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Voyager 1 Fires Up Thrusters After 37 Years (nasa.gov)
If you tried to start a car that's been sitting in a garage for decades, you might not expect the engine to respond. But a set of thrusters aboard the Voyager 1 spacecraft successfully fired up Wednesday after 37 years without use. NASA announces: Voyager 1, NASA's farthest and fastest spacecraft, is the only human-made object in interstellar space, the environment between the stars. The spacecraft, which has been flying for 40 years, relies on small devices called thrusters to orient itself so it can communicate with Earth. These thrusters fire in tiny pulses, or "puffs," lasting mere milliseconds, to subtly rotate the spacecraft so that its antenna points at our planet. Now, the Voyager team is able to use a set of four backup thrusters, dormant since 1980. "With these thrusters that are still functional after 37 years without use, we will be able to extend the life of the Voyager 1 spacecraft by two to three years," said Suzanne Dodd, project manager for Voyager at NASA's Jet Propulsion Laboratory, Pasadena, California.
It's not even in our solar system any longer, having traversed the heliosphere of the solar wind into true interstellar space. Power from the nuclear thermal generator runs out in about 2020.
Bruce Perens.
FYI, you can see what each antenna in NASA's Deep Space Network is doing at any given moment by Looking at this site..
Below each antenna is the craft being communicated to. Clicking on the antenna and then "+ more detail" will get you some info about signal strengths, transmission rates, round trip light times, and more.
I don't see one right this moment but it is common to find one of the 70m antennas talking to one of the Voyagers. Right now Goldstone antenna 14 (70m) is talking with New Horizons.
Captcha = acquire
The radiation is mostly cosmic and, if you've ever priced a chip that is hardened for space travel, you'll know it isn't a minor price difference. It's nasty.
It's not less than a millisecond, I think the minimum on-time is 15 milliseconds (you can go lower but you get disproportionate amounts of error).
It's an electrically-driven valve, a skinny tube with an injector at the end, which is embedded in the catalyst. When the fuel is released, it squirts out the injector and onto the catalyst. This causes it to decompose into steam (think putting hydrogen peroxide on a cut in your skin, but vastly more energetic). The steam is then accelerated out a nozzle, creating thrust.
As far as rocket engines go, it's not very efficient, and typically you have to heat the catalyst bed with a heater to keep the thermal shock of a firing from cracking the catalyst into dust. That, and development of "varnish" in the (tiny) injector passages - baked-on crud like a baking pan, is what causes them to wear out. One or both of those is apparently a factor in degradation of the prime attitude control set.
It's not terribly good for attitude control purposes due to the limited pulse life in the "fire once, wait 3 days, fire again" duty cycle, but it has the advantage of being very small (0.15 or so lb) and very inexpensive (I think something like $20000 a piece now, much less at the time) and has an extraordinary number of flights on it.