That's compared to a few hundred pounds for an equivalent chemical rocket. The point of post you are replying to is absolutely correct, it only makes sense if the rocket using it is large and carries a large amount of propellant.
There are effectively two factors in rocket design - the engine ISP and the mass ratio. The mass ratio is a measure of how much propellant is carried VS the dead weight (engine, tanks, payload). Those two things can tell you the velocity change of the rocket (see: "rocket equation"). Note that you have to recognize that the ISP and exhaust velocity are one and the same to make sense of it.
The ISP is twice as good as a chemical rocket, but the dead weight is very high, too, so for this to make sense, you need a large amount of propellant. The difference between 250 lbs (chemical rocket weight) and a few thousand (practical lower end of the NTP and associated shielding, etc) could be critical.
For example, using hydrogen as a working fluid increases the ISP (the lighter the exhaust products, the better) but reduces the mass ratio because the density is so low, the tanks have to be gigantic and therefore heavy. reducing the mass ratio. If it used Xenon, it might have lower ISP but the dead weight would be smaller due to much smaller fuel tanks. It's a trade-off, and NTP engines don't care very much what fuel they use.
Someone has already figured all this out, there was a perfectly sound design for a rocket upper stage using a NERVA engine, I would suggest that as a point for further research.
In this case, it's absurdly beside the point as well. The expenditure of nuclear materials is utterly irrelevant to the problem.
The way to rocket works it to use nuclear-generated heat to expand and accelerate a working fluid (usually hydrogen) and shoot it out the nozzle. What matter is the mass of the working fluid expended per impulse (force x time) - the specific impulse (lb-sec/lb or kg-sec/kg, for units of seconds) or ISP. T
housands and thousands of lbs of the working fluid will be consumed, the fact that it also consume a few ounces of nuclear material, too, is utterly in the noise.
A very good chemical rocket will have an ISP of 450-460 seconds. A nuclear thermal rocket will have an ISP of around 900-1000, or roughly twice as "good". "Good" is defined by the amount of impulse/momentum change you get for a given amount of fuel consumed.
A nuclear thermal engine can be built to provide almost any desired thrust level, with 25000 lb thrust engines actually built and tested.
By comparison, a Hall Current or other ion engine will have an ISP of around 1800, but use vast amounts of electrical power for extremely feeble thrust of far less than a pound in typical cases.
Actually, I do get that, and/. is full of them. And they are hopeless - everybody actually doing work is stupid, and the real experts are the guys in various mom's basements who saw 'Empire' 27 times.
Sometimes, it gets the better of me.
An Ion thruster (of any variety) is not *remotely* a replacement for a nuclear thermal engine. The ISP is great but the thrust levels are (and always will be, at rational sizes) feeble. And it's very likely that massively clustering them to get the thrust up will required a nuclear reactor to power them. 6/10ths of an *ounce* of thrust for 4 kW power input.
Ion thrusters have their uses, like in gently nudging things over long periods. They are not going to replace chemical rocket or NTP engines for any sort of high-thrust application.
Correct. Then a large fraction of the government capitulated, formed a puppet government, and did the Nazis' bidding, including rounding up people for shipment to concentration camps. And in some cases, like in North Africa, fought (weakly) against the allies.
At the same time, the parts of the government and military that were caught in or escaped to England made themselves royal pains in the ass to the allies, posturing and playing politics to try to claim they were in charge of the government in abstentia, This greatly complicated the invasion planning and led to poor tactical decisions based on maintain the pride of strutting martinets like DeGaulle. This allowed the Germans to escape through the Falaise gap, for example, when they were otherwise going to be caught. This probably extended the war another 6 months.
The ultimate was in the 60s. DeGaulle demanded that all American tropps be removed from French soil. Lyndon Johnson asked him "does that include the 65000 that died lliberarting it*.
You are probably right about the confirmation bias. But one should be able to make that argument without hounding someone out of a profession. That is more-or-less what happened here.
