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#26 2014-12-06 07:44:07

Terraformer
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From: Ceres
Registered: 2007-08-27
Posts: 3,526
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Re: Habitat air

Then again, Robert, *you* have been continually claiming that fire is not a problem in high O2 atmosphere, when it is known that fire depends on O2% rather than partial pressure, and you've also ignored the ability of humans to adapt to CO2...


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#27 2014-12-06 10:41:39

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
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Re: Habitat air

I don't exactly know what "145 to 220 fsw" means,  "fsw" being jargon for something.  But,  I'm guessing it means "feet of sea water" since the research had to do with deep sea diving.  Call it a good educated guess. 

Assuming it's feet of sea water,  145 ft submergence at sp gr gravity = 1.025 leads to a gage pressure of 64.2 psig,  and a total or absolute pressure of 78.9 psia.  Ratioed (absolute not gage pressures!) to surface conditions gives a minimum decompression total pressure ratio of 5.368:1.  Lumping all the inert gases together at 79.1%,  the r to surface total pressure is 4.25,  way above the recommended pre-breathe r limit of 1.2 for nitrogen.  OF COURSE the rats got the bends.  How could they not?

If we assume a 1 atm habitat pressure,  that same overall pressure ratio would be talking about a 2.74 psi oxygen suit.  I don't think we're really talking about going that low in suit pressure,  but some of us would like to use 3 psia O2.  But use it (2.74 psia) anyway.  Pp N2 in the hab is 11.62 psia.  The r to the total pressure in the suit would be the same 4.25.  OF COURSE the astronaut would get the bends if he didn't do some nitrogen blow-off time! 

That's part of why "they" want an 8 or 9 psi suit at NASA.  For that,  r = 11.62 Pp N2/9 psi suit O2 = 1.29,  which is still a bit on the high side.  You still need at least several minutes of blow-off time,  you can't just don,  seal,  and go straight out the airlock at low O2 suit pressure. 

The REAL question here is how fast can we safely blow off the inert mixture vs straight nitrogen? 

If the hab atm is 20.9% O2 and 79.1% N2,  the effective dissolved Pp of N2 in the blood is only a little less than that in the hab atm at 11.62 psi.  If on the other hand you used a 3-inert-gas mix at equal parts,  each individual gas's effective dissolved Pp in the blood is now 33% of the straight N2 value,  or 3.87 psi each,  although their total is still 11.62 psi. 

Diffusion physics says the driving force for diffusion rates is the difference in Pp's,  which in the suit would be 0's for the inerts.  The risk of smooth outgassing vs fizzing (bubble formation) I believe would be driven by higher Pp differences,  less at lower values.  Those differences for the individual gases are lower with the mix than it is with the single inert gas.  Now,  other interactions may intervene,  to make the total Pp difference of the mix more important to bubble formation than the Pp difference of each gas individually.  That would be the point of re-running the experiments. 

It's just that we do it on the low side of 1 atm,  when they were done on the high side of 1 atm before,  and it's not necessarily the same.  Assuming it is the same is a bad idea.  That's why "assume" is spelled the way it is,  because of what it makes out of "u" and "me".   

The cited article was unclear about that.  For the high-side-of-1 atm experiments,  they saw some differences in the gases,  but not enough to really do anything but lump them together.  NOBODY KNOWS the interactions on the low side of 1 atm.  That's what we're arguing about here. 

And THAT is why I recommended re-running the experiments at pressures from 1 atm down.  Find out for sure what really works and what does not.  It would be cheap and easy to do so. 

GW

Last edited by GW Johnson (2014-12-06 10:50:36)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#28 2014-12-06 11:50:38

SpaceNut
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#29 2014-12-06 12:47:33

Impaler
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From: South Hill, Virginia
Registered: 2012-05-14
Posts: 286

Re: Habitat air

GW Johnson wrote:

I don't exactly know what "145 to 220 fsw" means,  "fsw" being jargon for something.  But,  I'm guessing it means "feet of sea water" since the research had to do with deep sea diving.  Call it a good educated guess.

Your guess here is correct, but this is the kind of thing 1 minute goggling will answer so you don't HAVE to guess.

GW Johnson wrote:

Diffusion physics says the driving force for diffusion rates is the difference in Pp's,  which in the suit would be 0's for the inerts.  The risk of smooth outgassing vs fizzing (bubble formation) I believe would be driven by higher Pp differences,  less at lower values.  Those differences for the individual gases are lower with the mix than it is with the single inert gas.  Now,  other interactions may intervene,  to make the total Pp difference of the mix more important to bubble formation than the Pp difference of each gas individually.  That would be the point of re-running the experiments.

In the absence of ANY evidence you would assume interaction between the gasses as we would understand the physical reaction happening is one in which each gas is trying to enter every bubble and the flow across the membranes combine to inflate the bubbles.  If you actually think about what is physically happening then the interaction is obvious.

