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“NASA Shuttle Carrier Aircraft – the Titans of the Space Shuttle Program” PART II

By Suresh A. Atapattu
November 26, 2012


Part I: http://www.airliners.net/aviation-articles/read.main?id=157

One of the most spectacular engineering marvels in aviation is NASA’s special Boeing 747 Shuttle Carrier Aircraft’s ability to transport the orbiter on its back. The piggyback method of carrying the orbiter represents a very innovative engineering solution for overcoming an otherwise complex problem of moving the orbiter to and from its launch pad at Kennedy Space Center, Florida and alternate landing sites in California, Europe (never used) and North Africa (never used). California was also used for major orbiter maintenance when there were four orbiters in existence hence that involved ferry flights. This ended after the Columbia disaster in 2003.



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Photo © Julian Leek

Maiden arrival of Space Shuttle Columbia to KSC on NASA's modified 747 aircraft


Given the large size and weight of the orbiters, it would have been impractical to transport it by rail from any of it alternative landing sites in California and New Mexico (backup to the backup site). Also, the abort sites for launching orbiters are in North Africa and Europe hence the effort required to transport by rail and sea back to the United States would be uneconomic and too time consuming. The impact on the flight schedule would be detrimental. The special 747 offers the ability to move the orbiter within days from its landing site to KSC or to the factory in California.

Conceived due to the ingenuity and dedication of NASA engineer John Kiker, the concept was not initially accepted but soon proved to be viable. He proposed carrying the shuttle orbiter on top of a modified Boeing 747 and demonstrated it to skeptical NASA officials using models. After extensive wind tunnel testing and modeling, NASA went ahead with the piggyback concept. Prior to the ALT program, more than 1400 hours of wind tunnel testing had taken place to validate the concept. In the absence of the SCA, one concept had the attachment of engines to the wings of the orbiter along with the assorted plumbing to fuel tanks in the payload bay thus allowing powered transcontinental ferry flights by the orbiters!

For a period of time in 1973, NASA considered the use of either a Lockheed C-5A Galaxy or a Boeing 747 as the SCA aircraft. The orbiter would be placed on top of the C-5A just like on the 747 SCA. In August and October 1973, contracts were awarded to Lockheed and Boeing, respectively, to conduct preliminary feasibility studies to evaluate whether the orbiter could separate clearly from the back of the carrier aircraft. Test results demonstrated that the 747 had several advantages over the C-5A. Compared with the C-5A, the 747 was shown to be safer and to have a longer estimated range. Additionally, the 747 could use shorter runways, and had a longer structural life. The added cost of maintaining the larger C-5 and economics of acquisition handicapped the C-5 alternative. The commercially available and proven 747 was favored. The rest is now history!

Shuttle Carrier Aircraft

In response to the official request by Christopher Kraft, director of NASA JSC, the NASA Space Shuttle Program Office approved the purchase of a Boeing 747 in June 1974. Simultaneously, the start of structural assembly of the crew module of the prototype orbiter, Enterprise (OV-101), commenced. NASA paid $15.6 million for a used Boeing 747-123. The aircraft purchased was an ex-American Airline 747 with registration N9668 (cn 20107/86). This aircraft (line number 86) had its first flight on October 15th 1970. It served with American Airlines for it entire commercial life and was registered with NASA as N905NA on July 7, 1974. Between August and December 1976, Boeing modified the aircraft for use as a SCA under the direction of NASA.



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Photo © Richard Vandervord

Note the American Airlines imprint on the fuselage despite the removal of the paint.


The major 747 hardware changes:

• Three struts with associated interior structural strengthening protrude from the top of the fuselage (two aft, one forward) on which the orbiter is attached.

• Two additional vertical stabilizers, one on each end of the standard horizontal stabilizer, to enhance directional stability.



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Photo © AirNikon Collection-Pima Air and Space Museum





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Photo © AirNikon Collection-Pima Air and Space Museum



• Removal of all interior furnishings and equipment aft of the forward No. 1 doors.



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Photo © Gary Chambers

Rear bulkhead showing the large stuffed spider that was a fixture. The SCA crew had a nice sense of humor.




