Traveling Wave Tube Competitors Unite Behind Standardization Push
VELIZY, France — The two principal manufacturers of Ka-band traveling wave tubes (TWTs) have called on satellite prime contractors to standardize their interfaces to permit the two companies to increase production rates of a component that is causing bottlenecks in satellite deliveries.
The two companies — Thales Electron Devices, which is based here and in Ulm, Germany; and L3 Communications Electron Technologies of Torrance, Calif. — have a virtual duopoly on TWT production, a situation that is unlikely to change soon as the costs and risks of TWT manufacturing are daunting.
Both manufacturers are under pressure to increase production rates as satellite operators the world over adopt broadband to deliver consumer and business Internet, direct-to-home television and mobile links to aeronautical and maritime platforms.
Market forecasts are unanimous in saying that demand for high-throughput satellite capacity is more than a temporary trend and likely will result in broadband capacity quadrupling, if not more, within a decade when measured in gigabits per second of throughput.
Much of this capacity will be in Ka-band, which Thales and L3 say poses special challenges for TWT manufacturing.
The two companies already are struggling to keep up with demand. They also are struggling to divvy up capacity so as not to have their production lines locked into one or another satellite program.
Jean-Francois Auboin, director of space programs and engineering at Thales Electron Devices, said that just a couple of years ago Ka-band TWT demand was less than 20 percent of his company’s TWT business. In 2012, he said, Ka-band is likely to equal Ku-band demand, with each accounting for a bit more than 40 percent of the total.
The remaining demand will be for TWTs in C-, X- and L-band.
“Demand for Ka-band TWTs is increasing, and the demand is for higher-power as well,” Auboin said. “By the end of the year we expect to have qualified a 170-watt tube.”
For broadband satellite systems, he said, “the TWTs have been the limiting factor in the size of the satellite, in part because of all the heat that these high-power tubes need to dissipate.”
Auboin and Michel Cazaux, Thales Electron Devices’ head of marketing for microwave and imaging subsystems, said their company has been investing in increased capacity, but that Ka-band TWTs still require months to build, with much of the work done in painstaking, hand-made fashion.
This is the nature of the work, they said, and it is not likely to change.
Jerry Ozovek, president of L3 Communications Electron Technologies, agreed.
“We are struggling to keep up with demand today and unfortunately you cannot just flip a switch and have increased capacity,” Ozovek said. “It takes a tremendous amount of investment from a dollar standpoint, and it takes many months to put the infrastructure in place and increase the throughput — in an environment of extreme uncertainty.”
From the L3 and Thales perspective, satellite operators and prime contractors are asking them to make a high-cost, long-term investment to serve a market whose long-term stability is far from assured.
Even more problematic, both companies said, is the fact that Ka-band TWT production is often program-specific, meaning TWTs built for, say, satellite prime contractor(SS/L) and its 1300 satellite platform cannot be transferred to an Astrium Satellites spacecraft if the SS/L program is delayed.
“You’re talking about what could be an infinite number of configuration combinations and permutations, all driven by the satellite platform designers,” Ozovek said. “The ability to get ahead of the curve, to build ahead — well, you don’t really know what to build because you don’t know what programs may go. And even if you did, you don’t know who [among the satellite builders] is going to win. The winners choose what configuration they want based on their own engineering approach, and that flows down to us.”
Auboin said the vacuum part of the TWT is standardized, but that the base plate for it varies considerably depending on which satellite manufacturer is placing the order. In part this is due to differences in where each satellite manufacturer places its heat pipes. The result is that a satellite program being competed by Boeing andwill need different TWTs depending on which company wins the contract.
“It would be great to exchange tubes from one to another satellite, and from one to another manufacturer,” Auboin said. This would allow the TWT builders to mix and match production to satisfy demands for programs that are accelerated, and those that are slowed down.
“There is no special reason for these differences” among satellite prime contractors, Auboin said. “They use these configurations because they have always done it that way, that’s all.”
Auboin said satellite prime contractors appear to understand the problem and are starting to make headway in standardizing subsystems. “It is changing,” he said. “But it is changing very, very slowly.”
Thales and L3 say it typically takes about a year to produce a Ka-band TWT. The cycles needed to hand-attach some of the 1,000 parts that go into a single tube, to “burn in” the tube, to verify its performance in thermal vacuum chambers — none of these things can be easily accelerated or automated, Auboin and Ozovek said.
And at the end of the process, a sizable percentage of the finished TWTs must be discarded because they have small defects. The two companies said they are reducing defects, which will help production, as they have done with TWTs for Ku-, C-band and other frequencies.
But the amount of handcrafting, they said, is unique to Ka-band and cannot be compressed or turned over to robots.
One positive element of it, the two companies said, is that Ka-band TWT production, because of its specialized nature, cannot easily be outsourced to India or China.