From: House Committee on Science, Space, and Technology
Posted: Saturday, May 10, 2003
My name is Jerry Grey. I am Director of Science and Technology Policy for the American Institute of Aeronautics (AIAA) and Visiting Professor of Mechanical and Aerospace Engineering at Princeton University. Although the views I express here on the orbital space plane program and related subjects are consistent with those appearing in the AIAA's publications, they are my own and do not necessarily reflect the formal position of the AIAA. Thank you for this opportunity to offer my comments on this important subject.
As you requested, I focus my testimony on the questions you posed.
(1) What key factors should be considered when evaluating human space transportation architectures?
There are two principal factors: safety and cost. Included in "safety" are avoidance of failures, tolerance of failures (i.e., no injury to the crew) should a failure occur, and adequate life-support systems and provisions. Note that "tolerance of failures" implies consideration of crew escape systems. Included in "cost" are development and operational costs, broken down into annual budget requirements and life-cycle cost.
(2) 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?
It is first necessary to define NASA's needs. By far the most critical current need is to meet the International Space Station's transportation requirements. Prior to the loss of Columbia, the Shuttle fleet provided the large-payload capability needed to transport major elements of the International Space Station (ISS) and carried ISS crew members to and from the station, along with sizable amounts of both technological cargo (e.g., experiment apparatus) and expendables (e.g., water). Once the remaining Shuttle fleet returns to flight status, those functions can resume. When that will be, however, is still uncertain.
Additional provisions and emergency crew return capability for up to three ISS crew members have been provided by Russian Soyuz and Progress vehicles. The Russians are committed to provide Soyuz crew-return capability until 2006, and although funding for the number of Progress vehicles needed to continue ISS supply flights without Shuttle support has yet to be identified, there are "workarounds" that are likely to allow the station to function at least minimally until the three Shuttles return to flight status. These include measures already implemented; i.e., using Soyuz lifeboat-replacement flights to transport ISS crew members up and down and reducing the ISS crew to two; finding ways to finance an increase in Russian Progress operations; and using the European Automated Transfer Vehicle (ATV), whose initial launch aboard an Ariane-5 is planned for late next year (assuming the Ariane-5 will have successfully returned to routine service by then). The main near-term concern is that if no source of funding for additional Progress flights can be found, it may become necessary to mothball the ISS late in 2003 or early in 2004 until the Shuttle fleet returns to flight status.
NASA's other needs for space transportation, other than one more servicing mission to the Hubble telescope, do not require the Shuttle's unique capabilities and can be met by the existing Expendable Launch Vehicle (ELV) fleet. Hence the principal requirements for the ISTP, as far as NASA's specific needs are concerned, are (1) to provide an alternative to the Shuttle fleet for servicing the ISS, especially after the next Shuttle failure occurs (at least one such failure is highly likely if the Shuttle is required to operated until 2015 or perhaps even 2020), (2) to provide ISS crew rescue capability after the Russian Soyuz commitment expires in 2006, and (3) perhaps most important, to provide rescue capability for an ISS crew larger than the present 3-person complement. This latter requirement is critical in order for the ISS to fulfill its purpose as a viable research facility. Cancellation by NASA of the original Crew Return Vehicle (CRV) program in February 2001 created this new requirement, which is of major concern to our foreign ISS partners as well as to the U.S. science community.
There is another important function for the ISTP, however: to provide the technology advancement and demonstration necessary to support major improvements in future U.S. access to space. Although not a specific NASA "need," this is clearly part of NASA's overall mission as defined by the 1958 NASA act. Without such improvements all elements of the U.S. space program – commercial, civil, and military – cannot proceed very far beyond what we are able to do today.
The amended ISTP proposal has essentially three primary elements: a Shuttle Service Life Extension Program (SLEP), the Orbital Space Plane (OSP), and development of Next-Generation Launch Technology (NGLT), the latter two of which constitute a revised Space Launch Initiative (SLI).
Next-Generation Launch Technology.
The expansion of the former Generation 3 technology program into the NGLT, as well as the increased emphasis placed on this type of effort in the amended proposal, should be strongly supported. For many years the AIAA has decried the lack of an ongoing program to advance and upgrade space transportation systems; i.e., to have each successive generation of launch systems "in the pipeline" to succeed the current generation. This is relatively standard practice in both the automotive and the aviation industries. It is the lack of such a program in the past that has led to the current crisis in space transportation. The NGLT also incorporates technology advances being pioneered by the DoD, including those of the Director of Defense Research and Engineering's (DDRE) National Aerospace Initiative (NAI) and the Air Force Space Command's Operationally Responsive Spacelift (ORS) program, thereby strengthening not only the NGLT's technical base but also the potential user base for future launch systems.
