A 2009 rocketship
blasts its way though space
I’m glad to see that someone finally found an excuse to launch a streamlined spacecraft that will cruise above Earth, steadily firing its engines to keep it moving. (Aristotelian physicists take note.) The European Space Agency will soon launch this sleek piece of hardware on a mission of gravity measurement with unprecedented accuracy: The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) will carry accelerometers able to sense accelerations as little as 10–13 of what we tolerate on Earth. Using three pairs of these instruments, it will measure the difference in gravitational acceleration from one side of the spacecraft to the other, and this will provide the data needed to determine the gravitational shape of the Earth (a sort of idealized sea-level) to an accuracy of a centimeter or so. A lot can be learned by measuring this shape and monitoring how it changes from day to day as ocean currents shift and volcanoes swell.
A 1957 rocketship
blasts its way through space
Why must GOCE blast its way though space (if ion thrusters can be said to “blast”)? The reason is that measurements of Earth’s shape gain lateral resolution if the instruments are closer to the surface, and so GOCE has been engineered to orbit relatively deep in the tenuous outer atmosphere. The engine thrust will compensate for atmospheric drag from moment to moment, and will keep the craft aloft until its xenon tank empties, after about 20 months.
It’s a cool piece of technology (with no moving parts, 0.1 nm geometric stability, 0.01 K temperature control, etc. [pdf]), and best of all, it makes a satisfying image. I hope that GOCE serves us all well after its liftoff from the Plesetsk Cosmodrome, now scheduled for May.
Continued…
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“The engine thrust will compensate for atmospheric drag …, and will keep the craft aloft until its xeon tank empties…”
Xeon=microprocessor; assuming you mean “xenon”.
Ooops. Fixed, thanks.
As compensation for the typo, here’s a fun fact about xenon: It liquifies near room temperature at a pressure of about 50 atmospheres, and is a good, non-polar solvent for organic molecules — and, as a so-called (but not quite) “inert gas”, it forms a remarkably inert liquid. I expect that much of the exotic chemistry that can be performed with in vacuum (involving highly reactive radicals, carbenes, etc.) would work equally well in xenon.
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