I believe so. I have always written my own runtime executable routines for the (limited) embedded sysetms work that I have done, so I'm not an expert on it. I was thinking more along the lines that QNX could give an idea of the memory footprints for Linux....
Okay, I went and did some checking, since I was curious anyways. It appears that a typical Linux kernal is 1.5 Mbytes. Too big for most real-time systems. On top of that, the kernel itself is a fairness scheduling algorithm, _and_ if a process is using the kernel resources, the process has to finish before the kernel is available for another process.
BUT! The kernel is modular (and open source!) so you could redo the algorithm, or take out modules to obtain something that has a scheduler more appropriate to real-time systems.
AND, the memory footprint of the kernal can be scaled down depending on what you need (or use) to about 300Kbytes for the kernal and about 100Kbytes for the file system, plus another 4Mbytes of RAM. If you include TCP/IP, it gets to be about twice as big. I got this information from here: http://www.lynuxworks.com/products/bluecat/faq/usi nglinux03-long.php3
Even though that is one site, it appears that the info is conceivably possible.
Why? Because there are countries and people that are opposed to the US, and will use warfare to achieve their goals.
Think of it this way: you are a soldier (something few of the people on/. were, is my guess), and you are going into a battle. If you are facing the US military today, with all it's weapons, and superior technology, it's almost certain that you will be found and killed. What's that? You're hiding in some trees? That Apache pilot will turn on his FLiR and see you, then shoot you.
And say instead you are facing... Indian troops in a different situation. Their technology is less developed than the US. No fancy laser targeting, not much in the way of IR. Yeah, they still have bullets, mortars, grenades, artillery, and nukes... but if they can't see you, then they can't exactly shoot at you.
And if you are fighting someone that can rain fire down from the sky, without ever seeing them, then you are pretty much not willing to put up a fight.
Another reason to support weapons is to look at the parallel between the US and the Roman Empire in terms of military might. The Romans (in their day) were superior. They fought as a unit, with every soldier equipped with armor and weapons, and they had good training. The Romans didn't always win their battles, but they ALWAYS won the wars. _Until_ the Roman government put less emphasis on the military (went with conscripts and less-trained soldiers, instead of pros). That inevitably created a situation where Rome could fall, because the military could not hold the Empire together.
Now look at the US military, we've won most of the wars we've fought. The ones we've lost, we have identified the errors and corrected them. We also develop superior technology to make sure that we have the edge on the battlefield. If we did not have that edge, we would face whole nations opposed to our ideology.
Besides, if other nations (or persons) become more advanced and decide to attack us, are we going to fight with insults and our money?
As long as there are threats, the US will need to have a strong military. The weak do not go after the strong. That's a fact of life. And the rest of the world should be glad that the US is not in the business of building an empire.
Until you kill all the terrorists with your disposable machines.:p
Besides, bombers can never take ground. That's always going to be up to infantry.
These will be just another element to the military.
When it only takes a few days or weeks for someone to crack the protection scheme. I say let them keep putting out copy-protection schemes. Then laugh when their money goes down the drain. Either the copy-protection schemes will survive, or there won't be any copy-protection schemes.
(Although I'm not a fan of warezing games... I'd just like to point that out.)
There is this thing called MIL-STD-461 which governs how much EMI a device aboard an aircraft can generate. It gives strict limits on how much EM leakage and susceptibility you can have... even for something as seemingly benign as a wire bundle. MIL-STD-462 governs how the devices should be tested.
The other thing is that pretty much ALL personal electronic devices are class B devices (according to the FCC). So they can't generate interference onto other devices... Problem is that almost no personal electronic device has EM shielding, eddy current dissipation methods, or a way to attach to the plane's common ground.
Personally I'd rather not have people using their cell phones or whatnot. Besides the noise, I'd rather not trust those $1 (US) RC filters used to dampen eddy currents.... which are actually just a 2 cent capacitor and a 2 cent resistor, but because it's validated against a specification it costs a LOT more.
So as long as the FAA regulates that MIL-STD-461 has to be used, there is no way around the rule against certain electronic devices.
