there's a big difference between having nukes, and using them. MAD.
nukes are not only a response to nuclear aggression (which has not happened), but they are also a STRONG deterrent against conventional aggression - because the aggressor has to be very willing to accept escalation. no one wants that, unless they are insane (N. Korea.. looking at you).
or perhaps they would not have invaded at all, given a potential nuclear response.
it's easy to tell other nations that they should not have nukes, sitting in a nice safe position of having lots of them. no one wants nuclear proliferation, it's a very slippery slope - but from the point of view of nations who are being stamped on, would you trust the US to come to your aid, especially given how well it worked out for Ukraine?
they were put under a 'nuclear umbrella' - but only in response to nuclear threats. and since Russia has not used nuclear weapons, the US, UK etc are free to 'ignore' the problem. Ukrainians are understandably upset that they gave up their nukes.
see how Japan might interpret this action? what if China does something that upsets Japan? will the US get involved, or come up with reasons to ignore the problem? would China be much more careful around Japan if they were nuclear armed? I think so..
I could be wrong on this, but I thought Pratt was going to be building the RD Amross (which is the american version of the RD-180) starting a couple of years ago. If that's the case then the RD-180's being used on the Atlas V are completely domestic.
no. they spent a small fortune on 'investigating the possibility' of building the engines in the US, which culminated in building one small part of an engine. then concluded that it was too expensive (a billion dollars to start production, and the US engines would also be twice the price).
RD-180s are built in Russia. they have a two year stockpile here in the US.. but ULA have just been awarded a five year block buy.
problems: turbine lag, high heat exhaust, poor fuel economy at idle/low speed. combined with a battery and electric motor system you could probably eliminate most of the problems.. except the fuel economy.
there is only a single nozzle on the grasshopper - one merlin 1D engine. the second, angled off to the side, jet of flame that you see is the low pressure exhaust from the gas generator on that engine, which has then ignited on contact with the oxygen in the air, since it runs fuel rich.
it provides very little in the way of thrust, and is not controllable on the 1D. on the merlin 1C vacuum version, it was directed and used for roll control - it appears that the merlin 1D-VAC directs the turbopump exhaust into the main engine bell to improve ISP, so presumably they plan on using cold gas or draco thrusters for upper stage roll control now.
you're correct that merlin 1D (and all the previous merlin models) use high pressure fuel from the output of the turbopump as the hydraulic fluid for gimbaling the engines - which has the nice advantage of not being able to run out of hydraulic fluid (or at least: you only run out when the engine quits firing).
'based on a Lotus Elise' would be the Tesla *Roadster* - which they haven't produced for a couple of years now. the car everyone is talking about in this story is the Model S, which is built from the ground up by Tesla as a pure electric vehicle, and is therefore a much more optimal solution.
'42% US power came from coal in 2011' - and it's dropping rapidly in most states (ie the non-coal producing ones). some states are 0% coal. doesn't matter either way. even at 42% coal, the power station is still far more efficient than an internal combustion engine (ICE is 20-25% efficient, coal power station is 80+%). that's where the official government MPG values come from - 92 MPG equivalent (based on CO2 emissions). reduce the coal percentage in your state and that MPG value climbs dramatically.
oracle uses an undo log and postgres a redo - the difference being that oracle is faster for multiple updates (and may be quicker to restart after a crash), but postgres doesn't suffer from running out of log space with large transactions, and rollback is very quick.
both postgres and oracle perform far better under locking scenarios than sqlserver.
recent postgres also have some very smart stuff if you use serializable isolation mode; supposed to be better than any other DB.
no. what they did is take the 40 year old engines and refurbish them (replace perishable seals etc), then add modern, western electronics and gimbal hardware and adjust for RP-1 rocket fuel rather than the 1970's Soviet equivalent.
whether they could actually produce new engines under the license they have is an open question - there has been a license for the RD-180 (used on the Atlas-V) for a long time, but no attempt at production has ever been made in the US. hell, they may not even be able to make new NK-33s in Russia, let alone the US - they were ordered to be scrapped and all the documentation destroyed - it was only due to a forward thinking (and brave) bureaucrat that they were warehoused and forgotten for 30 years...
these old Soviet design engines have very complex, tricky to reproduce metallurgy; that's why they are such good engines. but whether the formulas for that still exist.. who knows? they can certainly make new RD-180s in Russia, maybe the NK-33s use the same stuff, maybe not.
