The SR-71 is not airframe limited, but limited by the two P&W J58 powerplants.
The supersonic air has to be slowed down to subsonic speeds to burn. At a flight Mach number 3.5 the temperature rise from the succesive oblique shocks and single normal shock raise the temperature of the air to just below the flame temperature of a stoichiometric kerosene-air mixture. On top of this, the temperature of the exhaust gas is approaching the thermal limit of the turbine blades. So, you're gaining incrimentally less thrust from your fuel as well as approaching other thermal limits.
On days when the upper air temp is REALLY COLD they fly just a little faster 'cause they get more thrust and have a little more margin on the exhaust gas temp.
As a side note, supersonic combustion isn't new. Not too long ago the University of Queensland designed and tested (in their own shock tunnel) a supersonic combustion ramjet that produces more thrust than drag, which is a first. The interesting thing to see with X-43 is whether it too produces more thrust than drag.
In many cases a company may also sell the stock that it owns of itself to finance its operations. If the stock price is in the toilet, then that may no longer be a viable option in terms of short term financing.
I think the sadest part is that the article from the Boston Globe seems to suggest in the first three paragraphs that it does come from space. This completely threw me off for most of the article 'cause I was stuck on the idea of how a fungus would survive in the vacuum of space.
As a practicing engineer in the aerospace business working for a private company, I'm personally and professionally insulted that you would suggest that we would not build a safe and reliable vehicle.
Aparently you lack the basic understanding of how to run a business. Yes, you have to make money. But you don't do it by killing people. If you've got four man rated spacecraft, and you loose one to an accident you face numerous problems. First, you kissed goodbye a large capital investment that can never be recovered. Second, you've brought upon yourself the hell known as the legal system, which may dog you until you're bankrupt. Third, if people believe the system is unreliable there is no way in hell they are going to fly on it, thus destroying that revenue stream. If your business is built on puting people in space, congratulations you've put yourself out of business, you're a failure and have no money. There is no incentive whatsoever to design and build an unsafe or unreliable vehicle. NONE.
The flipside is this. What if it were completely left to the government? Would it be safe? Probably. Would it be behind schedule? YES. Would it be too expensive for all but the government to be able to afford to operate it? YES. What if the gov't looses one of four vehicles to an accident? You've still lost the large capital investment. Will legal troubles dog the program? Maybe, but they won't put the gov't out of business. Will the gov't shutdown if they loose a spacecraft and crew? Nah, build another and put more people in it (baring minor modifications, that is exactly what we did after challenger). The revenue stream is not dependant on paying customers, but on people's tax dollars.
Noone forces you to smoke cigarettes. Noone forces you to drive an unsafe vehicle. Noone is going to force you to go into space. Oh, but if the gov't were left to selling cigarettes, they would be safe to smoke. Gov't cars would be high quality, safe, and affordable. Yeah. Right. Driven a Russian car lately? As bad as GM is, there are many more that are worse.
If the US gov't depended on paying customers to fly the space shuttle, they would have suspended operations back in the early 80's.
BTW, please tell me. What incentive does the government have in building a safe, reliable and affordable launch vehicle?
Space travel is inherently dangerous and you will always be worrying about safety. What does government have to loose if seven astronauts die because of a stupid decission to launch despite the objections of the engineers of the manufacturer of the solid boosters? After the chanllenger accident, did the gov't go out of business, have civil or criminal charges filed against it?
Private companies have a financial stake in providing safe and affordable access to space. The private company faces financial ruin and potentiall civil and criminal lawsuits if the screw up. If I were a private company, I'd be damn sure the vehicle was reliable and safe.
Actually, what would be kind of cool is if you could use your hybrid car to serve as a backup generator for your house. It could bring new meaning to Sport Utility Vehicles.
"Honey pull up the hybrid sports car, the power went out again..." Now that's a utility vehicle.
:-)
A lot of our testing was performed at night at a number of tracks willing to provide time at night. Most of Sunrayce 99 was in the rain with some thunderstorms. Granted you're running on batteries, but you can do it.:-) In fact, I can remember from Sunrayce 99 ascending a hill at solar noon recording solar flux readings that were below that which we should have seen at 7:30pm.
