Apollo 8 and a LM
Greg D. Moore (Strider)
LM since the LM wasn't ready.
What exactly wasn't ready? I suspect it was more than simply being
overweight (since it was overweight as late as Apollo 10).
Thinking about it, was ANY thought given to launching it, even if it was
only dead weight to be used as a lifeboat (ala Apollo 13). I.e. could they
have accomplished Apollo 8 even more safely than they did?
--
Greg Moore
Ask me about lily, an RPI based CMC.
kevin willoughby
> History says that Apollo 8 was launched to the Moon despite the risk,
> w/o an LM since the LM wasn't ready.
>
> What exactly wasn't ready? I suspect it was more than simply being
> overweight (since it was overweight as late as Apollo 10).
I strongly recommend "Digital Apollo" by David Mindell. Especially if
you have any interest in computers, either hardware or software.
Mindell makes clear that the software to actually land the LM wasn't
ready until fairly late, certainly not for Apollo 8. Heck, there was a
scramble to complete the non-landing lunar software in time for
Christmas 1968.
--
Kevin Willoughby kevinwi...@acm.org.invalid
It doesn't take many trips in Air Force One
to spoil you. -- Ronald Reagan
Greg D. Moore (Strider)
news:3YSdnT-RbM0B7W_U...@giganews.com...
> Greg D. Moore (Strider) wrote:
>> History says that Apollo 8 was launched to the Moon despite the risk, w/o
>> an LM since the LM wasn't ready.
>>
>> What exactly wasn't ready? I suspect it was more than simply being
>> overweight (since it was overweight as late as Apollo 10).
>
> I strongly recommend "Digital Apollo" by David Mindell. Especially if you
> have any interest in computers, either hardware or software.
>
> Mindell makes clear that the software to actually land the LM wasn't ready
> until fairly late, certainly not for Apollo 8. Heck, there was a scramble
> to complete the non-landing lunar software in time for Christmas 1968.
Umm, why? The LM wasn't used by then.
But that's sort of my point. Forget using the LM for anything other than a
lifeboat, pretty much as it was used during Apollo 13. Were there technical
issues that would have prevented that?
Joe Pfeiffer
> Greg D. Moore (Strider) wrote:
>> History says that Apollo 8 was launched to the Moon despite the
>> risk, w/o an LM since the LM wasn't ready.
>>
>> What exactly wasn't ready? I suspect it was more than simply being
>> overweight (since it was overweight as late as Apollo 10).
>
> I strongly recommend "Digital Apollo" by David Mindell. Especially if
> you have any interest in computers, either hardware or software.
Not directly related to the original question, but I'll strongly second
the suggestion of Digital Apollo. Outstanding book, giving a lot of
insight into computers in the 1960s, and the conflict between a "man in
control" vs. "machine in control" mentality.
behl...@gmail.com
<mooregr_deletet...@greenms.com> wrote:
> "kevin willoughby" <kevinwilloug...@acm.org.invalid> wrote in message
It wasn't ready, meaning behind schedule
Ken S. Tucker
<mooregr_deletet...@greenms.com> wrote:
> History says that Apollo 8 was launched to the Moon despite the risk, w/o an
> LM since the LM wasn't ready.
That statement implies a spec that the LM could be used as
a "lifeboat", we got lucky the Apollo 13 SM malfunctioned when
it did. If it happened when the LM was on the moon...
> What exactly wasn't ready? I suspect it was more than simply being
> overweight (since it was overweight as late as Apollo 10).
The LM was the most complicated 2 stage manned
rocket ever built. I'd imagine the assembly instructions
and checklist would run to nearly 1,000,000 items.
(anyone know?).
The engineers could not sign-off a unit 90% complete,
unless that was pre-designed.
> Thinking about it, was ANY thought given to launching it, even if it was
> only dead weight to be used as a lifeboat (ala Apollo 13). I.e. could they
> have accomplished Apollo 8 even more safely than they did?
Not realistically, after all, Apollo 8 proved to be 100% safe.
I think the Constellation Earth-Moon-Earth ferry-boat should
have redundancy.
IIRC the Apollo 13 was a freak accident caused by a
check-list malfunction, (had the wrong switch).
> Greg Moore
> Ask me about lily, an RPI based CMC.
Regards
Ken
Greg D. Moore (Strider)
news:193b8408-12b5-4d8f...@q33g2000pra.googlegroups.com...
> On Apr 24, 6:44 am, "Greg D. Moore \(Strider\)"
> <mooregr_deletet...@greenms.com> wrote:
>> History says that Apollo 8 was launched to the Moon despite the risk, w/o
>> an
>> LM since the LM wasn't ready.
>
> That statement implies a spec that the LM could be used as
> a "lifeboat", we got lucky the Apollo 13 SM malfunctioned when
> it did. If it happened when the LM was on the moon...
Yes, the astronauts would have died. However, the lifeboat scenario had
been discussed prior to Apollo 13. And specifically in Apollo 8 it would
have provided a lifeboat capability during the entire flight.
>
> The LM was the most complicated 2 stage manned
> rocket ever built. I'd imagine the assembly instructions
> and checklist would run to nearly 1,000,000 items.
> (anyone know?).
> The engineers could not sign-off a unit 90% complete,
> unless that was pre-designed.
In other words, you don't know what exactly wasn't ready. And your
statement isn't completely accurate in any case since both Apollo 9 and
Apollo 10 flew with LMs that did not meet the landing criteria, which
arguably means they weren't 'complete'.
>
>> Thinking about it, was ANY thought given to launching it, even if it was
>> only dead weight to be used as a lifeboat (ala Apollo 13). I.e. could
>> they
>> have accomplished Apollo 8 even more safely than they did?
>
> Not realistically, after all, Apollo 8 proved to be 100% safe.
> I think the Constellation Earth-Moon-Earth ferry-boat should
> have redundancy.
Umm, your statement doesn't really follow and is only ex post facto. We
know NOW that it was 100% successful. It wasn't 100% safe though. A failure
could have killed the crew.
>
> IIRC the Apollo 13 was a freak accident caused by a
> check-list malfunction, (had the wrong switch).
Not quite.
--
Greg D. Moore (Strider)
Umm, could you be more specific. What wasn't ready? Clearly it was behind
schedule, but what items (besides apparently software and mass?)
Ken S. Tucker
<mooregr_deletet...@greenms.com> wrote:
> "Ken S. Tucker" <dynam...@vianet.on.ca> wrote in messagenews:193b8408-12b5-4d8f...@q33g2000pra.googlegroups.com...
>
> > On Apr 24, 6:44 am, "Greg D. Moore \(Strider\)"
> > <mooregr_deletet...@greenms.com> wrote:
> >> History says that Apollo 8 was launched to the Moon despite the risk, w/o
> >> an
> >> LM since the LM wasn't ready.
>
> > That statement implies a spec that the LM could be used as
> > a "lifeboat", we got lucky the Apollo 13 SM malfunctioned when
> > it did. If it happened when the LM was on the moon...
>
> Yes, the astronauts would have died. However, the lifeboat scenario had
> been discussed prior to Apollo 13. And specifically in Apollo 8 it would
> have provided a lifeboat capability during the entire flight.
