The amount of (angular) momentum that has to be transferred is quite large, but you can transfer it over a long time (days), so the sideways force on the tether attachment point is small.
If you don't believe me just check out the publications of highlift systems or any other paper on space elevators. They never mention propulsion because it is not nessecary.
A tether that is not in contact with the ground would indeed need propulsion.
But in all designs I know there is a contact between tether and ground. Since the tether is bent slightly backwards by the coriolis force of the upward-moving climber, there is a force component at the anchor point that is parallel to the motion of the attachment point, so angular momentum is transferred.
Since the payload moves very slowly and is much lighter than the tether, the tether at the attachment point is almost vertical, but not completely vertical.
And I am not getting energy out of nothing. There are two invariants that must be conserved: energy and angular momentum. Energy is supplied from the outside (from a ground-based laser), and angular momentum is supplied from the earth via the attachment point.
This is simple newtonian mechanics, so I am 100% sure that it works that way. You want to bet over a box of beer? I suggest Henry Spencer of sci.space.policy as an authority to decide who is right:-)
I wish I had modpoints. Rotovators are indeed much more practical than space elevators. They do not require exotic new materials such as carbon nanotubes. They can be built with cheap materials like spectra or zylon fiber. They are also much shorter (100km instead of 36000km) and more flexible.
This system could double the payload capacity of launchers to geosynchronous transfer orbit or pick up small payloads from suborbital trajectories.
This could be built today. Rotovators are also a very good addition to suborbital space transports such as SpaceShipOne.
You don't get it. I don't blame you because it is not trivial.
When the tether is in place but no payloads move up or down, the top of the tether is directly overhead of the base station, so there is no net force on the top. But when a payload moves upwards, it will create a coriolis force which pulls the tether slightly backwards relative to the rotation of the earth.
Thus the force of the part of the tether below the payload has a component in the direction of the orbital motion of the payload, and the tether accelerates the payload and thus conserves angular momentum.
There is no need for thrust at the top of the tether. That is why space elevators are so attractive.
The energy is provided by the climber, which in the current designs is powered by a beam of light coming from a ground station.
The angular momentum for the orbit comes from the rotation of the earth. If you would launch billions of tons of rock using a space elevator, the rotation of the earth would slow down noticeably.
Well, writing 3D games requires a lot of knowledge about 3D geometry (crossproducts, matrices, quaternions and so on), and so does writing rocket control software. So that certainly helped.
But the most important thing is obviously the money from doom and quake.
I think you should do something different than just entering college. Like volunteering with the Geek Corps or joining the army for a year or whatever.
I am not a religious person, but I found that religious people that went on a mission for a year or two came back completely changed for the better. So you should do something similar.
The point about college is not so much that it requires extreme intelligence. They make you do all kinds of stupid shit, and if what you said is true the most important thing you will need is discipline.
I learned this the hard way. I am also very intelligent, yet I dropped out of college before finishing my master in physics because I just could not stand it anymore after 15 continuous years of school.
If I had done something different before entering college it would be something completely different. One year of real life experience is worth more than 10 years of school, IMHO. After 15 years of school/high school/college, I was a lonely, constantly depressed alcoholic.
Now after a few years of real life I got a very beautiful girlfriend, a well-paying and interesting job, and my life is really good. I wish I had finished college, but with the self confidence I gained it should not be such a big problem should I decide to try it again.
But there is also a positive side: being inside the crater, the rover is not as exposed to the cold night sky as it would be on a plain. And maybe they can drive the rover to a slope where the panels get pointed to the sun to compensate for the shadows.
The slope will also be a major issue for spirit once it climbs the columbia hills. It will probably avoid the sides that point away from the sun. Maybe it will drive to an especially good spot each day to refuel the batteries.
You can thank the fear of everything nuclear for this. Usually you would run a mars rover from a RTG. That way they would have enough power to run the rover continuously for years, and also enough heat to make sure none of the components fails because of excessive thermal cycling.
