A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Space Science Misc
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

earliest moon landing



 
 
Thread Tools Display Modes
  #21  
Old December 22nd 04, 03:07 AM
Derek Lyons
external usenet poster
 
Posts: n/a
Default

Pat Flannery wrote:
Derek Lyons wrote:

Nonsense. If you allow for testing/tweaking time in your
manufacturing schedule and budget, it doesn't matter if you are making
10 motors or 10,000.


Do you think you are going to have more man hours in five big motors and
their plumbing or thirty medium sized ones? More man hours mean more
possibility for mistakes. All of our manned moon landings (Apollos 11, 12,
14, 15, 16, 17) used the same number of F-1 motors as the number of NK-15's
used in one N-1 first stage. If you have forever to make them, you can take time
on each of the motors and check it out...


No, you simply have multiple checkout and assembly pipelines running
in parallel.

but the 14 N-1's the soviets had finished or in construction meant they needed 420
motors for the first stages, and an additional 112 modified NK-15s for the second
stages. That's 532 motors total, and that is a _lot_ to build and inspect.


Not particularly. During WWII air craft engine manufacturers
routinely turned out 10-12 motors a day from a single factory. The
Russians knew about assembly lines Pat.

One thing that indicates the degree of confidence that the Soviets had
in the N-1 was that they wanted a dozen successful unmanned launches
before they were going to put a crew on it.


Right. As compared to every US manned booster, with the exception of
the Saturn V and the Shuttle, which had that many or more. Don't
confuse prudence with a lack of confidence.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

  #22  
Old December 22nd 04, 01:30 PM
Heinrich Zinndorf-Linker (zili@home)
external usenet poster
 
Posts: n/a
Default

Am Tue, 21 Dec 2004 14:55:14 -0600 schrieb "Pat Flannery":

But assuming that the motors have an equal potential for catastrophic
failure, the more motors you put on the vehicle, the more likely it is
that one will catastrophically fail. Because of its large size, the F-1
probably had a greater potential for catastrophic failure than a NK-15,
like the N-1's first stage used, but to get equal reliability in the
overall booster stage, the NK-15 would have to be _six times_ as
reliable as a F-1 in this respect...and I don't think that that was the
case.
[...other conclusions snipped...]


I agree totally. And I see a very parallel development in computer
technology that is the business of many writers here. See RAID
systems: You can increase their reliability by using redundant amounts
of hard disks for building arrays that have the capability to survive
single or sometimes even multi disk failures. E.g. a raid-5 array of
three disks survives the crash of one disk. But with increasing
numbers of disks the probability of single failures itself increases
(multiplies by number of used disks), too. So, at some point,
increasing numbers of disks in hard disk arrays begins to reduce
over-all reliability of the total array. That is a known fact - and
btw: one main factor for that decrease in overall reliability is the
increased complexity of "plumbing". (:-) The parallels are obvious.
And so is the actual trend of using as few as possible disks for
getting the necessary storage capacity.

cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker)
--
"Abusus non tollit usum" - Latin: Abuse is no argument against proper use.

mailto: http://zili.de

  #23  
Old December 22nd 04, 07:46 PM
external usenet poster
 
Posts: n/a
Default

Let see...

- Kerosene engines

- Small maneuvering engines

- Something to calculate the orbital maneuvers

And so on.


Personally, I think that technologies probably already existed in the
1930's, and perharps even before it. By the 1940's, nuclear engines
probably is much prefered than kerosene engines, just like in Herge's
"Objectif Lune" (which I suspect was done with help from outside
sources, it's just too detailed for a comic book).


Though it should be noted that there were ancient batteries and ancient
clocwork type devices already existed thousands of years ago, so it
could have happened thousands of years ago.

  #26  
Old December 23rd 04, 08:58 AM
Pat Flannery
external usenet poster
 
Posts: n/a
Default

Derek Lyons wrote:

Certainly. But we weren't talking about saving money, but about
producing motors, especially large ones, in significant quantities on
a schedule. However Pat dismissed even the possibility of such a
program for the N-1 out of hand, which is incorrect and what I was
adressing.


