US3200750A

US3200750A - Insulating device

Info

Publication number: US3200750A
Application number: US180055A
Authority: US
Inventors: Dale L Burrows
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-03-15
Filing date: 1962-03-15
Publication date: 1965-08-17
Anticipated expiration: 1982-08-17

Description

1965 D. L. BURROWS 3,200,750

INSULATING DEVICE Filed March 15, 1962 FIG. I

FIG. 2

Dale L. Burrows, F|G 3 INVENTOR.

BY 4. %6Z.-

4.51 jaw w. SOLIQ United States Patent 3,20%,750 INSULATING DEVICE Dale L. liurrows, Huntsviile, Ala, assignor to the United States of America as represented by the Secretary of the Army Filed Mar. 15, 1962, Ser. No. 180,055 15 Claims. (Cl. 10292.5) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates broadly to missiles which travel at significant velocities high in the atmosphere, and beyond the atmosphere, and more particularly to insulating the nose portion of the missile for the purpose of rendering the surface resistant to high temperatures and thermal shocks encountered particularly upon re-entry to the atmosphere.

In the past a mixture of resin or some other ablative material and fibers has been coated on the nose portion of re-entry missiles in order to protect the missile from extremely high temperature due to friction during reentry of the missile into the atmosphere. However certain disadvantages are encountered when the mixture of fibers and an ablative material is used to protect the missile during reentry. For example, when the ablative material is heated a gas is generated causing bubbles and pits to form on the surface of the coating, these bubbles and pits present an uneven surface to the fluid flow over the nose portion of the missile during re-entry into the atmosphere and thus fail to provide uniform heat dissipation. Furthermore at the location of the bubbles and pits greater heat is generated due to the increase in friction. These problems are overcome in the present invention by disposing a brush-like arrangement of fibers on a base which in turn is attached by some suitable adhesive material to the nose portion of the missile.

In view of these facts, an object of this invention is to provide a missile having a nose portion that has a high resistance to heat.

Another object of this invention is to provide a missile having a nose portion which has high resistance to the stress of thermal shock.

A further object of this invention is to provide a missile having a nose portion which has uniform ablation characteristics.

A still further object of this invention is to provide insulation having an appreciable reduction in weight for a required insulating value.

The invention will be more readily understood from the following description taken in conjunction with the accompanying drawing, in which:

FIGURE 1 is a plan view of a missile with the insulation on its nose portion.

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1 showing the insulating material on the nose portion of the missile.

FIGURE 3 is an enlarged plan view of an insulating element showing the arrangement of some of the bristles on the element.

In the drawings, wherein for the purpose of illustration there is shown a preferred embodiment of the in vention, in which the numeral 4 designates a missile comprising a shell 6 and an insulated nose portion 8.

The nose portion may be constructed in sections of structural plate steel or other suitable material shaped to the desired configuration. Attached to plate 6 by cement It) or some other suitable adhesive material is a plurality of base blocks 12 of ceramic material or resin bonded fibers; to the outside of which is attached by a bonding fiilififfifi Patented Aug. 17,1965

process or cement a brush-like coating of bristles 14. A refractory insert 1c is disposed on the foremost point of the nose since bristles placed at this point would tend to incline backwards during re-entry and expose the missile shell to high temperatures. Furthermore the point of greatest aerodynamical heating is not at the stagnation point.

The bristle or fiber arrangement may be composed of fibers of different materials or of fibers which are all of the same material. However, to obtain best results the fibers used should be selected from materials having both high aerodynamic heating insulator properties and high thermal conduction insulating properties. Preferred materials with these properties include fibrous, filamentary or bristle like materials of synthetic origin .and particularly those fabricated from ceramic and refractory materials such as oxides of magnesium, silicon, thorium, and aluminum.

Along with the fibers of the above materials and intimately associated with them it is sometimes desirable to use fibers made from other materials having the follow ing properties: (1) good heat sink or heat absorption qualities, (2) uniform endothermic decomposition characteristics and (3) high thermoconduction insulator properties and, in addition, having a decomposition temperature somewhat lower than the base blocks referred to above, in order to derive the beneficial endothermic effects. However, it is not necessary that the bristles have a decomposition temperature lower than the blocks if the fibers are long enough so that the temperature drop through the fibers or bristles is great enough to prevent damage to the resin or ceramic blocks. In general, suitable materials having the above mentioned properties are found among long chain resinous materials such as melamine, phenolic resins and nylons. Mixtures of fibers from both classes of the above materials may be varied when desired as may also the length of the fibers. In selecting the materials to be used and in determining the length of the fibers, the heat protection requirements of the particular trajectory under consideration would be the governing factor. Thus for some trajectories an assortment of about ten percent of the resinous material with the remainder-selected from one of the ceramic materials mentioned would be suitable; As stated above fibers made from the ceramic materials alone may be advantageous over a mixture of the ceramic materials with the resinous materials because in the case of certain trajectories it may be desirable that the ablation should proceed smoothly without gasifying effects disturbing the surface flow, i.e. where low Reynolds number trajectories are contemplated it would be advantageous to use the ceramic fibers having smooth ablation characteristics. Fibers having uniform ablation characteristics and hence producing a smoother external surface would induce a greater area of laminar flow thus resulting in a much lower heat transfer than occurs when a combination of the fibrous materials are used which generate a more turbulent flow.

