On Mar 4, 2008, at 4:59 PM, Apptech wrote:
> BCC's: Photo worth a look if you haven't seen it. 300 kB.
>
>> As far as I'm aware NASA has dumped the MMU and its no
>> longer carried,
>> EVA's where they want to go places now use the manipulator
>> arm in its
>> place.
>
>> Are you saying that if an astronaut is knocked away from
>> the shuttle,
>> there is no plan for retrieving said astronaut ?
>
> I believe the intention was to say that there is never any
> chance of them being knocked away. ie they are always
> tethered. Tether discipline would be similar to safety line
> discipline for construction workers who use them - but the
> result of getting it terminally wrong would be a slower but
> more certain death and a lack of need for burial and
> guaranteed auto-cremation in due course. I suspect that
> tether discipline is enforced utterly rigorously as part of
> standard utterly inviolate checklists. If you've ever seen
> the procedure for eg installing a screw in a satellite under
> assembly you'll get the idea.

They're using TWO tethers, one ALWAYS on something, the other is  
moved... tether over tether to get somewhere.  It's drilled and  
drilled and drilled into their heads, and is as natural as breathing  
after a while.  All that time in the simulation tanks isn't for just  
showing them how to do the work they're about to do.

This is why there's usually one Astronaut on the robotic arm  
instead... that person is "safer" and only one mobile Astronaut has to  
be tracked by lots of eyeballs.

The EVA crew inside is not only watching for procedures for the work  
being done, but you hear regular calls of, "Are you tethered?" or  
"Your tether has floated behind you."  Stuff like that.

The EVA crew, robotic arm crew, everyone not already occupied is  
typically observing the work being done "outside" with eyeballs,  
binoculars, cameras, whatever -- and ANYONE can call for a "stop" to  
re-evaluate tether or any other safety status issue.

This is all pretty clear if you listen to the audio from NASA Select  
(TV) during EVA's.  Free on the web, too.

Other interesting things are that transmitters (RF) are kept to a  
minimun to avoid interference to the Astronaut's communications  
systems, which includes shutting down the Amateur Radio station on  
board, etc... before every EVA.   (There is a packet radio station on  
board that's completely automated for ground-based hams to "talk"  
through.  It can not be left on during EVA, docking, anything going on  
"outside"... same with the cross-band repeater when it's configured  
and active.)

They take EVA's pretty darn seriously... lots of safety steps, and  
lots of eyeballs and ears (hopefully) paying attention.

Even ground personnel are involved... for camera remote control and  
watching what's going on, since there's more cameras than the Shuttle  
has monitors to watch full-time.  SOMEONE is watching EVERY camera,  
and they're all pointed at the action... well, that is as long as  
their auto-irises are working and they're not going to be fried by an  
orbital sunrise directly into the lens... (lots of camera pointing  
activities from the ground are done constantly to avoid camera  
damage)...

--
Nate Duehr
nate@natetech.com



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