Parachute trajectory control

A parachute has its suspension lines divided into groups, each group connected to the load through a linear actuator. During descent of the parachute, foreshortening of an actuator or of any group of adjacent actuators causes the parachute trajectory to move in the direction of the foreshortened actuator. Multiple parachutes connected to a single load, with each parachute being connected to the load through an actuator, can similarly have their trajectory controlled. The trajectory of the parachute can also be changed by a system of normally foreshortened actuators which lengthen by actuation. Simultaneous, rapid shortening of all actuators just before ground impact can be used to reduce the descent velocity at ground impact.

SUMMARY OF THE INVENTION 
This invention is a control for the trajectory of a descending, non-gliding 
parachute. Another type of parachute, the gliding parachute, already uses 
methods for steerable gliding. Such gliding parachutes are used for the 
delivery of cargo or personnel over a horizontal distance as they glide 
downward. 
Low-glide parachutes, generally defined as having a glide ratio (horizontal 
velocity/vertical velocity) less than 1.0, are also known to be steered. 
Non-gliding parachutes can be modified for a low-glide characteristic. 
However, continuous gliding is not always necessary or desired. This 
invention can create gliding as needed. 
This invention applies to the non-gliding type of parachute. It can be used 
to control the trajectory of non-gliding parachutes for the purpose of 
improving landing position accuracy. 
This invention provides a control means for causing a descending, 
non-gliding parachute to move horizontally in a particular direction, thus 
changing its trajectory. The controls of this invention use known means 
for electronic guidance and navigation connected to the mechanical means 
of this invention to modify a given trajectory of a descending parachute 
towards a desired landing location. The invention can be applied to a 
single parachute or to a group of parachutes suspending the load. 
The invention uses long-stroke linear actuators such as (1) pneumatic 
cylinders or pneumatic muscle devices actuated by compressed gas through 
solenoid valves or (2) electro-mechanical actuators such as screw motors 
or winches. The pneumatic muscle device is a woven tube surrounding a 
bladder. The weave of the surrounding tube is such that when the tube is 
forced by fluid pressure in the bladder to expand, its length becomes 
foreshortened. This foreshortening upon being pressured or lengthening 
upon being de-pressured is the linear actuation mode of the device. The 
pneumatic muscle is operated by control means which can include altitude 
sensing, a receiver of control signals from a source remote to the 
parachute system and a control means for the pressure within the bladder 
of a given pneumatic muscle device. 
The suspension lines, attached to the parachute canopy around its 
perimeter, are divided into groups. The lines of each group are attached 
to a single linear actuator. The linear actuators, each holding a group of 
suspension lines, have their lower ends connected together at the payload 
or onto the riser system which leads to the payload. Horizontal motion 
develops from the section of the suspension lines where the suspension is 
foreshortened or lengthened by one or more actuators, thus tilting the 
skirt of the parachute. The tilting causes horizontal motion in the 
direction of the lowest edge of the parachute. 
In an alternative form of the invention, all actuators are initially 
foreshortened. Steering is accomplished by the lengthening of one or more 
actuators on the side opposite the desired direction of motion. 
A second alternative form of the invention is for use with multiple 
parachutes, known as a cluster, connected to a single payload. One linear 
actuator each is attached to all the suspension lines of each parachute in 
the cluster. When one or more actuators are shortened or lengthened 
relative to the others, an asymmetric flow pattern about the entire 
assembly is established which causes the payload to develop horizontal 
velocity. 
DeHaven has already presented the case of a parachute soft landing using 
rapid retraction by a single linear actuator connected between the payload 
and the parachute. The use of multiple actuators in unison in a parachute 
system to reduce the impact velocity of the payload is part of this 
invention. However, our invention is more than a logical extension of 
DeHaven because of the following unexpected result: In our use of the 
concept of foreshortening of all lines we combine smaller parachutes with 
a soft landing system in order to provide a system with higher horizontal 
velocity in the guidance phase of the descent. Smaller parachutes have a 
faster descent velocity and consequently a higher horizontal velocity 
under trajectory control. The higher horizontal velocity is important for 
overcoming wind effects on the parachute trajectory. However, the result 
can be an excessive impact velocity. The impact velocity of our system for 
a parachute with high descent velocity is reduced to a feasible, lower 
impact velocity by providing means for rapid, simultaneous retraction of 
all of the linear actuators the instant before impact of the load with the 
ground.

DETAILED DESCRIPTION 
FIG. 1 shows a parachute system 1 with its canopy 25 and with its load 2. 
The periphery of the canopy is 29. The multiple suspension lines 3 are 
seen to be formed into three groups 4, 5, and 6, each of which is attached 
to an actuator 7, 8 and 9 at 28, 27 and 26 respectively. In the view shown 
actuator 9 is actuated (shortened) and the canopy 25 is seen to be tilted 
in the direction of the actuator 9. The three actuators each attach to the 
payload harness 60 connectors at 51, 52 and 53. The payload harness 60 is 
attached to the payload 2 at three connectors 61 being one of the three. 
An arrow is included in the drawing to point the movement direction of the 
parachute motion caused by the foreshortened actuator 9. The box 62 
contains navigation and guidance means. 
The overall length of the actuators 7, 8, and 9 and of their stroke would 
be a function of the characteristics of the particular actuator being used 
and the detailed design goals for the degree of steering of the parachute. 
FIG. 2 shows a view looking up at the canopy 25 from the plane of the upper 
actuator attachments 26, 27 and 28. Single arrows indicate the horizontal 
direction of movement of the parachute which would be caused by 
foreshortening of any one group of suspension chords. Double arrows 
indicate the direction of horizontal movement of the parachute that would 
be caused by two of the three groups of suspension lines being 
foreshortened. The direction is always to the side where the 
foreshortening occurs. 
FIG. 3 shows a trajectory-controlling parachute system 10 in which the load 
11 is carried by a group of parachutes 13, 14 and 15. The parachutes 13, 
14, and 15 are connected each to an actuator 16, 17 or 18. The action 
portrayed is of the load 11 moving in the direction of the arrow as caused 
by the foreshortening of actuator 16, the remaining actuators 17 and 18 
being kept in their extended, non-actuated length. 
FIG. 4 appears identical to FIG. 1. However, FIG. 4 is presented to point 
out a distinctly different case than that of FIG. 1. FIG. 4 represents the 
case where, to begin with, all three actuators are foreshortend. The 
parachute system 63 then receives its directional change by a lengthening 
of one or more of those actuators for the suspension lines which are 
positioned around the canopy on the side opposite the desired direction of 
movement. In other words the parachute drop starts with all actuators 
foreshortened. Just preceding the event seen in FIG. 4, actuators 37 and 
38 were lengthened while actuator 36 has remained in its original 
foreshortened length. As in FIG. 1, movement is to the right. 
The schematic drawing of FIG. 5 shows the control and power connections. 
The controls for navigation and guidance are contained in the box 39. The 
power supply for the computer in 39 is contained in 40. The power supply 
41 drives the actuators 7, 8, and 9. The units 42, 43, and 44 can be 
solenoid valves if the actuators 7, 8 and 9 are pneumatic. If the 
actuators are electromechanical, 42, 43, and 44 would be electrical 
drives. 
In FIG. 6 the elastomeric tube 47 is held within the braided tube 46 and 
both are held within the sealing end cap 45. Fluid flow to the unit is 
introduced through the tube 49. The attachment fittings at the ends are 50 
and 51. The cross-sectional view details the calmping and sealing design 
of the end caps.