The idea of using wingtip devices to control vorticies has been around for over 100 years. Frederick Lanchester (a conteporary of Prandtl) secured a patent in 1897 for the use of "bent up wing tips" to control tip vorticies. He was working on those theories at the same time the Wright brothers were trying to learn how to fly. It took 20 years for aerodynamicists to prove his theories correct.
That's one of the problems with controls theory. Three basic situations occur: Critically Damped, Over-Damped, and Under-Damped. None of which sound particularly good if you don't know what they mean. "Critically" is usually not a term used for anything benificial (eg Critical Condition), Over-Damped just sounds opressive, and Under-Damped sounds just as bad in the opposite direction. So basically, within controls theory, you're really damped if you do and damped if you don't.
Admittedly when I wrote the second part of my previous post I was thinking scramjet not ramjet. You're right that ramjets have fairly simple relatively conical geometries, except for the inlet and nozzle the whole thing is basically one big combustion chamber. The solid fuel ramjets that you mentioned are good for relatively steady velocity applications, throttling is very limited with that particular type of engine due to fuel injection via ablation.
That doesn't mean that rocket powered ramjets would work for this application however. The biggest challenge with an integrated rocket/ramjet is the nozzle requirements for the two stages are completely different. The exhaust gasses from the rocket motor are traveling much faster than the exhaust from the ramjet which means one of two things: You could design a compromise nozzle (or leaving it completely nozzleless) which would provide marginal performance for both, or you could have a separate nozzle just for the rocket portion of flight which would be discarded after burnout of the motor.
The real problem with using this type of application on an aircraft like the SR-72 (or whatever they're going to call it) is you're not going to be able to have a powered landing. The rocket motor will accelerate from rest to a speed at which the ramjet will be able to operate, but unless you're going to destroy the UAV each flight (much like the D-21 drone) you're not going to be able to slow down beyond the lower operating range of the ramjet. Some might consider this a non-issue since it is a UAV and we could always build more... but that just seems wasteful to me.
I think you're thinking of modern cruise missles which use a solid rocket motor which is jettisoned before starting a small turbine engine for the rest of the trip.
The problem with filling a ramjet full of solid fuel is that the irregular shape of the ramjets interior will cause irregular burn speeds in the solid fuel creating uneven thrust. Using certain catalysts the burn rate of the fuel can be managed somewhat, but these burn rate modifiers would have to be precisely positioned inside the ramjet in order to compensate for the geometry changes. Manufacturing such precision solid fuel would be difficult to say the least. Not to mention having a controlled explosion travelling the opposite direction of the typical flow of the ramjet would most likely cause damage to the intricate geometry of the engine.
Not quite...
"Conventional" wisdom now says that then president Lyndon B. Johnson messed up the designation in his public announcement and called it the SR-71 - and nobody wanted to correct the president. Because the strike mission had been cancelled anyway, "SR" was quickly reinterpreted as "Strategic Reconnaissance". However, a first-hand witness of those events recently revealed in Aviation Week & Space Technology, that LBJ did not misread anything. In fact, then USAF Chief of Staff LeMay simply didn't like the "RS" designator - he already objected it when the RS-70 was discussed, preferring "SR-70". When the RS-71 was to be announced, he wanted to make sure it would be called SR-71 instead. He managed to have LBJ's speech script altered to show "SR-71" in all places. Using archived copies of LBJ's speech, it can actually be verified that it reads SR-71 both in the script and on the tape recording. However, the official transcript of the speech, created from the stenographic records and handed to the press afterwards, shows "RS-71" in three places. It seems that not the president but a stenographer did accidentally switch the letters, and thus create a famous aviation "urban legend".http://www.designation-systems.net/usmilav/nonstan dard-mds.html#_MDS_SR71
The whole reason these patterns are attracting so much attention is because they don't explicitly repeat themselves yet they still show a rotational symmetry. Making crystaline structures isn't very difficult mathematically. Crystals are very ordered and neat, repeating themselves ad infinitum. Quasicrystals on the other hand are very complex mathematically because of their aperiodic structure.
The patterns found on the structures would be even more incredible if they were just random accidents. The pattern on the shrine mentioned in the article is a near perfect match to the mathematical model, the chances of that happening are very very slim. I'm not saying that this proves they knew the math behind the patterns, I'm just saying that they deliberately created the patterns in such a way that we can't rule out that they didn't.