>
>
>
> > The LM was the most complicated 2 stage manned
> > rocket ever built. I'd imagine the assembly instructions
> > and checklist would run to nearly 1,000,000 items.
> > (anyone know?).
> > The engineers could not sign-off a unit 90% complete,
> > unless that was pre-designed.
>
> In other words, you don't know what exactly wasn't ready. And your
> statement isn't completely accurate in any case since both Apollo 9 and
> Apollo 10 flew with LMs that did not meet the landing criteria, which
> arguably means they weren't 'complete'.
Agreed. The LM has various degrees of preparation,
for example, from zero to fully fueled on both stages
and the Life Support topped up, and the requirement
for LM rendevous and extraction by CSM.
If I might provide a bit of back-drop, the Earth orbit
rendevous was only done previously (IIRC) in the
Gemini Program, which had some bugs, also (sadly)
the Apollo Capsule fire caused Apollo managers and
engineers a set back in confidence.
Well I'm sure you can imagine the complexity of
fueling the 2 stage LM with it's hypergolics etc.
(Life Support) on top of the 3 Stages of the SV,
there isn't a short-cut.
> >> Thinking about it, was ANY thought given to launching it, even if it was
> >> only dead weight to be used as a lifeboat (ala Apollo 13). I.e. could
> >> they
> >> have accomplished Apollo 8 even more safely than they did?
>
> > Not realistically, after all, Apollo 8 proved to be 100% safe.
> > I think the Constellation Earth-Moon-Earth ferry-boat should
> > have redundancy.
>
> Umm, your statement doesn't really follow and is only ex post facto. We
> know NOW that it was 100% successful. It wasn't 100% safe though. A failure
> could have killed the crew.
There is no such thing as 100% safe.
> > IIRC the Apollo 13 was a freak accident caused by a
> > check-list malfunction, (had the wrong switch).
>
> Not quite.
True, I over-simplified, though the malfunction was caused
by an "over-sight" on the ground, (rather than a random act
of nature), that was missed by engineers-technicians, so
I use the umbrella sematic, "check-list malfunction", to
focus attention there to an engineering inconsistency.
> Greg Moore
Regards
Ken S. Tucker
Pat Flannery
Greg D. Moore (Strider) wrote:
>
> Umm, could you be more specific. What wasn't ready? Clearly it was
> behind schedule, but what items (besides apparently software and mass?)
I got Curious about this, so I went over to the Encyclopedia
Astronautica article on the LM with its comprehensive chronology of the
LM program: http://www.astronautix.com/craft/apollolm.htm
It wasn't one thing, it was a whole pile of things getting behind
schedule or just not working right.
As late as October 1968 LM propellant tanks were rupturing during ground
tests, and there were still changes being made to it into early 1969...
in fact, it's pretty amazing they had it ready to go at all anytime in
1969 after reading all the plethora of problems they were running into
regarding it.
Even without the Apollo fire occurring and slowing the program down, the
LM would have been nowhere near ready to go when the CSM was, and the
first lunar landing would probably occurred almost exactly when it did,
as the LM was the limiting factor on when that could happen.
The LM lifeboat concept came up in 1966:
"1966 March 17 - Apollo time-critical aborts due to service propulsion
system failure investigated - Program: Apollo.
John D. Hodge, Chief of MSC's Flight Control Division, proposed that
time-critical aborts in the event of a service propulsion system failure
after translunar injection (TLI; i.e., insertion on a trajectory toward
the moon) be investigated. Time-critical abort was defined as an abort
occurring within 12 hours after TLI and requiring reentry in less than
two days after the abort.
He suggested that if an SPS failed the service module be jettisoned for
a time-critical abort and both LEM propulsion systems be used for earth
return, reducing the total time to return by approximately 60 hours. As
an example, if the time of abort was 10 hours after translunar
injection, he said, this method would require about 36 hours; if the SM
were retained the return time would require about 96 hours.
He added that the LEM/CM-only configuration should be studied for any
constraints that would preclude initiating this kind of time-critical
abort. Some of the factors to be considered should be:
1. maximum time the LEM environmental control system could support
two or three men on an earth return;
2. maximum time the CM electrical system could support minimum
power-up condition;
3. time constraints on completely powering down the CM and using the
LEM systems for support;
4. effects on planned landing areas from an open loop reentry mode;
5. stability of the LEM/CM configuration during the descent and
ascent propulsion burns;
6. total time to return using the descent propulsion system only or
both the LEM's descent propulsion system and ascent propulsion system; and
7. communications with Manned Space Flight Network required to
support this abort."
John D. Hodge was a man way ahead of the curve here, and it's a very
good thing that he started the investigations into this possibility.
Pat
Pat Flannery
Ken S. Tucker wrote:
>
> Agreed. The LM has various degrees of preparation,
> for example, from zero to fully fueled on both stages
> and the Life Support topped up, and the requirement
> for LM rendevous and extraction by CSM.
>
> If I might provide a bit of back-drop, the Earth orbit
> rendevous was only done previously (IIRC) in the
> Gemini Program, which had some bugs, also (sadly)
> the Apollo Capsule fire caused Apollo managers and
> engineers a set back in confidence.
>
> Well I'm sure you can imagine the complexity of
> fueling the 2 stage LM with it's hypergolics etc.
> (Life Support) on top of the 3 Stages of the SV,
> there isn't a short-cut.
>
Reading between the lines on the EA article on the LM, you can tell that
although NASA was trying to talk itself into the concept of the first
manned LM test being as safe on a orbital Moon flight as in LEO, they
themselves weren't buying it, and definitely wanted the first test to be
in LEO, so that if something went wrong it at least wasn't happening
days away from a safe return to Earth.
Pat
Joe Pfeiffer
>
> IIRC the Apollo 13 was a freak accident caused by a
> check-list malfunction, (had the wrong switch).
No -- it was a freak accident caused by damage resulting from the tank
being dropped, and a lot of anomolies shortly before launch being
ignored (well, I guess that last factor moves it from "freak" to "nearly
routine").
http://science.ksc.nasa.gov/history/apollo/apollo-13/apollo-13.html
Joe Pfeiffer
> by an "over-sight" on the ground, (rather than a random act
> of nature), that was missed by engineers-technicians, so
> I use the umbrella sematic, "check-list malfunction", to
> focus attention there to an engineering inconsistency.
Ah, OK -- the way you worded it, I thought you meant an error by one of
the astronauts.
Chris Jones
> History says that Apollo 8 was launched to the Moon despite the risk, w/o an LM
> since the LM wasn't ready.
>
> What exactly wasn't ready? I suspect it was more than simply being overweight
> (since it was overweight as late as Apollo 10).
I think there was no LM anywhere near ready to be launched into space.
The only hope of there being one to launch on Apollo 8 was to delay 8.
Once you've done that, you might as well fly 8 on its original mission,
the checkout of the LM. Since the Saturn V was deemed ready (somewhat
of a stretch, but it worked out in the end) and the CM was deemed ready
(also a somewhat risky assumption), flying a lunar mission was deemed
the best way to meet the end-of-1969 deadline.
>
> Thinking about it, was ANY thought given to launching it, even if it was only
> dead weight to be used as a lifeboat (ala Apollo 13). I.e. could they have
> accomplished Apollo 8 even more safely than they did?
