A multibody. flight simulation for the Mars Science Laboratory that includes six-degree-of-freedom rigid-body models for both the supersonically deployed and subsonically deployed parachutes has been developed. This p...
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A multibody. flight simulation for the Mars Science Laboratory that includes six-degree-of-freedom rigid-body models for both the supersonically deployed and subsonically deployed parachutes has been developed. This provides a complete end-to-end simulation of the entire entry, descent, and landing sequence. The simulation provides attitude history predictions of all bodies throughout the flight as well as loads on each of the connecting lines. Other issues such as recontact with jettisoned elements (heat shield, backshell, parachute mortar covers, etc.), design of parachute and attachment points, and desirable line properties can also be addressed readily using this simulation. Time histories of the parachute line loads and the parachute and lander aerodynamic angles are presented. The simulation shows that the backshell does not recontact the lander after separation.
The vertical landing and recovery of rockets are now considered an important solution in the field of reusable launch vehicles. This paper focuses on guided atmospheric entry to reach an expected landing site before l...
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The vertical landing and recovery of rockets are now considered an important solution in the field of reusable launch vehicles. This paper focuses on guided atmospheric entry to reach an expected landing site before landing with powered descent. Using the characteristic of predictive algorithms that the onboard model can be changed easily, a new predictive entry guidance algorithm based on the dual-channel attitude control of a low-lift entry vehicle is proposed. Because the accuracy of the predictive guidance entirely depends on the discrepancies between the onboard dynamic model and the real environment while the rocket enters the atmosphere, an onboard adaptive identification method of aerodynamic deviation is added to decrease the methodological error. Simulation results show that the adaptive predictive entry guidance performance is no longer dependent on knowledge of aerodynamic and density dispersion. The adaptive aerodynamic fitting method repeatedly adapts the onboard model to varied environments in real time, decreasing the traditional predictive algorithms' guidance error from kilometer-to meter-scale precision.
The sizing and capability definitions of reusable launchers during high-speed recovery are very challenging problems. In this paper, a convex optimization guidance algorithm for this type of system is proposed, based ...
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The sizing and capability definitions of reusable launchers during high-speed recovery are very challenging problems. In this paper, a convex optimization guidance algorithm for this type of system is proposed, based on performance improvements arising from the study of the coupled flight mechanics, guidance, and control problem. To appreciate the obtained improvements, tradeoff analyses of powered descent and landing scenarios are presented first using traditional guidance techniques. Subsequently, these results are refined by using the proposed online successive convex optimization-based guidance strategy. The descending over extended envelopes using successive convexification-based optimization (DESCENDO) algorithm has been designed as a middle ground between efficiency and optimality. This approach contrasts with previous convexification algorithms that either aimed at increasing computational efficiency (by typically disregarding aerodynamic deceleration) or reaching trajectory design optimality (by using exhaustive convex approximations). More critically, the algorithm is not confined to the mild coverage conditions assumed by previous approaches and can successfully handle the incorporation of the operational dynamics of reusable launchers. Insights provided by DESCENDO operating in a closed-loop fashion over full recovery scenarios enable a computationally efficient mission performance assessment.
A guidance algorithm was used to examine the space rendezvous process from a low-circular orbit departure, to final docking of a space vehicle taxi, with the cycler. The algorithm tracked the desired approach profile,...
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A guidance algorithm was used to examine the space rendezvous process from a low-circular orbit departure, to final docking of a space vehicle taxi, with the cycler. The algorithm tracked the desired approach profile, allowing the taxi, to dock within 10 cm of the approach axis at a speed of 7 cm per second. It was observed that the docking procedure can be repeated, when the taxi approaches the the cycle outside the docking radius. Safety measures and redundant systems were included in the rendezvous strategy, to overcome the problems faced by the taxi in docking with the cycler. The safety measures adopted provided adequate safety for hyperbolic rendezvous, overcoming a major challenge of cycler and semicycler architectures.
This paper examines the ability of a bilinear tangent guidance law to perform continuous-thrust, single-burn orbital maneuvers in the small-body orbital environment (solar radiation pressure, etc.) and the capability ...
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This paper examines the ability of a bilinear tangent guidance law to perform continuous-thrust, single-burn orbital maneuvers in the small-body orbital environment (solar radiation pressure, etc.) and the capability of a Newton-Raphson predictor-corrector algorithm to perform free-time, state-to-state spacecraft guidance on initial state perturbations. This paper shows that low-thrust bilinear tangent is able to perform a wide variety of maneuvers with a wide variety of thrust levels around asteroid Bennu. Additionally, this paper shows that even with a high control authority, the size of initial state perturbations that can be corrected depends on the size of the target state's complex backward-reachable subspace and the location of the initial state of the maneuver in that subspace. For example, a 5 mN thruster on a 1000 kg spacecraft performed an aggressive shape and plane change maneuver for less than 3.5 g of fuel. The derived guidance algorithm then corrected 100% of initial state perturbations drawn from delta r similar to N(33,17.5) m and delta v similar to N(3,1.7) mm/s distributions. Ultimately, this paper shows that Newton-Raphson predictor-corrector bilinear tangent guidance is a capable guidance scheme when used on perturbations that lie within the reachable subspace of the target state.
The paper proposes a guidance algorithm for a single pursuer facing multiple maneuvering evaders, one of which is finally engaged by the pursuer. It is assumed that the pursuer makes a decision to engage one of the ev...
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The paper proposes a guidance algorithm for a single pursuer facing multiple maneuvering evaders, one of which is finally engaged by the pursuer. It is assumed that the pursuer makes a decision to engage one of the evaders at a given moment in flight, and the probability of each possible choice is known in advance. Under these assumptions, a guidance law is derived that optimizes the expected integral quadratic control effort, where the expectation is taken over all possible engagement decisions. The derived guidance law turns out to be a linear combination of optimal pursuit guidance laws toward each of the evaders separately, with time-dependent coefficients. Numerical simulation results show the efficiency of the proposed guidance law with respect to conventional solutions that do not take into account the delayed engagement decision.
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