coondoggie writes "On its current space scouting mission, NASA's Lunar Reconnaissance Orbiter (LRO) is using a pumped up communications device to deliver 461 gigabytes of data and images per day, at a rate of up to 100 Mbps.
As the first high data rate K-band transmitter to fly on a NASA spacecraft, the 13-inch-long tube, called a Traveling Wave Tube Amplifier, is making it possible for NASA scientists to receive massive amounts of images and data about the moon's surface and environment.
The amplifier was built by L-3 Communications Electron Technologies in conjunction with NASA's Glenn Research Center. The device uses electrodes in a vacuum tube to amplify microwave signals to high power. It's ideal for sending large amounts of data over a long distance because it provides more power and more efficiency than its alternative, the transistor amplifier, NASA stated." It kills me that the moon has better bandwidth than my house.
Did anyone notice that it's all based on vacuum tubes?
My question is why you need a vacuum tube in a vacuum? Just put the parts out in open space, save a bit of weight, no problem with the tube getting deposits on it over time, or thermal expansion and contraction stressing the tube, etc.
Also, I'm almost sure he could get a 100 Mbps link to his house if he was willing to pay what NASA is paying for theirs. At least I don't think it would be much more expensive.
by Anonymous Coward
on Thursday August 20, @09:29AM (#29132749)
Vacuum tubes have always had higher frequency limits than transistors, since WWII in fact. Take a look at THz radiation sources, all tubes. No tranny is going to touch that for a while. And then tubes will have gotten better too. http://en.wikipedia.org/wiki/Backward_wave_oscillator Tubes just have more geometric freedoms to create bizarre fields and strange structures to do whatever you need.
Traveling Wave Tubes have been a mainstay of microwave communications and radar systems for the better part of a century. They're a very efficient way of amplifying microwave signals to the very high power levels needed to cross long distances.
The article admits that the Traveling Wave Tubes are not new, but it also lists several points that make this implementation better and very much noteworthy compared to its predecessors. You seem to have an interest in/knowledge of these communication devices, so I would say that the article is actually a worthwhile read for you.
the point is that before you read it, did you know there was a TWT orbiting the moon withh 100Mbps bandwidth transferring over 400GB of data a day? if not, then you learned something new.
And these have been used in space applications since the early 60's. In fact every satellite program that I have worked on used TWTA amplifiers. People are always looking for alternatives because they are very squirrely devices, but it's pretty difficult to generate much power at microwave frequencies with solid-state alternatives.
Yes. But it's not easy. A TWT is, in many ways, very similar to a linear acclerator, except that instead of using RF to put energy into an electron beam to make it faster, it takes energy out of a fast electron beam to amplify an RF signal. So whip out those books on linear accelerator design and construction, and have at it. You need an electron gun and some electron optics to make the beam, and then the section where the RF interacts with the beam, either a helix or a series of coupled resonant cavitie
Exactly. Why the hell does the summary go into depth on TWT's? They've been around since WWII, and have been extensively forever.
Cause Joe Sixpack never heard of them? And with the possibility of NASA losing some more budget [newscientist.com], it's best to keep talking up all that cool tech that's been around since the Stone Age, makes people think you just found something cool.
They are using a radar set as a data link. I'm wondering whether they are still using it as a radar to map the moon too, by using a different set of antennas.
When you need to make serious power, tubes are still the way to go. Transistors have a significant reliability benefit.
Also, for 99% of applications, transistors are better. For the other 1%, you have very application-specific tube designs such as TWTs and magnetrons, which rearrange the tubes in such a manner as to negate its usual disadvantage (large size USUALLY translates to nasty frequency limits - TWTs and magnetrons are exceptions that use various Neat Tricks to allow microwave operation from a large device.)
BTW, one of the other common microwave tubes (magnetrons), while it is a "niche" device, it is a VERY widely deployed niche - basically all microwave ovens use magnetron tubes.
I think he was referring to the "vacuum" of space. Why not just take the glass off the outside and save some weight?
Because the tube would get contaminated by the pollutants & particles in the atmosphere, and some of that won't outgas as the probe gets into a decent vacuum. Also, the solar wind [wikipedia.org] kicks particles out as well, and some of those could also contaminate the tube, threatening its lifespan and/or performance.
curious thing about tubes, they don't become useful until they're sealed in vacuum, and boiled out in a high RF magnetic field to take impurities off the elements. and then you have to flash the last of the gases off by igniting a getter inside the envelope.
that provides a higher vacuum on earth, inside the tube, than you can ever develop in space. and the electrons can do their work, instead of hitting stuff and just making a useless glow.
You just KNOW that the original name for the device was "Traveling Wave Amplified Tube" until some NASA jackass noticed the acronym and ruined it for everyone.