They weren't looking for maximum safety, they were looking at the best
way to safely meet the deadline.
David Higgins
> kevin willoughby <kevinwi...@acm.org.invalid> writes:
>> I strongly recommend "Digital Apollo" by David Mindell. Especially if
>> you have any interest in computers, either hardware or software.
>
> Not directly related to the original question, but I'll strongly second
> the suggestion of Digital Apollo.
+1 (Thirded?)
I bought "Digital Apollo" and David Wood's "How Apollo Flew to the Moon"
a few months back. Both are quite good.
Ken S. Tucker
Sorry guys, my language was poor, here's a quote from
the link (previously posted),
" Due to an oversight in replacing an underrated component during a
design modification, "
BTW, I attended 2 lectures on the subject, 1st by an
electronics engineer and 2nd by James Lovell, and I
still don't fully understand it, but enough.
Ken
kevin willoughby
> "kevin willoughby" <kevinwi...@acm.org.invalid> wrote in message
> news:3YSdnT-RbM0B7W_U...@giganews.com...
>> Greg D. Moore (Strider) wrote:
>>> History says that Apollo 8 was launched to the Moon despite the risk,
>>> w/o an LM since the LM wasn't ready.
>>>
>>> What exactly wasn't ready? I suspect it was more than simply being
>>> overweight (since it was overweight as late as Apollo 10).
>>
>> I strongly recommend "Digital Apollo" by David Mindell. Especially if
>> you have any interest in computers, either hardware or software.
>>
>> Mindell makes clear that the software to actually land the LM wasn't
>> ready until fairly late, certainly not for Apollo 8. Heck, there was a
>> scramble to complete the non-landing lunar software in time for
>> Christmas 1968.
>
> Umm, why? The LM wasn't used by then.
The LM and the CSM used the same computer. There was only one team
developing the flight software for Apollo. For Apollo 8, that team was
having trouble getting the CSM software right. Just reusing the Apollo 7
software wasn't an option. CSM software was one of the gating factors on
the "8 to the moon" decision.
Details in Digital Apollo.
kevin willoughby
> Not directly related to the original question, but I'll strongly second
> the suggestion of Digital Apollo. Outstanding book, giving a lot of
> insight into computers in the 1960s, and the conflict between a "man in
> control" vs. "machine in control" mentality.
One of my favorite anecdotes from the book was on just that motif.
At the very first meeting ever of the Society of Experimental Test
Pilots, one member gave a talk about the issues of placing a computer
between the pilot and the controls. His conclusion was that this was a
bad idea. The pilot should have direct control of his 'craft, with no
intermediaries. This guy's name: Neil Armstrong. (My irony-meter went
*ping* at that point.)
Years later, Armstrong was talking with some folks at Dryden who wanted
to experiment with an analog computer in a fly-by-wire airplane.
Armstrong recommended that they use a digital system, explaining that
was how he had landed on the moon. Amazingly, when a surplus Apollo
flight computer was used to fly that airplane, well over half the
software was unchanged from the software that flew a spacecraft.
Oh yeah, Armstrong's talk on computers between the pilot and the
controls was delivered on October 4, 1957. Yes, *that* October 4, 1957.
(Excuse me, I have to return my irony-meter to the factory for an overhaul.)
kevin willoughby
So how many of us have read that book? And why has it been so rarely
discussed around here?
Derek Lyons
>David Higgins wrote:
>
>> I bought "Digital Apollo" and David Wood's "How Apollo Flew to the Moon"
>> a few months back. Both are quite good.
>
>So how many of us have read that book?
I haven't, but I have a lot of hobbies and interests and a to be read
stack enough to keep me busy for at least five years if I do nothing
but read. Heck, I'm just now finishing 'First Man'.
Digital Apollo is on the list, but I haven't gotten around to it yet.
>And why has it been so rarely discussed around here?
It isn't rocket engines, it isn't NASA (other than
Mercury-Gemini-Apollo) bashing, it doesn't have many pretty pictures,
it is deep technical detail.
In the minds of many that leaves its at-bat at 1-3 and headed for the
dugout.
D.
--
Touch-twice life. Eat. Drink. Laugh.
http://derekl1963.livejournal.com/
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL
Derek Lyons
>Joe Pfeiffer wrote:
>> Not directly related to the original question, but I'll strongly second
>> the suggestion of Digital Apollo. Outstanding book, giving a lot of
>> insight into computers in the 1960s, and the conflict between a "man in
>> control" vs. "machine in control" mentality.
>
>One of my favorite anecdotes from the book was on just that motif.
>
>At the very first meeting ever of the Society of Experimental Test
>Pilots, one member gave a talk about the issues of placing a computer
>between the pilot and the controls. His conclusion was that this was a
>bad idea. The pilot should have direct control of his 'craft, with no
>intermediaries. This guy's name: Neil Armstrong. (My irony-meter went
>*ping* at that point.)
In 1957 I wouldn't find that an unusual viewpoint. Computers were in
their infancy, and the waters around the Cape were becoming Snark
infested.
Greg D. Moore (Strider)
news:49f7f6db....@news.supernews.com...
> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
>
>>David Higgins wrote:
>>
>>> I bought "Digital Apollo" and David Wood's "How Apollo Flew to the Moon"
>>> a few months back. Both are quite good.
>>
>>So how many of us have read that book?
>
> I haven't, but I have a lot of hobbies and interests and a to be read
> stack enough to keep me busy for at least five years if I do nothing
> but read. Heck, I'm just now finishing 'First Man'.
Very good book. I thought it did a decent job of revealing the man behind
the myth.
>
> Digital Apollo is on the list, but I haven't gotten around to it yet.
>
>>And why has it been so rarely discussed around here?
>
> It isn't rocket engines, it isn't NASA (other than
> Mercury-Gemini-Apollo) bashing, it doesn't have many pretty pictures,
> it is deep technical detail.
>
> In the minds of many that leaves its at-bat at 1-3 and headed for the
> dugout.
>
Being an IT person I'll have to say software and related subjects are far
from glamorous. That's for sure.
They're definitely the unsung workhorses of the aerospace program.
But then again I'm biased. :-)
Joe Pfeiffer
>
> Years later, Armstrong was talking with some folks at Dryden who
> wanted to experiment with an analog computer in a fly-by-wire
> airplane. Armstrong recommended that they use a digital system,
> explaining that was how he had landed on the moon. Amazingly, when a
> surplus Apollo flight computer was used to fly that airplane, well
> over half the software was unchanged from the software that flew a
> spacecraft.
Something I find interesting is just how late the daebate over
analog/digital lasted. As a CS undergrad in the late 1970s, analog
computers seemed just unbearably quaint. And the first generation of
automotive engine computers was analog, in exactly that time frame!
Pat Flannery
Ken S. Tucker wrote:
>
> BTW, I attended 2 lectures on the subject, 1st by an
> electronics engineer and 2nd by James Lovell, and I
> still don't fully understand it, but enough.
>
Don't forget the stir-motor test with the wrong voltage before it was
installed in the SM that damaged the insulation on it.