-It's design is probably older than most of the posters here on this forum. When it was originally concieved as a horizontal take-off and landing craft, it was assumed that the wings would provide enough lift to get the orbiter to orbit. That didn't work, because the shuttle by itself cannot carry enough fuel and still lift a usable payload. The delta wing that the shuttle uses has a L/D (lift-to-drag) ratio of something horrid... like 5. (A sailplane typically has an L/D of 25+. And your average Cesna 172 has an L/D of about 10. In any event, they needed more thrust, but the shuttle was already designed... so they had to slap some solid boosters on it. BUT! It turns out that having a multi-stage lift system is more efficient than a single-stage to orbit system in terms of how the thrust is used. SSTO concepts (Single Stage To Orbit) are researched because of the inherent simplicity in the system, and because technology has progressed enough that engineers feel comfortable working the numbers on the designs. (If you asked companies to build an SSTO 30 years ago, they'd have laughed at you... or asked for huge sums of money.)
-The shuttle is currently the only vehicle in the world that can lift the payloads that it does. It's literally a workhorse. It is THE perfect vehicle for missions to ISS. No other vehicle can do what the shuttle does now.
-The shuttle is still a test aircraft. People get complacent with the technology because they see it work so often. The shuttle crews know this, the people that work on them know this, and the NASA administrators know this. It IS sad that people died, but they knew that the shuttle is not 100% reliable. It was built by the lowest bidder, from the cheapest parts, and from the cheapest labor that would get the job done.
-There were some replacement concepts for the shuttle. But because of congress' budgeting, the ideas were scrapped. About the only research being done by NASA in this area is on the linear aerospike engine. That's basically it.
-The shuttle is seen by NASA as something that won't last, but still has a good 30 years of life left. Though that attitude may have changed somewhat because of the Columbia destruction, that attitude will return after a few more STS missions where the shuttle leaves and returns safely.
-The shuttle has more than one million parts to it. Heck, the turbopump engines that are used in the shuttle main engines are some of the most technologically advanced and complex pieces of equipment ever built. Those fancy electric propulsion concepts like ION-F are simple in operation compared to an STS main engine. (Oh and don't say that electric concepts will work on earth... the pressure of the atmosphere keeps the gases from being ionized.)
-If you look at ALL of the vehicles that put objects into space, the shuttle has one of the better safety records. Which translates to why we don't use those other launch vehicles for manned flight - they are not rated for that use.
-Oh and back to the shuttle's age... the design is old. The parts that are used, and the standards that they were made to conform to, are nearly as old. Except for the replaceable/consumable items of course.
For the record: I actually AM a rocket scientist. Currently, I do modelling, simulation, embedded systems, and controls work for a small aerospace company (we're REALLY small). My background is in fluid mechanics and spacecraft propulsion though... this job is just holding me over for a bit.
Do you use the SPARC systems exclusively in your numerical math?
(I do some CFD. Just curious what others use. I run with several x86 systems in parallel. And when I was in school, I would use DEC Alphas.)
F&*K you. People died.
And for your info, I routinely work with radians per second. Not revolutions per second. I noted the difference. And because I routinely work with those units I read the report incorrectly.
though more dangerous because they tend to not shatter. Just spin one up, then lay it against a rail of some kind and watch it take off. It will curve slightly due to the Coriolis effect.
But I've seen them stick into trees...
I stand corrected. Didn't notice the extra 2pi in there (rev/s does not equal rad/s). *blushes*
Funny thing is that I'm actually a real live rocket scientist...:/
Yes. At that speed and altitude, the dynamic pressure on the piece of foam is in the neighborhood of 2900 psi... which comes to about 200 tons on a square foot. So if that piece of material had a face of it perpendicular to the direction the incoming fluid was travelling, that just happened to measure a square foot, you would have a force of 200 tons. I'd think that's enough to stop the foam which doesn't weigh very much. That's a rough number based on an educated guess as to how fast the shuttle was going.
The guy that made those comments isn't a rocket scientist. Just because someone works for NASA doesn't mean that they are a rocket scientist, nor that they have had any scientific training (think technicians).
Some people that work there do pure and applied math. Some do physics. And some, like the administrator of NASA Ames, have a background in radiation measurement. (Check his bio, as someone posted above.)
Plus, the guy is in management. Which brings me to another point. There are two kinds of engineers: the technical types (like me), and the management types. The technical types will sometimes debate the finer points of number theory, quantum physics, string theory, or fusion. The managerial types will have their eyes glaze over with that deer-in-the-headlights look when you mention any sort of equation.
