Early mission plans for Prometheus 1 (Jupiter Icy Moons Orbiter) indicate that the spacecraft would orbit Callisto, Ganymede, and Europa individually, and perhaps have a lifespan of about 20 years."
Looks like those "early mission plans" have been revised. See the second half of this article. Here's the relevant paragraph:
JIMO, whose launch had already been pushed back from around 2012 to 2015, faced what NASA called "concerns over costs and technical complexity," leading the agency to effectively cancel the mission. JIMO was intended to be the cornerstone of Project Prometheus, a nuclear power and propulsion program; NASA will instead seek a less-complex alternative mission to demonstrate those technologies.
It's a shame Hubble is our only orbiting telescope.
There's more to the electromagnetic spectrum than visible light you know. The Hubble Space Telescope is only one of NASA's four orbiting "Grand Observatories". Here are links to info about the other telescopes.
The last time I watched the original V miniseries a few years ago, my friends and I had just finished taking an "Introduction to Theater" class in college. We were stunned that several scenes in the show seemed to be lifted, almost word for word, from "Fear and Misery in the Third Reich" by Berthold Brecht. The play, written in the late 1930's, was a collection of several short scenes which showed how the Nazis slowly corrupted life in Germany.
I did a quick Google search for "V the miniseries" and "Fear and Misery in the Third Reich" and didn't get any hits. I checked the credits listed in V's entry in the IMDB, and couldn't find any credit given to Brecht.
Anybody out there know more about this? Were parts of V openly adapted from this play, or are the similarities I saw a coincidence (or something shadier?)
Sorry to disappoint you, but Pontiac doesn't make the Firebird OR the Firebird Trans-Am anymore. Somewhere, David Hasselhof and Burt Reynolds are quietly weeping, mourning the passage of their valiant steeds.
2002 was the last model year any of these cars were built. The same goes for the Chevy Camaro.
Actually, the (co-)author of the article and the/. submitter appear to be one and the same person.
I suppose there's nothing wrong with a little self-promotion. It's not as if he tried to hide the fact that he was submitting his own article ("Over at eWEEK, we believe we've got the drop on the...").
Re:Straight line vs. cornering
on
Landshark
·
· Score: 1
If you are breaking hard, or breaking in a turn, the pressure goes forward and can be unstable. A typical manouver if you are offroading.
If you are accelerating in a turn, a common manouver while racing, then the pressure goes to the rear of the vehicle.
Actually, I would think that both braking (hopefully not "breaking") and acceleration while cornering is typical for a race car. The driver will be braking heavily while decelerating into the corner, then once past the apex of the curve, it's back on the gas to accelerate away from the corner.
So I think for most racing applications (barring straight-line speed record attempts or drag racing), the conventional four-wheeled configuration is the way to go.
"It seems ludicrous to imagine that a spaceship could ascend into orbit and beyond by riding the impulses produced by a series of external atomic explosions...."
That's because it IS ludicrous, at least the "ascend into orbit" part. It has been a while since I read anything about Project Orion, but I'm pretty confident that this propulsion technique was intended for use only in space. The spacecraft would most likely have been assembled in orbit, or possibly launched from Earth by one mother of a big chemical rocket.
I can testify to the poor maintenance and operation of the coasters on New Jersey piers. I spent a weekend in Wildwood, NJ, about 10 years ago. My brother and I spent a lot of time on the amusement piers. On one roller coaster, a wooden one with only lap bars to restrain the passengers, the guy running the ride started the train rolling before the lap bars were locked down. All the passengers started screaming, and the operator stopped the train. On another coaster, the ride vibrated and rattled excessively, much worse than any old rickety wooden coaster I've ever ridden, even though this ride was a steel looping coaster. My head was bouncing back and forth pretty hard against the head restraints. My guess is that the amusement pier was not entirely stable, and that the pilings had sunk or shifted since the coaster was built.
I'm not sure how I feel about the proposed G-limiting law in the article, but I am all for tighter inspections and safety regulations for rides like these.
