The SCA | Shuttle Carrier Aircraft | NASA | Only vehicle

The SCA - Shuttle Carrier Aircraft

There were once two 747's which carried spacecrafts on their back. They were called the SCA, abbreviation for Shuttle Carrier Aircraft. They were operated by NASA for the transportation of the space shuttles from their alternative landing sites to their main landing site for repair and reuse.

The Shuttle Carrier Aircraft

Where do the space shuttles land?

The space shuttles are intended to land at the Kennedy Space Center in Florida.

Inside the Kennedy Space Center, Florida

Why do they land at different locations?

The alternate landing sites of the shuttles include the Vandenberg Air Force Base and Edwards Air Force Base in California and the White Sands Space Harbor in New Mexico. These are the landing sites in America alone. Even though they were intended to land at the Kennedy Space Center, most of them couldn't do it because of several reasons. The primary reason is weather issues.

Vandenberg Air Force Base, California

Edwards Air Force Base, California

Space Shuttle (ST-3) Landing at White Sands Space Harbor, New Mexico

How were the 747's used?

Two modified 747's were used by NASA for the purpose of transporting the shuttles from the alternate landing sites to the main landing site at Kennedy Air Force Base in Florida for their repair and reuse. 

The space shuttles can be sent for any future missions to space. They have to be refitted with new protection plates. The protection plates on the space shuttle become heated due to very high temperatures when entering the Earth's atmosphere. 

When coming close to the surface, It becomes rapidly cooled down. This weakens the plates and has to be replaced. Similarly, all the systems which aid in its working have to be thoroughly inspected to ensure that it works fine. The SCA brings it here to this facility.

Worn out heat protection plates visible in the space shuttle

How were they able to carry space shuttles?

The two 747's were heavily modified. They were of different variants and were acquired from different airlines. The first one was a 747-100 acquired from American Airlines and the second one was a 747-100SR (Short Range) acquired from Japan Airlines. 

They were retrofitted by removing all the business and economy seats, most of the lavatories, overhead bins, and other items that wouldn't be of any use. This helped to reduce weight significantly. 

The first-class seats remained and were used by NASA passengers. The top of the aircraft was also fitted with equipment to hold the shuttle in place. There were also additional two vertical stabilizers at the rear end to make the transport efficient. This made both the aircraft a 'Triple Tail'.

The two SCA 

Inside the SCA

First Class Seats of the SCA

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How was the shuttle mounted on the airplanes?

The space shuttles were attached to the back of the 747's with a special 'Mate-Demate' device. NASA built four of them in Edwards Air Force Base, Kennedy Space Center, Vandenberg Air Force Base, and a mobile one. Since Vandenberg Air Force Base canceled its shuttle program, it was moved to the US Air Force Plant 42. The mobile device was used in cases where the space shuttle lands in different places apart from the alternate sites.

The mate-Demate device at Edwards Air Force Base

How this affected the aircraft?

Having the space shuttle mounted at the top of the 747's caused a loss in the aerodynamical structure of the airplanes. This made both the aircraft lose their range and had to be refueled at various spots to get to California. An aerial refueling method was planned to be added to both planes. But this was proven not efficient and was called off at last. Even though it did have technical problems like this, it proved to be very useful for NASA.

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Credits for the design

The credits for this unique design go to John Kiker, a NASA engineer. He proposed a model of an RC model of an airplane and an RC model of a space shuttle. His idea was accepted by NASA and this is where the iconic 'Piggyback Ride' story started.

John Kiker with his RC models

The RC 747 and the space shuttle in Action

Where are they now?

One of the aircraft is kept on display at the Joe Davies Heritage Airpark, Palmdale. The other plane is on display at the Space Center Houston, Texas.

Space Center Houston, Texas

  

Joe Davies Heritage Airpark, Palmdale

Public Attraction

The SCA became a very popular public attraction. People would gather around favorable places where the aircraft would pass and would watch spacecraft and aircraft coming together because of human mastermind and development.

The SCA passing by Hollywood

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Best Workings Of SCA:

Pressure plotting experiments conjointly show that because the angle of attack is altered the distribution of pressure over the surface changes significantly, and in consequence, there'll be a movement of the center of pressure. 

The position of the middle of pressure is typically outlined as being a definite proportion of the chord from the vanguard. 

It typical pressure distribution over Associate in Nursing surface at variable angles of attack. 

In these diagrams solely the raised part of the whole pressure has been aforethought - the drag part has hardly any impact on the position of the centre of pressure. 

It will be noticed that at a negative angle, and even at 0 degree, the pressure on the side close to the vanguard is increased on top of traditional, which on the lower surface is decreased; this causes the loop within the pressure diagram, which means that this portion of the surface is being pushed downward, whereas the rear portion is being pushed upwards, so that the full surface tends to show over nose initial. 

So, even at the angle of zero raise, once the upward and downward forces area unit equal, there's a nose-down pitching movement on the aerofoil; as are seen later this is often a matter of goodly significance. 

Golf stroke it otherwise, at these negative angles the centre of pressure may be a great distance back - the sole place wherever we have a tendency to might place one force that would have an equivalent moment or turning impact because the distributed pressure would be an extended means behind the edge, in fact at zero raise it couldn't offer a pitching moment {at all|in the least|the least bit|in the slightest degree|in Associate in Nursing respect} unless it were an infinite distance back - that is absurd. 

Perhaps a additional smart means of golf stroke it's to mention that there's one or two working on the surface, and one or two has no resultant and has an equivalent moment concerning any purpose. 

As the angle of attack is exaggerated up to 16o, the center of pressure bit by bit moves forward till it's but onethird of the chord from the leading edge; on top of this angle it begins to maneuver backwards once more. 

Now throughout flight, for reasons that we have a tendency to shall see later, the angle of attack is typically between 2o and 8o and is extremely seldom below 0o or on top of 16o . So, for the standard angles of flight, because the angle of attack of the surface is exaggerated, the centre of pressure tends to maneuver forward.