[AR] Re: FW: drag brakes (was Re: Cubesats orbital grenades ?)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 17 Dec 2017 23:56:59 -0500 (EST)
On Sun, 17 Dec 2017, Craig Fink wrote:
I would think that magnetic torquers/thrusters would be the way to go, at
end of life just leave the cubesat in deorbit mode. Or, traffic control with
them.
http://etd.fcla.edu/CF/CFE0001917/Ganesh_Karthik_G_200712_MS.pdf
If there were such a thing as a "magnetic thruster", yes. (As opposed to
a thruster which uses a magnetic field to help expel propellant; there are
many versions of that.)
He seems to be under the impression that he can get thrust out of torque
coils, somehow. Although it's kind of hard to tell, because there's also
a reference to fuel use, and a block diagram (Fig. 5, page 30) showing
"Thrusters (MET)" -- MET usually means Microwave Electrothermal Thruster,
which uses a microwave cavity to heat propellant. It's so badly written
that it's hard to tell what he thinks he's doing. Almost certainly he's
just confused; don't bet money on it working.
(Even just doing full *attitude control* with torque coils only is not
really feasible. There have been more than a few attempts, and as far as
I know they've all been failures. The problem is that torque coils can't
produce a torque around an axis parallel to the external magnetic field,
so at any given time they give you only two-axis control. If you also
have reaction wheels -- or possibly a spin-stabilized satellite -- to
store angular momentum temporarily, you can just store it up until you're
in a part of your orbit where the field is in a suitable direction to
unload it. That's how many LEO satellites, including Hubble and a bunch
of ours, do attitude control. But without wheels, last I heard, nobody's
made it work, in space as opposed to on paper.)
Henry
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