gsh7w@astsun.astro.Virginia.EDU (Greg S. Hennessy) (09/18/90)
The shuttle Columbia's launch attempt was just scrubbed. A hydrogen leak caused a concentration of more than 1000 ppm in the aft compartments. Values of 2275 ppm were measured. Values are currently less than 1500 ppm, but the mission is scrubbed for tonight. At the present time it is unknown what will happen. -- -Greg Hennessy, University of Virginia USPS Mail: Astronomy Department, Charlottesville, VA 22903-2475 USA Internet: gsh7w@virginia.edu UUCP: ...!uunet!virginia!gsh7w
arnaud@schizo.schizo.imposter.samsung.com (Alain Arnaud) (09/18/90)
What's happening at NASA. I am starting to beleive some of their critics that say that the agency should be closed. Their credibility has really gone down, specially after the latest scrub. They tell us that the leak was a seal problem, that it was fixed, and here we go again, another scrub. They should not cry wolf, too many times. I vote, to replace NASA with the ESA (European Space Agency). Let's launch our payloads on Ariannes and Shuttles from Guyanna. At least, ESA is capable of properly resolving and fixing problems in a timely manner.
ahughes@dg-rtp.dg.com (Arch Hughes) (09/22/90)
In article <1990Sep17.224055.1343@murdoch.acc.Virginia.EDU>, gsh7w@astsun.astro.Virginia.EDU (Greg S. Hennessy) writes: |> |> The shuttle Columbia's launch attempt was just scrubbed. A hydrogen |> leak caused a concentration of more than 1000 ppm in the aft |> compartments. Values of 2275 ppm were measured. Values are currently |> less than 1500 ppm, but the mission is scrubbed for tonight. |> |> At the present time it is unknown what will happen. |> |> -- |> -Greg Hennessy, University of Virginia |> USPS Mail: Astronomy Department, Charlottesville, VA 22903-2475 USA |> Internet: gsh7w@virginia.edu |> UUCP: ...!uunet!virginia!gsh7w Anyone know what concentrations of hydrogen are capable of causing a real explosion?
neufeld@physics.utoronto.ca (Christopher Neufeld) (09/25/90)
In article <993@dg.dg.com> ahughes@dg-rtp.dg.com (Arch Hughes) writes: >gsh7w@astsun.astro.Virginia.EDU (Greg S. Hennessy) writes: >|> >|> A hydrogen >|> leak caused a concentration of more than 1000 ppm in the aft >|> compartments. Values of 2275 ppm were measured. >|> >|> -Greg Hennessy, University of Virginia >|> Internet: gsh7w@virginia.edu >|> UUCP: ...!uunet!virginia!gsh7w > > >Anyone know what concentrations of hydrogen are capable of causing a >real explosion? According to the 1989-1990 CRC handbook, hydrogen in air will burn with flame propagation for a hydrogen concentration between 4.00% and 74.20% by volume. So, 2275 ppm is roughly a nineteenth of the minimum concentration required to cause an explosion, assuming that measure is ppm volume. -- Christopher Neufeld....Just a graduate student | "The pizza was just a neufeld@helios.physics.utoronto.ca Ad astra! | detonator; I mean, if cneufeld@{pnet91,pro-micol}.cts.com | it had set off the "Don't edit reality for the sake of simplicity" | hams...." Downtown Brown
gsh7w@astsun.astro.Virginia.EDU (Greg Hennessy) (09/25/90)
In article <993@dg.dg.com> ahughes@dg-rtp.dg.com (Arch Hughes) writes:
#Anyone know what concentrations of hydrogen are capable of causing a
#real explosion?
About 4 percent, or 40,000 ppm. The limit for a shuttle launch is
1,000 ppm.
--
-Greg Hennessy, University of Virginia
USPS Mail: Astronomy Department, Charlottesville, VA 22903-2475 USA
Internet: gsh7w@virginia.edu
UUCP: ...!uunet!virginia!gsh7wahughes@dg-rtp.dg.com (Arch Hughes) (09/26/90)
In article <1990Sep25.152824.15327@murdoch.acc.Virginia.EDU>, gsh7w@astsun.astro.Virginia.EDU (Greg Hennessy) writes: |> In article <993@dg.dg.com> ahughes@dg-rtp.dg.com (Arch Hughes) writes: |> #Anyone know what concentrations of hydrogen are capable of causing a |> #real explosion? |> |> About 4 percent, or 40,000 ppm. The limit for a shuttle launch is |> 1,000 ppm. |> |> |> -- |> -Greg Hennessy, University of Virginia |> USPS Mail: Astronomy Department, Charlottesville, VA 22903-2475 USA |> Internet: gsh7w@virginia.edu |> UUCP: ...!uunet!virginia!gsh7w Why is there such a great gap between the launch limit and the 4% concentration? If the limit was 2% (20K ppm) wouldn't there be ample time to scrub as the limit was exceeded, and vent the gas?
palmer@nntp-server.caltech.edu (David Palmer) (09/29/90)
ahughes@dg-rtp.dg.com (Arch Hughes) writes: >Why is there such a great gap between the launch limit and the 4% >concentration? If the limit was 2% (20K ppm) wouldn't there be ample >time to scrub as the limit was exceeded, and vent the gas? If the amount of Hydrogen exceeds the launch limit, that means that there is something wrong, and something wrong may become very wrong. If you analyzed some food, and found that its cyanide content was only 1% of the LD50 (the dose required to kill half the people eating it), you probably would want to avoid that food, even though it would probably have no ill effects on your health. The area into which the Hydrogen leaks is flushed with Nitrogen, so it wouldn't explode even at 4%, but the principle still holds. -- David Palmer palmer@gap.cco.caltech.edu ...rutgers!cit-vax!gap.cco.caltech.edu!palmer I have the power to cloud men's minds -- or at least my own.
gsh7w@astsun8.astro.Virginia.EDU (Greg Hennessy) (09/29/90)
In article <1001@dg.dg.com> ahughes@dg-rtp.dg.com (Arch Hughes) writes:
#Why is there such a great gap between the launch limit and the 4%
#concentration? If the limit was 2% (20K ppm) wouldn't there be ample
#time to scrub as the limit was exceeded, and vent the gas?
Because the sensors can be several feet, or tens of feet from where
the leak is. The concentration will increase as you get closer to the
leak. NASA is leaving themselves a healthy safety margin.
--
-Greg Hennessy, University of Virginia
USPS Mail: Astronomy Department, Charlottesville, VA 22903-2475 USA
Internet: gsh7w@virginia.edu
UUCP: ...!uunet!virginia!gsh7w