----- Original Message ----- From: "Ronn! Blankenship" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Saturday, January 25, 2003 9:24 PM Subject: Re: G-Whiz: Roller Coasters Get Astronaut Rating
> At 08:41 PM 1/25/03 -0600, Dan Minette wrote: > > >----- Original Message ----- > >From: "Ronn! Blankenship" <[EMAIL PROTECTED]> > >To: <[EMAIL PROTECTED]> > >Sent: Saturday, January 25, 2003 2:48 PM > >Subject: Re: G-Whiz: Roller Coasters Get Astronaut Rating > > > > > > > At 11:51 AM 1/25/03 -0600, Dan Minette wrote: > > > > > > >----- Original Message ----- > > > >From: "Robert Seeberger" <[EMAIL PROTECTED]> > > > >To: <[EMAIL PROTECTED]> > > > >Sent: Saturday, January 25, 2003 11:23 AM > > > >Subject: G-Whiz: Roller Coasters Get Astronaut Rating > > > > > > > > > > > > > > "What we do know, and what has been substantiated by science" Gibson > > > >added, > > > > > "is that riding a roller coaster imposes less g-forces on the body > >than > > > > > flopping down in a chair, sneezing or skipping rope. Ridding a roller > > > > > coaster is far safer than many of our other ordinary daily > >activities." > > > > > > > >An interesting related trivia question. Say you drop something solid > >and > > > >moderately hard, like a solid piece of glass or a crystal, on a hard > > > >surface, like a tile floor. What are the g forces involved when the > > > >glass/crystal hits the floor? > > > > > > > > > > > > Depends on how quickly the falling object comes to a halt. > > > > > > Assuming it was dropped from a height h and started at rest, at impact it > > > will be moving downward with a velocity of sqrt(2gh), so the acceleration > > > it experiences will be a = sqrt(2gh)/<delta-t>, where <delta-t> > >represents > > > the time it takes the object to come to a halt. That would depend on > > > things like the elasticity and tensile strength of the object and the > > > floor, but I don't know of any equation to compute <delta-t>. Probably > >the > > > best method would be to use high-speed photography to measure the time > >the > > > impact takes . . . > > > >Or, to measure the shock when it happens. The MWD industry is the roughest > >enviornment that crystals (such as NaI crystals) and photomultiplier tubes > >are expected to perform in. OK, its a pretty standard test in the MWD > >industry. The g force for something dropped from a meter onto a hard > >surface is typically around 1000 g's. The shock pulse is about 0.005 s I dropped a zero. The shock pulse is only 0.0005 s wide. > >wide. There are specifications I've written for detectors (comprising of a > >photomultiplier tube and a NaI crystal) to survive these shocks, as well as > >6 hours of 20 g rms random vibration. > > > Must be more stringent than the specs for the NaI(Tl) crystals and PM tubes > I recall from the unclear lab, or PM tubes used in astronomy. Although > fortunately I haven't actually tested any of them for impact resistance . . . Very much so. Designing packaging to meet those tolerances is a tremendous challange: especially when it is 20 g rms at 175C. A lifetime test for areospace is considered light qualification screening for MWD.[1] Dan M [1] I should probably define this for new folks on the list. MWD is Measurement While Drilling (oil wells). _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