no, that comes later, just before MECO, and it's not to reduce dynamic pressure, it's to keep the G-forces on the payload from getting too high as the rocket loses weight (by burning fuel/oxidizer) and accelerates faster. the new F9 1.1 (yet to fly) has engine throttling capability and is supposed to throttle down around Max-Q (F9 v1 can't do that, no throttle capability) and before MECO, instead of shutting down engines.
this was definitely an unexpected problem with either the engine or the fairing around it.
that said, the rocket coped amazingly well given the spectacular loss of an engine... adjusted and compensated in real time and ended up dropping Dragon off within 2km of the target.
all that information is from a presentation by a (now) former SpaceX employee which was disavowed by the company as 'paper plans'. there's no evidence either way that any of that stuff is in progress.
the 'failed Soyuz docking attempts' (there was only one) was a result of the cash strapped Russians trying to dock *without* the automated systems (actually - they were turned off, as a test, to see if they could save money in future by not having them).
docking is easier because (a) the vehicle approaches along the V-bar and (b) the vehicle is aiming to contact a target, with some tolerance.
berthing requires (for the ISS) approaching from the R-bar, which is much harder, and also must rendezvous with a precise point in free space, ready to be grappled. it also requires a skilled robot arm operator, and doesn't allow the vehicle to be used for crew, because it cannot unberth itself without robot arm assistance.
berthing is *harder* than docking. they are doing it this way because it is a cargo transport, and the berthing ports are much larger than the docking ports.
if/when Dragon starts carrying people, it will dock.
the problem is you can't just 'fix' TCP. even if you make it work with both IPv4 TCP and IPv6 TCP, you're still missing the other protocols out there (SCTP, UDP, etc, etc), and more importantly, can NEVER fix protocols that are being encrypted (ie TCP inside VPN packets). the protocols that you aren't 'fixing' will just continue barging their way through.
the only workable solution is to drop packets and assume the protocols themselves will adjust (which they will, if they are working correctly, and if they're not working correctly.. they'll be penalized with a lot of dropped packets).
dropping packets is unpleasant, because it is wasting bandwidth, and causing TCP stalls.. but ECN barely works because half the routers out there drop or mangle it, so it's the only solution.
no, it's specifically aimed at conventional weapons, not nuclear. the point is NOT to send an ICBM, because doing so tends to make our Russian or Chinese friends get all retaliatory (even if it's not nuclear tipped.. how do they know?) - instead this thing would fly through the atmosphere and deliver a conventional payload.
it's intended to be a very, very fast cruise missile, with the objective of being able to hit any point on the planet in an hour or less.
that video is over three years old, and quite a lot has changed since then.
for example: they show an escape tower being jettisoned - there isn't going to be one now, SpaceX are working through NASA sponsored milestones to design and build a 'built in' launch abort system, which they also plan on using for landing at a later date (ie: no dunking in the sea).
they are also working on designs for crew cabin (again, part sponsored by NASA). that's what the original posting is talking about - a step in that process.
I definitely wouldn't take that video as gospel for how the piloting systems will look.
this is a duct for the J2-X rocket engine, produced using Direct Metal Laser Sintering (3D printed metal, in other words). it has to operate at insane temperatures and pressures... and it does, perfectly.
Most (if not all, Taurus II is yet to fly) of the engines in question are and will be brand new; sold profitably. Redesigned quite a few times. Put into production (or prepared for one) in "high labour cost" place.
they are cleaned, polished, given a new coat of paint and some new gaskets. a new wiring harness and modern electronics.. fired on a test stand to make sure they don't explode (and apparently a third of the NK-33s WILL explode when used.. without some fixes. that's why Taurus is delayed). but they are definitely not 'brand new'. none of those engines has been built new in decades.
But at least you, suddenly, insist that economy of rockets does matter after all...
the whole topic of discussion was about the price of *fuel*. which is insignificant compared to the rocket, engines, electronics, and payload. of course the cost of the engines makes a difference. a single engine costs ten or more times the fuel and oxidizer..
this would be the (one of) the reasons SpaceX designed a relatively simple, cheap to make, engine. it's not as efficient as the Soviet-era engines, but it's just as cheap, and can be mass produced now. that means you need to use more fuel. but guess what? the cost of the extra fuel is basically a rounding error.
for the upper stage, I absolutely agree with you - efficiency is king. but Soviet-era engines are not the best choice for that... a super high ISP kerolox engine is still 30% worse than an average hydrolox engine.
