From DC3 to DCX

Aviation, from an operational standpoint, did not take off overnight. Even though the Wright brothers flew their Flyer I no less than four times that first day at Kitty Hawk, it was many years before the general public was willing to risk their necks in the new flying machines. Only after Charles Lindbergh, in the Spirit of St. Louis, demonstrated that it was possible to fly nonstop across the Atlantic, did general

Fig. 9.2 The Space Shuttle on its mobile launch platform and crawler-transporter, inching its way toward the launchpad. The Shuttle carries virtually all its propellants in an external liquid fuel tank and two solid rocket boosters (courtesy NASA)

aviation take off in earnest. By that time, the days of the biplane (Fig. 9.3) were essentially over. Powerful new engines had been developed, and they were being mounted on the new airplanes in two's and three's (Fig. 9.5) . This factor alone assured the public that it was time to climb aboard. One of these early passenger-carrying airplanes was the Ford Tri-Motor, which had three radial engines and carried ten passengers. Several of these lumbering early-birds are still flying, and appear at places such as the yearly EAA fly-in at Oshkosh, Wisconsin. But they were slow, cramped, and inefficient on both the engineer's and the economist's tally sheet. Something bigger, faster, and better was needed (Fig. 9.4).

Fig. 9.3 Still in the biplane era, the Vought VE-7 was a necessary step on the long road toward the spaceplane. NACA test pilot Paul King dons warm clothing and oxygen mask just before high-altitude test flight in October 1925 (courtesy NASA)

The time was right for the first airliner, the twin-engine Douglas DC-3. Though small by today's standards, it was the perfect airplane for its era, and it quickly proved its value in hauling not only passengers but cargo as well. It became, arguably, the first operationally efficient, profit-motive driven airplane in the history of aviation. These aircraft were built by the thousands, with hundreds still flying to this day. They were even used by the Army air forces during World War II, serving with distinction as the celebrated C-47 Gooney Bird. The famous Berlin airlift used many of these useful aircraft. But what does the ancient history of aviation have to do with the advanced spaceplanes of the future?

Fig. 9.4 The Vega Air Express, with NACA-designed cowling, broke the transcontinental speed record in 1929 (courtesy NASA)

Fig. 9.5 Twin-engine aircraft greatly increased the range and reliability of airplanes in the years before and during World War II. Mercury astronaut Donald K. "Deke" Slayton (right) and Ed Steinman (both 1st Lieutenants) pose with their Douglas A-26 bomber in 1945. Astronaut Slayton later took part in the Apollo-Soyuz Test Project in July 1975 (courtesy NASA)

Fig. 9.5 Twin-engine aircraft greatly increased the range and reliability of airplanes in the years before and during World War II. Mercury astronaut Donald K. "Deke" Slayton (right) and Ed Steinman (both 1st Lieutenants) pose with their Douglas A-26 bomber in 1945. Astronaut Slayton later took part in the Apollo-Soyuz Test Project in July 1975 (courtesy NASA)

It actually has a lot to do with it, because until airplanes became operationally efficient, they never appeared in large numbers. And until they appeared in large numbers, they did not have a chance of becoming economically operational. The key was people - thousands of fare-paying passengers who simply wanted to go. If they had the money, and enough of them obviously did, then they could get to ride in style on one of the sleekest, fastest ships then available - the DC-3. These airplanes - these ships of the sky - even had captains and flight crews, something which has held over to the modern day. Not everyone, of course, could afford to pay the ticket price, and only the well-to-do took to the skies in the early years. And so it will be with the first spaceplanes.

The DC-3's operational success was linked to its versatility, its reliability, its safety, and of course, its reusability. Every successful passenger airplane since then has taken its cue from this venerable old maiden of the skies. This cannot be said of the DC-X Delta Clipper, which was to have taken this legacy beyond the skies.

The DC-X was one of the first single-stage-to-orbit VTVL testbeds ever flown. And fly it did, though it never flew in space. It was basically an Earth version of the Apollo Lunar Module, without a crew. It could take off, hover, fly horizontally some distance, land on its four legs, and do it all using rocket power alone. One of its remote control pilots was Charles "Pete" Conrad, Commander of Apollo 12 and the third man to walk on the Moon. On the last flight of the much ballyhooed Delta Clipper, it tipped over and blew up. And that was that. There are plenty of reasons why this happened, including lack of funding, an overworked ground crew, and so on. But the fact remains that according to Murphy's Law, if something can tip over, it will tip over. In the case of the DC-X, one of its landing gear failed to extend at touchdown because of an unattached hydraulic line. Although it had flown perfectly, and its other three legs had deployed as they should, this one little glitch was enough to doom the top-heavy craft. Toppling to the ground, the remaining onboard propellants immediately ignited, and the spacecraft was destroyed in a blazing instant.

What lessons are involved in this comparison of DC-3 to DC-X? There are many lessons, some so simple that they would tend to be ignored completely. Two of these cannot be ignored here, however. The first lesson is that piloted machines are inherently safer than unpiloted ones. Every DC-3 had a flight crew. If the DC-X had a pilot, you can be sure he or she would have checked the landing gear before taking off. This is normal operating procedure. Pilots are trained never to fly an unsafe craft. The second lesson is that it is very unwise to fly a machine that may tip over, especially if tipping over means blowing up. Airplanes cannot tip over, because they have wings sticking out on both sides. Even if a landing gear collapses completely, the airplane merely tilts a little and slumps to the tarmac (Fig. 9.7). Simple, but who would think of it? Who would speak of it? It is a silly thing, a simple thing, but it is true. Airplanes do not tip over! And neither will spaceplanes.

Before we get into the what, the why, and the how of the advanced spaceplane, it is convenient at this juncture to note that one of the reasons the X-33 program was canceled was because of the concerns of flying unpiloted craft over the continental United States. The X-33 was to have tested the new linear aerospike rocket

Fig. 9.6 Douglas D-558-2 Skyrocket in flight with F-86 chase plane, during the mid-1950s. The post-war years saw a rapid and continual improvement in airplane and rocketplane designs, exemplified here by the recently introduced swept wings of both aircraft (courtesy NASA)

Fig. 9.7 Rocketplanes might trip up, but they do not tip over. Here, the nose gear of the X-1E has collapsed on landing at Rogers Dry Lake in June 1956. The research aircraft was easily repaired to fly again. See also Fig. 2.5 (courtesy NASA)

engines on suborbital trajectories, lifting off from the American southwest and landing on runways in Nevada and Montana. But the specter of one of these unmanned vehicles crashing - and causing loss of life or injury to those on the ground - was too great. This ultimately contributed to the cancellation of X-33 and its follow-on project, VentureStar (see Fig. 9.8).

Fig. 9.8 The X-34 Technology Testbed Demonstrator spaceplane parked on the ramp at Dryden Flight Research Center, California. Like the X-33, this promising program was also unfortunately canceled (courtesy NASA)

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