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Photo © Suresh A. Atapattu

The area behind the cockpit on N911NA still retains a few of the JAL era seats and wallpaper. The galley (not seen here) is also from her JAL service days and it still retains even the JAL coffee maker




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Photo © Jeremy Frew

The area around the staircase leading to the top deck. Note that the seats in the nose area remain.




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Photo © Suresh A. Atapattu

The nose area seating that is used by crew during positioning flights. Only the flightdeck is occupied during orbiter ferry flights.




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Photo © Jack Hannen

The stripped main cabin area.



• Instrumentation used by SCA flight crews and engineers to monitor orbiter electrical loads during the ferry flights and also during pre- and post-ferry flight operations.

• Improvements also were made to the Pratt and Whitney JT-9D engines to provide more power.

• A flight crew escape system, consisting of an exit tunnel extending from the flight deck to a hatch in the bottom of the fuselage, was installed during the modifications. The system also included a pyrotechnic system to activate the hatch release and cabin window release mechanisms. In a catastrophic emergency, the parachute wearing pilots and flight engineer would activate explosives that would blow the fuselage hatch for bail-out. Next, they would jump into the tunnel in the floor of the top deck of the SCA and slide down and out the hole, escaping into the air beneath the airplane. Activation of the tunnel hole explosives also activated pyrotechnic devices designed to blow out 10 windows above each wing in order to equalize the on-board air pressure allowing the crew to slide down the tunnel. The flight crew escape system was removed from the NASA 905 following the successful completion of the ALT program.

Some interesting operational facts about the SCA:

• The SCA are particular vulnerable to issues of center of gravity due to their stacked nature. Each have about 2 tons of pig iron up-front in the former first class section of the aircraft, and about 3.5 tons of pea gravel in the cargo hold for keeping the aircraft’s center of gravity forward when a heavy Shuttle is mounted on top. Without the gravel and iron, the tail-heavy Shuttles, made so by their rocket engines, could cause the 747s to experience flight instability. So, the gravel and iron provide much-needed weight toward the noses of the 747s to balance out the problem.

• Typical fuel burn is around 38,500 pounds per hour with a 176, 000 pound orbiter on the top. This is twice the normal burn rate of the unloaded SCA. The weight of the orbiter varies from one to the other and also depending on the mission flown.

• There is a constant rumble heard in the SCA cabin during the flight because of the wake of the orbiter hitting the vertical stabilizer of the 747.

• Limited on altitude with the Orbiter to eight pounds per square inch and temperature limited to minus nine degrees centigrade (15 degrees Fahrenheit). Due to this restriction, the SCA carrying an orbiter frequently stays beneath 10,000feet.

• The loaded SCA avoids all clouds and thunderstorms. It can only encounter light turbulence.

• 10,000 feet of runway is typical takeoff length with an orbiter.

• Six pilots and four flight engineers crew a typical ferry flight with multiple stops.

• According to SCA chief flight engineer, Henry Taylor: “There are four main, one center wing, and two reserve tanks. We normally only use fuel out of the mains and reserves. We don’t use fuel out of center wing mainly because the Orbiter just takes up too much weight. The airplane can only weigh 710,000 pounds at takeoff. So with a 200-and-something-thousand-pound Orbiter we can’t put a full load of fuel on. So we never get fuel in the center because you make it too heavy.”

• During Orbiter ferry mission the SCA provides power to the Orbiter to keep systems functioning. The SCA flight engineer monitors the power setting every 15 minutes and if there is a disruption, the SCA will consider landing to prevent any damage to the internal systems of the orbiter.

SCA Specifications:
Wingspan: 195 ft. 8 in.
Length: 231 ft. 10 in.
Height: Top of vertical stabilizer, 63 ft. 5 in. To top of cockpit area, 32 ft. 1 in.
Maximum gross taxi weight: 713,000 lbs
Maximum gross brake release weight: 710,000 lbs
Maximum gross landing weight: 600,000 lbs
Weight: Basic weight:
o NASA 905, 318,053 lbs.
o NASA 911, 323,034 lbs.