Why is that, why do ~half of US launch systems might end up with ex-Soviet / Russian engines? The staged combustion cycle, which only the Russians successfully implemented, is extremely efficient.
because they are cheap? they were built with Soviet labor, then left in warehouses to rot. found and sold to the US in the 90s for pennies on the dollar. they are VERY good engines.. but that's NOT why they're being used.
efficiency is only terribly useful for a rocket in a vacuum. that's why they're rebuilding the J2 for upper stage work (and even it's not particularly good).for first stages you need thrust. that's why the shuttle and the proposed Aries-V (cough) SLS needs expensive, dangerous solid rocket boosters strapped to it, because it's using hydrogen fueled engines which are good at ISP but not as good at thrust. Saturn-V used kerolox for the first stage for a very good reason. high thrust, not so good ISP.
When you have cheap Fuel and no Concerns about global warming. Making Bigger and Faster means transportation is easy. Fuel isn't cheap anymore. So we are trying to keep the same old stuff from the 60s but make them use less fuel a much harder engineering challenge. I want to make my car faster and fuel isn't a concern make the engine with more cylinders and grater gear ratios. But to make my car 10% more fuel efficient while keeping the existing power is much harder to do.
fuel (and oxidizer) is a TINY percentage of the cost of a rocket launch - usually less than 1% of the cost of the launch. launch vehicles are never optimized for fuel economy - they are optimized for performance above all else.
they are reusing components from the shuttle because they are still (just) available. components from Saturn V (engines, mostly) would do a far better job, but they haven't been built in decades and couldn't be reproduced for a sensible amount of money. NASA is half way through a project to reproduce a J-2 engine for the new vehicle's upper stage (the same engine was used for Saturn V upper stages 50 years ago), and it's cost a VERY large amount of money to get as far as they have.
there is also a huge dollop of politics and pork involved. re-using shuttle components keeps existing contractors (and jobs), rather than causing uncomfortable restructuring and job losses right before an election year.
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there's a big difference between having nukes, and using them. MAD.
nukes are not only a response to nuclear aggression (which has not happened), but they are also a STRONG deterrent against conventional aggression - because the aggressor has to be very willing to accept escalation. no one wants that, unless they are insane (N. Korea.. looking at you).
or perhaps they would not have invaded at all, given a potential nuclear response.
it's easy to tell other nations that they should not have nukes, sitting in a nice safe position of having lots of them. no one wants nuclear proliferation, it's a very slippery slope - but from the point of view of nations who are being stamped on, would you trust the US to come to your aid, especially given how well it worked out for Ukraine?
http://en.wikipedia.org/wiki/N...
they were put under a 'nuclear umbrella' - but only in response to nuclear threats. and since Russia has not used nuclear weapons, the US, UK etc are free to 'ignore' the problem. Ukrainians are understandably upset that they gave up their nukes.
see how Japan might interpret this action? what if China does something that upsets Japan? will the US get involved, or come up with reasons to ignore the problem? would China be much more careful around Japan if they were nuclear armed? I think so..
Yeah, this seems a bit silly.
Japan is already protected by the US nuclear program, so nothing really changes.
so was the Ukraine, in exchange for giving up their ex-Soviet nukes. see how well that worked out for them?
when push comes to shove, the US may, or may not, honor its commitments. it all depends on how much they want to go to war with China.
I could be wrong on this, but I thought Pratt was going to be building the RD Amross (which is the american version of the RD-180) starting a couple of years ago. If that's the case then the RD-180's being used on the Atlas V are completely domestic.
no. they spent a small fortune on 'investigating the possibility' of building the engines in the US, which culminated in building one small part of an engine. then concluded that it was too expensive (a billion dollars to start production, and the US engines would also be twice the price).
RD-180s are built in Russia. they have a two year stockpile here in the US.. but ULA have just been awarded a five year block buy.
Chrysler Turbine Car, from the 60's: http://en.wikipedia.org/wiki/C...
problems: turbine lag, high heat exhaust, poor fuel economy at idle/low speed. combined with a battery and electric motor system you could probably eliminate most of the problems.. except the fuel economy.
there is only a single nozzle on the grasshopper - one merlin 1D engine. the second, angled off to the side, jet of flame that you see is the low pressure exhaust from the gas generator on that engine, which has then ignited on contact with the oxygen in the air, since it runs fuel rich.
it provides very little in the way of thrust, and is not controllable on the 1D. on the merlin 1C vacuum version, it was directed and used for roll control - it appears that the merlin 1D-VAC directs the turbopump exhaust into the main engine bell to improve ISP, so presumably they plan on using cold gas or draco thrusters for upper stage roll control now.
you're correct that merlin 1D (and all the previous merlin models) use high pressure fuel from the output of the turbopump as the hydraulic fluid for gimbaling the engines - which has the nice advantage of not being able to run out of hydraulic fluid (or at least: you only run out when the engine quits firing).