The assumption your making is like saying that if I know that a flammable gas is only explosive above 10% concentration in air, and another is only explosive above 13% and another above 15% then it will be possible to mix all of them together and get mix which is 10+13+15= 38% fuel and it will be non-explosive because each 'individual' gas is safe.  The reasonable hypothesis is full-interaction, not the absence of interaction.

The earlier rat experiments are indeed being severely decompressed from the 4-6 atmosphere to 1 atmosphere range, the severity of decompression symptoms included death and were obviously not going to be doing that to people, the point of the experiment was to induce a strong decompression response so the different gas effects could clearly be elicited by gross physical differences like death/non-death.  The result clearly said worse symptoms with Argon or Ar/N2 mix vs pure N2.  If you no longer believe that decompression symptoms at one pressure ratio can be extrapolated across different pressures with the same ratio then your throwing away the very concept of the Bends ratio which is what you based your earlier work on.

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#30 2014-12-06 13:39:26

RobertDyck
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From: Winnipeg, Canada
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Posts: 7,253
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Re: Habitat air

Terraformer, there is the table and figures from the paper Impaler linked. Everything I found before this indicated flammability was directly proportional to partial pressure oxygen. Fire fighters found water significantly reduced flammability, primarilly because simply spraying water in the air reduced air temperature. So for a hot fire, they don't just dose the fuel, they spray water in the air. And it intereferes with fire. But this paper provides more data. Very useful, if presented dispassionately.

::Edit:: Link to the paper http://ntrs.nasa.gov/archive/nasa/casi. … 005041.pdf
FlammabilityTable.png
FlammabilityFigure1.png
FlammabilityFigure2.png
Notice the lines in Figure 1. They are not flat. Flammability is not directly proportional to percent oxygen. Also note the test doesn't go below 7.0 psi pressure. We have to interpolate. Apollo used 5.0 psi total pressure. I had recommended 8.433 psi with a tri-gas mix, but if that doesn't work for zero prebreathe, then 2.7 psi O2 + 3.6 psi N2 = 6.3 psi total. That's still below the data presented, so we still have to interpolate.

Also realize this data measures self-extinguishing. That means turning the air you breathe into a fire extinguisher. On Earth we live the fact many materials will burn, we just don't ignite them. Wood for example is not self-extinguishing in Earth ambient atmosphere.

And which materials do you have to worry about? I recommended PCTFE for the greenhouse envelope, sold by Honeywell under brand name Clarus, and until 1995 sold by 3M under brand name Kel-F. The exterior of spacesuits is Orthofabric, which is a double layer fabric with Goretex facing. Goretex is PTFE. The air bladder of a spacesuit is neoprene; but that's the suit, not spacecraft interior.

This table doesn't give ignition temperature for neoprene. What is the ignition temperture for neoprene at spacesuit pressure? Considering what I'm talking about for suit pressure is about the same as an Apollo suit, I don't remember fire starting in any spacesuit. The Apollo 1 fire, yes, which started in the capsule at 17.8 psi pure oxygen. Not in a suit while performing an EVA in space.

So interpolating using data for 7.0 psia and 12.35 psia:
At 6.3 psia, Kel-F aka PCTFE for the greenhouse would require 78.6% O2 to sustain a flame. Less oxygen than that is self-extinguishing.
At 6.3 psia, PTFE aka Goretex for a spacesuit would require 53.9% O2 to sustain a flame.

According to Material Safety Data Sheet from Icrorally, PTFE autoignition temperature in Earth atmosphere is 520-560°C.
According to MSDS from 3M, Neoprene autoignition temperature is 404°C.
According to MSDS from Honeywell, PCTFE autoignition temperature is not defined. One reason it isn't defined is it's so incredibly difficult to burn. Considering PCTFE is more chemically stable than PTFE, it's autoignition temperature would be higher. And PTFE autoignition temperature is higher than PCTFE melting or decomposition temperatures.
PCTFE will melt at 220°C, which will decompress the greenhouse to Mars ambient, flood it with Mars 95+% CO2. So it can't burn.

Last edited by RobertDyck (2014-12-06 22:49:02)

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#31 2014-12-06 17:10:41

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
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Re: Habitat air

I'm an OLD guy.  By the standards of most participants on these forums,  I'm a REALLY OLD guy.  I designed my first airplane,  and my first half dozen supersonic missiles,  with a slide rule,  back in the 1970 time frame.  If any of you know what one of THOSE is.  For 300 years previous,  the slide rule WAS our calculator. 

It's what we designed the Saturn 1 and Saturn 5 with (and their engines),  and what we designed the Apollo hardware with (and its engines),  by the way.  As well as the X-15 and the SR-71 and the B-70 and the F-100 (and their engines). 