Engines
• Four Pratt and Whitney JT9D-7J gas turbine engines, each producing 50,000 lbs of thrust.

Performance

Airspeed limits with, and without an orbiter: 250 knots or Mach 0.6
Range:
Typical mated, 1000 nautical miles (with reserves); maximum unmated, 5500 nautical miles
Altitude:
o Typical cruise with orbiter: 13,000-15,000 ft;
o typical cruise unmated: 24,000-26,000 ft.
o Minimum temperature at altitude 15 degrees (F) (-9 degrees C)
Fuel Capacity
• 47,210 gallons (316,307 lbs) jet fuel
Crew
• Minimum for flight is two pilots and one flight engineer. Minimum for mated flight is two pilots and two flight engineers.


Milestones in the history of N905NA
NASA delivery flight: July 18,1974
First SCA flight: Dec. 16, 1976
First captive flight Enterprise: Feb. 18, 1977
First captive flight Columbia: March 9,1979
First captive flight Challenger: July 4,1982
New paint scheme replacing the American Airline colors: April 1983
First ferry flight Discovery: Nov. 6,1983
First ferry flight Atlantis: April 12,1985
“376” stenciled on starboard side SCA for Paris Air Show: June 1983
Current color scheme: Feb. 1996
Flight hours/landings as of April 10,2012: 10968.60 Hrs/ 6285 landings



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Photo © Dean Straw

The SCA shows the American Airlines colors which remained till April 1983


On January 14, 1977, was delivered to NASA Dryden by Fitzhugh "Fitz" Fulton and Tom McMurtry. Later that month, on 31 January, the space shuttle orbiter Enterprise (OV-101) was trucked to Dryden from the Rockwell International facility in Palmdale to begin preparation for the Approach and Landing Test project; hence N905NA has a permanent and important place in the history of the shuttle program even before the orbiters themselves.

NASA utilized only one SCA (N905NA) until the publication of the Rogers Commission report on the Space Shuttle Challenger disaster. The commission pointed out that NASA experience indicates the orbiter will divert into Edwards more than 30 percent of the time due to the dynamic weather present in Florida at the SLF. NASA must therefore plan to use Edwards routinely. This requires reserving six days in the post-landing processing schedule for the Orbiter's ferry trip back to Florida. It also requires redundancy in the ferry aircraft hence the existence of only one SCA meant a single point of failure. In response to the commission recommendations, NASA purchased N911NA in 1989. NASA 911 (20781 ln: 221), a Boeing 747-100SR short-range version. This airframe was the first SR built. The initial 747SR model, the −100SR, had a strengthened body structure and undercarriage to accommodate the added stress accumulated from a greater number of takeoffs and landings. The wings had extra structural support and this extended to the fuselage and the landing gear. It became the second Shuttle Carrier Aircraft. With her first flight on August 31, 1973, she was flown in commercial airline service by Japan Air Lines (registration JA8117) for about 15 years. After modifications by Boeing, it was delivered to NASA on Nov. 20, 1990 to serve as a carrier aircraft for the space shuttles for the next 21 years.





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Photo © Howard Chaloner

N911NA in service with Japan Air Lines as JA8117.




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Photo © George W. Hamlin

N911NA in service with Japan Air Lines as JA8117.


Milestones in the history of N911NA
NASA delivery flight: Oct 27,1988
First SCA flight: Sept. 25,1990
New paint scheme: Nov. 1990
First Ferry Flight of Endeavour: May 3,1991
Current color scheme: Oct. 1995
Flight hours at retirement on Feb. 10, 2012: 33,004.1 flight hours



To be continued...

Written by
Suresh A. Atapattu

Suresh A. Atapattu is a biomedical engineer specializing in cardiology. He has had a longstanding research interest in the functioning of the human physiology in spaceflight. He was given unprecedented access and permission by NASA to document Space Shuttle processing at the Kennedy Space Center over the last decade of operations including the retirement and placement in museums. Some of his NASA photography can be seen at his website at http://www.atapattu.net or here at Airliners.net http://tinyurl.com/d7mrsa2

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