System and Method for Detecting the Amount of Stabilizer Degradation in Solid Rocket Propellant

• US 20140022551A1
• Filed: 07/19/2012
• Published: 01/23/2014
• Est. Priority Date: 07/19/2012
• Status: Active Grant

• Current Assignee: General Opto Solutions LLC, United States Secretary of the Army
• Original Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Inventors: Edwards, Eugene, Brantley, Christina L., Luo, Fang, Ruffin, Paul B.
• Granted Patent: US 8,842,281 B2
• Time in Patent Office: Days
• US Class Current: 356/432
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence
• CPC Class Codes: G01N 21/59 Transmissivity G01N21/25 takes precedence

Abstract

A spectrometric system, including: a solid rocket fuel; an illuminating source including at least two wavelengths within a spectral range from 100 nm to 200,000 nm, a first wavelength or range of wavelengths having a distinguishably greater or lesser absorbance for the stabilizer than for components of the propellant, and a second wavelength or range of wavelengths having an absorbance for the stabilizer not distinguishably different than the absorbance for the components of the propellant, an illuminating fiber to illuminate a surface of a solid rocket fuel; a collecting fiber to collect back scattered, reflected or transmitted light being given off from the surface of the solid rocket fuel; and a spectrometer to determine the light intensities of the two wavelengths of the back scattered, reflected or transmitted light collected.

Claims

1. A method of determining an amount of degradation of stabilizer in solid rocket fuel by either back scattered, reflected or transmitted light, the solid rocket fuel including nitrate-ester-based propellant and stabilizer, the stabilizer being selected from the group consisting of 2-methyl-4-nitroaniline (MNA) and 1,2,4-butanetriol trinitrate (BUN), the method comprising the steps of:

passing light from an illuminating source, the light including at least two wavelengths of light within a spectral range from 100 nm to 200,000 nm, a first wavelength or range of wavelengths producing a distinguishably greater or lesser light absorbance for the stabilizer than for components of the propellant, and a second wavelength or range of wavelengths producing a light absorbance for the stabilizer not distinguishably different than for the components of the propellant, the light having passed through a light-directing device including a lens and into an illuminating fiber light-entering end and through the illuminating fiber;

illuminating a light-contacting portion of a surface of the solid rocket fuel with light coming out of the illuminating fiber light-exiting end, and the illuminating fiber light-exiting end either contacting or coming into close proximity to the light-contacting portion, the illuminating fiber light-exiting end illuminating the light-contacting portion of the surface with the light from the illuminating source;

collecting backscattered, reflected or transmitted light being given off from the surface of the solid rocket fuel in response to the illuminating fiber light-exiting end illuminating the light-contacting portion of the surface, wherein the collecting of light is by a collecting fiber light-entering end either contacting or coming into close proximity to the surface of the solid rocket fuel where back scattered or transmitted light is being given off;

or the collecting fiber light-entering end gathering light from a light-collecting device near the surface of the solid rocket fuel, the light-collecting device receiving reflected light being given off from the light-contacting portion of the surface, wherein the light-collecting device includes a device selected from the group consisting of a lens, a mirror and an integration sphere;

passing light through the collecting fiber and out a collecting fiber light-exiting end through the light-directing device and into a spectrometer; and

determining with the spectrometer the light intensities of the back scattered, reflected or transmitted light being given off from the surface of the solid rocket fuel.

2. The method according to claim 1, wherein the nitrate-ester-based propellant is a double-base NC/NG propellant comprised of nitrocellulose, nitroglycerin and KNO₃.

3. The method according to claim 2, wherein the nitrate-ester-based propellant further comprises carbon black.

4. The method according to claim 1, wherein the stabilizer is MNA and the first wavelength or range of wavelengths is from a blue light having at least one wavelength in a range from 450 to 490 nm, and the second wavelength or range of wavelengths is from a green light having at least one wavelength in a range from 501 to 543 nm.

5. The system according to claim 4, wherein the first wavelength is 473 nm and the second wavelength is 532 nm wavelength.

6. The method according to claim 1,

wherein, in the illuminating step, when the illuminating fiber light-exiting end contacts or is in close proximity to the surface of the solid rocket fuel and delivers light to the light-contacting portion, the light penetrates into and forms back scattered light beneath the surface of the solid rocket fuel and the back scattered light exits the solid rocket fuel at a light-collecting portion of the surface of the solid rocket fuel;

and wherein, in the collecting step, the collecting fiber light-entering end contacts or is in close proximity to the light-collecting portion of the surface of the solid rocket fuel and collects back scattered light exiting the light-collecting portion.

7. The method according to claim 6,

wherein, at the surface of the solid rocket fuel, the light-contacting portion of the surface and the light-collecting portion of the surface are at a distance less than 1 mm apart, and the illuminating fiber light-entering end and the collecting fiber light-exiting end are substantially parallel to each other in an area proximate to the light-contacting and light-collecting portions of the surface of the solid rocket fuel.

8. The method according to claim 1,

wherein, in the illuminating step, when the illuminating fiber light-exiting end delivers to-be-reflected light to the light-contacting portion of the surface of the solid rocket fuel, the illuminating fiber light-exiting end does not contact the light-contacting portion of the surface but is in close proximity to the light-contacting portion, the to-be-reflected light being reflected back off the light-contacting portion of the surface;

wherein, in the collecting step, when the light is reflected back off the light-contacting portion of the surface of the solid rocket fuel, the light-collecting device, not contacting the light-contacting portion but in close proximity to the light-contacting portion, collects the reflected light from the light-contacting portion of the surface of the solid rocket fuel, the reflected light from the light-contacting portion hitting the light-collecting device at more than one angle;

and wherein, the light-collecting device directs light to the collecting fiber light-entering end, so that the light directed from the light-collecting device enters the collecting fiber light-entering end.