Let me see, over the course of a completely sunny day during the summer you can expect to average 700W/m^2 over the eight hour period (5.6kWh/m^2). Your peak flux will be about 1kW/m^2 at solar noon, though if you're lucky cloud lensing can put that as high as 1.5kW for a short time. Anyway... So, if you run with cheap silicon you can expect 15% and if you've got the nice ones expect 25%. So, you're energy collection per square meter will be between 840Wh and 1.4kWh. If you look at a GM EV1 with the old delphi lead acid pack of 26 12V, 55Ah batteries you've got about 17kWh of capacity. So, now lets assume you've got a one square meter roof to put cells on. At the most you can recover 8% of your capacity, or about 7mi of the range of the vehicle with that pack.
BTW, make sure you get your units right before you start posting. Small thing to nitpick, but it was drilled into my head the first lecture or two of every engineering class I took.
Personally I enjoyed World Solar Challenge in Australia. The thing you can get from competitions like WSC is a good sense of how far you can push technology.
Granted, we'll never see a solar powered car driving down the road 'cause of the extremely high cost of solar cells, but at the same time how many auto manufacturers make aero performance a top priority and weight number two? There's a lot of room for the auto industry to improve aero and weight, but until Americans get over their love afair with big vehicles it just isn't happening. Besides, big vehicles ala the Expedition and Explorer are the cash cows of the industry, thus leaving little incentive to change.
The other thing people don't realize is that because something is electric doesn't mean the performance sucks. In testing at Ford, our solar car could spank the chrysler minivan that was running chase. The vehicle was so light on it's feet that it was common to spin the drive wheel (four wheel vehicle, right rear was the drive wheel) because the motor could produce so much torque.
Mazda has had a hydrogen powered vehicle in testing. It used a rotary engine to avoid the knock problems that piston engines have. Check it out at: www.monito.com/wankel/hydrogen.html
Ah, but the reason why the turbulent boundary layer is so important is that it resists seperation!
Correct me if I'm wrong, but turbulent boundary layers remove MORE energy from the flow than do laminar (thus a higher drag). However, in the case of the golf ball, having a laminar boundary layer allows the flow to seperate earlier, thus even though laminar flow is preferred in most cases, in this case it actually hurts.
You wouldn't want to dimple a car, it would probably produce too much drag over smooth panels. The auto industry needs to pay more attention to minimizing seperation off the back end of the vehicle first. Surface texturing is a small part of the pie.
I sure hope you're kidding, 'cause you're being a bit hypoctritical hiding behind an AC.
If you read the deposition, he was asked many times if he wanted to quit the deposition and stated that if he felt like he couldn't continue that he would stop the deposition.
His statments are fair game. Being sick or old doesn't absolve you of responsibility for your statements.
Silicon cells have been manufactured by the University of New South Wales to efficiencies of ~24/25%. But they cost $300 per cell and they aren't big. That's the top end of the silicon cells. There are some neat cells that are used for satellites that are made of multiple semiconductors that are optimized for certain wavelengths, are operate near 30%. Those are really expensive and are most often used in satellites.
Look into solar car racing if you're interested in performance use of solar cells. In Sunrayce 99 on a clear day (which we never saw) on an 8m^2 array you could expect a peak power of about 1kW and it would cost about $5k in raw cells.
FYI, on a very clear day you can expect ~1000W/m^2 for an array that is pointed directly at the sun at solar noon. Clouds can push that number around . I've seen at solar noon anywhere from 50W/m^2 to 1500W/m^2 due to clouds.
I was under the impression that PowerPC was a spinoff of the Power2 chip, which was 32bit. I remember having lots of fun when I had an IBM 3BT Power2 at 67MHz and a 43P with a PPC604 running at 133 to play with. Ahh... The good 'ol days of three years ago.:-) At one point they were nice machines, until the 3BT started having power supply problems. The 43P was never good for much other than looking at and using it as an X display terminal (32Mb of RAM).
