Saturday, January 13, 2007

NASA's Shuttle Carrier Aircraft (Part 1) - Interview with SCA Crew Chief Pete Seidl

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Everyone knows that the orbiter of the Space Transportation System (or "STS," and more popularly called the "Space Shuttle) doesn't always land back at the Kennedy Space Center at Cape Canaveral in Florida. Sometimes, it lands at Edwards Air Force Base and, if needed, it could land at White Sands or one of several other emergency landing sites around the world.

That's great, but it puts the orbiter several thousand miles away from its launching facility at the cape.

So how does the orbiter get around? Most of you know that the answer is that you mount it on the top of a specially-modified Boeing 747 called a Shuttle Carrier Aircraft or "SCA." But, if you're like me, you probably didn't know much about the SCAs. How are they different from a stock 747? How many are there? What's it like to maintain an aircraft like that? What's it like to fly it?

Well, if there's one thing you know about Airspeed, it's that we never pass up the opportunity to go right to the source to get real answers from the people closest to the aircraft. And that's just what we did for this special two-part series.

First, a bit about the SCAs. There are two of them. NASA 905 (tail number N905NA) is a Boeing 747-100 and the other, NASA 911 (tail number N911NA) is a short-range Boeing 747-100SR.

The two aircraft are very similar and have nearly identical operating characteristics. If you happen to be lucky enough to see one on the ramp but can't see the tail number, NASA 905 has two upper-deck windows on each side while NASA 911 has five.

The SCAs have a maximum gross taxi weight of 711,000 pounds. A stock 747-100 weighs about 380,000 pounds empty and an SCA weighs even more than that. Once you add 180,000 pounds or more for the orbiter, you have less than 140,000 pounds or so left for fuel and other stuff. And there's precious little other stuff because even using the entire remaining 140,000 or so pounds for fuel only gives you about a 1,000-mile range.

That's actually a little gratifying, because these are some of the same concerns that those of us who have flown ultralights, Cessna 152s, or light sport aircraft know a thing or two about. If you've ever left your flight bag, spare change, and shoelaces back at the FBO and still had to closely manage the amount of fuel in the plane to get two average-sized guys into a C-152 under max gross, you've had the same thing on your mind - at least at some scale - that our guest today deals with very frequently.

We start off the series on the SCA by talking to SCA crew chief Pete Seidl. Pete started working with the SCAs in 1979. He's an employee of Computer Sciences Corporation (or "CSC") under contract to NASA's Shuttle Support Operations Office at NASA's Dryden Flight Research Center in Southern California. He heads a team of five at NASA Dryden that does the regular maintenance on the two SCAs. Among other things, Pete was on the crew that took NASA 905 and the Enterprise orbiter to the Paris Airshow in 1983.

Before we get going, a couple of notes for non-space-junkies.

You'll hear us talk about hypergolic fuels. Hypergolic fuels ignite immediately when the two components of the fuel come together. They're very reliable, even if their components are sometimes highly toxic. Examples are hydrazine paired with nitric acid and monomethylhydrazine (MMH) paired with nitrogen tetroxide, the latter pair of which is used in the space shuttle's reaction control system. Early uses included a critical application for the Apollo program's lunar modules.

One other insider point. Moving orbiters is complex enough with a crack team, lots of support, and only one orbiter at a time to move. But, in early 2001, NASA came within 37 minutes of having a formation flight of the two SCAs, each with an orbiter aboard.

On February 20, 2001, Space Shuttle Atlantis unexpectedly had to land at Edwards. Atlantis needed to be received, processed, and ferried back to the Orbiter Processing Facility at Kennedy Space Center in Florida. Space Shuttle Discovery was undergoing upgrades at Boeing's facility in nearby Palmdale and needed to be at the cape in preparation for launch by March 8. NASA 905 was already in Palmdale awaiting mating of Discovery for the ferry flight, but NASA 911 was at Evergreen Air Center in Marana, Arizona undergoing maintenance.

Two orbiters, two SCAs, an almost simultaneous deadline, and not much time to organize and carry out an amazingly complex set of operations. Pete and his team faced an unprecedented challenge. But, on March 1, 2001, the two SCAs, each with a national treasure mounted atop it, launched for Kennedy Space Center with NASA 905 and Columbia taking off at 11:00 a.m. local and NASA 911 with Atlantis taking off at 11:37. Although each encountered bad weather and other difficulties, each made it to Florida in time.

The aircraft took separate routes and a formation flight would have been impractical and beyond the mission risk profile, but at least I'm not the only one to have allowed the thought to enter my head and think that that would have been a deeply moving picture.

Anyway, on to the interview. We caught up with Pete Seidl at an office at NASA Dryden a mere 150 feet from the nose of NASA 905.

[Interview audio.]

Many thanks to Pete Seidl for taking some time out of his day to talk to us.

Tune in next time for the view from the cockpit of the NASA Shuttle Carrier Aircraft with SCA pilot, project pilot, former astronaut, Shuttle Approach and Landing Test pilot, STS-3 pilot, and STS 51-F commander Gordon Fullerton.


A special note of thanks from the Airspeed crew goes out to a heroic listener who works for Apple. We redirected the feed for the podcast on Labor Day weekend over to Libsyn from a prior RSS provider. Apparently, whether due to a glitch in the RSS provider's system or iTunes, when we let the old forwarded feed go away, we winked out of existence on iTunes. Thanks to some fast footwork on the part of a listener and the willingness of the folks at iTunes to hustle the re-listing of the podcast through, we got back online quickly and lost little, if any, or our subscriber base that subscribes through iTunes.

Thanks to Apple and to that heroic listener for helping us keep Airspeed up and available.


Image used per NASA's policy entitled Using NASA Imagery and Linking to NASA Web Sites (October 13, 2005) located at

See more pictures of the SCA at

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