Satellite Launches in the PRC: Hughes
Defense Department Assessments of Damage to National Security
On December 7, 1998, the Department of Defense completed an initial assessment of the January 1995 Apstar 2 launch failure. The assessment was based on the Hughes Apstar 2 reports that had been provided to the Defense Department by the Commerce Department in June 1998.170
The Defense Department assessment concludes that the technical information provided to the PRC by the Hughes Apstar 2 failure analysis can be applied to either PRC rockets or ballistic missiles. The Defense Department considers that the assistance rendered to the PRC by Hughes in the 1995 Apstar 2 failure investigation was a "defense service," and clearly beyond the scope of the export jurisdiction of the Commerce Department.171
According to the Defense Department, "the conclusions outlined in the Hughes/Apstar materials provided to the PRC (and reviewed by the Defense Department for this assessment) were sufficiently specific to inform the PRC of the kinds of launch vehicle design or operational changes that would make the Long March 2E (and perhaps other launch vehicles as well) more reliable," 172 and could assist the PRC military in development of a more reliable fairing for use with ballistic missiles.173
Damage to National Security from the Apstar 2 Failure Investigation
The Hughes Failure Investigation Team included several sub-teams that were assigned the following areas:
- Spacecraft debris
- Material properties
- Video analysis
- Coupled loads
Of these sub-teams, the last three most clearly involved rocket design considerations.
The following account of the activities of these three sub-teams is taken directly from the report of the Hughes Failure Investigation Team.
Coupled Loads: This sub-team reviewed all of the coupled loads analysis information that was available for the Long March 2E rocket/HS-601 satellite combination. They compared the flight data from the satellite accelerometers that have flown on the Long March, the Atlas, and the Ariane. They traveled to Beijing to work beside the CALT engineers to review and participate in the Coupled Loads Analysis methodology. They expanded the standard satellite dynamic model (normally good to 75 Hz) to be valid up to 100 Hz.
Structures: The structures sub-team analyzed the strength requirements and capabilities of the satellite, the interstage, and the rocketís fairing. They performed stress analysis and buckling analysis on the primary structure elements based on detailed knowledge of the satellite and on design information supplied by CALT. They analytically determined the strength requirements and capabilities of the rivets in the fairing zipper. They analytically determined the deformation characteristics and the strength of the dome structure. They analyzed the capabilities of the satellite and rocket clamp bands.174
Aerodynamics: The aerodynamics sub-team was formed in order to understand the forces applied to the fairing which, in turn, are transmitted to the satellite. This team used the expertise of the Hughes Missile Systems Group to determine the flow field around the fairing, the pressure distribution, and the resulting forces and moments on the fairing and launch vehicle. This team also reviewed the NASA SF8001 guidelines that classify the Long March 2E fairing configuration as "separated, unstable." The guideline strongly recommends a comprehensive wind tunnel test program.175
The Defense Department believes it is likely that the Failure Investigation Teamís seven sub-teams provided some of the principal interfaces between Hughes and the PRC in the preparation of individual analytical pieces of the decision tree approach to defining the likely root cause of the failure. In one case, for example, Hughes reported that a sub-team worked "beside" PRC engineers "to review and participate in coupled loads analysis methodology" (quotation in original).176
Each of these sub-teams carried out technical efforts that involved identifying the causes of failure of the Long March 2E fairing, and may have contributed directly to redesign of the fairing to bring its structure up to adequate levels of strength. Moreover, there is indication in the Hughes report on the launch failure that not only the results of Hughes team and sub-team work, but also the methods and know-how based on experience in the areas of airload determination and structural analysis and design, may have been imparted to the PRC.
At a minimum, it appears evident from the Hughes Failure Investigation Team report that the PRC member of the International Oversight Team could have had access to all of it. Indeed, such access is guaranteed by the International Oversight Teamís charter. The statement in the report that the Coupled Loads Analysis sub-team "traveled to China to work beside the CALT engineers to work and participate in the Coupled Loads Analysis methodology" indicates a much more focused channel for possible technical information exchange with the PRC.
The conclusion reached by the Hughes Failure Investigation Team was that the initial failure of the Long March 2E launch of the Apstar 2 occurred in the rocket fairing. This failure was caused by the aerodynamic forces, buffeting, and aeroelastic (that is, interactions between structural dynamics and airloads) effects that are encountered as the rocket enters the transonic phase of flight. These effects were accentuated by the winds aloft and wind shear that were high on the day of the launch.
The Hughes Failure Investigation Team also noted the importance of the fact that the 1992 failure of the Long March 2E carrying the Optus B2 satellite occurred under the same (winter) wind conditions that prevailed at the time of the 1995 Apstar 2 launch failure of the same PRC rocket. The Hughes team pointed out that the three successful Long March 2E launches all took place when such wind conditions did not prevail.
It was further concluded on the basis of structural analyses that the fairing failed either in the rivets of the fairing zipper or in the fiberglass nose dome. Hughes engineers actually made a detailed stress analysis of the redesign of the rivets in the fairing zipper.
