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Ada Flyer Ada Turns Science Fiction to Fact as It Flies DC-X at One-Tenth Cost

Buck Rogers had one notable advantage over the modern space program: His space ship was genuinely reusable; he didn't have to throw away most of it in the process of coming and going. Only recently has the space industry been catching up technologically with him. And Ada was the language used to show how to do it.

On August 18, 1993, science fiction came true for a small group of spectators at the U.S. Army's White Sands Missile Range, N.M. -- it was the maiden flight of the Delta Clipper Experimental (DC-X) single-stage rocket.

The DC-X launched vertically, hovered in mid-air at 150 feet, and began to move sideways at a dogtrot. After 350 feet, the onboard global-positioning satellite unit indicated that the DC-X was directly over its landing point. The spacecraft stopped mid-air again and, as the engines throttled back, began its successful vertical landing. Just like Buck Rogers.

As an officer said to the crowd at the maiden flight, "We are at the threshold of a new era, and you are at the doorway. To your front you're seeing the future. You're seeing a spaceport." A flight of 150 feet up, 350 feet over, and back down may not seem like going to Mars. But the DC-X had to overcome a lot more than distance. It had to show that a genuinely reusable launch vehicle could be developed quickly and economically, bringing together a large number of organizations and skills, and producing an aircraft that was both reliable and adaptable to changing circumstances.

The software tool to do just that was Ada.

For the Ada community, the important part about turning science fiction into scientific fact was using the right tool to do the job. That was shown when reports on the software schedule were released. The DC-X's software, which consisted of 65,000 lines of Ada code, had been developed at a tenth of the estimated cost, in a tenth of the estimated time.

The software had to operate 25 basic commands to fly the vehicle, including opening and closing the throttles and flaps, operating the thrusters, and gimbaling each engine about two axis. According to Chris Rosander, a senior manager at the primary contractor, McDonnell Douglas, the software's accelerated schedule and reduced budget were critical in keeping down the entire costs of the vehicle.

So, if NASA is successful in its current plans to make practical a commercially successful reusable launch vehicle, Americans be able to thank Ada for showing the way. Unfortunately, though, they won't be able to ride on the Clipper itself.

Human error
With eight flights under its belt, the DC-X was converted to the Delta Clipper-Experimental Advanced (DC-XA), and named the Clipper Graham in memory of Lt. Gen. Daniel O. Graham, an early proponent of economical space travel.

The next three flights went successfully. With a rapid turnaround of just 26 hours after the second of those flights, the Clipper Graham took its longest flight -- 20 minutes to go up two miles and return. After the next flight, however, the Clipper Graham was waylaid by something that happens in both fact and fiction: simple human error. For the DC-XA, it was a hose not connected properly. At White Sands on July 31, 1996, during its twelfth and final flight, the Clipper Graham's landing strut 2 failed to extend. The rocket tipped over on its landing pad. At least one tank exploded, and the ensuing fire damaged large sections of the DC-XA.

Facing current budget restraints, Gary Payton, Reusable Launch Vehicle program director, knew that new monies would not be forthcoming to repair the DC-XA and further its research. Nonetheless, he recognized the impressive accomplishments of the Clipper Graham. "Like any good experimental vehicle, the DC-XA flew until it was destroyed," he said. "We will always be impressed by the lessons this little rocket taught us about the right way to travel to the heavens..."

"The right way to travel"
The Strategic Defense Initiative Organization (SDIO, now the Ballistic Missile Defense Organization -- BMDO) originally funded the Clipper project for potential military applications. Its more futuristic and interesting purpose, however, was to bring space transportation to private consumers and corporations.

As the prime contractor, McDonnell Douglas Aerospace at Huntington Beach, Calif., developed, built, and flight-tested a DC-X, Single Stage to Orbit (SSTO) Program vehicle. (Over the years and under different organizations the program has also been called Single Stage Rocket Technology (SSRT) Program and the Reusable Launch Vehicle (RLV)).

