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Computers in Space Examined
Wil Harris writes "There's an article about the computers used in space missions over at bit-tech this morning. It covers the processor types and speeds, why space stations are less powerful than the laptops that astronauts take up with them and why tape storage is still de rigeur. An interesting and concise couple o' pages."
Doesn't it seem very strange compared to the days where the goverment had super computers and the regular people had no computers? A stark contrast indeed. Now we are...close to the same level? Does this sound realistic, or are aces up their sleeves?
Dave Mills (inventor of NTP) told me that on the last Columbia shuttle mission, they were running some experiments with NTP in space. And, thankfully, they transmitted all their data before landing. But apparently, they were so overworked, they didn't have time to calibrate the machine properly, so sadly, the data is useless.
To make laws that man cannot, and will not obey, serves to bring all law into contempt.
--E.C. Stanton
Just like Cassini, the Hubble also has on-board solid state recorder (installed during one of the servicing missions), which replaced an old tape recorder. This has been really a nice addition as we can store more data into the solid state device while collecting data bits and dump them when the downlink becomes available. It really helps increase the efficiency of the satellite (and that's a big thing for science mission).
[Note that I've simplified the scheme alot here.]
Though several sections of the device have been damaged by radiation, or something, I hear. So even these things aren't too resilent to the harsh space environment, yet. Something you future engineers should think about as a project.
They need more performance than space equipment, and space equipment has power concerns that studio equipment does not, so the equation balances.
I never vote for anyone. I always vote against.
-- W.C. Fields
see http://spaceflight.nasa.gov/gallery/images/station /crew-1/hires/iss01e5127.jpg
Not necesarily. If people don't have to be in a particular part of the spacecraft, why waste air having atmosphere?
I'm wondering if more powerful computers will ever get up there. As the article states, computing power is minimally needed. Will the space industry ever be able to take higher-powered computers into space? This brings forward the question that if high-powered computers can never get off the planet, how will the future space industry be impacted by that?
Yep, that's right. I've been using CCDs at a ground level for long, seeing CRs zapping through a tiny detector in a short integration time (a few seconds). We are also surrounded by mildly radioactive materials (some paint, rocks, etc), which can cause radiation damage as well.
And surely that's part of the reason that I always buy ECC RAMS for mission critical stuffs.
An embedded machine, OTOH, is designed to do one, or a very small range of things, very well, very reliably, and very efficiently. I have had the fortune of working on two space based projects. In the first we used a single board Z80 based space hardened 'computer' to control a simple set of devices. It stored the ASM code in an EEPROM. It was more complex than we needed, as it was a standard issue unit, but much simpler than the Apple ][ we used as the GPC.
On the second project, 10 years later, we were not using incredible different machines on the satellite, though the GPC was now a Wintel machines with 100X the memory and speed. But when your main concern is that things just have to work, processor speed and OS wars have little meaning.
So these stories about how underpowered and behind the times embedded systems are just annoys me. It is just like continuous burns on SciFi shows(kudos to Babylon 5). Perhaps meaningless power is important to the ignorant masses, but we on /. are supposed to know better. I was using a tape drive until at least '87, just because It Worked.
"She's a scientist and a lesbian. She's not going to let it slide." Orphan Black
Radiation in space is usually not high enough to cause extensive phyiscal damage to processors in the short term. However, some kinds of radiation can cause random electrical noise on the processor, screwing up calculations. The larger the components, and the fewer of them there are, the less likely this is to happen. Of course, like all government agencies, NASA is very cautious about waiting to see how well components work. This is one of the reasons cell phones are not allowed on airplanes, the FAA has taken 10 years "just to be sure" nothing bad could happen. Also, NASA tends to use "hardened" processors, which have special shielding, as well as a mesh of wire that helps ground random electrical noise. These processors have to be specially designed and made by manufacturers based on existing designs, then rigorously tested by the company and NASA. Even if they start with a cutting edge design, by the time it is NASA tested and certified it is several years old and several generations out of date.
The first 8" wafer line of Honeywell's SOI VII HX5000 0.15 micron will be officially opened by the end of the month.
geremy
On board the International Space Station, they run programs checking for bit flips.
Single Event Upsets happen occasionally, but it's difficult to tell if they're associated with actual hardware failures or just if they're just coincidental.
They have 2 networks of IMS A-31P laptops for Command & Control of the station (PCS) and another network for situation awareness, procedure viewing, inventory tracking, Office tools (Word, email, etc...) and a few other uses.
They're not completely COTS laptops - they've been modified somewhat for radiation and cooling purposes (convection cooling doesn't work in microgravity) but they're pretty close to what you'd buy on Earth.
The printers, on the other hand, have some really cool attachments for the paper input & output trays to keep the paper from floating off... but that's another topic.
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Real space battles will be boring as hell.
Somehow, I doubt that. A tactical spacecraft--at the current, only an ICBM or slimiar missle--will be nothing but manuvering, with an unusually high allotment of its weight given over to course correction.
It won't be Star Wars, but it won't be interplanetary pool, either.
They are not useing the junk tape drives that you were using, but quality stuff. Mainframes have always put most of their data on tapes drives, and they rarely have problems.