I always kind of wondered... Why did Scotty even need the aluminum to be transparent? They could've carried the whale in a regular aluminum tank.:)
You missed the point. Scotty needed to acquire large plexiglass panels from that factory manager guy (Scotty: "How thick would one of your panels have to be to withstand the pressure of...[whatever numbers he quoted]?" factory guy: "That's easy, 6 inches. We carry stuff that big in stock." Scotty: "Aye, I noticed."). Unfortunately, having freshly arrived from the 23rd Century, the Enterprise crew was a little short on cash. Scotty gave the guy the formula for transparent aluminum in exchange for the plexiglass panels (Scotty: "Is it worth something to ya, laddy, or shall I just punch up clear?")
Except that they used two engines, counter-rotating to negate gyro effects, and the pilot was between them.
Wrong.
The original Wright Flyer only had one engine that turned two propellors driven by chains from the engine (not too surprising, given the Wright Bros. primary occupation at the time). You are correct that the two propellors did counter-rotate, though.
Maybe realistic wasn't the best choice of words. As has been pointed out in other comments, the important thing is that the physics model be consistent so the motion is predictable and "feels right" to the player. Certainly, there is room to make simplifying assumptions, such as assuming uniform gravity fields (in your example).
I think you missed my point about the necessity of at times using some form of numerical integration to model physics in a game. Returning to the "space battle" example we've been using, I agree that no integration, Runge-Kutta or otherwise, is required to represent the motion of planets, or missiles moving in a straight line. What about motion of the player-controlled spaceship, though? There are several ways this motion can be modelled:
The simplest approach is something like "If joystick goes right, spaceship goes right". This is how ancient games like Defender and countless other side-scrolling shoot-em-ups worked. If this is the approach you want to take, there is no need to perform any complex numerical integrations.
What if you want to add another layer of complexity, or (dare I say?) realism, to the game. What if joystick motion controlled the amount of thrust produced by engines on the spaceship? In this case, the joystick is essentially controlling acceleration of the spaceship, through the forces created by the thrusters. To get velocity and position from this information, some form of numerical integration is required. A closed-form solution (like for the planets or missiles) is not an option, since the forces acting on the spaceship (joystick input) are not known explicitly. It doesn't have to be a full-blown 4th-order Runge-Kutta solution, but some form of numerical integration is necessary. A simple trapezoidal rule might do nicely.
The necessity of calculating the forces acting on an object and integrating to find position becomes even more obvious in a less celestial environment, like a flight simulator. Unless you want to dogfight like the planes did in Combat! for the Atari 2600:)
Using the closed-form solutions is all well and good if you are simulating a fairly static universe. In an interactive game, player actions and inputs are going to influence the game universe. Using closed form solutions in the physics model quickly becomes impossible, and some form of numerical integration is required.
In other words, with closed-form solutions, you can have your planet moving in an ellipse in the background, while the player's space ship fires missiles which move in a straight line. But how do you model the motion of the player-controlled space ship realistically?
Non-gradient based optimization techniques such as genetic algorithms typically require many, many iterations, trying many different genetic combinations over many "generations" before obtaining an "optimal" solution. Are club-goers to be subjected to hours of crappy music in order for the computerized DJ to figure out what the crowd likes?
In this CNET article about the release of Intel's Linux compilers, they quoted the purchase price as $399 for a download, $499 for a CD. Somebody should tell them that blank CDs are a lot cheaper than they used to be...
(I know, I know. The boxed version probably also comes with some printed documentation, supposedly justifying the higher price. It still seemed funny to me..)
Now, suppose we put a satellite at, let's say, 43630 km from the surface. Gravity still works at this height. So you can still put an object in orbit. And suppose we set it moving in an orbit parallel to the lower satellite at a speed of, ooooh, about, 13127 km/h. What then?
Kepler and Newton are spinning in their graves.
I'm to lazy to actually do the math, but your second satellite will not stay in your nice circular orbit. Instead, it will probably take up some eccentric, decidedly NON-geosynchronous orbit.
You can not maintain a circular orbit at an arbitrary altitude at an arbitrary velocity. Think of a ball tied to a string being swung around in a circle. The tension in the string is providing a centripetal acceleration that is maintaining the cirular path of the spinning ball (An observer on the ball might call this a "centrifugal force"). What is keeping your satellite in orbit? GRAVITY, of course. And the gravitational force (the "string" that is holding your satellite in its orbit) is inversely proportional to the square of the distance between the satellite and the center of the earth. So if your second satellite is orbiting at a higher altitude, the gravitational force acting on the satellite will be reduced. Thus, to remain in a circular orbit, your second satellite would have to be travelling slower, in order for the reduced gravitational force to still be providing enough centripetal acceleration to maintain a circular orbit.
