Airspan Networks Inc. of Boca Raton, Florida has recently announced a device family called MiMax(TM) which addresses both of these problems. They now have USB 2.0 WiMax adapters for laptops, etc, which can operate on unlicensed as well as licensed bands.
Quoting from article:
"The MiMAX USB is a ground-breaking product that will enable end-users to connect to virtually every Mobile WiMAX network that is deployed worldwide, and supports all of the target Wave 2 MIMO Mobile WiMAX certification profiles (2.3 GHz, 2.5 GHz, 3.3 - 3.8 GHz, and 4.9 - 5.8 GHz). This capability enables service providers to offer roaming services across multiple WiMAX networks regardless of the frequency band used.
This incredibly slim device measuring just 98mm x 36mm x 8mm -- around 28cc, is one of the world's first WiMAX USB devices. The device is light and easy to carry, making it an ideal companion for the laptop-carrying traveller. The device is powered, via the USB port by the host computer. Its low power consumption and support for Mobile WiMAX idle and sleep modes means that while battery life is conserved, the MiMAX USB still delivers +22dBm at 2.3, 2.5 and 3.5 GHz and +17dBm at 5 GHz."
I don't specialize in fluid or thermodynamics but this is my opinion, and any support/rebuttal is welcome!
A quick check on re-entry temperature variation on this site: http://www.columbiassacrifice.com/$D_temperature.h tm shows the area around the hole endures about 10 minutes of 1500 deg F heat, and Google tells me aluminum melts at 1220 deg F. On the surface (pun intended), this would seem cause for concern.
If NASA engineers feel these tiles can re-enter without repair, their reasons could be:
1) This area of the shuttle does not have to contend with the extreme heat that is experienced at the nose or other leading edge surfaces so the "hot air" isn't hot enough to melt the aluminum in the belly, and 2) The hole must be small enough that hot air flow may "skip" over it on re-entry. If the hot air can indeed passes right over it, then the danger to the aluminum inside is probably not very great.
If the engineers ran a "simplified" mathematical simulation assuming the hole was just the "average" well-formed hole, the above rationale would make sense.
I think the more important concern to focus on (which I'm sure NASA must have considered), is that this hole is very asymmetric. The photos provide terrific evidence. One side the gash slopes gently into the "hole" (I presume where the depth sensor reads 1.2 inches, since the tiles are only 1 inch thick), and on the other side, you have a quarter ping-pong ball cut-out as well as a 90-degree lip of half-tile above the hole. In this instance, I think the direction of travel of these tiles on re-entry matters a great deal... I think the first scenario below may be most cause for concern.
1) If the "up" orientation of the tile lettering is the shuttle's forward direction, I would imagine the hot air flow will not be turbulent upon entering the gash, and will actually follow the gentle slope downwards towards and into the hole, melting what is inside. What hot air doesn't make it into the hole will smack into the 90-degree lip and the quarter ping-pong ball cut-out, causing excess heat at those edges and/or loosening that tile from its backing, causing it to fall off (though not too likely since that lip represents only a small portion of that tile, and it is buttressed by the other tiles "behind" it).
2) On the other hand, if the forward direction was reversed, the hot air flow would become turbulent upon meeting the quarter ping-pong ball cut-out. If the dimensions of that cut-out are sufficiently disruptive, the turbulent hot air could "lick" the hole, melting whatever is inside, what doesn't go into the hole will glide off the sloped ceramic gouge on the other side. With the turbulent air, there will be a negative air pressure around that tile, but the force shouldn't be enough to rip the tile from its backing.
If the shuttle direction is that of option #1, let's hope that hole is small enough that as litte hot air gets in as possible.
My point is this: A hole is not just a hole unless it looks the same from all sides...
Slashdot Mirror
Airspan Networks Inc. of Boca Raton, Florida has recently announced a device family called MiMax(TM) which addresses both of these problems. They now have USB 2.0 WiMax adapters for laptops, etc, which can operate on unlicensed as well as licensed bands.
Please see today's article in CNN Money:
http://money.cnn.com/news/newsfeeds/articles/marketwire/0307789.htm
Quoting from article: "The MiMAX USB is a ground-breaking product that will enable end-users to connect to virtually every Mobile WiMAX network that is deployed worldwide, and supports all of the target Wave 2 MIMO Mobile WiMAX certification profiles (2.3 GHz, 2.5 GHz, 3.3 - 3.8 GHz, and 4.9 - 5.8 GHz). This capability enables service providers to offer roaming services across multiple WiMAX networks regardless of the frequency band used. This incredibly slim device measuring just 98mm x 36mm x 8mm -- around 28cc, is one of the world's first WiMAX USB devices. The device is light and easy to carry, making it an ideal companion for the laptop-carrying traveller. The device is powered, via the USB port by the host computer. Its low power consumption and support for Mobile WiMAX idle and sleep modes means that while battery life is conserved, the MiMAX USB still delivers +22dBm at 2.3, 2.5 and 3.5 GHz and +17dBm at 5 GHz."
I don't specialize in fluid or thermodynamics but this is my opinion, and any support/rebuttal is welcome!
h tm shows the area around the hole endures about 10 minutes of 1500 deg F heat, and Google tells me aluminum melts at 1220 deg F. On the surface (pun intended), this would seem cause for concern.
A quick check on re-entry temperature variation on this site: http://www.columbiassacrifice.com/$D_temperature.
If NASA engineers feel these tiles can re-enter without repair, their reasons could be:
1) This area of the shuttle does not have to contend with the extreme heat that is experienced at the nose or other leading edge surfaces so the "hot air" isn't hot enough to melt the aluminum in the belly, and
2) The hole must be small enough that hot air flow may "skip" over it on re-entry. If the hot air can indeed passes right over it, then the danger to the aluminum inside is probably not very great.
If the engineers ran a "simplified" mathematical simulation assuming the hole was just the "average" well-formed hole, the above rationale would make sense.
I think the more important concern to focus on (which I'm sure NASA must have considered), is that this hole is very asymmetric. The photos provide terrific evidence. One side the gash slopes gently into the "hole" (I presume where the depth sensor reads 1.2 inches, since the tiles are only 1 inch thick), and on the other side, you have a quarter ping-pong ball cut-out as well as a 90-degree lip of half-tile above the hole. In this instance, I think the direction of travel of these tiles on re-entry matters a great deal... I think the first scenario below may be most cause for concern.
1) If the "up" orientation of the tile lettering is the shuttle's forward direction, I would imagine the hot air flow will not be turbulent upon entering the gash, and will actually follow the gentle slope downwards towards and into the hole, melting what is inside. What hot air doesn't make it into the hole will smack into the 90-degree lip and the quarter ping-pong ball cut-out, causing excess heat at those edges and/or loosening that tile from its backing, causing it to fall off (though not too likely since that lip represents only a small portion of that tile, and it is buttressed by the other tiles "behind" it).
2) On the other hand, if the forward direction was reversed, the hot air flow would become turbulent upon meeting the quarter ping-pong ball cut-out. If the dimensions of that cut-out are sufficiently disruptive, the turbulent hot air could "lick" the hole, melting whatever is inside, what doesn't go into the hole will glide off the sloped ceramic gouge on the other side. With the turbulent air, there will be a negative air pressure around that tile, but the force shouldn't be enough to rip the tile from its backing.
If the shuttle direction is that of option #1, let's hope that hole is small enough that as litte hot air gets in as possible.
My point is this: A hole is not just a hole unless it looks the same from all sides...