But since nuclear==BAD, they have to run the rover from a solar cell which gives only a tiny trickle of power during the daytime and none at all during the night. All components are subject to massive thermal cycling. So sooner or later either the solar panel will be too coated with dust to work, or the battery will no longer work, or components will fail because of excessive thermal cycling.
Note that all of these problems would be trivial to avoid if you had 50W electrical power and 1kw thermal power continuously, like you would get from a tiny RTG.
--
The standards are royalty free Any credible sources for this?
however the standards only cover the CLR (the VM/JIT) and C# the language, not the Framework (all the classes that do stuff). I know. But the CLR is the most important part. The linux community can write their own libraries just fine. GTK# and Qt# already have more features than Windows.Forms (e.g. decent layout management) --
We are using the Boehm collector in precise mode, so all we are missing is the compacting features. It does a fairly good job, and we can run large applications with good success.
But a generational GC would have much better performance for short-lived objects, wouldn't it?
Doing a compacting collector is in our radar,
but we have to balance our resources: port to
new platforms, support 2.0 features and improve
performance.
As long as you keep in mind that you will have to change to a generational GC some day, thats O.K. The generics of 2.0 will reduce the load to the garbage collector because putting valuetypes into a (typed)collection will no longer require boxing.
Mono 1.0 will use Boehm, but after that we might
consider using a different collector (in fact,
we have some preliminary patches for doing
refcount-based systems).
Refcounts? I thought the problem with refcount-based systems was that they were not able to deal with circular references. What have I missed?
--
I was under impression that mono has switched to a modern generational garbage collector, the Intel ORP GC. But the current beta uses the conservative boehm garbage collector.
A conservative GC is nice for a quick hack, but it really does not cut it for a modern VM.
So which one will it use in mono 1.0? Boehm or ORP? And if it is the boehm collector, what plans are there to switch to a modern GC?
By the way: the conservative garbage collector is the only real technical flaw of mono. Other than that it is quite a modern VM. Quite amazing for this short development time...
--
Any news about the patent review?
on
Mono Beta 2 Released
·
· Score: 4, Insightful
The only information that is needed for the success of mono is the following: are the relevant ECMA standards 334 and 335 and just RAND, or are they really RAND and royalty free as miguel and others have claimed?
If it is really RAND and royalty free, it will become my favorite development platform. Working with.NET is really very nice and productive. Microsoft will finally have made a valuable and lasting contribution to computer science.
If not, it is just another poisoned fruit by microsoft. --
Gee, it's a good thing that electrical or other engineering flaws can't ignite liquid fuel during storage, transport, or fuelling. I'm also pleased to discover that problems of sloppy management can be alleviated through the use of liquid fuels....
There is still a huge difference. A liquid fueled vehicle is fueled on the pad, when the next human being is in a bunker about 500m away. The fuel and oxidizer themselves (usually kerosene and liquid oxygen) are not that dangerous as long as they don't mix.
With a solid fueled rocket the fuel and oxidizer are mixed and casted into the shell of the rocket motor before the rocket is assembled. So all the manual labor of the assembly of the stages and the attachment of the payload takes place a few meters away from several dozen tons of highly explosive fuel/oxidizer mixture.
The accident in brazil was not the first accident with solid fuels. There have been several american and japanese launch vehicle accidents that were related to solid booster rockets.
Using solid fuels for a new launcher is just totally braindead unless you need a launcher that can be stored for years and then launched in seconds, like with an ICBM.
Property is a central economic institution of any society, and private property is the central institution of a free society.
That is not true. The RD-170 engines for the boosters are still in production for the zenit sea launch vehicles. And the first stage of the zenit vehicle was used as the booster rockets of the energia. So the only thing you would have to do would be to resume production of the core stage.
The problem is that there is no demand for such large payloads. But if you gave the russians a few billion USD they could certainly reactivate the energia.
Those Falcon launchers sound impressive, but are completely unproven and it remains to be seen how they perform in reality and what the real cost is. Saying that something is "a step backward" from stuff that doesn't exist doesn't make much sense. The falcon launchers are just as unproven as the vega launcher. Neither of them has flown, but the engines of both falcon and vega have been tested on test stands.
