Ask The Mission Team - Question and Answer Session
Shuttle Weather Officer
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RichO from Elk Grove, IL: What are the major factors in the weather like rain, storms, high winds on the ground and in the atmosphere that can scrub a launch?
Well, we're mainly looking at the natural and triggered lightning threats. We're looking at clouds within 10 nautical miles of the launch pad. We're looking at the thickness of the clouds and the base of the clouds, and also what height they get to -- particularly if they're cumulous clouds, because we're concerned that we may trigger a lightning strike on launch. We also watch for natural lightning, as well, but that's a little more straightforward. So we're watching for those clouds and the thickness of the clouds within 10 nautical miles of the launch pad. Also, we look for landing weather at the Shuttle Landing Facility. We're looking particularly at showers and storms within 20 nautical miles of the Shuttle Landing Facility.
Another thing that's a concern is wind. We're concerned about surface winds at the launch pad exceeding 19 knots if the winds are from the northeast. It's directionally dependent, so that can also be as high as 34 knots, depending on the direction the wind is from. And for the Shuttle Landing Facility, a crosswind of 15 knots is a concern for landing, and also a headwind of 25 knots, or a tailwind of 10 knots of sustained wind peaking up to 15 knots. So wind can be a concern, as well.
We can't fly through any precipitation. So we don't want to launch through any precipitation, or come within 20 nautical miles of precipitation for the Shuttle Landing Facility.
And also, there's a concern for ceiling at the launch pad. If the ceiling is less than 6,000 feet, we'll be having the forward observers for the range evaluating to determine if the vehicle can be viewed with the optical sights from the 45th Space Wing.
Temperatures are also a concern for launch. We don't want the temperatures to be too hot. Greater than 99 degrees Fahrenheit is a problem that we usually don't have. But in the wintertime, sometimes we can run into cold temperature issues because if temperatures get below 48 degrees, we have to start evaluating relative humidity and wind, and see the combination of those and determine if we are going to be red for launch.
So we're looking for natural and triggered lightning -- we're looking at clouds for that -- and we're looking for the wind at the surface, precipitation in the area, and also ceiling in the area, and finally at temperatures for launch.
Tucker from White: What landing site would NASA use if Kennedy and Edwards weather was unacceptable?
Well, if Kennedy and Edwards weather was unacceptable and we tried it for a few days and weren't able to land there, the other site that's available is at White Sands Missile Range. It's called Northrop Landing Facility, and that's the site that we would use as a third possibility for landing the shuttle. That's in New Mexico.
Derek from Vincent: What is the maximum and minimum wind speed that the space shuttle can launch and land in?
Well, Derek, it depends on the direction of the wind. We are looking at winds at both the launch pad and the Shuttle Landing Facility for a return-to-launch-site landing, in case there's an abort. And so, for launch, if the winds are anywhere from 19 knots to 34 knots -- it depends on the direction -- then we'd be concerned. For example, if the winds are from the northeast, greater than 19 knots, that would be a problem for us for launch. We would have to go red for the weather constraints. For the Shuttle Landing Facility, the winds are, the main concern is a crosswind of 15 knots, a peak wind, or a headwind of 25 knots, or a tailwind of 10 knots sustained wind peaking up to 15 knots.
There's also wind concerns for winds aloft. Those are evaluated with computer algorithms. There's not a specific maximum or minimum wind speed for that. Those are evaluated differently, so we're not looking for any specific maximum or minimum loft.
Kris from Jacksonville: Does a tropical storm like Alberto pose any threat to the shuttle while on the pad and what happens if the expected winds exceed safety levels?
Kris, a tropical storm like Alberto would definitely pose a threat to the shuttle on the pad. We watch those very closely and spent a lot of time, actually, talking about Alberto. We are mainly concerned that the winds will exceed 70 knots of peak wind. If we do expect the winds to exceed 70 knots of peak wind, then the shuttle will be rolled back from the launch pad before those winds occur. And actually, the shuttle needs to be rolled back before we hit 40 knots of sustained wind peaking up to 60 knots. So the decision is for 70 knots of peak wind, and then the rollback must occur before we hit 40 knots peaking to 60. And we look at every storm that is developing out there and talk several times a day as these storms are developing and becoming a threat. So we watch these storms very closely.
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