I would also note that almost no one here is actually a scientist, much less a Nobel prize winner. So no one is all that qualified to debunk his idea. There are certainly falsifiable points in his premise on race (and probably plenty of research to support it). All that need be done is produce and make the argument, and the issue should be closed. But no, that's not sufficient, he has to be punished.
This is a classic case of claims of "Science!" being used as a cover for political correctness. More like "Science! (so shut the hell up)".
Of course it's a familiar cultural setting. Unless the nature of the culture and social interactions is the theme, you would rather have something that the reader can relate to. You need to relate it to something the reader will understand, because, otherwise, you will either use up inordinate space and words describing it, or leave the entire thing unexplained which loses the reader.
Moreover, human nature hasn't changed consequentially for 10,000 years. The same motivations, reactions, and through processes are on some level universal. The culture *hasn't* changed all that much at the root level. The means and mechanism, and superficially changes, but deep down nothing is really all that different since the development of "civilization" coincident with the agricultural revolution.
The components were already at the minimum operating temperature. You can't just let everything cool to the background, then hope to heat it back up later. Something will likely break. There have been survival heaters and (in this case) thermal shunts from the RTG to keep it warm enough the entire time.
How the mighty have fallen. First, a Roman god, 2000 years later, you live in a doghouse and take orders (confusingly) from *another dog* - and a dimwitted country hick dog, at that.
I agree that the OP is not getting it right but that is not the case. In fact, there were numerous Apollo-related unmanned test flights before the fire, and there were several planned after the nominal launch of AS-204 (renamed Apollo 1 later). In particular, what was later termed Apollo 4 was always planned to be an unmanned mission, as was 6. The only mission definition changes were to remove all the Block I CSM missions in favor of the Block II (which was already in planning, but were also altered due to the findings in the fire investigation) and the launch of the Apollo 5 which originally was intended to go on a manned Saturn V launch but instead was put as a LM-solo mission (obviously unmanned) mission on the Saturn 1b previously assigned to the mission that caught fire. Some other missions, particularly which LM abort cases needed to be run, were still undefined but they were always manned.
It's "eerily similar" because they are testing the same test points they did before. The fact that a previous spacecraft built with 50's aerospace technology managed to do it doesn't mean that much. We know what to expect, but you still have to actually build what you are planning to fly, and then fly it and see. You can't just simulate everything, assume the simulation is correct, and then shoot it off with 3 people in it on national TV.
In many ways, the added complexity made possible by much more computing power might be a liability in some ways. Radiation doesn't hurt a toggle switch.
Most of the command module avionics, control system, fore and aft heat shield, power and thermal subsystem, and recovery systems like the parachute system.
Right, this is the first ever launch delay or abort. Except for almost all of the Mercury flights, two pad aborts on Gemini, 3-4 launch slips on Apollo, alternate launch window launch on Apollo 16, repeated shuttle launch delays and scrubs, It happens all the time, all the preparation in the world will not prevent them, and it has nothing to do with "newbies" in the process.
And in fact, since this is a ULA Delta launch, with NASA personnel who formerly ran the Shuttle and ISS operations, I would estimate based on my personal knowledge that they have several orders of magnitude more launch experience that most of the mission control people on Apollo ever had.
Moreover, in Episode 2f09, Itchy plays Scratchy's ribs like a xylophone, and he strikes the same rib twice but it makes two clearly distinct tones. Are we supposed to believe it's some sort of magic xylophone or something?
Slashdot Mirror
This is a pretty facile assessment. The safest possible approach would be to ban the plants entirely. Once you dismiss that, then it's a trade-off.
That's compared to a few hundred pounds for an equivalent chemical rocket. The point of post you are replying to is absolutely correct, it only makes sense if the rocket using it is large and carries a large amount of propellant.
There are effectively two factors in rocket design - the engine ISP and the mass ratio. The mass ratio is a measure of how much propellant is carried VS the dead weight (engine, tanks, payload). Those two things can tell you the velocity change of the rocket (see: "rocket equation"). Note that you have to recognize that the ISP and exhaust velocity are one and the same to make sense of it.
