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.
n8035388@unicorn.wwu.edu (Worth Henry A) (09/19/90)
In article <ARNAUD.90Sep18101120@schizo.schizo.imposter.samsung.com> arnaud@schizo.schizo.imposter.samsung.com (Alain Arnaud) writes: > > > 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. > > My vote is with the WSA. ;-) To be fair, the ESA is not yet dealing with manned flight and is young enough to not yet be as afflicted by bureaucratic harding of the arteries as NASA. I'm not familiar with the ESA's organization -- has it been structured to avoid micro-management by every member's government and to discourage the formation of a cronic bureaucracy? If not, it will soon be as problem ridden as NASA. :-( I have not yet seen any knowledgable responses as to post-Challanger changes in the leak sensing system and/or scrub criteia. I fear that between the stricter post-Challanger criteria and the inevitable deteriation of shuttle systems from disuse and old age -- that NASA may be entering one of those no-win situations where the shuttles breakdown faster than they can be repaired. :-( On a unrelated note (or is it?), recently -- while ensnared in one of Seattle's many non-rush-hour grid-locks -- I caught the very tail-end of an NPR(?) interview of a Soviet space official. The official seemed to be stating that the Buran-class shuttles are all but scapped and (yes, old news -- but the interesting part follows) that they are proceeding with the development of a NEW shuttle system. Anyone in Netland have a confirmation and details as to what my traffic crazied mind thinks it heard? This may have been related to the recent visit, to the USA, by some Soviets seeking more joint space projects.
sysmgr@KING.ENG.UMD.EDU (Doug Mohney) (09/19/90)
>In article <ARNAUD.90Sep18101120@schizo.schizo.imposter.samsung.com> arnaud@schizo.schizo.imposter.samsung.com (Alain Arnaud) writes: > On a unrelated note (or is it?), recently -- while ensnared in one of >Seattle's many non-rush-hour grid-locks -- I caught the very tail-end of an >NPR(?) interview of a Soviet space official. The official seemed to be >stating that the Buran-class shuttles are all but scapped and (yes, old news >-- but the interesting part follows) that they are proceeding with the >development of a NEW shuttle system. HMM. Maybe. After all, an Energyna <sp> is a very nice booster even without a Buran hitching a ride.
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.
clj@ksr.com (Chris Jones) (09/29/90)
In article <1001@dg.dg.com>, ahughes@dg-rtp (Arch Hughes) writes: >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. > >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? According to the 24 September 1990 AW&ST, Crippen raised the limit from 600 ppm to 1000 ppm (when the hydrogran was in its "fast flow" mode; the limit is lower when the flow is slower), and some advisors were holding out for 1400 ppm. In the event, the hydrogen concentration peaked at 4000 ppm. "There is some belief among NASA's shuttle contractors that the agency is being overly conservative in its assessment of the hydrogen danger." (When do you want me to launch, April?) "One said, ''NASA is looking for a pure machine. They'll never find it.''" Also, NASA is willing to go to 10000 ppm, and would have no qualms about doing troubleshooting at that level. This is in keeping with the safety factor of four which they apparently use in many shuttle systems. They just don't want to launch in that condition. -- Chris Jones clj@ksr.com {world,uunet,harvard}!ksr!clj
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!gsh7wfosler@inmet.inmet.com (09/29/90)
For thoose of you who do not get AW&ST, an article on the shuttle
delay says that NASA managers say the problem is not caused by
aging orbiter systems or by plumbing repeatedly subjected to flowing
hydrogen. The orginal faults were traced to the umbilicals,
and the last set of leaks were confined to the orbiter aft engine
compartment and were not cause by the umbilicals. The orginal
limits was 600 ppm, which was raised by Crippen to 1,000 ppm on
Sept 14. During the fueling on Sept. 17, after switching from
slow flow to fast flow, hydrogen reached 2,200 ppm, flow was
reduced in hope that concentraction would revert to acceptable
limits, but when level peaked at 4,000ppm, the fueling was stopped.
There is some belief amoung NASA's shuttle contractors that the
agency is being overly conservative in its assessment of the
hydrogen danger.
It goes on to say that a manager of NASA says that NASA is comfortable
with levels of 10,000 ppm and that trobule-shooting would have been done
in that enviroment readily, but I do not understand what this means.
Carl Fosler