An improved system for use in imposing directional stability on a rocket-propelled vehicle is described. The system includes a pivotally supported engine-mounting platform, a gimbal ring mounted on the platform and adapted to pivotally support a rocket engine and an hydraulic actuator connected to the platform for imparting selected pivotal motion. An accelerometer and a signal comparator circuit for providing error intelligence indicative of aberration in vehicle acceleration is included along with an actuator control circuit connected with the actuator and responsive to error intelligence for imparting pivotal motion to the platform. Relocation of the engine's thrust vector is thus achieved for imparting directional stability to the vehicle

Perkins, H.

English

NASA Technical Reports Server

United States Patent ~ 1 9 1  
Perkins 
[ 1 I I 3,948,470 
1451 Apr. 6, 1976 
[ 5 4  1 SYSTEM FOR IMPOSING DIRECTIONAL 
VEHICLE 
STABILITY ON A ROCKET-PROPELLED 
[ 751 Inventor: Harold Perkins, Huntsville, Ala. 
[ 731 Assignee: The United States of America as 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[ 22 J Filed: July 31, 1974 
[ 2 1 ] Appl. No.: 493,359 
[52]  U.S. CI. ...........I .................................... 244/3.22 
[ 5 1 ] Int. CL2 .......................................... B64C 15/00 
[ 5 8 ]  Field of Search .................................... 24413.22 
[561 References Cited 
UNITED STATES PATENTS 
3,048.01 1 8/1962 Tumavicus ......................... 244/3.22 
3,l 13,520 12/1963 Geissler et al. .................... 244/3.22 
3,532,304 10/1970 Pyptiuk .............................. 244/3.22 
Primary Examiner-Verlin R. Pendegrass 
Attorney, Agent, or Firm-Wayland H. Riggins; L. D. 
Wofford, Jr.; John R. Manning 
[571 ABSTRACT 
An improved system for use in imposing directional 
stability on a rocket-propelled vehicle. The system in- 
cludes a pivotally supported engine-mounting plat- 
form, a gimbal ring mounted on the platform and 
adapted to pivotally support a rocket engine, an hy- 
draulic actuator connected to the platform for impart- 
ing thereto selected pivotal motion, an accelerometer 
and a signal comparator circuit for providing error in- 
telligence indicative of aberration in vehicle accelera- 
tion, and an actuator control circuit connected with 
the actuator and responsive to error intelligence for 
imparting pivotal motion to the platform, whereby a 
relocation of the engine's thrust vector is achieved for 
imparting directional stability to the vehicle. 
3 Claims, 9 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19760014187 2020-03-20T02:14:22+00:00Z
U S .  Patent ~ p r i l 6 ,  1976 Sheet 1 of 2 3,948,470 
Y 
US. Patent April 6, 1976 Sheet 2 of 2 3,948,470 
50 
CO MPAR IT0 R 
I 
FIG 7 
FIG 4 
FIG 8 
FIG 5 
3,948,470 
1 2 
whereby maximum thrust may be achieved and direc- 
tional stabilitv afforded the vehicle. SYSTEM FOR IMPOSING DIRECTIONAL 
STABILITY ON A ROCKET-PROPELLED VEHICLE 
OBJECTS AND SUMMARY OF THE INVENTION 
5 It is therefore an object of the instant invention to 
provide an improved system for achieving maximum 
thrust while imposing directional stability for rocket- 
propelled vehicles. 
It is another object to provide an improved system 
10 through which may be achieved a relocation of thrust 
vectors for accommodating both parallel and center-of- 
gravity thrust vector orientation. 
ORIGIN OF THE INVENTION 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
BACKGROUND OF THE INVENTION 
The invention generally relates to supports for rocket - It is another object to provide an improved system 
engines, and more particularly to an improved system through which it is possible to achieve directional sta- 
for pivotally displacing an engine-mounting platform, 15 bility in the event of engine failure, without requiring 
whereby a relocation of the engine’s thrust vector rela- engine shut-down or over-thrusting of residual engines. 
