|
|
|
|
|
NASA considers relaxing daylight rule if Atlantis misses September window BY WILLIAM HARWOOD STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION Posted: August 29, 2006 If the shuttle Atlantis fails to get off the ground before the Sept. 7 end of its current launch window - a scenario that could delay the flight to late October - NASA managers may reconsider an earlier decision to only launch in daylight to ensure photo documentation of the ship's heat shield and external tank, officials said today. The issue became somewhat moot in the near term after NASA managers reversed an earlier decision to haul Atlantis off the pad because of concern about high winds from tropical storm Ernesto. If Atlantis can ride out the storm at pad 39B without any major problems, NASA should have one or two shots at getting the flight off the ground before Sept. 7 without changing any existing requirements. Had NASA pressed ahead with rollback, however, the agency would have lost any chance of launching Atlantis before the end of the window without help from the Russians or a change in the lighted launch requirement. While NASA could launch as late as Sept. 13 based on lighting alone, any launch past Sept. 7 would require the Russians to delay launch of a Soyuz rocket carrying the next station crew and that, in turn, would force the outgoing station crew to land in pre-dawn darkness. The Russians don't want to do that and while discussions are ongoing, it appears extremely unlikely they will change their position. The next lighted launch opportunity for Atlantis is a two-day window opening Oct. 26. But if Atlantis doesn't' get off before Sept. 7, and if NASA managers give up the lighting requirement, the shuttle could take off shortly after the Soyuz carrying the outgoing station crew departs from the lab complex. Assuming NASA uses up the existing window, the Soyuz would take off Sept. 18 and dock with the station two days later. The outgoing station crew would land Sept. 29. Under that scenario, the earliest Atlantis could launch, in predawn darkness, would be late September or, more likely, early October. "We want to work the technical discussion of lighting and see where it leads us and we'll keep you informed as we get there," Hale told reporters less than an hour before Atlantis reversed course and headed back to the pad. In the wake of the 2003 Columbia disaster, NASA managers said the first two return-to-flight missions would be launched in daylight to ensure good photo documentation of the heat shield and external tank insulation. After a large piece of foam insulation fell off the shuttle Discovery's tank during the first post-Columbia mission, Hale extended the daylight launch requirement to one additional mission - STS-115 aboard Atlantis. After standing down a year to make more changes to the tank's insulation, Discovery flew again last July and its tank performed well. No major pieces of foam came off during passage through the dense lower atmosphere when the most critical damage can occur. But Discovery's tank, like the one being used by Atlantis, features buildups of foam insulation called ice-frost ramps that are considered dangerous. NASA is working to redesign the ramps, but a fix will not be in place until next year. From Hale's perspective, the lighted launch requirement is directly tied to the need to gather data that can help engineers improve the tank design. But with the possibility of a long delay if Atlantis misses the September window, Hale has asked engineers to revisit the lighting issue. "We have kicked off a study to review our requirement for lighting," Hale said. "This will be the third flight that we have asked for lighting and going into STS-115, our position was that having successful data and consistent performance we would drop that requirement for subsequent flights and fly at night as required. "So we have asked ourselves now, what are the rationales for our requirements, have we exceeded some of it? For example, if we wait for the next lighted launch window, which is very late in October, I think it's the 26th of October, one of the things we wanted to potentially get was to roll data that you'd get from the lighted pictures of the ET into the ice-frost ramp redesign. We're working that very hard. "We expect to finalize our design and make some engineering decisions about the first of October," he said. "So at that point, getting data late in October is not very useful to inform those engineering decisions. I'm just using that as an example of the kind of review we're going forward with to say do we, in fact, still want to hold firm to a day-lit launch requirement for this particular flight? Or is it possible that we would be willing to launch with less than optimum lightning conditions?" Hale said he expects a preliminary report by the end of next week. "We have not made a decision, we're just going through the technical review at this point," he said. "We obviously will talk to a lot of folks about that decision before we make it. So lighting, I think, is under discussion." Hale was asked if his willingness to consider amending a long-standing, if self-imposed, safety guideline in the face of perceived "schedule pressure" might send the wrong signal to the work force. He strongly disagreed and because this issue is so critical to the near-term shuttle launch schedule, here is his complete response: "The original test flight philosophy was to have two flights with the daylight launch, which was STS-114 and STS-121," he said. "We elected, and it was largely my decision, to extend the daylight planning requirement for one more flight, STS-115. There seemed to be a number of reasons why that would be an interesting and good thing to do. "But none of which were related to the safety of the flight in progress. Because the safety of the flight in progress, in this case STS-115, is assured by the 100 percent inspection that we do of the thermal protection system of the orbiter before we commit to landing. And it's also backed up with layers of redundancy, with our repair capability that we have worked very long and hard to get together for on-orbit repairs of the thermal protection system. Finally, as a last-ditch effort, (we have) a way to rescue the crew from an extended stay on board the space station if we had suffered large damage and were unable to repair it. So we think we have defense in depth here. "The question about having a day-lit launch really is to gather data for the future flights after the current one, which is to say STS-116 and subsequent. Now, the principle thing we're doing on the tank is to modify the ice-frost ramps. We have a large group of folks ... working on that redesign. We have done a large number of ground tests, we're getting ready to go back into the wind tunnel with modified designs. "So we think we're coming to a decision point here in the not veryÊ distant future to make final decisions about those modifications, which we are going to start putting on the tank that will fly early next year," he said. "So the question is, are we missing something, is there something in a requirement which we are not thinking about that says that we should stay with the lighted launch requirement? "We know that if you have for the duration of the shuttle program a requirement to launch in daylight, we cannot fulfill this manifest, it is physically impossible. So at some point, we want to go back to having around-the-clock launch capability. Originally, that was scheduled to be for the STS-115 flight. "We extended the constraint for one flight because we thought there were some good reasons for it and what I've asked the team to do is go off and examine those reasons and see if they are still applicable. If they are, we will stay with the lighted launch window. If, in fact, we have been overcome by events and they are no longer requirements, they do not inform the redesign for the ice-frost ramps, then perhaps we have a constraint that is overly burdensome and is not providing additional safety to the program and it makes sense then to proceed with a non-lighted launch."
|
|
|
|
STS-115 patch The official crew patch for the STS-115 mission of space shuttle Atlantis to resume orbital construction of the International Space Station. Choose your store:U.S. - U.K. - E.U. - Worldwide  |
||||||||||||||||||||
|
MISSION INDEX |
||||||||||||||||||||||||||
Space shuttle Atlantis is delivered to Kennedy Space Center's launch pad 39B on August 2 to begin final preparations for blastoff on the STS-115 mission to resume construction of the International Space Station.
Just after 1 a.m. local time August 2, the crawler-transporter began the slow move out of the Vehicle Assembly Building carrying space shuttle Atlantis toward the launch pad.
Space shuttle Atlantis is transported to the cavernous Vehicle Assembly Building where the ship will be mated to the external fuel tank and twin solid rocket boosters for a late-August liftoff.
VIDEO:
OFFICIALS EXPLAIN INITIAL SCRUB 