By the time of ASALM-PTV,  I was using a calculator to do what I formerly did with a slide rule.  Think Mach 6 on airbreathing propulsion (NOT SCRAMJET!!!!!).  We set that record BY ACCIDENT in 1980 with an ASALM flight test,  and it stood until 2004.  Very little of that effort had anything to do with computers (by which I mean mainframes,  there were NO desktops in those days). 

Because of that history and my age,  I will never be comfortable "googling" things first.  My comfort zone was,  is,  and always will be,  hardcopy paper.  Sorry,  at my age,  that ain't gonna change.  Period.  You guys gotta make the difference there.

I see by the curves in the previous post that there really is a significant effect of partial pressure Pp on flammability,  it's NOT JUST all % oxygen.  Hard to argue with real data,  ain't it?  Real life is a bitch,  most of the time.  But the slopes of those curves are low,  so it really is MOSTLY % O2.  Just not ALL % O2. 

Once again,  the "bends" experiments were run at P's > 1 atm.  NO experiments were run at P's < 1 atm.  "ASSUME" is spelled the way it is because it makes an "ASS" out of "U" and "ME".  Dare trust nothing,  as Hercule Poirot would say.  So,  run the damned experiments at P < 1 atm.  Find out "for sure".  Quit extrapolating.  That will eventually kill people. 

And THAT is why the X-15 and the SR-71 and the Saturn-1 and the Saturn-5 and the F-100 and the B-70 were as successful as they were.  We simply went and found out what we needed to know.  We did whatever it took to find out.  We did not ASSUME we knew anything at those conditions.  Extrapolating outside your database is nearly always fatal.  THAT's our history. 


GW

Last edited by GW Johnson (2014-12-06 17:16:50)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#32 2014-12-06 23:41:59

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,253
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Re: Habitat air

I'm getting up there myself. I watched the space race from Mercury through Apollo 11 as a pre-schooler; I wanted to be an aerospace engineer. But that just couldn't happen, there was no aerospace engineering where I grew up.

There was no advanced learning program, and my efforts to get ahead so I could skip a grade in elementary school just resulted them putting me in remedial class. I did even worse there. The remedial teacher wanted me transferred into a special school for learning disabled, although my other teachers disagreed. My mother took me to student services at the school division office; they tested my IQ. I got 133 on average, but higher in math and science, and poor in English. They transferred me into regular class. In junior high they tested aptitude; I got 95 percentile in math, which is on a scale of 0 to 99. In logic, pattern matching, and spatial relations I got 99; there isn't anything higher. And my scores in spelling, grammar, and English composition sucked (um, 40). The teacher said it was the clearest result they ever saw, I should go into engineering or computer science. There was no aerospace engineering in my province, and my parents couldn't afford to send me out of province for university, so I took computer science.

In high school, as well as first and second year university, we still used punched cards. The first personal computers came out; they had 4 kilobytes of memory, and an audio cassette for storage. I remember dreaming of a computer you could put on a student desk, about the size of a 3-ring binder, with the hinge away from you so you could open it up, with the display on the inside cover, and the keyboard on the bottom cover. And a word processing program that lets you type, with a spelling checker. This was in grade 11 computer class in 1978/79, my fellow students said I was crazy. Today they're called "laptop computers". My mother was an accountant, but her employer asked her to form that company's first computer department. I read one of the books she brought home, about something called a database. My best friend and I competed for top grades in computer science; he got 93% while I only got 92%. That was still an A+, but only second highest for the class. But the other students came to me because I helped them when they got stuck on an assignment, but did so without trying to take-over, not doing their work for them, just pointing out their problem and how to resolve it.

I did get a full-time job as a computer programmer half way through first year university. Only paid minimum wage, but it was the sort of work a recent graduate would do. One day the boss said there wasn't any database management system for personal computers yet, so write one. So I did. Our customers ran small business with an 8-bit computers running at 4 MHz, 60 kB of memory, and a pair of 5.25" floppy disk drives holding 1.0 MB each, and no hard drive. We didn't have a compiler, so I had to hand code subroutines in machine language. We didn't have an assembler either, so I had to hand code the numeric OP codes. Just to get them to run fast enough for business use. And one day a customer came to us with a magazine that had pictures of a new computer called an Apple Lisa. It was way too expensive for them; they wanted their current computer to do that. The Lisa was the predecessor to the Macintosh. So I had to figure out on my own how to write event driven graphical programming, and write it from scratch with nothing but pictures from a magazine. And the 8-bit computers we had ran the CP/M operating system, the one before MS-DOS 1.0. It didn't have a graphics display adapter, only character graphics. So I had to use corner and line characters to draw borders around the windows, and use only keyboard because these computers didn't have a mouse.

