🚀 go-pugleaf

In article <dcu028127ggnbr00tf8ka6hhpdgr9omftj@4ax.com>, 
jonk@infinitefactors.org says...
> 
> On Mon, 06 Aug 2012 21:26:55 -0400, Walter Banks
> <walter@bytecraft.com> wrote:
> 
> >Jon Kirwan wrote:
> >
> >> On Mon, 06 Aug 2012 16:15:32 +1000, Don McKenzie <5V@2.5A>
> >> wrote:
> >>
> >> >Been there, done that :-)
> >> >
> >> >http://www.abc.net.au/news/2012-08-06/nasa-celebrates-successful-mars-landing/4180454
> >>
> >> I started watching the NASA channel about 4 hours ago and
> >> stayed with it. (Still watching, while they are doing the
> >> news conference event and just finished congradulating each
> >> member of the EDL team (entry, descent, and landing.)
> >>
> >> Australia was part of this success, as well -- at least in
> >> terms of participating in the very much needed communications
> >> portions.
> >>
> >> What impresses me the most is that this trip was about 350
> >> million miles, ending in a tight coordination with two
> >> orbiting satellites, the ODY and MRO, and deploying novel
> >> technologies to land a 1 ton vehicle (if I heard correct.)
> >> Hard to believe that all of this could come together as well
> >> as it did.
> >
> >I like many watch the landing  coverage. There are two
> >things that really impressed me.
> >
> >1) The navigation to get them there on a really small landing
> >    footprint
> >
> >2) With all of the technology in the systems to land this
> >successfully, one number still is impressive. There were still
> >250 single point possible failures. The math against it working
> >was astronomical. If there was anyone involved reading
> >this I am all ears and you have my congratulations.
> >
> >Listing to the systems readout after the landing showed it
> >almost everything was nominal.
> >
> >Congratulations all
> 
> Of all those single points of failure, the ones that worried
> me the most were the pyros. You can test a lot of things --
> like the 65,000 pounds of force the parachute had to bear.
> But you can't test the ACTUAL pyros you will use. No matter
> what you do, the ones you place in there can't have been
> tested. We know how to make explosives of great uniformity,
> of course. But all of that has to go into a system and it
> must fire exactly correctly, under buffeting circumstances,
> without a single point of failure in a single pyro. Just one
> and that is it. Not that the rest wasn't also difficult. But
> some of the things, since as the novel use of an imbalance in
> weight distribution in order to permit direction control
> during entry, can have errors in one part of the software be
> compensated by the outer control loop in another part. So
> even there, there is a backup hope. But the pyros either
> work, or don't. That's what I was watching mostly for, though
> the rest was also sincerely knuckle-whitening as well.
> 
However, you can have redundancy in some types of pyros such as wire
cutters and other release mechanisms.  Whether such redundancy is worth
the extra pyro weight, cabling and switching is a matter for experts
to decide.


Mark Borgerson