The ISP is twice as good as a chemical rocket, but the dead weight is very high, too, so for this to make sense, you need a large amount of propellant. The difference between 250 lbs (chemical rocket weight) and a few thousand (practical lower end of the NTP and associated shielding, etc) could be critical.
For example, using hydrogen as a working fluid increases the ISP (the lighter the exhaust products, the better) but reduces the mass ratio because the density is so low, the tanks have to be gigantic and therefore heavy. reducing the mass ratio. If it used Xenon, it might have lower ISP but the dead weight would be smaller due to much smaller fuel tanks. It's a trade-off, and NTP engines don't care very much what fuel they use.
Someone has already figured all this out, there was a perfectly sound design for a rocket upper stage using a NERVA engine, I would suggest that as a point for further research.
In this case, it's absurdly beside the point as well. The expenditure of nuclear materials is utterly irrelevant to the problem.
The way to rocket works it to use nuclear-generated heat to expand and accelerate a working fluid (usually hydrogen) and shoot it out the nozzle. What matter is the mass of the working fluid expended per impulse (force x time) - the specific impulse (lb-sec/lb or kg-sec/kg, for units of seconds) or ISP. T
housands and thousands of lbs of the working fluid will be consumed, the fact that it also consume a few ounces of nuclear material, too, is utterly in the noise.
A very good chemical rocket will have an ISP of 450-460 seconds. A nuclear thermal rocket will have an ISP of around 900-1000, or roughly twice as "good". "Good" is defined by the amount of impulse/momentum change you get for a given amount of fuel consumed.
A nuclear thermal engine can be built to provide almost any desired thrust level, with 25000 lb thrust engines actually built and tested.
By comparison, a Hall Current or other ion engine will have an ISP of around 1800, but use vast amounts of electrical power for extremely feeble thrust of far less than a pound in typical cases.
Actually, I do get that, and /. is full of them. And they are hopeless - everybody actually doing work is stupid, and the real experts are the guys in various mom's basements who saw 'Empire' 27 times.
Sometimes, it gets the better of me.
An Ion thruster (of any variety) is not *remotely* a replacement for a nuclear thermal engine. The ISP is great but the thrust levels are (and always will be, at rational sizes) feeble. And it's very likely that massively clustering them to get the thrust up will required a nuclear reactor to power them. 6/10ths of an *ounce* of thrust for 4 kW power input.
Ion thrusters have their uses, like in gently nudging things over long periods. They are not going to replace chemical rocket or NTP engines for any sort of high-thrust application.
Right, the politicians will have to answer some tough questions. Politicians with constituents that work at ULA, in some case, in large numbers.
Too bad there's no "Johnny Dangerously" bonus mod point. Perhaps there should be
Ah, so he's an idiot.
Correct. Then a large fraction of the government capitulated, formed a puppet government, and did the Nazis' bidding, including rounding up people for shipment to concentration camps. And in some cases, like in North Africa, fought (weakly) against the allies.
At the same time, the parts of the government and military that were caught in or escaped to England made themselves royal pains in the ass to the allies, posturing and playing politics to try to claim they were in charge of the government in abstentia, This greatly complicated the invasion planning and led to poor tactical decisions based on maintain the pride of strutting martinets like DeGaulle. This allowed the Germans to escape through the Falaise gap, for example, when they were otherwise going to be caught. This probably extended the war another 6 months.
The ultimate was in the 60s. DeGaulle demanded that all American tropps be removed from French soil. Lyndon Johnson asked him "does that include the 65000 that died lliberarting it*.
That's why we hate the French.
I don't care what you say. Say whatever you want, I am a conservative, so I don't think it's a good idea to censor speech.
Thwe Watson case is an absolutely classic case of PC bullying.
The latter is exactly my point. I would think the man's premise would be quickly and easily refuted. And it was and is.
But the "community" couldn't let it go at that. He had to be punished for the way he thought, because it made everybody feel better.
You are probably right about the confirmation bias. But one should be able to make that argument without hounding someone out of a profession. That is more-or-less what happened here.