When I was in high school in the late 1970s, we talked about installing network. It would be a global network, with vast amounts of information available. A computer in every house. Most adults at the time scoffed: "Why would you want a computer in the house?" Government labs at the time had something called Arpanet; it would be based on that. And I remember being invited to come back to my alma matter in 1990 for a presentation about a new thing called the Internet. A text based network using a new protocol called TCP/IP, with a search engine called Archie. There was talk about a new search engine called Veronica, but that one didn't contain much content yet. The university was making this available to the public; it required a dial-up modem to access. There were rumours of someone working on a graphical user interface, something they called the World Wide Web, but the graphics were so large that it wasn't practical to use unless you had a high speed connection. You could get a T1 connection at 1.2 million bits per second, but it cost $1,000 per month. So no one in my province had even seen it.

Yea, I have heard engineers talk of the dangers of extrapolating outside the database. That was the warning that ATK engineers gave to NASA prior to launching Challenger. Outdoors temperature was outside the database. They advised to not launch. But apparently NASA managers didn't understand that.

So yea, that's part of my point. Thank you for emphasizing it. We do need to test in conditions we will actually operate. For flammability, NASA did test the air they used for the Apollo capsule after the Apollo 1 fire and before launching. That's my point: this paper does not cover that condition. But Apollo and Skylab did work. And one test they did on Skylab was to burn a candle. It burned quite differently in zero-G; no convection. But that didn't set Skylab on fire.

The first candle test was conducted on Skylab in 1974. They first tested it on the ground in a chamber with the same atmosphere as Skylab. Interesting, this book gives a bit more detail. It says Skylab used 65% oxygen at 35.8 kPa (5.2 psia).
http://books.google.ca/books?id=ZwD8uTp … 74&f=false

And yes, we need to test decompression for the exact environment we are talking about. Not extrapolating outside the database. Thank you for reminding me (and us) of that.

Last edited by RobertDyck (2014-12-07 05:00:43)

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#33 2014-12-07 10:46:42

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 25,719

Re: Habitat air

I have just read my very simular educational back ground and experience in you post RobertDyck. I also remember vaccumn tubes, Transistors, DTL logic, paper tape readers, 8 in single mode floppy's.....PDP-11 flip switch input computers, the 8088 trainer kit, computer programs  of basic, cobalt, pascal, and being in design labs do the CD rom burner....

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#34 2014-12-07 16:01:42

GW Johnson
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From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
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Re: Habitat air

Transistors appeared commercially during my teen years.  My pre-teen years were spent pedalling to the corner store with TV vacuum tubes to test in their tube tester.  Does anybody remember those things?  We had a black-and-white Dumont vacuum-tube TV from 1952.  Refrigerator-sized cabinet with a 12-inch screen.  It had an unshielded Klystron tube in its power supply.  If you sat too close,  you could absorb a lifetime's dose of X-ray in about an hour.  Of course,  nobody knew that back then. 

My experiences with computers were entirely different from that described by Robert Dyck.  There was nothing like that available in my high school.  The vocational electronics guys were doing vacuum tube TV stuff.  Radio was similar in those days.  I went physical stuff,  not electronics. 

When I got to undergrad engineering school in college,  there were card batch input mainframes with fan-fold printed output,  or teletype interfaces with fan-fold printed output.  There were no pocket calculators of any kind,  only the same slide rules I used in high school.  We avoided using the mainframe like the plague,  whenever possible. 

I learned how to program in college in Fortran II,  but never learned any "job control language" (what today we would call an operating system),  because that stuff was machine-specific,  and thus simply wasn't taught.  That lack still cripples me today. 

In industry,  I became really adept at programming in Fortran IV,  and later one of the advanced BASIC's,  called QuickBASIC,  which actually resembles the Fortran 77 I never learned.  I know absolutely nothing of the modern languages,  although I learned how to do very structured programming in Fortran IV and in QuickBASIC.  But,  there are some problems that simply require "spaghetti code",  such as balancing a ramjet engine. 

You cannot write "spaghetti code" in the modern languages,  I do know that about them.  So I already know that my QuickBASIC ramjet cycle analyses cannot ever be translated to modern languages!

Believe it or not,  I still have a way to program and operate in QuickBASIC,  thanks to my son,  for whom modern desktop operating systems are quite transparent.  I am still doing ramjet stuff in that environment,  even today,  and for real clients.  The hardest part was figuring out how to print out from such dead languages  when there is no such thing as a parallel-port printer anymore.  My son solved that problem.  I can do it now. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#35 2014-12-07 16:57:53

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,253
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Re: Habitat air

What you described in college, I used in high school. I did take tubes from our TV to the tube tester at the convenience store. Pocket calculators came out while I was in junior high. The personal computer at my first job used BASIC, but it was an interpreter, not a compiler. That's why I had to write subroutines in machine language to speed up certain features.

