From: House Committee on Science, Space, and Technology
Posted: Saturday, May 10, 2003
Michael D. Griffin
Hearing on the NASA Orbital Space Plane Program
Subcommitee on Space and Aeronautics
Committee on Science
Rayburn House Office Building
8 May 2003
Requirements for NASA's proposed Orbital Space Plane (OSP) and its place in the new Integrated Space Technology Plan (ISTP) are discussed. Consideration and adoption of appropriate top-level goals for the nation's space transportation architecture is advocated. The role of OSP relative to the Space Shuttle in support of International Space Station (ISS) is treated. Key OSP design features, especially the issue of a winged vs. semiballistic vehicle design, are discussed. OSP programmatic assumptions are examined, with attention to cost, schedule, and technology development requirements.
Thank you for inviting me to appear before this committee to discuss this most important issue, that of the NASA Orbital Space Plane (OSP) program, and its relationship to the new NASA Integrated Space Transportation Plan (ISTP).
I will open by noting that, in my opinion, this is not only a most important topic for discussion, it is the single most important subject to be addressed by the nation's leaders in connection with our nation's future in astronautics.
In aeronautics, the air is merely a medium through which one must transit in order to reach a desired destination. In astronautics, both air and space become navigable media, but space also becomes much more: It is itself a destination, a region offering access to an enhanced vantage point, hard vacuum, microgravity, advantageous positioning, and new sources of energy and materials.
But to use these assets we must first reach the destination. The physics of Earth's gravity well are such that once we reach low Earth orbit (LEO) we are, in Arthur C. Clarke's famous turn of phrase, "halfway to anywhere". This hearing, one of many such discussions on the topic, is prima facie evidence that despite the passage of sixty years since the invention of the first vehicles capable of reaching space, the task of reaching LEO -- reliably, routinely, and cost-effectively -- continues to elude us. We are still having trouble taking Clarke's first half-step.
The task is difficult. To reach LEO, we must package the energy required for an intercontinental aircraft flight in a container with the volumetric efficiency of an eggshell, yet which is tough enough to withstand high inertial, thermal, and aerodynamic loads. The stored energy must be expended within a few minutes, and prevented from being expended in a few seconds. Each launch of an expendable vehicle is its maiden flight, an event performed under only the most carefully controlled and limited conditions in aeronautics, yet which in astronautics must be a maximum-performance event. A reusable vehicle must survive a return through an atmospheric flight regime so rigorous it cannot be simulated in even the highest performance wind tunnels; such a vehicle can be fully tested only by flying it "for real".
But while the task is difficult, we have allowed ourselves to make it more difficult than it need be. We have sometimes concentrated so heavily on particular details and "point designs" that we have failed to appreciate that each such design must blend into, and be part of, a broader architecture. We have sometimes become enamored of specific requirements, to the exclusion of broader goals. We have at times over-valued the role of government while failing to pay due attention to the skill and expertise residing in our industrial base. At other times we have done the opposite, leaving too much to the discretion of contractors who, after all, bear no final responsibility for the success or failure of any government enterprise. In some cases we have stayed too long with proven but inefficient technology. In other cases we have designated as "operational" those things which were, at best, operating at the very edge of the state of the art, and possibly beyond it. We accept, without serious objection, a "cost of doing business" in government space endeavors that should shame us all were it to be examined on any sort of rational basis.
We have made most of the mistakes that can be made, mistakes which would have put any commercial enterprise mercifully out of its misery, in favor of a competitor with a better approach. But because the development of space launch vehicles has been almost exclusively a government enterprise, and because the few and only competitors have been other governments, normal market mechanisms are absent, and we continue to muddle along. This does not mean that all of our problems would be solved if we merely turned space launch over to industry, and restricted the government's role to supervising the purchase of tonnage per year to orbit. The contrary fact is true; the government's role in sponsoring appropriate technology and systems development is crucial, if effective launch vehicle technologies and an efficient free market in space transportation are ever to exist. We simply need to do it better than we have so far demonstrated.
