Fact Sheet #6
The Policy Origins of the X-33
December 22, 1999
A Joint Plan for Launcher Technology Development
The Access to Space Option 3 team also
included a plan for "maturing" and "developing" the required
technologies for a reusable single-stage-to-orbit rocket in their July 1993 report.
The task of identifying those technologies fell to the Option 3 technology assessment
subteam, led by Terry F. Greenwood of NASA's Marshall Space Flight Center. The "majority
of the critical enabling technologies," the July 1993 report read, "were
found to be common across three broadly based vehicle concepts." Those were
the three vehicle concepts studied in Option 3: a rocket-powered, single-stage-to-orbit
vehicle; a mixed airbreather-rocket single-stage-to-orbit vehicle; and a mixed airbreather-rocket
two-stage-to-orbit vehicle. Greenwood's subteam identified six fundamental technologies
required for all three vehicle architectures: 1) reusable cryogenic propellant tanks;
2) reusable liquid oxygen-liquid hydrogen propulsion; 3) vehicle health management
(hardware and software for auditing vehicle systems); 4) durable thermal protection
systems; 5) adaptive autonomous vehicle software and avionics; and 6) operable vehicle
subsystems. The Summary Report repeated the same technologies, but in somewhat more
concrete form: "graphite-composite reusable primary structures, aluminum-lithium
and graphite-composite reusable cryogenic propellant tanks, tri-propellant or lox-hydrogen
engines designed for robustness and operability, low-maintenance integral or standoff
thermal protection systems, autonomous flight control, vehicle health monitoring,
and a number of operations-enhancing technologies."
As proposed by the Option 3 team, these technologies would undergo development
and testing in both ground laboratories and on experimental (or "X") vehicles.
The Summary Report endorsed the same mix of flight and ground studies. Moreover,
the Summary Report advised, "technologies that interact should be tested together,
both on the ground and in the experimental vehicle." The "experimental
vehicle" also would serve "to validate the vehicle design models that are
used to predict the characteristics and performance of single-stage-to-orbit rocket
The Option 3 team also worked up a budget plan for their technology development
program. During an October 1993 briefing to the Office of Management and Budget (OMB),
Arnold Aldrich, head of NASA's Office of Space Systems Development, disclosed the
estimated cost of funding what now was known as the Access to Space Technology /
Demonstration Program. As the OMB learned, the total cost of the Access to Space
Technology / Demonstration Program from fiscal 1994 through 2000 would be $2.637
billion, with all but the first two years funded at $450 million annually. NASA and
the Pentagon would share equally in both the annual and total program costs.
The proposed cost-sharing with the Department of Defense reflected an ongoing
collaboration between NASA and the Pentagon in the development of launch systems,
such as the National Launch System (NLS) and the National AeroSpace Plane (NASP).
Nonetheless, already in 1992, NASA and the Air Force abandoned plans to work together
on the NLS, and the two agencies continued to conduct research together on NASP,
but the program had been scaled back to focus on suborbital tests of components.
As yet, the White House had no stated space policy. President Clinton had just
entered office in January 1993. The so-called Moorman Report, which led to the White
House decision to assign development of expendable launchers to the Defense Department
and development of reusable systems to NASA, came later, in May of 1994, and an interagency
review of launch vehicle led by Richard DalBello of the White House Office of Science
and Technology Policy was due on President Clinton's desk by January 1994. The White
House anticipated reaching a decision on whether to pursue a new launch vehicle sometime
Before the White House made any space policy decisions, however, NASA and the
Pentagon engaged in discussions over the possibility of jointly developing a single-stage-to-orbit
rocket. These discussions took place between NASA Administrator Dan Goldin and Air
Force Chief of Staff Gen. Merrill McPeak, as well as other Pentagon and NASA officials
during October and November of 1993. NASA viewed collaboration with the Defense Department
as a necessity in light of current budget reductions, according to Michael Lyons,
then NASA's deputy associate administrator for flight systems. As early as July 1993,
moreover, Merrill A. McPeak wrote a memorandum to two Pentagon officials regarding
the need to cooperate with NASA on space launch and propulsion technology. The Defense
Department, though, did not want to undertake another joint program. Instead, according
to Lyons, NASA proposed a cooperative arrangement, in which one agency would lead
the program and the other would provide technical support. This "cooperative
arrangement," however, did not mean the use of a cooperative agreement, a specific
In addition, NASA and the Pentagon disagreed on how big a new launcher needed
to be. The Air Force wanted a vehicle with a payload capacity of about 20,000 pounds
to low Earth orbit by 2005. This was the weight class of the vehicles investigated
in the Have Region study and the SSTO/SSRT program. NASA, however, was driven by
space station support and desired a vehicle large enough to carry 45,000 pounds to
orbit. Moreover, a single-stage rocket was unlikely to be ready by 2005, and the
two U.S. launch programs would be unaffordable in the current budget environment.
