The worst example of unthinking de-orbiting was Mir. There you had many, many tons of aerospace-grade titanium, aluminum, and steel in orbit. Everybody talked of either continuing to man and maintain Mir, or burning it in. No one considered the third and best option: boost it to a higher orbit where atmospheric drag is neglibile, and wait patiently until it becomes an incredibly valuable resource of raw materials for on-orbit industry.
High sustained winds during the parachute descent would indeed accelerate the lander as you described.
OTOH, you repeated the "150 mph" speed which is a figure I frankly pulled out of my butt.:) I don't know how often, if ever, 150 mph winds are encountered on Mars.
the power needed to run the wiper could conceivably be more than the power lost due to the dust and transporting the extra weight to Mars.
More likely, if instead of adding wipers that weigh say half a kilogram, you use that half-kilogram to increase the surface area of the solar panels a little, you'll be ahead of the game.
Really? If I couldn't afford a newer computer, I would gladly accept a donation of a 486, if the alternative was not owning a computer at all -- which is the situation most Africans are in.
Martian dust storms are not the big deal many people imagine they are. We're used to hurricanes, able to generate winds so strong that people are literally blown off their feet. And a few months ago we heard soldiers describe sandstorms in Iraq, where grains of sand are whipped against your skin so hard that it stings like hell.
On Mars however, the atmosphere is so thin that storm effects are quite different. The dust raised by these storms consists of tiny talcum-powder-sized particles. These thin winds would never have the "oomph" to pick up a grain of sand.
And a "raging" 150 mph wind on Mars would not be able to knock a person on his or her butt. It would only carry as much force as a relatively gentle 18 mph Earth wind.
The only possible ill-effect from a dust storm, is that a thin layer of dust might coat the lander's solar panel and reduce its efficiency by a few percent. (Not enough to prevent the lander from phoning home, though.)
The failure of most of the recent Mars landers is espcially strange when you consider that two of the three successful landings, Viking 1 and Viking 2, were built with 1960s technology. (Yes, they landed in 1976, but the latest kit takes years to become space-qualified.)
You'd think that spacecraft designed with 1990s tech would be more reliable than the Vikings.
Hydrogen -- it's something you *can* mine
on
Global Dimming
·
· Score: 1
The most promising source of the hydrogen may be geological "traps" similar to those now drilled for natural gas. Professor Freund said: "One of these natural hydrogen fields is already known to exist in North America, and extends from Canada to Kansas."
Wide screens are great for watching DVDs. But the aspect ratio is *exactly wrong* for viewing web pages and word processing, which almost always call for a portrait orientation rather than landscape. When you put Word in "Whole Page" view mode on a landscape-oriented display, a ton of screen real estate is wasted.
What we really need is for all IT departments to shell out the few extra bucks for pivoting displays.
People who work with computers remain fixated on efficiency. Every week I hear the debates over whether businesses should use Linux or Windows, the commentators always wrangling over which systems will save the most money. I find this battle increasingly tiresome. I'm more interested in finding the systems that will put more people to work.
If Andy wants to have a ditch dug, he could hire one man with a backhoe, twelve men with shovels, or 300 men with teaspoons. According to his rationale, hiring the teaspoon-equipped men would be the best solution.
WRONG!
If everyone did business in that manner, our GDP would be miniscule. Almost everyone would be living in poverty and squalor.
Each labor-saving device means the idling of thousands of people, wasting their years of experience, rigorous training, and practical insights.
Yes, new technologies can be quite disruptive in the short term. But in the long term they cause amazing increases in the standard of living of EVERYONE. (E.g., today there are millions of people employed in the auto industry today -- far more than were ever employed in the horse-carriage industry. But if Andy had his way, the auto industry would have been considered the enemy because it imperiled the jobs of the horse-carriage makers.) He should try to grasp basic economics before writing another article like this.
Actually, Bush Sr. proposed a manned mission to Mars. Would have been quite an exciting endeavor, but the public today just lacks the imagination to support such a program, unlike during the Apollo era.