I have never heard of ANY professor selling notes. The closest thing was when one of the academic fraternities was selling old tests (with the professor's permission) as a fund raiser. Luckily I'm in the College of Engineering rather than Communication, but I know I can download full video of lectures in certain classes for free. I've downloaded semester's worth of video lectures for courses I haven't even taken yet (mostly graduate courses for subjects I'm interested in). This professor's just trying to make a quick buck off his students and they're stupid enough to buy into it.
Go to class, take notes, if you need to review further look over your notes after class and go to office hours. If you miss a class, get the notes from someone else in the class or study from the book on your own. It's not that hard, especially for a 200-level Communication course.
I worked at the UPS Hub in Raleigh, NC for about a year while in college. Your loading technique is dead wrong. The trucks are all loaded front to back stacking as you go with the ideal situation being all available space used up floor to ceiling. Does stuff get thrown on top? Of course, but you don't fill the back of the truck first then throw the packages towards the front, that's a complete waste of space. I don't know about hubs out in CA but if we did that our managers would have our asses since they didn't like calling for new trucks multiple times in one night.
What you are right about though is the conveyor belts. Those would do more damage to packages than any human could ever attempt to do with their bare hands. There were many nights when I'd just run up and down the conveyor belt breaking jams of packages (yes walking on the conveyor belt would get you fired too but most people turned a blind eye to it since they wanted their numbers for the shift and didn't care as long as people could still load the trucks). I actually got bored one weekend and came up with a few design modifications for the belts and slides that would minimize package jams, but what did they do? "We can't spend money to retrofit all these belts, it's a nice thought though."
So the next time your box comes from UPS (or FedEx, or DHL) looking like an accordian, it's most likely not the loader's fault.
They don't specify the eccentricity of the ellipse however they do specify the period and the material that makes up their "sun". From a few simple calculations you can figure it out:
T=3000 rev/year => 9.5066x10^-5 rev/s take the inverse P = 10519.007s (some rounding error)
mu is known as the standard gravitational parameter, and can be found by multiplying the mass of the object by the universal gravitational constant:
mu = G*m
to find the mass take the volume of a sphere of diameter 8cm (FTA) and multiply it by the density of tungsten:
m = V*rho
V = (4/3)*pi*r^3 = (4/3)*pi*(4cm)^3
= 268.08 cm^3
rho = 19.25 gm/cm^3
m = (268.08 cm^3)(19.25 gm/cm^3)
= 5160.589gm
= 5.160 kg
mu = G*m
= (6.6742x10^-11 m^3*s^-2*kg^-1)(5.16 kg)
= 3.443 m^3/s^2
Using mu and the period P, we can find the semimajor axis a:
P = 2*pi*sqrt(a^3/mu)
solving for a:
a = (P^(2/3)*(2*mu)^(1/3))*(2*pi^(2/3))^-1
plugging all those fun numbers in:
a = 212.838 m
from there we can find the eccentricity by the formula:
e = 1-(r_p/a)
r_p is the radius at the periapsis of the orbit (the closest point in the orbital path to the mass it is orbiting).
FTA the "planet" will be launched 10cm away into an oval shaped orbit. For an arbitrary assumption, we'll take 10cm to be the periapsis of this orbit.
That would put the eccentricity at e=.99953, which is extremely close to the eccentricity of a parabolic trajectory of e=1, so 10cm is most likely not the periapsis of the orbit.
However since the semimajor axis of the orbit is so large compared to the initial given value of 10cm, it wouldn't make sense for it to be at any other point in the orbit. So essentially, from the numbers given in the article we have an extremely large system (total orbital diameter is 2a = 425.676m) which would be impractical to create and launch to the legrange point.
Unfortunately I believe we have yet another case of not enough actual details in the article to come to a reasonable conclusion about the physics behind the story.
As always, if there's something wrong with the analysis or any of my calculations please point them out. It's been a while since I've done any of this stuff and mistakes do happen.
Ramjets operate at a slower speed than Scramjets so the inlet geometry is able to slow the air down to subsonic speeds by the time it gets to the combustion chamber. Much like the scramjet there are no moving parts in the engine so there are not problems with traditional compressors found in jet engines.
