Well, this is great to hear that a ROACH has been flown successfully on a Balloon.
How long was it up for? Do you have any photos? Thanks! On Tue, Apr 16, 2013 at 12:17 PM, Stachnik, Robert A (3282) < [email protected]> wrote: > Brad, > > We used a crude but effective scheme to fly a roach I on high altitude > balloon in Sept 2011. > Since weight for us is not a big issue, the approach is to use a thick > sheet of aluminum plate (~0.25 in thick) > and larger than the roach assembly as a heat spreader. We mounted the > roach board upside-down using spacers > to clear parts and connectors. (Xilinx heatsink and fan removed) To > contact the Xilinx chip and the PPC, we machined aluminum blocks matching > the chip footprint and matching the chip to plate clearance (within a few > mil). Any gaps were accommodated by Berquist thermal pad material. We also > put a similar heatsink on the ADCs using a copper strap and thermal pad. > We put spring loaded fasteners in the holes in the roach board near the > Xilinx chip to prevent the board from warping away from the heatsink block > in flight. > > We build up a 28VDC ATX-type power supply using Vicor modules. These have > a high power density, are easy to > heat sink and we've used these type on many balloon flights. > > Finally, we put a metal cover over the entire roach and power supply > assembly. Heat from the heat spreader plate was dumped through small > radiator plate that extended outside the gondola insulation. > > In flight, the FPGA internal sensor read about 65C peak during the day at > float (~4hPa) and at night cooled to ~20C. > > Hope this helps a bit. > Bob Stachnik > > > - > * Robert A.Stachnik, M/S 183-401| [email protected] > * Jet Propulsion Laboratory, | Office: (818) 354-1921 > * 4800 Oak Grove Drive, | Cell: (818) 653-8738 > * Pasadena, CA 91109-8099, USA | FAX: (818) 354-5148 > ********************************************************************** > ________________________________________ > From: Jason Manley [[email protected]] > Sent: Tuesday, April 16, 2013 4:37 AM > To: dana whitlow > Cc: Steve Maher; Vaughan Moss; Casper Lists > Subject: Re: [casper] Roach Conduction Cooling > > > Merely dunking things in liquid will just get you hot liquid. And > I'd be concerned > > about the chip packages' leak integrity. > > Excellent point. In fact, the Xilinx packages have breather holes that > prevent us from washing the boards after manufacture. So I'd be very > nervous about this. > > > My point is, don't forget the radiator. Then ask, perhaps, "Can I just > attach the > > chips to the radiator?". Perhaps this is already what Jason is getting > at, but he > > didn't say how his "heatsink" was going to dispose of the heat. > > Yeah, big fins on the other side of the alu! You'd have to run the numbers > to see how big and how many fins you'd need at altitude/thin air. > > Jason > > -- Brad Dober Ph.D. Candidate Department of Physics and Astronomy University of Pennsylvania Cell: 262-949-4668