Actually the pluto mission is unmanned. It is more commonly known as Pluto Kuiper Express. If you go to www.jpl.nasa.gov/ice_fire for an idea of some of the projects that may be cut.
There are some really unique problems with going to Pluto. In a nutshell: Keeping the elctronics warm enough to remain operational. Because the satellite is far from the sun it receives very little EM energy. How do you power your electronics? There has been a lot of research into this in area. Of particular interest is the Radioisotop AMTEC which was planed for PKE, Europa and the Solar Probe mission. Once you get to Pluto, how do you get all of the data back to Earth? Sure, the Deep Space Network is available, but who wants to wait seemingly forever to get the data back? Because there is a limited time fram to get to Pluto due to its orbit, how can you speed up the spacecraft? Chemical rockets are heavy and bulky compared to electric propulsion, but how are you going to power the EP?
Having taken a senior level course in Spacecraft Systems Design at the U of Michigan, it is amazing how much new technology can be aplied to problems solved long ago. There is always research going on to make something lighter/smaller/more power efficient/more capable. In the end it all results in a spacecraft that weighs less (and hence costs less to launch), can perform more research, and in the end benefits all of society.
Some interesting links: www.jpl.nasa.gov - general space exloration beyond the moon
www.engin.umich.edu/dept/aero/spacelab/ - electric propulsion research at the U of Michigan
www.ampsys.com/ - AMTEC power systems
www.engin.umich.edu/dept/aero/designcrs/index.ht ml The Winter 97 UMAero spacecraft design course atempt at Pluto Kuiper Express
Please realize that AutoCAD was available for UNIX boxes. However, if you look at Autodesk's website, AutoCAD Release 14 and later are no longer available for UNIX. There is evidence that businesses are trying to get away from doing CAD work on UNIX and trying to move to NT. I don't agree with it, but when I had to part with my SGI box at work for an NT box I was less than enthusiastic, but that is management.
Slashdot Mirror
The SR-71 is not airframe limited, but limited by the two P&W J58 powerplants.
The supersonic air has to be slowed down to subsonic speeds to burn. At a flight Mach number 3.5 the temperature rise from the succesive oblique shocks and single normal shock raise the temperature of the air to just below the flame temperature of a stoichiometric kerosene-air mixture. On top of this, the temperature of the exhaust gas is approaching the thermal limit of the turbine blades. So, you're gaining incrimentally less thrust from your fuel as well as approaching other thermal limits.
On days when the upper air temp is REALLY COLD they fly just a little faster 'cause they get more thrust and have a little more margin on the exhaust gas temp.
As a side note, supersonic combustion isn't new. Not too long ago the University of Queensland designed and tested (in their own shock tunnel) a supersonic combustion ramjet that produces more thrust than drag, which is a first. The interesting thing to see with X-43 is whether it too produces more thrust than drag.
In many cases a company may also sell the stock that it owns of itself to finance its operations. If the stock price is in the toilet, then that may no longer be a viable option in terms of short term financing.
I think the sadest part is that the article from the Boston Globe seems to suggest in the first three paragraphs that it does come from space. This completely threw me off for most of the article 'cause I was stuck on the idea of how a fungus would survive in the vacuum of space.
I wonder what the rad levels are like in the Mir?
As a practicing engineer in the aerospace business working for a private company, I'm personally and professionally insulted that you would suggest that we would not build a safe and reliable vehicle.
Aparently you lack the basic understanding of how to run a business. Yes, you have to make money. But you don't do it by killing people. If you've got four man rated spacecraft, and you loose one to an accident you face numerous problems. First, you kissed goodbye a large capital investment that can never be recovered. Second, you've brought upon yourself the hell known as the legal system, which may dog you until you're bankrupt. Third, if people believe the system is unreliable there is no way in hell they are going to fly on it, thus destroying that revenue stream. If your business is built on puting people in space, congratulations you've put yourself out of business, you're a failure and have no money. There is no incentive whatsoever to design and build an unsafe or unreliable vehicle. NONE.
