V. Where the United States Stands Today in Terms of Commercial Spaceflight Passenger Transport
A. The importance of airworthiness-certified passenger spaceflight systems
Explorers explore and settlers settle. Consequently, exploration and settlement each have their own rules for safety. The early stages of space settlement will occur as the space industrial revolution unfolds. For space settlement to proceed, an acceptable level of operational safety must be achieved. This means that human operations in this new frontier will undergo a paradigm shift in safety from the higher level of risk inherent in exploration to the low level of risk associated with and expected for normal living activities.
Passenger transport safety highlights this distinction. Legally a passenger is a person who has hired a business to transport him or her to a destination by paying a fare. When hiring the business, the passenger surrenders the responsibility for his or her safety to the business owners and operators. In accepting the fare for the transportation, the business also accepts a “duty to care” obligation for the passenger’s safety. If the business owner or operator is negligent and harm comes to the passenger, then the owner or operator may be sued to recover damages. If the negligence is severe, then criminal charges may also be brought. The duty to care obligation is part of common law, indicating that this is a normally expected legal obligation that the owner and operators accept when the business begins to operate.
Starting in the 1800s, as steamboats and railroads became a common form of passenger transportation, the increasing mechanical complexity of the systems exceeded the ability of the passengers to ascertain their safety by normal visual inspection. This was especially true for components such as the boilers, brakes, rails, and bridges, whose proper functioning were critical to safety. Regulation, independent inspection, and certification became the way the duty to care obligation was met. Regulations, usually involving design and manufacturing standards, were implemented by law, as were inspections by qualified independent experts. When the system being inspected was found to comply with the regulations, a certificate was issued. This protected the owners from unwarranted lawsuits claiming negligence and provided the basis for allowing the business to operate with the public’s confidence.
For commercial aircraft, airworthiness certification is used to meet the duty to care obligation. This involves two parts. First, a new aircraft design or type must be shown by analysis, inspection, and ground and flight test to be safe—to be airworthy. This necessarily involves building and flying prototype and early production aircraft of the new type. When the new design is demonstrated to be airworthy, a “type certificate” is issued, freezing the design. Then the new design goes into serial production. Each production aircraft is (a) individually inspected to show that it was built per the approved design and (b) ground and flight tested to demonstrate that it was properly built—the controls work, all the cables are properly connected, the software is loaded correctly, the landing gear retracts and extends, etc. When this is demonstrated, each individual aircraft is issued an airworthiness certificate giving the owner who buys the aircraft the legal ability to transport passengers on that particular aircraft. Only then does that aircraft enter service and begin to carry passengers.
Undertaking the airworthiness certification process, while required by law, also demonstrates the builder’s commitment to passenger safety as this is a carefully regulated process. Having the airworthiness certification process enables the builder to demonstrate the safety of the new design in a manner that the public accepts as being adequate to protect safety reasonably. Having an airworthiness certificate for each operational system—and maintaining it through proper inspections, maintenance, and repairs—enables the operator to demonstrate that its duty to care obligation is being met.
The key to making the airworthiness process work is that it is regulating fully reusable flight systems. Prototype and early production aircraft must be flown repeatedly to gather flight test data to support the type certificate. Each production aircraft must be test flown prior to receiving its airworthiness certificate and entering passenger service. This same safety-assurance rationale carries over into all other forms of passenger transport—certify, then operate. And, of course, this certification process cannot be applied to an expendable or partially expendable flight system, which is why public transportation systems are not expendable or partially expendable.
Obviously, for the commercial transportation of passengers to and from earth orbit and within the Earth-Moon system, only fully reusable flight systems will be able to be used in order to achieve the airworthiness certification necessary to meet the operator’s duty to care obligation. Hence, to open space to commercial human operations, fully reusable spaceflight systems need to be developed, type certified, and, then, have each operational system be airworthiness certified before becoming operational. Current or planned human expendable or partially expendable spaceflight systems cannot be airworthiness certified and are, therefore, not useable for passenger transportation.
It is important to differentiate a certificated fully reusable space access system from the “reusable” concept of recovering and reusing a stage or major component, such as the engines, of an otherwise expendable launch vehicle. If any normal fight safety components of the flight system are expendable, then the system cannot be certified. Hence, reusing a recovered component is an economic choice only. While this may be important for decreasing the overall launch costs for these expendable systems, simply being reusable, but without formal airworthiness certification, says nothing about the safety of the system.
B. America’s interest in fully reusable space access dates back to the 1950s
The American dream to become a true human spacefaring nation has been widely evident with the American public since the mid-1950s, when Wernher von Braun, in cooperation with Walt Disney, introduced this spacefaring future to the public. Von Braun, an early pioneer in expendable rockets, understood the need to move to a more conventional logistics infrastructure. His view of the future involved reusable space access systems, orbiting space stations, and reusable spaceships to reach the Moon.
