Ares Rockets: More Blogging
Published on Aug 4, 2006 at 5:29 pm.
7 Comments.
Filed under NASA, rockets, space exploration.
Not too long ago, I posted an entry about the new Ares Rockets that NASA is designing. I mentioned that portions of the new rockets are based on Shuttle technology, in particular the external tank. Well, that includes the problematic foam. There was an article in the local paper here today about just that. As with most of the news in the local paper, local reporters didn’t come up with it. This was an AP story. The reporter pointed out that this is the same foam that keeps flaking off, and that a piece of foam falling off on liftoff was what did the damage to the Columbia that ultimately proved fatal to that craft. However, the report also goes on to say that this should not be a problem. Well, I thought that I might expand on that.Foam has been flaking off of the Shuttle external tank since the early days of the Space Shuttle in the 1980’s. At first, engineers correcty were concerned. However, as time passed without a major incident relating to the foam problems, their concerns were put on the back burner. Then, in the 1990’s, the manufacturing process for the external tanks changed to use a new, more environmentally friendly way of applying foam to the tanks. I am all for saving the environment. But, folks, we need to be reasonable. The problem with the new method was that the foam was even more likely to flake off than before. Concerns about this went unheeded. Even when a particularly large chunk of foam fell off and seriously damaged a support brace holding the solid rocket boosters to the external tank on the STS-112 mission, higher ups didn’t take the matter seriously. Not, until the loss of the Columbia on mission STS-107, that is.So, can foam flaking be dangerous with this new design? Well, yes. But, not nearly as dangerous as with the Shuttle program. First of all, the biggest concern that NASA has with foam flaking is that the foam flaking off might damage the orbiter’s heat shield. The heat shield is composed of rather delicate porous ceramic tiles that are easy to damage. Hitting them hard enough can break or scour them. Even more fragile are the tiles on certain parts of the orbiter, like on the leading surfaces of the wings, where the heat load is greatest. These tiles are much more brittle, and they are easier to damage. A foam strike on the leading edge of the Columbia’s port wing is what is believed to have doomed the craft.Â
However, the new CEV won’t have that problem. This new craft rides atop the rockets. So, any foam shedding will not be able to strike the crew vehicle. Furthermore, it is expected that foam shedding should not strike anything important. The Ares I, which will be used to lift the astronauts into space in their CEV will not even have fins to damage. This rocket is steered with gimballed rocket motor nozzles. There is a faring around the base of the rocket, but foam should actually have moved away from the rocket body enough by the time that it reaches the faring that impact is unlikely, and if impact did occur, serious damage is also unlikely. In theory, that is. A worse case scenario would be if foam near the top of the rocket peeled off, and that exposed more foam to aerodynamic stresses that cause it to peel off, and so forth. One could imagine foam breaking away from an entire side of the rocket. This could, in theory, lead to handling problems. I don’t think that any problems of this sort would bring down the rocket, but then it would be unwise not to consider every possibility, however remote. And, this is, indeed, an exceedingly remote possibility. Such a cascading foam peeling has never happened, and I don’t think that it can even happen without a whole lot of things going wrong with rocket manufacture, foam composition, foam application, rocket handling after fabrication, etc. It would take a remarkable series of failures to even lead to such a foam cascade, which would unlikely have a disastrous result even if it did occur.
However, the Ares V is another story. This is the heavy lift vehicle. It will be the rocket to lift the major heavy components of Lunar and Martian missions into space. It will be used for future major launches of space station components. And, it is more susceptable to damage. This is because it is composed of a central core with two solid rockets strapped to the side. Despite the fact that Atlantis safely completed the STS-112 mission, there was serious damage caused by foam shedding to a strut holding one of the solid rockets onto the external tank. The strut held. However, in only just held. Had the damage happened earlier in the flight, had the damage been slightly more severe, had the damage happened closer to the end of the strut, then the solid rocket might have torn away from the external tank. Well, actually, only part of the solid rocket would have torn away. The other part would have torn off part of the external tank, resulting in a repeat of the sort of even that destroyed the Challenger. This is still a danger. And this danger would still exist with the Ares V rocket. It is a remote possibility, but then so is the possibility of damage such as that which downed Columbia. Again, ignoring it is dumb. However, even a loss of an Ares V, while bad, and disastrous for the completion of a mission, would not result in loss of life (unless, of course, the debris fell on someone). The astronauts will be riding into space aboard an Ares I, which is unlikely to suffer horrible damage from any foam shedding.