Damage to National Security From the Sharing of Coupled Loads Analysis
Coupled loads analysis simulates and assesses the interplay of the loads on the rocket during flight, including interaction between the satellite and the rocket which are stacked one on top of the other.
This analysis is based on a finite element model, a mathematical representation of the specified grid points that define the physical body of the satellite. Finite element analysis is the analysis of structural stress about the satellite body grid points.
Coupled loads analysis combines the satellite and rocket models for loads analysis. Information contained in the Hughes/Apstar materials indicates that, based on that analysis, Hughes learned that the PRC coupled loads analysis was deficient.
As with satellites and rockets, coupled loads analysis and finite element analysis are applied in the design and testing of missiles to the interaction of the components of a missile and warhead during launch.
The Defense Department believes it is reasonable to infer that, during the close collaboration between Hughes and PRC engineers, Hughes imparted to the PRC sufficient know-how to correct the overall deficiencies in their approach to coupled loads analysis and the PRCís finite elements model.177
Much of the work during the investigation appears to have been done in the PRC in close collaboration with PRC experts. Hughes clearly was concerned about the serious flaws in PRC modeling and analysis of aerodynamic loads on the Long March rocketís fairing. According to the Hughes/Apstar materials, among the lessons Hughes said it learned was that it cannot rely exclusively on the PRC to perform coupled loads analysis.
Damage to National Security From Providing the PRC With Information Concerning Deficiencies in the Fairing, and Resultant Improvements to PRC Rockets and Ballistic Missiles
The Defense Department determined that, according to the Hughes/Apstar materials, deficiency in PRC design of the rocket fairing was cited as the most likely "root cause" of the Long March 2E failure. Hughesí conclusions highlighted numerous areas of concern focusing on improving the Long March rocket design.
The conclusions included:
- Concerns about the fairing design
- The rivet strength of the zipper
- Weaknesses in the nose cap split line
- The shape of the fairing
There were also concerns about certain Long March rocket interfaces (such as the design of the clamp separation band) and inadequate vent area in the rocketís fairing.178
The Defense Department found that, over the course of about five months in early 1995, Hughes conducted a broad and in-depth investigation that involved significant and detailed technical interchanges between Hughes and PRC experts.179 These interactions specifically addressed a full range of possible causes for the failure that included a comprehensive analysis of the Hughes satellite and the PRC rocket fairing and flight loads.
The investigationís conclusions that were provided to the PRC were very specific and identified the need for modifications in the Long March rocket fairing design and in PRC launch operations.180
The PRC made several changes to the Long March 2E fairing in 1995 to address possible failure causes, including:
- Structural changes to strengthen the fairing
- Improved coupled loads analysis
- Tighter winds-aloft launch go/no-go criteria, to prevent launches in winds above a specific threshold
Further, the PRC modified the Long March 2E guidance system by adding a wind-bias trajectory compensation to limit the Long March 2Eís angle of attack.
All of the above changes by the PRC directly addressed Hughesí recommendations conveyed to the PRC in the course of the failure investigation.
The Defense Department assessment concluded that:
[T]he [PRC] modifications in the LM-2E fairing, coupled loads analysis, and launch operations apparently addressed the problems because the PRC successfully launched two non-Hughes commercial communications satellites on LM-2E vehicles in November and December 1995.
Although the LM-2E has not been used since then, the lessons learned from the APSTAR 2 investigation are directly applicable to fairings on other launch vehicles, including those used to boost PRC military satellites. . .
[A]lthough it is possible that the PRC may be able to transfer the benefits of this launch failure investigation to its ballistic missile programs, the utility to those programs would be limited largely to development of a more reliable fairing for use with advanced payloads on military ballistic missiles.
Other Information Learned By the PRC, and Defense Department Reaction
The Hughes investigation provided the PRC with details about the satellite design and some manufacturing/inspection practices to prove that the satellite was not responsible for the failure, and that a faulty Long March rocket fairing design was the likely root cause of the failure.
The joint investigation also provided the PRC with insight into U.S. diagnostic techniques for assessing defects in rocket and satellite design.
The Defense Department concluded that there was no evidence of any limits on the Apstar 2 investigation imposed by the Commerce Department or any other U.S. Government agency. As a consequence, the PRC and Hughes engaged in technical exchanges, such as those concerning coupled loads analysis and finite elements analysis, that would allow the PRC to gain specific insight into specific rocket design, operational problems, and corrective actions.181
In addition, the Defense Department report stated that
. . . based on DODís experience monitoring technical interchange meetings and related activities in connection with foreign launches of U.S. commercial satellites, it is reasonable to conclude that during the course of the five-month Hughes investigation there were significant interactions with the PRC of a highly technical and specific nature that are not reflected in the Hughes/Apstar materials reviewed by DOD.182
The Defense Department assessment also noted that its findings and conclusions are "necessarily preliminary in nature," given the incompleteness of the information available. For example, the Defense Department assessment properly noted the assistance a Hughes "subteam" provided in coupled loads analysis, but also that "the precise nature of the analyses performed and the composition of skills of the team members cannot be ascertained from the Hughes/Apstar materials reviewed by the Defense Department." 183
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