1. Turbines in a jet engine are located after compression and combustion occur. Compression is due to compressors located after the inlet of the engine and before the combustion chamber where fuel is introduced and ignited. From the combustion chamber the high pressure, high temperature exhaust is then fed through the turbines which then generate power for quite a few different things including running the compressors.
Engine Theroy: Suck, Squeeze, Bang, Blow.
2. Jet engines do not work at very high speed not because of stresses in the compressors/turbines but rather because of the problems with supersonic flow. For supersonic aircraft the airflow into the engine is slowed to subsonic speeds using inlet geometry to control the oblique and normal shocks in the flow. Yes, theoretically you could spin the compressor faster than it's mechanical stress limits but that would occur a lot longer after the engine stopped working due to the flow.
3. The reason hydrogen is used as fuel for the scramjet is because the pressure tolerances for the engine are extremely small. The compressed flow must maintain supersonic speed, contain enough heat to ignite the fuel, and have enough time to have initiation and reaction occur inside the combustion chamber before it's ejected out the exhaust nozzle.
The reason they're comparing a Scramjet to a rocket engine is because having a Scramjet would dramatically reduce the weight of orbital flight by not having to carry its own oxidizer. For example: 75% of the weight of the Space Shuttle during launch is stored in LOX used as fuel.
However the feasibility of using a Scramjet engine for a single stage to orbit vehicle poses problems of its own. Way too many to list here. But solutions might be found to these problems as technology increases.
Well one would think you could run just a standard TV out to get the video, and run your soundcard through your stereo amp to get the audio. Most likely your best bet would be to keep it all wired since speed would be limited via wireless. Those are just a few of my thoughts, but what do I know, I'm just a silly college student. Good luck.
Let's think about this for a second.... If we could produce our own Caffine then what would happen to Jolt soda (the choice of the Hacking Generation)?
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The idea of using wingtip devices to control vorticies has been around for over 100 years. Frederick Lanchester (a conteporary of Prandtl) secured a patent in 1897 for the use of "bent up wing tips" to control tip vorticies. He was working on those theories at the same time the Wright brothers were trying to learn how to fly. It took 20 years for aerodynamicists to prove his theories correct.
The Russians were the first to try this particular tactic against Chechnya. They called it the "InterNyet".
That's one of the problems with controls theory. Three basic situations occur: Critically Damped, Over-Damped, and Under-Damped. None of which sound particularly good if you don't know what they mean. "Critically" is usually not a term used for anything benificial (eg Critical Condition), Over-Damped just sounds opressive, and Under-Damped sounds just as bad in the opposite direction. So basically, within controls theory, you're really damped if you do and damped if you don't.
Admittedly when I wrote the second part of my previous post I was thinking scramjet not ramjet. You're right that ramjets have fairly simple relatively conical geometries, except for the inlet and nozzle the whole thing is basically one big combustion chamber. The solid fuel ramjets that you mentioned are good for relatively steady velocity applications, throttling is very limited with that particular type of engine due to fuel injection via ablation.
That doesn't mean that rocket powered ramjets would work for this application however. The biggest challenge with an integrated rocket/ramjet is the nozzle requirements for the two stages are completely different. The exhaust gasses from the rocket motor are traveling much faster than the exhaust from the ramjet which means one of two things: You could design a compromise nozzle (or leaving it completely nozzleless) which would provide marginal performance for both, or you could have a separate nozzle just for the rocket portion of flight which would be discarded after burnout of the motor.
The real problem with using this type of application on an aircraft like the SR-72 (or whatever they're going to call it) is you're not going to be able to have a powered landing. The rocket motor will accelerate from rest to a speed at which the ramjet will be able to operate, but unless you're going to destroy the UAV each flight (much like the D-21 drone) you're not going to be able to slow down beyond the lower operating range of the ramjet. Some might consider this a non-issue since it is a UAV and we could always build more... but that just seems wasteful to me.
I think you're thinking of modern cruise missles which use a solid rocket motor which is jettisoned before starting a small turbine engine for the rest of the trip.