I would expect that once you get the cable past 36,000 km above the earth the cable would mostly pull itself up from that point on.
Your understanding is pretty close.
What will actually happen is that a big "spool" of ribbon will be launched into geosynch orbit. Shortly after you begin to deploy the ribbon out of the spool, the "gravity gradient" effect will create tension in the ribbon, and it will actually begin to pull itself out of the spool. To date, experimental space tethers have only been a few km long and generated a relatively modest tension. But a tether long enough to reach Earth's surface will generate high tension; the "spool" will have to contain a powerful brake to keep the ribbon from unreeling itself at out-of-control speeds.
Keep in mind that as the ribbon deploys in one direction, the spool will automagically move in the opposite direction, such that the system's center of mass remains in geosynch orbit. That's why the overall length of the ribbon must be longer than the altitude of geosynch orbit. (And that's a big bonus for launching an interplanetary vehicle; it can ride the elevator to a point well above geosynch orbit.)
you have to use the cable for propulsion, otherwise you have just invented a strange kind of tethered rocked and you are not saving any energy.
It's not "a strange kind of tethered rocked." Not by a longshot.
First of all, the elevator, unlike a rocket, need not carry any propellant. Right there you have reduced the size and complexity of the vehicle by 97%. Do a little research on the "rocket equation," and learn how the need to accelerate tons of propellant to hypersonic speeds leads to exponential increases in vehicle size, as well as the need for complex staging mechanisms.
It also need not carry its own energy source. Power will be beamed to the vehicle by laser or microwave.
A final way to realize the elevator's superiority to a rocket is to consider that 100% of the energy expended by the elevator serves to increase the elevator's potential energy in the earth's gravitational field. But not all of the energy expended by a rocket increases the rocket's potential energy -- especially when it has just left the pad and is traveling slowly. In the extreme case, consider how a rocket needs to expend enormous amounts of energy just to "hover" at a constant altitude. The elevator, on the other hand, can simply clamp on to the ribbon and hang there, expending zero energy to hover.
with a 1/10 g acceleration you will reach the top of the "elevator" in less than 6 hours
Another poster hypothesized that the "track mechanism will presumably be some sort of magnetic suspension," thus speeds must be kept down to 400 - 500 km/h, to prevent a catastrophic failure in case the vehicle brushes against the nanotube ribbon.
For all I know, the "track mechanism" may be even simpler than that -- such as opposing rubber wheels tightly gripping the ribbon. (I wish I could be at that conference to see what mechanisms are actually being proposed!) In which case speeds will also have to be kept pretty low in order to prevent damage to the ribbon.
the descent stage needs no power. However, apparantly venting heat will be a problem at high speeds.
I don't see why the principle of "regenerative braking," used by most other electric vehicles, couldn't be used to generate power as the elevator descends. While it may be impractical to store this energy on board, it could be beamed by laser or microwave to the station at the base of the elevator, or to an ascending car on a nearby elevator.
No need for the elevator to radiate lots of waste heat like a Pentium!
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Your thesis, that all longstanding bureaucracies are impossible to reform or streamline, is depressing and seems overly pessimistic.
Is there anything in the theory of management of large organizations to back up your claim?
What the heck are you talking about?
The worst example of unthinking de-orbiting was Mir. There you had many, many tons of aerospace-grade titanium, aluminum, and steel in orbit. Everybody talked of either continuing to man and maintain Mir, or burning it in. No one considered the third and best option: boost it to a higher orbit where atmospheric drag is neglibile, and wait patiently until it becomes an incredibly valuable resource of raw materials for on-orbit industry.
http://www.snopes.com/quotes/bush.htm
High sustained winds during the parachute descent would indeed accelerate the lander as you described.
:) I don't know how often, if ever, 150 mph winds are encountered on Mars.
OTOH, you repeated the "150 mph" speed which is a figure I frankly pulled out of my butt.
the power needed to run the wiper could conceivably be more than the power lost due to the dust and transporting the extra weight to Mars.