Pat
Derek Lyons
>kevin willoughby <kevinwi...@acm.org.invalid> writes:
>>
>> Years later, Armstrong was talking with some folks at Dryden who
>> wanted to experiment with an analog computer in a fly-by-wire
>> airplane. Armstrong recommended that they use a digital system,
>> explaining that was how he had landed on the moon. Amazingly, when a
>> surplus Apollo flight computer was used to fly that airplane, well
>> over half the software was unchanged from the software that flew a
>> spacecraft.
>
>Something I find interesting is just how late the daebate over
>analog/digital lasted.
Why? It's not like digital walked onto the field and blew all other
competitors away.
While digital *computing* offers some advantages (and disadvantages)
compared to analog, digital *computers* took a long time to get small
enough, reliable enough, and cheap enough to completely displace
analog machines.
>As a CS undergrad in the late 1970s, analog computers seemed just
>unbearably quaint.
That's a fault of your curriculum.
>And the first generation of automotive engine computers was analog,
>in exactly that time frame!
Which should tell you something. But digital uber alles so you reject
evidence in favor of dogma.
Greg D. Moore (Strider)
news:871vrgo...@duck-dodgers.hsd1.ma.comcast.net...
> "Greg D. Moore (Strider)" <mooregr_d...@greenms.com> writes:
>
>> History says that Apollo 8 was launched to the Moon despite the risk, w/o
>> an LM
>> since the LM wasn't ready.
>>
>> What exactly wasn't ready? I suspect it was more than simply being
>> overweight
>> (since it was overweight as late as Apollo 10).
>
> I think there was no LM anywhere near ready to be launched into space.
Yes, but I'm wondering on specifics.
> The only hope of there being one to launch on Apollo 8 was to delay 8.
> Once you've done that, you might as well fly 8 on its original mission,
> the checkout of the LM.
Agreed. And it was a gutsy move that could have ended the space race had it
been the Apollo 13 CSM (or more accurately, had the LOX tank.)
>>
>> Thinking about it, was ANY thought given to launching it, even if it was
>> only
>> dead weight to be used as a lifeboat (ala Apollo 13). I.e. could they
>> have
>> accomplished Apollo 8 even more safely than they did?
>
> They weren't looking for maximum safety, they were looking at the best
> way to safely meet the deadline.
Note, I never said maximum safety. For that, you never leave the ground.
I was just suggesting increased safety.
Greg D. Moore (Strider)
That makes a lot of sense.
And I definitely have to add to my reading list!
kevin willoughby
> Something I find interesting is just how late the daebate over
> analog/digital lasted. As a CS undergrad in the late 1970s, analog
> computers seemed just unbearably quaint. And the first generation of
> automotive engine computers was analog, in exactly that time frame!
We've been writing software for, roughly, 70 years. Yet writing a
program that does exactly what it is supposed to do is still incredibly
difficult. In contrast, analog computers don't have the same set of
scary failure modes -- they can fail, but not in the bizarre ways a
digital system can. A engineer making a "you bet your life" decision can
be forgiven for the conservative choice.
kevin willoughby
> Years later, Armstrong was talking with some folks at Dryden who wanted
> to experiment with an analog computer in a fly-by-wire airplane.
> Armstrong recommended that they use a digital system [...]
A friend has emailed me, suggesting that I got the details wrong. Some
of the Dryden guys wanted a digital computer but couldn't find an
adequate one. They knew Armstrong from when they all worked on the X-15.
Armstrong recommended using one of the Apollo guidance computers.
Details in http://klabs.org/history/history_docs/reports/dfbw_tomayko.pdf
page 31.
kevin willoughby
> [Digital Apollo] isn't rocket engines, it isn't NASA (other than
> Mercury-Gemini-Apollo) bashing, it doesn't have many pretty pictures,
> it is deep technical detail.
I'll quibble about that third point. The book is quite readable without
a lot of technical prerequisites. As one example, he correctly explains
the famous program alarms on the first lunar landing correctly. The
common explanation that "they left a radar on" is so over-simplified as
to be misleading. Every other accurate explanation I've read tosses
around tech-babble ("race condition" "phase skew"). Mindell is clear,
accurate and avoids the tech-babble.
kevin willoughby
> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
>> At the very first meeting ever of the Society of Experimental Test
>> Pilots, one member gave a talk about the issues of placing a computer
>> between the pilot and the controls. His conclusion was that this was a
>> bad idea. The pilot should have direct control of his 'craft, with no
>> intermediaries.
>
> their infancy, and the waters around the Cape were becoming Snark
> infested.
All true, but Mindell hints that there may also have been a bit of pilot
Ludditism.
The correct use of automated systems is a major motif of the book.
Joe Pfeiffer
> Joe Pfeiffer <pfei...@cs.nmsu.edu> wrote:
>
>>kevin willoughby <kevinwi...@acm.org.invalid> writes:
>>>
>>> Years later, Armstrong was talking with some folks at Dryden who
>>> wanted to experiment with an analog computer in a fly-by-wire
>>> airplane. Armstrong recommended that they use a digital system,
>>> explaining that was how he had landed on the moon. Amazingly, when a
>>> surplus Apollo flight computer was used to fly that airplane, well
>>> over half the software was unchanged from the software that flew a
>>> spacecraft.
>>
>>Something I find interesting is just how late the daebate over
>>analog/digital lasted.
>
> Why? It's not like digital walked onto the field and blew all other
> competitors away.
>
> While digital *computing* offers some advantages (and disadvantages)
> compared to analog, digital *computers* took a long time to get small
> enough, reliable enough, and cheap enough to completely displace
> analog machines.
>
>>As a CS undergrad in the late 1970s, analog computers seemed just
>>unbearably quaint.
>
> That's a fault of your curriculum.
I don't think it's specifically a fault of my curriculum -- it's
a fault of the general CS mind-set, which identifies computers with
automata. I'd be surprised if there were many CS departments that did
it differently (though I imagine many EE departments saw things very
differently).
>>And the first generation of automotive engine computers was analog,
>>in exactly that time frame!
>
> Which should tell you something. But digital uber alles so you reject
> evidence in favor of dogma.
Yes, it does tell me something -- that your original point above, that
digital didn't just walk over analog, is valid. And apparently my
phrasing wasn't clear, because that was my original point as well, and
that a student's perceptions at the time were incorrect.
If I were going to reject evidence in favor of dogma, I wouldn't have
brought it up.
Fred J. McCall
:
The environment under the hood of a car is incredibly hostile to
electronics, both in temperature and vibration. It took a long time
to get to digital components that could stand up to that sort of thing
for the years at a time necessary for use in something like a car.
It sounds to me like you might have been miseducated somewhat.
--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw
Derek Lyons
>Joe Pfeiffer wrote:
>
>> Something I find interesting is just how late the daebate over
>> analog/digital lasted. As a CS undergrad in the late 1970s, analog
>> computers seemed just unbearably quaint. And the first generation of
>> automotive engine computers was analog, in exactly that time frame!
>
>We've been writing software for, roughly, 70 years. Yet writing a
>program that does exactly what it is supposed to do is still incredibly
>difficult.
Nit, ITYM "writing a non trivial program". Of course, the meaning of
non trivial is a variable.
>In contrast, analog computers don't have the same set of
>scary failure modes -- they can fail, but not in the bizarre ways a
>digital system can.