I would also note that almost no one here is actually a scientist, much less a Nobel prize winner. So no one is all that qualified to debunk his idea. There are certainly falsifiable points in his premise on race (and probably plenty of research to support it). All that need be done is produce and make the argument, and the issue should be closed. But no, that's not sufficient, he has to be punished.
This is a classic case of claims of "Science!" being used as a cover for political correctness. More like "Science! (so shut the hell up)".
Of course it's a familiar cultural setting. Unless the nature of the culture and social interactions is the theme, you would rather have something that the reader can relate to. You need to relate it to something the reader will understand, because, otherwise, you will either use up inordinate space and words describing it, or leave the entire thing unexplained which loses the reader.
Moreover, human nature hasn't changed consequentially for 10,000 years. The same motivations, reactions, and through processes are on some level universal. The culture *hasn't* changed all that much at the root level. The means and mechanism, and superficially changes, but deep down nothing is really all that different since the development of "civilization" coincident with the agricultural revolution.
The components were already at the minimum operating temperature. You can't just let everything cool to the background, then hope to heat it back up later. Something will likely break. There have been survival heaters and (in this case) thermal shunts from the RTG to keep it warm enough the entire time.
How the mighty have fallen. First, a Roman god, 2000 years later, you live in a doghouse and take orders (confusingly) from *another dog* - and a dimwitted country hick dog, at that.
I agree that the OP is not getting it right but that is not the case. In fact, there were numerous Apollo-related unmanned test flights before the fire, and there were several planned after the nominal launch of AS-204 (renamed Apollo 1 later). In particular, what was later termed Apollo 4 was always planned to be an unmanned mission, as was 6. The only mission definition changes were to remove all the Block I CSM missions in favor of the Block II (which was already in planning, but were also altered due to the findings in the fire investigation) and the launch of the Apollo 5 which originally was intended to go on a manned Saturn V launch but instead was put as a LM-solo mission (obviously unmanned) mission on the Saturn 1b previously assigned to the mission that caught fire. Some other missions, particularly which LM abort cases needed to be run, were still undefined but they were always manned.
It's "eerily similar" because they are testing the same test points they did before. The fact that a previous spacecraft built with 50's aerospace technology managed to do it doesn't mean that much. We know what to expect, but you still have to actually build what you are planning to fly, and then fly it and see. You can't just simulate everything, assume the simulation is correct, and then shoot it off with 3 people in it on national TV.
In many ways, the added complexity made possible by much more computing power might be a liability in some ways. Radiation doesn't hurt a toggle switch.
Most of the command module avionics, control system, fore and aft heat shield, power and thermal subsystem, and recovery systems like the parachute system.
Quite a few things, actually,
Right, this is the first ever launch delay or abort. Except for almost all of the Mercury flights, two pad aborts on Gemini, 3-4 launch slips on Apollo, alternate launch window launch on Apollo 16, repeated shuttle launch delays and scrubs, It happens all the time, all the preparation in the world will not prevent them, and it has nothing to do with "newbies" in the process.
And in fact, since this is a ULA Delta launch, with NASA personnel who formerly ran the Shuttle and ISS operations, I would estimate based on my personal knowledge that they have several orders of magnitude more launch experience that most of the mission control people on Apollo ever had.
Other than that, you are absolutely correct.
Check the scoreboard, ace.
Number of manned missions launched be NASA - ~150.
Number of manned missions launched by ESA - 0 and none planned.
It's *really easy* to never fail - as long as you never try.
I sure hope I can use the IoT to control a monorail!
Of course, it's classic stoner logic. It makes you stupid, therefore stupid ideas seem like genius.
Moreover, in Episode 2f09, Itchy plays Scratchy's ribs like a xylophone, and he strikes the same rib twice but it makes two clearly distinct tones. Are we supposed to believe it's some sort of magic xylophone or something?
Because its the latest cause celebre' for leftists.
Now see, THIS, gentlemen, is how to sling bullshit. Please make a note of it.