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REXIS/TiNi Telecon

REXIS/TiNi Telecon. Harrison Bralower Mark Chodas Dr. Rebecca Masterson Lt. Hal Schmidt. Agenda. Project overview Mechanical design for Frangibolt implementation Proposed fastener design Torque/preload relationship Planned flight conditions for Frangibolt operation

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REXIS/TiNi Telecon

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  1. REXIS/TiNi Telecon Harrison Bralower Mark Chodas Dr. Rebecca Masterson Lt. Hal Schmidt

  2. Agenda • Project overview • Mechanical design for Frangibolt implementation • Proposed fastener design • Torque/preload relationship • Planned flight conditions for Frangibolt operation • Electrical design for Frangibolt implementation • Overheating concerns • Request for quote

  3. OSIRIS-REx Overview = sample return mission = at least 60 g or 2.1 ounces (and as much as 2 kg or 4.4 pounds) =pristine carbonaceous material = a time capsule from the early Solar System! • SPACECRAFT FAST FACTS • 2 meters per side (6.6 feet) • 8.5 m2 of solar panels (91 square feet) • 5 Instruments • Touch-and-Go Sampler • Sample Return Capsule

  4. REXIS Roles and Responsibilities • MIT: Overall instrument responsibility • Space Systems Laboratory (SSL) • Instrument Manager and systems engineering • Flight software and Main Electronics Board • Thermal and structures • System integration and test • Earth, Atmospheric and Planetary Sciences (EAPS) • Instrument Scientist • MIT Kavli Institute (MKI) for Astrophysics and Space Research • Detector Array • Detector Array Electronics • Harvard College Observatory (HCO): Harvard-Smithsonian Center for Astrophysics (CfA) • Deputy instrument scientist • Instrument architecture/design (coded-aperture mask) • Lincoln Laboratories • CCID-41 Detectors • Aurora Flight Sciences • Safety and Mission Assurance

  5. REXIS Instrument Overview Sun • REXIS is the Student Collaboration Experiment on OSIRIS-REX • REgolith • We study asteroid dust • X-ray • Monitor X-rays fluoresced out of the asteroid by incident solar X-rays • Imaging • CCDs and a coded aperture mask capture images of the asteroid and create a global map • Spectrometer • Identify spectral lines in the collected X-rays to determine the elemental composition of the asteroid Solar X-rays 1999 RQ36 X-ray Fluorescence (XRF)

  6. REXIS Instrument Overview Radiator Coded Mask Radiation Cover Detector Array Thermal Isolation Standoffs Solar X-ray Monitor Electronics Box Z Y X

  7. Mechanical Design Radiation cover 3.67 in 1.42in Hinge 2.54in 4.51in Frangibolt

  8. Mechanical Design Head containment cap Titanium washers Titanium #4 fastener Titanium nut Deployable Fixed

  9. Mechanical Design Rubber shock absorber Titanium washer

  10. Mechanical Design 0.219in (distance to weak point from under bolt head) 0.213in (deployable thickness) 0.083in (structural lip) 1.156in (total bolt length taken from under the head) 0.375in (all washer dia.) 0.112in (bolt major dia.)

  11. Proposed Fastener Design • Design is standard #4 bolt except for flats at bottom of fastener to aid installation • Used to grip bolt and prevent it from turning during install • Other projects have noticed shear failure of bolts if the bolt turns during preloading • Is this an appropriate feature to prevent shear failure? 0.219in 1.063in 0.094in 0.063in

  12. Torque/Preload Relationship • Relationship between installation torque and bolt preload can vary up to 30% in some cases • Is our geometry particularly sensitive to preload? • Is there a preferred torque/preload relationship for our geometry? • Can TiNi specify a nominal installation torque along with, or instead of, a nominal bolt preload?

  13. Flight Conditions • Last time we proposed cold storage of the Frangibolt at -90C for 2.5 years and 5V input to the Frangibolt • We have changed this to anywhere between -20C to 0C cold storage over this time, with a one-week cooldown to -60C after which we would return to temp for about a week and then actuate at 9V input • Are these temperature conditions acceptable? Are they within the qualification limits for the FD04 actuator?

  14. Electrical Interface to Frangibolt • MSK5055RH controller converts nominal 32V input from • spacecraft down to 9V input to Frangibolt • MOSFETs: Aeroflex RAD7130-NFx, rated to 22A drain current

  15. Overheating Concerns • We are concerned about a situation during test where power is applied to the Frangibolt but the bolt does not actuate, which could overheat and permanently damage the Frangibolt given enough time • Is there an easy way to prevent this? • TiNi website suggests the Frangibolt actuates at ~100C, so in principle an RTD attached to the outside of the Frangibolt could be used to determine overheating of the SMA • Does a thermal model of the Frangibolt exist that we could use for this purpose?

  16. Request for Quote • We need two FD04 actuators and five fasteners per slide 12 of this presentation (an official mechanical drawing will be sent to TiNi shortly) • We would like to receive these parts by 6/1/13 • We need material certifications for the titanium fastener • Titanium specified per AMS 4965 according to TiNi ICD WI-2782-XX • We need material specifications for all other materials in the products we are procuring, but we do not need certifications

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