Re: vacuum-safe laptops ?
On Fri, 16 Jul 2004, Major Variola (ret) wrote: Um, even the small form factor PC on a board the size of your palm may still rely on caps in the power supply that don't handle 760 to 0 mm Hg/min so readily. However, if you use a low-power board, you have less current to filter the ripples from, so you need smaller caps, which offers you more options. You can also replace the caps in the power supply for vacuum-resistant types, for the price of some soldering. Otherwise, there are many small PCs on a card if you look into the embedded marketplace. Complete with solid state disks, etc. COTS. Do you know some worth of being refered to, if possible low-cost? The situation on the market is changing so fast it's difficult to keep track. perhaps anon actually wants to run M$ in a low pressure environ. Perhaps that's why he's anonymous :-) Maybe it's agent of Microsoft looking for expanding the market to space! (Blue sky instead of blue screen?) My guess is regular ole airplane takeoff, but its not quite 0 torr at 35Kfeet, and I *think* the cargo part is pressurized, lest Fido suffocate. Also, a lot of cargo can be susceptible to lower pressures. Eg, the mentioned capacitors could be popping. So some overpressure during the flight has to be maintained there. And while a SAM would be a great science fair project, you don't go above that limit. Perhaps anon will be a space tourist, wanting to take notes, on something heavier than a PDA+keyboard. In that case, I'd suggest to build it as a wearable computer, integrated into the space suit. I once TA'd at a UC, one advanced ugrad had a project for an atmospheric science prof building a board for the nose of a spyplane, to sample the air. (For ozone, not nucleotides. No, really.) He was interested in vibration problems; I told him to take his proto board on an offroad trip in his car to shake out the moths. Wise. :) Am not sure that epoxy cover makes a difference, the board manuf. go to lengths to avoid air pockets under traces, the ICs themselves fairly (albeit not guaranteed) encapsulated in an epoxy mix. Sealing the boards in resin, under lowered pressure, could possibly help; the pressure of the atmosphere would be replaced by the pressure of the resin. Another option could be mounting the device into a hermetically sealed case, filled with eg. silicone oil for easier heat transfer.
Re: vacuum-safe laptops ?
On Sat, 17 Jul 2004, Tyler Durden wrote: Sorry to need educating once again, but I had assumed can-shaped capacitors were gone from laptops in lieu of surface mount. Anyone know? (I don't own a laptop.) The can caps can be surface-mounted as well. The leads then look different, but the inside is still the same: a metal can with etched aluminum strips and an insulator soaked with electrolyte. The magic smoke they are filled with also has the same color and smell as their non-SMD predecessors. See also http://www.elna.co.jp/en/ct/c_al01.htm for brief description of liquid-electrolyte aluminum capacitors. There are also some more modern constructions, where the electrolyte is solid-state. (The tantalum capacitors, which are more common in SMD form than the aluminum ones, use MnO2 as electrolyte and Ta2O5 as insulator. The added advantage here is that during a breakdown, the MnO2 layer locally overheats and is converted to less conductive Mn2O3, which causes the breakdown to heal. Similar mechanism is used in capacitors with solid-state plastic electrolyte.) I suppose the solid-state caps could be much more reliable in the conditions of rapid pressure changes, if they won't have moisture or air trapped inside their construction.
Re: vacuum-safe laptops ?
At 05:15 PM 7/17/04 -0400, Tyler Durden wrote: Sorry to need educating once again, but I had assumed can-shaped capacitors were gone from laptops in lieu of surface mount. Anyone know? (I don't own a laptop.) -TD With apologies, you really seem a troll at times. The *power supply* may use can-caps, obviously the bottom of the CPU is littered with solid-state ceramic babies.
Re: vacuum-safe laptops ?
On Fri, 16 Jul 2004, Major Variola (ret) wrote: At 06:35 AM 7/16/04 -0400, An Metet wrote: Does anyone *know* (first or second hand, I can speculate myself) which laptops, if any, can safely go to zero air pressure (dropping from 1 atm to 0 in, say, 1 minute.) waves hand furiously I got it! I got it!!! You're building an ICBM? -- Yours, J.A. Terranson [EMAIL PROTECTED] 0xBD4A95BF ...justice is a duty towards those whom you love and those whom you do not. And people's rights will not be harmed if the opponent speaks out about them. Osama Bin Laden - - - There aught to be limits to freedom!George Bush - - - Which one scares you more?
Re: vacuum-safe laptops ?
