System stabilizes aximuth of gondolas which are carried by high-altitude balloons as platforms for tracking telescopes. When telescopes must be constantly aimed at specific targets, control system stabilizes gondola to within 5 arc-seconds

Squillari, W.

Studenick, D. K.

Tyler, A. L.

English

NASA Technical Reports Server

June 1975	 B75-10085 
NASA TECH BRIEF S
Goddard Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Torque Control System 
	
To Shroud-	 Fitting	 The problem: 
lines Cap Gondolas carried by high-altitude balloons are 
often used as platforms for tracking telescopes. The 
telescopes must be constantly aimed at specific 
- targets. Unfortunately, once the balloons reach the 
altitude of approximately 100,000 feet (30,000 m), 
they start to rotate at a slow rate. This rotation is 
transferred to the gondolas through parachute 
shroudlines. Various devices have been used to 
stabilize the gondolas; however, none has the 
It 
	
Elongated/'	 accuracy necessary for the tracking telescopes (5 
	
Tube '\	 arc-seconds). II M Rotor Winding 
tJI.41 - Bearings,
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:flhi:!nflTj
y Rotor Winding 
Electric 
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The solution: 
A new torque control system stabilizes the azimuth 
of a gondola to within 5 arc-seconds. 
, How.lt's done:.... . . 
The system comprises a torque sensor and an active 
bearing. The torque sensor is connected between the 
lower ends of the shroudlines and the gondola and 
senses torque applied by the shroudlines _to the 
gondola. The sensor generates pulses proportional to 
the applied torque. The pulses are fed by. electrical 
lines to an active bearing which is located between the 
upper end of the parachute and the lower end of the 
balloon. The bearing is driven either clockwise or 
counterclockwise to counteract the detected torque. 
This system is designed to stabilize a 2,500-pound 
(1,136-kg) gondola. 
The sensor as shown in Figure 1 includes a shaft 
approximately 20 inches (50 cm) long. Much of the 
shaft is cruciform in cross section which allows it to be 
shorter than an ordinary rod and still provide the 
same axial strength and torque sensitivity. The top 
end of the shaft is screwed into a bore in the fitting 
cap, and the bottom end is similarly connected to the 
bore end fitting. The top and the bottom are 
connected, respectively, to the shroudlines and the 
gondola.
(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=19750000085 2020-03-19T20:03:39+00:00Z
. 
To Balloon 
Sprocket
DC Motor 
To
Parachute 
Figure 2. Active Bearing
S The sensor also includes a synchro transformer. The transformer rotor winding is bonded to the 
cylindrical portion of the shaft. The stator winding is 
concentric with the rotor and is mounted on a piston 
which is fixed to the upper end of the shaft. Two ball 
bearing assemblies support the shaft which rotates 
relative to the piston. 
In operation, when a torque is applied by the 
shroudlines, the shaft begins to rotate. The rotation is 
sensed by the transformer which is fed by a 400-Hz 
square-wave source. The transformer feeds a circuit 
which generates an error signal. This signal is fed to 
the active bearing. 
The bearing as shown in Figure , 2 includes a thrust 
bearing housing. Two shafts extend from this 
housing: The top one is a bearing shaft connected to 
the balloon, and the bottom shaft is connected to the 
parachute. The bearing shaft is driven through a 
sprocket-and-chain drive connected to a reversible dc 
motor. Pulses generated by the torque sensor drive the 
motor which compensates for the torque applied to 
the gondola.
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Goddard Space Flight Center. 
Code 704.1 
Greenbelt, Maryland, 20771 
Reference: TSP75-10085 
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,698,667). Inquiries concerning non-
exclusive or exclusive license for its commercial 
development should be addressed to: 
Patent Counsel 
Goddard Space Flight Center 
Code 204 
Greenbelt, Maryland 20771 
Source: David K. Studenick, Allen L. Tyler, 
and Walter Squillari
Goddard Space Flight Center 
(GSC-1 1077) 
Categories: 06 (Mechanics) 
02 (Electronics Systems) 
B75-10085
	 03 (Physical Sciences)


Torque control system

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