bees@infoswx.UUCP (01/24/86)
Shuttle delays are very complicated and are addressed on an individual basis. There is no set schedule of delay times for a given set of problems. When Lockeed Space Operations Corp. (LSOC) has to address a problem, there is a meeting of 70 - 80 people to determine the requirements to solve the problem and what delays must be effected. Additionally there are people on-line from KSC, JSP and the individual companies responsible for whatever the current payload is. One reason that there is not a set schedule of delay times is that each shuttle mission is different. Different payloads require different processing and may have critical time limits. For instance, on the last launch, delays caused the blood sacks to have to be replaced. Often each launch brings updates and enhancements to the shuttles which may require different processing in that area. Everything is a complication. star!fisher has already explained hold times and launch windows. If a problem is small and can be fixed during the current launch window, the countdown can be put on hold. If a problem is more complex (see star!fisher's Auxiliary Power Unit example) things get increasingly worse. A shuttle can only hold fuel for so long. The fuel cools down the main engines, which must be in a specific temperature range for the launch. If the APUs are shutdown, the temperature controls have to be cooled before a restart. There are also safety considerations to be made each time something has to be done to a shuttle. Entry into the aft to fix a problem requires evacuation of the fuel. This is a many step process with certain time periods between each step. On another note, NASA can handle overlapping missions. It all depends on the specific requirements of the mission. Some missions are intentionally scheduled to overlap. Every mission is a different story! ...sounds like Rod Stewart B-) Ray Davis Teknekron Infoswitch, Richardson, TX infoswx!bees, (214)644-0570