At 04:03 AM 7/17/04 +0200, Thomas Shaddack wrote: On Fri, 16 Jul 2004, Major Variola (ret) wrote: Sorry so late ---but your can-shaped capacitors might not handle the rapid depressurization so well. Perhaps it's time to challenge the introductory assumption. Why a laptop? There are many various embedded computers available on the market, eg. the one from http://www.gumstix.com/. Um, even the small form factor PC on a board the size of your palm may still rely on caps in the power supply that don't handle 760 to 0 mm Hg/min so readily. Otherwise, there are many small PCs on a card if you look into the embedded marketplace. Complete with solid state disks, etc. COTS. Power dissipation is not a problem if you use a CPU like Via's and have a nice radiative heatsink. Or dick with Peltier-effect junctions at the expense of watts. ARM's edge is low power, but you may not want to run Linux or BSD or a RTOS, perhaps anon actually wants to run M$ in a low pressure environ. Perhaps that's why he's anonymous :-) My guess is regular ole airplane takeoff, but its not quite 0 torr at 35Kfeet, and I *think* the cargo part is pressurized, lest Fido suffocate. And while a SAM would be a great science fair project, you don't go above that limit. Perhaps anon will be a space tourist, wanting to take notes, on something heavier than a PDA+keyboard. I once TA'd at a UC, one advanced ugrad had a project for an atmospheric science prof building a board for the nose of a spyplane, to sample the air. (For ozone, not nucleotides. No, really.) He was interested in vibration problems; I told him to take his proto board on an offroad trip in his car to shake out the moths. Am not sure that epoxy cover makes a difference, the board manuf. go to lengths to avoid air pockets under traces, the ICs themselves fairly (albeit not guaranteed) encapsulated in an epoxy mix. We-all being scientists, I'd suggest looking up with the vacuum hobbyists do with fridge pumps, etc, and doing a bit of testing. I've even seen using a CRT as a vacuum source, break the glass neck and shazaam, a few litres of hard vacuum. Got Kalman filtering?
Re: vacuum-safe laptops ?
On Fri, 16 Jul 2004, Major Variola (ret) wrote: Does anyone *know* (first or second hand, I can speculate myself) which laptops, if any, can safely go to zero air pressure (dropping from 1 atm to 0 in, say, 1 minute.) Sorry so late ---but your can-shaped capacitors might not handle the rapid depressurization so well. Perhaps it's time to challenge the introductory assumption. Why a laptop? There are many various embedded computers available on the market, eg. the one from http://www.gumstix.com/. (Question for the crowd: anybody knows other comparable or better Linux-ready affordable embedded computer solutions?) You may like to take such module and seal it in resin in order to shield it from the pressure changes (question for the crowd: would it really work?). Use memory card instead of hard drive; you don't want moving parts that depend on air density. The smaller size and lower power consumption than a laptop has makes many issues, from cooling to powering, much easier; vacuum-proofing and testing of the assembly is potentially simplified as well. I'd also be cautious about the fluorescent tubes for the displays, the glass won't necessarily have to withstand the rapid change in air pressure. The LCDs themselves consist from two layers of glass with a electricalyl-sensitive light-polarizing liquid between them, make sure it won't have tendency to boil or vaporize in vacuum. Optionally, for unmanned operation, do without the display completely. For manned operation, use something like the head-worn see-through http://www.microopticalcorp.com/ display, located in the operator's pressure suit, and connect it to the computer by a suitable wired or wireless connection. If the system has to go beyond the reach of the atmosphere, you would like to use some sort of radiation shielding, or use a redundant assembly with several computers working in parallel, compensating lower reliability (silicon-on-insulator chips are difficult to find in off-the-shelf setting) with redundancy. You may also prefer to keep critical systems working on lower frequencies, with older-design parts, using bipolar transistors instead of CMOS (which tends to trap charged particles in the insulator layers of the gates, which shifts the gate threshold voltage), and chips with larger structures (so the ionization traces of particles won't affect the chips that much). Protect the content of the memories - large arrays of rad-sensitive elements - with ECC codes. GaAs is also more radiation resistant material than silicon. Again, combine rad-hard design with redundancy for best results. Cooling is a royal bitch. You can't use anything but radiation cooling. I think satellites use a neat trick with pipes containing a wick soaked in a suitable liquid, eg. some freon. The liquid is vaporizing on the hot end of the pipe, condensing on the cold end, and soaking back to the hot end by capillary forces; this is used to bring the heat from the power parts and the sun-facing side of the satellite to the dark side of the satellite, from where it radiates to space. (Question for the crowd: Can thermal imaging be used for scanning the sky for low-orbit satellites? Other question for the crowd: How suitable would be this wick-in-a-tube approach for ground-level computers, could it increase the efficiency of heat transfer from the CPU chips to the wings of the heatsinks? Eg. for the purpose of having the computer sealed in an RF-shielded enclosure, with the heatsinks being part of the case, which could eliminate the cooling air inlets?)
