An air-launched sonobuoy, particularly useful for under-ice surveillance, rries a descent-retardation parachute whose lanyards activate a surface float during descent. Upon impact into an ice region, a slip-rod is jarred loose from the cannister top thus freeing the surface float, and its RF antenna, to remain above the ice while the remainder of the components deploy.

BACKGROUND OF THE INVENTION 
It can become very difficult to implant a properly working surveillance 
device in Northern waters that may be covered, or partially covered, with 
ice fields. Also, most air-launched devices do not contact the surface in 
a straight vertical manner, but rather at a slant angle of approximately 
twenty degrees, or even more, and then descend several feet below the 
surface before inflation of the surface float. When the float inflates, 
the device will generally rise to below the ice cover and lay over on its 
side. Since the RF antenna is usually contained in the surface float, this 
sideways orientation of the antenna results in poor, or no, 
communications. 
SUMMARY OF THE INVENTION 
A cylindrical, under-ice surveillance sonobuoy is air-dropped to guided 
descent via a parachute canopy attached to one end of thereof. The opening 
of the parachute activates a battery-powered circuit that causes an 
RF-antenna containing surface float to be inflated with compressed gas. 
When the weighted, bottom end of the buoy contacts an ice surface, an 
impact-sensing device releases the parachute harness and allows the 
sonobuoy components to deploy according to preset conditions. 
It is therefore an object of the present invention to provide an under-ice 
sonobuoy that will maintain its RF-antenna in a upright, above-ice 
position when deployed in an ice field. 
It is another object of the present invention to provide an under-ice 
sonobuoy that has an RF-antenna containing surface float that will inflate 
prior to termination of descent. 
It is a still further object of the present invention to provide an 
under-ice surveillance sonobuoy that uses a descent retardation parachute 
to maintain guided descent to an ice field. 
It is a still further object of the present invention to provide an under 
ice surveillance sonobuoy that uses a spring-loaded mechanical device to 
free the descent guiding parachute and allow deployment of the sonobuoy 
components. 
These and other objects, advantages and novel features of this invention 
will become apparent from the following detailed description when 
considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The under-ice surveillance sonobuoy of the present invention comprises an 
air-launched, cylindrical sonobuoy, containing components, such as a 
hydrophone, an electronics sensor package, a cable pack and an RF 
antenna-containing surface floats packed inside cannisters. FIG. 1 shows a 
front elevational view of the under-ice surveillance sonobuoy 12, while 
FIG. 2 shows a front elevational view with portions of the outer tubular 
shell 14 cutaway to show details of the inner sonobuoy components. Shell 
14 is a slender, tubular shell with various sonobuoy components arranged 
inside an inner cannister, such as 72 (as seen in FIG. 5) and having at 
one end (the lower end when looking at FIGS. 1 and 2) a sealing cap 18 and 
an impact weight 21 attached thereto, and at the opposite end (the upper 
end when looking at FIGS. 1 and 2) a standard wind-flap, schematically 
represented at 24, connected as at 25, covering the descent retardation 
means 26. As seen in FIG. 3, the descent retardation means is a 
larger-than-standard parachute canopy 29 attached via longer-than-standard 
lanyards 31 to a spring steel harness belt 33, as will be described, and 
activated as is known, by a parachute release spring. 
FIG. 3 shows a side elevational view of buoy 12 after canopy 29 has been 
inflated, after wind-flap 24 (not shown) has activated and allowed the 
parachute release mechanism to push canopy 29 into the windstream. Risers 
38 are made longer than usual to allow a buoy float 30 to inflate while 
buoy 12 is descending. As shown, a clip 36 has been pulled by canopy line 
37 from the electronic inflation circuitry 40, shown schematically in FIG. 
6. Circuitry 40 reacts, once clip 36 is pulled away from a 
spring-activated, normally-open switch 42, to apply power from a battery 
47 to a squib 46 that drives a pin into a source of compressed gas 45 to 
allow inflation of buoy float 30, which carries an RF antenna 35. 
Circuitry 40 receives its power from battery 47 via electrical connection 
48, as is known, and antenna 35 is connected (not shown) to the rest of 
the sonobuoy components. 
The impact sensing capability of buoy 12 comes from the compression of the 
bottom of buoy 12 and weight 21, which, because of its heavier weight than 
the remaining buoy parts, is the first surface to make contact when buoy 
12 hits an ice field 15 (as shown in FIG. 4). A very inflexible J-rod 52 
is securely attached to weight 21, as at 50, adjacent the lowermost 
surface of weight 21 and sits adjacent the outside surface of shell 14. 
J-rod 52 is so named because of the hook 54 at the uppermost end that 
constrains harness belt 33, as will be explained. Rod 52 has a protusion 
56, (as seen in FIG. 2a) at its mid-point, that is normally seated inside 
cavity 57 in the side of shell 14, and normally remains adjacent the side 
of shell 14. The J-hook end of rod 52 fits inside of clasping means, or 
the inter-layered ends 62,63, of belt 33, locking into loops 62a amd 63a, 
as seen in FIGS. 2a and 2b. Belt 33, when closed around the upper end of 
shell 14 and secured by the J-hook 54, is fastened beneath a plurality of 
projections 67, as seen in FIG. 2C. Projections 67 can be small, 
rectangularly-shaped areas pressed outwardly along parallel edges, or 
other similar means, and serve to hold belt 33 against shell 14 as long as 
J-hook 54 remains in place. 
Sonobuoy 12 is designed to allow float 30 to be inflated while the buoy is 
descending through the air. Impact weight 21 and end 50 of J-rod 52 
contact the ice surface first and the impact jolt, or force, on end 50 
initially compresses the bottom of buoy 12 and starts an initial 
longitudinally and vertically directed movement of rod 52. As shown by the 
diagrammatic arrow in FIG. 4a, the initial upward movement causes 
protusion 56 to bump up against the top surface of cavity 57, and, because 
the top surface has been sloped accordingly, then slide outwardly away 
from cavity 57. This combination movement is repeated by J-hook 54, (as 
can be seen in FIG. 4b) since J-rod 52 is structurally inflexible, and the 
hook 54 is thereby, first, forced out of the binding position with loops 
62a,63a and then away from that position. As shown in FIG. 4, as soon as 
J-hook 54 is removed, the spring force in harness belt 33 causes belt 33 
to spread open, thereby freeing means 26 from shell 14. 
As seen in FIG. 5, once belt 33 springs free from shell 14, the continuing 
downward momentum of shell 14 carries it away from the inner cannister 72 
(optional) containing sonobuoy components, as is known. 
Obviously, other embodiments and modifications of the present invention 
will readily come to those of ordinary skill in the art having the benefit 
of the teachings presented in the foregoing description and drawings. It 
is therefore to be understood that various changes in the details, 
materials, steps and arrangement of parts, which have been described and 
illustrated to explain the nature of the invention, may be made by those 
skilled in the art within the principle and scope of the invention as 
expressed in the appended claims.