Phobos Mission?

Flymuffins wrote:

>"(2) Crew vehicle tethered to surface from 30 - 50 m height (3-point
tether system for energy conservation)"

It does sound a bit weird. This caught my eye:

"Given the decay of the Phobos orbit, will landing, EVA, or spiking
significantly perturb it?"

Hmmm...Phobos masses about 1.08*10^16 kg. Say four billion loaded
supertankers, or one and a half million Great Pyramids of Cheops. ;-)
There's no way anything "significant" could be done to Phobos orbit,
short of NASA taking the world's nuclear arsenal, Bruce Willis and some
dodgy Hollywood effects there. ;-)

>How is a mass supposed to just hang up there 30 - 50 m off the
surface of Phobos? Why? Is this really a NASA document?

If the mass is tethered on the far side of Phobos, and forced to
co-orbit (in a higher-but-slower track round Mars), then there would be
a net tension on the cable(s), just like there would be on an asteroid
tethered at the "far" end of an Earth orbital tower, beyond the
geosynchronous point. At some altitude the tension on the tether will
balance the local gravitational attraction of Phobos...but my (early
morning) spreadsheet for this case suggests that altitude is nearer
3.2km above the surface of Phobos and not lower.

Is it a NASA document? Don't know. It's a very poor summary if it is.

Regards,

Andy G