The rocket equation is highly non-linear. If you leave 30% of the fuel in the rocket for the return trip, you may lose a large proportion your final impulse and so final speed before separation with the second stage. I don't see how that could be economical.
The thing is that reusable engines have existed for a while. Solid Rocket Boosters are the simplest. They use 100% of their fuel every time, and they are retrieved by parachutes. Even under these conditions, they need significant rebuilding. SRB Rebuilding issues were a significant factor in the Challenger disaster. How economical was that?
Because this assume that the hardware will actually be reusable. Rocket engines are not like jet engines. All the data on the space shuttle has shown that its engines basically needed to be rebuilt every time, over periods of several months. This was not correctly anticipated by NASA and as far as I know, it was never solved over the entire life of the Space Shuttle. This fact was also the main reason the Space Shuttle was not able to launch sufficiently often.
This also assume that the hardware will be retrieved every time. Perhaps SpaceX will improve, but it looks as if a vertical landing is actually harder than an vertical launch, and we know those are not 100% reliable.
SpaceX believes that reusing the 1st stage could lower its launch costs by 30% ; I'm just being highly skeptical of this claim. Fortunately, it doesn't matter all that much.
What I find highly annoying is the belief that because SpaceX is a private enterprise, they will necessarily do better than a large governmental agency like NASA.
The parent is right., the US church attendance is 39% according to the wikipedia link you gave. Church attendance in Europe varies between 3% in Norway to 54% in Poland. The Church attendance in the US is a little high compared to the average in Europe but not that far.
To pull that off they have to leave unburned fuel in the stage rocket, going all the way up and all the way down. This means the stage engine is not as efficient as it could be. It is not obvious that doing this risky vertical landing is going to result in any savings at all.
For any larger rockets, multi-stage rockets this is going to look worse and worse. later stages actually orbit the Earth for a while. Pulling something out of orbit requires a lot of fuel, making the endeavour even less economic.
Correct. I remember ordering 128MB for a Sun workstation at work ca. 1995. This was considered huge, and the engineer who came to install it was more impressed by the fact that I was able to completely fill it with data from an actual problem in a few minutes.
Nobody in academia lands an academic job right after their PhD. After their graduation, young doctors who want to continue into academia go to a different lab, where they continue to do research, publish, teach and so on. They are supposed to learn the techniques of the new lab and to spread the ones of the old lab in the new place. Usually a Postdoc salary is OK. It is typically twice that of a PhD student. Usually a Post-doc position is quite nice.
After a couple of years as Post-doc, typically people find an assistant professor job somewhere. *This* is where they start to work 80-hours week.
The solution is to design exams so that having a cheating watch is of no help. Open-book exams are the best. Disclaimer: I'm a prof, all my exams are open-book. If you didn't study beforehand, the textbook is of little help.
Low income and poverty are different things. Maine is fairly rural. Income in the countryside goes a lot further than in the city. It is not so much raw income that counts, rather inequality. Living in the gutter right next to someone who lives in an expensive condo may drive people to crime.
Lack of empathy is not a standard we as a society should aspire to. This would mean it would be OK to openly mock, bully, despise, put down and generally be assholes to one another without check. Basically this would mean reverting to caveman-like behaviours, where the physically strongest is the chief because no one dares contradicting him.
I'm sure many of the men on this forum have stinging memories of middle school because they fell victim to such behaviour at recess time. I'm actually curious why many here voted such a proposal up.
Assuming that some day humanity develops strong AI, and shortly after a super-intelligence emerges. It seems obvious to me that this super-AI would no longer care about humanity and all its achievements, as we would be a complete waste of resources. Think of all the waste we generate as a species. Then, it seems our long-term future is doomed without strong AI because we are too fragile to achieve anything beyond our solar system, and we are doomed with it because we will be irrelevant. Is humanity but a stepping stone to something grander ? if so, why is the universe not already teeming with artificial life ?
We are steadily developing the required computational resources to simulate a decent-size artificial brain. We have concurrently developed advanced machine learning methods, for instance deep learning. Together, these advances have allowed us to solve long-standing AI problems, such as automated translation, chess, face recognition, and others, to a high degree of accuracy, even beating humans. Perhaps in the near future a computer will convincingly pass the Turing test.
However we have made comparatively little progress on autonomous learning, i.e. letting a computer learn something by itself, and not by example. Do you view it as essential, and is there a path forward in this area?
Going to Mars sounds nice, but there doesn't seem to be anything of note to mine or exploit there that would make it economically viable. It is not a lifeboat for humanity in the short run either because it would require such a continual feed of stuff from Earth to be survivable.
If we wanted a humanity lifeboat, It would be easier, cheaper, safer and more effective to build a giant, self-sustained fallout shelter under the ice of Antarctica than going to Mars. We are not doing that either.
I wouldn't say people don't care. Some don't care. I should think many do care.
You worry that some people don't like your plan. This is the exact same situation. Publish your plan, hopefully if it is good it will be implemented some day.
Observers of the current state of the space program like to maintain that a space race, such as occurred in the 1960s, will never happen again.
Emphasis mine. The little race between Musk and Boeing is nice to watch, however in the 1960s we were watching a race between two superpowers with basically no holds barred.
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So you have to send to orbit a heat shield. This is not free.
Depends on many factor, like reliability, and how much of the retrieved engines they can actually reuse.
The rocket equation is highly non-linear. If you leave 30% of the fuel in the rocket for the return trip, you may lose a large proportion your final impulse and so final speed before separation with the second stage. I don't see how that could be economical.