I took computer science in university. You can write anything without spaghetti code; you just have to know how. I've written in: BASIC (MBASIC, Business BASIC), Fortran (WatFor extended, and WatFiv), COBOL, Pascal, Delphi, PL/1, APL, Ada, C, C++, Visual C++, Visual Basic, VBA, HTML, Java, Java Script / CGI / Perl, and machine languages for IBM mainframes, VAX, 1802, 6800/6802/6805. 68000, 32000, 8080/8086/Z80, 8086/8088 and x86 for current Intel processors, as well as MC68332 microcontroller. I've written JCL for IBM mainframes running DOS VSE, MVS, and OS/390. I am a certified performance expert for VAX/VMS version 5.0, from Digital Equipment Corporation's education division, dated September 1989. I worked with MS-DOS 2.11 through MS-DOS 6.22 and MS-DOS 7.0 (embedded in Windows 95). Windows 1.4 through 3.1 and Windows For Workgroups 3.1.1, Windows 95 through ME, Window NT from when it was first released through the latest Windows 8.1, Window Server NT through Windows Server 2008R2. I've been a system administrator and developed software for Unix System V, BSD, Ultrix, Xenix, DEC Unix, AIX, HP-UX, and QNX. As well as VAX/VMS & Alpha/OpenVMS. And Linux Ubuntu, Debian, Fedora, all server and desktop, and Linux Mint desktop. I've worked on mainframes with ISPF/TSO and CICS. On Windows with MFC (Microsoft Foundation Classes), ATL, and .Net framework. With Telon, Easytreave, Microfocus Revolve, and PowerHouse. Database systems: IMS, IDMS, DB/2, RDB, SQL Server, MS-Access, Progress, Oracle, Sybase, and MySQL. I've installed/setup/configured/used Clonezilla server and client for mass deployment, and Windows Server deployment services. I've installed/setup/configured Windows Server Update Services.

That's what happens from a life-time career. I've held fancy titles like systems analyst, information systems specialist, technical architect. Worked for organizations large and small, private industry and government departments. You would think I could get a job. But no. So I have a little home business doing computer repairs.

By the way, "spaghetti code" is a bit of a contention between computer software developers vs engineers. Software engineering is part of the computer science degree, so I put software engineers with "software developers". But engineers from the faculty of engineering, and nuclear engineers and nuclear physicists, keep justifying "spaghetti code". Software guys consider that to be equivalent to designing a bridge held together with duct tape.

Last edited by RobertDyck (2014-12-08 04:57:17)

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#36 2014-12-07 19:14:39

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 25,719

Re: Habitat air

I figured that I would only give a brief summary of what I have learned but I can see many simularities and have always been lacking the titiles for the talent.

The other things that I can do is prototype build of electronics component as well as device systems using raw pc board, perferated using lead to lead construction or either laying down my own traces as well as wire wrapping or cutting from copper foil the etches to connect the parts on the pcb and even making my own artwork to build with all working to design future items. This does include all the sheet metal fabrication to house the guts within.

I remember working on magnetic tape drives the ones that had the vaccumn chambers,seperate cards for each of the functions to control two 12 inch reels that held inch wide tape to which 9 tracks of data was written in a variety of modes such as NRZ...same as the Apollo program used...

Last edited by SpaceNut (2014-12-07 21:09:01)

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#37 2014-12-08 06:29:21

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Habitat air

Terraformer wrote:

Then again, Robert, *you* have been continually claiming that fire is not a problem in high O2 atmosphere, when it is known that fire depends on O2% rather than partial pressure, and you've also ignored the ability of humans to adapt to CO2...

Discussions on alternative atmospheres would be a lot easier if we had a mathematical model that allowed us to predict how certain gas combinations and partial pressures would effect fire risk.  We need hard metrics that we can compare, such as ignition radiant heat fluxes and flame spread rate over a common material.  With a tool like that, we would be in a better position deciding what is safe and what is not.

I have some background in fire engineering.  I will see what I can put together.  The importance of the topic is clearly very high.  If we can use almost pure oxygen atmospheres with slightly reduced partial pressure, it makes space habitats a lot easier to build wherever you are.  On the moon, a pure O2 atmosphere is easy to resource.  An 80:20 N2/O2 atmosphere is extremely difficult.  On Mars, a lower pressure eases structural requirements.  It also makes spacesuit design easier.

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#38 2014-12-08 15:50:41

Antius
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From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Habitat air

http://www.sciencedirect.com/science/ar … 7707002426

'...Results showed that a wider flammable range was obtained in sub-atmospherics conditions. In middle pressure range (101–40 kPa), the required ppO2 for ignition decreased almost linearly as the total pressure decreased, indicating that higher fire risk is expected. In lower pressure range (<40 kPa), the required partial pressure of oxygen increased dramatically, then ignition was eventually not achieved at pressures less than 20 kPa under the conditions studied here...'

Interesting results.  They suggest that as pressure steadily declines towards 20KPa, the energy required for ignition tends to slope upwards.  Not sure why it would be, but certainly an interesting result.

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#39 2014-12-08 17:11:00

Void
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Registered: 2011-12-29
Posts: 4,556

Re: Habitat air

Although I have read to the contrary, I am supposing that Nitrogen carries off some of the heat without contributing to energy of combustion.

