[meteorite-list] Fwd: Re: How much survives entry?
From: cdtucson at cox.net <cdtucson_at_meteoritecentral.com>
Date: Sat, 5 Dec 2009 19:24:59 -0500 Message-ID: <20091205192459.T7WVT.69096.imail_at_fed1rmwml33> > Chris, > Just so you know. When you look at the time and date of my posts you will see they are from Thursday. They are often delayed by several days. I don't know why they take so long to post to the list. I have not had time yet to read your references but I certainly will very soon. > You make entry sound so dramatic with your TNT figures but those amounts are gibberish to most of us non-scientists. > What makes me curious relative to those scary numbers you state, is the simple fact that we have been shuttling space ships and rockets for quite some time in and out of this atmosphere with relatively few TNT scale catastrophes. That said it seems that if we can do it so can a smooth rock. Even if you look at photos we have of asteroids they are very smooth themselves. Not jagged or non-aerodynamic. Makes you wonder why that is? Is there some mechanism that makes them smooth that we have never addressed yet? So, my presumption is that they have had millions of years of experience with space travel. Some we have even observed entering our atmosphere and then actually exiting without ever falling to Earths surface. These it seems to me that those rocks would be extra touch for the next go round. Because they now already must have a tough fusion crust which might be even better designed than our space shuttle tiles. And therefore should slip through our atmosphere with the greatest of ease. > So, keeping all of this in perspective , Sterling says the range is actually from 14%-100% is lost. This figure makes much more sense but it seems to me that some meteoroids MUST be equally as aerodynamic as our space shuttle and therefore can not be discounted from the equation. And therefore must make it through with little loss. > Just my humble common sense here. without math. Thanks again. Carl > -- > Carl or Debbie Esparza > Meteoritemax > > > ---- Chris Peterson <clp at alumni.caltech.edu> wrote: > > To get a visceral sense of why so little material survives entry, we can do > > a simple back-of-the-envelope calculation that lets us ignore messy details > > like entry angle, composition, and ablation physics. > > > > A very slow meteoroid (12 km/s) entering the atmosphere is carrying a > > kinetic energy of 72 MJ/kg. That's the equivalent of 17 kg of TNT per kg of > > meteoroid. Usually, all of that energy is dissipated in at most a few > > seconds (for our purposes, any surviving meteorites can be considered to > > have zero kinetic energy). > > > > A meteoroid that enters at 26 km/s (still slow enough for meteorites) gives > > up 338 MJ/kg, or 80 kg TNT per kg. > > > > Not hard to see from this just how rough a ride those meteoroids experience. > > The energy is what it is; the primary factor that determines survival is how > > long the energy is allowed to dissipate. That's why long lasting fireballs > > are much better candidates for meteorite producers than shorter ones. > > > > Chris > > > > ***************************************** > > Chris L Peterson > > Cloudbait Observatory > > http://www.cloudbait.com > > > > > > ----- Original Message ----- > > From: <cdtucson at cox.net> > > To: "Richard Kowalski" <damoclid at yahoo.com>; "meteoritelist" > > <meteorite-list at meteoritecentral.com> > > Sent: Thursday, December 03, 2009 9:32 PM > > Subject: Re: [meteorite-list] How much survives entry? > > > > > > > Richard, > > > Very nice show tonight. I recorded it so I can watch again. You were very > > > very good! You are (the) ultimate meteorite hunter. Congrats. > > > I'm pretty sure it has been stated on this list that the amount burned up > > > in passage through the atmosphere depends on so many different factors > > > that any guess might be right. > > > Anyway, Congrats again. > > > Carl > > > > ______________________________________________ > > http://www.meteoritecentral.com > > Meteorite-list mailing list > > Meteorite-list at meteoritecentral.com > > http://six.pairlist.net/mailman/listinfo/meteorite-list Received on Sat 05 Dec 2009 07:24:59 PM PST |
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