US3990657A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for reducing ballistic missile range errors due to viscosity uncertainties (U)
Assignee: United States Department of the Navy
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Filing: 1974-04-22
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Granted: 1976-11-09
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Expires: 1994-04-22
Abstract
Abstract Errors in the trajectories of balistic missiles result from a number of ces such as the velocity uncertainty of the missile during its powered flight. Prediction of these errors provides the missile circular error probability (CEP) usually in the form of a ballistic position error ellipse that is derived for each trajectory. This ellipse can be used to significantly improve performance by reducing the error probability. At a particular time (T 1 ) during the flight a radar altimeter determines the actual altitude of the missile and computation of the altitude error is made by subtracting the actual altitude from the nominal altitude at T 1 provided by the predetermined ellipse. Range error is computed from the relationship Δ h over tangent θ where θ is the angle of the ellipse semi-major axis with respect to the vertical. A missile control system then directs a maneuver based upon the range error to correct the error by returning the missile to its nominal trajectory.
Inventors
- 👤 Gene D. Schott
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 22:58
CPC Classifications
F; F42; F42C; F42C13/00; F42C13/04; F41; F41G; F41G7/00; F41G7/34; F41G7/343
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
99 words
A method of improving range accuracy of ballistic missiles having a predetermined nominal trajectory defined by a specific ballistic position error ellipse comprising: measuring the actual trajectory altitude of the missile at a particular time (T 1 ), computing the altitude error (Δ h) relative to the nominal altitude at T 1 , and computing a position error (Δ R) at T 1 by resolving the relationship ##EQU3## where θ is the angle of said ellipse semi-major axis with respect to the target horizontal, and maneuvering the trajectory of said missile sufficiently to compensate for said computed position error.
Claim 2
Independent Claim
99 words
A method of improving range accuracy of ballistic missiles having a predetermined nominal trajectory defined by a specific ballistic position error ellipse comprising: measuring the actual trajectory altitude of the missile at a particular time (T 1 ), computing the altitude error (Δ h) relative to the nominal altitude at T 1 , and computing a position error (Δ R) at T 1 by resolving the relationship ##EQU3## where θ is the angle of said ellipse semi-major axis with respect to the target horizontal, and maneuvering the trajectory of said missile sufficiently to compensate for said computed position error.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein said computations and maneuvering are made during the re-entry-flight portion of the missile trajectory.
Claim 4
Dependent Claim
127 words
Apparatus for correcting the range accuracy of ballistic missiles having a predetermined nominal trajectory defined by a specific ballistic position error ellipse comprising, trajectory timing means, means for measuring the trajectory altitude at any time (T 1 ) during said trajectory, computing means, memory storage means, missile control means responsive to said computer means for varying the missile trajectory, said memory means being provided with preset data regarding the nominal altitude of said missile trajectory at T 1 and the characteristics of said position error ellipse, means for gating said data to said computer at T 1 whereby said computer can resolve the altitude error and the range error, and means for applying said range error data to said missile control means for correcting the range error.
Claim 5
Dependent Claim
127 words
Apparatus for correcting the range accuracy of ballistic missiles having a predetermined nominal trajectory defined by a specific ballistic position error ellipse comprising, trajectory timing means, means for measuring the trajectory altitude at any time (T 1 ) during said trajectory, computing means, memory storage means, missile control means responsive to said computer means for varying the missile trajectory, said memory means being provided with preset data regarding the nominal altitude of said missile trajectory at T 1 and the characteristics of said position error ellipse, means for gating said data to said computer at T 1 whereby said computer can resolve the altitude error and the range error, and means for applying said range error data to said missile control means for correcting the range error.
Claim 6
Dependent Claim
54 words
Apparatus of claim 3 whereby said altitude error (Δ h) is resolved by subtracting the nominal altitude at time T 1 from the measured altitude at T 1 and the range error is derived from the relationship ##EQU4## where θ is the angle of said ellipse major axis with respect to the target horizontal.
Claim 7
Dependent Claim
15 words
The apparatus of claim 3 wherein all of said means are carried by the missile.
References Cited (Backward Citations)
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US2979284A
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US3249324A
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US3184182A
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US3497161A
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US3758052A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-11-09 | 1980-05-10 | 1980-11-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-11-09 | 1984-05-10 | 1984-11-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-11-09 | 1988-05-10 | 1988-11-09 | $7700.00 | Window Closed / Lapsed |