.cz/~bartak/prolog.old/FAQs.html


Offline Jamie Young

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RE: CEV abort system gains a brain
« Reply #8 on: 12/21/2005 05:07 AM »
You sound like you know what you're talking about. What do you think would be a better choice of software/lanuage, whatever this is? ;) I know nothing about this subject.

Offline Dobbins

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RE: CEV abort system gains a brain
« Reply #9 on: 12/21/2005 05:50 AM »
Quote
Jamie Young - 21/12/2005  1:07 AM

You sound like you know what you're talking about. What do you think would be a better choice of software/lanuage, whatever this is? ;) I know nothing about this subject.

HAL/S, the language that was developed for the Shuttle computers. It's a real time language that has been throughly debugged over the past 30 years.

Most computer programs are written in a high order language that is easy for humans to understand, but these have to be translated into assembly language that the computer can understand by a compiler. If there is a bug in the language, then there will be bugs in the program that is written with it.

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Offline lmike

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RE: CEV abort system gains a brain
« Reply #10 on: 12/21/2005 09:24 AM »
Sounds like they are just prototyping in this new language.  For this sort of hard real-time reqs. I'd go with an FPGA circuit or even a custom build ASIC chip.  Directly wired to the sensors and the manual abort switch and the LES motors/CEV separation bolts.  Needs to be close to the metal.  As simple in logic as possible.  'Primitive', even.  Especially with a solid as the first stage.  Must not have an (computer) override if the crew/ground controllers elect to abort (due to visual clues for example)  But an override to force an abort above certain threshold of malfunction data.

Offline FransonUK

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RE: CEV abort system gains a brain
« Reply #11 on: 12/21/2005 11:17 AM »
So do we think the CEV will ever be in a situation that force an abort without prior warning to the controllers or crew? I obviously like the idea of the commander or controller having the final say, but given the human brain will not react as fast, that could make the human control pointless in an emergancy?

Note Challenger.
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Offline Rocket Ronnie

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RE: CEV abort system gains a brain
« Reply #12 on: 12/21/2005 11:54 AM »
Never take the control to abort away from the pilot or commander is what I'm thinking. I'd feel a bit wrong if I was flying in something that was in control of saving my life.

Online Chris Bergin

RE: CEV abort system gains a brain
« Reply #13 on: 12/21/2005 11:58 AM »
But what point is that if it's a Challenger situation, where the only member of the crew to notice managed to utter "uh oh" before break up. Even if he had aborted on the uttering those words, it'd of been too late. Yet Challenger was already going through processes to try and correct the problems, before that was made pointless by the SRB twisting into the ET.

I know what you mean as far as control with the Commander, and I agree - but how do you get around the problem of not being able to react as fast as the computer?

Offline Martin FL

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RE: CEV abort system gains a brain
« Reply #14 on: 12/21/2005 12:13 PM »
It's a fine line they have to find. This system is going to be used to at least work out what needs to be done once the Abort is in progress, whether it will decide if to actually Abort is the interesting element.

Offline SimonShuttle

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RE: CEV abort system gains a brain
« Reply #15 on: 12/21/2005 01:07 PM »
How do other abort systems work, like on the older US versions, Apollo etc. And maybe on the Russian ones?

Offline Dobbins

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RE: CEV abort system gains a brain
« Reply #16 on: 12/21/2005 05:12 PM »
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Chris Bergin - 21/12/2005  7:58 AM

But what point is that if it's a Challenger situation, where the only member of the crew to notice managed to utter "uh oh" before break up. Even if he had aborted on the uttering those words, it'd of been too late. Yet Challenger was already going through processes to try and correct the problems, before that was made pointless by the SRB twisting into the ET.

I know what you mean as far as control with the Commander, and I agree - but how do you get around the problem of not being able to react as fast as the computer?

In Apollo the system would do an automatic abort under certain conditions, or the comander could do a manual abort.

http://en.wikipedia.org/wiki/Apollo_spacecraft#Launch_Escape_System_.28LES.29

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Offline lmike

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RE: CEV abort system gains a brain
« Reply #17 on: 12/22/2005 12:14 AM »
Of course, the system should be able to do an auto abort, the whole point of the electronics on the LES is the fast reaction time, especially with solids there are less things to monitor for clues.  Or, if the crew are incapacitated.  The manual control is there just to force an escape, not to prevent it.  I'd also give this ability to the ground controllers, in case there are some visual clues from outside on launch.  There could be (extremely unlikely) scenarios where the system could do a false abort in the extremely short time that the LES is active at all, 2 minutes of the ascent?, but at the worst the crew would survive, just with a loss of a good vehicle.  

