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It is well known that the Orion capsule was born as a rescue shuttle for the International Space Station. NASA developed the Orion project for the transportation of instruments and astronauts to mo...

This work details the development of new stagnation-point aeroheating engineering correlations for Mars entry vehicles. Convective and radiative heating relations were formulated over a wide range ...

An approach is presented for eliminating communication blackout caused by the plasma sheath encountered during the Mars atmospheric entry phase. On the basis of the high penetration of X-ray beams,...

An analysis of deployable aerodecelerators has been performed using a developed six-degree-of-freedom entry trajectory simulator coupled with a structural model of the deployable structural members, or ribs, to investigate the effect of aerodecelerator flexibility on the trajectory and configuration design. The modified Newtonian method is used in the entry trajectory simulator, and the deployable ribs are modeled as Euler–Bernoulli beams. It is shown that, although flexibility is beneficial in reducing the mass and volume of the deployed ribs, an increase in peak heat flux will result. However, if mass savings from flexible ribs can be reallocated toward increasing the diameter of the entry vehicle, significant benefits can be gained.

The reconstruction of atmospheric properties encountered during Mars entry trajectories is a crucial element of postflight mission analysis. This paper proposes a deep learning architecture using a long short-term memory (LSTM) network for the reconstruction of Martian density and wind profiles from inertial measurements and guidance commands. The LSTM is trained on a large set of Mars entry trajectories controlled through the fully numerical predictor-corrector entry guidance (FNPEG) algorithm, with density and wind from the Mars Global Reference Atmospheric Model (GRAM) 2010. The training of the network is examined, ensuring that the LSTM generalizes well to samples not present in the training set, and the performance of the network is assessed on a separate training set. The errors of the reconstructed density and wind profiles are, respectively, within 0.54 and 1.9%. Larger wind errors take place at high altitudes due to the decreased sensitivity of the trajectory in regions of low dynamic pressure. The LSTM architecture reliably reproduces the atmospheric density and wind encountered during descent.

Enhancing the positional information acquisition during Mars entry blackout improves the Mars landing mission reliability. A positioning method based on the high-penetration of X-rays was developed to solve the problem. The X-ray signal attenuation was estimated. The positioning performance and the influence of X-ray signal transmission system were also evaluated. Results indicated that the X-ray signal attenuation is extremely low, and the X-ray-based method is expected to be a potential application for obtaining high-precision positional information during Mars entry blackout.

Defining a feasible vehicle design and mission architecture capable of reliably delivering apayload of 20 metric tons (mt) or more is a great challenge for landing humans on Mars. TheMid Lift-to-Drag Rigid Vehicle (MRV), a rigid decelerator studied in NASA’s Entry, Descent,and Landing Architecture Study (EDLAS), has shown to be a viable vehicle candidate forfuture human Mars missions. As the vehicle concept matures, models of increasing fidelity areadded to the six-degree-of-freedom (6DoF) EDL simulation. This paper presents 6DoFsimulation results using model updates for vehicle mass properties, fineness ratio, andaerodynamic-propulsive interactions. Additionally, an assessment of the Fractional-Polynomial Powered Descent Guidance (FP2DG) performance is presented, and the vehicleperformance is compared with the Tunable Apollo Powered Descent Guidance (TAPDG).Finally, Monte Carlo results of the vehicle design trades are presented.

Over the past four years, NASA has directed the Entry, Descent and Landing Architecture Study (EDLAS) to evaluate candidate technologies to deliver human-scale vehicles (carrying 20t payloads) to the surface of Mars. The study focused on two vehicles in Phase 3 (during 2018 and 2019), one low and one mid lift-to-drag (L/D) vehicle. This paper summarizes updates to the structural and aeroshell outer mold line design for the mid-L/D Mars entry lander vehicle that occurred during EDLAS Phase 3. The design efforts used parametric optimization to arrive at a solution for total vehicle primary and secondary structure mass, and vehicle center-of-gravity location. Additionally, the end of Phase 2 provided an updated surface payload manifest that required three 22 t landers. This paper also summarizes the results of the packaging feasibility study of the updated payload configurations for those three reference missions. The study verified an arrangement of the payload elements within the mid-L/D vehicle that satisfied the center of gravity location limitations for flight.

In this study, a novel \( H_{\infty } \) guidance strategy based on optimal control theory is proposed to guide the spacecraft landing on the Mars precisely. Initially, the error system of entry phase with the external disturbance is derived, and the method of tracking the nominal entry trajectory is adopted. Considering the difference of magnitudes’ order between several state variables concluding the altitude, the velocity and range, normalization strategy is used to avoid numerical problem. Subsequently, the \( H_{\infty } \) optimal control theory is introduced, and the difficulty of the entry phase is that the Hamilton-Jacobi-Isaacs (HJI) equation with control constraint must be solved. So the neural network (NN) is introduced to get the solution of HJI equation approximately. Finally, simulation is done to demonstrate the \( H_{\infty } \) guidance strategy.