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I believe so. I have always written my own runtime executable routines for the (limited) embedded sysetms work that I have done, so I'm not an expert on it. I was thinking more along the lines that QNX could give an idea of the memory footprints for Linux. ...
i nglinux03-long.php3
Okay, I went and did some checking, since I was curious anyways. It appears that a typical Linux kernal is 1.5 Mbytes. Too big for most real-time systems. On top of that, the kernel itself is a fairness scheduling algorithm, _and_ if a process is using the kernel resources, the process has to finish before the kernel is available for another process.
BUT! The kernel is modular (and open source!) so you could redo the algorithm, or take out modules to obtain something that has a scheduler more appropriate to real-time systems.
AND, the memory footprint of the kernal can be scaled down depending on what you need (or use) to about 300Kbytes for the kernal and about 100Kbytes for the file system, plus another 4Mbytes of RAM. If you include TCP/IP, it gets to be about twice as big. I got this information from here: http://www.lynuxworks.com/products/bluecat/faq/us
Even though that is one site, it appears that the info is conceivably possible.
Wouldn't QNX give you a good idea?
Why? Because there are countries and people that are opposed to the US, and will use warfare to achieve their goals. Think of it this way: you are a soldier (something few of the people on /. were, is my guess), and you are going into a battle. If you are facing the US military today, with all it's weapons, and superior technology, it's almost certain that you will be found and killed. What's that? You're hiding in some trees? That Apache pilot will turn on his FLiR and see you, then shoot you.
And say instead you are facing... Indian troops in a different situation. Their technology is less developed than the US. No fancy laser targeting, not much in the way of IR. Yeah, they still have bullets, mortars, grenades, artillery, and nukes... but if they can't see you, then they can't exactly shoot at you.
And if you are fighting someone that can rain fire down from the sky, without ever seeing them, then you are pretty much not willing to put up a fight.
Another reason to support weapons is to look at the parallel between the US and the Roman Empire in terms of military might. The Romans (in their day) were superior. They fought as a unit, with every soldier equipped with armor and weapons, and they had good training. The Romans didn't always win their battles, but they ALWAYS won the wars. _Until_ the Roman government put less emphasis on the military (went with conscripts and less-trained soldiers, instead of pros). That inevitably created a situation where Rome could fall, because the military could not hold the Empire together.
Now look at the US military, we've won most of the wars we've fought. The ones we've lost, we have identified the errors and corrected them. We also develop superior technology to make sure that we have the edge on the battlefield. If we did not have that edge, we would face whole nations opposed to our ideology.
Besides, if other nations (or persons) become more advanced and decide to attack us, are we going to fight with insults and our money?
As long as there are threats, the US will need to have a strong military. The weak do not go after the strong. That's a fact of life. And the rest of the world should be glad that the US is not in the business of building an empire.
Until you kill all the terrorists with your disposable machines. :p
Besides, bombers can never take ground. That's always going to be up to infantry.
These will be just another element to the military.
I'd hate to see a file that is actually pr0n, when you are downloading "chicken_soup.food".
Would that make the pr0n edible?
When it only takes a few days or weeks for someone to crack the protection scheme. I say let them keep putting out copy-protection schemes. Then laugh when their money goes down the drain. Either the copy-protection schemes will survive, or there won't be any copy-protection schemes. (Although I'm not a fan of warezing games... I'd just like to point that out.)
There is this thing called MIL-STD-461 which governs how much EMI a device aboard an aircraft can generate. It gives strict limits on how much EM leakage and susceptibility you can have... even for something as seemingly benign as a wire bundle. MIL-STD-462 governs how the devices should be tested. The other thing is that pretty much ALL personal electronic devices are class B devices (according to the FCC). So they can't generate interference onto other devices... Problem is that almost no personal electronic device has EM shielding, eddy current dissipation methods, or a way to attach to the plane's common ground. Personally I'd rather not have people using their cell phones or whatnot. Besides the noise, I'd rather not trust those $1 (US) RC filters used to dampen eddy currents.... which are actually just a 2 cent capacitor and a 2 cent resistor, but because it's validated against a specification it costs a LOT more. So as long as the FAA regulates that MIL-STD-461 has to be used, there is no way around the rule against certain electronic devices.