No, they don't have the same set of scary and bizarre failure modes
that a digital system has. They have their *own* set of scary and
bizarre failure modes. I remember un fondly being at sea for a test
of the hovering and missile compensation controller - when energized,
it commanded all valves to the 'flood tanks' position and steadfastly
insisted we were going *up*.
Analog computers are more easily maintained than digital too, and a
dammed good thing because they can need a lot of maintenance.
I much preferred troubleshooting relay based controllers though - the
basic tools were a stethoscope and a rubber mallet.
Joe Pfeiffer
> Joe Pfeiffer <pfei...@cs.nmsu.edu> wrote:
>
> :kevin willoughby <kevinwi...@acm.org.invalid> writes:
> :>
> :> Years later, Armstrong was talking with some folks at Dryden who
> :> wanted to experiment with an analog computer in a fly-by-wire
> :> airplane. Armstrong recommended that they use a digital system,
> :> explaining that was how he had landed on the moon. Amazingly, when a
> :> surplus Apollo flight computer was used to fly that airplane, well
> :> over half the software was unchanged from the software that flew a
> :> spacecraft.
> :
> :Something I find interesting is just how late the daebate over
> :analog/digital lasted. As a CS undergrad in the late 1970s, analog
> :computers seemed just unbearably quaint. And the first generation of
> :automotive engine computers was analog, in exactly that time frame!
> :
>
> The environment under the hood of a car is incredibly hostile to
> electronics, both in temperature and vibration. It took a long time
> to get to digital components that could stand up to that sort of thing
> for the years at a time necessary for use in something like a car.
>
> It sounds to me like you might have been miseducated somewhat.
No, I was in a CS program, and CS is very much a place where
computation==automata.
Ken S. Tucker
wrote:
> On Sun, 26 Apr 2009 14:22:25 EDT, Pat Flannery <flan...@daktel.com>
> wrote:
>
> >Don't forget the stir-motor test with the wrong voltage before it was
> >installed in the SM that damaged the insulation on it.
>
>
> The tank contained several components relevant to the accident:
>
> * a quantity sensor;
>
> * a fan to stir the tank contents for more accurate quantity
> measurements;
>
> * a heater to vaporize liquid oxygen as needed;
>
> * a thermostat to protect the heater;
>
> * a temperature sensor;
>
> * and fill and drain valves and piping.
>
> The heater and protection thermostat were originally designed for the
> command module's 28-volt DC bus. However, their specifications were
> changed to allow a 65 volt ground supply to pressurize the tanks more
> rapidly. The tank subcontractor Beechcraft never upgraded the
> thermostat to handle the higher voltage.
Thanks OM, I term that a "check-list" malfunction, what
would be a better term?
> The temperature sensor could not read above the highest operational
> temperature of the heater, about 100 �F (38 �C). Ordinarily this was
> not a problem because the thermostat was designed to open at 80 �F (27
> �C).
>
> The oxygen shelf carrying the oxygen tanks was originally installed in
> the Apollo 10 service module. It was removed to fix a potential
> electromagnetic interference problem. During removal, the shelf was
> accidentally dropped about 2 inches (5.1 cm) because a retaining bolt
> had not been removed. The tank appeared undamaged but a loosely
> fitting filling tube was apparently damaged, and photographs suggested
> that the close-out cap on the top of the tank may have hit the fuel
> cell shelf. The report of the Apollo 13 review board considers the
> probability of tank damage during this incident to be "rather
> low".[15]
>
> After the tank was filled for ground testing, it could not be emptied
> through the normal drain line. To avoid delaying the mission to
> replace the tank, the heater was connected to 65V ground power to boil
> off the oxygen. Lovell signed off on this procedure. It should have
> taken a few days at the thermostatic opening temperature of 80 �F (27
> �C). However, when the thermostat opened, the 65-volt supply fused its
> contacts closed and the heater remained powered.
I'm uncertain the contacts fused at the moment of closure or
when the switch wanted to open since it closed and didn't
reopen. Anyway that's what I understand too.
Thanks for the details
Ken
...
Pat Flannery
Joe Pfeiffer wrote:
>
> I don't think it's specifically a fault of my curriculum -- it's
> a fault of the general CS mind-set, which identifies computers with
> automata. I'd be surprised if there were many CS departments that did
> it differently (though I imagine many EE departments saw things very
> differently).
>
Surprisingly, analog is a lot closer to the way our brains work than
binary digital ever was.
Our neurons fire via a greater or lesser stimuli, and the total effect
on them and how strongly they fire is a variable thing rather than a
simple on/off binary effect.
New research has suggested that human-type AI may be far easier to
accomplish via analog theories than digital ones.
You ever want to see the failure of a "0/1" binary approach to the
world, look at the history of the U.S. foreign policy since 2000.
Everyone in the world was either our "great friend" or our "evil enemy",
with no shades of any differentiation between the two.
America had learned to think in the same way that its computers did.
0 = evil; 1 = good.
A horrible sort of math that would let the "1's" do whatever was needed
to the "0's" to remove them from the program, as they were screwing it
up, and not letting it run right.
It needed de-bugging, and those bugs needed to be removed without
hesitation.
Not from any sort of emotion of course, but simply for the sake of
efficiency. :-D
Pat
======================================= MODERATOR'S COMMENT:
Ok, really starting to drift here. Let's try to avoid going to far down the political path, we have places for that. GdM
Jan Vorbrüggen
> binary digital ever was.
> Our neurons fire via a greater or lesser stimuli, and the total effect
> on them and how strongly they fire is a variable thing rather than a
> simple on/off binary effect.
The "bad thing" about digital systems is not the 0/1 thing, but that
operation and in particular failures can be highly nonlinear (e.g.,
accidentally setting the MSB on a value that should be near zero). All
sorts of damping etc. that analog systems show don't exist in the
digital world (although interfacing a digital system to the real world
almost always introduces such damping, in part precisely for that purpose).
Neural systems, however, _are_ highly nonlinear, show all sorts of
collective and chaotic phenomena, and so on. Remember, these are active
systems consuming lots of power to keep working. From my point of view,
they're a lot more like a digital than like an analog system.
Jan
Joe Pfeiffer
> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
>
>>Joe Pfeiffer wrote:
>>
>>> Something I find interesting is just how late the daebate over
>>> analog/digital lasted. As a CS undergrad in the late 1970s, analog
>>> computers seemed just unbearably quaint. And the first generation of
>>> automotive engine computers was analog, in exactly that time frame!
>>
>>We've been writing software for, roughly, 70 years. Yet writing a
>>program that does exactly what it is supposed to do is still incredibly
>>difficult.
>
> Nit, ITYM "writing a non trivial program". Of course, the meaning of
> non trivial is a variable.
That statement pretty much defines it -- any program that does
*exactly* what it's supposed to do must be trivial :)
Neil Gerace
> Surprisingly, analog is a lot closer to the way our brains work than
> binary digital ever was.
The more bits per unit of information, the more precision each unit has and the more the system looks like analogue
rather than digital :)
Ken S. Tucker
> kevin willoughby <kevinwilloug...@acm.org.invalid> wrote:
> >Joe Pfeiffer wrote:
>
> >> Something I find interesting is just how late the daebate over
> >> analog/digital lasted. As a CS undergrad in the late 1970s, analog
> >> computers seemed just unbearably quaint. And the first generation of
> >> automotive engine computers was analog, in exactly that time frame!
