X-Sender: jcanham@mscmail.gsfc.nasa.gov

X-Mailer: QUALCOMM Windows Eudora Pro Version 3.0.5 (32)

Date: Mon, 10 Jan 2000 08:34:45 -0500

To: \"White, John A\" \<john.a.white2@boeing.com\>,

\"\'My Account\'\" \<me@leidecker.gsfc.nasa.gov\>,
craig.t.mueller@aero.org,

jkolasin@pop700.gsfc.nasa.gov, melanie.ott@gsfc.nasa.gov,

jplante@swales.com, ray.prestridge@lmco.com,

\"EXT-Beverly, David W\" \<david.w.beverly1@jsc.nasa.gov\>,

Anna@seawire.traveller.com, DChalk@BICCGeneral.com,

DZevotek@BICCGeneral.com, DRothermel@BICCGeneral.com, jli@spectran.com,

dyoung@spectran-specialty.com, mseifert@spectran.com,

harold.f.battaglia@boeing.com, moorec@pgocm1.ksc.nasa.gov,

BANKSE@pgocm1.ksc.nasa.gov, Daniel.Tambert-1@kmail.ksc.nasa.gov,

john.a.white2@boeing.com, david.j.gill2@boeing.com,

\"EXT-Buzzard, Frank T\" \<frank.t.buzzard1@jsc.nasa.gov\>,
klw@lucent.com,

djd@lucent.com, John.S.Canham.1@gsfc.nasa.gov

From: \"John S. Canham, Ph.D.\" \<John.S.Canham.1@gsfc.nasa.gov\>

Subject: RE: Mechanically agitating the fiber optic cable does produce

HF

As a first cut answer, It would be likely that either the electrostatic

discharge or radiative damage would result in the formation of HF
through a

number of means, it is unlikely that mechanical agitation would cause
this

phenomenon as the conductor and the polyimide are not present.

There is a plan to investigate the radiation effects upon the FEP by

exposing raw pellet material to radiation in the absence of silicon

containing materials. This should provide the same answer with respect
to

the FEP buffer.

John S. Canham

At 05:15 PM 1/6/00 -0800, White, John A wrote:

\>Hi Henning,

\>

\>I wonder what would happen if we tested the cable without the fiber in
the

\>same manor. Would w see equivalent amounts of HF produced?

\>

\>John A. White

\>EEE Parts IPT

\>International Space Station

\>Boeing - Huntington Beach

\>(714) 896-3311 X70236

\>

\>

\> \-\-\-\--Original Message\-\-\-\--

\> From: My Account \[SMTP:me@leidecker.gsfc.nasa.gov\]

\> Sent: Thursday, January 06, 2000 4:27 PM

\> To: craig.t.mueller@aero.org; jkolasin@pop700.gsfc.nasa.gov;

\>melanie.ott@gsfc.nasa.gov; jplante@swales.com;
me@leidecker.gsfc.nasa.gov;

\>ray.prestridge@lmco.com; david.w.beverly1@jsc.nasa.gov;

\>Anna@seawire.traveller.com; DChalk@BICCGeneral.com;

\>DZevotek@BICCGeneral.com; DRothermel@BICCGeneral.com;
jli@spectran.com;

\>dyoung@spectran-specialty.com; mseifert@spectran.com;

\>harold.f.battaglia@boeing.com; moorec@pgocm1.ksc.nasa.gov;

\>BANKSE@pgocm1.ksc.nasa.gov; Daniel.Tambert-1@kmail.ksc.nasa.gov;

\>john.a.white2@boeing.com; david.j.gill2@boeing.com;

\>frank.t.buzzard1@jsc.nasa.gov; klw@lucent.com; djd@lucent.com;

\>John.S.Canham.1@gsfc.nasa.gov

\> Subject: Mechanically agitating the fiber optic cable does

\>produce HF

\>

\> Gentles,

\>

\> Dr John S Canham (a UNISYS employee who supports our Materials

\>Branch) has

\> attached a 10 foot long segment of ISS fiber optic cable (cut from

\>the link

\> I\'ve been working with, called P7) to a mass spectrometer.