-It's design is probably older than most of the posters here on this forum. When it was originally concieved as a horizontal take-off and landing craft, it was assumed that the wings would provide enough lift to get the orbiter to orbit. That didn't work, because the shuttle by itself cannot carry enough fuel and still lift a usable payload. The delta wing that the shuttle uses has a L/D (lift-to-drag) ratio of something horrid... like 5. (A sailplane typically has an L/D of 25+. And your average Cesna 172 has an L/D of about 10. In any event, they needed more thrust, but the shuttle was already designed... so they had to slap some solid boosters on it. BUT! It turns out that having a multi-stage lift system is more efficient than a single-stage to orbit system in terms of how the thrust is used. SSTO concepts (Single Stage To Orbit) are researched because of the inherent simplicity in the system, and because technology has progressed enough that engineers feel comfortable working the numbers on the designs. (If you asked companies to build an SSTO 30 years ago, they'd have laughed at you... or asked for huge sums of money.)
-The shuttle is currently the only vehicle in the world that can lift the payloads that it does. It's literally a workhorse. It is THE perfect vehicle for missions to ISS. No other vehicle can do what the shuttle does now.
-The shuttle is still a test aircraft. People get complacent with the technology because they see it work so often. The shuttle crews know this, the people that work on them know this, and the NASA administrators know this. It IS sad that people died, but they knew that the shuttle is not 100% reliable. It was built by the lowest bidder, from the cheapest parts, and from the cheapest labor that would get the job done.
-There were some replacement concepts for the shuttle. But because of congress' budgeting, the ideas were scrapped. About the only research being done by NASA in this area is on the linear aerospike engine. That's basically it.
-The shuttle is seen by NASA as something that won't last, but still has a good 30 years of life left. Though that attitude may have changed somewhat because of the Columbia destruction, that attitude will return after a few more STS missions where the shuttle leaves and returns safely.
-The shuttle has more than one million parts to it. Heck, the turbopump engines that are used in the shuttle main engines are some of the most technologically advanced and complex pieces of equipment ever built. Those fancy electric propulsion concepts like ION-F are simple in operation compared to an STS main engine. (Oh and don't say that electric concepts will work on earth... the pressure of the atmosphere keeps the gases from being ionized.)
-If you look at ALL of the vehicles that put objects into space, the shuttle has one of the better safety records. Which translates to why we don't use those other launch vehicles for manned flight - they are not rated for that use.
-Oh and back to the shuttle's age... the design is old. The parts that are used, and the standards that they were made to conform to, are nearly as old. Except for the replaceable/consumable items of course.
For the record: I actually AM a rocket scientist. Currently, I do modelling, simulation, embedded systems, and controls work for a small aerospace company (we're REALLY small). My background is in fluid mechanics and spacecraft propulsion though... this job is just holding me over for a bit.
Do you use the SPARC systems exclusively in your numerical math? (I do some CFD. Just curious what others use. I run with several x86 systems in parallel. And when I was in school, I would use DEC Alphas.)
F&*K you. People died. And for your info, I routinely work with radians per second. Not revolutions per second. I noted the difference. And because I routinely work with those units I read the report incorrectly.
though more dangerous because they tend to not shatter. Just spin one up, then lay it against a rail of some kind and watch it take off. It will curve slightly due to the Coriolis effect. But I've seen them stick into trees...
I stand corrected. Didn't notice the extra 2pi in there (rev/s does not equal rad/s). *blushes* Funny thing is that I'm actually a real live rocket scientist... :/
It's not circumference times the rotational velocity. It's the RADIUS times the rotational velocity.
.06 m x 583.3 rotations / second (using his numbers) = 34.998 m/s = 114.8 fps = 78.3 mph.
So, for the standard CD thats:
If it really was going 220 m/s, that's a significant fraction of the speed of sound at sea level (340 m/s).
Yes. At that speed and altitude, the dynamic pressure on the piece of foam is in the neighborhood of 2900 psi... which comes to about 200 tons on a square foot. So if that piece of material had a face of it perpendicular to the direction the incoming fluid was travelling, that just happened to measure a square foot, you would have a force of 200 tons. I'd think that's enough to stop the foam which doesn't weigh very much. That's a rough number based on an educated guess as to how fast the shuttle was going.
The guy that made those comments isn't a rocket scientist. Just because someone works for NASA doesn't mean that they are a rocket scientist, nor that they have had any scientific training (think technicians). Some people that work there do pure and applied math. Some do physics. And some, like the administrator of NASA Ames, have a background in radiation measurement. (Check his bio, as someone posted above.) Plus, the guy is in management. Which brings me to another point. There are two kinds of engineers: the technical types (like me), and the management types. The technical types will sometimes debate the finer points of number theory, quantum physics, string theory, or fusion. The managerial types will have their eyes glaze over with that deer-in-the-headlights look when you mention any sort of equation.