NASA leaves its Artemis I rocket exposed to winds beyond design limits
Hurricane Nicole made landfall early Thursday morning near Vero Beach on Florida’s east coast. Because Nicole had a very large eye, nearly 60 miles in diameter, the strongest winds were well north of this landing position.
As a result, the Kennedy Space Center received some of Nicole’s most intense gusts of wind on Wednesday evening and Thursday morning. While such Category 1 hurricane winds are unlikely to damage facilities, they are a cause for concern as the space agency has left its Artemis I mission — consisting of the Space Launch System rocket and Orion spacecraft — on a trail. at Launch Complex-39B. The pad is a stone’s throw from the Atlantic Ocean.
How strong were the winds? The National Weather Service hosts data from NASA sensors attached to the launch pad’s three light towers on a public website. It can be a little difficult to interpret the readings because there are sensors at heights ranging from 132 feet to 457 feet. However, most of the publicly available data seems to come from a height of about 70 meters, which corresponds to the area of the Space Launch System rocket where the core stage is attached to the top stage. The entire pile reaches a height of about 370 feet above the ground.
Prior to Nicole’s arrival, NASA said the SLS rocket was designed to withstand wind gusts of 74.4 knots. In addition, the agency Tuesday mentioned in a blog post“Current forecasts predict that the greatest risks on the trail are high winds that are not expected to exceed the SLS design.”
However, publicly available records indicate that the missile 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 at the National Weather Service site, with multiple gusts above NASA’s design level. There may be some margin built into the design limit of 74.4 knots.
The space agency is wrong to suggest that forecasters did not predict such winds from Nicole. The reality is that the National Hurricane Center’s wind speed probability predictions accounted for the possibility of such high winds, even if they weren’t the most likely scenario. On Tuesday, shortly before NASA released its blog post update downplaying the risks to Nicole’s Artemis I, the National Hurricane Center predicted a 15 percent chance of hurricane-force winds at the Kennedy Space Center, which would have generated gusts similar to those measured at the launch site Thursday morning.
So what’s going to happen now? Nominally, the space agency is still targeting a launch attempt at 1:04 a.m. ET (06:04 UTC) on Wednesday, Nov. 16. Theoretically, this remains possible, but in reality it seems unlikely. When it is safe for NASA employees and contractors to return to the Kennedy Space Center, perhaps later today or Friday, they will begin inspecting the vehicle.
According to Phil Metzger, an engineer who worked on the Space Shuttle program for NASA, the most likely concern will be the rocket’s structural integrity after exposure to extended periods of high winds. A rocket is designed to go uphill, so while its structure can withstand intense pressure and wind in the vertical direction, it is not designed to withstand similar winds in the horizontal direction.
In a series of tweetsMetzger predicted it will be a busy few weeks for structural engineers to assess the risks of storm damage and possibly request exemptions to allow the vehicle to fly after it has been subjected to these loads. This will be a difficult task. There is no ability to X-ray the structures in the rocket, so this process involves performing and re-running structural calculations. At some point, program leadership will have to decide whether the risk — including the possibility of the missile breaking apart during launch — is too great to fly without further inspections or repairs.
So why didn’t NASA just roll back for cover? The timing is key here. It takes about three days to prepare and roll the rocket back from the launch pad to the protective Vehicle Assembly Building at Kennedy Space Center. NASA therefore probably should have made the rollback decision on Sunday. At the time, the most likely outcome, predicted by forecasters, was that the missile would have been exposed to winds of 40 knots.
Space agency officials have not gone public to discuss their decision-making process, but NASA’s blog post from Tuesday suggests that a final call was indeed made on Sunday night: “Based on forecast weather conditions and options to roll back for the storm, it decided agency Sunday night that the safest launch hardware option was to keep the Space Launch System rocket and Orion spacecraft on the path.”
From the space agency’s vantage point on Sunday, there was clearly a non-zero risk of damaging winds to the rocket, but it was low, probably less than 5 percent. Rolling back the rocket at that time would have eliminated several launch attempts, and perhaps even wiped out the entire November launch window, for the highly anticipated Artemis I mission. If the launch had been delayed until December, that would have created a host of other problems for the agency, perhaps most importantly, that the solid rocket booster’s longevity certification – these massive powder-based boosters have been stacked for nearly two years – was almost over. expired.
So NASA had many good reasons to pull the Artemis I mission off the launch pad this month. That’s why they gambled a bit with the weather. They may have lost.
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