The problem with filling a ramjet full of solid fuel is that the irregular shape of the ramjets interior will cause irregular burn speeds in the solid fuel creating uneven thrust. Using certain catalysts the burn rate of the fuel can be managed somewhat, but these burn rate modifiers would have to be precisely positioned inside the ramjet in order to compensate for the geometry changes. Manufacturing such precision solid fuel would be difficult to say the least. Not to mention having a controlled explosion travelling the opposite direction of the typical flow of the ramjet would most likely cause damage to the intricate geometry of the engine.
Not quite... "Conventional" wisdom now says that then president Lyndon B. Johnson messed up the designation in his public announcement and called it the SR-71 - and nobody wanted to correct the president. Because the strike mission had been cancelled anyway, "SR" was quickly reinterpreted as "Strategic Reconnaissance". However, a first-hand witness of those events recently revealed in Aviation Week & Space Technology, that LBJ did not misread anything. In fact, then USAF Chief of Staff LeMay simply didn't like the "RS" designator - he already objected it when the RS-70 was discussed, preferring "SR-70". When the RS-71 was to be announced, he wanted to make sure it would be called SR-71 instead. He managed to have LBJ's speech script altered to show "SR-71" in all places. Using archived copies of LBJ's speech, it can actually be verified that it reads SR-71 both in the script and on the tape recording. However, the official transcript of the speech, created from the stenographic records and handed to the press afterwards, shows "RS-71" in three places. It seems that not the president but a stenographer did accidentally switch the letters, and thus create a famous aviation "urban legend". http://www.designation-systems.net/usmilav/nonstan dard-mds.html#_MDS_SR71
That's actually the very end of the television ad that was pulled.
The whole reason these patterns are attracting so much attention is because they don't explicitly repeat themselves yet they still show a rotational symmetry. Making crystaline structures isn't very difficult mathematically. Crystals are very ordered and neat, repeating themselves ad infinitum. Quasicrystals on the other hand are very complex mathematically because of their aperiodic structure.
The patterns found on the structures would be even more incredible if they were just random accidents. The pattern on the shrine mentioned in the article is a near perfect match to the mathematical model, the chances of that happening are very very slim. I'm not saying that this proves they knew the math behind the patterns, I'm just saying that they deliberately created the patterns in such a way that we can't rule out that they didn't.
Check out http://intendo.net/penrose/info.html for more on the math behind the patterns.
I have never heard of ANY professor selling notes. The closest thing was when one of the academic fraternities was selling old tests (with the professor's permission) as a fund raiser. Luckily I'm in the College of Engineering rather than Communication, but I know I can download full video of lectures in certain classes for free. I've downloaded semester's worth of video lectures for courses I haven't even taken yet (mostly graduate courses for subjects I'm interested in). This professor's just trying to make a quick buck off his students and they're stupid enough to buy into it.
Go to class, take notes, if you need to review further look over your notes after class and go to office hours. If you miss a class, get the notes from someone else in the class or study from the book on your own. It's not that hard, especially for a 200-level Communication course.
I worked at the UPS Hub in Raleigh, NC for about a year while in college. Your loading technique is dead wrong. The trucks are all loaded front to back stacking as you go with the ideal situation being all available space used up floor to ceiling. Does stuff get thrown on top? Of course, but you don't fill the back of the truck first then throw the packages towards the front, that's a complete waste of space. I don't know about hubs out in CA but if we did that our managers would have our asses since they didn't like calling for new trucks multiple times in one night.
What you are right about though is the conveyor belts. Those would do more damage to packages than any human could ever attempt to do with their bare hands. There were many nights when I'd just run up and down the conveyor belt breaking jams of packages (yes walking on the conveyor belt would get you fired too but most people turned a blind eye to it since they wanted their numbers for the shift and didn't care as long as people could still load the trucks). I actually got bored one weekend and came up with a few design modifications for the belts and slides that would minimize package jams, but what did they do? "We can't spend money to retrofit all these belts, it's a nice thought though."
So the next time your box comes from UPS (or FedEx, or DHL) looking like an accordian, it's most likely not the loader's fault.