Building upon the success of the Mars Science Laboratory (MSL) landing and surface mission, the Mars 2020 project is a flagship-class science mission intended to address key questions about the potential for life on Mars and collect samples for possible Earth return by a future mission. [1] Mars 2020 will also demonstrate technologies needed to enable future human expeditions to Mars. Utilizing the groundbreaking entry, descent, and landing (EDL) architecture pioneered by the MSL, [2] [3] Mars 2020 will launch in July 2020 and land on Mars in February 2021. Like its predecessor, Mars 2020 will deliver its rover payload to the Martian surface through the use of Apollo-derived entry guidance, a 21.45 meter supersonic Disk-Gap-Band parachute, a Descent Stage powered by throttleable Mars lander engines, and the signature Sky Crane maneuver. While Mars 2020 inherits most of its EDL architecture, software, and hardware from the MSL, a number of changes have been made to correct deficiencies, improve performance, and increase the robustness of the system. For example, Mars 2020 will take advantage of the favorable atmospheric conditions of the 2020 launch opportunity to deliver a larger and more capable rover than has landed on Mars to date. A primary focus in developing the Mars 2020 EDL system has been mitigating residual risks identified after the landing of the MSL. The Advanced Supersonic Parachute Inflation Research Experiment (ASPIRE) was performed to address new concerns about the stresses experienced by parachute canopies during inflation. Other risk reduction activities include investigating possible interactions between the parachute deployment system and the inertial measurement unit (IMU) which could lead to IMU saturation, researching the effects of airborne dust on radar ground measurements, and site-specific gravity modeling for improved fuel usage. Several enhancements were added for Mars 2020 to improve performance. The addition of Terrain Relative Navigation (TRN) allows the system to land at sites with more hazardous terrain, enabling scientists to select from locations which have previously been considered inaccessible. Mars 2020 will utilize a Range Trigger for initiating parachute deployment, which reduces landing ellipse sizes by 40% compared to the Velocity Trigger approach used on the MSL. New EDL Camera hardware will capture high resolution and high frame rate images and videos of key events, such as parachute deployment and rover touchdown. Finally, the Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) sensor suite will build upon the successful MSL MEDLI experiment with the addition of heatshield pressure sensors tuned for the supersonic flight regime and backshell instrumentation. The team has faced new and unexpected challenges throughout development. Notably, the failure of the flight heatshield during a static load test has prompted the fabrication of a new unit. Also, in accommodating the first ever Mars Helicopter under the rover belly pan, the EDL design has been further constrained by reduced ground clearances. Despite these challenges, much of the EDL-related hardware and software have already been delivered, and the EDL verification and validation program is on track to be completed on schedule prior to launch in July 2020.

The real-time trajectory replanning method which is used for the guidance of Mars entry is investigated in this paper. Comparing with the traditional Mars entry guidance methods, such as the reference-trajectory tracking guidance and predictor–corrector guidance, the real-time trajectory replanning method can increase the reliability of the mission remarkably. When faults occur during the Mars entry phase, a replacement trajectory will be planned quickly. Due to the limited onboard computing capacity, replanning the trajectory onboard is a challenging task. Corresponding to this problem, the neural network is trained to approximate the dynamics of the atmospheric entry. The uncertain factor of the atmospheric density is also included in the neural network. Then, by using the characters of the neural network, the analytical expressions of the Jacobian which are needed in trajectory optimization are derived. Finally, an estimation-replanning guidance procedure is introduced. The numerical simulation shows that the proposed guidance strategy can decrease the error of final states effectively, and the neural network approximation improves the computational speed of the nonlinear programming solver remarkably, which makes the method more suitable for use onboard.

This paper focuses on the attitude tracking control problem of Mars entry vehicle (MEV) with time-varying input delay. The original attitude dynamics of MEV is divided into slow subsystem and fast subsystem. For slow subsystem, the dynamic inversion method is used to generate the angular velocity command. For fast subsystem, a T-S fuzzy model is used to approximate it, and delays-dependent $$H_{\infty }$$ attitude tracking control is applied to reduce the effects of delay on attitude dynamics. Specially, a decomposition coefficient of delay integral inequality is introduced in our proposed results, which may further reduce the design algorithm conservatism. Finally, numerical simulations are used to verify the effectiveness of the proposed method.

Develop two evolutionary rigid vehicle concepts to deliver human-scale payloads (20 metric tons) to the surface of Mars: Capsule; Lifting body, mid-range lift-to-drag ratio (Mid L/D). Determine vehicle configurations for various mission flight phases. Determine vehicle performance: Integrated system mass; Ability to meet landing constraints; Payload packaging and surface access. Provide technology investment recommendations to NASA’s Space Technology Mission Directorate.