Still, the Pentagon sought to determine its launch needs. In 1993, shortly following
installation of the new President in January, the Pentagon conducted two major reviews
to appraise its launch and other needs. A sweeping inquiry that took place in April
and May reviewed launch needs and considered both expendable and reusable launchers,
while a six-month bottom-up review of spending priorities that ended in early September
1993 ruled out development of a new rocket by the Defense Department. John Deutch,
undersecretary of defense for acquisition and technology, led Defense Secretary Les
Aspin's bottoms-up review, which considered both expendable launchers and a reusable
single-stage rocket. In November 1993, though, it appeared that Aspin's decision
ruling out a new rocket for the Pentagon would not be the final word. On November
5, 1993, Deutch and other defense officials met with John Daily, NASA's acting deputy
administrator, to discuss possible collaboration on a new rocket and other efforts.
The policy question of collaboration between the defense and space agencies would
not be determined until the following year, as a consequence of the Moorman Report
and a White House policy decision that assigned NASA the responsibility for developing
reusable launch vehicles and the Pentagon the responsibility for developing expendable
These deliberations within the Defense Department, the discussions between NASA
and the Pentagon, and the White House's search for its own space policy formed the
ambiguous policy background to the Access to Space Technology / Demonstration Program.
That program, as we saw, involved technology development both on the ground and in
the air. In order to implement the program, the Option 3 July 1993 report recommended
that: "A team consisting of Option 3 members should continue to expand the understanding
of the advanced technology concepts through more detailed in-house studies. This
team should also assist in the formulation and advocacy of the recommended technology
program." Indeed, Gene Austin, Steve Cook, Roger Romans, and others at NASA's
Marshall Space Flight Center, and who had served on the Option 3 team, pushed the
Access to Space Technology / Demonstration Program.
They were supported in their effort by Thomas J. "Jack" Lee, whom Dan
Goldin appointed as his Special Assistant for Access to Space in January 1994. Even
before Lee transferred to Headquarters, though, Goldin saw Lee as critical to the
space agency's launch technology development efforts. "We definitely need to
address future launch issues and keep the heat on," Goldin told the November
29, 1993, meeting of senior staff and NASA center directors. "Aldrich [then
head of NASA's Office of Space Systems Development] and Lee are leading this effort,
which could result in a national leadership role for us."
Lee started his professional career in 1958 as an aeronautical research engineer
with the U.S. Army Ballistic missile Agency at Redstone Arsenal, Alabama. In 1960,
he transferred to the Marshall Space Flight Center as a systems engineer, and became
technical assistant to the technical deputy director of Marshall in 1969. After managing
various project offices, including Spacelab, starting in December 1980, Jack Lee
served as deputy director of Marshall until July 1989, when he was named director.
While at Headquarters, Jack Lee defined and coordinated the Access to Space Technology
/ Demonstration Program, which would take place at Marshall Space Flight Center.
These Headquarters efforts continued those he had been undertaking at Marshall
in the autumn of 1993. For example, in response to a request from Dan Goldin dated
October 8, 1993, Jack Lee described a program that "develops, demonstrates and
applies the [key] technologies to an SSTO flight demonstration vehicle." Lee
pointed out three "key technologies … essential for development of a single
stage to orbit (SSTO) launch system." These technologies were reusable cryogenic
fuel tanks, graphite composite structures, and a tri-propellant rocket engine. They
became the principal technologies studied in the ground portion of the Access to
Space Technology / Demonstration Program.
In writing to Goldin, Lee elaborated on the three technologies to be developed.
NASA needed to develop cryogenic tanks made of either aluminum-lithium or graphite
composite and which would last a long time and require minimal maintenance, he wrote.