>
> >We've been writing software for, roughly, 70 years. Yet writing a
> >program that does exactly what it is supposed to do is still incredibly
> >difficult.
>
> Nit, ITYM "writing a non trivial program". Of course, the meaning of
> non trivial is a variable.
>
> >In contrast, analog computers don't have the same set of
> >scary failure modes -- they can fail, but not in the bizarre ways a
> >digital system can.
>
> No, they don't have the same set of scary and bizarre failure modes
> that a digital system has. They have their *own* set of scary and
> bizarre failure modes. I remember un fondly being at sea for a test
> of the hovering and missile compensation controller - when energized,
> it commanded all valves to the 'flood tanks' position and steadfastly
> insisted we were going *up*.
>
> Analog computers are more easily maintained than digital too, and a
> dammed good thing because they can need a lot of maintenance.
The calculus operations of differerentiation and integration
are fairly straightforward using capacitors, resistors, pots etc
in an analog computer, (V2 to ~ Mercury programs), but
components drift over time, temperature, wear etc and that
in turn requires periodic allignment/adjustment.
One good Analog to Digital Converter (ADC) solves alot of
problems. The software can select the analog input from
some source then read the data and store it for further
mathematical manipulation. The digital computer doesn't
need adjustment.
Also, the process is easily reversed by a DAC (Digital to
Analog Converter), so the computer can send an analog
signal when necessary.
I'm a technician (moonlights design* ;-), and the guy who
needs to calibrate the system (hung-over with an effective
IQ of 80) and needs to be kept simple and as maintenance
free as possible for field servicing.
> I much preferred troubleshooting relay based controllers though - the
> basic tools were a stethoscope and a rubber mallet.
Does Relay logic output much RF?
Regards
Ken
*Not meant as advertising, even though I'm poor, hungry
and low on work, my TV repair business is down.
David Lesher
>The environment under the hood of a car is incredibly hostile to
>electronics, both in temperature and vibration. It took a long time
>to get to digital components that could stand up to that sort of thing
>for the years at a time necessary for use in something like a car.
AND power-supply.... look up "load dump" sometime.
And one reason it took so long was Detroit tried to use ME's
to design EE projects. It was only in the 70's they started hiring
EE's.
They were forced to; smog+CAFE meant "closed loop" combustion, and despite
Detroit's efforts to make vacuum-hose based analog computer-controlled
carbs....... well.....
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
kevin willoughby
> The environment under the hood of a car is incredibly hostile to
> electronics, both in temperature and vibration.
Within the context of a discussion of Apollo computers, this is
laughable. Do you really think the temperature range of a New England
season matches the temperature extremes of a lunar flight? Do you know
just how violent the launch of a big rocket can be?
Apollo committed to computers in the early 1960s. Detroit was 2-3
decades behind that, despite the much less hostile environment.
(Admittedly, the Gremlin didn't have an Apollo budget...)
> It sounds to me like you might have been miseducated somewhat.
What's the correct education needed to compare spaceflight computers
with automobile travel computers?
kevin willoughby
> Thanks OM, I term that a "check-list" malfunction, what
> would be a better term?
I'm not OM, nor do I know the official vocabulary. But to my mind, the
hallmark of Apollo 13 isn't that it was a single malfunction, but a
multi-point malfunctions.
We engineers are supposed to be able to design systems that can survive
any single-point failure. With enough time, effort and smarts, any two
or three failures. But Apollo 13 was a long string of failures -- no one
or two or even three things explains what happened.
The Angry Alligator of Gemini was a multi point failure. One failure was
due to a guy who's wife had gone into labor -- he prioritized his wife
and child above some last-minute paperwork...
Three Mile Island is another example of a multi-point failure. Lots of
things went wrong. No one or two things can explain the full extent of
what happened at that reactor.
Probably the most extreme multi-point failure was the 9/11 attacks.
Entire books can (have!) been written on what went wrong. Most ignore
the fact that the World Trade Towers were nominally designed to accept
the impact of a big jetliner. There is precedent for this. Back in the
1940s, a big airplane (a Boeing-built 4-engine bomber) crashed into the
tallest building in Manhattan. The Empire State Building still stands,
half a century after that crash. It is pure speculation what would have
happened if the World Trade Towers were still standing, but I suspect
the world would be a different place.
Derek Lyons
>Fred J. McCall wrote:
>> The environment under the hood of a car is incredibly hostile to
>> electronics, both in temperature and vibration.
>
>Within the context of a discussion of Apollo computers, this is
>laughable. Do you really think the temperature range of a New England
>season matches the temperature extremes of a lunar flight? Do you know
>just how violent the launch of a big rocket can be?
Except we aren't talking about Apollo computers Kevin, the thread has
drifted somewhat.
>Apollo committed to computers in the early 1960s. Detroit was 2-3
>decades behind that, despite the much less hostile environment.
>(Admittedly, the Gremlin didn't have an Apollo budget...)
In some way the enviroment of an Apollo flight was more hostile. In
others, less. For example, even though a launch is violent it is over
in a few minutes, as opposed to a car which is expected to run for
hours. The Apollo computers only had to 100% reliable for a matter of
days, those in a car for months or years. Under normal operating
conditions, insulated inside the CM or LM ascent stage, the Apollo
computers neither got as hot as an Arizona July or as cold as a Maine
January.
And the Apollo computers didn't have to be cheap enough for the
average Joe to afford to replace one.
Jim Davis
> Back in the
> 1940s, a big airplane (a Boeing-built 4-engine bomber) crashed
> into the tallest building in Manhattan.
I believe that was actually a twin engined North American built
bomber, a B-25.
Jim Davis
Joe Pfeiffer
> Fred J. McCall wrote:
>> The environment under the hood of a car is incredibly hostile to
>> electronics, both in temperature and vibration.
>
> Within the context of a discussion of Apollo computers, this is
> laughable. Do you really think the temperature range of a New England
> season matches the temperature extremes of a lunar flight? Do you know
> just how violent the launch of a big rocket can be?
>
> Apollo committed to computers in the early 1960s. Detroit was 2-3
> decades behind that, despite the much less hostile
> environment. (Admittedly, the Gremlin didn't have an Apollo budget...)
A much less hostile environment (though far more hostile than, say, a
desktop computer), but requirements that it be mass produced cheaply and
that it keep working for a decade or so with virtually no maintenance,
In some ways an equally tough, or even tougher, requirement; though
completely orthogonal to environmental hostility.
>> It sounds to me like you might have been miseducated somewhat.
>
> What's the correct education needed to compare spaceflight computers
> with automobile travel computers?
Without the original post for reference, I think he was telling me I
might have been miseducated regarding the strengths of analog computers
in the 1970s (to which I didn't quite disagree; I said I expected a CS
education would be very different from an EE background in that
respect).
Steve Hix
kevin willoughby <kevinwi...@acm.org.invalid> wrote:
> Probably the most extreme multi-point failure was the 9/11 attacks.