9. The method according to claim 1,

wherein, in the illuminating step, when the illuminating fiber light-exiting end contacts or is in close proximity to the light-contacting portion of the surface of the solid rocket fuel and delivers light to the light-contacting portion, the light penetrates the surface, becoming an internally transmitted beam close beneath the surface of the solid rocket fuel from the light-contacting portion to a light-collecting portion of the surface;

and wherein, in the collecting step, the collecting fiber light-entering end contacts or is in close proximity to the light-collecting portion of the surface of the solid rocket fuel and collects light from the internally transmitted beam transmitted from the surface at the light-collecting portion.

10. A spectrometric system that measures back scattered, reflected or transmitted light, comprising:

a solid rocket fuel surrounded by a metal shell, the solid rocket fuel including a nitrate-ester-based propellant and a stabilizer selected from the group consisting of 2-methyl-4-nitroaniline (MNA) and 1,2,4-butanetriol trinitrate (BUN);

a spectrometer to determine the light intensities of the green wavelength light and of the blue wavelength light of back scattered, reflected or transmitted light;

an illuminating source giving off light including at least two light wavelengths within a spectral range from 100 nm to 200,000 nm wavelengths, a first wavelength or range of wavelengths producing a distinguishably greater or lesser light absorbance for the stabilizer than for components of the propellant, and a second wavelength or range of wavelengths producing a light absorbance for the stabilizer not distinguishably different than for the components of the propellant;

a light-directing device including a lens through which light passes in a first direction toward the solid rocket fuel and in an opposite direction toward the spectrometer;

an illuminating fiber including a) an illuminating fiber light-entering end to collect light coming from the illuminating source through the light-directing device;

b) the illuminating fiber itself through which the light travels; and

c) an illuminating fiber light-exiting end to illuminate a light-contacting portion of a surface of a solid rocket fuel by either contacting or being in close proximity to the light-contacting portion; and

a collecting fiber including a) a collecting fiber light-entering end to collect back scattered, reflected or transmitted light being given off from the surface of the solid rocket fuel or from a light-collecting device near the surface of the solid rocket fuel;

b) the collecting fiber itself through which the light travels; and

c) a collecting fiber light-exiting end to deliver light to and through the light-directing device and toward the spectrometer;

wherein the light-collecting device receives reflected light being given off from the contacting portion of the surface, the light-collecting device including a device selected from the group consisting of a lens, a mirror and an integration sphere.

11. The system according to claim 10, wherein the nitrate-ester-based propellant is a double-base NC/NG propellant comprised of nitrocellulose, nitroglycerin and KNO₃.

12. The system according to claim 11, wherein the double-base NC/NG propellant further comprises carbon black.

13. The system according to claim 10, wherein the stabilizer is MNA and the first wavelength is from a blue light having at least one wavelength in a range from 450 to 490 nm and from a green light having at least one wavelength in a range from 501 to 543 nm.

14. The system according to claim 13, wherein the first light wavelength is 473 nm and the second light wavelength is 532 nm.

15. The system according to claim 10, further comprising an optical port in the metal shell, the optical port being positioned between the light-directing device and the surface of the solid rocket fuel, the optical port including an opening in the metal shell through which the illuminating fiber and the collecting fiber pass into a space between the metal shell and the surface of the solid rocket fuel to give the illuminating fiber light-exiting end and the collecting fiber light-entering end contact or close proximity with the surface of the solid rocket fuel.

16. The system according to claim 10, wherein the illuminating fiber light-exiting end contacts or is in close proximity to the light-contacting portion of the surface of the solid rocket fuel and the collecting fiber light-entering end contacts or is in close proximity to a light-collecting portion of the surface of the solid rocket fuel;

and wherein the light-contacting portion and the light-collecting portion are at a sufficient distance from each other to allow light from the illuminating fiber light-exiting end to penetrate the surface at the light-contacting portion and form back scattered light inside the solid rocket fuel between the light-contacting portion and the light-collecting portion, the back scattered light emerging from the light-collecting portion to the collecting fiber light-entering end.

17. The system according to claim 16, wherein the light-contacting portion and the light-collecting portion are less than 1 mm apart on the surface of the solid rocket fuel;

and wherein the illuminating fiber light-exiting end and the collecting fiber light-entering end are substantially parallel to each other in an area proximate to the light-contacting portion and the light-collecting portion of the surface of the solid rocket fuel.

18. The system according to claim 17, wherein the light-contacting portion and the light-collecting portion are at most 200 microns apart from each other.

19. The system according to claim 10, wherein the illuminating fiber light-exiting end is in close proximity but does not contact the light-contacting portion of the surface of the solid rocket fuel, and the light-collecting device also is in close proximity to but does not contact the light-contacting portion;

wherein the light-collecting device collects reflected light from the light-contacting portion of the surface of the solid rocket fuel, the reflected light travelling from the light-contacting portion and entering the light-collecting device at more than one angle; and

wherein the collecting fiber light-entering end is positioned with respect to the light-collecting device, so that the reflected light collected in the light-collecting device is directed to the collecting fiber light-entering end.

20. The system according to claim 10, wherein the illuminating fiber light-exiting end contacts or is in close proximity to the light-contacting portion of the surface of the solid rocket fuel, and the collecting fiber light-entering end contacts or is in close proximity to the light-collecting portion of the surface of the solid rocket fuel;

wherein the light is directed to the light-contacting portion of the surface from the illuminating fiber light exiting end and the light becomes an internally transmitted beam transmitted from the light-contacting portion to the light-collecting portion beneath the surface of the solid rocket fuel; and

wherein the internally transmitted beam is transmitted from the light-collecting portion of the surface and enters the collecting fiber light-entering end.