One area for concern, however, is the NGLT's focus on hydrocarbon-fueled first-stage designs for the future Reusable Launch Vehicle (RLV). Although some offices of the Air Force (mainly the laboratory community) also favor hydrocarbon fuels, a definitive summer hypersonics study conducted by the Air Force Scientific Advisory Board in 2000 concluded that a hydrogen-fueled first stage would be optimum for both rocket-powered and airbreathing-propelled designs.
The planned NGLT also reduces the emphasis on rocket-powered launch systems in favor of airbreathing combined-cycle propulsion. Hence an excellent propulsion prospect, the robust high-thrust, high-pressure, high-performance expansion-cycle engine, a derivative of the ultra-reliable RL-10 (which has employed an expansion cycle with great success for four decades), will receive little or no attention in the NGLT.
Shuttle Service Life Extension Program.
The Shuttle SLEP should also be supported, because for the foreseeable future the Shuttle will be essential to ISS operations. With the loss of Columbia, we now have only three remaining orbiters to conduct these operations through at least 2012 [and possibly much later, because (a) the OSP is likely to encounter development problems that will delay its initial operational date and (b), as I will discuss later, Shuttle capability will be needed even after a successful OSP system is deployed]. Moreover, with this extended operational period, as I mentioned earlier, the likelihood of another Shuttle failure cannot be ignored. One key capability that ought to be explored in the SLEP (I don't know if NASA is planning this) is conversion of at least some missions to fully automated flight operations. More on this later.
Orbital Space Plane.
Now, the OSP. In effect, the OSP and its expendable launch vehicle have been moved chronologically ahead of the Generation-2 program in NASA's original SLI; that is, development of technologies for, and selection of, a reusable system that was to have replaced the Shuttle's function of carrying crew and cargo to and from the ISS at lower cost and with higher reliability. Elements of the old Gen-2 program now appear in the NGLT array of system applications, but the new plan postpones a decision on developing an RLV to 2009 – well into the development phase of the OSP. The OSP also replaces the function of the original CRV that was cancelled in 2001, as I've noted earlier.
So, does the proposed OSP/Evolved Expendable Launch Vehicle (EELV) architecture meet these needs of NASA's?
If we assume successful, on-time development of the OSP, that architecture does indeed meet those needs (except that the proposed initiation date for crew return capability [no later than 2010] is four years beyond the Russian commitment to provide that capability).
But that's a big "if." Let's look at the background.
X-33. NASA's termination of the X-33 single-stage-to-orbit technology demonstrator was certainly a correct decision (although as I told this Subcommittee on April 10, 2000, I really regret the expenditure of over $1 billion and several years on a program that, like the National Aerospace Plane, was doomed to failure by its overambitious goals right from the beginning).
Space Launch Initiative (SLI). NASA's subsequent decision to focus on a much more realistic two-stage-to-orbit architecture for the original SLI was also a wise one. As mentioned earlier, NASA has proposed to continue the evaluation of a reusable hydrocarbon-fueled first stage in the NGLT program, with significant cooperation from DoD. This evaluation could have some effect on the OSP development, in that the new ISTP proposal identifies the possibility of "OSP bridge to a new launcher" in 2016, but its major influence will be on the future (2009) NASA decision regarding a reusable booster. Contrary to NASA's and the DoD National Aerospace Initiative's focus on a hydrocarbon-fueled first stage, however, as I mentioned earlier, the Air Force Scientific Advisory Board's Summer Hypersonics Study in 2000 concluded that a hydrogen-fueled first stage, whether rocket-powered or airbreathing, is better than a hydrocarbon-fueled one. Hence consideration of hydrogen-fueled boosters should not be dropped from the NGLT.
Reusability. NASA should not, however, be blamed for postponing to 2009 a decision on development of a reusable launch system. The basis for that decision was sound: neither the commercial launch market nor the government launch market, even in combination, can support the estimated price tag of a new reusable launcher. Fortunately, while NASA was obeying the August 1994 Presidential directive to spend its time and money pursuing a too-ambitious reusable launch concept, the Air Force and its EELV contractors were able to develop two new expendable launcher families that now open up real possibilities to help solve NASA's near-term needs.
