Toshiya Hanada

Low-velocity projectile impact on spacecraft

Abstract Various impact phenomena are encountered in space, among which debris impacts are of most concern. In terms of velocity range of the impacts, structural hazard at very large velocity of over a few km/s is much investigated. However, lower velocity impacts can also be encountered, with similar fatal effects to spacecraft. Examples are debris impacts in geostationary altitude and those onto rear side of spacecraft in low earth orbit. It should be pointed out that debris shield like Whipple bumper system is not effective at low velocities, and no other effective means are known to protect spacecraft from projectiles encounted at less than 1 km / s . A series of laboratory impact tests are conducted to find out characteristics of both structural damages and fragments created and released into space. The major items made clear are that characteristics of fragments are similar to those of hypervelocity impacts. Structural damage to honeycomb panels and mesh-type parabola dishes will be described as examples of debris impact in geostationary orbit. Another example to be investigated is impacts of rocks and steel projectile onto structure of sampling mechanism on a surface of an asteroid, a mission to fly in the year 2002.

Geo debris environment: A model to forecast the next 100 years

Abstract The geostationary orbit is a unique natural resource that mankind will find useful for many generations to come. During a little over than 30 years, more than 600 objects have been placed into this region. Most of these objects were left in stable orbits to remain there for many thousands of years. At least three of these objects experienced fragmentation, whose fragments are too small to be detected from the earth, but are large enough to damage or destroy other satellites. The motion of these objects was analyzed to find out potential collision hazards including longitudinal clustering and sun-moon gravity effects. A breakup model was adopted partly reflecting laboratory experiments. With a simple object accumulation model the debris environment evolution was evaluated, under realistic debris mitigation scenarios to be adopted in the near future.

Orbital debris environment model in the geosynchronous region

The Kyushu University orbital debris environment model in the geosynchronous region has been updated to provide a better and more accurate description and understanding of orbital debris environment than the previous model. The main advantage of the present model over the previous model is to introduce more realistic breakup dispersion to estimate collision hazards to other spacecraft caused by breakup fragments. The results from the new model indicate that all aged satellites should move into a disposal orbit at the end of mission to reduce potential hazards to operational satellites. However, boosting up all aged satellites cannot preserve the current orbital environment sufficiently because debris fragments from explosions are still hazardous to operational satellites. The results also indicate that safekeeping procedures for all rocket bodies and spacecraft that remain in the geosynchronous region after completion of their mission are required as well as in low Earth orbit.

Using NASA Standard Breakup Model to Describe Low-Velocity Impacts on Spacecraft

The applicability is examined of the hypervelocity collision model included in the NASA standard breakup model 2000 revision to low-velocity collisions possible in space, especially in the geosynchronous regime. The analytic method used in the standard breakup model is applied to experimental data from low-velocity impact experiments previously performed at Kyushu University at a velocity range less than 300 oils. The projectiles and target specimens used were stainless steel balls and aluminum honeycomb sandwich panels with face sheets of carbon fiber reinforced plastic, respectively. It is concluded that the hypervelocity collision model in the standard breakup model can be applied to low-velocity collisions with some simple modifications.

Orbital Evolution of Cloud Particles from Explosions of Geosynchronous Objects

Current orbital debris search strategies for telescopes observing in geosynchronous Earth orbit are designed around the known orbital distributions of cataloged objects. However, the majority of cataloged objects are believed to be intact spacecraft and rocket bodies, not the debris particles the searches are intended to locate. If there have been breakups in geosynchronous Earth orbit, the explosions may have put the debris into orbits that are significantly different from those in the catalog. Consequently, observation plans optimized for the catalog population may not be optimized for any unseen debris populations. Some hypothetical cases and a real near-synchronous U.S. Titan IIIC transtage explosion will be presented to demonstrate this effect. Perturbing accelerations to be considered for orbital evolution are the nonspherical part of the Earth’s gravitational attraction and gravitational attractions due to the sun and moon. Solar radiation pressure effects are omitted in this analysis, not because they are unimportant for this type of analysis, but to concentrate on the primary orbit perturbations.

Consequence of Continued Growth in the GEO and GEO Disposal Orbital Regimes

To date more than 800 spacecraft, upper stages, and apogee kick motors are known to reside in geosynchronous and nearby orbits, including geosynchronous disposal (i.e., collection) orbits. U.S. and European ground-based sensors have detected an even larger number of debris greater than 10cm in diameter. Using projections of geosynchronous deployment characteristics and disposal rates, NASA and Kyushu University models of the geosynchronous and super-geosynchronous orbital regimes have examined the sensitivity of the long-term satellite population to various scenarios. Emphasis has been placed on the rate of collisions in the geosynchronous orbit and in the higher collection orbits and on the significance of cross-regime contamination. The sensitivity of the long-term environment to low velocity (0–1km/s) collision breakup model parameters and on the minimum height of collection orbits has also been explored. Results are presented in terms of both satellite population and spatial density.

Effective Search Strategy Applicable for Breakup Fragments in the Geostationary Region

This paper proposes to apply the space debris modeling techniques to devise an effective search strategy applicable for breakup fragments in the geostationary region. The space debris modeling techniques describe debris generation and orbit propagation to effectively conduct predictive analyses of space objects that include characterizing, tracking, and predicting the behavior of individual and groups of space objects. Therefore, the techniques can predict population of debris from a specific breakup event. The population prediction specifies effectively when, where, and how optical measurements using ground-based telescopes should be conducted. The space debris modeling techniques can also predict motion of debris in successive images taken with ground-based telescopes. The motion prediction specifies effectively and precisely how successive images of objects in the geostationary region should be processed. This paper also validates the proposed search strategy through actual observations, targeting the ...

Microsatellite Impact Tests to Investigate the Outcome of Satellite Fragmentations

To predict the future orbital environments, it is necessary to know outcome of the satellite fragmentation. The NASA standard breakup model is designed to describe the outcome of typical satellite fragmentation. This model is an empirical model and themajor data sources are the 1980s on-orbit satellite breakup events and the ground-based Satellite Orbit Debris Characterization Impact Test series conducted in early 1990s. The target cubic satellites ranged from 15 to 20 cm in size and about 1000 g in mass. Results from all seven impact tests carried out in 2008 are shown in this paper and compared with the NASA standard breakupmodel to demonstrate potential improvements of the model in the future.

Optical Observations of the Orbital Debris Environment at NASA

Abstract To monitor the orbital debris environment and facilitate orbital debris modeling and forecasting, the Orbital Debris Program Office of the NASA Johnson Space Center operates two principal telescopes: the liquid mirror telescope (LMT) and the charge coupled device debris telescope (CDT). Both telescopes are maintained at the NASA Cloudcroft Observatory, a 15-meter dome at 2761-meter elevation near Cloudcroft, NM. The LMT became operational in October 1996. Approximately 580 hours of digital video data from the LMT have been collected and processed by an automated hardware/software system. Results from 504 hours are presented. This paper also presents the results of a study of the detection sensitivity of the LMT system as well as a new measurement-based model for estimating object size from LMT measurements. The CDT, the other principal component of the optical program, became operational in November 1997. The CDT is currently being used in a statistical survey of catalogued and uncataloguued debris in geosynchronous earth orbit. Approximately 180 nights worth of data have been collected and results from a portion of this data are presented. A new direction for the CDT is to investigate various regions in GEO that would contain debris from hypothesized break-ups.

Towards A Better Understanding of Space Debris Environment

This paper briefly introduces efforts into space debris modeling towards a better understanding of space debris environment. Space debris modeling...