Technique eliminates hazards of handling propellants and permits determination of structure index of gel by remote control. Rheometer weighs cone of propellant gel which remains on a disc that has been slowly pulled out of the gel

Globus, R. H.

Vanderwall, E. M.

English

NASA Technical Reports Server

1972	 B72-10026 
is NASA TECH BRIEF 
Ames Research Center 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.. 20546. 
Rising-Plate Rheometer 
.
The problem: 
To measure the degree of structure of hazardous, 
hygroscopic, and reactive cryogenic propellant gels. 
The solution: 
Weigh the cone of propellant gel which remains 
on a disc that has been slowly pulled out of the gel. 
How it's done: 
Studies of gelled cryogenic propellants require the 
measurement of static properties such as degree of 
structure or structure index. Ordinarily, the structure 
index is measured by determining the maximum 
weight of a sphere that can be supported by the 
gel. However, this technique requires some manual 
operations that may be hazardous to the operator 
and usually result in excessive exposure of reactive 
or hygroscopic propellants to the atmosphere. A new 
technique was developed to eliminate hazards of 
handling the propellants and to permit determination 
of the structure index of a gel by remote control. 
A thin metal disc is deeply immersed in the gel 
in a horizontal position. After a period of time, gov-
erned largely by the character of the gel, the disc 
is very slowly withdrawn; an inverted cone of pro-
pellant remains on the disc. The angle of repose, 
that is, the angle between the horizontal disc and 
the side of the cone, is related to the degree of 
structure of the gel; the greater the degree of struc-
ture, the greater the angle of repose. 
The angle of repose does not have to be measured 
directly because the mass of propellant which re-
mains on the disc is an indirect measure of the angle 
of repose, for as the degree of gel structure increases, 
the mass of propellant remaining on the disc in-
creases. This mass, in turn, provides a direct measure-
ment of the gel structure under zero-shear conditions. 
Measurement of the mass of gel on the disc is 
made by a strain gage that is situated outside of the 
container with the gel propellant; thus, there is no 
need for the operator to be in the vicinity of the 
propellant. Moreover, since the disc need not be 
very large, the measurement can be made on small 
quantities of material and often can be included with 
other measuring devices in the container holding the 
propellant. 
The results of experiments indicate that minor dif-
ferences in rate of rise of the disc, disc shape, disc 
area, and disc tilt do not affect results significantly. 
For comparison of different propellant compositions, 
however, it is necessary to take into account their 
densities; this is done by calculating the volume of 
the cone of the propellant from the measured mass 
of the propellant in the cone. The structure index of 
the propellant gel is then determined from a graph 
of the index versus cone volume. 
The following table shows correlation of the 
structure index obtained by the new technique and 
the sphere method; the data were obtained on gels 
prepared from vacuum pump oil and a silica 
gelling agent.
Structure Index, N/rn2 
Gellant, Sphere New Volume, 
wt-% Method Method ml 
2.5 20.0 25.0 1.88 
3.0 70.0 70.0 5.28 
3.5 170.0 150.0 11.31 
4.0 240.0 190.0 14.33
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19720000026 2020-03-17T03:24:00+00:00Z
These data were used to prepare the graph of 
structure index versus cone volume discussed in a 
previous paragraph. 
Note: 
No additional information is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B72-10026
Patent status: 
No patent action is contemplated by NASA. 
Source: R. H. Globus and

E. M. Vander Wall of

Aerojet Liquid Rocket Company

under contract to

Ames Research Center

(ARC-10524)
. 
S 
Category 03


Rising-plate rheometer

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