And I am totally convinced that using solids for civilian launchers is a major step backward. Imagine having to work on a launch vehicle full of highly explosive propellant. A liquid fueled launch vehicle on the other hand gets fueled on the pad, so as long as it is in the assembly building it is just a bunch of totally inert metal. Even if you can control the risk, the safety precautions make assembling the solid-fueled launcher much more expensive.
The first falcon I launch will be in this summer, and the first falcon V launch will be in the fall of next year if all goes according to plan. The first vega launch will be in 2006.
Conspiracy theory time! I wonder what the throw weight is, say, halfway around the globe? About three to four tons. But that was just a joke. It could be used as an ICBM though. --
Small solid launch vehicles have been tried before. For example the athena and taurus rockets by lockheed. Even though they used old ICBM technology they are commercial failures.
Another problem with solid rockets is that they have a rather extreme launch environment (lots of vibration), so you have to beef up your payload to handle the vibrations.
Solid rockets for civilian applications are just a bad idea.
You don't need to be a rocket scientist to see that when falcon V costs 12 million USD and has a payload of 4200kg while vega costs 20 million USD and has a payload of 1500kg, the vega project does not make any sense.
And everybody on sci.space.tech or sci.space.policy will agree that using solid propellant for a civilian launcher is just asking for trouble.
21 rocket scientists from brazil would definitely agree with this. Unfortunately they can't because they are all dead!
To back up my assertion that the vega is not competitive: here are a few launch prices:
The vega is supposed to cost 20 million USD for a payload of 1500kg to LEO. The Falcon I will cost 6 million USD for a payload of 700kg to a similar orbit, and the Falcon V will cost 12 million USD and have a payload of 4200kg to LEO.
So commercially vega will be a complete desaster. The only payloads that will go to vega will be government payloads that can not go to falcon for reasons of national prestige.
On the other hand, vega is a decent ICBM with MIRV capability.
Vega is a solid-fueled launcher based on the Ariane V boosters. Solid-fueled launchers are great for the military since they can launch at a moments notice, but other than that they are a big PITA.
Since they arrive at the launch complex fully fueled, they are a major safety risk. There have been numerous accidents with solid-fueled boosters. The last major accident was in brazil, and it killed several people and completely destroyed the launch complex.
The solid fueled boosters of the shuttle make assembly much more difficult, and if a shuttle SRB were to accidentally go off while in the assembly building, it would probably kill hundreds of people. That is why NASA tries to limit the number of people working on the shuttle while the SRB are attached, which of course increases the cost and the processing time.
For a really modern and cheap small launcher, take a look at the falcon.
There has been a long discussion about this topic in the sci.space.policy news group.
The people in there are usually extremely well informed, and none of them could see a plausible way how this could work. The problem is that there is no way to get lift without drag, and even with a very good supersonic lift to drag ratio the drag would be bigger than the thrust of the ion engines.
If they can pull it off anyway, they will get richer than bill gates. But I am not holding my breath.
Tourists will do all kinds of things. Favorite activities will be looking out of the window, all kinds of strange zero gravity sports, and of course zero-gravity sex.
And who says that civilians can not do science in space? There is a lot of science that has not yet been done by NASA, so you can expect many of the initial customers to be from universities and private research labs.
It will coast to 100km, which is the official edge of space. And the design is not a dead end. It does exactly what it is designed to do: fly to 100km.
The overall concept which rutan is using is staging at high altitude and low speed with a more or less conventional aircraft as a first stage.
This is most definitely not a dead end. There are existing launchers such as pegasus that do it that way, and there are also some very serious proposals for orbital two stage space transports with a large, rocket assisted transport aircraft as a first stage.
Give rutan a price of 100 million $ and he will come up with a concept for an orbital two stage space transport. It will probably look completely different (no two rutan aircraft look alike), but I would bet that it will use subsonic staging at high altitude.
Slashdot Mirror
The amount of (angular) momentum that has to be transferred is quite large, but you can transfer it over a long time (days), so the sideways force on the tether attachment point is small.