The flipside is this. What if it were completely left to the government? Would it be safe? Probably. Would it be behind schedule? YES. Would it be too expensive for all but the government to be able to afford to operate it? YES. What if the gov't looses one of four vehicles to an accident? You've still lost the large capital investment. Will legal troubles dog the program? Maybe, but they won't put the gov't out of business. Will the gov't shutdown if they loose a spacecraft and crew? Nah, build another and put more people in it (baring minor modifications, that is exactly what we did after challenger). The revenue stream is not dependant on paying customers, but on people's tax dollars.
Noone forces you to smoke cigarettes. Noone forces you to drive an unsafe vehicle. Noone is going to force you to go into space. Oh, but if the gov't were left to selling cigarettes, they would be safe to smoke. Gov't cars would be high quality, safe, and affordable. Yeah. Right. Driven a Russian car lately? As bad as GM is, there are many more that are worse.
If the US gov't depended on paying customers to fly the space shuttle, they would have suspended operations back in the early 80's.
BTW, please tell me. What incentive does the government have in building a safe, reliable and affordable launch vehicle?
Space travel is inherently dangerous and you will always be worrying about safety. What does government have to loose if seven astronauts die because of a stupid decission to launch despite the objections of the engineers of the manufacturer of the solid boosters? After the chanllenger accident, did the gov't go out of business, have civil or criminal charges filed against it?
Private companies have a financial stake in providing safe and affordable access to space. The private company faces financial ruin and potentiall civil and criminal lawsuits if the screw up. If I were a private company, I'd be damn sure the vehicle was reliable and safe.
Actually, what would be kind of cool is if you could use your hybrid car to serve as a backup generator for your house. It could bring new meaning to Sport Utility Vehicles.
"Honey pull up the hybrid sports car, the power went out again..." Now that's a utility vehicle.
:-)
A lot of our testing was performed at night at a number of tracks willing to provide time at night. Most of Sunrayce 99 was in the rain with some thunderstorms. Granted you're running on batteries, but you can do it. :-) In fact, I can remember from Sunrayce 99 ascending a hill at solar noon recording solar flux readings that were below that which we should have seen at 7:30pm.
Let me see, over the course of a completely sunny day during the summer you can expect to average 700W/m^2 over the eight hour period (5.6kWh/m^2). Your peak flux will be about 1kW/m^2 at solar noon, though if you're lucky cloud lensing can put that as high as 1.5kW for a short time. Anyway... So, if you run with cheap silicon you can expect 15% and if you've got the nice ones expect 25%. So, you're energy collection per square meter will be between 840Wh and 1.4kWh. If you look at a GM EV1 with the old delphi lead acid pack of 26 12V, 55Ah batteries you've got about 17kWh of capacity. So, now lets assume you've got a one square meter roof to put cells on. At the most you can recover 8% of your capacity, or about 7mi of the range of the vehicle with that pack.
BTW, make sure you get your units right before you start posting. Small thing to nitpick, but it was drilled into my head the first lecture or two of every engineering class I took.
Personally I enjoyed World Solar Challenge in Australia. The thing you can get from competitions like WSC is a good sense of how far you can push technology.
Granted, we'll never see a solar powered car driving down the road 'cause of the extremely high cost of solar cells, but at the same time how many auto manufacturers make aero performance a top priority and weight number two? There's a lot of room for the auto industry to improve aero and weight, but until Americans get over their love afair with big vehicles it just isn't happening. Besides, big vehicles ala the Expedition and Explorer are the cash cows of the industry, thus leaving little incentive to change.
The other thing people don't realize is that because something is electric doesn't mean the performance sucks. In testing at Ford, our solar car could spank the chrysler minivan that was running chase. The vehicle was so light on it's feet that it was common to spin the drive wheel (four wheel vehicle, right rear was the drive wheel) because the motor could produce so much torque.
Ahh... The good old days of college life.
Mazda has had a hydrogen powered vehicle in testing. It used a rotary engine to avoid the knock problems that piston engines have. Check it out at: www.monito.com/wankel/hydrogen.html
Ah, but the reason why the turbulent boundary layer is so important is that it resists seperation!