With a dozen subcontractors, McDonnell Douglas produced the DC-X from scratch in 20 months on an SDIO contract for $60 million. It was considered a drop in the bucket to what technologically innovative rockets often cost. For example, nothing was allotted for research and development. The equipment and some software was off-the-shelf from NASA and other avionics companies' previous experiments. The engineers even bought parts from K-Mart.

In order to write the flight-control software at a low cost and with a quick turnaround, McDonnell Douglas used a prototyping model called the Rapid Prototyping and Integrated Design System (RAPIDS). Their efforts resulted in an operating software system in about 10 months.

To write the flight-control software, McDonnell Douglas used Integrated Systems, Inc. (ISI) and its design and analysis tool MATRIX. MATRIX includes the software-development tools SystemBuild, a modeling and simulation tool; AutoCode, a real-time code generator; and AC-100, a rapid prototyping system.

Each of the four people of the software team took charge of developing control algorithms, or modeling the aerodynamics and the flight-control processor and sensors, or generating and testing the code on simulation and real-time hardware. They were able to work on their own projects and then integrate them later using SystemBuild.

With RAPIDS, McDonnell Douglas was able to simulate the flight test software directly on the on-board processor, which Honeywell provided. The team modeled all the sensor-data and control functions within SystemBuild and automatically generated the real-time code through AutoCode. They could then target the code for the sensor model to the AC-100 and target the code representing the flight software to the flight processor, which was a space-qualified version of Intel's 80960 RISC. The closed-loop environment of the AC-100 and the flight processor allowed them to test the flight software. SystemBuild facilitated quick changes to any part of the flight-control system. In the final stage, the AC-100 was out of the loop and replaced with the real hardware.

McDonnell Douglas's other subcontractors and their projects included Aerojet (Rancho, Cordova, Calif.), for the reaction control system; Allied Signal Aerospace Co., Torrance, Calif., actuators and propulsion subsystems.; Chicago Bridge & Iron Services, Oak Brook, Ill., tanks; Deutsche Aerospace, Munich, Germany, landing gear; Douglas Aircraft Co., Long Beach, Calif., supportability and maintainability; Harris Corp., Melbourne, Fla., flight operations control center design and electronic components; Honeywell Space Systems Group, Clearwater, Fla., avionics; Martin Marietta Astronautics Group, Denver, Colo., ground support systems; Pratt & Whitney, West Palm Beach, Fla., main engines; and Scaled Composites, Mojave, Calif., aeroshell.

Where do we go from here?
The original Delta Clipper flew three times at the White Sands before SDIO terminated the program in late 1993. When the program found funding again in 1994, it flew another five flights before returning to McDonnell Douglas at Huntington Beach. The company then converted it into the DC-XA, which flew four flights at White Sands.

The Clipper Graham and the DC-X were prototypes for NASA's Reusable Launch Vehicle Technology Program. Future reusable vehicles that are larger and more advanced reusable will include the X-34 and X-33. (The 43-foot-tall Clipper Graham was one-third the size of SDIO's projected final reusable rocket.) The program's final goal was to create an SSTO reusable vehicle for space exploration.

But NASA, SDIO, and the Air Force are only part of the story.

The Reusable Launch Vehicle Technology Program was a partnership among NASA, the Air Force, and private industry to develop a new generation of SSTO launch vehicles. NASA invested $20 million for hardware and $30 million for integration in the DC-XA program.

The DC-X and DC-XA impressed the entire space travel community not just by how they flew or even how fast they got off the drawing board and into the air. The miracle lay in the same rocket being launched several times. The Delta Clipper, for example, demonstrated its reusability by being readied for reflight in seven days. In addition, its engines were test fired twice within eight hours.

As G. Harry Stine writes in his book, Halfway to Anywhere: Achieving America's Destiny in Space, "Every rocket-propelled vehicle that has flown into orbit as of 1995 has been totally or partially expendable. It has thrown away parts of itself as it climbed into space. Only the NASA space shuttle recovers parts for future re-use: the winged Orbiter and the two Solid Booster Rocket casings. Recovering and refurbishing these casings has turned out to be more expensive than throwing them away."