They don't specify the eccentricity of the ellipse however they do specify the period and the material that makes up their "sun". From a few simple calculations you can figure it out:
T=3000 rev/year => 9.5066x10^-5 rev/s
take the inverse
P = 10519.007s (some rounding error)
mu is known as the standard gravitational parameter, and can be found by multiplying the mass of the object by the universal gravitational constant:
mu = G*m
to find the mass take the volume of a sphere of diameter 8cm (FTA) and multiply it by the density of tungsten:
m = V*rho
V = (4/3)*pi*r^3 = (4/3)*pi*(4cm)^3
= 268.08 cm^3
rho = 19.25 gm/cm^3
m = (268.08 cm^3)(19.25 gm/cm^3)
= 5160.589gm
= 5.160 kg
mu = G*m
= (6.6742x10^-11 m^3*s^-2*kg^-1)(5.16 kg)
= 3.443 m^3/s^2
Using mu and the period P, we can find the semimajor axis a:
P = 2*pi*sqrt(a^3/mu)
solving for a:
a = (P^(2/3)*(2*mu)^(1/3))*(2*pi^(2/3))^-1
plugging all those fun numbers in:
a = 212.838 m
from there we can find the eccentricity by the formula:
e = 1-(r_p/a)
r_p is the radius at the periapsis of the orbit (the closest point in the orbital path to the mass it is orbiting).
FTA the "planet" will be launched 10cm away into an oval shaped orbit. For an arbitrary assumption, we'll take 10cm to be the periapsis of this orbit.
That would put the eccentricity at e=.99953, which is extremely close to the eccentricity of a parabolic trajectory of e=1, so 10cm is most likely not the periapsis of the orbit.
However since the semimajor axis of the orbit is so large compared to the initial given value of 10cm, it wouldn't make sense for it to be at any other point in the orbit. So essentially, from the numbers given in the article we have an extremely large system (total orbital diameter is 2a = 425.676m) which would be impractical to create and launch to the legrange point.
Unfortunately I believe we have yet another case of not enough actual details in the article to come to a reasonable conclusion about the physics behind the story.
As always, if there's something wrong with the analysis or any of my calculations please point them out. It's been a while since I've done any of this stuff and mistakes do happen.
Ramjets operate at a slower speed than Scramjets so the inlet geometry is able to slow the air down to subsonic speeds by the time it gets to the combustion chamber. Much like the scramjet there are no moving parts in the engine so there are not problems with traditional compressors found in jet engines.
I'm not even sure where to start with this one...
1. Turbines in a jet engine are located after compression and combustion occur. Compression is due to compressors located after the inlet of the engine and before the combustion chamber where fuel is introduced and ignited. From the combustion chamber the high pressure, high temperature exhaust is then fed through the turbines which then generate power for quite a few different things including running the compressors.
Engine Theroy: Suck, Squeeze, Bang, Blow.
2. Jet engines do not work at very high speed not because of stresses in the compressors/turbines but rather because of the problems with supersonic flow. For supersonic aircraft the airflow into the engine is slowed to subsonic speeds using inlet geometry to control the oblique and normal shocks in the flow. Yes, theoretically you could spin the compressor faster than it's mechanical stress limits but that would occur a lot longer after the engine stopped working due to the flow.
3. The reason hydrogen is used as fuel for the scramjet is because the pressure tolerances for the engine are extremely small. The compressed flow must maintain supersonic speed, contain enough heat to ignite the fuel, and have enough time to have initiation and reaction occur inside the combustion chamber before it's ejected out the exhaust nozzle.
The reason they're comparing a Scramjet to a rocket engine is because having a Scramjet would dramatically reduce the weight of orbital flight by not having to carry its own oxidizer. For example: 75% of the weight of the Space Shuttle during launch is stored in LOX used as fuel.
However the feasibility of using a Scramjet engine for a single stage to orbit vehicle poses problems of its own. Way too many to list here. But solutions might be found to these problems as technology increases.
Well one would think you could run just a standard TV out to get the video, and run your soundcard through your stereo amp to get the audio. Most likely your best bet would be to keep it all wired since speed would be limited via wireless. Those are just a few of my thoughts, but what do I know, I'm just a silly college student. Good luck.
So basically this is saying:
"All your idea are belong to Microsoft."
Let's think about this for a second.... If we could produce our own Caffine then what would happen to Jolt soda (the choice of the Hacking Generation)?