Minutes of the Tracker Meeting
April 1, 2004
- Robert: remarks on the Lehman review Tracker presentation
- Jeff Tice: bottom tray core
- Riccardo/Sandro: schedule for bottom/top tray tooling; documentation; production readiness
- Mike: status of interface hardware procurement and qual test plans
- Riccardo: Plyform mid-tray progress; sidewall prepreg status; readiness for ESPI test
- Sandro: status of work at G&A preparing for MCM mounting and ladder mounting/wire-bonding of bottom trays; documentation status; plans for PRR.
- Albert or Dave: MCM status
Last week's action items:
1. Robert: give Jeff Tice information to procure cables for T/V testing
2. Riccardo: check whether glass beads could be used to ensure bondline thicknesses in the bottom tray assembly. Done---answer was no
3. Mike: correct the epoxy called out in the BOM for closeout assembly (and other tray drawings)
4. Riccardo: help Plyform correct the prepreg RFQ with the right specification table. Done
5. Jeff Tice: procure Keenserts for the grid simulators
6. Riccardo: send the ESPI procedure to Robert for release. Done
7. Robert: release the tray vibration procedure. In progress
Older open Action Items:
1. John Ku and Mike Opie: draft or redlined static and vibe test plans
Robert reported that the Tracker presentation to the Lehman review was reasonably well received, but there was a great deal of concern expressed about the schedule. We presented a 3-week slip relative to the February PMCS status, such that Tower A completes environmental test just before the August shutdown. Reviewers pushed Robert hard on finding ways to improve on this, to make sure that the Tower A delivery doesn’t slip into September. Lowell promised that for the next review (end of September) there will be one tower on the Grid at SLAC taking cosmic-ray data. (Unfortunately, status presented in these minutes erode even the schedule presented at the review by several weeks---bottom tray assembly start, mid-tray assembly completion, MCMs)
Jeff Tice reported that he is able to cut the heavy core material with scissors, one cell at a time. He said the result looked better than the Plascore cut. He predicted a 4-week lead time for new cores, not including shipping to Italy. Sandro said that Plyform had to trim cores for EM trays. They don’t like doing it but will if absolutely necessary for the first two trays. It was suggested that they take some bottom tray cores back to Pisa and trim them there, so as not to impact Plyform.
Sandro said that next week they will release the bottom tray assembly fixture drawings to G&A and will have the parts back at the beginning of May.
Sandro said that results on the mid-tray dimensional measurements can be found in the CDR peer-review presentations. Robert will pass that information on to Martin. In fact, all of those presentations can still be found online at http://www-glast.slac.stanford.edu/Tracker-Hardware/Peer%20Review/peer.html. They did not have time to make the same measurements on the top and bottom trays in the mad rush last summer to get the EM tracker assembled and vibe tested before the Alenia shutdown (déjà vu).
Mike reported that the flexures are still scheduled for April 9 delivery. He will confirm this status with Advanced Machining. Joe will witness the CMM inspection of one complete set April 9 at the vendor. All but Borden's side flexures and 1 set for SLAC tests will ship to Pisa immediately. SLAC will also send the CMM data to Italy.
He and Jeff are ordering interface hardware parts for 36 joints. 12 are for the static test, 12 for the EM vibe test, and 12 for engineering development. 2 of the latter were ordered on a credit card for early delivery, about a week from now. The other 34 are expected about a week later. These will not be flight parts, as the drawings are not released. Arthur said that he is waiting for latest round from Martin on checking and redlining the drawings. We will need a review also by Pisa before releasing the flight production. Arthur has a clamp concept sketched out for Mike to review. Mike will send Pisa a copy of this drawing.
Jack reported that they have started correlation of data and model for the thermal-vacuum test.
Mike reported that a designer is working on modifying the static test grid simulator part for the new interface. The changes are minimal---just move the holes to match the new side flexures and modify the bore and counterbore to match the new interface hardware. Since the fixture is steel, we don’t have to mess with Keenserts and bushings.
Sandro expressed some concerns about handling the static test grid simulator. It is very heavy, so there is a risk of injury or damage to a tray. There is also concern about whether the 2nd tray in the fixture will hold up to repetitive use (don’t we have other trays that could be put in its place?---Robert) Mike said that heat straps are not needed from the loads point of view, but at least a spacer is needed to fill the gap between sidewall and closeout. Mike will set up a telecon for next week for discussing static load test issues and fixtures.
Mike reported that another designer is working on the vibration test fixture redesign. Mike wants to get the requirements definition correct. There is a meeting this afternoon on this topic. They have to relocate mounting holes and make them very similar to the planned holes in the Grid. Also, he will correct the protection scheme for cables during vibration and transportation. He will also add some tooling balls, but that is easy. He said that Martin has some other ideas that would complicate the design. Nanda stressed the need to keep the fixture very stiff. Mike concurred.
Mike reported that Robert Ruland, manager of alignments group, is meeting regularly with Mike and Martin and others to go through the alignment strategy. They are making progress. Another meeting will be held today.
Emilio will send tomorrow some drawings for the inner container concept. Jeff Tice is working on getting a new outer container specification and design. There is not problem to get almost any desired height from the same vendor as the last container. Once he knows the height of the inner container, he can specify an outer container height much reduced from the previous case and also specify the interior fit (looser than the last time). He will also add features near the bottom to strap it to a pallet.
Nanda said we need more complete environmental specs for the outer container, for vibration and humidity, as well as shock. Sandro said that he will put the recorder data on the web from the road transportation loads back and forth across Italy.
We also need to refine requirements for tray transportation within Italy (Ku and Opie?). The general concept is that the tray will be mounted in the special aluminum box from Bari (connected via the closeout inserts). That box will be in a protective envelope and packed in a rigid box with foam. Since a lot of trays will have to move at once, they will design a shipping container that can hold a lot of trays at the same time.
Sandro reported that has not yet started gluing closeouts into the tray panels. There is a delay in starting up that he and Nanda will try to understand when then visit Plyform tomorrow. They will send this information to Robert and Jim.
Inserts have been bonded into >60 closeouts. Unfortunately, Riccardo discovered that the inserts were all made from 7075-T6 aluminum, which is not approved by NASA, for reasons of susceptibility to stress-corrosion fractures. The same material was used throughout the EM tower. The MAR, section 7.2.6, says no Table-III materials may be used without a special materials usage agreement. Jeff will talk to Fred Gross about the implications of this. The MSFC-522B document in which Table-III can be found says that Table-III material can be considered in cases where the environment is benign, which seems to be very much the case for the Tracker (the LAT has strict humidity control requirements because of the CsI in the calorimeter, and the Tracker is deep in the center of the instrument).
Robert will check Sandro's email of drawing issues against Jeff's spread sheet. Robert informed the group that Jeff and Martin have put a very complete listing of drawings and parts on the web page, to replace the old drawing tree. It can be found at http://www-glast.slac.stanford.edu/Tracker-Hardware/default.asp, click on New Drawing Tree and Parts List.
MCM status: Teledyne guarantees the first lot of 25 flight MCMs by April 23 (4 weeks ARO) but will try to pull that schedule in by a few days if possible. All 25 are kitted as of today and are started into the production line. The second lot of 25 should be a week later, at which point we will have enough for Tower A.