If you don't believe me just check out the publications of highlift systems or any other paper on space elevators. They never mention propulsion because it is not nessecary.
A tether that is not in contact with the ground would indeed need propulsion.
:-)
But in all designs I know there is a contact between tether and ground. Since the tether is bent slightly backwards by the coriolis force of the upward-moving climber, there is a force component at the anchor point that is parallel to the motion of the attachment point, so angular momentum is transferred.
Since the payload moves very slowly and is much lighter than the tether, the tether at the attachment point is almost vertical, but not completely vertical.
And I am not getting energy out of nothing. There are two invariants that must be conserved: energy and angular momentum. Energy is supplied from the outside (from a ground-based laser), and angular momentum is supplied from the earth via the attachment point.
This is simple newtonian mechanics, so I am 100% sure that it works that way. You want to bet over a box of beer? I suggest Henry Spencer of sci.space.policy as an authority to decide who is right
I wish I had modpoints. Rotovators are indeed much more practical than space elevators. They do not require exotic new materials such as carbon nanotubes. They can be built with cheap materials like spectra or zylon fiber. They are also much shorter (100km instead of 36000km) and more flexible.
This system could double the payload capacity of launchers to geosynchronous transfer orbit or pick up small payloads from suborbital trajectories.
This could be built today. Rotovators are also a very good addition to suborbital space transports such as SpaceShipOne.
I meant measurable as in measurable with an atom clock. If you want 1 second longer days you will indeed have to launch much more.
You don't get it. I don't blame you because it is not trivial.
When the tether is in place but no payloads move up or down, the top of the tether is directly overhead of the base station, so there is no net force on the top. But when a payload moves upwards, it will create a coriolis force which pulls the tether slightly backwards relative to the rotation of the earth.
Thus the force of the part of the tether below the payload has a component in the direction of the orbital motion of the payload, and the tether accelerates the payload and thus conserves angular momentum.
There is no need for thrust at the top of the tether. That is why space elevators are so attractive.
The energy is provided by the climber, which in the current designs is powered by a beam of light coming from a ground station.
The angular momentum for the orbit comes from the rotation of the earth. If you would launch billions of tons of rock using a space elevator, the rotation of the earth would slow down noticeably.
Well, writing 3D games requires a lot of knowledge about 3D geometry (crossproducts, matrices, quaternions and so on), and so does writing rocket control software. So that certainly helped.
But the most important thing is obviously the money from doom and quake.
I think you should do something different than just entering college. Like volunteering with the Geek Corps or joining the army for a year or whatever.
I am not a religious person, but I found that religious people that went on a mission for a year or two came back completely changed for the better. So you should do something similar.
The point about college is not so much that it requires extreme intelligence. They make you do all kinds of stupid shit, and if what you said is true the most important thing you will need is discipline.
I learned this the hard way. I am also very intelligent, yet I dropped out of college before finishing my master in physics because I just could not stand it anymore after 15 continuous years of school.
If I had done something different before entering college it would be something completely different. One year of real life experience is worth more than 10 years of school, IMHO. After 15 years of school/high school/college, I was a lonely, constantly depressed alcoholic.
Now after a few years of real life I got a very beautiful girlfriend, a well-paying and interesting job, and my life is really good. I wish I had finished college, but with the self confidence I gained it should not be such a big problem should I decide to try it again.
But there is also a positive side: being inside the crater, the rover is not as exposed to the cold night sky as it would be on a plain. And maybe they can drive the rover to a slope where the panels get pointed to the sun to compensate for the shadows.
The slope will also be a major issue for spirit once it climbs the columbia hills. It will probably avoid the sides that point away from the sun. Maybe it will drive to an especially good spot each day to refuel the batteries.
--
You can thank the fear of everything nuclear for this. Usually you would run a mars rover from a RTG. That way they would have enough power to run the rover continuously for years, and also enough heat to make sure none of the components fails because of excessive thermal cycling.