tive to the vehicle’s center of gravity is achieved. It is another object to provide in a system for use in 
It is, of course, recognized that maximum thrust is achieving directional stability for rocket-propelled ve- 
achievable for a multi-engine system when the thrust hicles a system through which parallel thrust alignment 
vectors are arranged in parallelism. However, for rea- 20 is accommodated, during normal engine operation, and 
sons fully appreciated by those familiar with the design center-of-gravity thrust alignment is accommodated in 
and operation of rocket-propelled vehicles, it is consid- the event engine failure is experienced in in-flight oper- 
ered to be impossible to mount multiple engines in a ation. 
manner such that the thrust vector of more than one These and other objects and advantages are achieved 
engine will pass through the center of gravity of the 25 through a pivotally supported engine mounting plat- 
vehicle and yet be oriented in parallelism with the vehi- form, adapted to receive and support a gimbaled rocket 
cle’s line of flight. This design restriction has lead to engine, and an actuator connected with the platform 
numerous problems encountered during in-flight oper- for selectively imparting pivotal motion to the platform 
ations. For example, it is not uncommon to experience in response to directional error correction signals for 
an abort resulting from failure of one engine during 30 thereby altering the orientation of the thrust vector of 
stage thrust operation. the rocket engine for thus achieving directional stabil- 
ity. In order to avoid loss of directional control, such as 
tumbling and the like, as a consequence of engine mal- 
function in a multi-engine system, it is common prac- 
tice to shut down the engine opposite the failing engine, 
or to increase the thrust of the remaining engines on 
the same side of the vehicle. Either of these alternatives 
are undesirable for obvious reasons. While it is possible 
to partially overcome this problem by pre-positioning 
thrust vectors to pass through the center of gravity, it 
has been found for vehicles having engine thrust vec- 
tors pre-positioned through some nominal center of 
gravity, two problems generally are encountered. The 
first being that the resultant thrust is never as great as 
it is for vehicles having engine thrust vectors pre-posi- 
tioned in parallelism, and secondly, the center of grav- 
ity tends to shift continuously throughout stage opera- 
tion, because of propellant depletion and similarly initi- 
ated changes in mass. Consequently, even where the 
thrust vectors are extended through a nominal center 
of gravity, it is apparent that only at one point in stage 
operation are the pre-positioned thrust vectors in fact 
extended through the center of gravity. 
It has been suggested that engine gimbal actuators 
larger than are required for nominal operational con- 
trol be provided for achieving thrust vector relocation. 
However, the mass and complexity of such gimbal actu- 
ator systems tend to render their use impractical. 
Because of the existence of these various problems 
and alternative trade-offs, designers of rocket- 
propelled vehicles continuously are faced with the de- 
cision of whether to orient thrust vectors in parallelism 
or to arrange the engines so that the thrust vectors are 
extended through the center of gravity of the vehicle. 
It is therefore the general purpose of the instant in- 
vention to provide an improved system for a rocket- 
propelled vehicle through which a selective relocation 
of the thrust vectors for rocket engines is facilitated 
BRIEF DESCRIPTION OF THE DRAWINGS 
35 FIG. 1 is a fragmented perspective view of a multien- 
gine, rocket-propelled vehicle having a cluster of 
rocket engines mounted on pivotally supported engine- 
mounting platforms included within a system embody- 
ing the principles of the instant invention. 
FIG. 2 is a perspective view of one of the engines 
shown in FIG. 1. 
FIG. 3 is a cross-sectional view taken generally along 
line 3-3 of FIG. 2. 
FIGS. 4 and 5 depict alternate operative configura- 
FIGS. 6 ,7  and 8, collectively, diagrammatically illus- 
trate the utility of the system which embodies the prin- 
ciples of the instant invention. 
40 
45 tions for one of the engines. 
FIG. 9 is a schematic view, in block diagra 
50 depicting the system. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
Referring now to the drawings, with more specificity, 
5 5  wherein like reference characters designate like or 
corresponding parts throughout the several views, 
there is shown in FIG. 1, a multi-engine, rocket- 
propelled vehicle, generally designated 10, having a 
cluster of rocket engines, designated 12, provided for 
The vehicle 10 is provided for illustrative purposes 
and forms no specific part of the instant invention. 
Therefore, a detailed description of the vehicle is omit- 
ted in the interest of brevity. However, it is to be under- 
65 stood that the vehicle 10 includes suitable supporting 
structure, not designated, for the cluster 12 of rocket 
engines 14 and that the cluster of rocket engines served 
to propel and impose in-flight directional control over 
60 propelling the vehicle. 