This paper investigates the deployment of an internal sole-moving-mass actuator in Mars entry vehicles. Given the extreme environment of Mars atmosphere, moving mass control has gained plenty of advantages in efficiency, cost and reliability over aerodynamic flap and thruster-based control. First, a model of moving-mass dynamics is derived using Kane’s Method based on the proposed moving mass configuration. In such a multi-body system, the interactions between the moving mass and the vehicle are focused on during the modeling procedure. Then, several key parameters of the moving mass configuration are determined through analysis. Finally, the manipulation characteristics are verified to ensure the capability of mission accomplishment. Simulation results indicate the applicability and effectiveness of the proposed sole-moving-mass actuator.

This paper presented a robust integrated navigation algorithm based on a special robust desensitized extended Kalman filtering with analytical gain (ADEKF) during the Mars atmospheric entry. The robust ADEKF is designed by minimizing a new function penalized by a trace weighted norm of the state error sensitivities and giving a closed-form gain matrix. The uncertainties of the Mars atmospheric density and the lift-to-drag ratio (LDR) percentage are modeled. Sensitivity matrices are defined to character the parameter uncertainties, and corresponding perturbation matrices are proposed to describe the navigation errors respected to the parameter uncertainties. The numerical simulation results show that the robust integrated navigation algorithm based on the robust ADEKF effectively reduces the negative effects of the two parameter uncertainties and has good consistency during the Mars entry., 11 pages, 7 figures

The serious challenge of future Mars mission is to find an appropriate entry guidance algorithm that can deliver the lander to the desired parachute deployment site under highly uncertain initial conditions. This paper describes the development and evaluation of the common numerical predictor–corrector algorithm and gives an improved algorithm — segmented guidance predictor–corrector algorithm for the Mars entry guidance. The common predictor–corrector algorithm can be less sensitive to initial dispersions, but needs fast on-board computation. However, the improved predictor–corrector algorithm and lateral control logic, detailed descriptions in the paper, is provided to shorten the on-board computational time. Furthermore, a heading alignment guidance law is used to improve the horizontal accuracy of the vehicle at the end of entry phase. Simulation results show that this entry guidance algorithm demonstrates reliable and robust performance in situations with high uncertainties.

The base of the dynamics characteristic research on the parachute and vehicle system is to establish a dynamics model, during the parachute descent phase, which can accurately display the relationship among the velocity, altitude and attitude angles as well as the variation of time. This paper starts with a new tracking law – ADRC in Mars entry guidance, which affects the initial states of the parachute deployment point and determines precision landing capability. Then, the influence of unsteady resistance to the parachute in Martian air is considered as the added mass, and a 6DOF nonlinear mathematical model of the parachute and vehicle system is established.

On the 19th October 2016, Schiaparelli, the Entry Demonstrator Module (EDM) of the ESA ExoMars Program entered into the martian atmosphere. Although it did not complete a safe landing on Mars, it transmitted data throughout its descent to the surface, until the loss of signal at 1 minute before the expected touch-down on Mars' surface. The main objective of the Atmospheric Mars Entry and Landing Investigations and Analysis (AMELIA) experiment was the assessment of the atmospheric science and landing site by exploiting the Entry Descent and Landing System (EDLS) sensors of Schiaparelli beyond their designed role of monitoring and evaluating the performance of the EDL technology demonstrator. Although more limited than expected, the flight data received from Schiaparelli are essential to investigate the anomaly that caused the crash landing and for the achievement of the AMELIA scientific objectives. We will present our methodology and results for the reconstruction of the dynamics of the vehicles during the EDL phases from the available flight data in order to assess the trajectory and attitude of the Schiaparelli EDM and to retrieve the atmospheric profiles.

This contribution is a survey of aerodynamic and aerothermodynamics data related to Mars entry. The survey includes the studies carried out in the frame of projects aiming at preparing exploration missions involving entry probes into Mars atmosphere and the efforts have been concentrated on the aerothermodynamics developments. Russian (including former Soviet Union), European and NASA aerothermodynamics developments for preparing such missions have been accounted for. If a focus has been dedicated to the flight data gathered during Viking and Mars Pathfinder entries, the experimental and numerical activities carried out for the different projects have been also considered. The emphasis has been put on the post-flight analysis of flight experiments. The objective of the activity has been to develop a database of the developments performed for Mars entry that will be of interest for the preparation of future missions and for testing new models related to radiative transfer, and chemical kinetics schemes based on a state-to-state approach.