OSP/EELV Suitability. Back to the big "if." First, although the EELV program has demonstrated highly successful initial launches, it is still too early to tell if the EELVs can reliably support a major ongoing NASA requirement such as is posed by the ISS. The prospects are certainly good, and having two widely different vehicles rather than a single one is definitely a "plus." I'll return to this point later. Next, the OSP itself isn't even a "paper" vehicle yet. Although NASA has stated that it will be based on low-risk, current or near-current technology, we won't be able to evaluate its risk until there is better system and subsystem definition. Again, the concept makes good sense, but there is still much to be determined before one could place a soundly based bet on its success. NASA's record for on-budget, on-schedule development of new space transportation systems leaves some doubt as to whether the OSP will really become available on the proposed dates.
Cost. One troubling fact is the current OSP development cost estimate, which, although admittedly premature, ranges from $9 billion to $13 billion. Whatever happened to the $1.2-billion CRV, which was to have performed at least one of the OSP's missions – and the much more critical one at that, in terms of near-term ISS needs? NASA might be better off to focus solely at first on the ISS crew rescue requirement, which is urgently needed both to succeed the Russian Soyuz commitment beyond 2006 and to increase the size of the ISS crew to a viable complement, and put off adding the ISS access function (for both crew and cargo) until the OSP can demonstrate its ability to meet this first milestone. Certainly planning for the access function can begin, but it might make budgetary sense to conduct OSP development in an evolutionary manner, one step at a time, starting with the most critical ISS need. I will discuss this later.
Commercial Launch System Support.
One further point on the ISTP: the original Gen-2 program in the ISTP was also to have provided the technology basis and risk reduction for a new reusable launcher that could begin to serve the entire space launch market – commercial, civil, and military – by the end of this decade. The OSP/EELV does not do that, and the new NGLT postpones possible RLV risk-reduction efforts to 2004 – 2009. In essence, NASA has proposed to delay its responsibility for risk reduction of low-cost reusable launch systems to succeed the EELV and the Shuttle, postponing any decision on proceeding with RLV development until 2009 at best. Indeed, if conditions such as the commercial launch market, DoD interest, and budget concerns at that time are not suitable, NASA may simply choose to put off any consideration of reusable launch-system development until longer-term NGLT program efforts are able to re-set the stage. This would leave the U.S. launch industry with only the two EELV families for large-payload service.
Summary. In short, the revised ISTP is neither overly optimistic nor overly conservative. It is soundly based and should be supported. NASA's thinking in proposing the new OSP/EELV architecture as a second source to the Shuttle for access to and from the ISS does make sense. However, it is too early to assess the risk involved in implementing OSP development or the soundness of its cost estimates.
The highest risk in the OSP element of the ISTP is in the budget and schedule for full-scale OSP development to meet both the crew rescue and ISS transport functions. The highest risks in the NGLT element of the ISTP are (a) postponing RLV risk reduction research to support a go-no go decision in 2009, (b) over-emphasis on hydrocarbon-fueled first stage designs rather than a mix that includes hydrogen-fueled concepts, and (c) the reduced emphasis on advanced expansion-cycle rocket-powered launch systems. The highest risk in the SLEP element of the ISTP is the ability to provide crew safety for all flight modes over an extended period of operations.
To reduce these risks, I recommend (1) an evolutionary approach to OSP development, focusing first on the ISS crew return requirement and then on the transport function; (2) inclusion of hydrogen-fueled first-stage designs and expansion-cycle rocket technology development in the NGLT program, and (3) including in the SLEP (a) a method for reducing the Shuttle crew to four and designing the flight deck as an escape capsule for all flight modes, (b) providing an on-orbit thermal-protection-system inspection and repair capability, and (c) equipping the orbiters for optional fully autonomous operation.
Further considerations are discussed in my response to your subsequent questions.
(3) 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?
Assuming the OSP/EELV architecture is demonstrated successfully by the proposed date of 2012, it is again necessary first to project NASA's needs for space transportation at that time. Those needs will continue to fall into two categories: robot spacecraft missions and those involving human crews. The latter category, at least for the foreseeable future, is almost wholly focused on servicing the ISS. Robot spacecraft will almost certainly continue to be launched primarily by ELVs, including EELVs for the more demanding missions. Hence the primary motivation for continuing Shuttle operations after the (assumed) initial successful operation of the OSP is its role in servicing the ISS.
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