So, the rules in my view: if the electronics and/or the crew decide to abort they abort.  Whoever throws the switch first.  If the system doesn't think it's time to abort, but the crew do, they still abort, the electronics stand aside.  The other way scenario is not likely since the reaction time of the system would be much faster than people flipping the override switch to stop it, but I'd say if the crew disagree, the system still aborts.  

The bigger problem, I think, is how to make a reliable abort decision based on a few sensor readings.  But with some statistics of what can go wrong with a solid first stage most of which has already flown some 200 times, and a couple of sensors here and there it's not that hard really.  Nothing that requires an AI, or a high level language, that's for sure.

Offline lmike

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RE: CEV abort system gains a brain
« Reply #18 on: 12/22/2005 02:30 AM »
Another thing that I'm curious about is that with the solid first stage, some failure modes (e.g. bad assymetrical grain) the LES motors would have to have much more thrust, or the separation of the CEV done a little sideways, because (in some of the modes) the abort system couldn't attempt to throttle down the first stage or just shut off the propellant lines as it could with the liquid first stage, and with a much lighter payload the CLV is going to shoot up like nobody's business and catch up with the CEV/LES stack, although they could blow a hole in the CLV's side with a pyro (hopefully without explosion) to make it lose thrust.

Offline Dobbins

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RE: CEV abort system gains a brain
« Reply #19 on: 12/22/2005 02:36 AM »
The use of a solid booster first stage makes the LES harder to design and program. In the Mercury and Apollo systems the LES could shut down the booster if it was out of control. A solid rocket can't be shut down so the LES has to be capable of reacting to any failure modes that produce side thrust.

The Mercury LES didn't even use a computer, it's sequencer relied on relays and logic circuits. You could get by with something that simple on a liquid fueled rocket, though it was a nightmare to checkout. A LES for a solid will require a fairly complex program.

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Offline Andy L

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RE: CEV abort system gains a brain
« Reply #20 on: 12/22/2005 02:37 AM »
Great posts.

On a different part of the subject, what level of G are the crew expecting to jump to on a crew escape abort? They are already travelling some, then get the kick boost of an abort?

Also, why wasn't any form of a crew escape for ascent designed into the STS? Impossible on that config? Only the two ejector seats possible?

Offline realtime

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RE: CEV abort system gains a brain
« Reply #21 on: 12/22/2005 02:45 AM »
Quote
lmike - 21/12/2005  8:14 PM

Of course, the system should be able to do an auto abort, the whole point of the electronics on the LES is the fast reaction time, especially with solids there are less things to monitor for clues.  Or, if the crew are incapacitated.  The manual control is there just to force an escape, not to prevent it.  I'd also give this ability to the ground controllers, in case there are some visual clues from outside on launch.  There could be (extremely unlikely) scenarios where the system could do a false abort in the extremely short time that the LES is active at all, 2 minutes of the ascent?, but at the worst the crew would survive, just with a loss of a good vehicle.  
Agree wholeheartedly.  Forced abort by either ground or crew.  Auto-abort if the humans don't notice that a failure is imminent.

Quote
...
The bigger problem, I think, is how to make a reliable abort decision based on a few sensor readings.  But with some statistics of what can go wrong with a solid first stage most of which has already flown some 200 times, and a couple of sensors here and there it's not that hard really.  Nothing that requires an AI, or a high level language, that's for sure.
The rules for deciding to abort have to be encoded somehow.  FPGAs are programmed using a higher level language like Verilog or VHDL and then translated into gate logic.  Amazing stuff, but they're just as subject to errors in design as any other language.  However, there's a lot of industry experience in those types of devices.  Not so much in SequenceL.

An FPGA link for the geeks:

http://www.embedded.com/showArticle.jhtml?articleID=18201956


Offline realtime

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RE: CEV abort system gains a brain
« Reply #22 on: 12/22/2005 03:12 AM »
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Jamie Young - 21/12/2005  1:07 AM

You sound like you know what you're talking about. What do you think would be a better choice of software/lanuage, whatever this is? ;) I know nothing about this subject.
I've worked with experimental languages and have spent a goodly part of my career doing real-time and industrial applications programming (thus the nick).  I brought up the subject of declarative languages such as Prolog and SequenceL with some of my colleagues today.  They're in two camps.  

One is the camp that I spoke to earlier, which holds that it should be done in a more procedural fashion using well-proven languages like 'C' compiled with a thoroughly debugged mature compiler, and running on a workhorse real-time OS like VxWorks.  Since that is the kind of work I do, I favor that approach.  "To a man with a hammer, every problem looks like a nail."