In the wake of the Columbia accident, some have argued for restricting, once again, the frequency and purposes of manned spaceflight, or of restricting shuttle launches to orbits compatible with the International Space Station (ISS). One hears it said that manned spaceflight should be restricted to those occasions when human presence is "needed". I cringe when I hear or read such views. Since there was no human spaceflight at all prior to 1961, it is plain to see that we do not "need" to do it. We do it from a fundamental desire, inherent in our genes and in our culture, to explore our environment and expand our presence within that environment. We do it, according to John F. Kennedy's ringing quote, "not because it is easy, but because it is hard". Bearing this in mind, I submit that NASA's role is not to figure out how to do less manned spaceflight; NASA's role is to figure out how to do more of it.
With these thoughts in mind, I offer the following in response to the questions posed by this committee in its formal invitation to appear.
- What key factors should be considered when evaluating human space transportation architectures? Is the proposed ISTP an overly optimistic or overly conservative approach to meeting NASA's needs? What areas of the proposed approach pose the greatest risk? What recommendations do you have to reduce these risks?
The key element of any system architecture is that it be responsive to an overarching framework of goals. When a system architecture - or a specific vehicle - is designed without reference to such top-level goals, the result is a point design that is unlikely to blend smoothly into any larger picture. Rather than being designed to meet a higher purpose, the purpose becomes merely that set of tasks the system can accomplish.
The proposed ISTP seems to lack the required global framework, the desired broader view. Three elements are specified - the Space Shuttle, a new Orbital Space Plane, and a reusable launch vehicle. This latter element, potentially the most important of the three, is hardly a factor in the present discussion because it is being deferred for some unspecified period. What, then, are the questions being asked, for which these three architectural elements are the answers? This discussion is nowhere to be found in the proposed ISTP.
NASA should lead the debate to define and enunciate the nation's goals in space, and following from them, our goals in the development of space transportation - goals which will guide us for at least a generation. These goals should be embraced within the Administration, and shared and supported by the Congress, for in this matter there is no conceivable partisan interest. Properly chosen goals will be shared by the majority of informed stakeholders, and will be broad enough to accommodate the flexibility of timing and funding that future Administrations and Congresses will need and want, without sacrificing their essence.
While others may certainly have their own ideas as to the appropriate goals for the nation in space transportation, I believe they should include at least the following:
-Robust and economical small, medium, large, and heavy lift capability to LEO, to the 100 metric ton level or greater.
-Dependable, available crew transport to and from LEO.
-Crew escape capability from ISS and other space stations yet to be built in other places.
-Reliable cargo transport to LEO, including the capability for automated rendezvous, proximity operations, and docking with pre-existing assets.
-The option, but not the requirement, to combine crew and cargo transport as needed for a particular mission.
-LEO-to-higher-orbit transfer capability.
-Efficient lunar and interplanetary transfer capability for both unmanned and manned missions.
If I may be permitted an imperfect but possibly useful analogy, NASA is the entity in the U.S. government charged with, and best suited to, creating the "interstate highway" to space. This highway needs to be designed to handle shipments both large and small, on known and reliable schedules, safely and economically. The highway is needed because the existing patchwork of separately developed roads is inadequate to serve the future we can envision. Industry can and must share in the design, and must perform the actual construction. But only NASA can enunciate the goals and architect the system.
Against this larger backdrop, the proposed ISTP can only be seen as far too conservative. It is not so much wrong, as it is incomplete. If fully realized, it would leave us with little more capability than we have today to go beyond Earth orbit. It would do nothing soon to reduce the cost of space access. It would saddle us for the next two decades with continued primary reliance on the Shuttle, which is by any reasoned measure the riskiest element in the system. Surely we can do better.
- How might the OSP alter NASA's reliance on, and the flight rate of, the Space Shuttle? Should crew and cargo delivery be addressed by separate systems? If the OSP and a separate cargo delivery capability for logistics re-supply were developed, would it be necessary to continue to fly the Space Shuttle? If so, what missions could not be accomplished without the Space Shuttle? If the Shuttle is required for the duration of the Space Station, is an OSP that performs both crew rescue and crew transportation required?
Given the existing Level 1 requirements and their interpretation, the OSP is unlikely to alter substantially NASA's reliance on the Space Shuttle.