> Entire books can (have!) been written on what went wrong. Most ignore
> the fact that the World Trade Towers were nominally designed to accept
> the impact of a big jetliner. There is precedent for this. Back in the
> 1940s, a big airplane (a Boeing-built 4-engine bomber) crashed into the
> tallest building in Manhattan. The Empire State Building still stands,
It was a B-25, not a B-17 or -29.
kevin willoughby
> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
>
> And the Apollo computers didn't have to be cheap enough for the
> average Joe to afford to replace one.
uh, yeah, I knew that. I said as much...
Fred J. McCall
:Fred J. McCall wrote:
:> The environment under the hood of a car is incredibly hostile to
:> electronics, both in temperature and vibration.
:
:Within the context of a discussion of Apollo computers, this is
:laughable. Do you really think the temperature range of a New England
:season matches the temperature extremes of a lunar flight? Do you know
:just how violent the launch of a big rocket can be?
:
The computers are kept in the environment controlled bit of the
Apollo. They don't hang them outside.
There is a difference between being able to BRIEFLY take quite violent
jolt and vibe and to take a much less extreme level of the two (plus
dirt) for YEARS without maintenance. The latter is actually harder.
:
:Apollo committed to computers in the early 1960s. Detroit was 2-3
:decades behind that, despite the much less hostile environment.
:(Admittedly, the Gremlin didn't have an Apollo budget...)
:
Apollo also had:
1) More actual space to put them in.
2) A controlled environment.
3) Preening to within an inch of its life.
:
:> It sounds to me like you might have been miseducated somewhat.
:
:What's the correct education needed to compare spaceflight computers
:with automobile travel computers?
:
Since that's not the actual issue, I'd suggest YOU might want to go
back to school to work on reading comprehension.
However, to answer your question, one would think that any engineering
discipline in the realm of electronics or computers would do.
One would hope that a practical engineering education would teach
something about manufacturability and maintainability coupled with the
difference between something that can weigh hundreds of kilos, is kept
in a conditioned environment and must only work for a month or so and
something that has to weigh a couple of orders of magnitude less than
that, is subject to everything from 30 degrees below zero to hundreds
of degrees above zero, and must function reliably with little to no
maintenance for years at a time.
kevin willoughby
> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
> :Fred J. McCall wrote:
> :> The environment under the hood of a car is incredibly hostile to
> :> electronics, both in temperature and vibration.
> :Within the context of a discussion of Apollo computers, this is
> :laughable. Do you really think the temperature range of a New England
> :season matches the temperature extremes of a lunar flight? Do you know
> :just how violent the launch of a big rocket can be?
> The computers are kept in the environment controlled bit of the
> Apollo. They don't hang them outside.
uh, no, not quite. The Saturn V IU was "hung on the outside" of the
controlled environment of the CSM. The computer in the LM was "outside"
for much of the flight -- it was "inside" only as the LM was warmed up
for human occupation. On Apollo 13, the CM computer was "outside".
> There is a difference between being able to BRIEFLY take quite violent
> jolt and vibe and to take a much less extreme level of the two (plus
> dirt) for YEARS without maintenance. The latter is actually harder.
Without quantifying how violent, how brief, how less extreme, this is
just hand-waving.
> :Apollo committed to computers in the early 1960s. Detroit was 2-3
> :decades behind that, despite the much less hostile environment.
> :(Admittedly, the Gremlin didn't have an Apollo budget...)
> Apollo also had:
>
> 1) More actual space to put them in.
Hardly. The engine bay in my car doesn't haven anywhere near enough
space for an Apollo computer.
> 2) A controlled environment.
Only in a pro-forma sense. Acceleration from zero to many gravities. Air
pressure from zero to a full atmosphere. Temperature from close to
absolute zero to full exposure to unfiltered sunlight.
> 3) Preening to within an inch of its life.
yep.
Fred J. McCall
:Fred J. McCall wrote:
:> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
:> :Fred J. McCall wrote:
:> :> The environment under the hood of a car is incredibly hostile to
:> :> electronics, both in temperature and vibration.
:> :Within the context of a discussion of Apollo computers, this is
:> :laughable. Do you really think the temperature range of a New England
:> :season matches the temperature extremes of a lunar flight? Do you know
:> :just how violent the launch of a big rocket can be?
:> The computers are kept in the environment controlled bit of the
:> Apollo. They don't hang them outside.
:
:uh, no, not quite. The Saturn V IU was "hung on the outside" of the
:controlled environment of the CSM. The computer in the LM was "outside"
:for much of the flight -- it was "inside" only as the LM was warmed up
:for human occupation. On Apollo 13, the CM computer was "outside".
:
An IU isn't a full 'computer'. Was the computer on the LM powered and
running out in the cold of space, or was it not? Was the CM computer
really 'outside' or was it environment conditioned?
:
:> There is a difference between being able to BRIEFLY take quite violent
:> jolt and vibe and to take a much less extreme level of the two (plus
:> dirt) for YEARS without maintenance. The latter is actually harder.
:
:Without quantifying how violent, how brief, how less extreme, this is
:just hand-waving.
:
We already know the two environments we're talking about.
:
:> :Apollo committed to computers in the early 1960s. Detroit was 2-3
:> :decades behind that, despite the much less hostile environment.
:> :(Admittedly, the Gremlin didn't have an Apollo budget...)
:> Apollo also had:
:>
:> 1) More actual space to put them in.
:
:Hardly. The engine bay in my car doesn't haven anywhere near enough
:space for an Apollo computer.
:
Now go back and read what I said. Glad to see you're in agreement,
although it was rather silly to start off with "Hardly", as if you
were disagreeing with my statement that the Apollo had more space to
put computers in than your typical Detroit product.
:
:> 2) A controlled environment.
:
:Only in a pro-forma sense. Acceleration from zero to many gravities.
:
Quite gently, as such things go. The acceleration is pretty benign.
The vibe environment sucks, particularly if you're using solids, but
it's of fairly short duration. Mere acceleration tolerance is easy.
Vibe and jolt are harder to deal with.
:
:Air pressure from zero to a full atmosphere.
:
Digital computers running exposed to vacuum? Cite?
:
:Temperature from close to
:absolute zero to full exposure to unfiltered sunlight.
:
Hogwash.
:
:> 3) Preening to within an inch of its life.
:
:yep.
--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn
Pat Flannery
kevin willoughby wrote:
> Fred J. McCall wrote:
>> There is a difference between being able to BRIEFLY take quite violent
>> jolt and vibe and to take a much less extreme level of the two (plus
>> dirt) for YEARS without maintenance. The latter is actually harder.
>
> Without quantifying how violent, how brief, how less extreme, this is
> just hand-waving.
The Soviets got around the vibration issue on Soyuz by using a big
honking block of a computer that relied on magnetic core memory for its
innate toughness: http://www.computer-museum.ru/english/argon16.htm
Pat
Fred J. McCall
:
:
:
And so did everyone else. It's not just the vibe issue (magnetic core
memory is probably MORE susceptible to vibe damage than SC memory),
but the rad issue. Magnetic core memory is pretty much rad hard from
the get go. SC memory is quite sensitive to it.
This is the same reason that IBM developed some REALLY tiny tubes for
space applications, even though ICs were available. Tubes are more
innately rad hard than SC components.