More likely, if instead of adding wipers that weigh say half a kilogram, you use that half-kilogram to increase the surface area of the solar panels a little, you'll be ahead of the game.
Really? If I couldn't afford a newer computer, I would gladly accept a donation of a 486, if the alternative was not owning a computer at all -- which is the situation most Africans are in.
What makes you think differently about this?
IAAAE (I am an Aerospace Engineer.)
Martian dust storms are not the big deal many people imagine they are. We're used to hurricanes, able to generate winds so strong that people are literally blown off their feet. And a few months ago we heard soldiers describe sandstorms in Iraq, where grains of sand are whipped against your skin so hard that it stings like hell.
On Mars however, the atmosphere is so thin that storm effects are quite different. The dust raised by these storms consists of tiny talcum-powder-sized particles. These thin winds would never have the "oomph" to pick up a grain of sand.
And a "raging" 150 mph wind on Mars would not be able to knock a person on his or her butt. It would only carry as much force as a relatively gentle 18 mph Earth wind.
The only possible ill-effect from a dust storm, is that a thin layer of dust might coat the lander's solar panel and reduce its efficiency by a few percent. (Not enough to prevent the lander from phoning home, though.)
The failure of most of the recent Mars landers is espcially strange when you consider that two of the three successful landings, Viking 1 and Viking 2, were built with 1960s technology. (Yes, they landed in 1976, but the latest kit takes years to become space-qualified.)
You'd think that spacecraft designed with 1990s tech would be more reliable than the Vikings.
From the Vancouver Sun,
The most promising source of the hydrogen may be geological "traps" similar to those now drilled for natural gas. Professor Freund said: "One of these natural hydrogen fields is already known to exist in North America, and extends from Canada to Kansas."
I'd imagine this is the last actual handspring release, before they fully merge with Palm.
Is this analagous to when Apple bought out Power Computing?
Wide screens are great for watching DVDs. But the aspect ratio is *exactly wrong* for viewing web pages and word processing, which almost always call for a portrait orientation rather than landscape. When you put Word in "Whole Page" view mode on a landscape-oriented display, a ton of screen real estate is wasted.
What we really need is for all IT departments to shell out the few extra bucks for pivoting displays.
Google ought to do complex Boolean queries like
(potato or potatoe) and ((fried or mashed) and gravy)
It's my only peeve about that wonderful search engine.
Thank you for recognizing the brilliance of Marble Madness. I couldn't have written a more loving tribute to the game.
Tip: when playing Marble Madness with MAME or MacMAME, connect your computer to a high-powered sound system with subwoofer : )
Virtual PC lets me copy and paste between Windows and Mac environments.
People who work with computers remain fixated on efficiency. Every week I hear the debates over whether businesses should use Linux or Windows, the commentators always wrangling over which systems will save the most money. I find this battle increasingly tiresome. I'm more interested in finding the systems that will put more people to work.
If Andy wants to have a ditch dug, he could hire one man with a backhoe, twelve men with shovels, or 300 men with teaspoons. According to his rationale, hiring the teaspoon-equipped men would be the best solution.
WRONG!
If everyone did business in that manner, our GDP would be miniscule. Almost everyone would be living in poverty and squalor.
Each labor-saving device means the idling of thousands of people, wasting their years of experience, rigorous training, and practical insights.
Yes, new technologies can be quite disruptive in the short term. But in the long term they cause amazing increases in the standard of living of EVERYONE. (E.g., today there are millions of people employed in the auto industry today -- far more than were ever employed in the horse-carriage industry. But if Andy had his way, the auto industry would have been considered the enemy because it imperiled the jobs of the horse-carriage makers.) He should try to grasp basic economics before writing another article like this.
GBush I didn't do diddly for NASA either.
Actually, Bush Sr. proposed a manned mission to Mars. Would have been quite an exciting endeavor, but the public today just lacks the imagination to support such a program, unlike during the Apollo era.
