From: vince@offshore.ai (Vincent Cate) Newsgroups: sci.space.tech Subject: Re: Heat Sink Heat Shields References: <5dcb47db.0310011151.51d744ce@posting.google.com> <9186edb5.0310051121.737e64cd@posting.google.com> NNTP-Posting-Host: 209.88.68.230 henry@spsystems.net (Henry Spencer) wrote in message news:... > Ely's "Return from Space" (which was published in 1966 but clearly written > before Mercury was very well defined) says that beryllium was abandoned > for early ICBM heatshields because of the prohibitive difficulty and cost > of fabricating large shapes out of a costly, brittle, toxic metal. > > (He says that even copper presented significant fabrication problems at > the sizes involved.) On page 128 of "Re-entry and Planetary Entry Physics and Technology - II" by W. H. T. Loh, 1968, a graph indicates that the reentry time time for ICBM is just over 0.1 min, while IRBM is around 0.2 min and Apollo is just under 10 min. In my simulator, this kind of steep reentry reduces the total heat by something like a factor of 8 compared to a shallow human tolerable one. It also has higher heating rates, so copper's higher conductivity could be important. With the lower total heat, you don't really need beryllium. So it now makes sense to me that they used copper and not beryllium for some ICBMs. However, for a manned reusable suborbital vehicle designed to rendezvous with a rotovator (something I am interested in) beryllium still seems very interesting. If the problem is just cost/difficulty of fabrication, and they managed it for Mercury, then it could be reasonable for a reusable vehicle which can amortize the costs over many flights. -- Vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vincent Cate Space Tether Enthusiast vince@offshore.ai http://spacetethers.com/ Anguilla, East Caribbean http://offshore.ai/vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You have to take life as it happens, but you should try to make it happen the way you want to take it. - German Proverb