By the late 1950s, stimulated by Sputnik and the initial race to launch orbiting satellites, the American dream of human spaceflight evolved into operational intent within the US Government. The US Air Force started a number of programs, including the original aerospaceplane studies for fully reusable, single- and two-stage space access systems, the hypersonic X-planes to explore the aerothermal environment of hypersonic flight (e.g., the X-15), and the orbital manned reusable spaceplane, DynaSoar (X-20). When President Kennedy made his fateful decision to pursue expendable launch vehicles and space capsules to beat the Soviets to the Moon in the civilian space race, progress in the development of more aircraft-like reusable operational capabilities continued through military R&D. Even after the military’s DynaSoar program was cancelled in 1963, largely due to the rapid maturation of military surveillance satellite technologies and ballistic missiles, significant research continued into lifting body designs, advanced materials and structures, and advanced propulsion.
The second opportunity to pursue the spacefaring path began with the start of the Space Transportation System, better known by its popular name, the Space Shuttle. As the name implies, it was originally intended to provide frequent and routine civil access to LEO. It was conceived in the early 1970s as a fully reusable, two-stage system design to be used in conjunction with an orbiting space station—reflecting the common sense fact that a reusable space access system needs someplace to go to in orbit in order to deliver passengers and cargo. Unfortunately, by 1972, politics and funding constraints changed this into the partially expendable system that we know as the Space Shuttle. Also, the space station was dropped. Safety concerns were addressed by presuming that production and pre-flight quality control of the expendable components would suffice. These changes subverted its original mission goal to operate frequently and routinely, with airline-like safety, because each new flight required the untested use of new and rebuilt components—the external tank and the solid rocket boosters.
Over the course of its 30 years of operation, the Space Shuttle only flew 135 times while unfortunately having two catastrophic failures with loss of crew—failures originating in the new/rebuilt expendable components. Thus, the proven risk of mission failure was about 1:60—far, far less than what is acceptable for public transportation. Expendability prevents knowing for certain that a system is safe to operate prior to being used in regular service. This elevates the risk substantially, making this form of space travel unacceptable for spaceflight passengers.
C. The US aerospace industry has been able to build fully reusable space access systems since the 1980s
This engineering common sense need for full reusability in space access was recognized in the 1950s. The first aerospaceplane design studies, started in the late 1950s, were focused on trying to find a fully reusable technological solution to space access. After the Apollo program—and its use of expendables as a politically expedient way of beating the Soviet Union—the focus returned to fully reusable space access when the Space Shuttle requirements were initially defined. It was intended to be a fully reusable, two-stage-to-orbit (TSTO) spaceflight system with airline-like operations. This was a very ambitious objective given the fact that the entire preceding operational and industrial experience was with high-risk expendable launch systems. The requisite political support for the funding necessary to substantially advance the state of the art in a system development program did not exist. The political compromise of the partially expendable Shuttle, with a much larger capacity to accommodate military payloads, was implemented.
With the decision to not pursue full reusability with NASA’s Space Shuttle, the pursuit of this approach returned to the military. At the same time the Space Shuttle was about to begin flight operations in the early 1980s, the US Air Force was evaluating military applications of fully reusable military aerospaceplanes. There was common agreement that, to be operationally effective, the system had to be aircraft-like and not some version of an expendable launch vehicle. This moved the intended user of the system from the launch community to the aircraft operations community, meaning that the system would be based at airfields and not at launch facilities. For this reason, the concept studies focused on horizontal takeoff and landing approaches on runways using quasi-single-stage-to-orbit (SSTO) and TSTO systems. A new name was invented—TransAtmospheric Vehicle (TAV)—to separate this concept politically from NASA’s Space Shuttle and the military’s expendable launch vehicles (ELV). Multiple concepts were studied under contract. A baseline study objective was to define concepts employing 1980s technologies so that a formal program start decision could be pursued.
In 1985, at the conclusion of the TAV conceptual design evaluation, the Air Force decided not to pursue gaining Department of Defense approval to start the formal engineering and manufacturing development of a TAV military system. This decision was based on changing mission needs and funding priorities. Instead, attention turned to developing a revolutionary airbreathing propulsion solution for an SSTO approach. The TAV decision was not a decision based on a determination of inadequate technology or inadequate industrial readiness needed to proceed into formal system development. What the TAV studies showed was that since the start of the Space Shuttle development in the early 1970s, the US aerospace industry had acquired the necessary industrial capability to begin the development of fully reusable, two-stage, rocket-powered space access systems with acceptable program risk.
For the future of the American human spaceflight program, the failure to proceed with the TAV development was another fateful decision, just as was the decision not to pursue full reusability for the Space Shuttle. The military’s development of new flight technologies and systems generally precedes commercial adoption, because this provides a proven path to overcome the inevitable technical obstacles and achieve the necessary technical and operational maturity necessary to enable commercial operations. The Air Force’s KC-135 jet tanker, developed in the early 1950s by Boeing, gave rise to Boeing’s B-707 commercial jet airliner that helped to jumpstart the commercial aviation industry in the late 1950s. The same has been true for advanced materials and structures, engines, digital flight controls, etc.
