It helps due to less air density. Its a bit tricky:
If you try to build a very small orbital vehicle, air drag is a major factor. This means that for sea level launches, rockets need to be quite large. By starting with 1/5 the pressure, the rocket can in principal be 1/5 the size (if nothing else is limiting) so very much lighter. Air launch makes small orbital vehicles more practical.
Another effect is that the efficiency (specific impulse) of rocket engines is better with lower atmospheric pressure. So the engines on an air launched rocket provide more delta-V for the same fuel.
Neither of these is a huge factor, but they help. The idea makes physics sense. Whether or not it makes economic sense is a different question (it may)
Purchasing fuels production by adding money to the system. I don't see how free distribution does that, but possession of CP is illegal even if no money changed hands. I assume the argument is that no one should have images of their abuse / rape distributed on the internet.
The argument that possessing child porn, not just purchasing or producing child porn should be illegal is that the images are harmful to children in some fashion. Otherwise there would be no reason not to allow the large amount of existing CP to be distributed for free. In fact making distribution of existing CP illegal probably encourages the production of new material, and that production is obviously harmful. The only way this policy makes any sense is if the images themselves are harmful.
I have no personal opinion one way or the other on the harm caused by the distribution of existing CP. I'm just pointing out that the existing laws only make sense if it is harmful.
If that is the case, then the FBI distributing CP seems indefensible in the same way that the FBI distributing narcotics, committing murder for hire, or prostituting children would be indefensible regardless of the end goal of reducing crime.
Unless they are planning to recover the entire rocket - extremely difficult due to re-entry heating, the SpaceX first stage recovery just seems better. It allows re-use of a large part of the total rocket mass and engines, and just throws away the upper stage rather than the full rocket.
If someone figures out a low mass way to recover a stage from orbit, then the SpaceX approach may still be a win rather than trying for very extreme mass ratios.
Nothing wrong with plug-nozzles in principal, but so far the ISP advantage hasn't been enough to make up for the extra weight in a real application.
H2O2 seems a strange choice instead of Liquid Oxygen. A SSTO rocket really needs high ISP and H2O2 is something like 10% worse - doesn't seem like much but it makes a big difference in the exponential.
Lox is not that difficult to deal with, not like Hydrogen.
H2 / LOx is a more typical choice for a SSTO design because of the much higher ISP, but the H2 is difficult to store which offsets some of its advantage.
Of course with SpaceX demonstrating successful 1st stage re-use, the advantage of a SSTO is much lower .
I've joined a variety of social groups on line and gotten bored and left, but not canceled the account. I have some google and yahoo accounts I haven't used in ages, and probably have an AOL account from 20 years ago, no idea what the password was. I don't even know my FB password, my computer auto logs in, and its in secure physical storage at home with my other passwords.
But I can't PROVE that I've forgotten my google+ account password.
Then again, being a middle-aged white guy, I guess I don't need to worry.
Its difficult to imagine a fusion plant being less expensive to build or operate than a fission plant. Even if we can figure out how to get net energy gain from fusion it may never make economic sense.
Its too bad, I wanted a nuclear powered future, with fission gradually being replaced by fusion of the next century. Doesn't look likely.
Nuclear has great potential in long distance spacecraft propulsion, but it just doesn't look very economically practical for terrestrial use.
I really do, but the endless parade of of proposed supersonic transports starting with the Boeing SST, that were eventually canceled makes me pretty pessimistic.
The basic technology for supersonic flight hasn't changed. Its not clear why the they claim that the will succeed where so many other companies have failed.
I'm a little surprised though that galactic mass black holes can in-spiral at any reasonable rate. It seems like the initial pass must have been exceptionally close.
That's probably true, I don't know much about piston engines at high altitude because they are rarely used there. A supercharger does lose energy. I think in principal a turbocharger doesn't lose energy, but in practice the intercooler is inefficient (throws away energy). I don't know how that balances against the higher combustion temperature in a piston engine.
I guess in some ways a turbo-compounded engine (supercharger and expansion turbine coupled to the main drive) smoothly blends into a turboprop where the piston engine acts like a combustion chamber. In practice no one uses these any more since the turbines are so much lighter. Some of the last generation turbo-compounded piston engines were pretty impressive machines. https://en.wikipedia.org/wiki/...
In practice turbo-props are clearly the best solution for all but the smallest planes.
The turboprop aircraft is more efficient, the turboprop engine is less efficient when you remember that kerosene is higher density than gasoline but its pretty close. The Wikipedia link doesn't have recent engines of either type, but gives a hint: https://en.wikipedia.org/wiki/...
