Hurricane Season and Rollbacks

June 1 thru November 30. The Atlantic Hurricane Season. As June 1 passed I was reminded how much ‘fun’ it was to experience.

From the earliest days of our manned spaceflight programs, the Launch Director was responsible for two things that outweighed all others, including launch itself. These were to protect the safety of the workforce, and to protect the flight and ground hardware. Obviously, these are everyone’s responsibility, and everyone took them very seriously. But when major processing decisions were required that had significant safety and/or processing implications, the LD made the final call.

Some of those decisions are well-known, the final decision to launch being the most obvious. Others were also the responsibility of the LD but not as visible. The decision to roll the vehicle out to the launch pad, establishing and enforcing the employee work time rules, and approving personnel exposure to launch pad hazards after external tank (ET) fueling are a few. The decision to roll the vehicle back to the Vehicle Assembly Building (VAB) from the launch pad was also given to the LD (along with a Shuttle Program rep that I’ll explain later).

What could drive us to roll back? Remember the woodpeckers and the damage they did to the ET that couldn’t be fully repaired at the pad? (That was STS-70, in June 1995.) How about the hydrogen leaks in the 1990s?

There was another event that could force us to bring the stack back to the VAB for safekeeping – threatening hurricanes.

If you recall, the vehicle spent about a month at the pad in preparation for launch. Unlike expendable rockets that can spend as little as one day at the pad, the Shuttle needed quite a bit more preparation time before launch. Payload installation, ordnance installations, hypergolic fueling, TCDT—those are just four of the numerous pre-flight jobs that had to be done at the pad. They were required for every mission regardless of the calendar.

Enter Hurricane Season. The Space Shuttle would spend that month of prep time on its seaside launch pad, less than ½ mile from the usually tranquil Atlantic Ocean. On occasion, that tranquility would be broken by the effects from tropical storms and hurricanes. If the Shuttle’s presence on the pad and tropical weather coincided, tough decisions would be required.

Protect the hardware. Protect the people.

The Shuttle program benefitted from the weather forecasts and advice from some of the best meteorologists in the world. The 45th Space Wing of the US Air Force provided weather support for us. Every day—not just during hurricane season, but every day—I would hold a 10-minute call with them for the daily forecast. Numerous processing groups would tie in to benefit from the information and how it might affect their work plans that day. If tropical systems began to form, the intensity on the calls would increase. If there were also a Shuttle at the pad, it would take on an additional air of importance and urgency. Daily calls would increase to twice per day, then every six hours, or even more as the threat got closer.

Ultimately, if the storm track, intensity, and speed combined to actually threaten KSC in the near future we would need to roll the Shuttle back to the VAB to ride out the storm. We could hunker down at the pad if the winds didn’t exceed 60 knots. But if the forecast had higher winds, we needed to get to the safety of the VAB, and this needed to be done early enough that allowed the workers time to get home to deal with their own, final storm preparations.

A lot went into those discussions, but for this entry it can be summarized as balancing the desire to stay at the pad and launch on time vs taking the protection option and delaying launch at least two weeks. But remember: the top priority was safety for the people and hardware. Launch schedules were secondary. But the balance needed to be struck, and it was the responsibility of the Launch Director and the Shuttle Program Manager (delegated to his KSC rep) to do it.

Why would it delay launch at least two weeks if we rolled back to the VAB? The three sets of required tasks, when combined, needed about two weeks to complete—rollback preparations including the roll itself, stay time in the VAB as the storm passed by, and then roll back out and re-perform pad operations undone in Step 1.

To get ready to roll back was at least two full days of activity—usually three—and was done with the storm bearing down on us and our families and homes. How long it took to prepare for rollback depended how close to launch we were when the decision to roll was made. The closer to launch meant more work had been performed that needed to be undone. The Payload Bay Doors needed to be closed after securing the payload. The aft compartment of the Orbiter needed to be closed with special doors, the side hatch closed, etc. Add to these relatively obvious preps things like hypergolic and ordnance systems securing, Pad-to-MLP disconnections (power, comm, gases, data lines, etc.), and you get the idea. The “final” disconnection was this contraption called the ‘9099 interface’ – a large bank of data and power lines on the side of the MLP. Once disconnected, all the work done to verify those systems were launch-ready became history—work that would have to be completely re-done once the Shuttle came back to the launch pad.

We had to roll the crawler out to the launch pad. The rollback itself was typically eight hours or so followed by rudimentary connections of the MLP to the VAB shore systems. Then the final workers could go home and shutter their houses.

Stay time on the VAB was storm-dependent of course, but let’s say three to four days until the “all clear” was declared to reopen KSC. If storm damage existed that would prevent normal work, add that repair time.

The workforce returned to work and got ready to roll back out to the pad. Two days minimum to get ready. Roll out was the same eight hours, and usually at night in the summer to avoid the afternoon thunderstorms. Once at the pad, you have to reconnect everything (reconnecting each interface means going through the complete set of checks to ensure that the connectors are properly mated again) and get back into the same posture as before the decision was made to ride out the storm in the VAB. Add back those three days or so. Then pick a new launch day, verifying that the new launch date doesn’t impact other planned launches at the Cape, other vehicles arriving at or departing the International Space Station, and so on.

All told, the decision to ride out a storm in the VAB meant an impact to the launch schedule of about two weeks.

No magic, just a lot of (necessary) work to protect the flight hardware.

Next week: Tropical Storm Ernesto and the “Half-Rollback”

Author: Mike Leinbach

Mike was the final Space Shuttle Launch Director at NASA's John F. Kennedy Space Center. He led the launch team for all Shuttle missions from August 2000 to the end of the program in 2011, giving the final "go" for every launch.

4 thoughts on “Hurricane Season and Rollbacks”

  1. Mr Leinbach, how much did the decision to use SRBs/hypergolics on STS effec the amount of processing that occurred in the VAB vs the pad? Seems from your statement that a lot of pad time was necessitated by processing work that ELVs today do off pad. thanks for your insights!


    1. Thx for the question, Ron. Hypergolic fuels definitely played a major role in the time we needed to prepare the vehicle at the pad. It took approximately 3.5 days to load all the fuels and during this time that was the only job performed due to its extremely hazardous nature. The hydrazine and nitrogen tetroxide used required the technicians to be in SCAPE suits in case of leaks. The Self Contained Atmospheric Protective Ensemble fully protected the guys and had either compressed air packs inside the suits or air supplied by hoses attached to the suits. We used the hypers for the Auxiliary Power Units in the SRBs as you suggest, and for the Orbiter APUs as well. The thrusters used hypers, too, as did the Orbital Maneuvering System engines. And while we loaded several tanks simultaneously it still took the 3.5 days to get it all in. It was all done at the pad so if we had leaks we would at least be outside vs in an enclosed building. (For completeness, the APUs provided the gas used to turn the hydraulic pump impellers that created the hydraulic power needed for gimbaling the SRB nozzles. Same concept for Orbiter hydraulic power generation.) Mike


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