The OSP program is specified solely in terms of its requirements to "support" the International Space Station (ISS), where "support" is defined as "supplementing" the existing capabilities of Shuttle and Soyuz. It must support ISS crew rotation on 4-6 month intervals, and system is to be designed to have minimum life-cycle cost. These constraining assumptions, offered without reference to a set of higher goals such as articulated above, will have profound consequences in the generation to come. To see where these assumptions can lead, let us consider the following train of thought.
If the purpose of OSP is to "support" ISS operations by "supplementing" the capabilities of the Shuttle, and ignoring Soyuz for the moment, then clearly the Shuttle must be kept flying, in accordance with the proposed ISTP. Estimates vary, but it is accepted that a viable Shuttle program requires a minimum of several - let us say three or four - launches per year. Thus, in the normal course of events, Shuttle alone can easily accommodate ISS requirements. OSP would then fly only a couple of times per year - if that - to maintain operational currency, or to rotate the vehicle(s) docked at ISS for purposes of emergency crew return. Under these assumptions, OSP is thus needed only when - as at present - the Shuttle is grounded. The OSP system thus needs to be designed to accommodate a peak rate of possibly four flights per year for short periods, and much less on average.
With such assumptions, it will be almost guaranteed that the lowest-life-cycle-cost design is a simple (probably expendable) vehicle with the least capability consistent with completing the tasks envisioned today. A basic semiballistic capsule designed for a few days of independent flight could easily suffice. By choosing this path - and it is inevitable if we accept the Level 1 OSP requirements as written - we accept the requirement to maintain the inherently high cost Shuttle program. Worse, we have as our only Earth-to-LEO transportation systems two designs (Shuttle and OSP) which are wholly incapable of being adapted to the needs of lunar return or Mars exploration, ventures which should certainly be of interest over the intended design life of the OSP. Considered in such a broader context, radically different design choices might be made for OSP. But they are not possible given the requirements as written.
It scarcely needs to be said that it will be extremely hard to justify the development of such a vehicle, at a cost of several billion dollars, for such a limited purpose as OSP will have, given the requirements envisioned for it today. And, indeed, such development makes little sense economically. One could likely obtain several replacement Shuttle orbiters in a "block buy" for the same cost as a new OSP. Further thought in this direction would likely show that the most economical crew return vehicle for ISS would be the Shuttle itself - modified for a 60-to-90 day stay - with four to six crew rotation missions peryear. Following this logic, it becomes difficult to see the path by which reliance on the Shuttle can be ended.
To me, the likeliest result of accepting the OSP Level 1 requirements as written is that a sober analysis will show the OSP to be wholly unjustifiable in economic terms, and the program will subsequently be cancelled in favor of continued use of the Shuttle. Since the Shuttle is not capable of supporting the larger goals that I have enunciated above, or any similarly broad set of goals, I would consider this outcome to be another setback for NASA and the nation.
With regard to separation of crew and cargo, the issue is not "should" they be separated, but "can" they be separated when it is advantageous to do so, as is so often the case. With the Shuttle, they cannot. While the Shuttle's large cargo bay is its most impressive feature, it is also the feature which, in my opinion, results in the greatest increment of risk to the astronauts who fly it. With the cargo bay attached to the crew cabin, the Shuttle orbiter is inherently so large that only a sidemount configuration is possible, leaving the crew with no escape path in the event of a launch malfunction, as with the Challenger failure, and vulnerable to falling debris, possibly including ice, as with the Columbia accident.
If the Shuttle system had been designed with a smaller manned vehicle atop an expendable cargo pod, the overall system would have been much safer. A simple escape rocket would have sufficed to separate the crew vehicle from the launch system in the event of a malfunction, which is of course ultimately inevitable, given a sufficient number of flights. The crew vehicle could have been launched, by itself, on a smaller vehicle or vehicles when no cargo was required. The only lost capability would have been the ability to handle "down cargo", the least-used feature of the Shuttle system. My own view on the value of "down cargo" is somewhat simplistic: It is so difficult and expensive to get payloads to space that, having done it, we ought by and large to leave them there, and design them for that! But, if necessary, I believe that the design of a reusable cargo pod capable of executing an autonomous reentry and landing would pose little challenge.
// end //