Gentlemen, start your engines???

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Chuck Crisler
Posts: 30
Joined: Wed Aug 02, 2006 9:44 am
Location: Windham, NH

Gentlemen, start your engines???

Post by Chuck Crisler »

I just read Andrew's latest update (http://stardustathome.ssl.berkeley.edu/ ... update.php). It sounds to me that Phase 3 is *FINALLY* lurching forward! :D Hot Dog! Maybe soon.

Chuck
jsmaje
Posts: 616
Joined: Tue Aug 15, 2006 8:39 am
Location: Manchester UK

Re: Gentlemen, start your engines???

Post by jsmaje »

Chuck, regarding that update, such unforeseen hold-ups are inevitable in even the best-run projects, and I wouldn't bet on a subsequent sudden burst of activity.

Personally I'd be interested to know more on the technical front. It seems that there will be an attempt to remove the aerogel tiles from the collector "without substantial loss of material", though the threshold for 'substantial' is unspecified. As a result the tiles will also need to be impregnated with "witness tracks" to maintain all-important trajectory information, their nature (? metal, glass, plastic wires, laser tracks or whatever), size, depth, number, position(s) and attendant potential further damage to the aerogel also being unspecified.

Apparently, while there have been "successful extractions of three tiles without substantial loss of material" so far (that word 'substantial' again), we're not told which tiles in particular (pre-flight, already-examined or new ones), and whether with or without the proposed 'witness tracks' inserted.

Basically, I'd like to know how much aerogel is likely to remain for us to examine after all these new procedures, and (given the ever-revised theoretical calculations) what may be the resulting estimated number of IS tracks to be found, always expecting the unexpected of course!

Also, given the apparent fragility of aerogel, I fear the catastrophe of a totally shattered tile into tiny tinkly fragments if slightly mismanaged. In which respect, it would be interesting to hear from the various jewellery experts who have been keen on obtaining, fashioning and mounting portions of aerogel as a sort of gemstone, particularly during phase 1. Their technical experiences could be of value to the team. It may well be the other way round, of course!

John
DanZ
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Re: Gentlemen, start your engines???

Post by DanZ »

Hi John,

Dr. Andrew Westphal was kind enough to take the time to answer your questions. His replies are below. Note, your original points have been highlighted in pink.

Dan

*******

…, Personally I'd be interested to know more on the technical front. It seems that there will be an attempt to remove the aerogel tiles from the collector "without substantial loss of material", though the threshold for 'substantial' is unspecified. As a result the tiles will also need to be impregnated with "witness tracks" to maintain all-important trajectory information, their nature (? metal, glass, plastic wires, laser tracks or whatever), size, depth, number, position(s) and attendant potential further damage to the aerogel also being unspecified.

These are great questions, thanks for raising them.

We haven't specified what we mean by "substantial". In practice it would be rather difficult to measure. In fact, no material will be permanently lost, even if a tile sheds some material around its edges -- all of the fragments will be conserved. They will just be substantially less convenient to search and handle. Nevertheless, if we lost more than a percent of the area of a tile during extraction, we would be concerned. So far, we have found no evidence for any loss of area, which is (so far) great news.

Regarding the witness tracks: they are simply "tunnels" made in the aerogel by a glass needle -- the same kind of needle that we use for keystoning. They
are configured in an "L", 500 microns apart, and they are each 200 microns deep. There are 15 triplets in a 3 by 5 array on the aerogel tile surface.

We also worried about the possibility of wiping out an interstellar track by accident. Even if we didn't look before we placed, we estimated that there is only a 1% probability, after placing all 6000 tracks, of having accidentally putting a witness track on top of an interstellar dust track. But we look before we place, so we think that this is very unlikely to occur.

Apparently, while there have been "successful extractions of three tiles without substantial loss of material" so far (that word 'substantial' again), we're not told which tiles in particular (pre-flight, already-examined or new ones), and whether with or without the proposed 'witness tracks' inserted.

All have had witness tracks put in before extraction. They are all real flight tiles, and all have already been imaged and searched by Stardust@home.

Basically, I'd like to know how much aerogel is likely to remain for us to examine after all these new procedures, and (given the ever-revised theoretical calculations) what may be the resulting estimated number of IS tracks to be found, always expecting the unexpected of course!

We should have more aerogel to scan than before, because the imaging will be so much better on the extracted tiles. We will be able to come much closer
to the edge of the tiles without the familiar coma-like distortions that experienced dusters are used to.

Also, given the apparent fragility of aerogel, I fear the catastrophe of a totally shattered tile into tiny tinkly fragments if slightly mismanaged. In which respect, it would be interesting to hear from the various jewellery experts who have been keen on obtaining, fashioning and mounting aerogel fragments as a sort of gemstone, particularly during phase 1. Their technical experiences could be of value to the team. It may well be the other way round, of course!

We worried a lot about that, and in fact we really didn't know whether this would work at all. So we practiced on the flight spare extensively before trying it on the real thing. It was clear that the flown aerogel was in fact different from the flight spares, but still it has been working very well. If it had not gone well on the first one we would have stopped and done a reassessment.

Best,

Andrew
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