Think of it this way: for an object to stay in a circular orbit, the gravitational force on the object must exactly balance the "centrifugal force" on the object (there really is no such thing as "centrifugal force", but this is an easy way to think about it). If an object moves faster around that orbit, the "centrifugal force" will increase, but the gravitational force remains constant, so the object would tend to drift outwards from its original orbit. So for each altitude, there is a specific orbital velocity required to maintain that circular orbit. Geosynchronous orbit is the ONE specific altitude for which the associated orbital velocity will keep the satellite orbiting the earth every 23 hours and 56 minutes.
If Microsoft wants to charge for their operating systems, let them. If I don't want to buy it, I won't.
That's the whole problem. If MS is able to coerce OEMs into not selling "Naked PCs", you'll have no choice but to buy an MS operating system when you purchase new hardware.
Re:Just what my toaster and coffee maker need!
on
Microcontroller Linux
·
· Score: 1
# make coffee -strength 10 -cups 3
Wow, I can't believe you have to recompile your coffee every time you make a new pot. Things like coffee strength or number of cups should really be run-time (brew-time?) options that you could put in your.coffeerc file or something.
I would have moderated this as (Funny), rather than (Insightful). But since someone took your suggestion seriously, I'll respond seriously.
The problem with your suggestion is that you're not addressing the fundamental issue of what constitutes "lewd stuff". If there was a program monitoring viewers' internet activity, waiting to "blow the whistle" if it detected porn, and could sucessfully identify porn or other objectionable material as such, it could just as easily block access to that content, and we wouldn't be having this discussion.
Of course, maybe having the "PORN ALERT!!!" siren go off when someone is looking for breast cancer information is better than preventing the person from accessing the information altogether. But I bet he or she won't learn very much with all the bright light and noise, not to mention the funny looks from other patrons.
The problem then became that M$ reserved the rights to change the contracts when software got updated and the rights to extend these contracts whenever they felt like it.
[Billy Dee]: "That was never part of our deal!"
[Billy G. (on a respirator)]: "Perhaps you feel you are being treated unfairly? It would be unfortunate if I had to change our file formats again, forcing another pointless upgrade cycle."
[Billy Dee]: "This deal is getting worse all the time! I need a Colt 45."
These things need to be simplified. There shouldn't be ANY work to play your favorite game. There shouldn't be ANY work to use your desktop. Everything should be still accessible by experts if they prefer to do it the tedious way too. Do linux developers believe that simple is evil or something? There is some SERIOUS UI attention needed in the desktop.
Assuming that World Domination is the ultimate goal for Linux development, I suppose you are correct.
I figure Mandrake, Corel, Redhat, etc are leaning towards this route. Though they are becoming bloatware too.
Well, you can't have your cake and eat it, too. If you try to replace Windows as the computing platform of choice for the unwashed masses, I'm afraid that a certain amount of 'bloat' will be unavoidable.
Slashdot Mirror
Wow, the pedants on Slashdot must be slacking off today. I guess it's left to me to point out that in binary, 1+1=10, not 11.
Don't forget (1.a) Capable of bringing a shitload of material back from orbit, something that the new system definitely can't do.
And to head off other grammar Nazis, it's "too", not "two".
Looks like those "early mission plans" have been revised. See the second half of this article. Here's the relevant paragraph:
Not to nitpick, but Apollo 8 was the first mission to circle the moon. So that crew witnessed the first ever 'Earthrise', not the Apollo 11 crew.
Here's a picture from the Apollo 8 Image Gallery.
There's more to the electromagnetic spectrum than visible light you know. The Hubble Space Telescope is only one of NASA's four orbiting "Grand Observatories". Here are links to info about the other telescopes.
The last time I watched the original V miniseries a few years ago, my friends and I had just finished taking an "Introduction to Theater" class in college. We were stunned that several scenes in the show seemed to be lifted, almost word for word, from "Fear and Misery in the Third Reich" by Berthold Brecht. The play, written in the late 1930's, was a collection of several short scenes which showed how the Nazis slowly corrupted life in Germany.