Course a mainframe tape drive can cost $30,000 each, (not counting the robots that load them) so you can see why home users don't get that quality.
Nope. Don't read Car and Driver. Did break a window with one once. Dunno why Car and Driver would print that, but it wasn't hard.
I want a new world. I think this one is broken.
The controller for the SSME (Space Shuttle Main Engine) uses a pair of 68000 processors. It is a very critical system. If something starts to go wrong with the engine, it has to detect the problem and shut the engine down before it progresses to a catastrophic failure. It uses two redundant processors for reliability. Each engine has its own controller.
Old microprocessors like the 80386 and the 68000 were the last commercial processors before cache, pipelines and other trickery made timing analysis difficult or impossible. Some people have used DSPs for controllers because they still offer predictable timing.
Mea navis aericumbens anguillis abundat
There's the cold of space and there's the hot of space. Most spacecraft don't spend their time pointing in ONE direction so the ships have to built with some expectation that exposed parts will face heat and cold.
Anything exposed to the sun is going to get very hot indeed. That'd be bad for a bare CPU.
Anything exposed to the night side (or the side where the sun ain't) is going to be cold but a CPU is still going to need a heat sink to effectively remove the heat. Empty space is not a particularly good conductor of thermal energy (i.e. heat).
Most exotic space-approved processors are not powerful enough to need the exotic cooling we need here on the ground. Your P4 or AMD64 flies here. But not in space.
Here's a thought: if WE launch spacecraft using fairly obsolete technology because it usually works, what does that say about any alien technology we might someday run across? It is logical to think whatever we encounter might be their version of "obsolete but reliable" tech.
Therefore, if we actually DO have captured UFOs, perhaps whatever makes them tick -while exotic and exciting to us- is not nearly the most advanced technology the aliens might have. Perhaps the common antigrav UFOs are no more advanced the average junker WWII-era Jeep. Good for some off-road kicking around but nothing special compared to a modern off-road vehicle.
Military analogy: the common UFOs are the Air Force Cub trainers. They keep the F-35s and the aircraft carriers at home.
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There was a slashdot article on this a long, long ago...this might be it (not original, however):
They Write The Right Stuff
It's a must read for programmers at mission critical stuff.
"Somehow, I doubt that. A tactical spacecraft--at the current, only an ICBM or slimiar missle--will be nothing but manuvering, with an unusually high allotment of its weight given over to course correction."
So, what's to prevent the engaging ship from detonating weapons in six to eight positions relative to where they think the target is, so that if the target moves they still end up destroying it?
I'd think that the future of space warfare would be in the effectiveness of decoys and disguise, rather than in the effectiveness of dodging close range fire. If they can't find you then it's harder to hit you, and if they find a convincing enough decoy then they may mistake its destruction for your destruction, leaving you to find them and destroy them or to pull out and regroup elsewhere.
Do not look into laser with remaining eye.
"True hardware box failures are taken care of by redundancies,not by limiting parts."
It's still very smart to use a small core of very expensive and high quality parts that can function entirely on their own, rather than to have a vast, interconnected system that needs most everything present and working in order to remain functional. It's kind of like Galileo and the Voyager probes, where the basic core was over-engineered the right way to withstand problems, while the external stuff was ultimately expendable or redundant.
"Yes, but response time for anomaly teams is usually an hour at best. Many satellites have built-in error checking and will take care of themselves given the chance, including putting themselves into 'safemode.'"
These systems drop back to a minimal mode using their high quality cores while ignoring the add-ons and modules that have failed. The basic system is very solid, the severable or ignorable expansion bus, to use an analogy, is where parts that could malfunction or otherwise have issues are placed, so to reduce the chances of causing a complete failure. K.I.S.S. principle is a very, very good design, especially when there are a lack of restrictions governing how the core has to be applied. Cars got complicated, for example, not when automakers decided to make them more difficult, but when external forces like pollution controls forced automakers to cobble extra stuff on to their engines and exhaust systems, and when fuel economy rules forced the adoption of increasingly complex control systems that are themselves prone to failure LONG before the "open valve, suck air and fuel in, compress fuel/air, explode fuel/air, decompress fuel/air, force fuel/air out through another valve" portion of the engine malfunctions.
Do not look into laser with remaining eye.
It's MUCH easier to harden a processor that has the bigger die spacing, doesn't take much/any shielding for use inside the van allen belt. If you go to more modern stuff, you are going to need about 50 pounds of lead to shield it.
Ironically enough, after I wrote this I checked in with work. They were busy working with the crew restoring a crashed file server onboard that is used for non-critical stuff like email and digital photos.
What happened? Corrupted hard drive.
Worst...sig...ever!
What you are talking about is used for encryption and or compression: http://en.wikipedia.org/wiki/Huffman_coding
e
ECC probably uses other mechanisms: http://en.wikipedia.org/wiki/Error-correcting_cod
Hamming code is a very well known example, the number of bits that can be corrected with it is dependant on the number of correction bit used. Wikipedia hasn't got a very good explanation of the hamming code and I wasn't able to find one quickly, but if you want to know use google.