3,948,470 
3 4 
the vehicle 10. suitable design. It is to be understood that the sensor 
Turning now to FIG. 2, it is noted that each of the circuit 46 provides directional error signals indicative 
rocket engines 14 includes a nozzle 16 and a combus- of instantaneous aberrational acceleration experienced 
tion chamber, not shown, connected with the nozzle in by the vehicle 10 during in-flight operations. The error 
a manner well understood by those familiar with rocket 5 signals, in turn, are fed to a signal comparator circuit 
engines. Since the particular structure embodied in the 48 which serves to compare the error signal with a 
rocket engine 14 also forms no specific part of the preselected electrical signal indicative of an instanta- 
instant invention, a detailed description of the engine is neous preselected attitude for the vehicle 10. A differ- 
omitted. However, it is to be understood that the en- ence signal is derived and employed to provide driver 
gine 14, where so desired, includes a suitable combus- 10 signals to actuator control circuits 50. The circuits 50 
tion chamber supplied with bipropellant components preferably include solenoids, not shown, connected 
delivered through suitable propellant conduits desig- with selector valves and similar devices, also not 
nated 18 and 20, FIG. 3. shown, capable of controlling a delivery of fluid under 
The engine 14 is supported by a gimbal ring 22, of pressure to the actuators 42. The actuators 42 are then 
any suitable design. As shown, for illustrative purposes, 15 driven in response to fluid delivered thereto under 
the gimbal ring 22 is supported by a plurality of axially pressure. 
extensible supporting beams 24 extended from a plural- 
ity of linear, angularly spaced actuators 26. As shown, 
the gimbal ring is connected with the distal ends of the It is believed that in view of the foregoing descrip- 
beams 24 through a plurality of pivotal couplings 28 of 20 tion, the operation of the device will readily be under- 
a suitable design. The actuators 26, in turn, are rigidly stood and it will be briefly reviewed at this point. 
affixed to the periphery of an  engine-mounting plat- With a cluster 12 of engines 14 supported by a plural- 
form 30 and are paired in spaced relation 180" apart. ity of platforms 30 and mounted aboard a vehicle 10, it 
It will be appreciated that the specific configuration is possible to achieve maximum thrust with the thrust 
of the gimbal ring 22 and its supporting structure is, in 25 vectors thereof being extended in substantial parallel- 
practice, varied where desired. However, it is impor- ism with the center line of the vehicle 10, as illustrated 
tant to understand that through the gimbal ring 22 the in FIG. 6. 
rocket engine 14 is afforded pivotal motion relative to Of course, the engines 14 are supported for pivotal 
the engine-mounting platform 30 in a manner consis- displacement relative to the platform 30 through an 
tent with current design practices. The purpose of ac- 30 activation of the actuators 26 in order to achieve nor- 
commodating pivotal motion of the engine 14 relative mal guidance control. Thus the thrust vectors for the 
to the platform 30 is to facilitate engine thrust vector engines may be oriented in parallelism for achieving 
control required for normal flight operations. maximum thrust. In the event one of the engines is lost, 
The engine-mounting platform 30, in turn, is sup- as illustrated by the dotted lines in FIG. 7,  through 
ported by suitable supporting structure through which 35 malfunction or for other reasons, the line of flight for 
pivotal motion of the platform, relative to the longitudi- the vehicle 10 is vaned as indicated by the directional 
nal axis of the engine, is accommodated. As shown, the arrow in FIG. 7. immediately, this change in direction 
platform 30 is supported, in part, by a pair of legs 32 is detected within the sensor circuit 46 with a n  atten- 
projected from a rigid base 34 and connected with the dant error signal being delivered to the signal compara- 
platform 30 through ball joints 36. Of course, the con- 40 tor circuit 48. A driver signal is then delivered from the 
figuration of the base 34 may be varied, as desired. comparator circuit 48 to  an appropriate actuator con- 
Moreover, a tubular shield 38 is provided for encasing trol circuit 50 for causing the actuator 42 connected 
the propellant conduits 18 and 20. As a practical mat- therewith and connected with a platform 30 disposed 
ter, the shield 38 includes a bellows joint 40 through adjacent the lost engine to pivotally displace the plat- 
which pivotal motion of the platform 30 is accommo- 45 form 30, as indicated in FIG. 8. Of course, as the plat- 
dated. form 30 is displaced the thrust vector of the engine 
In addition to the legs 32, an hydraulic actuator 42 is supported thereby is relocated sufficiently for stabiliz- 
provided for supporting the platform 30. The actuator ing the direction of flight for the vehicle 10, as indi- 
42 preferably is mounted on the shield 38 and is affixed cated by the directional arrow in FIG. 8. 