I did a quick Google search for "V the miniseries" and "Fear and Misery in the Third Reich" and didn't get any hits. I checked the credits listed in V's entry in the IMDB, and couldn't find any credit given to Brecht.
Anybody out there know more about this? Were parts of V openly adapted from this play, or are the similarities I saw a coincidence (or something shadier?)
Sorry to disappoint you, but Pontiac doesn't make the Firebird OR the Firebird Trans-Am anymore. Somewhere, David Hasselhof and Burt Reynolds are quietly weeping, mourning the passage of their valiant steeds.
2002 was the last model year any of these cars were built. The same goes for the Chevy Camaro.
I suppose there's nothing wrong with a little self-promotion. It's not as if he tried to hide the fact that he was submitting his own article ("Over at eWEEK, we believe we've got the drop on the ...").
So I think for most racing applications (barring straight-line speed record attempts or drag racing), the conventional four-wheeled configuration is the way to go.
That's because it IS ludicrous, at least the "ascend into orbit" part. It has been a while since I read anything about Project Orion, but I'm pretty confident that this propulsion technique was intended for use only in space. The spacecraft would most likely have been assembled in orbit, or possibly launched from Earth by one mother of a big chemical rocket.
I can testify to the poor maintenance and operation of the coasters on New Jersey piers. I spent a weekend in Wildwood, NJ, about 10 years ago. My brother and I spent a lot of time on the amusement piers. On one roller coaster, a wooden one with only lap bars to restrain the passengers, the guy running the ride started the train rolling before the lap bars were locked down. All the passengers started screaming, and the operator stopped the train. On another coaster, the ride vibrated and rattled excessively, much worse than any old rickety wooden coaster I've ever ridden, even though this ride was a steel looping coaster. My head was bouncing back and forth pretty hard against the head restraints. My guess is that the amusement pier was not entirely stable, and that the pilings had sunk or shifted since the coaster was built.
I'm not sure how I feel about the proposed G-limiting law in the article, but I am all for tighter inspections and safety regulations for rides like these.
You missed the point. Scotty needed to acquire large plexiglass panels from that factory manager guy (Scotty: "How thick would one of your panels have to be to withstand the pressure of ...[whatever numbers he quoted]?" factory guy: "That's easy, 6 inches. We carry stuff that big in stock." Scotty: "Aye, I noticed."). Unfortunately, having freshly arrived from the 23rd Century, the Enterprise crew was a little short on cash. Scotty gave the guy the formula for transparent aluminum in exchange for the plexiglass panels (Scotty: "Is it worth something to ya, laddy, or shall I just punch up clear?")
Wrong.
The original Wright Flyer only had one engine that turned two propellors driven by chains from the engine (not too surprising, given the Wright Bros. primary occupation at the time). You are correct that the two propellors did counter-rotate, though.
Maybe realistic wasn't the best choice of words. As has been pointed out in other comments, the important thing is that the physics model be consistent so the motion is predictable and "feels right" to the player. Certainly, there is room to make simplifying assumptions, such as assuming uniform gravity fields (in your example).
I think you missed my point about the necessity of at times using some form of numerical integration to model physics in a game. Returning to the "space battle" example we've been using, I agree that no integration, Runge-Kutta or otherwise, is required to represent the motion of planets, or missiles moving in a straight line. What about motion of the player-controlled spaceship, though? There are several ways this motion can be modelled:
The simplest approach is something like "If joystick goes right, spaceship goes right". This is how ancient games like Defender and countless other side-scrolling shoot-em-ups worked. If this is the approach you want to take, there is no need to perform any complex numerical integrations.
What if you want to add another layer of complexity, or (dare I say?) realism, to the game. What if joystick motion controlled the amount of thrust produced by engines on the spaceship? In this case, the joystick is essentially controlling acceleration of the spaceship, through the forces created by the thrusters. To get velocity and position from this information, some form of numerical integration is required. A closed-form solution (like for the planets or missiles) is not an option, since the forces acting on the spaceship (joystick input) are not known explicitly. It doesn't have to be a full-blown 4th-order Runge-Kutta solution, but some form of numerical integration is necessary. A simple trapezoidal rule might do nicely.
