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)
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
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.
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 right way to 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 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.
Where do we go from here?
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
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
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
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.
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
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
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
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
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
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
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.