On Protection of Freedom’s Solar Dynamic Radiator From the Orbital Debris Environment: Part I—Preliminary Analysis and Testing

Abstract

A great deal of experimentation and analysis has been performed to quantify penetration thresholds of components which will experience orbital debris impacts. Penetration has been found to depend upon mission-specific parameters such as orbital altitude, inclination, and orientation of the component; and upon component specific parameters such as material, density, and the geometry particular to its shielding. Experimental results are highly dependent upon shield configuration and cannot be extrapolated with confidence to alternate shield configurations. Also, current experimental capabilities are limited to velocities which only approach the lower limit of predicted orbital debris velocities. Therefore, prediction of the penetrating particle size for a particular component having a complex geometry remains highly uncertain. This paper describes the approach developed to assess on-orbit survivability of the solar dynamic radiator due to micrometeroid and space debris impacts. Preliminary analyses are presented to quantify the solar dynamic radiator survivability, and include the type of particle and particle population expected to defeat the radiator bumpering (i.e., penetrate a fluid flow tube). Results of preliminary hypervelocity impact testing performed on radiator panel samples (in the 6 to 7 km/sec velocity range) are also presented. Plans for further analyses and testing are discussed. These efforts are expected to lead to a radiator design which will perform to Space Station Freedom requirements over the expected lifetime.

Improvement of methods for evaluating the spacecraft pressure wall penetration probability

“…Active radiators are susceptible to meteoroid/debris impact damage and puncture of the coolant lines contained within the panels, leading to degradation or failure of the heat rejection system. Hypervelocity impact tests have been performed on various radiator panel configurations to assess vulnerability to meteoroid/debris impact and develop ballistic limits [Rhatigan et al, 1990[Rhatigan et al, , 1992Melin, 1990]. …”

“…Painted surfaces are subjected to spall (detachment) around the impact site, although this may not be very significant for properly prepared and painted surfaces. For instance, Z-93 painted radiator surfaces spalled approximately 2-3 hole diameters around the impact point in one series of hypervelocity impact tests at NASA Johnson Space Center [Rhatigan et al, 1990[Rhatigan et al, , 1992. Silver-teflon tape on honeycomb panels will debond to a similar extent around hypervelocity impact sites [Christiansen et al, , 1998].…”

On Protection of Freedom’s Solar Dynamic Radiator From the Orbital Debris Environment: Part II—Further Testing and Analysis

“…The solar dynamic power system and the SDR have been described in detail elsewhere. ( 14,10 ) A previous paper (13) gave an overview of the preliminary testing and analyses performed to initially quantify the probable survivability of the SDR over its lifetime in the orbital debris environment. This paper describes further testing and analysis undertaken to achieve a better understanding of the response of the SDR to the environmental threat of hypervelocity impact (HVI) from micrometeoroids and space debris.…”

“…The previous paper (13) reported results of a series of 12 HVI tests performed on SDR panel samples. That test series has been designated 'phase 1' of the current program.…”