Ignition requiring Oxygen and a fuel, and heat.....

That's my best on that.

I think that thinking it though might provide what is needed.  Keep dangerous heat sources and combustible materials remote from low pressure high oxygen situations.
Have a High Nitrogen environment with higher pressure for those processes that require ignition sources and fuels to be exposed to Oxygen.


Done.

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#40 2014-12-08 17:17:17

Void
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Registered: 2011-12-29
Posts: 4,556

Re: Habitat air

I suppose I should provide you with an opportunity to evaluate me.  If I am more trouble than it is worth to keep, then please politely ask me off the site.  I will actually comply.

My history:
Graduated from high school (Just).
Was fortunate to easily get a job on those merits.

I worked in a red iron processing plant for a summer.  I worked a #2 shovel at first.  That means I shoveled muck from under a conveyer belt onto it.  Today Osha would not allow it I bet.  They were at the end of their rope trying to get ore out of the pit.  It was too wet.  The place I worked was the prelude to Taconite.

http://en.wikipedia.org/wiki/Taconite

They had tried sintering what they had, but I guess it did not work out.  I saw what they did what they had.

It was a loosing battle.  The ore was too wet.  They would try to dry it out but it spread out like pancake batter.

I worked that summer as labor shoveling mud more or less.  My foreman would stop us from working and make us sit down and talk smile  I was pretty thin, maybe he was afraid I would die.  They were old timers.  Not much like the work environment today.  Typically even though I wore cloth gloves, my hands were covered with open wounds, where the rubbing went from blisters to broken blisters.

Anyway, I quit the job after making a bit of money, and went to a technical school.  My class was all about process control, Vacuum tubes, transistors and pneumatics.
So, the previous contenders and I have vacuum tubes in common.

I graduated (Just).  I had very poor conditions for that schooling as I had to work at night, perhaps 3:00-7:00 in the morning.  I kept falling asleep in class. I was a Janitor at night.

Anyway, I got a job at the very plant where they pioneered the mining of Taconite.  So, I got to see those processes.  Sadly I was a bit wayward then with party life, having plenty of money, and being young.

Moved to a real Taconite plant, and was again a #2 shovel/hoser.  When you worked in the aglomeration process, pellets would fall from the process and you had to squirt them down a drain for recovery with a fire hose.  Lots of fun.  If a red hot pellet came down and got inside your shirt, the best policy was to lean forward and let it burn through and out.

Eventually an opportunity to be adopted to an Electricians apprentice opened up and I applied for it and got it.  I was a shop electrician.  They actually had classes you might even respect.  The instructors were not sub standard, I can tell you for sure. So I got to use some of my classes, and had to be involved with that for 2 years.  Although those classes covered electric motors they were actually more about a power distribution grid.

I did that I think for 2 years, and got a chance to change over to what was called a Instrumentation apprentice.  Electronics and process control.
As it seems it is usual for me so far, I finished 6 months before they threw out all younger Apprentice people (So that was 2 years as an electrician and 5 years as Instrumentation).  There were some sad stories for some of those layed off before completing their training, so I feel very blessed with what I have had.  As I worked my job, I was required to do shift work until near the end.  That involved being ready to fix a line asap, as in those days it was about $10,000.00 per minute it was down, Can't thing how much now.

So I worked there for 10 1/2 Years, there were significant layoffs which happens in that industry, so, on the bidding of a brother of mine I applied for a job with conglomerate.  I got it on the second try, and was working at a research center.  As support, you understand.

So, I did that, and had various further training.  Was exposed to scientists and those who help them.  My work was to calibrate and repair the equipment.  Electronics I was actually weak at.  In the mines, there were a few who might pretend, but I was not one of them.  It had been a long time since my 1 or less year of training.  But there were nice people who helped me.  Again a blessing I did not have a right to. 

I got through it, did a variety of things, eventually specialized in weighing equipment. Balances and Scales calibration.  Mechanical and electronic repair of them.

Got so tired of that after so many years that I got involved in I.T. of a sort.  I had previously begun working with VB6.0, and had also been involved with a vendors software which was for data entry of calibration data.  I got them to talk to each other. 

So I was sort of I.T.

I have gotten comfortable in the job, although it was hell to start with.  I am actually involved with VB6.0 (Historically), VBA (No thrills)  SQL, Crystal Reports and am working my way into VB2010 + and other languages.  I manage a database for calibration data as well, and am involved with Metrology, but am not a Metrologist.  A2LA certifications and such things, Uncertainty of data.

http://en.wikipedia.org/wiki/Metrology

I have spent a lot of time over the years at libraries until the internet, and now every day try to find new and interesting things on the web, which is why I am with you.

I am soon to retire if I want to.