I didn't say it was impossible to do, just that is was going to be damn
hard to do, and that it would be difficult to give each motor a decent
check-out before shipping it off the the launch site. I don't know haw
many man-hours went into each motor's construction, but it was a fairly
sophisticated design that had a better ISP than the F-1, and it sounds
like a lot of floor space and people would be needed to build them in
the numbers needed for large-scale use of the rocket.
The original plan was for variants of the N-1 using its stages in
various configurations were going to become the standard Soviet medium
and heavy lift rocket systems- there was even a ICBM variant proposed:
http://www.astronautix.com/lvs/n11gr.htm

(Pat and I were also discussing tweaking/tuning in the
name of building safe, reliable motors. Cost is somewhat less of an
issue in that instance.)


I'd be more concerned about the production rate than the cost per motor.

Pat

  #27  
Old December 24th 04, 04:25 AM
Herb Schaltegger
external usenet poster
 
Posts: n/a
Default

In article ,
Pat Flannery wrote:

Manufacturing problems can easily happen when you
have a very small, limited production run, which means that your need for
"strenuous tests" is likely higher with a small run as compared to a very
large run, where repeatability in the manufacturing processes has already
been achieved.

In the perfect world, yes...but in the real world every one of those
motors is going to be at least a bit different from its sisters due to
it's complexity, and when you are dealing with hundreds of them turned
out in a fairly short period of time, at least one is going to be
different in a fatal way.


I missed this in Jeff's post - I was distracted and not reading
closely, unfortunately.

In any event Pat's point is well-taken, especially given the Soviet
production standards of the day. Jeff states "where repeatability in
the manufacturing process has already been achieved." Personally, I
think it's a big and unwarranted assumption to state or even imply
that a large production run indicates that repeatability has been
achieved. A large production run, in and of itself, means nothing.
If your qualification testing program is valid, and ONLY IF, you can
presume the various widgets you're manufacturing are fungible (rather
than frangible, as the N-1 engines turned out to be . . . ;-)
Otherwise you're just turning out mass quantities of stuff with no
guarantees that s/n 1 is at all similar to s/n 50 or 500. You need
strict control of your manufacturing process, from beginning to end,
in order to ensure that those units are in fact similar enough to
count on behaving similarly. It gets back to the age-old design
engineering debate: do you qualify for flight by test? (e.g., hotfire
each engine, etc) or by analysis (e.g., very limited testing combined
with documentation demonstrating repeatability and consistency in
manufacturing?) Obviously, for the state of the Soviet art at the
time, the N-1's designers picked the wrong approach for the entire
vehicle.

--
Herb Schaltegger, B.S., J.D.
"Wow! This is like saying when engineers get involved, harmonic
oscillations tear apart bridges."
~Hop David
http://www.angryherb.net

  #28  
Old December 24th 04, 08:36 AM
Pat Flannery
external usenet poster
 
Posts: n/a
Default

Herb Schaltegger wrote:


If your qualification testing program is valid, and ONLY IF, you can
presume the various widgets you're manufacturing are fungible (rather
than frangible, as the N-1 engines turned out to be . . . ;-)


There was only three motor malfunctions that could be possibly
attributed to a fault in the motor itself- on the first flight, a motor
developed a high frequency oscillation from bits of metal that got into
the turbopump, and this caused it to rip free from its propellant
plumbing. On the second flight, one of the motors ingested a temperature
sensor, bolt, or piece of welding slag (stories vary) from inside the
Lox tank and exploded, damaging the other motors in its vicinity and
causing the KORD system to shut all the motors down. On the fourth
flight what went wrong depends on who's telling the story- from the
engine builder's viewpoint what went wrong was that a too rapid shutdown
of the center six motors caused a water-hammer effect to rupture their
plumbing. From the rocket designer's viewpoint another turbopump had
exploded in one of the center six motors (Turbopump overspeed due to
propellant cut-off?).



Otherwise you're just turning out mass quantities of stuff with no
guarantees that s/n 1 is at all similar to s/n 50 or 500.