Re: vacuum-safe laptops ?
Sorry to need educating once again, but I had assumed can-shaped capacitors were gone from laptops in lieu of surface mount. Anyone know? (I don't own a laptop.) -TD From: Major Variola (ret) [EMAIL PROTECTED] To: [EMAIL PROTECTED] [EMAIL PROTECTED] Subject: Re: vacuum-safe laptops ? Date: Fri, 16 Jul 2004 17:27:56 -0700 At 06:35 AM 7/16/04 -0400, An Metet wrote: Does anyone *know* (first or second hand, I can speculate myself) which laptops, if any, can safely go to zero air pressure (dropping from 1 atm to 0 in, say, 1 minute.) Sorry so late ---but your can-shaped capacitors might not handle the rapid depressurization so well. MV _ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/
Re: vacuum-safe laptops ?
Thomas Shaddack [EMAIL PROTECTED] writes: There are many various embedded computers available on the market, eg. the one from http://www.gumstix.com/. (Question for the crowd: anybody knows other comparable or better Linux-ready affordable embedded computer solutions?) When I investigated this a while back, gumstix were about the best deal. They also have pretty good support, it's a small company and the techies directly answer queries on mailing lists. Peter.
Re: vacuum-safe laptops ?
Hard drives won't be able to, you'd need solid state flash disks. Sustainable operation will dry out lubricant in bearings, so any fans won't last very long. Any cooling requiring convection won't work, radiative cooling only. I suppose backlighting should be able to do, don't see how LCDs will get damaged. If high voltage is sufficiently good insulated, otherwise it will arc. It all depends on how hard your vacuum is, of course. And how long you want to operate the device. You'd need an old laptop, passively cooled (if it won't foul up your vacuum, immerse it in silicon oil), outfitted with flash sticks or flash drives. All of this is an educated guess, of course. On Fri, Jul 16, 2004 at 06:35:02AM -0400, An Metet wrote: Does anyone *know* (first or second hand, I can speculate myself) which laptops, if any, can safely go to zero air pressure (dropping from 1 atm to 0 in, say, 1 minute.) -- Eugen* Leitl a href=http://leitl.org;leitl/a __ ICBM: 48.07078, 11.61144http://www.leitl.org 8B29F6BE: 099D 78BA 2FD3 B014 B08A 7779 75B0 2443 8B29 F6BE http://moleculardevices.org http://nanomachines.net pgpJXkSpVhEzs.pgp Description: PGP signature
vacuum-safe laptops ?
Does anyone *know* (first or second hand, I can speculate myself) which laptops, if any, can safely go to zero air pressure (dropping from 1 atm to 0 in, say, 1 minute.)
RE: vacuum-safe laptops ?
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of An Metet Sent: Friday, July 16, 2004 6:35 AM To: [EMAIL PROTECTED] Subject: vacuum-safe laptops ? Does anyone *know* (first or second hand, I can speculate myself) which laptops, if any, can safely go to zero air pressure (dropping from 1 atm to 0 in, say, 1 minute.) What's your application, exactly? A rocket? I don't know about rapid decompression, but one problem is with the disk drives - the heads rely on entrained air to maintain separation from the disk surface. Most drives are not hermetically sealed, and have a (filtered) port to the outside to equalize air pressure. Some drives *are* sealed, and will operate at low pressure. I've seen this issue disscussed in the context of computers and laptops at high-altitude astronomical observatories: most machines will suffer head crashes if you try to use them at 10,000 feet (jets maintain an internal pressure altitude of about 5,000 feet). Some applications use solid state drives to get around this: http://www.globalspec.com/featuredproducts/detail?exhibitId=10540fromSpotlight=1fromSupplier=0 Some displays may also be a problem. This is more an issue for big plasma displays. Sony makes a special plasma TV for high altitude use: http://www.superwarehouse.com/Sony_PlasmaPro_PFM-42V1A_S_Silver_42_Plasma_Display/PFM-42V1A_S/pf/330392 A useful article is at http://www.iht.com/IHT/SUP/031999/digi-08.html You might want to look at the Itronix GoBook Max. http://www.gobookmax.com/ This device supposedly meets MILSPEC: http://www.dtc.army.mil/pdf/810.pdf which is a USG survivability spec. It includes an explosive decompression test, but not to high vacuum. ..and of course, all this gets pricy. Peter Trei