'based on a Lotus Elise' would be the Tesla *Roadster* - which they haven't produced for a couple of years now. the car everyone is talking about in this story is the Model S, which is built from the ground up by Tesla as a pure electric vehicle, and is therefore a much more optimal solution.
'42% US power came from coal in 2011' - and it's dropping rapidly in most states (ie the non-coal producing ones). some states are 0% coal. doesn't matter either way. even at 42% coal, the power station is still far more efficient than an internal combustion engine (ICE is 20-25% efficient, coal power station is 80+%). that's where the official government MPG values come from - 92 MPG equivalent (based on CO2 emissions). reduce the coal percentage in your state and that MPG value climbs dramatically.
postgres uses MVCC, similar to oracle.
oracle uses an undo log and postgres a redo - the difference being that oracle is faster for multiple updates (and may be quicker to restart after a crash), but postgres doesn't suffer from running out of log space with large transactions, and rollback is very quick.
both postgres and oracle perform far better under locking scenarios than sqlserver.
recent postgres also have some very smart stuff if you use serializable isolation mode; supposed to be better than any other DB.
no. what they did is take the 40 year old engines and refurbish them (replace perishable seals etc), then add modern, western electronics and gimbal hardware and adjust for RP-1 rocket fuel rather than the 1970's Soviet equivalent.
whether they could actually produce new engines under the license they have is an open question - there has been a license for the RD-180 (used on the Atlas-V) for a long time, but no attempt at production has ever been made in the US. hell, they may not even be able to make new NK-33s in Russia, let alone the US - they were ordered to be scrapped and all the documentation destroyed - it was only due to a forward thinking (and brave) bureaucrat that they were warehoused and forgotten for 30 years...
these old Soviet design engines have very complex, tricky to reproduce metallurgy; that's why they are such good engines. but whether the formulas for that still exist.. who knows? they can certainly make new RD-180s in Russia, maybe the NK-33s use the same stuff, maybe not.
the battery system is also "human rated", since the capsule is rated that way - astronauts are working in it once it is berthed to the ISS.
no, that comes later, just before MECO, and it's not to reduce dynamic pressure, it's to keep the G-forces on the payload from getting too high as the rocket loses weight (by burning fuel/oxidizer) and accelerates faster. the new F9 1.1 (yet to fly) has engine throttling capability and is supposed to throttle down around Max-Q (F9 v1 can't do that, no throttle capability) and before MECO, instead of shutting down engines.
this was definitely an unexpected problem with either the engine or the fairing around it.
that said, the rocket coped amazingly well given the spectacular loss of an engine... adjusted and compensated in real time and ended up dropping Dragon off within 2km of the target.
no, it's exactly the same size capsule. just replaced cargo racks with seats, controls, windows, environmental controls.
all that information is from a presentation by a (now) former SpaceX employee which was disavowed by the company as 'paper plans'. there's no evidence either way that any of that stuff is in progress.
the 'failed Soyuz docking attempts' (there was only one) was a result of the cash strapped Russians trying to dock *without* the automated systems (actually - they were turned off, as a test, to see if they could save money in future by not having them).
docking is easier because (a) the vehicle approaches along the V-bar and (b) the vehicle is aiming to contact a target, with some tolerance.
berthing requires (for the ISS) approaching from the R-bar, which is much harder, and also must rendezvous with a precise point in free space, ready to be grappled. it also requires a skilled robot arm operator, and doesn't allow the vehicle to be used for crew, because it cannot unberth itself without robot arm assistance.
berthing is *harder* than docking. they are doing it this way because it is a cargo transport, and the berthing ports are much larger than the docking ports.
if/when Dragon starts carrying people, it will dock.
the problem is you can't just 'fix' TCP. even if you make it work with both IPv4 TCP and IPv6 TCP, you're still missing the other protocols out there (SCTP, UDP, etc, etc), and more importantly, can NEVER fix protocols that are being encrypted (ie TCP inside VPN packets). the protocols that you aren't 'fixing' will just continue barging their way through.
the only workable solution is to drop packets and assume the protocols themselves will adjust (which they will, if they are working correctly, and if they're not working correctly.. they'll be penalized with a lot of dropped packets).
dropping packets is unpleasant, because it is wasting bandwidth, and causing TCP stalls.. but ECN barely works because half the routers out there drop or mangle it, so it's the only solution.
no, it's specifically aimed at conventional weapons, not nuclear. the point is NOT to send an ICBM, because doing so tends to make our Russian or Chinese friends get all retaliatory (even if it's not nuclear tipped.. how do they know?) - instead this thing would fly through the atmosphere and deliver a conventional payload.
it's intended to be a very, very fast cruise missile, with the objective of being able to hit any point on the planet in an hour or less.
that video is over three years old, and quite a lot has changed since then.
for example: they show an escape tower being jettisoned - there isn't going to be one now, SpaceX are working through NASA sponsored milestones to design and build a 'built in' launch abort system, which they also plan on using for landing at a later date (ie: no dunking in the sea).
they are also working on designs for crew cabin (again, part sponsored by NASA). that's what the original posting is talking about - a step in that process.
