Large compound curved surfaces for collecting and concentrating radiation are fabricated by the use of several common machining and forming processes. Lightweight sectors are assembled into large reflectors. With this concept of fabrication, integrally stiffened reflective sectors up to 25 square feet in area have been produced

Reader, A. F.

Russell, W. E.

Werner, E. A.

English

NASA Technical Reports Server

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Februar 1967	 Brief 67-10010 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Process Sequence Produces Strong, Lightweight Reflectors of Excellent Quality 
_1 __ '1	 E
	
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Clamps 
The problem: 
To fabricate large compound curved surfaces for 
collecting and concentrating radiation. Existing meth-
ods are not satisfactory for producing rigid, light-
weight sectors or panels to the dimensional and sur-
face accuracy desired. Such accuracy with stability 
requires a smooth continuous surface supported by an 
integral network of stiffener ribs machined on the 
opposite side. Machining of such a network in the 
curved shape is extremely difficult and expensive.
The solution: 
The use of several common machining and forming 
processes in a sequence that makes it possible to ac-
curately fabricate lightweight sectors for assembly into 
large reflectors. 
How it's done: 
Flat plate sectors are first polished to the final sur-
face finish on one side and the polished surface cov-
ered with protective tape. Stiffener ribs are then 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19670000010 2020-03-11T20:20:58+00:00Z
machined into the unpolished side by tape controlled 
milling. 
The polished and machined sectors are then formed 
on an aluminum forming fixture that has an accurately 
machined and polished convex surface. The flat sector 
is placed on the fixture and loaded by spring loaded 
clamps located around the edges of the sector. The 
fixture, containing approximately 80 kw of resistance 
heaters, is heated to approximately 400° F and the 
clamping is increased until the sector edges are drawn 
close to the fixture surface. The sector-edge-to-fixture-
surface joint is then sealed with high temperature sili-
con adhesive tape and a vacuum is drawn between the 
polished sector surface and the polished fixture sur-
face. The fixture and sector are then heated to ap-
proximately 5500 F and held for about one hour as 
atmospheric pressure forces the sector to conform to 
the fixture surface. The assembly is slowly cooled to 
approximately 2000 F, the vacuum is released, and the 
sector removed. The edge machining and bolt hole 
drilling are performed on a vacuum machining fixture, 
which is identical to the forming fixture but without 
heaters. Accurate hole drilling is accomplished by po-
sitioning two adjacent sectors on the machining fixture 
and drilling body-fit bolt holes.
The sectors are individually cleaned, epoxy coated, 
and aluminized for high reflectivity prior to final as-
sembly. An important advantage of this concept is 
that all polishing of the reflective surface is performed 
prior to the cross section machining and forming. 
Notes: 
I. With this concept of fabrication, integrally stiff-
ened reflective sectors up to 25 square feet in area 
have been produced. Mirrors 20 feet in diameter, 
made of 12 such sectors, have been fabricated. 
2. Inquiries concerning this invention may be directed 
to:
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B67-10010 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: Austin F. Reader, 
Walter E. Russell,
and Edward A. Werner
(Lewis-331) 
Brief 67-10010	 Category 05


Process sequence produces strong, lightweight reflectors of excellent quality

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