Improving Lunar Return Entry Range Capability Using Enhanced Skip Trajectory Guidance

Putnam, Zachary R.; Bairstow, Sarah; Braun, Robert D.; Barton, Gregg H.

doi:10.2514/1.27616

Cited by 37 publications

(21 citation statements)

References 5 publications

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“…It is evident that many of the misses are tens to hundreds of kilometers from the intended landing site. This is a well-known limitation of the Apollo algorithm [24]. The Apollo algorithm calculates incorrect exit conditions for the upcontrol phase (the exit point of the skip).…”

Section: Results For Apollo Skip Entry Guidancementioning

confidence: 98%

“…With modern Global Positioning System (GPS) data, as discussed in Ref. [24], greater knowledge of vehicle state information is expected. The same knowledge of vehicle state is permitted for the FNPEG algorithm to facilitate the comparison.…”

Section: Modifications For Current Workmentioning

confidence: 99%

“…Once such a reference trajectory is found, the Apollo guidance system commands the bank angle to track the reference velocity and rate of altitude profiles by a linear guidance law. The various approximations and linearization assumptions have been found to limit the accuracy of the guidance in this work and others [2,24], especially in the case where the downrange is medium to long. This inaccuracy can have a significant adverse impact on the success of the mission.…”

Section: Introductionmentioning

confidence: 96%

“…A current focus in entry guidance research is on improving landing accuracy in the presence of extreme dispersions (relative to dispersions used by others [3,21]) by taking advantage of modern on-board computational capability [2,4,5,16,17,22,24]. These new guidance algorithms numerically simulate the entry trajectory by integrating the equations of motion [23].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Fully Numerical Predictor-Corrector and Apollo Skip Entry Guidance Algorithms

Brunner

2012

J of Astronaut Sci

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The dramatic increase in computational power since the Apollo program has enabled the development of numerical predictor-corrector (NPC) entry guidance algorithms that allow on-board accurate determination of a vehicle's trajectory. These algorithms are sufficiently mature to be flown. They are highly adaptive, especially in the face of extreme dispersion and off-nominal situations compared with reference-trajectory following algorithms. The performance and reliability of entry guidance are critical to mission success. This paper compares the performance of a recently developed fully numerical predictor-corrector entry guidance (FNPEG) algorithm with that of the Apollo skip entry guidance. Through extensive dispersion testing, it is clearly demonstrated that the Apollo skip entry guidance algorithm would be inadequate in meeting the landing precision requirement for missions with medium (4000-7000 km) and long (>7000 km) downrange capability requirements under moderate dispersions chiefly due to poor modeling of atmospheric drag. In the presence of large dispersions, a significant number of failures occur even for shortrange missions due to the deviation from planned reference trajectories. The FNPEG algorithm, on the other hand, is able to ensure high landing precision in all cases tested. All factors considered, a strong case is made for adopting fully numerical algorithms for future skip entry missions.

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Section: Results For Apollo Skip Entry Guidancementioning

confidence: 98%

Section: Modifications For Current Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Comparison of Fully Numerical Predictor-Corrector and Apollo Skip Entry Guidance Algorithms

Brunner

2012

J of Astronaut Sci

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“…Both algorithms use a numerical predictorcorrector for the skip phase coupled with the Apollo ¦nal phase entry guidance. Putnam et al also presented a skip entry guidance by introducing a numerical predictorcorrector phase during the atmospheric skip portion with an Apollo guidance baseline algorithm [3]. Vernis et al reported a numerical predictorcorrector entry guidance that had been designed within the frame of the ESA-funded ¢Robust skip Entry£ program [6].…”

Section: Introductionmentioning

confidence: 99%

Accurate predictor–corrector skip entry guidance for low lift-to-drag ratio spacecraft

Enmi

Qian

et al. 2018

Progress in Flight Dynamics, Guidance, Navigation, and Control – Volume 10

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This paper develops numerical predictorcorrector skip entry guidance for vehicles with low lift-to-drag L/D ratio during the skip entry phase of a Moon return mission. The guidance method is composed of two parts: trajectory planning before entry and closed-loop guidance during skip entry. The result of trajectory planning before entry is able to present an initial value for predictorcorrector algorithm in closed-loop guidance for fast convergence. The magnitude of bank angle, which is parameterized as a linear function of the range-to-go, is modulated to satisfy the downrange requirements. The sign of the bank angle is determined by the bank-reversal logic. The predictor-corrector algorithm repeatedly applied onboard in each guidance cycle to realize closed-loop guidance in the skip entry phase. The e¨ectivity of the proposed guidance is validated by simulations in nominal conditions, including skip entry, loft entry, and direct entry, as well as simulations in dispersion conditions considering the combination disturbance of the entry interface, the aerodynamic coe©cients, the air density, and the mass of the vehicle.

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Optimal feedback gains determination method for nominal reentry guidance

Shen

2015

Optim Control Appl Methods

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This paper presents a new method for solving feedback gains in guidance based on optimal control theory. The determination of feedback gains is a critical problem for nominal guidance, because landing precision benefits from appropriate feedback gains. The magnitude of the bank angle is determined by minimizing the total error of final altitude as well as downrange requirement to the landing site. The problem is formulated as an optimal control problem by means of the Pontryagin's maximum principle, and backward integration is used to solve the problem based on homogeneous property. The proposed approach not only can avoid linearizing the nonlinear dynamic equations, but also are applicable to different guidance equations. Validation shows that the proposed approach can provide consistent results with that of Apollo. Despite employment of nominal guidance in the entire reentry of lunar mission, the proposed approach demonstrates good performance in all simulation cases while subject to significant disturbances. Figure 3. The 5000 dispersed cases of simulation results. (a) Latitude versus longitude, (b) histogram of load factor, (c) histogram of maximal heat rate, and (d) histogram of heat load. 221 OPTIMAL FEEDBACK GAINS FOR REENTRY GUIDANCE

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Improving Lunar Return Entry Range Capability Using Enhanced Skip Trajectory Guidance

Cited by 37 publications

References 5 publications

Comparison of Fully Numerical Predictor-Corrector and Apollo Skip Entry Guidance Algorithms

Comparison of Fully Numerical Predictor-Corrector and Apollo Skip Entry Guidance Algorithms

Accurate predictor–corrector skip entry guidance for low lift-to-drag ratio spacecraft

Optimal feedback gains determination method for nominal reentry guidance

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