The thing is that reusable engines have existed for a while. Solid Rocket Boosters are the simplest. They use 100% of their fuel every time, and they are retrieved by parachutes. Even under these conditions, they need significant rebuilding. SRB Rebuilding issues were a significant factor in the Challenger disaster. How economical was that?
Because this assume that the hardware will actually be reusable. Rocket engines are not like jet engines. All the data on the space shuttle has shown that its engines basically needed to be rebuilt every time, over periods of several months. This was not correctly anticipated by NASA and as far as I know, it was never solved over the entire life of the Space Shuttle. This fact was also the main reason the Space Shuttle was not able to launch sufficiently often.
This also assume that the hardware will be retrieved every time. Perhaps SpaceX will improve, but it looks as if a vertical landing is actually harder than an vertical launch, and we know those are not 100% reliable.
SpaceX believes that reusing the 1st stage could lower its launch costs by 30% ; I'm just being highly skeptical of this claim. Fortunately, it doesn't matter all that much.
What I find highly annoying is the belief that because SpaceX is a private enterprise, they will necessarily do better than a large governmental agency like NASA.
On the ground that they are a danger to themselves and others ?
The parent is right., the US church attendance is 39% according to the wikipedia link you gave. Church attendance in Europe varies between 3% in Norway to 54% in Poland. The Church attendance in the US is a little high compared to the average in Europe but not that far.
To pull that off they have to leave unburned fuel in the stage rocket, going all the way up and all the way down. This means the stage engine is not as efficient as it could be. It is not obvious that doing this risky vertical landing is going to result in any savings at all.
For any larger rockets, multi-stage rockets this is going to look worse and worse. later stages actually orbit the Earth for a while. Pulling something out of orbit requires a lot of fuel, making the endeavour even less economic.
This is interesting but looks like a stunt.
Correct. I remember ordering 128MB for a Sun workstation at work ca. 1995. This was considered huge, and the engineer who came to install it was more impressed by the fact that I was able to completely fill it with data from an actual problem in a few minutes.
Sorry you don't know what a Postdoc is.
Nobody in academia lands an academic job right after their PhD. After their graduation, young doctors who want to continue into academia go to a different lab, where they continue to do research, publish, teach and so on. They are supposed to learn the techniques of the new lab and to spread the ones of the old lab in the new place. Usually a Postdoc salary is OK. It is typically twice that of a PhD student. Usually a Post-doc position is quite nice.
After a couple of years as Post-doc, typically people find an assistant professor job somewhere. *This* is where they start to work 80-hours week.
The solution is to design exams so that having a cheating watch is of no help. Open-book exams are the best. Disclaimer: I'm a prof, all my exams are open-book. If you didn't study beforehand, the textbook is of little help.
The terrorists in Paris used assault rifles for their attack. They are already banned in the whole of Europe. I think there is a lesson in this.
very reactive, amazing.
Low income and poverty are different things. Maine is fairly rural. Income in the countryside goes a lot further than in the city. It is not so much raw income that counts, rather inequality. Living in the gutter right next to someone who lives in an expensive condo may drive people to crime.
So interstellar travel is impossible on economical grounds.
Easier but maybe still impossible. We don't know.
Lack of empathy is not a standard we as a society should aspire to. This would mean it would be OK to openly mock, bully, despise, put down and generally be assholes to one another without check. Basically this would mean reverting to caveman-like behaviours, where the physically strongest is the chief because no one dares contradicting him.
I'm sure many of the men on this forum have stinging memories of middle school because they fell victim to such behaviour at recess time. I'm actually curious why many here voted such a proposal up.
Assuming that some day humanity develops strong AI, and shortly after a super-intelligence emerges. It seems obvious to me that this super-AI would no longer care about humanity and all its achievements, as we would be a complete waste of resources. Think of all the waste we generate as a species. Then, it seems our long-term future is doomed without strong AI because we are too fragile to achieve anything beyond our solar system, and we are doomed with it because we will be irrelevant. Is humanity but a stepping stone to something grander ? if so, why is the universe not already teeming with artificial life ?
We are steadily developing the required computational resources to simulate a decent-size artificial brain. We have concurrently developed advanced machine learning methods, for instance deep learning. Together, these advances have allowed us to solve long-standing AI problems, such as automated translation, chess, face recognition, and others, to a high degree of accuracy, even beating humans. Perhaps in the near future a computer will convincingly pass the Turing test.
However we have made comparatively little progress on autonomous learning, i.e. letting a computer learn something by itself, and not by example. Do you view it as essential, and is there a path forward in this area?
Going to Mars sounds nice, but there doesn't seem to be anything of note to mine or exploit there that would make it economically viable. It is not a lifeboat for humanity in the short run either because it would require such a continual feed of stuff from Earth to be survivable.
If we wanted a humanity lifeboat, It would be easier, cheaper, safer and more effective to build a giant, self-sustained fallout shelter under the ice of Antarctica than going to Mars. We are not doing that either.
I wouldn't say people don't care. Some don't care. I should think many do care.
You worry that some people don't like your plan. This is the exact same situation. Publish your plan, hopefully if it is good it will be implemented some day.
You should have tested the distribution with a $\chi^2$ test.
Just in case someone is wondering, this is true, read this.
Maybe I'm reading this wrong, but let's see you do it :-)
Good on him indeed, this means several things:
He's a big-shot CEO who can delegate. Great
This sort of things is not reserved for women. Fathers should take time off too. Great
The workplace is not the be-all and end-all of all things. Kids are important too, they are our future. Great
Quote:
Observers of the current state of the space program like to maintain that a space race, such as occurred in the 1960s, will never happen again.
Emphasis mine. The little race between Musk and Boeing is nice to watch, however in the 1960s we were watching a race between two superpowers with basically no holds barred.