As Hurricane Nicole spun over Florida, NASA’s bajillion dollar SLS rocket sat atop Launch Complex-39B. Eric Berger:
Prior to Nicole’s arrival, NASA said its SLS rocket was designed to withstand wind gusts of 74.4 knots. Moreover, the agency stated on Tuesday in a blog post, “Current forecasts predict the greatest risks at the pad are high winds that are not expected to exceed the SLS design.”
From the publicly available data, however, it appears that the rocket was exposed to wind gusts near, at, or above 74.4 knots for several hours on Thursday morning. A peak gust of 87 knots was reported on the National Weather Service site, with multiple gusts above NASA’s design levels. It is possible that the 74.4-knot design limit has some margin built into it.
The time the space agency would have needed to begin rolling the rocket back to safety within the Vehicle Assembly Building, Nicole’s estimated winds were far below the safety margin. Time will tell if the choice to keep the rocket outside was a bad one, as Berger writes:
According to Phil Metzger, an engineer who worked on the space shuttle program for NASA, the most likely concern will be the structural integrity of the rocket after being exposed to prolonged periods of high winds. A rocket is designed to go upward, so although its structure can endure intense pressure and winds in a vertical direction, it is not designed to withstand similar winds in the horizontal direction.
In a series of tweets, Metzger predicted that it will be a busy couple of weeks for structural engineers to assess the risks of damage from the storm and potentially seek waivers to fly the vehicle after its exposure to these loads. This will be a difficult task. There is no ability to X-ray the structures inside the rocket, so this process will involve running, and re-running, structural calculations. At some point the program’s leadership will have to decide whether the risk—which includes the potential for the rocket to break apart during launch—is too high to fly without further inspections or remedial work.
Jim Free, NASA’s Associate Administrator for Exploration Systems Development, issued a statement on the issue, citing slower wind speeds than otherwise reported:
While wind sensors at the launch pad detected peak wind gusts up to 82 mph (71 knots) at the 60-foot level, this is within the rocket’s capability. We anticipate clearing the vehicle for those conditions shortly.
Our team is conducting initial visual check-outs of the rocket, spacecraft, and ground system equipment with the cameras at the launch pad. Camera inspections show very minor damage such as loose caulk and tears in weather coverings. The team will conduct additional onsite walk down inspections of the vehicle soon.
We took the decision to keep Orion and SLS at the launch pad very seriously, reviewing the data in front of us and making the best decision possible with high uncertainty in predicting the weather four days out. With the unexpected change to the forecast, returning to the Vehicle Assembly Building was deemed to be too risky in high winds, and the team decided the launch pad was the safest place for the rocket to weather the storm.