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

Abstract

Recent progress to better understand the environmental threat of micrometeoroid and space debris to the radiator for the solar dynamic power system on Space Station Freedom is reported. The objective has been to define a design which would perform to survivability requirements over the expected lifetime of the radiator.A previous paper described the approach developed to assess on-orbit survivability of the solar dynamic radiator due to micrometeoroid and space debris impacts. Preliminary analyses were presented to quantify the solar dynamic radiator survivability. These included the type of particle and particle population expected to defeat the radiator bumpering. Results of preliminary hypervelocity impact (HVI) testing performed on radiator panel samples were also presented. This paper presents results of a more extensive test program undertaken to further define the response of the solar dynamic radiator to HVI. Tests were conducted on representative radiator panels (under ambient, nonoperating conditions) over a range of particle size, particle density, impact angle, and impact velocity. Target parameters were also varied. Data indicate that analytical penetration predictions are conservative (i.e., pessimistic) for the specific configuration of the solar dynamic radiator.Test results are used to define the solar dynamic radiator reliability with respect to HVI more rigorously. Test data, analyses, and survivability results are presented.

Improvement of methods for evaluating the spacecraft pressure wall penetration probability

“…It has undergone extensive revisions and updates [NASA JSC HITF website; Christiansen et al, 1992Christiansen et al, , 1997 BUMPER calculates the number of failures by determining the number of meteoroid/debris particles that exceed the ballistic limits for each element of the FEM, then summing failures over all elements and/or particular regions of interest in the FEM. The number of failures is determined by breaking the debris threat into 90 threat directions and the meteoroid threat into 149 threat directions for each element of the FEM.…”

“…NASA Johnson Space Center assesses ISS Probability of No Penetration (PNP) using the BUMPER code [NASA JSC HIT website; Christiansen et al, 1992]. Critical elements on ISS are all pressurised modules, external pressure vessels, and stored energy devices (such as control moment gyros and gyrodynes).…”

“…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].…”