I did at one point try to patent a process having to do with distillation of water, and that was a learning curve.  It got so intense that I think that I had an encounter with human madness or the spirit world.  Your choice.  I abandoned it for real world reasons (Real humans).  But that certainly opened my eyes.  It's not always what you might think it is.

I also took a course on Interior decorating, don't think I have what it takes for that.  Maybe later, if there is a later.  And also Real Estate.

That's about it about me.

Last edited by Void (2014-12-08 21:36:30)


Done.

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#41 2014-12-08 21:21:58

Void
Member
Registered: 2011-12-29
Posts: 4,556

Re: Habitat air

I really think it was a mistake to be done with vacuum tubes.  Transistors were needed for that current era, but space is a fair vacuum, and I think there were a lot of tricks to learn that were not learned about messing with electrons and ions in a vacuum.  It just was killed for that current sake of convenience and also for the current buzz at that time.


Done.

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#42 2014-12-09 14:23:15

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
Website

Re: Habitat air

As it turns out,  ironically enough,  vacuum-tube electronics tend to be nuclear-hard,  while nothing in the solid-state silicon world is.  By nuclear-hard,  I mean significantly resistant to (not totally proof against) the nuclear EMP wave that every nuke explosion generates in spades. 

The downside is that vacuum-tube electronics is orders and orders of magnitude more bulky and heavy compared to modern chip-based solid-state electronics. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#43 2014-12-09 14:55:59

Void
Member
Registered: 2011-12-29
Posts: 4,556

Re: Habitat air

I see your point as true, but it is a pity the drive for weight savings ended most of the tube process.  For instance if you are not going to push things around in space, say if you were working on the Moon, and because 3D printers are coming on line, for that location tubes might make some sense, and perhaps there are some interesting undiscovered properties, things that tubes could do.


Done.

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#44 2014-12-09 16:27:18

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,253
Website

Re: Habitat air

Tubes kept burning out. Transistors are smaller, lighter, lower power, but most importantly last longer.

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#45 2014-12-12 10:23:34

Antius
Member
From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Habitat air

I have found an interesting reference on the NASA archives - many thanks to Robert for bringing my attention to this excellent resource.

http://ntrs.nasa.gov/archive/nasa/casi. … 016199.pdf

Increased fire risk at higher O2 concentrations is driven by increased adiabatic flame temperature.  This increases the proportion of flame heat that is emitted as thermal radiation.  On Earth in air, a typical carbonaceous flame emits something like 30% of its heat as radiation; the rest goes into heating up the nitrogen component and flue gases and is carried off by convection.  In pure O2, the figure is closer to 80%.  This is because the flame burns much hotter without the heat capacity of nitrogen in the air and radiated heat from a black body increases to the fourth power of temperature – so even slightly hotter flames put out a lot more radiated heat.  Flames spread predominantly by radiation, which heats and pyrolysis the surrounding fuel bed, so an increase in radiated fraction will result in increased flame spread, which is exactly what we see.

I carried out a calculation of adiabatic flame temperature of methane in both air and pure O2.  In air, adiabatic flame temperature is ~2400K. In pure O2 at 1 bar, it is 5900K.  I was shocked by just how big a difference the nitrogen in air actually makes.

Flame spread rates are shown in Figure 3 over paper strips for a number of different O2 partial pressures and O2 concentrations (presumably in nitrogen).  Notice that at 1bar of 99.6% O2, flame spread rate is a whopping 4.3cm/s.  Extrapolating from the graphs, the flame spread rate in the Apollo 1 capsule at 1.14bar O2 would have been ~5cm/s.  This can be compared to the flame spread rate in air at sea level conditions (21% O2 & 1bar) – which is ~1cm/s.  In pure oxygen at 0.21bar, the flame spread rate is 2.3cm/s.  With decreasing pressure, the combustion rate of the fire is increasingly constrained by the reduced mass flow of oxygen.  The flame is buoyancy (differential pressure) driven.  For a roughly constant adiabatic flame temperature, we would therefore expect heat output per unit area of fuel bed to be proportional to the square root of oxygen pressure (from the Bernoulli equation).  This is roughly consistent with the results for 99.6% O2 in Figure 3.  If we extrapolate down to 0.14bar (two-thirds of sea level partial pressure and the limit for human habitation here on Earth), this gives a flame spread of ~1.88cm/s.

An interesting corollary in this reference is the effect of gravity on flames (See Figure 5 in link).  It would appear that one of the reasons behind NASAs decision to opt for almost pure O2 atmosphere in Skylab was the change in fire dynamics that occurs at reduced gravity levels.  In micro-g, flame spread rates drop dramatically, as the fire can only receive fresh oxygen via diffusion.  On Earth, buoyancy removes fire combustion products and replaces them with fresh air drawn in at the base of the fire.  This dramatically accelerates flame spread and allows the fire to burn hotter.  There is none of that in zero-g.  Apparently, NASA was well aware of this by the early 1970s.  The decision to abandon high O2 for the shuttle appears to have been driven more by safety on the ground than in space.  On the moon and Mars, where gravity is lower, flame spread rate is also reduced, although to a lesser extent on Mars.  Based on extrapolation from Figure 5, flame spread rate on cotton cloth in 3.5PSI pure O2 under Martian gravity is only 50% of that at full Earth gravity.  This will clearly have a big impact on fire dynamics on Mars.