My copy of Raymer (Aircraft design, a conceptual approach) gives a typical specific fuel consumption for a turbo prop as 0.5lb/hr-hp, and 0.4 for a piston. The detailed charts I have for a modern light aircraft piston engine (IO550) gives about 0.36. I don't have detailed numbers for a turboprop.
It doesn't really matter, the turboprops are so much lighter for the same power that they result in higher efficiency aircraft for all but the smallest planes. (turboprops don't scale well below about 1000hp).
The power density of present day fuel cells isn't very high. Power density is very important for aircraft because carrying extra weight uses more fuel. Its surprising but old fashioned aircraft piston engines are more efficient than modern jets (eg, more power produced per fuel burned). Modern planes use jets because they are very much lighter for the same power, so the overall aircraft efficiency is better (and the planes can fly faster).
I remember seeing design studies of hydrogen fueled aircraft where the hydrogen is burned in conventional engines. Even though the hydrogen is very light (which should be a big win for aircraft) the weight of the tanks and the extra volume (liquid hydrogen is very low density) made it not competitive with jet fuel.
Of course as technology changes these trade-offs could change.
You would have to compare similar missions, and look at how funding works in both countries. Its good that this team did a good low cost mission. That doesn't mean that a high cost mission that did something different was a waste.
Really. Not a snark, not a joke, I mean it. Its really fantastic that they managed a Mars mission on an extremely tight budget. Its a really difficult project and they did a fantastic job.
This sort of ultra-cheap approach might allow lots of probes to be sent to less studied bodies.
It may also be about the expected level of responsibility. A talented older worker will be in a position of considerable technical and / or managerial responsibility. If he / she tries to move out of their narrowly defined career, it may be difficult for a new employer to take the chance of giving them that much responsibility, but at the same time can't reasonably them as well for a position of less responsibility.
From what I've seen, moving within the same industry is not that difficult, but moving to a new industry is very tough for older workers.
An older worker who has lost their job (for any reason) can also be viewed as a risk. Sometimes "layoffs" really are about money but sometimes its a way of nicely firing someone. Do you trust that person to make critical decisions on your project?
Note, I'm one of those "older" workers and I don't like the idea that its very difficult to find different work, but I think I understand it .
Its a neat idea, even if it is a very watered down version of the 60's vacuum train concept that ran at near orbital speed. https://en.wikipedia.org/wiki/...
No fundamental physics issues, the big question is economics. The cars are pretty small and at those speeds you need a lot of spacing between trains. Curves need to be large radius and if track switching is even possible, the switches need to be very large. Its not clear that its less expensive than 350km/h high speed rail - which itself is often not cost effective.
The higher speed than high speed rail is nice for long trips (>150KM). but otherwise the boarding and accelerate/decelerate times will hide most of the difference. It will need airport like security since a relatively small bomb would kill a lot of people - sort of like an airliner, so it may be slower to board than high speed rail.
Not crazy but there isn't an obvious niche where it is cost effective (similar problems for maglev).
Considering that the argument for why distributing and owning (as opposed to producing) child porn is that the images actively harm children, I do not think there is any way to justify the FBI's behavior. I think its been generally established that law enforcement cannot commit felonies in order to gather evidence. Otherwise we could have police informants carrying out gang hits in order to capture higher level crime bosses. This is not the start of a slippery slope, it is well down the slope.
They can't have it both ways. If the images don't do actual harm to children, the people who posses the images are only guilty of a minor crime. If the images do harm children, then the FBI should destroy them as soon as they are discovered to prevent continuing harm .
On the central topic there need to be clear rules about what capabilities we want law enforcement to have. It is probably technologically possible for law enforcement to scan all of the records of the great majority of citizens to look for criminal activity. Is that what we want?
Personally I would vote to reduce surveillance and accept a higher rate of criminal activity.
I assume they have done some market research and think that $50 would be the price point that would make them the most money. Fair enough - they are a business, they have every right to set prices where they want, and consumers have every right to choose to purchase or not at that price.
$50 is more than some people can afford, and insignificant to others.
There *should* be zero tolerance for some behaviors. If someone is harassing one of their workers, in addition to behaving immorally and illegally, they are driving away talented people, and exposing the company to huge lawsuits.
Why should anyone ever be given a pass for this sort of behavior?
More minor offenses are a different matter, but a manger asking a direct report for sex is not a borderline case.
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It helps due to less air density. Its a bit tricky:
If you try to build a very small orbital vehicle, air drag is a major factor. This means that for sea level launches, rockets need to be quite large. By starting with 1/5 the pressure, the rocket can in principal be 1/5 the size (if nothing else is limiting) so very much lighter. Air launch makes small orbital vehicles more practical.