Had the TAV program been pursued, a military TAV TSTO system would have likely become operational by the late 1990s. This would have opened the door to commercial TSTO derivatives, especially given the 1986 Space Shuttle Challenger failure that exposed the substantial safety and operational inadequacies of the entire US space access infrastructure. A civilian passenger version of such a TSTO TAV system could easily have transported 20 or more passengers to LEO. A civilian cargo version could have transported medium-sized payloads. Think of the impact this would have had on the course of US manned space operations, both civil and commercial, versus where the American human space program stand’s today.
It is very important to recognize that from the mid-1980s, America’s commercial aerospace industry had signaled that it had the capability to develop fully reusable space access systems—most likely TSTO systems. Yet, for more than a generation, normal commercial market forces/constraints have prevented industry from pursuing this approach, even when the termination of the Space Shuttle and the consequences of this became apparent. Hence, there is a clear need for an effective public-private partnership to initiate this capability as industry will not do this itself.
Within months of the decision not to pursue the military’s TSTO TAV, the Federal Government instead chose to pursue the goal of demonstrating a fully reusable SSTO system capable of taking off and landing on a runway. This became the National Aerospace Plane (NASP/X-30) program as part of a national effort to reinvigorate aerospace science and engineering. The technical path chosen was to maximize the use of airbreathing propulsion, employing scramjets capable of operating to Mach 12 and above.
To put this into perspective, the NASP program was initiated in 1985 when the first personal computers were just becoming available. A typical laptop PC today has more computing power than the supercomputers of that time. While exciting, NASP was the point where the nation’s intended reach exceeded its technical grasp. While the US aerospace industry had the technical ability to execute a rocket-powered TSTO system development with acceptable risk, the X-30 SSTO program was very high risk. This became quite evident by the end of the 1980s as the projected gross takeoff weight of the flight system grew substantially as design closure—the predicted ability to achieve orbit—became increasingly uncertain.
Consequently, with the NASP program floundering, with the military’s TAV not being pursued, with the military doubling-down on ELVs in the wake of the Challenger failure in 1986 and not seeing any need for human military operations in space, and with NASA doubling-down on the Space Shuttle after the Challenger failure, the US aerospace industry began to dismantle its then-impressive manned fully reusable spaceflight development capabilities. The practical reason was that there was no likely near-term return on their investments to be prepared for a government development contract for a fully reusable system.
The final fling at SSTO was the ill-conceived X-33 program in the 1990s. This started as a follow-on to the earlier rocket-powered studies that produced the Boeing RASV concept in the 1970s. In the 1980s, the military began to address the need for ballistic missile defense seriously. Placing platforms into Earth orbit to detect, track, and destroy launched ballistic missiles was one approach being considered. For this to be practical, the means to place military payloads into orbit at costs substantially lower than ELVs was needed. Drawing on efforts originating in the 1970s, an all-rocket, vertical-takeoff and vertical-landing (VTVL), subscale demonstrator program was proposed. Focusing on demonstrating VTVL capability and aircraft-like reusability, the Delta Clipper Experimental (DC-X) effort was started in 1991 under contract to the military. The 39-foot tall, 42,000 pound, unmanned, fully reusable DC-X experimental vehicle made eight test flights, demonstrating that such rocket-powered systems could be built and operated. As the first phase of the DC-X program ended with several successful fully reusable flights, a 1995 revision to the National Space Transportation Policy placed responsibility for developing fully reusable space access capabilities under NASA. Once again, the military, even though making significant progress, was taken out of the picture by national political priorities.
This policy change placed developing fully reusable space access into political conflict with NASA’s jobs- and budget-heavy “800-pound gorilla” called the Space Shuttle. If the fully reusable space access approach had become successful, then the Shuttle program would have ended. The only political path forward for the fully reusable approach was to try again for an SSTO solution. Such a technically demanding approach would protect its development funding in the budget process, because politicians would view the potential of it really threatening the Shuttle program as very unlikely.
Like the NASP program before, the guiding national policy was flawed in that preference was given to the Space Shuttle and ELVs. The common sense next step of developing a fully reusable TSTO system, even as a demonstrator to prepare for the future, was pushed aside in favor of another high-risk, but politically safe, SSTO approach. What was most unfortunate with the X-33 program was that it did not reach flight testing because an inadequate technical design was selected from the competing designs. (The design selected was not from the company that had done the DC-X effort.) Even if the X-33 had not reached orbit, the technical information gained would have been very useful for future programs. Unfortunately, the X-33 program was cancelled after the propellant tank’s ground structural test article failed prematurely, casting doubt on the overall airframe design approach, since the SSTO airframe is essentially a large propellant tank.
The one good aspect of these past 30 years has been the growing competence of the US aerospace industry in on-orbit operations. The International Space Station (ISS) program has kept this segment of the industry engaged developing capabilities that will now be needed to undertake building the LEO component of the integrated spacefaring logistics infrastructure. However, manned space access of the type needed by a true human spacefaring nation has been withering for over a generation and this must be rebuilt.