But since nuclear==BAD, they have to run the rover from a solar cell which gives only a tiny trickle of power during the daytime and none at all during the night. All components are subject to massive thermal cycling. So sooner or later either the solar panel will be too coated with dust to work, or the battery will no longer work, or components will fail because of excessive thermal cycling.
Note that all of these problems would be trivial to avoid if you had 50W electrical power and 1kw thermal power continuously, like you would get from a tiny RTG.
--
The standards are royalty free
Any credible sources for this?
however the standards only cover the CLR (the VM/JIT) and C# the language, not the Framework (all the classes that do stuff).
I know. But the CLR is the most important part. The linux community can write their own libraries just fine. GTK# and Qt# already have more features than Windows.Forms (e.g. decent layout management)
--
We are using the Boehm collector in precise mode, so all we are missing is the compacting features. It does a fairly good job, and we can run large applications with good success.
But a generational GC would have much better performance for short-lived objects, wouldn't it?
Doing a compacting collector is in our radar, but we have to balance our resources: port to new platforms, support 2.0 features and improve performance.
As long as you keep in mind that you will have to change to a generational GC some day, thats O.K. The generics of 2.0 will reduce the load to the garbage collector because putting valuetypes into a (typed)collection will no longer require boxing.
Mono 1.0 will use Boehm, but after that we might consider using a different collector (in fact, we have some preliminary patches for doing refcount-based systems).
Refcounts? I thought the problem with refcount-based systems was that they were not able to deal with circular references. What have I missed?
--
I was under impression that mono has switched to a modern generational garbage collector, the Intel ORP GC. But the current beta uses the conservative boehm garbage collector.
A conservative GC is nice for a quick hack, but it really does not cut it for a modern VM.
So which one will it use in mono 1.0? Boehm or ORP? And if it is the boehm collector, what plans are there to switch to a modern GC?
By the way: the conservative garbage collector is the only real technical flaw of mono. Other than that it is quite a modern VM. Quite amazing for this short development time...
--
The only information that is needed for the success of mono is the following: are the relevant ECMA standards 334 and 335 and just RAND, or are they really RAND and royalty free as miguel and others have claimed?
.NET is really very nice and productive. Microsoft will finally have made a valuable and lasting contribution to computer science.
If it is really RAND and royalty free, it will become my favorite development platform. Working with
If not, it is just another poisoned fruit by microsoft.
--
Gee, it's a good thing that electrical or other engineering flaws can't ignite liquid fuel during storage, transport, or fuelling. I'm also pleased to discover that problems of sloppy management can be alleviated through the use of liquid fuels....
There is still a huge difference. A liquid fueled vehicle is fueled on the pad, when the next human being is in a bunker about 500m away. The fuel and oxidizer themselves (usually kerosene and liquid oxygen) are not that dangerous as long as they don't mix.
With a solid fueled rocket the fuel and oxidizer are mixed and casted into the shell of the rocket motor before the rocket is assembled. So all the manual labor of the assembly of the stages and the attachment of the payload takes place a few meters away from several dozen tons of highly explosive fuel/oxidizer mixture.
The accident in brazil was not the first accident with solid fuels. There have been several american and japanese launch vehicle accidents that were related to solid booster rockets.
Using solid fuels for a new launcher is just totally braindead unless you need a launcher that can be stored for years and then launched in seconds, like with an ICBM.
Property is a central economic institution of any society, and private property is the central institution of a free society.
That is not true. The RD-170 engines for the boosters are still in production for the zenit sea launch vehicles. And the first stage of the zenit vehicle was used as the booster rockets of the energia. So the only thing you would have to do would be to resume production of the core stage.
The problem is that there is no demand for such large payloads. But if you gave the russians a few billion USD they could certainly reactivate the energia.
--
Those Falcon launchers sound impressive, but are completely unproven and it remains to be seen how they perform in reality and what the real cost is. Saying that something is "a step backward" from stuff that doesn't exist doesn't make much sense.
The falcon launchers are just as unproven as the vega launcher. Neither of them has flown, but the engines of both falcon and vega have been tested on test stands.