The other camp holds that my beloved procedural approach is more susceptible to programming errors, since every hand-crafted line of the program could contain a bug.  They, like NASA, favor the "declarative" approach where a lot of related parameters can be controlled at once by altering a single high-level parameter.  

If you've written the compiler right, this eliminates the possibility of one of those sub-parameters being mishandled, since the compiler generates all the code to make it happen.  Theoretically, all the engineer (not programmer) has to do is correctly define the logical relationships between say, control outputs like explosive bolt triggers and escape rocket igniters and define them as sub-parameters that share a single high level control command (that command being: ABORT!).

This is the primary advantage to solving control problems using declarative languages.  The difficulty in the past has been in producing bug-free compilers that generate efficient code.  The ADA language adopted by DoD had literally millions of man-hours poured into it over the last couple of decades.  It's still in use but because of compiler problems, it has never lived up to its full potential.

Another difficulty is the lack of an experienced programmer base with which to write programs.  This would be the case with any new language.  It is not the case with 'C'.

NASA could do well by SequenceL or it might be a rathole down which millions of dollars could be poured to no avail.  Sure hope it's the former.


Offline lmike

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RE: CEV abort system gains a brain
« Reply #23 on: 12/22/2005 04:08 AM »
Quote
Dobbins - 21/12/2005  9:36 PM

The use of a solid booster first stage makes the LES harder to design and program. In the Mercury and Apollo systems the LES could shut down the booster if it was out of control. A solid rocket can't be shut down so the LES has to be capable of reacting to any failure modes that produce side thrust.

The Mercury LES didn't even use a computer, it's sequencer relied on relays and logic circuits. You could get by with something that simple on a liquid fueled rocket, though it was a nightmare to checkout. A LES for a solid will require a fairly complex program.


I agree, in general (see my post prior).  The solid first stage is a harder nut to crack for the LES.  It may seem a contradiction in terms, but some of my software devloping experience (medical/semiconductor inspection istrumentation) tells me that more complex tasks require simpler solutions (to be robust, understandable and debuggable) from the design perspective.  The reaction time requirement is tighter in this case(explodes/spins out of control due to imbalanced thrust due to faulty grain), sensor instrumentation is more limited as well (can't detect if a turbopump is losing speed...), control options are also more limited (no fuel line valves to close...), you are riding a firecracker basically... hence, no time for loading instructions/dereferencing memory/handling exceptions (gosh forbid)/running a shortest path algorithm in a decision net/running a state machine/...  If a bunch of 'if...then...' at the circuit gates level can do it (like say transistor relays/gates), then so it should be done*.  As simple *as possible*, but no simpler.  And the complex logic requirement is nowhere in sight here.

*it's not like they are going to need to debug/reset the thing once in flight(unlike the MER rovers, for example)... Hopefully...

Offline Avron

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RE: CEV abort system gains a brain
« Reply #24 on: 12/22/2005 04:46 AM »
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lmike - 22/12/2005  12:08 AM
you are riding a firecracker basically... hence, no time for loading instructions/dereferencing memory/handling exceptions (gosh forbid)/running a shortest path algorithm in a decision net/running a state machine/...  If a bunch of 'if...then...' at the circuit gates level can do it (like say transistor relays/gates), then so it should be done*.  As simple *as possible*, but no simpler.  And the complex logic requirement is nowhere in sight here.

*it's not like they are going to need to debug/reset the thing once in flight(unlike the MER rovers, for example)... Hopefully...

We are talking Abort system, so there really is not time to Debug, thats too late even if it was done by machine.. I totally agree, it has to be simple. The more complex, the more points of potential failure of the LES. The fault tree size and MTBF will just reduce the usefulness of the system.

Offline SimonShuttle

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RE: CEV abort system gains a brain
« Reply #25 on: 12/22/2005 09:00 AM »
Realtime, you mentioned about the Shuttle's systems being very much debugged over years. Is that a bit like having an old computer, but because there's no need for constant Windows patches it can run smoother than a newer computer?

The Shuttle flight computers seem to work very well, talking to the engines and back etc.etc. But some people redicule how old they are. Is that the case then, they work a lot better than their age may suggest because they are so debugged then do the job better than sticking some Window XP computers into the Orbiters?

Online Chris Bergin

RE: CEV abort system gains a brain
« Reply #26 on: 12/22/2005 09:58 AM »
That's one for the tech people on here, but I had heard about the age of the Orbiter systems, yet one speaks to the USA guys and they wouldn't swap the flight computers.

