Ltv Aerospace & Defense Company

Loral Vought Systems Corporation

Douglas W Freitag

James Richard Wood

David L Hunn

Shawn M Keough

Kerry K Richardson

A secondary heat shield is positioned within a heat shielding radome and spaced from the nose of the radome in order to protect an antenna against thermal radiation from the inner surface of the radome. The secondary heat shield can be a single unitary component integrally formed of a lightweight ceramic which can be easily fabricated in the desired shape and which maintains its shape. The secondary heat shield can be formed of a lightweight ceramic material having a dielectric constant at 17 GHz and 21.degree. C. in the range of about 1 to about 3.5, a thermal conductivity of less than 0.7 W/M-K, and a density at 21.degree. C. of less than 3.2 g/cc. The most preferred ceramic material has a dielectric constant at 17 GHz and 21.degree. C. in the range of about 1.01 to about 2.0, a thermal conductivity in the range of about 0.04 to about 0.08 W/M-K, and a density at 21.degree. C. of less than about 1.0 g/cc. The secondary heat shield comprises a forward dome portion, which can be shaped to act as a lens for radiation emitted from or received by the antenna, and a rearwardly extending skirt portion which laterally encompasses the antenna and other temperature sensitive components.

Radome with secondary heat shield

A high temperature, high strength in-situ reinforced ceramic composite adapted for use in various applications including missile radomes in which microwave transparency is required in a high temperature environment. The material is manufactured by a pressureless sintering process, in which silicon nitride and barium aluminosilicate are blended together, isostatically pressed into a desired shape and thereafter sintered.

BAS reinforced in-situ with silicon nitride

A process for producing a green composite structure by isostatic compression and filtration. A suspension of colloidal size matrix powders is established in a carrier liquid. The suspension is incorporated into a die chamber having a filter opening containing a filter which is permeable to filtrate from the suspension under applied pressure but substantially impermeable to the matrix powders. An elevated pressure is isostatically imposed on the colloidal suspension within the die chamber. The pressure is maintained for a period of time to expel at least 20% of the liquid originally in the colloidal suspension through the filter opening. A specific die chamber comprises a rigid cage structure and an expandable bladder within the cage structure into which the colloidal suspension is introduced. The cage structure is disposed within a pressure vessel which can be initially evacuated to cause the bladder to conform to the cage structure and then pressurized with fluid for the isostatic compression procedure.

Method for producing structures by isostatic compression

A process for the production of reinforced refractory composite structures which may be of high density and shaped in desired three dimensional configurations. The shaped composite structures are produced by forming a suspension of particulate materials including a colloidal refractory power, colloidal sintering aid, and refractory reinforcement whiskers in a carrier liquid. The colloidal suspension is conformed to a desired configuration and brought into contact with a semipermeable membrane. A pressure is imposed on the suspension in the desired configuration to expel liquid from the suspension through the membrane to arrive at a green composite having a density of at least 40% of theoretical density. After drying, the green composite is then sintered under conditions to form an intergranular liquid phase in the composite providing further densification. A specific composite is a silicon carbide reinforced silicon nitride composite. The green composite may be sintered to provide a density of at least 93% of theoretical to produce a closed impermeable composite surface. The composite may then be subjected to hot isostatic pressing.

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Arlington, TX, United States of America

Douglas W Freitag