Being usable for only a single shot makes current space rockets and vehicles unprofitable and uninteresting for private investors. The DC-X changed rockets from being efforts that only governments could mount to becoming a viable research and development project for corporations. Its maiden flight was not mentioned in most of the government and avionics news journals. As Stine points out, however, it made news in another quarter: both Business Week and Barron's announced it beforehand on June 21, 1993.

Private industry is interested in part because of potential space or intercontinental travel in an SSTO vehicle. If developed under the economics, time frame, and capability of the DC-X and Clipper Graham, a trip on a reusable launch vehicle to anywhere on Earth for a 185-pound passenger might theoretically cost $5,000 in current U.S. dollars.

More important for contemporary corporations, however, is how a future viable SSTO vehicle would reduce the cost of payloads to space. Commercial aircraft operate routinely at fuel-cost ratios of U.S.$3 per pound If the Delta Clipper's pricing practice were consistent with commercial aircraft, then a fleet of DC-Xs could reduce launch costs to as low as $27 per pound. Under current development plans for the SSTO, the propellant cost of putting a pound of payload in orbit would be $9 per pound (with a 20,000-pound payload, and using liquid hydrogen and liquid oxygen propellant).

Even at $27 per pound, such costs would be dramatically less than the space industry currently faces. U.S. expendable launchers like the Atlas, Delta, and Titan generally cost about $3,000 to $8,000 per pound of payload put into low Earth orbit (LEO). Moreover, their failure rate is three percent, which is astronomically high when endangering human life or launching expensive satellites into orbit.

Meanwhile, unlike American funds for SSTO development, the international market for inexpensive payloads has not all but vaporized. Stine cites 15 commercial telecommunications companies that need 1,385 satellites in space within the decade. The demand exceeds the productivity of the entire world's combined reusable launch vehicle programs. However, many countries other than the U.S. are already profiting from inexpensive space launch vehicles. As Stine writes, "Europeans and Russians [are] building space trucks that are cost- and reliability-driven, durable, cheap, simple, rugged, easy to manufacture, and with wide performance tolerances."

In reaction to increasing demand, Congress restored monies to NASA for further investigation into its RLV program. The program to build the X-34 started up in March 1995 when NASA and Orbital Sciences Corp., Dulles, Va., signed a cooperative agreement to develop a small, reusable space booster. Its purpose is to reduce mission costs significantly for 1,000 to 2,000-pound payloads in low-Earth orbit. In this effort, NASA took an innovative approach to funding. Five of its centers will support Orbital Sciences Corp. and Rockwell International in the program. The two companies will invest $100 million with NASA's $70 million through a new, jointly owned company, American Space Lines.

On July 2, 1996, a contract for another Single-Stage-to-Orbit Reusable Launch Vehicle, the X-33, was awarded to Lockheed-Martin for its VentureStar model. NASA's Marshall Space Flight Center in Huntsville, Ala., awarded a $1 billion contract to Lockheed-Martin Skunk Works in Palmdale, Calif., through the year 2000. The company is to produce a sub-scale demonstrator vehicle to begin flying on March 1, 1999. (In the spring of 1997, NASA warned that the space vehicle might be heavier and slower than anticipated.)

Changing realities have not deterred NASA and Lockheed-Martin in their plan to prove the technological and economic feasibility of commercial space launches within the first decade of the next millennium. After NASA awarded the contract, the vice chairman and chief executive officer of Lockheed-Martin, Norman R. Augustine, said "Through the examples of the train, the automobile and the airplane, history has shown that, as costs of transportation come down, visionary business people think of new ways to harness commerce to technological innovations. They create new industries and new communities that generate jobs and prosperity for the future."

Those Buck Rogers who benefit in the future from commercial space transporation will have good reason to thank Ada, both for reducing the cost and time of developing flight controls and for laying the groundwork for the new businesses that are sure to evolve around cheap space transportation.

Copyright 1998. IIT Research Institute
All rights assigned to the US Government (Ada Joint Program Office). Permission to reprint this flyer, in whole or in part, is granted, provided the AdaIC is acknowledged as the source.
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