piner@pur-phy.UUCP (Richard Piner) (01/30/86)
This is just my own idle speculation about Tuesday's sad events. I too watched the slow motion pictures of the shuttle's destruction. I must agree that it is unlikely that a burn through of the SRB was the cause. I was watching the CBS special last night. I noted a bright flash between the shuttle and the external tank. Dan Rather said that the location of the flash was in the area of the umbilical connecting the shuttle to the tank. If this is true, a failer there could explain what happened. I will offer here my own scenario. Several hours before launch, the shuttle is exposed to a fair amount of moisture. Then the temperature drops forming ice. We know that this did happen. What if some of that moister was inside some part of the connector where the umbilical joins the shuttle. If that moisture froze, it could damage the connector. While that umbilical and connector are designed to take very cold temperatures, I do not know if they were designed to take a freeze / thaw cycle with water all over them. Anyone who lives up north knows that water and cold can do an amazing amount of damage. Let us assume that indeed the connection or umbilical were damaged. Why didn't the shuttle blow up on the pad as soon as fuel started flowing into the shuttle? Well, hydrogen will dissipate at an incredible rate. If there were a modest leak in the umbilical system, it is unlikely that enough hydrogen to cause an explosion would reach the engine flames or hydrogen ignitors many feet below. Hydrogen would just go away when vented in open air. But as the shuttle begins to gain speed, the air stream would tend to draw the hydrogen towards the engines in a smaller and smaller, denser and denser steam. When the order to go full throttle was given, the flow from the tank almost doubled and the flow though the faulty connector increased in proportion. Now the hydrogen stream reaching the engines is dense enought to ignite. The flame shoots up the stream like a lit fuse. Until it gets to the umbilical. Then BOOM! This would explain the flame seen at the base of the tank first, followed by the flash at the umbilical. By the way, burning hydrogen makes no visible flame, so any flame we saw must be due to some other material being burned, such as paint or insulation. This would explain why it might not be possible to see the whole stream buring. In fact, it might have been burning for some time, we just couldn't see it until it got some of the paint on the SRBs to burn. To sum it up, what we may have seen was the same effect as a flash back on a hydrogen fueled bunsen burner. Anyway, I hope I'm wrong. Richard Piner Purdue Physics Dept. piner@pur-phy.UUCP
dwg1@mhuxn.UUCP (GOULD) (01/31/86)
>What if ... moisture was inside some part of the connector >where the umbilical joins the shuttle. If that moisture froze, >it could damage the connector... >... If there were a modest leak in the umbilical system ... as the >shuttle begins to gain speed, the air stream would tend to draw the >hydrogen towards the engines ... When the order to go full throttle >was given, the flow from the tank almost doubled and the flow though >the faulty connector increased in proportion... This would explain >the flame seen at the base of the tank first, followed by the flash >at the umbilical. > (Richard Piner @Purdue Univ.) I had a similar guess after discussion with friends: the umbilical connector probably failed. The obvious question is: WHY? Moisture induced pre-launch damage could be it, but >While watching my VCR replay ... Using the fast scan ... Challenger >seemed to be wobbling back and forth a little bit. > (Michael Ross @3M Company) increased stress from improper movement of the airframe control surfaces (e.g., elevators, rudder, etc.) could account for the failure, as could mechanical wearout of the connector retention system - Challenger has been re-used several times now ... (I sure hope that wasn't the cause). I trust that NASA will eventually tell us what happened... >The best tribute we can pay to the memory of the Challenger >crew is to perpetuate their own forward thinking. > (Steve Miller @Bell Communications Research Inc.) Well Stated. ----------------------------------------------------------------- Doug Gould @ AT&T Bell Laboratories, Murray Hill, NJ mhuxn!dwg1 "The views expressed here are my own and do not represent those of my employer"