So, there you have more on the Ares rockets.
Oh, and I am still looking to move my blog. I’ll post a forwarding address when that happens. Interestingly, this new thing that they’ve put into effect here actually seems to work better with Firefox than it does with Internet Explorer. Imagine that. A Microsoft product that doesn’t work well with other Microsoft things. Still, not all features work, and I don’t like it. So, I am looking to move.
-Astroprof
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Greg on August 11, 2006 at 8:44 pm: 1
The Ares I does not use the shuttle external tank, and it isn’t clear that it will have any external foam. The Ares V tank has changed and will not be what the shuttle uses. The new core is actually based on the Saturn V design, which to my knowledge didn’t have foam. However, if you have ever watched the films of a Saturn V launch, you can see lots of ice sluffing off as the vehicle begins to move.
Astroprof on August 11, 2006 at 10:49 pm: 2
I wrote this after reading several news stories about the Ares rockets. Just about all mentioned foam, and several cited NASA engineers talking about the foam on the Ares rockets.
Howerver, I found this NASA fact sheet that seems to suggest that, indeed, the Ares V core is based on a Saturn V design, but it doesn\’t go into specifics as to which part of the Saturn V it is based upon. Definitely, the Saturn V had no external foam, and so that would seem to suggest that perhaps the core would also have no external foam. But, earlier things that I had read indicated that the new upper stage of the Ares I was to have foam. Even earlier documents indicated that the Ares V central core was to be based upon Shuttle external tank technology.
Rockets go through a large number of design changes, some very significant and radical ones, between when they are first conceived and when they are built. No doubt a lot of what I have said will be obsolete by the time that the things actually are done.
Thanks for pointing out the design change. I am sure that there are plenty that I don\’t know about yet, and I am sure that there will be more.
Justin on August 12, 2006 at 10:24 pm: 3
The foam wouldn’t make a difference in terms of crew safety, as the CEV sits on top of the rocket, as opposed to being strapped on the side like the Shuttle. Falling foam would have nothing to hit.
Justin on August 12, 2006 at 10:28 pm: 4
Oops sorry, I didn’t know that the article expanded. I read the excerpt on the front page and didn’t notice the ellipse in the brackets.
Greg on August 15, 2006 at 3:24 pm: 5
My source was the NASA Fact Sheets. The whole idea originally was to use as much of the shuttle components and technology as possible to make launch systems quickly and cheaply. But that has been evolving over time. Yesterday I found an article from just a few weeks ago where the deputy director for the program talked about using a tank design similar to the shuttle’s for the Cargo Launch Vehicle. So who knows? I have been trying to develop a simulation model for my work, and I am going nuts trying to nail down the numbers.
Nick on December 29, 2006 at 7:16 pm: 6
What I keep sking myself is why even use the foam? The foam was used on the shuttle due to the fact that it was strapped to the side of the ET and foam would prevent ice from forming, and crashing into the shuttle. With the capsule on top what could the ice do to the vehicle? Look at the Saturn rocket, or Atlas or Delta II. Ice poses no saftey issue to the payload or engines.
Astroprof on December 30, 2006 at 1:00 am: 7
You need some sort of insulation when using cryogenic propellants. However, before the Shuttle, this insulation was always interior to the rocket structure. There is no skin on the Shuttle’s external tank to save on weight. Heck, even a thick coat of paint would probably help!