That much data and Comcast would throttle it no matter what the scientists said. If AT&T had it going through their "unlimited" 3G connection, NASA would be hosed and we would be increasing the national debt by trillions.
One last thing, I m wondering if the **AA doesn't want access to the data stream to make sure it isn't a bittorrent containing their precious copyrighted work. After all, we all know there is no legitimate use for that much bandwidth.
TWT amps have been used in microwave systems since the 2nd world war. The use of TWT in satellites are recent, as in 25-30 years ago. The NSA's LACROSSE and the new ONYX satellites use TWT amps in the finals on their radar systems. The Soviet ROARSAT's probably use them as well, or something similar, they love to overbuild their stuff.
Hell, the YF-12a used 2 TWT's in tandem in its Hughes AN/ASG-18 radar, putting out over 10MW of raw power.
But they are power gobblers, The YF-12A's ate over 40KVA of juice to operate.
It kills me that the moon has better bandwidth than my house.
I know that Taco's trying to be funny here, but, seriously, the moon should most certainly have better bandwidth. That is to say, a research project that is able to afford a custom solution to a highly specialized problem with plenty of money to throw at had damned well better have better performance than what is available to commodity markets. I expect this to be true just as nearly every other bit of the hardware they send up will be better, faster, stronger, lighter, and more able to withstand ionizing radiation than the equivalent, when available, from K-Mart. There's a good reason these projects cost hundreds of millions of dollars for a probe to be sent somewhere. The Mars rovers, as another example, are using a 256 kbps channel -- deployed five years ago when DSL was still considered fast -- over a distance that ranges 55 to 400 million miles. Now *that's* performance.
It actually rather amazes me that Taco's or anyone else's house has close to the bandwidth available from the moon.
..and there's always the advantage of having data with a warmer, richer feel to it than using a solid-state amp. Just think how much better the data will be once they start storing it on vinyl!
In fact the limited factor is recording speed and capacity. The large atom-smashers run the receptor data through a preliminary A.I. discrmination programs which save the small fraction deemed interesting. Then slaving grad students will spend years on tiny pieces extacting the significant discoveries.
Some of the large ground telescopes are partnering with Google and MicroSoft to put large portions of their data online. The computer programs and main scientists only have enough time to give a cursory glance at it. Maybe it will be a kid in a junior high school science lab that looks at something more closely and makes a discovery. Some of this is occuring with google earth imagery now.
but for high power, squirrelly conditions, and reliability under real world conditions, tubes are still the go-to player in a lot of situations. a solar storm will roach semiconductor outputs, but it takes a monster pulse straight down the gullet to take a tube out.
You know what's ironic? I HAVE played WoW with over a second of lag. Fuck, sometimes WoW servers were having up to fucking three seconds lag. It's rare, but it always happens at the worst possible moment, often during a boss fight.
If I was stuck on the moon with absolutely nothing to do, I wouldn't complain about 1 second of lag if WoW was my only source of daily fun.
The best available at my house is 512Kbs DSL. I offered to lay the fiber myself for the final 2 1/2 miles or so, or pay them to do it, but they insist that there are legal reasons they can't serve me.
So, in typical geek fashion, I set up a P2P wifi link for that distance. It works, and I get about 50 Mbs on a good day. I get terrible packet loss when it rains hard, though.
Insane (Score:5, Funny)
Their Cingular bill is going to suck.
Re:Insane (Score:4, Funny)
Parent
Re:Insane (Score:5, Insightful)
My question is why you need a vacuum tube in a vacuum? Just put the parts out in open space, save a bit of weight, no problem with the tube getting deposits on it over time, or thermal expansion and contraction stressing the tube, etc.
Parent
Re: (Score:3, Funny)
Re:Insane (Score:5, Funny)
That was my slogan for a while, too. Pity my liver couldn't take the strain.
Parent
Re: (Score:3, Informative)
no, they couldnt risk having a Verizon tech punching the oribter in the face if they needed onsite service
Re:Insane (Score:5, Informative)
5.46MB/s is close to half of a 100BaseT.
Parent
Sure, it can blast huge amounts of data (Score:5, Funny)
Re:Sure, it can blast huge amounts of data (Score:5, Funny)
Sure it can, after all it's got a 13 inch "tube".
Parent
Don't feel bad, CmdrTaco (Score:5, Funny)
Re:Don't feel bad, CmdrTaco (Score:5, Insightful)
Parent
Re:Don't feel bad, CmdrTaco (Score:4, Funny)
At the very least, he could buy a new house near somewhere that has 100mbps connections.
Parent
Bandwidth, sure, but the Ping? (Score:3, Funny)
It may have better BW than your house, but the ping is going to suck.
Or would you like your internet connection to be served by a SUV carrying hard drives?
Re:Bandwidth, sure, but the Ping? (Score:5, Insightful)
Or would you like your internet connection to be served by a SUV carrying hard drives?
