From: vince@offshore.ai (Vincent Cate) Newsgroups: sci.space.tech Subject: Re: Heat Sink Heat Shields References: <5dcb47db.0310011151.51d744ce@posting.google.com> <9186edb5.0310012120.758e3a2a@posting.google.com> NNTP-Posting-Host: 207.42.133.230 henry@spsystems.net (Henry Spencer) wrote in message news:... > >Is there any chance that the the US ICBMs with "copper heatsinks" > >could have really been copper coated beryllium? > > Nope, straight copper. Heavy, yes, but cheap, easily fabricated, and > mechanically durable. (Whereas beryllium, although light, is costly, > very difficult to work with, and brittle.) Do you know what sort of trajectories they fly? Like do they come in at a very high angle? If I simulate 7.7 km/sec coming in at 45 degrees it generates like 1/8th the total heat of coming in at 0 degrees. This could explain how they could get by with copper and I can't for a human capsule with L/D of 0.4 and CD of 1. Of course the G load is not human friendly at like 120 Gs. :-) That is probably even more Gs than you want your nukes to have to deal with. > Glenn never made a suborbital Mercury flight. Shepard and Grissom flew on > Mercury's original beryllium heatsink heatshield. Thanks. > Its one big advantage is something that actually isn't in your list: > stiffness. But for a heatsink this does not seem like a feature I was looking for. For other things, sure. > Wild idea of the week: I wonder if you could take a leaf from Apollo's > book, and make a heatsink heatshield out of hexagonal beryllium rods in a > copper or stainless-steel honeycomb? The honeycomb would take mechanical > loads and hold the beryllium together, eliminating brittleness issues, > while the beryllium handled most of the heat. It seems like something could be done. Do you know how much trouble the brittleness issue was for Mercury? > One book, interestingly enough, mentions the idea of adding expendable > (perhaps liquid) coolant behind a heatsink heatshield, but says the idea > was not pursued, because straight heatsinks seemed adequate for satellite > applications, while nothing short of ablators would do for the most > demanding warhead flight profiles. It seems like this becomes a good idea when you use water and then use the steam for transpiration/film-cooling. Also, when you are making a reusable vehicle you may not be as willing to use ablation. You could at least fly your heatsink/transpiration capsule any number of times before you put people on it. -- Vince