I definitely wouldn't take that video as gospel for how the piloting systems will look.
the major reason none of the web servers support multiplexed fastcgi is that none of the fastcgi servers support it (ie PHP etc).
that said, there is a third party module for nginx to provide multiplexed fastcgi.. ie comes with demo fastcgi servers to test with.
https://github.com/rsms/afcgi
that site seems to be getting hammered... try this cached copy:
http://www.free-photos.biz/photographs/science/astronomy/67895_c_venera09_processed.php
I have a counterpoint:
http://blogs.nasa.gov/cm/blog/J2X/posts/post_1297869180794.html
this is a duct for the J2-X rocket engine, produced using Direct Metal Laser Sintering (3D printed metal, in other words). it has to operate at insane temperatures and pressures... and it does, perfectly.
Most (if not all, Taurus II is yet to fly) of the engines in question are and will be brand new; sold profitably. Redesigned quite a few times. Put into production (or prepared for one) in "high labour cost" place.
they are cleaned, polished, given a new coat of paint and some new gaskets. a new wiring harness and modern electronics.. fired on a test stand to make sure they don't explode (and apparently a third of the NK-33s WILL explode when used.. without some fixes. that's why Taurus is delayed). but they are definitely not 'brand new'. none of those engines has been built new in decades.
But at least you, suddenly, insist that economy of rockets does matter after all...
the whole topic of discussion was about the price of *fuel*. which is insignificant compared to the rocket, engines, electronics, and payload. of course the cost of the engines makes a difference. a single engine costs ten or more times the fuel and oxidizer..
this would be the (one of) the reasons SpaceX designed a relatively simple, cheap to make, engine. it's not as efficient as the Soviet-era engines, but it's just as cheap, and can be mass produced now. that means you need to use more fuel. but guess what? the cost of the extra fuel is basically a rounding error.
for the upper stage, I absolutely agree with you - efficiency is king. but Soviet-era engines are not the best choice for that... a super high ISP kerolox engine is still 30% worse than an average hydrolox engine.
Why is that, why do ~half of US launch systems might end up with ex-Soviet / Russian engines? The staged combustion cycle, which only the Russians successfully implemented, is extremely efficient.
because they are cheap? they were built with Soviet labor, then left in warehouses to rot. found and sold to the US in the 90s for pennies on the dollar. they are VERY good engines.. but that's NOT why they're being used.
efficiency is only terribly useful for a rocket in a vacuum. that's why they're rebuilding the J2 for upper stage work (and even it's not particularly good).for first stages you need thrust. that's why the shuttle and the proposed Aries-V (cough) SLS needs expensive, dangerous solid rocket boosters strapped to it, because it's using hydrogen fueled engines which are good at ISP but not as good at thrust. Saturn-V used kerolox for the first stage for a very good reason. high thrust, not so good ISP.
When you have cheap Fuel and no Concerns about global warming. Making Bigger and Faster means transportation is easy. Fuel isn't cheap anymore. So we are trying to keep the same old stuff from the 60s but make them use less fuel a much harder engineering challenge. I want to make my car faster and fuel isn't a concern make the engine with more cylinders and grater gear ratios. But to make my car 10% more fuel efficient while keeping the existing power is much harder to do.
fuel (and oxidizer) is a TINY percentage of the cost of a rocket launch - usually less than 1% of the cost of the launch. launch vehicles are never optimized for fuel economy - they are optimized for performance above all else.
they are reusing components from the shuttle because they are still (just) available. components from Saturn V (engines, mostly) would do a far better job, but they haven't been built in decades and couldn't be reproduced for a sensible amount of money. NASA is half way through a project to reproduce a J-2 engine for the new vehicle's upper stage (the same engine was used for Saturn V upper stages 50 years ago), and it's cost a VERY large amount of money to get as far as they have.
there is also a huge dollop of politics and pork involved. re-using shuttle components keeps existing contractors (and jobs), rather than causing uncomfortable restructuring and job losses right before an election year.