The bristles or fibers although contacting each other would have a network of air cell between them (see magnified View in FIGURE 3) and inasmuch as the fibers are slanted to the surface a greater resistance to heat transfer is provided than if the void were filled with a bonding agent such as resin. The major heat path would be down or along each fiber and the inclination of the fibers from the normal would effectively increase the heat path length and thus increase the insulating value for a given thickness of the insulation material.

From an aerodynamic point of view the inclination of the fibers (as shown in FIGURE 2) would be beneficial inasmuch as the surface shear forces would tend to keep the bristles brushed back and hence maintain the aerodynamic surface. The individual bristles are so fine that as far as the boundary layer is concerned the surface is essentially smooth. Such a surface may actually promote an increase of laminarfiow very much in line with the phenomena occurring on the feathered surfaces of birds. Under the conditions of surface melting the surface hould become smoother and ablation would be a uniform process due to the homogeneous nature of the closely packed bristled surface. Inasmuch as each bristle i welded, fused or bonded to a base the whole insulating surface would actually withstand the aerodynamic forces (especially during the ablating process) much better than a matted or stranded arrangement of fibers impregnated with resin. Also the possible aerodynamic disadvantage of bubbling or sputtering of resin will be avoided.

It is to be noted that the invention is not limited to bristles on a plurality of blocks cemented to a missile shell but the bristles could have their internal ends anchored on or in a common base which covers the entire nose of the missile (with the exception of the solid refractory insert at the foremost part of the nose).

. The following invention is claimed:

1. A heat resistant device comprising:

(a) a shell;

(b) means disposed on said shell for protecting said shell from high temperatures,

() said means including a brush-like arrangement of fibers, and

(d) said brush-like arrangement of fibers being so oriented and so fine as far as a boundary layer is concerned that the surface thereof i essentially smooth to promote an increase of laminar flow very much in line with the phenomena occurring on the feathered surfaces of birds.

2. The device as set forth in claim ll wherein said fibers are of ablative material.

3. The device as set forth in claim 1 wherein said fibers are made of material having both high aerodynamic heating insulator properties and high thermal conduction insulating properties.

4. A missile comprising:

(a) a nose portion;

(b) an adhesive material disposed on said nose portion;

(c) a plurality of insulating elements attached to said adhesive material; and

(d) a brush-like arrangement of fibers disposed on each of said insulating elements.

5. The device as set forth in claim 4 wherein said fibers are of ablative material.

6. The device as set forth in claim 4 wherein said fibers and said insulating elements are made of material having both high aerodynamic heating insulator properties and high thermal conduction insulating properties.

7. A missile comprising:

(a) a nose portion;

i (b) an adhesive material disposed on said nose portion; (c) a plurality of insulating elements attached to said adhesive material; and (d) a brush-like arrangement of fibers tilted away from the front of said nose portion and disposed on each of said insulating elements. 8. A missile comprising: (a) a nose portion; (b) an adhesive material disposed on said nose portion; (c) a plurality of insulating elements attached to said adhesive material; (d) a brush-like arrangement of fibers disposed on each of said insulating elements; and (e) a solid refractory insert mounted on the foremost part of said nose portion.

9. The device as set forth in claim 7 wherein said fibers are of ablative material.

10. The device as set forth in claim 7 wherein said fibers and said insulating elements are made of material having both high aerodynamic heat insulator properties and high thermal conduction insulating properties.

1.1. The device of claim 19 wherein a solid refractory insert is mounted on the foremost part of said nose portion.

12. A missile comprising: a nose portion having a relatively smooth and continuous. outer surface; a missile shell having an outer surface; means securing said nose portion to said shell so as to form a continuous surface of said nose portion outer surface and said shell outer surface; and means secured to said relatively smooth and continuous outer surface of said nose portion for protecting said nose portion from high temperatures and including a brush-like arrangement of fibers.

13. The device as set forth in claim 12 wherein said last mentioned means further includes an adhesive material disposed on said nose portion, a plurality of insulating elements attached to said adhesive material, and said brush-like arrangement of fibers being secured to said insulating elements. 7

14. The device as set forth in claim 12 wherein said fibers are tilted away from the front of said nose portion.

15. The device as set forth in claim 14 wherein a solid refractory insert is mounted on the foremost part of said nose portion.

References Cited by the Examiner UNITED STATES PATENTS 1/56 Nicholson 1l7-l6 11/61 Parlanti 102-925 OTHER REFERENCES BENJAMIN A. BORCHELT, Primary Examiner.

ARTHUR M. HORTON, Examiner.

Claims

1. A HEAT RESISTANT DEVICE COMPRISING: (A) A SHELL; (B) MEANS DISPOSED ON SAID SHELL FOR PROTECTING SAID SHELL FROM HIGH TEMPERATURES, (C) SAID MEANS INCLUDING A BRUSH-LIKE ARRANGEMENT OF FIBERS, AND (D) SAID BRUSH-LIKE ARRANGEMENT OF FIBERS BEING SO ORIENTED AND SO FINE AS FAR AS A BOUNDARY LAYER IS CONCERNED THAT THE SURFACE THEREOF IS ESSENTIALLY SMOOTH TO PROMOTE AN INCREASE OF LAMINAR FLOW VERY MUCH IN LINE WITH THE PHENOMENA OCCURRING ON THE FEATHERED SURFACES OF BIRDS.