Offline darkenfast

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RE: CEV abort system gains a brain
« Reply #27 on: 12/22/2005 06:58 PM »
Regarding the need for speed in aborts, I believe the danger may not be quite as severe as some would imagine.   As I understand it, neither stage of the Crew Launch Vehicle is capable of "detonating" (as opposed to a fireball like Challenger experienced).   This is very well explained in the "Reliability and Crew Safety Study" done for ATK by SAIC (don't have the link handy, but it's easy to find).    The other thing is that a capsule is much more likely to survive either a fireball or aerodynamic loads from a vehicle breakup than something like the Orbiter, so even if the system isn't the fastest (in computer terms), the crew will likely survive.   Remember, it was the aerodynamics that actually destroyed Challenger.
I do believe that it's very important to have manual actuation, in addition to the automated system.


Offline realtime

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RE: CEV abort system gains a brain
« Reply #28 on: 12/22/2005 09:18 PM »
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SimonShuttle - 22/12/2005  5:00 AM

Realtime, you mentioned about the Shuttle's systems being very much debugged over years. Is that a bit like having an old computer, but because there's no need for constant Windows patches it can run smoother than a newer computer?

The Shuttle flight computers seem to work very well, talking to the engines and back etc.etc. But some people redicule how old they are. Is that the case then, they work a lot better than their age may suggest because they are so debugged then do the job better than sticking some Window XP computers into the Orbiters?
I didn't say that, but I may have implied it.  I agree.  The Shuttle flight control systems have been thoroughly debugged, and they don't constantly fiddle with them, so they tend toward stability.  Yet there is one thing I can guarantee you.

There is always one more bug.

With luck, they'll never find it.


Offline Do Shuttles Dream

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RE: CEV abort system gains a brain
« Reply #29 on: 12/23/2005 04:02 AM »
Thanks, that's interesting. I want to get into computers as a career and this is all very interesting.

Offline lmike

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RE: CEV abort system gains a brain
« Reply #30 on: 12/23/2005 04:04 AM »
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darkenfast - 22/12/2005  1:58 PM

Regarding the need for speed in aborts, I believe the danger may not be quite as severe as some would imagine.   As I understand it, neither stage of the Crew Launch Vehicle is capable of "detonating" (as opposed to a fireball like Challenger experienced).   This is very well explained in the "Reliability and Crew Safety Study" done for ATK by SAIC (don't have the link handy, but it's easy to find).    The other thing is that a capsule is much more likely to survive either a fireball or aerodynamic loads from a vehicle breakup than something like the Orbiter, so even if the system isn't the fastest (in computer terms), the crew will likely survive.   Remember, it was the aerodynamics that actually destroyed Challenger.
I do believe that it's very important to have manual actuation, in addition to the automated system.


A Titan IVB's SRMU exploded due to faulty grain at the section seams.  On the testing pad.  Wiped out the whole testing area.  One never knows...

Anyway, this may turn out to be true, but...  it may not.  You need to cover as much as you can.  Or if it does blow up then it's the ATK's fault, not the LES's?   (btw, the non-detonation spec. is also based on assumptions such as the solid fuel manufacture)  I've seen plenty of hardware/documentation bugs as well.  

Actually, my biggest nightmare here is the rogue CLV ramming the CEV/LES stack as it tries to get away (ATK proposed to blow holes in the sides, AFAIK, to kill off thrust)

In the case of the LES, it's 'the faster the better' & 'the simpler the better'  Just in case.  This is a system whose sole purpose is saving lives in extreme situations within some short minutes that it's online before being thrown off the stack.  If no good arguments can be made in favor of complicating and delaying the process (such as software maintenance/compatibility/readability/... as we in the commercial world often do)), then it's 'the faster the better'.  Not having to withstand a first stage fireball and being some miles away is much preferable to having to go through one.  This seems obvious to me.

I would never start off the design of a crew escape system based on preconceived assumptions and blind trust in the written documents.  

Here's the objective for the designers... All you've got are these pressure/temperature/acceleration sensors and these gyros and these eyes on the deck for input (forget the first stage folks assurances), these pyros for the output -- figure if I'm in trouble and do what you can to save my a$$.

Offline darkenfast

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RE: CEV abort system gains a brain
« Reply #31 on: 12/25/2005 06:21 PM »
My last post was written badly.  I meant to emphasize that I think that the need for reliability is more important than the need for ultra-quick reaction time.  The sort of parameters that served for the Apollo LES should serve here, unless there's some problem with the Apollo system that I never heard about.

Offline rsp1202

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RE: CEV abort system gains a brain
« Reply #32 on: 12/28/2005 06:32 PM »
Check out http://www.usspacenews.com/ for graphics of CEV abort-test boosters.

Offline publiusr

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RE: CEV abort system gains a brain
« Reply #33 on: 12/29/2005 07:14 PM »
In 2008 they will have a dry stage atop the full Stick IIRC.

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