David Lesher
>One would hope that a practical engineering education would teach
>something about manufacturability and maintainability coupled with the
>difference between something that can weigh hundreds of kilos, is kept
>in a conditioned environment and must only work for a month or so and
>something that has to weigh a couple of orders of magnitude less than
>that, is subject to everything from 30 degrees below zero to hundreds
>of degrees above zero, and must function reliably with little to no
>maintenance for years at a time.
And have a per-unit cost 4 order of magnitude lower....
kevin willoughby
> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
> :uh, no, not quite. The Saturn V IU was "hung on the outside" of the
> :controlled environment of the CSM. The computer in the LM was "outside"
> :for much of the flight -- it was "inside" only as the LM was warmed up
> :for human occupation. On Apollo 13, the CM computer was "outside".
> :
>
> An IU isn't a full 'computer'.
Actually, it was. cording to
http://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit, it is a rare
example of a hybrid computer, both analog and digital.
Stages to Saturn says "Packed inside [the IU] were the computers....".
See
http://books.google.com/books?id=JnoZTbVLx0MC&pg=PA478&dq=apollo+instrument+unit+computer#PPA241,M1
> Was the computer on the LM powered and
> running out in the cold of space, or was it not?
Yes.
The entire LM was powered down until shortly before it was opened up for
the crew.
> Was the CM computer
> really 'outside' or was it environment conditioned?
That one was "inside", with the understanding that it wasn't a room
temperature during much of the Apollo 13 flight.
Greg D. Moore (Strider)
news:uoudnXnow90EiZ_X...@giganews.com...
It was also designed to operate at in a vacuum. This occurred more than
once on Apollo flights.
>
--
Greg Moore
Ask me about lily, an RPI based CMC.
Derek Lyons
>Fred J. McCall wrote:
>> An IU isn't a full 'computer'.
>
>Actually, it was. cording to
>http://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit, it is a rare
>example of a hybrid computer, both analog and digital.
>
>Stages to Saturn says "Packed inside [the IU] were the computers....".
>See
>http://books.google.com/books?id=JnoZTbVLx0MC&pg=PA478&dq=apollo+instrument+unit+computer#PPA241,M1
And, while the IU electronics were 'outside' in the sense they weren't
in something like the crew compartment - they were inside the struture
of the IU itself and enviromentally controlled.
>> Was the computer on the LM powered and
>> running out in the cold of space, or was it not?
>
>Yes.
>The entire LM was powered down until shortly before it was opened up for
>the crew.
True. But the stack was in PTC, and the computer was inside an
insulated compartment.
>> Was the CM computer
>> really 'outside' or was it environment conditioned?
>
>That one was "inside", with the understanding that it wasn't a room
>temperature during much of the Apollo 13 flight.
No, they weren't at room temperature... But the inside of the CM was
only a little below freezing.
Joe Pfeiffer
> Fred J. McCall wrote:
>> kevin willoughby <kevinwi...@acm.org.invalid> wrote:
>> :uh, no, not quite. The Saturn V IU was "hung on the outside" of the
>> :controlled environment of the CSM. The computer in the LM was
>> "outside" :for much of the flight -- it was "inside" only as the LM
>> was warmed up :for human occupation. On Apollo 13, the CM computer
>> was "outside".
>> :
>>
>> An IU isn't a full 'computer'.
>
> Actually, it was. cording to
> http://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit, it is a rare
> example of a hybrid computer, both analog and digital.
Interesting! Lots of detail there I hadn't come across before.
Fred J. McCall
:
It also wasn't running during much of the Apollo 13 flight.
Derek Lyons
>Fred J. McCall wrote:
>
>> An IU isn't a full 'computer'.
>
>Actually, it was.
The IU ia no more 'a' computer than the CM was. The IU was a section
of the vehicle that contained (among many other things) computers.
>cording to http://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit,
>it is a rare example of a hybrid computer, both analog and digital.
Nope. The IU contained a digital computer (the LVDC) and an analog
computer (the flight control computer). (See page 149 of
http://history.nasa.gov/ap12fj/pdf/sa507-flightmanual.pdf.) A third
unit (the LVDA) performed A/D and D/A conversions and served as an
interface and buffer unit between the LVDC and the remainder of the IU
systems.
Andre Lieven
> kevin willoughby <kevinwilloug...@acm.org.invalid> writes:
> > Fred J. McCall wrote:
> >> :uh, no, not quite. The Saturn V IU was "hung on the outside" of the
> >> :controlled environment of the CSM. The computer in the LM was
> >> "outside" :for much of the flight -- it was "inside" only as the LM
> >> was warmed up :for human occupation. On Apollo 13, the CM computer
> >> was "outside".
> >> :
>
> >> An IU isn't a full 'computer'.
>
> > Actually, it was. cording to
> >http://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit, it is a rare
> > example of a hybrid computer, both analog and digital.
>
> Interesting! Lots of detail there I hadn't come across before.
Including a PDF link for Stages To Saturn that isn't working... :-(
(I have a trade paper copy of the book, anyway, but a copy for the
computer is always a good thing)
Andre
kevin willoughby
> And, while the IU electronics were 'outside' in the sense they weren't
> in something like the crew compartment - they were inside the struture
> of the IU itself and enviromentally controlled.
This is the first I've heard that the IU had environmental control.
References?
Derek Lyons
>Derek Lyons wrote:
>
>> And, while the IU electronics were 'outside' in the sense they weren't
>> in something like the crew compartment - they were inside the struture
>> of the IU itself and enviromentally controlled.
>
>This is the first I've heard that the IU had environmental control.
It wasn't the IU that was enviromentally controlled, it was the IU
electronics - the boxes.
Ken S. Tucker
> kevin willoughby <kevinwilloug...@acm.org.invalid> wrote:
> >Fred J. McCall wrote:
>
> >> An IU isn't a full 'computer'.
>
> >Actually, it was.
>
> The IU ia no more 'a' computer than the CM was. The IU was a section
> of the vehicle that contained (among many other things) computers.
>
> >it is a rare example of a hybrid computer, both analog and digital.
>
> Nope. The IU contained a digital computer (the LVDC) and an analog
> unit (the LVDA) performed A/D and D/A conversions and served as an
> interface and buffer unit between the LVDC and the remainder of the IU
> systems.
> D.
This site has a nice readable overview,
http://www.apollosaturn.com/ascom/s5news/p71-7.htm
Herein the computer is well described,
http://en.wikipedia.org/wiki/Saturn_Launch_Vehicle_Digital_Computer
Ken
Pat Flannery
Ken S. Tucker wrote:
> This site has a nice readable overview,
> http://www.apollosaturn.com/ascom/s5news/p71-7.htm
>
> Herein the computer is well described,
> http://en.wikipedia.org/wiki/Saturn_Launch_Vehicle_Digital_Computer
>
Here's a couple of drawings of one, showing all the components:
http://mix.msfc.nasa.gov/IMAGES/MEDIUM/0100984.jpg
http://mix.msfc.nasa.gov/IMAGES/MEDIUM/0100806.jpg
This page shows different details:
http://apollomaniacs.web.infoseek.co.jp/apollo/sv_iue.htm
(The STR-124 platform doesn't seem to be housed in a sphere anymore, or
its air supply sphere is missing)
Pat