Another effect is that the efficiency (specific impulse) of rocket engines is better with lower atmospheric pressure. So the engines on an air launched rocket provide more delta-V for the same fuel.
Neither of these is a huge factor, but they help. The idea makes physics sense. Whether or not it makes economic sense is a different question (it may)
Purchasing fuels production by adding money to the system. I don't see how free distribution does that, but possession of CP is illegal even if no money changed hands. I assume the argument is that no one should have images of their abuse / rape distributed on the internet.
The argument that possessing child porn, not just purchasing or producing child porn should be illegal is that the images are harmful to children in some fashion. Otherwise there would be no reason not to allow the large amount of existing CP to be distributed for free. In fact making distribution of existing CP illegal probably encourages the production of new material, and that production is obviously harmful. The only way this policy makes any sense is if the images themselves are harmful.
I have no personal opinion one way or the other on the harm caused by the distribution of existing CP. I'm just pointing out that the existing laws only make sense if it is harmful.
If that is the case, then the FBI distributing CP seems indefensible in the same way that the FBI distributing narcotics, committing murder for hire, or prostituting children would be indefensible regardless of the end goal of reducing crime.
Child porn is illegal because distributing it harms children. Doing that in order to catch criminals is not OK.
Unless they are planning to recover the entire rocket - extremely difficult due to re-entry heating, the SpaceX first stage recovery just seems better. It allows re-use of a large part of the total rocket mass and engines, and just throws away the upper stage rather than the full rocket.
If someone figures out a low mass way to recover a stage from orbit, then the SpaceX approach may still be a win rather than trying for very extreme mass ratios.
Nothing wrong with plug-nozzles in principal, but so far the ISP advantage hasn't been enough to make up for the extra weight in a real application.
H2O2 seems a strange choice instead of Liquid Oxygen. A SSTO rocket really needs high ISP and H2O2 is something like 10% worse - doesn't seem like much but it makes a big difference in the exponential.
Lox is not that difficult to deal with, not like Hydrogen.
H2 / LOx is a more typical choice for a SSTO design because of the much higher ISP, but the H2 is difficult to store which offsets some of its advantage.
Of course with SpaceX demonstrating successful 1st stage re-use, the advantage of a SSTO is much lower .
I've joined a variety of social groups on line and gotten bored and left, but not canceled the account. I have some google and yahoo accounts I haven't used in ages, and probably have an AOL account from 20 years ago, no idea what the password was. I don't even know my FB password, my computer auto logs in, and its in secure physical storage at home with my other passwords.
But I can't PROVE that I've forgotten my google+ account password.
Then again, being a middle-aged white guy, I guess I don't need to worry.
I thought that and have been a fan of nuclear for a long time, but its starting to look like renewables will end up being cheaper.
Its difficult to imagine a fusion plant being less expensive to build or operate than a fission plant. Even if we can figure out how to get net energy gain from fusion it may never make economic sense.
Its too bad, I wanted a nuclear powered future, with fission gradually being replaced by fusion of the next century. Doesn't look likely.
Nuclear has great potential in long distance spacecraft propulsion, but it just doesn't look very economically practical for terrestrial use.
I really do, but the endless parade of of proposed supersonic transports starting with the Boeing SST, that were eventually canceled makes me pretty pessimistic.
The basic technology for supersonic flight hasn't changed. Its not clear why the they claim that the will succeed where so many other companies have failed.
One of the most amazing objects in the universe.
I'm a little surprised though that galactic mass black holes can in-spiral at any reasonable rate. It seems like the initial pass must have been exceptionally close.
That's probably true, I don't know much about piston engines at high altitude because they are rarely used there. A supercharger does lose energy. I think in principal a turbocharger doesn't lose energy, but in practice the intercooler is inefficient (throws away energy). I don't know how that balances against the higher combustion temperature in a piston engine.
I guess in some ways a turbo-compounded engine (supercharger and expansion turbine coupled to the main drive) smoothly blends into a turboprop where the piston engine acts like a combustion chamber. In practice no one uses these any more since the turbines are so much lighter. Some of the last generation turbo-compounded piston engines were pretty impressive machines. https://en.wikipedia.org/wiki/...
In practice turbo-props are clearly the best solution for all but the smallest planes.
The turboprop aircraft is more efficient, the turboprop engine is less efficient when you remember that kerosene is higher density than gasoline but its pretty close. The Wikipedia link doesn't have recent engines of either type, but gives a hint: https://en.wikipedia.org/wiki/...
My copy of Raymer (Aircraft design, a conceptual approach) gives a typical specific fuel consumption for a turbo prop as 0.5lb/hr-hp, and 0.4 for a piston. The detailed charts I have for a modern light aircraft piston engine (IO550) gives about 0.36. I don't have detailed numbers for a turboprop.