When the gravity effects are taken into account, the flame spread rate for 0.21bar pure O2 on Mars, would be 1.15cm/s.  This is comparable to the flame spread in air at Earth sea level conditions.  At 0.14bar, it would be ~0.94cm/s.  Flame temperatures could be reduced comparable to Earth sea level if the air contained 0.3kg of saturated water mist per cubic metre.

Another interesting conclusion from this study concerns the auto-ignition temperature of solid materials (Figure 4).  Note that this appears to be a linear function of oxygen partial pressure, rather than concentration.  So in 0.21bar pure O2, one would not expect materials to be substantially more ignitable than they are on Earth.

The long shot is that low pressure pure O2 atmospheres do not appear to be excessively dangerous for a Mars habitat.  This would be especially true if it were fitted with automatic water mist suppression systems.  Fires would be more rapidly detectable in pure O2 due to their high radiated heat output and inadvertent activation would be easier to avoid than on Earth.

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#46 2014-12-12 13:27:32

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
Website

Re: Habitat air

I don't know for sure,  but I have heard there might be very-long-term medical issues with a pure O2 atmosphere,  whatever its total pressure.  These revolve around pregnancy.  It's because we evolved with diluted oxygen that these concerns arise.   It's not a problem for an exploration crew.  It might be a problem for a permanent base or colony.  Does anybody know the truth of this?

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#47 2014-12-13 01:05:42

Impaler
Member
From: South Hill, Virginia
Registered: 2012-05-14
Posts: 286

Re: Habitat air

Pregnancy is probably the most delicate thing imaginable, I've heard that just about anything outside of Earth-normals can screw-up the zygotes blastula stages which is already THE most dangerous time in any organisms development.  We really have no idea what conditions mammals need to get pregnant in space, I don't even think we have gotten rats to breed let alone people.

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#48 2014-12-13 08:43:14

Terraformer
Member
From: Ceres
Registered: 2007-08-27
Posts: 3,526
Website

Re: Habitat air

Well... we know people in Denver can successfully reproduce, and studies in rats showed few problems with elevated (>50mb) CO2 levels 1 week pre and post delivery...


"I'm gonna die surrounded by the biggest idiots in the galaxy." - If this forum was a Mars Colony

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#49 2014-12-14 11:41:02

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,833
Website

Re: Habitat air

Not much difference between 11 or 12 psia air and 14 or 15 psia air.  People have lived and reproduced quite successfully throughout history at altitudes up to about 20,000 feet.  Although those above 15,000 seem to have genetically adapted over the 1000's of generations.  The pressure at 15,000 feet is about 56% that at sea level,  or about 8.3 psia.  At 20,000 feet it's 6.8 psia. 

The actual human experience of "Earth normal air" is thus much wider than is usually assumed in these discussions.  There's nothing at all wrong with 21%O2 79%N2 at,  say,  9 or 10 psia.  Pp O2 at 9.5 psia is then 2.0 psia,  and Pp N2 is 7.5 psia.  Using the recommended pre-breathe factor of 1.2 on that Pp N2 says you can go straight to a pure O2 suit at 5.0 psia without any delay pre-breathing. 

So,  what do we need an 8 or 9 psia suit design for? 

Since donning MCP suits takes time,  that's your pre-breathe time.  (Going from Pp 7.5 psia N2 to 3.5 psia O2 is factor 2.1,  so some N2 blow-off time is required.)  My point is that this makes 3 or 4 psia MCP suits possible right now.  Those are compression levels already achieved by Paul Webb's elastic garments in the 60's,  and by Dava Newman's stuff at MIT.   

There are things you can do in an MCP suit that you simply cannot do in a gas bag suit.  We will need to do those things,  sooner or later.  Those things make the decompression blow-off time worthwhile.  I'd recommend having both types of suit on-hand,  wherever we go. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#50 2014-12-14 14:31:37

Impaler
Member
From: South Hill, Virginia
Registered: 2012-05-14
Posts: 286

Re: Habitat air

Because most of our Astronaut corp is going to come from normal low-altitude dwelling populations, they are going to train at our existing approximately sea-level facilities and will not be acclimatized to high altitude because we are not going to relocated our Astronaut training facilities to Himalayan plateau.  At best we might locate it in Denver (which is just 12 psi), but that would take more money and political upheaval then engineering a space-suit which has a cost of a few million to develop and already HAS been developed and which dose everything we need it too, their is nothing that the balloon-suit can't do that we would need MCP for.

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