The greatest advantage of aluminum-lithium over conventional aluminum in cryogenic
tank construction was a saving of 15 percent in mass. There were some disadvantages,
too. For example, aluminum-lithium cost was about five times higher, had a tendency
to delaminate, and required special shielding for welding All candidate aluminum-lithium
alloys, known commercially as Alcoa 2090, Alcan 8090, and Weldalite (Reynolds) 2195,
already were in use in such aerospace applications as the Atlas Centaur payload adapter
(Alcoa 2090), the Titan IV payload adapter (Alcan 8090), the Airbus A330/A340 leading
edges (Alcoa 2090 and Alcan 8090), the McDonnell Douglas C17 aft and fuselage, cargo
door, and deck (Alcoa 2090), and the Westland Agusta cabin frame and fuselage (Alcan
8090 and Alcoa 2090). The optimum tank alloy was considered to be Weldallite 2195.
Also under consideration were carbon fiber reinforced plastic (CFRP, a composite
material) tanks. CFRP could save 25 percent in mass over conventional aluminum tank
structures. It also had disadvantages. Those who worked with CFRP knew that its permeability
to hydrogen might increase each time it was refilled. Also, they had limited experience
with CFRP structures in contact with cryogenic hydrogen, which the NASP program still
needed to verify. Also, experts foresaw problems sealing end domes, access doors,
and the like.
Lee also explained to Goldin that primary structures, such as aeroshell sections,
made of graphite composite materials would reduce overall structural weight by 40
percent compared to the Shuttle structure, without corrosion or fatigue problems.
Actual transport aircraft with composite primary structures included the Boeing 777,
the Airbus A330 and A340, and the ATR 72. In addition, Lee wrote, NASA would study
both tri-propellant rocket engines and an upgraded Space Shuttle Main Engine (SSME)
for use on a single-stage-to-orbit vehicle.
The tri-propellant engine specifically under consideration was the RD-701 being
developed in Russia. Consideration of the RD-701 signified further NASA collaboration
with Russia following the end of the Cold War. Earlier in 1993, NASA had announced
that Russia would participate in the design and construction of the International
Space Station. The Russian RD-701 first used kerosene and liquid oxygen, then shifted
to liquid hydrogen and liquid oxygen. The engine, though, had yet to be test fired.
"It's still got a ways to go to be a real engine," explained Gene Austin.
Critical engine problems to be addressed included the tri-propellant injector and
the mechanism for shifting from kerosene to liquid hydrogen fuels.
More concrete detail of the proposed Access to Space Technology / Demonstration
Program came to light on October 19, 1993, when NASA officials briefed their counterparts
from the Pentagon's SSTO Review Team on it and the Access to Space Study. Richard
"Dick" Powell of NASA's Langley Research Center discussed a single-stage-to-orbit
vehicle concept studied at Langley and known as the SSV (Single-Stage Vehicle). The
SSV featured a bonded blanket thermal protection system, graphite composite wings
and other internal and external structures, and aluminum-lithium tanks for the liquid
hydrogen and oxygen fuel. Propelling the SSV was a set of seven evolved Space Shuttle
Main Engines or a grouping of three RD-701 engines.
Gene Austin briefed the same group on the proposed technology development and
demonstration program. He outlined the required technologies for a single-stage-to-orbit
vehicle: aluminum lithium cryogenic tanks, graphite composite primary structure,
and tri-propellant engines. "NASA, in partnership with industry and DoD [Department
of Defense]," Austin urged, "should initiate a focused SSTO Technology
maturation / demonstration program leading to a near term decision to develop a full
scale SSTO transportation system." In addition to the proposed ground-based
technology program, Austin wanted to test technologies on an experimental vehicle.
As the program's experimental "X" vehicle for flight testing, Austin proposed
his X-2000, which we saw in "The Flight Vehicle"
section of Fact Sheet 3.
The X-2000 Advanced Technology Demonstrator, named for the program's final year
of operation, was to be built entirely by the Marshall Space Flight Center. However,
Dan Goldin did not support the X-2000 project. As Goldin wrote to John H. Gibbons,
Assistant to the President for Science and Technology, in September 1993, regarding
launch technology development: "NASA does not have a plan to develop or release
any request for proposal for any launch vehicle, even as a technology demonstration.
We do have a desire, however, to ensure NASA is pursuing the technology needed by
the country in support of future launch vehicles." "With this in mind,"
he continued," it would be desirable to identify a wedge within NASA's budget
for a technology development effort that would be supportive of a program that might
be defined by the Working Group [on Space Transportation of the White House Office
of Science and Technology Policy] in concert with all affected agencies."