It doesn't really matter, the turboprops are so much lighter for the same power that they result in higher efficiency aircraft for all but the smallest planes. (turboprops don't scale well below about 1000hp).
The power density of present day fuel cells isn't very high. Power density is very important for aircraft because carrying extra weight uses more fuel. Its surprising but old fashioned aircraft piston engines are more efficient than modern jets (eg, more power produced per fuel burned). Modern planes use jets because they are very much lighter for the same power, so the overall aircraft efficiency is better (and the planes can fly faster).
I remember seeing design studies of hydrogen fueled aircraft where the hydrogen is burned in conventional engines. Even though the hydrogen is very light (which should be a big win for aircraft) the weight of the tanks and the extra volume (liquid hydrogen is very low density) made it not competitive with jet fuel.
Of course as technology changes these trade-offs could change.
You would have to compare similar missions, and look at how funding works in both countries. Its good that this team did a good low cost mission. That doesn't mean that a high cost mission that did something different was a waste.
Really. Not a snark, not a joke, I mean it. Its really fantastic that they managed a Mars mission on an extremely tight budget. Its a really difficult project and they did a fantastic job.
This sort of ultra-cheap approach might allow lots of probes to be sent to less studied bodies.
It may also be about the expected level of responsibility. A talented older worker will be in a position of considerable technical and / or managerial responsibility. If he / she tries to move out of their narrowly defined career, it may be difficult for a new employer to take the chance of giving them that much responsibility, but at the same time can't reasonably them as well for a position of less responsibility.
From what I've seen, moving within the same industry is not that difficult, but moving to a new industry is very tough for older workers.
An older worker who has lost their job (for any reason) can also be viewed as a risk. Sometimes "layoffs" really are about money but sometimes its a way of nicely firing someone. Do you trust that person to make critical decisions on your project?
Note, I'm one of those "older" workers and I don't like the idea that its very difficult to find different work, but I think I understand it .
Maybe, but the wealthy are able to live close to their jobs. It looks pretty uncomfortable so it probably won't compete with bizjets.
It might have a niche.where its useful.
Its a neat idea, even if it is a very watered down version of the 60's vacuum train concept that ran at near orbital speed. https://en.wikipedia.org/wiki/...
No fundamental physics issues, the big question is economics. The cars are pretty small and at those speeds you need a lot of spacing between trains. Curves need to be large radius and if track switching is even possible, the switches need to be very large. Its not clear that its less expensive than 350km/h high speed rail - which itself is often not cost effective.
The higher speed than high speed rail is nice for long trips (>150KM). but otherwise the boarding and accelerate /decelerate times will hide most of the difference. It will need airport like security since a relatively small bomb would kill a lot of people - sort of like an airliner, so it may be slower to board than high speed rail.
Not crazy but there isn't an obvious niche where it is cost effective (similar problems for maglev).
Considering that the argument for why distributing and owning (as opposed to producing) child porn is that the images actively harm children, I do not think there is any way to justify the FBI's behavior. I think its been generally established that law enforcement cannot commit felonies in order to gather evidence. Otherwise we could have police informants carrying out gang hits in order to capture higher level crime bosses. This is not the start of a slippery slope, it is well down the slope.
They can't have it both ways. If the images don't do actual harm to children, the people who posses the images are only guilty of a minor crime. If the images do harm children, then the FBI should destroy them as soon as they are discovered to prevent continuing harm .
On the central topic there need to be clear rules about what capabilities we want law enforcement to have. It is probably technologically possible for law enforcement to scan all of the records of the great majority of citizens to look for criminal activity. Is that what we want?
Personally I would vote to reduce surveillance and accept a higher rate of criminal activity.
I assume they have done some market research and think that $50 would be the price point that would make them the most money. Fair enough - they are a business, they have every right to set prices where they want, and consumers have every right to choose to purchase or not at that price.
$50 is more than some people can afford, and insignificant to others.
Yes. (assuming the charges can be proven).
No different from fraud or any other illegal action that puts the company at great financial risk.
We have openings for talented software people. She would be very welcome at SLAC, and our HR takes any reports of harassment seriously.
We don't have stock options, but our pay and benefits are good and the work is very interesting.
There *should* be zero tolerance for some behaviors. If someone is harassing one of their workers, in addition to behaving immorally and illegally, they are driving away talented people, and exposing the company to huge lawsuits.
Why should anyone ever be given a pass for this sort of behavior?
More minor offenses are a different matter, but a manger asking a direct report for sex is not a borderline case.
When you saw worse, did you act to stop it?