Correct me if I'm wrong, but turbulent boundary layers remove MORE energy from the flow than do laminar (thus a higher drag). However, in the case of the golf ball, having a laminar boundary layer allows the flow to seperate earlier, thus even though laminar flow is preferred in most cases, in this case it actually hurts.
You wouldn't want to dimple a car, it would probably produce too much drag over smooth panels. The auto industry needs to pay more attention to minimizing seperation off the back end of the vehicle first. Surface texturing is a small part of the pie.
I sure hope you're kidding, 'cause you're being a bit hypoctritical hiding behind an AC.
If you read the deposition, he was asked many times if he wanted to quit the deposition and stated that if he felt like he couldn't continue that he would stop the deposition.
His statments are fair game. Being sick or old doesn't absolve you of responsibility for your statements.
Silicon cells have been manufactured by the University of New South Wales to efficiencies of ~24/25%. But they cost $300 per cell and they aren't big. That's the top end of the silicon cells. There are some neat cells that are used for satellites that are made of multiple semiconductors that are optimized for certain wavelengths, are operate near 30%. Those are really expensive and are most often used in satellites.
Look into solar car racing if you're interested in performance use of solar cells. In Sunrayce 99 on a clear day (which we never saw) on an 8m^2 array you could expect a peak power of about 1kW and it would cost about $5k in raw cells.
FYI, on a very clear day you can expect ~1000W/m^2 for an array that is pointed directly at the sun at solar noon. Clouds can push that number around . I've seen at solar noon anywhere from 50W/m^2 to 1500W/m^2 due to clouds.
One question: did you read the article?
Learn to read, then ask questions.
Russ
I was under the impression that PowerPC was a spinoff of the Power2 chip, which was 32bit. I remember having lots of fun when I had an IBM 3BT Power2 at 67MHz and a 43P with a PPC604 running at 133 to play with. Ahh... The good 'ol days of three years ago. :-) At one point they were nice machines, until the 3BT started having power supply problems. The 43P was never good for much other than looking at and using it as an X display terminal (32Mb of RAM).
Russ
Actually the pluto mission is unmanned. It is more commonly known as Pluto Kuiper Express. If you go to www.jpl.nasa.gov/ice_fire for an idea of some of the projects that may be cut.
t ml
There are some really unique problems with going to Pluto. In a nutshell: Keeping the elctronics
warm enough to remain operational. Because the satellite is far from the sun it receives very little EM energy. How do you power your electronics? There has been a lot of research into this in area. Of particular interest is the Radioisotop AMTEC which was planed for PKE, Europa
and the Solar Probe mission. Once you get to Pluto, how do you get all of the data back to Earth? Sure, the Deep Space Network is available, but who wants to wait seemingly forever to get the data back? Because there is a limited time fram to get to Pluto due to its orbit, how can you speed up the spacecraft? Chemical rockets are heavy and bulky compared to electric propulsion, but how are you going to power the EP?
Having taken a senior level course in Spacecraft Systems Design at the U of Michigan, it is amazing how much new technology can be aplied to problems solved long ago. There is always research going on to make something lighter/smaller/more power efficient/more capable. In the end it all results in a spacecraft that weighs less (and hence costs less to launch), can perform more research, and in the end benefits all of society.
Some interesting links:
www.jpl.nasa.gov - general space exloration beyond
the moon
www.engin.umich.edu/dept/aero/spacelab/ - electric propulsion research at the U of Michigan
www.ampsys.com/ - AMTEC power systems
www.engin.umich.edu/dept/aero/designcrs/index.h
The Winter 97 UMAero spacecraft design course atempt at Pluto Kuiper Express
Russ Moerland
Please realize that AutoCAD was available for UNIX boxes. However, if you look at Autodesk's website, AutoCAD Release 14 and later are no longer available for UNIX. There is evidence that businesses are trying to get away from doing CAD work on UNIX and trying to move to NT. I don't agree with it, but when I had to part with my SGI box at work for an NT box I was less than enthusiastic, but that is management.