to the base 34 in a suitable manner. The output shaft of 50 While not shown, it is to be understood that each of 
the actuator 42 is connected with the engine-mounting the engine-mounting platforms 30 for the rocket en- 
platform 30 through a ball joint, designated 44. It is to gines 14 can be repositioned during flight for simulta- 
be understood that while an hydraulic actuator is neously relocating the thrust vectors causing the thrust 
shown in the drawings, any suitable linear actuator, vectors t o  pass through the center of gravity of the 
such as a worm driven by a worm wheel o r  and the like, 5 5  vehicle 10 as excursion occurs. Thus a tracking of the 
may be employed. Moreover, the platform may be center of gravity is facilitated. 
supported by rotating cams employed where so desired. Therefore, while the system herein described has 
Of course, where only one actuator, as illustrated, is particular utility in overcoming the effects of engine 
provided pivotal motion of the platform 30 is limited to malfunction, without requiring a reduction in thrust 
angular displacement about a single axis. It is, there- 60 output, for imposing directional stability, it should be 
fore, to be understood that as many actuators as may be apparent that it is possible to  utilize the system for 
desired can be employed for supporting and pivotally achieving in-flight change of modes of operation from 
oscillating the platform 30 about multiple axes. parallel thrusting to center-of-gravity thrusting. 
As shown in FIG. 9 a sensor circuit 46 is provided for In view of the foregoing, it should be apparent that 
the vehicle 10 for detecting acceleration in directions 65 the system of the instant invention provides a practical 
angularly related to the longitudinal axis of the vehicle solution to the perplexing problem of achieving in- 
10. As a practical matter, the sensor circuit 46 includes flight reorientation of thrust vectors for rocket engines 
a plurality of angularly related accelerometers of a in a simplified and practical manner. 
OPERATION 
3,948,470 
6 
tory motion about said axis lying in a plane trans- 
versely related to the thrust axis of said rocket 
engine. 
2. In the system of claim 1, the improvement further 
comprising: 
A. sensing means for providing error signals indica- 
tive of instantaneous aberrational acceleration im- 
parted to said vehicle; 
B. a signal comparator circuit connected with said 
sensing means including means for comparing pre- 
selected intelligence signals indicative of normal 
acceleration with instantaneously derived signals 
indicative of aberrational acceleration for provid- 
ing difference signals and means responsive to said 
difference signals for providing driver signals; and 
C. a control circuit including means connected with 
said signal comparator circuit and means con- 
nected with said actuating means for receiving said 
driver signals and means responsive to said driver 
signals for activating said actuating means for im- 
parting pivotal motion to said platform for thereby 
reducing aberrational acceleration. 
3. The improvemefit of claim 1 wherein said actuat- 
5 
Although the invention has been herein shown and 
described in what is conceived to be the most practical 
and preferred embodiment, it is recognized that depar- 
tures may be made therefrom within the scope of the 
invention, which is not to be limited to the illustrative 
details disclosed. 
I claim: 
1. In a system particularly adapted for use in impos- 
ing directional control over a rocket-propelted vehicle, 
the improvement comprising: 
A. a gimbal ring adapted to receive in supporting 
relation a rocket engine having a thrust axis con- 
centrically related thereto; 
B. an engine mounting platform supported for pivotal 
motion about an axis lying in a plane transversely l 5  
related to the thrust axis of said rocket engine; 
C. means for imparting pivotal motion to said gimbal 
ring about a plurality of axes extended diametri- 
cally therethrough including an annular array of 20 
uniformly spaced linear actuators rigidly affixed to 
said platform and having a plurality of axially ex- 
tensible support beams disposed in substantial par- 
allelism and connected to said gimbal ring; and 
lo  
D. actuating means coupled with said engine mount- 25 ing means includes an hydraulic ram. 
ing platform for imparting thereto pivotal oscilla- * * * * *  
30 
35 
40 
45 
50 
60 
65 


System for imposing directional stability on a rocket-propelled vehicle

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