Prosecution Insights
Last updated: April 19, 2026
Application No. 18/717,599

HYBRID ROCKET ENGINE FUEL GRAINS WITH COMPOSITIONAL VARIATIONS

Non-Final OA §103
Filed
Jun 07, 2024
Examiner
FELTON, AILEEN BAKER
Art Unit
1734
Tech Center
1700 — Chemical & Materials Engineering
Assignee
Firehawk Aerospace Inc.
OA Round
1 (Non-Final)
51%
Grant Probability
Moderate
1-2
OA Rounds
4y 6m
To Grant
67%
With Interview

Examiner Intelligence

Grants 51% of resolved cases
51%
Career Allow Rate
223 granted / 435 resolved
-13.7% vs TC avg
Strong +16% interview lift
Without
With
+15.5%
Interview Lift
resolved cases with interview
Typical timeline
4y 6m
Avg Prosecution
51 currently pending
Career history
486
Total Applications
across all art units

Statute-Specific Performance

§101
1.1%
-38.9% vs TC avg
§103
63.7%
+23.7% vs TC avg
§102
16.5%
-23.5% vs TC avg
§112
17.3%
-22.7% vs TC avg
Black line = Tech Center average estimate • Based on career data from 435 resolved cases

Office Action

§103
DETAILED ACTION Notice of Pre-AIA or AIA Status The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA . Claim Rejections - 35 USC § 103 The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action: A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made. Claims 79-94 are rejected under 35 U.S.C. 103 as being unpatentable over Jones (2017/0073280) in view of Danforth (2019/0002362). Regarding claim 79 and 86-94, Jones discloses a fuel grain for a hybrid rocket engine (abstract), the fuel grain comprising: multiple, concentric layers of fuel grain material defining a combustion port extending through a body of the fuel grain (para [0032], [0082]: An exemplary solid fuel grain suitable for use in a hybrid rocket engine and made in accordance with the present invention has a generally cylindrical shape and defines a center port that runs linearly through its length. The solid fuel grain is formed as a fused stack of layers with each layer comprising a plurality of abutting, fused concentric generally circular, disposed beads of material suitable as a hybrid rocket fuel maintain combustion along the exposed surface area of the center port 46 wall), in which each layer comprises multiple beads of fuel grain material, in which the multiple beads in a given layer are disposed adjacent to one another and bonded together, in which adjacent concentric layers are bonded together (para [0058], [0072]: layer formed as a series of abutting fused concentric ring-shaped beads additive manufacturing process has commenced form small diameter concentric ring-shaped beads of material; para [0074]: As each ring-shaped beaded structure cools and solidifies, a fusion bond develops between the concentric ring-shaped beaded structure, and as each plurality of such ring-shaped beaded structures forming layers cool and solidify, likewise a fusion bond develops between the layers), in which each bead of fuel grain material comprises a polymer based rocket fuel material para [0034]: a thermoplastic fuel formulation such as 95% by mass Acrynotrile Butadiene Styrene (ABS) and 5% NmX-01 nanocomposite aluminum). Jones does not specifically disclose in which a composition of the fuel grain material varies along a radius of the fuel grain. However, Danforth discloses a fuel grain for a hybrid rocket engine (para [0003], [0009], [0012]: the fuel includes a first thermoplastic continuous material, with a metal additive oxidizer additive includes droplets of oxidizer material (it is noted that in a hybrid rocket engine oxidizer is typically in liquid or vapor state and fuel is in solid or semi-solid state per Applicant's current specification at para [002])) in which a composition of the fuel grain material varies along a radius of the fuel grain (para [0044]: variations in the regions 12 and 14 throughout the element 10. The relative amounts of fuel and oxidizer may be varied at different locations within the element 10 by varying the size, composition, and/or placement of the regions 12 and 14. For example, at different longitudinal (axial) and/or radial locations within the element). It would have been obvious to one of ordinary skill in the art to use the composition of the fuel grain material that varies along a radius of the fuel grain of Danforth in the fuel grain of Jones to produce desired burn characteristics at different times during the burning, or at different locations in the combustible element (see Danforth, para [0033]). Regarding claim 80, Jones in view of Danforth discloses the fuel grain of claim 49. Jones further discloses in which at least some of the beads comprise a metallic or polymer additive material (para [0034], [0064]: 5% NmX-01 nanocomposite aluminum nanocomposite aluminum additive). Regarding claim 81, Jones in view of Danforth discloses the fuel grain of claim 80. Jones further discloses in which the metallic or polymer additive material comprises nanoscale or microscale metal or polymer particles (para [0034], [0064]: 5% NmX-01 nanocomposite aluminum nanocomposite aluminum additive). Regarding claim 82, Jones in view of Danforth discloses the fuel grain of claim 81. Jones further discloses in which the metallic or polymer additive material comprises nanoscale aluminum particles (para [0034]: 5% NmX-01 nanocomposite aluminum). Regarding claim 83, Jones in view of Danforth discloses the fuel grain of claim 82. Jones further discloses in which the nanoscale aluminum particles are passivated with a polymer (para [0069], [0084]: Ultra-high energetic nano particle size aluminum, especially aluminum powder produced without an aluminum oxide shell and passivated (by encapsulating or 'capping' the particle in a polymer shell)). Regarding claim 84 and 85, Jones in view of Danforth discloses the fuel grain of claim 82 or 83. Jones further discloses in which the nanoscale aluminum particles have an average diameter of between 5 nm and 20 nm (para [0084]: the size of which measures 100 nanometers (nm) or less). Conclusion Any inquiry concerning this communication or earlier communications from the examiner should be directed to AILEEN BAKER FELTON whose telephone number is (571)272-6875. The examiner can normally be reached Monday 9-5:30, Thursday 11-3, Friday 9-5:30. Examiner interviews are available via telephone, in-person, and video conferencing using a USPTO supplied web-based collaboration tool. To schedule an interview, applicant is encouraged to use the USPTO Automated Interview Request (AIR) at http://www.uspto.gov/interviewpractice. If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Jonathan Johnson can be reached at 571-272-1177. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300. Information regarding the status of published or unpublished applications may be obtained from Patent Center. Unpublished application information in Patent Center is available to registered users. To file and manage patent submissions in Patent Center, visit: https://patentcenter.uspto.gov. Visit https://www.uspto.gov/patents/apply/patent-center for more information about Patent Center and https://www.uspto.gov/patents/docx for information about filing in DOCX format. For additional questions, contact the Electronic Business Center (EBC) at 866-217-9197 (toll-free). If you would like assistance from a USPTO Customer Service Representative, call 800-786-9199 (IN USA OR CANADA) or 571-272-1000. /AILEEN B FELTON/Primary Examiner, Art Unit 1734
Read full office action

Prosecution Timeline

Jun 07, 2024
Application Filed
Mar 06, 2026
Non-Final Rejection — §103 (current)

Precedent Cases

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Study what changed to get past this examiner. Based on 5 most recent grants.

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Prosecution Projections

1-2
Expected OA Rounds
51%
Grant Probability
67%
With Interview (+15.5%)
4y 6m
Median Time to Grant
Low
PTA Risk
Based on 435 resolved cases by this examiner. Grant probability derived from career allow rate.

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