And when you need 30 motors per first stage of each individual N-1
rocket, you are turning out large numbers of motors that you can't be
sure of until the first launch is attempted and then you get a few
successful launches under your belt. How would you like to be looking at
a room with a hundred or so NK-15 motors sitting in it, and be trying to
figure out if the turbopumps have an inherent problem in their design,
or if simply sticking filter screens on the propellant feed lines will
fix the problem? You'd better hope the latter will be the case, as if it
is a design problem on the motor you're going to have to explain to the
Kremlin that all those motors are going to need major modifications or
be simply scrapped....and you may find yourself living in a tiny
Siberian yurt made out of a scrapped NK-15 motor.
The motor was made by the Kuznetsov Design Bureau BTW....the design
bureau had plenty of experience in building gas turbine motors for
aircraft, but had almost no experience with liquid-fueled rocket motors
when the N-1 got dropped into its lap. So that was another thing that
the design of the N-1 had going in its favor.

You need
strict control of your manufacturing process, from beginning to end,
in order to ensure that those units are in fact similar enough to
count on behaving similarly. It gets back to the age-old design
engineering debate: do you qualify for flight by test? (e.g., hotfire
each engine, etc) or by analysis (e.g., very limited testing combined
with documentation demonstrating repeatability and consistency in
manufacturing?) Obviously, for the state of the Soviet art at the
time, the N-1's designers picked the wrong approach for the entire
vehicle.


That pretty well sums it up; as one of the designers said about it: "How
do you explain to your government that you have a rocket that weighs
more than a Saturn V, develops more thrust than a Saturn V, and yet can
carry far less to the Moon than a Saturn V?"
I imagine that after each of the four failures, that became a little
harder to do.

Pat

  #29  
Old December 27th 04, 07:29 PM
Derek Lyons
external usenet poster
 
Posts: n/a
Default

Pat Flannery wrote:
And when you need 30 motors per first stage of each individual N-1
rocket, you are turning out large numbers of motors that you can't be
sure of until the first launch is attempted and then you get a few
successful launches under your belt.


sigh Pat... You keep repeating this as fact, and it is not.

It is possible, nay fairly straightforward, to produce a large number
of motors *and* to be sure of their performance. That the Russians
screwed it up by making the wrong choices doesn't change this.

How would you like to be looking at a room with a hundred or so
NK-15 motors sitting in it, and be trying to figure out if the turbopumps
have an inherent problem in their design, or if simply sticking filter
screens on the propellant feed lines will fix the problem?


Problems easily resolved with a proper design, qualification, and
production process. That the Russians chose not to follow this well
trodden path is no indication that the job is impossible.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

  #30  
Old December 27th 04, 07:34 PM
Derek Lyons
external usenet poster
 
Posts: n/a
Default

Pat Flannery wrote:
I didn't say it was impossible to do, just that is was going to be damn
hard to do, and that it would be difficult to give each motor a decent
check-out before shipping it off the the launch site.


It's not difficult at all. It's a straightforward matter to schedule
your production start early enough and to provide enough test stands.

(Pat and I were also discussing tweaking/tuning in the
name of building safe, reliable motors. Cost is somewhat less of an
issue in that instance.)


I'd be more concerned about the production rate than the cost per motor.


Again, not an issue. Start your production early enough with one
line, then 'twin' it (I.E. move experienced workers from the first
line to the second, then filling both with less experienced). Repeat
as needed. (Or start a bunch of lines at once and be prepared to
scrap a lot of early motors.)

It's all about proper management and having enough resources, and the
Russians chose (for various reasons) not to apply themselves to the
task.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
The Apollo Hoax FAQ (is not spam) :-) Nathan Jones UK Astronomy 8 August 1st 04 09:08 PM
The Apollo Hoax FAQ (is not spam) :-) Nathan Jones Astronomy Misc 5 July 29th 04 06:14 AM
The Apollo Hoax FAQ darla Misc 10 July 25th 04 02:57 PM
The Apollo Hoax FAQ darla UK Astronomy 11 July 25th 04 02:57 PM
The Apollo Hoax FAQ Nathan Jones Astronomy Misc 5 November 7th 03 09:53 PM


All times are GMT +1. The time now is 01:17 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.