And I am totally convinced that using solids for civilian launchers is a major step backward. Imagine having to work on a launch vehicle full of highly explosive propellant. A liquid fueled launch vehicle on the other hand gets fueled on the pad, so as long as it is in the assembly building it is just a bunch of totally inert metal. Even if you can control the risk, the safety precautions make assembling the solid-fueled launcher much more expensive.
The first falcon I launch will be in this summer, and the first falcon V launch will be in the fall of next year if all goes according to plan. The first vega launch will be in 2006.
Conspiracy theory time! I wonder what the throw weight is, say, halfway around the globe?
About three to four tons. But that was just a joke. It could be used as an ICBM though.
--
Small solid launch vehicles have been tried before. For example the athena and taurus rockets by lockheed. Even though they used old ICBM technology they are commercial failures.
Another problem with solid rockets is that they have a rather extreme launch environment (lots of vibration), so you have to beef up your payload to handle the vibrations.
Solid rockets for civilian applications are just a bad idea.
--
You don't need to be a rocket scientist to see that when falcon V costs 12 million USD and has a payload of 4200kg while vega costs 20 million USD and has a payload of 1500kg, the vega project does not make any sense.
And everybody on sci.space.tech or sci.space.policy will agree that using solid propellant for a civilian launcher is just asking for trouble.
21 rocket scientists from brazil would definitely agree with this. Unfortunately they can't because they are all dead!
--
To back up my assertion that the vega is not competitive: here are a few launch prices:
The vega is supposed to cost 20 million USD for a payload of 1500kg to LEO. The Falcon I will cost 6 million USD for a payload of 700kg to a similar orbit, and the Falcon V will cost 12 million USD and have a payload of 4200kg to LEO.
So commercially vega will be a complete desaster. The only payloads that will go to vega will be government payloads that can not go to falcon for reasons of national prestige.
On the other hand, vega is a decent ICBM with MIRV capability.
The most promising propellantless launch technology is rotating tethers.
Check out this for plenty of information about what is possible. here is a paper about a tether for LEO to GTO boost that could be built today.
All the other things like electric catapults are much too large to be practical if you want reasonable g-forces.
--
Vega is a solid-fueled launcher based on the Ariane V boosters. Solid-fueled launchers are great for the military since they can launch at a moments notice, but other than that they are a big PITA.
Since they arrive at the launch complex fully fueled, they are a major safety risk. There have been numerous accidents with solid-fueled boosters. The last major accident was in brazil, and it killed several people and completely destroyed the launch complex.
The solid fueled boosters of the shuttle make assembly much more difficult, and if a shuttle SRB were to accidentally go off while in the assembly building, it would probably kill hundreds of people. That is why NASA tries to limit the number of people working on the shuttle while the SRB are attached, which of course increases the cost and the processing time.
For a really modern and cheap small launcher, take a look at the falcon.
--
There has been a long discussion about this topic in the
sci.space.policy news group.
The people in there are usually extremely well informed, and none of them could see a plausible way how this could work. The problem is that there is no way to get lift without drag, and even with a very good supersonic lift to drag ratio the drag would be bigger than the thrust of the ion engines.
If they can pull it off anyway, they will get richer than bill gates. But I am not holding my breath.
Tourists will do all kinds of things. Favorite activities will be looking out of the window, all kinds of strange zero gravity sports, and of course zero-gravity sex.
And who says that civilians can not do science in space? There is a lot of science that has not yet been done by NASA, so you can expect many of the initial customers to be from universities and private research labs.
It will coast to 100km, which is the official edge of space. And the design is not a dead end. It does exactly what it is designed to do: fly to 100km.
The overall concept which rutan is using is staging at high altitude and low speed with a more or less conventional aircraft as a first stage.
This is most definitely not a dead end. There are existing launchers such as pegasus that do it that way, and there are also some very serious proposals for orbital two stage space transports with a large, rocket assisted transport aircraft as a first stage.
Give rutan a price of 100 million $ and he will come up with a concept for an orbital two stage space transport. It will probably look completely different (no two rutan aircraft look alike), but I would bet that it will use subsonic staging at high altitude.