Electrically conductive spacer for multilayer insulation grounding
As spacecraft electronic control and human support systems get increasingly sophisticated, protection for those systems becomes more critical. Multilayer insulation (MLI) is a common thermal protection system on spacecraft, and it includes layers of metalized film that may build up electrostatic charge that can be hazardous in many respects. MLI should be electrically grounded to prevent the unwanted electrostatic buildup while meeting thermal performance requirements. Aspects of the present disclosure involve a significant improvement in grounding methods within a multilayer insulation structure with minimal thermal performance degradation. Metalized spacers create electrical continuity through layers and may have only a single layer connecting to chassis ground. Multiple spacers can be utilized for larger blankets for grounding redundancy. Thermal performance penalty can be orders of magnitude smaller than conventional techniques.
1 . A multilayer insulation comprising:
a first insulation layer;
a second insulation layer;
a third insulation layer;
a first conductive structural spacer structure positioned between the first insulation layer and the second insulation layer, the first conductive structural spacer structure including a metalized outer surface with defined features and geometries to minimize solid thermal conductivity and provide electrical continuity between the first insulation layer and the second insulation layer;
a second conductive structural spacer positioned between the second insulation layer and the third insulation layer, the second conductive structural spacer structure including a metalized outer surface with defined features and geometries to minimize solid thermal conductivity and provide electrical continuity between the second insulation layer and the third insulation layer; and
an electrical connection between the first conductive structural spacer and the second conductive structural spacer providing an electrical path between the first insulation layer, first conductive structural spacer, second insulation layer, second conductive structural spacer and the third insulation layer.
2 . The multilayer insulation of claim 1 wherein the geometry of each of the first conductive structural spacer and the second conductive structural spacer define an A/L ratio of 1.36×10 −4 m to reduce conducted heat flux and an electrical resistivity of 0.1 to 2.0Ω to reduce electrical continuity between the first insulation layer and the second insulation layer of the multilayer insulation.
3 . The multilayer insulation of claim 1 wherein each of the first conductive structural spacer structure and the second conductive structural spacer are encapsulated with a layer of electrically conductive metal in the range of 350-1500 Angstroms and wherein the electrically conductive metal is Aluminum, Nickel, Silver, Gold, Chromium, or Titanium.
4 . The multilayer insulation structure of claim 1 wherein each of the first conductive structural spacer structure and the second conductive structural spacer comprise a low thermal conductivity material.
5 . The multilayer insulation structure of claim 4 wherein the low thermal conductivity material is ULTEM, PEEK, LCP or Alumina.
6 . The multilayer insulation structure of claim 1 wherein the first conductive structural spacer structure is attached to the first insulation layer and the second conductive structural spacer is attached to the second insulation layer through bonding with an electrically conductive adhesive that provides an electrical ground path through the metalized surface of the structural support spacer to the first insulation layer and the second insulation layer.
7 . The multilayer insulation structure of claim 6 wherein multiple stacks of conductive structural support spacers can provide redundant ground paths of the multilayer insulation.
8 . The multilayer insulation structure of claim 1 wherein a chassis ground tail extends from at least one of the first insulation layer, the second insulation layer or the third insulation layer, and electrically coupled with the electrical path between the first insulation layer, first conductive structural spacer, second insulation layer, second conductive structural spacer and the third insulation layer.
9 . The multilayer insulation of claim 1 further comprising:
an electrically conductive tape on the second insulation layer, the electrically conductive tape extending from a first side of the second insulation layer in electrical contact with the first conductive structural spacer to a second side of the second insulation layer in electrical contact with the second conductive structural spacer, the electrically conductive tape providing the electrical connection between the first conductive structural spacer and the second conductive structural spacer.
10 . The multilayer insulation of claim 1 further comprising:
an aperture in the second insulation layer;
a conductor extending through the aperture and in electrical contact with the first conductive structural spacer and the second conductive structural spacer, the conductor providing the electrical connection between the first conductive structural spacer and the second conductive structural spacer.
11 . The multilayer insulation of claim 10 wherein the second insulation layer comprises a first outer metalized layer and a second outer metalized layer with a non-conductive polymer layer therebetween, the first conductive structural spacer in contact with the first outer metalized layer and the second conductive structural spacer in contact with the second outer metalized layer, the conductor extending through the aperture providing an electrical connection between the first outer metalized layer and the second outer metalized layer through the non-conductive polymer layer.
12 . The multilayer insulation of claim 11 wherein the conductor is a conductive adhesive.
13 . The multilayer insulation of claim 1 further comprising
a first plurality of first non-conductive structural spacers positioned between the first insulation layer and the second insulation layer;
a second plurality of second non-conductive structural spacers positioned between the second insulation layer and the third insulation layer, the second plurality of second non-conductive structural spacers aligned with respective first non-conductive spacers to maintain spacing between the first insulation layer and the second insulation layer, and to maintain spacing between the second insulation layer and the third insulation layer, and
wherein the first insulation layer, the second insulation layer and the third insulation are thermally insulated and electrically isolated from one another by the first plurality of first non-conductive structural spacers and the second plurality of second non-conductive structural spacers.
14 . The multilayer insulation of claim 13 wherein:
the first non-conductive structural spacer and the second non-conductive structural spacer are axial aligned, the second non-conductive structural spacer electrically coupled to ground, with the combination of the first non-conductive structural spacer, the second non-conductive structural spacer, the electrical connection between the first non-conductive structural spacer and the second non-conductive structural spacer providing an electrostatic grounding path between the third insulation layer, the second insulation layer and the first insulation layer.
15 . A multilayer insulation comprising:
a first insulation layer;
a second insulation layer; a first conductive structural spacer structure positioned between the first insulation layer and the second insulation layer, the first conductive structural spacer structure including a metalized outer surface with defined features and geometries to minimize solid thermal conductivity and provide electrical continuity between the first insulation layer and the second insulation layer; a second conductive structural spacer including a metalized outer surface with defined features and geometries to minimize solid thermal conductivity and provide electrical continuity between the second insulation layer and the third insulation layer; and
wherein the first conductive support spacer is aligned with a first hole in the first insulation layer, and the second conductive support spacer is aligned with a second hole in the second insulation layer, where each of the first hole and the second hole includes conductive adhesive expressed through the respective holes creating electrical continuity across a dual metalized film or radiant barrier such as PET or Kapton of the respective first insulation layer and second insulation layer.