The necessity of calculating the forces acting on an object and integrating to find position becomes even more obvious in a less celestial environment, like a flight simulator. Unless you want to dogfight like the planes did in Combat! for the Atari 2600 :)
Using the closed-form solutions is all well and good if you are simulating a fairly static universe. In an interactive game, player actions and inputs are going to influence the game universe. Using closed form solutions in the physics model quickly becomes impossible, and some form of numerical integration is required.
In other words, with closed-form solutions, you can have your planet moving in an ellipse in the background, while the player's space ship fires missiles which move in a straight line. But how do you model the motion of the player-controlled space ship realistically?
Non-gradient based optimization techniques such as genetic algorithms typically require many, many iterations, trying many different genetic combinations over many "generations" before obtaining an "optimal" solution. Are club-goers to be subjected to hours of crappy music in order for the computerized DJ to figure out what the crowd likes?
Too late.
I don't know about the other NASA research centers, but I know that at Ames and Langley, there are a lot of Macs in use as desktop workstations.
Why would you buy The Hobbit Millenium Edition, when The Hobbit XP is going to be released in a matter of weeks?
In this CNET article about the release of Intel's Linux compilers, they quoted the purchase price as $399 for a download, $499 for a CD. Somebody should tell them that blank CDs are a lot cheaper than they used to be...
(I know, I know. The boxed version probably also comes with some printed documentation, supposedly justifying the higher price. It still seemed funny to me..)
Kepler and Newton are spinning in their graves.
I'm to lazy to actually do the math, but your second satellite will not stay in your nice circular orbit. Instead, it will probably take up some eccentric, decidedly NON-geosynchronous orbit.
You can not maintain a circular orbit at an arbitrary altitude at an arbitrary velocity. Think of a ball tied to a string being swung around in a circle. The tension in the string is providing a centripetal acceleration that is maintaining the cirular path of the spinning ball (An observer on the ball might call this a "centrifugal force"). What is keeping your satellite in orbit? GRAVITY, of course. And the gravitational force (the "string" that is holding your satellite in its orbit) is inversely proportional to the square of the distance between the satellite and the center of the earth. So if your second satellite is orbiting at a higher altitude, the gravitational force acting on the satellite will be reduced. Thus, to remain in a circular orbit, your second satellite would have to be travelling slower, in order for the reduced gravitational force to still be providing enough centripetal acceleration to maintain a circular orbit.
Think of it this way: for an object to stay in a circular orbit, the gravitational force on the object must exactly balance the "centrifugal force" on the object (there really is no such thing as "centrifugal force", but this is an easy way to think about it). If an object moves faster around that orbit, the "centrifugal force" will increase, but the gravitational force remains constant, so the object would tend to drift outwards from its original orbit. So for each altitude, there is a specific orbital velocity required to maintain that circular orbit. Geosynchronous orbit is the ONE specific altitude for which the associated orbital velocity will keep the satellite orbiting the earth every 23 hours and 56 minutes.
That's the whole problem. If MS is able to coerce OEMs into not selling "Naked PCs", you'll have no choice but to buy an MS operating system when you purchase new hardware.
Wow, I can't believe you have to recompile your coffee every time you make a new pot. Things like coffee strength or number of cups should really be run-time (brew-time?) options that you could put in your .coffeerc file or something.
I would have moderated this as (Funny), rather than (Insightful). But since someone took your suggestion seriously, I'll respond seriously.
The problem with your suggestion is that you're not addressing the fundamental issue of what constitutes "lewd stuff". If there was a program monitoring viewers' internet activity, waiting to "blow the whistle" if it detected porn, and could sucessfully identify porn or other objectionable material as such, it could just as easily block access to that content, and we wouldn't be having this discussion.
Of course, maybe having the "PORN ALERT!!!" siren go off when someone is looking for breast cancer information is better than preventing the person from accessing the information altogether. But I bet he or she won't learn very much with all the bright light and noise, not to mention the funny looks from other patrons.
[Billy G. (on a respirator)]: "Perhaps you feel you are being treated unfairly? It would be unfortunate if I had to change our file formats again, forcing another pointless upgrade cycle."
[Billy Dee]: "This deal is getting worse all the time! I need a Colt 45."