Putting Together the Flight Schedule Puzzle

Right now the team is hunkered down in a conference room here at the hotel pouring over data sheets and weather charts. Underneath the chatter of the discussions you can hear them clicking and clacking away at laptop keyboards and calculators. So far everything is looking good and we should have a flight route for tomorrow soon.

I’ve been reading the comments and one of the most popular questions is, “when is Atlantis flying over my town?” It’s not as easy as you might think to answer that question. In order to get the shuttle home to Kennedy Space Center, we have quite a few rules and restrictions we have to follow.

First of all, we have to be very careful about the kind of weather we fly into and out of and through. And as you all know, forecasts change all the time. Flying from Southern California to Central Florida we are really dealing with weather planning across the entire southern half of the US — and meeting all our other strict constraints on temperature, clouds and precipitation. Put all of that together and you can see why it’s tough to say where we’re going to be and when we’re going to get there.

Today’s first leg flight is a perfect example of how crazy the scheduling challenges can be. We had originally planned for just a fuel layover in El Paso, then added an option to go north to Amarillo instead of El Paso and finally needed to pick just stopping at El Paso for the day.

Here’s what Ferry Operations Manager, Don McCormack said about it. He can explain it better than I can…

This is a good question that doesn’t have a quick easy answer.

First of all, we start with a list of airfields (about 20), primarily military bases that are on an approved list of airfields to be used during a ferry mission.  Each of these bases has agreed to accommodate an SCA/Orbiter landing and each has personnel trained to do so.  There is a very specific set of requirements that must be satisfied by each base.  These requirements include providing security for the Orbiter, providing a safe place to park an Orbiter that still has highly toxic commodities on board, has ground support equipment that can reach the Orbiter on top of the SCA if it is required, and not least of all, is willing to accept the disruption to normal operations that is caused when we arrive.  In addition, if the ferry stop is overnight, the base also arranges for transportation and lodging of the ferry team.

Second, the Orbiter has a very restrictive set of atmospheric/weather requirements.  We must, at all cost, avoid rain in flight.  Flying through rain will damage the Orbiter’s thermal protection system and result in a costly and long delay before the Orbiter’s next flight.  We also try very hard to avoid exposing the Orbiter to severe weather on the ground, which could also cause damage.  The Orbiter cannot be exposed to temperatures less than 15 F either in flight or on the ground and the Orbiter cannot fly at an altitude where the pressure is less than 8 psia.  These requirements typically limit our altitude to an 11,000 to 16,000 ft range.  So, the SCA/Orbiter route is largely driven by the bases that are available and the weather en route.

In addition, the SCA has a very limited range when ferrying the Orbiter.  That range depends primarily on the weight of the Orbiter and the air temperature.  Winds are also a factor.  The heavier the Orbiter is, the less fuel we can load into the SCA, pure and simple.  Without going into a lot of technical details, hotter air is less dense air and that too significantly impacts the performance of the aircraft.

Finally, hardware issues can also impact our route selection by causing delays.  During delays, the weather changes and often times so does the route.

So, there are many factors that drive the route we take with weather being the big one.  And as everyone can understand, predicting the weather is not an exact science.  That’s the biggest reason that it’s often the morning of the flight before we can say, with certainty, where we’re going.

I told you he knew his stuff.

13 thoughts on “Putting Together the Flight Schedule Puzzle”

  1. Dan-
    Wow, any heads up you can give us as to your time in and around Tallahassee, Florida would be greatly appreciated. Hope you can loop the capitol building a time or two.

    Best for a great mission,

  2. It’s just thrilling! I live in Nashville TN and saw a space shuttle ferry go over sometime ago and I could not believe my eyes! Once in Florida, I saw a lift off…I wish everyone could see either of these. I’m 70! My first airplane ride in 1964 was on an Eastern Airlines prop plane! I also love the Hubble …I look on line often.

    I hope to see you tomorrow. God speed!!

  3. Appreciate the updates. Once before when returning to FL NASA made a loop down to Houston, TX for a JSC flyby before going on to Barksdale, LA. Any heads-up on a Houston “loop” for the NASA/JSC group would be appreciated. I live near enough there to actually drive near there and see it with my own eyes instead of getting the Eyewitness News version, for a change.

    Again, appreciated if able. One more question, what is the tail number of this flight? I was able to track it once before. I think it was N911NA that time if memory serves correctly.

  4. I’m curious as to why the orbiter cannot fly at a pressure lower than 8 psia while mated to the SCA (assuming temperature is still within parameters at that altitude).

    If the shuttle can fly in low earth orbit where the absolute pressure is next to nothing, why is it limited to higher pressure during atmospheric flight? Does it have something to do with fluid dynamics?

    Thanks! I’m enjoying your pictures and videos. Unfortunately, I won’t see the ferry pass overhead up here in Chicago!

  5. It seams that a craft designed to travel into space, orbit the planet, reenter and land as a plane should be able to handle a little rain? I just don’t get why everything about the shuttle is so weather critical.

  6. It would be great if you could update your blog about an hour two in advance of crossing near fairly large towns. That way we could have our cameras ready and see if we can get any decent pictures. You’ve landed near me twice and the photo possibilities were terrific. Alas I wasn’t holding my camera at the time.

  7. Okay you have me baffled! Why must the Space Shuttle have a minimum 8 PSI atmospheric pressure while piggybacking on the SCA? This seems a like an odd requirment for a space ship.

  8. When, approximately, will the flight be near Melbourne & Cocoa Beach? We love to see the shuttle arrive safely back home.

  9. Shuttle is leaving El Paso at 7:45am CDT…going to San Antonio….the folks in Houston should be in a good place for at least a flyover. I saw it in Fort Worth last year…well worth the time to drive and see it…very impressive and the chances of seeing this is down to probably this time since the shuttle program is nearing its end and the liklehood it won’t land in CA again…

  10. Ok, why can’t the shuttle get wet? Doesn’t it get wet during thunderstorms on the launch pad? A shuttle has been sitting on the pad since before this mission for a launch in two weeks…it’s been rained on hasn’t it?

  11. The Orbiter avionics in the crew module are certified to operate at a minimum pressure of 8 psia (cabin leak scenario). Since the Orbiter cabin pressure is not monitored during ferry flight, a worst case assumption is made that the cabin has a leak and the pressure drops to atmospheric pressure. This is a conservative assumption because it is extremely unlikely that the cabin would leak during ferry. After all, it operates in a vacuum while on orbit. However, the ferry altitude is typically limited by temperature so the pressure requirement rarely comes into play operationally.

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