\>

\> The distant end of the segment is sealed with \"Apiezon Wax W\": this

\>stuff

\> has a vapor pressure of 0.6 microtorr at 20 degC, melts at 44 degC,

\>and is

\> applied at about 100 degC. The buffer tube of the near end of the

\>cable is

\> inserted into a stainless steel tube whose inside diameter is chosen

\>to be a

\> close fit to the outside diameter of the FEP buffer tube, and the

\>joint is

\> covered with Apiezon Wax W. Some external splices were added to

\>strengthen

\> this connection. John arranged the specimen as a coil of about ten

\>turns.

\>

\> The stainless steel tube is a few inches long, and enters a chamber

\>

\> containing a mass spectrometer. The chamber is 4 inches in

\>diameter; I do

\> not know how high it is. A port on the side of this chamber

\>connects to a

\> pressure gauge and turbomolecular pump, which is backed by a

\>molecular sieve

\> and then a roughing pump. (The sieve limits backstreaming from the

\>rougher

\> into the turbo.)

\>

\> It takes about a day for this system to pump out all the gases

\>normally

\> exhaled from the segment of cable after it has been soaked in air.

\>After

\> pump-down, the total pressure approaches roughly 0.5 microtorr with

\>the cable

\> attached. The main gases seen by the mass spectrometer are from our

\>

\> atmosphere: nitrogen, oxygen, neon, water; these gases leak through

\>the

\> jacketing and then the FEP buffer tube, and finally get to the mass

\>

\> spectrometer. (The total pressure is more two orders of magnitude

\>lower when

\> the chamber is sealed, without the cable attached.)

\>

\> John twisted the coil vigorously for several seconds, and noted the

\>presence

\> of HF within several seconds after the start of twisting. The HF

\>persisted

\> for several minutes; the amount detected decreased substantially

\>after some

\> five minutes.

\>

\> John stimulated the coil using a hand-held Tesla coil, moving it

\>back and

\> forth over several inches of one side of the coiled cable. John

\>estimates

\> that about as much as half the total length of the fiber optic cable

\>was

\> stimulated by the Tesla coil. The duration of excitation was

\>roughly two

\> seconds. HF became visible within a few seconds after the start of

\>

\> excitation, and persisted over the next five minutes. The Tesla

\>coil

\> produced roughly five times the amount of HF than twisting the coil

\>did.

\>

\> John will be attempting to estimate the number of moles (nanomoles

\>is likely

\> to be a more appropriate unit) of HF produced in these adventures.

\>But,

\> while we do not know production rates yet, I believe we can conclude

\>that

\> John has established that HF is produced by motion of the cable

\>(perhaps

\> because this motion creates sparks between the polyimide and the

\>FEP?), and

\> also by direct electrical action on this cable. Also, I believe we

\>can

\> conclude that easily detectable amounts of HF are produced within

\>seconds of

\> a several second-long stimulus, and that this HF can be detected for

\>minutes.

\> We know that a few dozen nanomoles of HF is enough to produce a

\>\"rocket

\> engine defect\".

\>

\> We learn from this that we cannot simply irradiate the cable and

\>then

\> transport it to John\'s mass spectrometer \-\-- atmospheric gases

\>quickly

\> dissolve into the cable to such an extent that the instrument is

\>saturated by

\> them for many hours, while the HF and associated products (i.e.,

\>COF2) are

\> so active (reactive) that they \"disappear\" within (nominally) five

\>minutes.

\> So we must irradiate the cable while it is in a good vacuum, and

\>then \-\--

\> keeping it under vacuum \-\-- transport it to the mass spectrometer

\>within a

\> minute or two. We are presently studying how best to do this.

\>

\> It seems clear that the source of the HF is the FEP. BICC has

\>kindly sent

\> us some FEP pellets (the same as the stock that feeds their

\>extruder). John

\> and I believe that we can learn something useful by exposing these

\>pellets to

\> x-rays from an industrial machine, and some others of these pellets

\>to the

\> gamma rays of cobalt-60. It can be much easier to arrange to keep

\>these

\> pellets in a good vacuum during the irradiation, and then to measure

\>the

\> amount of HF released, than arranging this for the cable.

\>

\> Henning Leidecker

\>

\>

John S. Canham