Never underestimate the bandwidth of a fedex truck packed with 250 lbs of hard disks!
Depending on the file size of what you would be downloading and with what technology, overnight shipping might STILL be better latency too!
Parent
Re: (Score:3, Funny)
Or would you like your internet connection to be served by a SUV carrying hard drives?
Never underestimate the bandwidth of a fedex truck packed with 250 lbs of hard disks!
Depending on the file size of what you would be downloading and with what technology, overnight shipping might STILL be better latency too!
Right, but remember that full hard drives weigh more than empty ones, so you only want to buy about 200 lb of empty drives if you have a 250 lb limit.
better bandwidth? (Score:3, Informative)
1 - http://www.vendian.org/envelope/dir0/light_delay.html [vendian.org]
Re:better bandwidth? (Score:4, Informative)
Parent
Spam (Score:3, Funny)
Re:Spam (Score:4, Informative)
Vacuum tubes have always had higher frequency limits than transistors, since WWII in fact. Take a look at THz radiation sources, all tubes. No tranny is going to touch that for a while. And then tubes will have gotten better too.
http://en.wikipedia.org/wiki/Backward_wave_oscillator
Tubes just have more geometric freedoms to create bizarre fields and strange structures to do whatever you need.
Parent
Re:Spam (Score:5, Funny)
Parent
So wait... (Score:3, Funny)
This is not exactly a new device... (Score:5, Informative)
Traveling Wave Tubes have been a mainstay of microwave communications and radar systems for the better part of a century. They're a very efficient way of amplifying microwave signals to the very high power levels needed to cross long distances.
Re:This is not exactly a new device... (Score:5, Interesting)
Parent
Re:This is not exactly a new device... (Score:5, Funny)
Parent
Re:This is not exactly a new device... (Score:5, Insightful)
the point is that before you read it, did you know there was a TWT orbiting the moon withh 100Mbps bandwidth transferring over 400GB of data a day? if not, then you learned something new.
Parent
Re: (Score:3, Informative)
And these have been used in space applications since the early 60's. In fact every satellite program that I have worked on used TWTA amplifiers. People are always looking for alternatives because they are very squirrely devices, but it's pretty difficult to generate much power at microwave frequencies with solid-state alternatives.
Brett
Re: (Score:3, Informative)
Yes. But it's not easy. A TWT is, in many ways, very similar to a linear acclerator, except that instead of using RF to put energy into an electron beam to make it faster, it takes energy out of a fast electron beam to amplify an RF signal. So whip out those books on linear accelerator design and construction, and have at it. You need an electron gun and some electron optics to make the beam, and then the section where the RF interacts with the beam, either a helix or a series of coupled resonant cavitie
Re:This is not exactly a new device... (Score:5, Informative)
You need an electron gun and some electron optics to make the beam,
Check, old 19" TV tube... all the parts are there.
and then the section where the RF interacts with the beam, either a helix or a series of coupled resonant cavities.
Again, can be found in other surplus tech.
but screw it, just buy one....
http://cgi.ebay.com/NEC-LD7306A-B61-Travelling-Wave-Tube-TWT_W0QQitemZ200255211587QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2ea0240843&_trksid=p3286.c0.m14 [ebay.com]
Parent
Re:This is not exactly a new device... (Score:4, Informative)
Cause Joe Sixpack never heard of them? And with the possibility of NASA losing some more budget [newscientist.com], it's best to keep talking up all that cool tech that's been around since the Stone Age, makes people think you just found something cool.
Parent
Yeah, but the latency's a bitch (Score:3, Funny)
Radar (Score:4, Interesting)
Vacuum Tube? (Score:5, Funny)
Anybody else think it's funny that in this case, a vacuum tube is a step up from a transistor?
Re:Vacuum Tube? (Score:4, Informative)
Parent
Re:Vacuum Tube? (Score:5, Informative)
When you need to make serious power, tubes are still the way to go. Transistors have a significant reliability benefit.
Also, for 99% of applications, transistors are better. For the other 1%, you have very application-specific tube designs such as TWTs and magnetrons, which rearrange the tubes in such a manner as to negate its usual disadvantage (large size USUALLY translates to nasty frequency limits - TWTs and magnetrons are exceptions that use various Neat Tricks to allow microwave operation from a large device.)
BTW, one of the other common microwave tubes (magnetrons), while it is a "niche" device, it is a VERY widely deployed niche - basically all microwave ovens use magnetron tubes.
Parent
Re: (Score:3, Insightful)
no because they always have kicked the arse of a transistor.
Show me a 10,000 watt transistor.. Oh wait, you haveto use a Tube for that kind of power....
Tubes have kicked the Transistors butt forever when you need high power comms.