They cite three injuries, "one requiring stiches," in 6000 units. This sounds a lot safer than motorcycles. Why haven't all motorcycles been recalled?
most of the sky is ignored and there is no solution to moving a huge asteroid just a little bit to avoid collision with the Earth or the moon.
:)
Who cares if a huge asteroid hits the moon? That would be fun to watch
Well, as long as it isn't so huge that it causes the moon to break apart. That might prove hazardous to us earthlings.
I would expect that once you get the cable past 36,000 km above the earth the cable would mostly pull itself up from that point on.
Your understanding is pretty close.
What will actually happen is that a big "spool" of ribbon will be launched into geosynch orbit. Shortly after you begin to deploy the ribbon out of the spool, the "gravity gradient" effect will create tension in the ribbon, and it will actually begin to pull itself out of the spool. To date, experimental space tethers have only been a few km long and generated a relatively modest tension. But a tether long enough to reach Earth's surface will generate high tension; the "spool" will have to contain a powerful brake to keep the ribbon from unreeling itself at out-of-control speeds.
Keep in mind that as the ribbon deploys in one direction, the spool will automagically move in the opposite direction, such that the system's center of mass remains in geosynch orbit. That's why the overall length of the ribbon must be longer than the altitude of geosynch orbit. (And that's a big bonus for launching an interplanetary vehicle; it can ride the elevator to a point well above geosynch orbit.)
you have to use the cable for propulsion, otherwise you have just invented a strange kind of tethered rocked and you are not saving any energy.
It's not "a strange kind of tethered rocked." Not by a longshot.
First of all, the elevator, unlike a rocket, need not carry any propellant. Right there you have reduced the size and complexity of the vehicle by 97%. Do a little research on the "rocket equation," and learn how the need to accelerate tons of propellant to hypersonic speeds leads to exponential increases in vehicle size, as well as the need for complex staging mechanisms.
It also need not carry its own energy source. Power will be beamed to the vehicle by laser or microwave.
A final way to realize the elevator's superiority to a rocket is to consider that 100% of the energy expended by the elevator serves to increase the elevator's potential energy in the earth's gravitational field. But not all of the energy expended by a rocket increases the rocket's potential energy -- especially when it has just left the pad and is traveling slowly. In the extreme case, consider how a rocket needs to expend enormous amounts of energy just to "hover" at a constant altitude. The elevator, on the other hand, can simply clamp on to the ribbon and hang there, expending zero energy to hover.
with a 1/10 g acceleration you will reach the top of the "elevator" in less than 6 hours
Another poster hypothesized that the "track mechanism will presumably be some sort of magnetic suspension," thus speeds must be kept down to 400 - 500 km/h, to prevent a catastrophic failure in case the vehicle brushes against the nanotube ribbon.
For all I know, the "track mechanism" may be even simpler than that -- such as opposing rubber wheels tightly gripping the ribbon. (I wish I could be at that conference to see what mechanisms are actually being proposed!) In which case speeds will also have to be kept pretty low in order to prevent damage to the ribbon.
the descent stage needs no power. However, apparantly venting heat will be a problem at high speeds.
I don't see why the principle of "regenerative braking," used by most other electric vehicles, couldn't be used to generate power as the elevator descends. While it may be impractical to store this energy on board, it could be beamed by laser or microwave to the station at the base of the elevator, or to an ascending car on a nearby elevator.
No need for the elevator to radiate lots of waste heat like a Pentium!
Here's some info about running Linux on Macs:
i d=6918320
/ 0259234&mode=thread&tid=106&tid=126&tid=137&tid=17 4&tid=181&tid=185
http://apple.slashdot.org/comments.pl?sid=77884&c
http://apple.slashdot.org/article.pl?sid=03/09/10
http://www.terrasoftsolutions.com/
http://www.yellowdoglinux.com/
North Korea and terrorist states could develop ICBM capabilities
Um, North Korea is developing ICBMs.