Re:Vacuum Tube? (Score:4, Informative)
Because the tube would get contaminated by the pollutants & particles in the atmosphere, and some of that won't outgas as the probe gets into a decent vacuum. Also, the solar wind [wikipedia.org] kicks particles out as well, and some of those could also contaminate the tube, threatening its lifespan and/or performance.
Good idea, but it just won't work in practice.
Parent
Vacuum (Score:5, Interesting)
Did they even bother to seal the tube, or are they using the vacuum of space?
if not, the tube would be ruined before launch (Score:5, Informative)
curious thing about tubes, they don't become useful until they're sealed in vacuum, and boiled out in a high RF magnetic field to take impurities off the elements. and then you have to flash the last of the gases off by igniting a getter inside the envelope.
that provides a higher vacuum on earth, inside the tube, than you can ever develop in space. and the electrons can do their work, instead of hitting stuff and just making a useless glow.
Parent
Re: (Score:3, Insightful)
Traveling Wave Tube Amplifier? (Score:5, Funny)
I hope Nasa has the right ISP (Score:5, Funny)
That much data and Comcast would throttle it no matter what the scientists said. If AT&T had it going through their "unlimited" 3G connection, NASA would be hosed and we would be increasing the national debt by trillions.
One last thing, I m wondering if the **AA doesn't want access to the data stream to make sure it isn't a bittorrent containing their precious copyrighted work. After all, we all know there is no legitimate use for that much bandwidth.
Slow news day from what it sounds like... (Score:4, Informative)
TWT amps have been used in microwave systems since the 2nd world war. The use of TWT in satellites are recent, as in 25-30 years ago. The NSA's LACROSSE and the new ONYX satellites use TWT amps in the finals on their radar systems. The Soviet ROARSAT's probably use them as well, or something similar, they love to overbuild their stuff.
Hell, the YF-12a used 2 TWT's in tandem in its Hughes AN/ASG-18 radar, putting out over 10MW of raw power.
But they are power gobblers, The YF-12A's ate over 40KVA of juice to operate.
Of course the moon will have better bandwidth (Score:4, Insightful)
CmdTaco comments in the original posting:
It kills me that the moon has better bandwidth than my house.
I know that Taco's trying to be funny here, but, seriously, the moon should most certainly have better bandwidth. That is to say, a research project that is able to afford a custom solution to a highly specialized problem with plenty of money to throw at had damned well better have better performance than what is available to commodity markets. I expect this to be true just as nearly every other bit of the hardware they send up will be better, faster, stronger, lighter, and more able to withstand ionizing radiation than the equivalent, when available, from K-Mart. There's a good reason these projects cost hundreds of millions of dollars for a probe to be sent somewhere. The Mars rovers, as another example, are using a 256 kbps channel -- deployed five years ago when DSL was still considered fast -- over a distance that ranges 55 to 400 million miles. Now *that's* performance.
It actually rather amazes me that Taco's or anyone else's house has close to the bandwidth available from the moon.
Tone (Score:3, Funny)
Traveling Wave Tube Amplifier
..and there's always the advantage of having data with a warmer, richer feel to it than using a solid-state amp. Just think how much better the data will be once they start storing it on vinyl!
terabytes for Hadron Collider and large telescopes (Score:3, Interesting)
Some of the large ground telescopes are partnering with Google and MicroSoft to put large portions of their data online. The computer programs and main scientists only have enough time to give a cursory glance at it. Maybe it will be a kid in a junior high school science lab that looks at something more closely and makes a discovery. Some of this is occuring with google earth imagery now.
the TWT is a 50-year-old technology (Score:3, Insightful)
but for high power, squirrelly conditions, and reliability under real world conditions, tubes are still the go-to player in a lot of situations. a solar storm will roach semiconductor outputs, but it takes a monster pulse straight down the gullet to take a tube out.
Re:Don't try this in Space (Score:5, Funny)
Tomorrow's headline: "RIAA Lobbies Congress to Shut Down NASA"
Parent
Re:Don't try this in Space (Score:5, Funny)
Parent
Re: (Score:3, Insightful)
Try playing WoW with over a second of lag.
You know what's ironic?
I HAVE played WoW with over a second of lag.
Fuck, sometimes WoW servers were having up to fucking three seconds lag. It's rare, but it always happens at the worst possible moment, often during a boss fight.
If I was stuck on the moon with absolutely nothing to do, I wouldn't complain about 1 second of lag if WoW was my only source of daily fun.
Re:The moon vs. your house (Score:4, Interesting)
The best available at my house is 512Kbs DSL. I offered to lay the fiber myself for the final 2 1/2 miles or so, or pay them to do it, but they insist that there are legal reasons they can't serve me.
So, in typical geek fashion, I set up a P2P wifi link for that distance. It works, and I get about 50 Mbs on a good day. I get terrible packet loss when it rains hard, though.
Parent