The Mars atmospheric entry phase plays a vital role in the whole Mars exploration mission-cycle. It largely determines the success of the entire Mars mission. In order to achieve a pin-point Mars landing, advanced entry guidance and control is essential. This paper systematically summarizes the past development and current state-of-art of Mars entry guidance and control technologies. More specifically, the Mars entry process and main technical challenges are first introduced. Second, the guidance and control technologies adopted in the past successful Mars landing mission are reviewed in detail. Next, current state-of-art and recent developments of guidance and control for Mars atmospheric entry are summarized at length. The advantages and disadvantages of the various existing methods are analyzed. Lastly, supposing future Mars pin-point landing missions as the potential project application goals, a more comprehensive outlook and prospect for the next-generation Mars entry guidance and control technologies are described.

Early in the development of the Mars Science Laboratory thermal protection system on the heatshield, project management planned to use Lockheed Martin’s Super Light Ablator in honeycomb as the ablative material based on successful use on previous Mars entry heatshields and on stagnation arcjet tests at heating rates beyond the design levels. Because this heatshield would be the first to experience combined turbulent flow and high shear environments as it entered the Mars atmosphere, tests were performed in various arcjet facilities on flat-plate, wedge, and swept-cylinder specimen configurations in order to ascertain the effects of shear on the material. During the course of these tests, a set of conditions within the flight envelope was identified that resulted in catastrophic failure in the SLA-561V. Consequently, project management decided to replace the SLA-561V with the phenolic-impregnated carbon ablator, the material that had flown successfully on the Stardust mission and was undergoing intense tes...

An assessment of computational uncertainties is presented for numerical methods used by NASA to predict laminar, convective aeroheating environments for Mars-entry vehicles. A survey was conducted of existing experimental heat transfer and shock-shape data for high-enthalpy reacting-gas CO2 flows, and five relevant test series were selected for comparison with predictions. Solutions were generated at the experimental test conditions using NASA state-of-the-art computational tools and compared with these data. The comparisons were evaluated to establish predictive uncertainties as a function of total enthalpy and to provide guidance for future experimental testing requirements to help lower these uncertainties.

This paper deals with the problem of attitude tracking control for MEVs (Mars entry vehicles). The rotational motion of MEVs system consists of fast subsystem and slow subsystem. The attitude dynamics are given by slow subsystem and angular velocity dynamics are given by fast subsystem. A T-S fuzzy modal is achieved to approximate the fast subsystem. Based on this obtained model, the attitude tracking control is designed via combining DOBC (disturbance-observer-based control) with delay-dependent H ∞ , control. Therefore, the delay-dependent state controller is obtained, which can reduce the effects of delay and disturbance on attitude. Finally, the effectiveness of our method is verified by numerical simulations.

The uncertain parameters exist in Mars entry have a significant effect on Mars entry navigation. In this paper, the hierarchical adaptive filter regulated by a gating network is presented to identify the uncertain parameters during Mars entry, which are atmosphere density, lift over drag ratio and ballistic coefficient. The hierarchical structure is composed of several bank of filters, and each bank of filters is composed of several experts running in parallel. Each expert is a realization of some parameter values. The gating network can adaptively assign appropriate weights to the filter banks and the experts. The weight which is close to unity corresponding to certain expert means that the given parameter value is close to the real value or is right the real value. By this way, the uncertain parameters can be identified. Also the effect of learning rate factor on the convergence rate of gating weights and the identification capability is demonstrated. The effectiveness of this method can be illustrated by the case of Mars entry navigation.

With the development of Mars exploration, NASA has been preparing plans for a crewed mission to Mars in the next few decades. One challenge associated with crewed missions to the Mars is the high ballistic-coefficient and human-class payloads. Because of the high ballistic-coefficient, the maximum limit value of the reference flight path angle is always the reference flight path angle meeting the downrange and altitude for the constant flight path angle algorithm. So this paper presents an improved algorithm which the terminal velocity is controlled by dynamic pressure controller, and the controller is used to modulate the velocity and altitude to meet final constraints. Simulations results of a Mars entry scenario illustrate that the improved algorithm achieves the final constraints within allowable tolerances.

To deliver a Mars entry vehicle through the Martian atmosphere to the prescribed parachute deployment point, active Mars entry guidance and control is essential. This article addresses the problem of Mars atmospheric entry control by a neural network-based sliding mode variable structure control (NNSMVSC) to reduce the effect of the bounded uncertainties on the atmospheric density and aerodynamic coefficients. First, NNSMVSC is designed to robustly track the prescribed nominal trajectory under high uncertainties and to effectively reduce the downrange error. Then, the heading alignment logic is adopted in the lateral plane to reduce the cross-range error. Finally, the validity of the control algorithm proposed in this article is demonstrated by computer simulation analysis.

The architecture concepts and aggressive science objectives for the next phases of Mars exploration will require landed masses an order of magnitude or greater than any Mars mission previously planned or flown. Additional studies have shown the requirements for missions more ambitious than the 2009 Mars Science Laboratory (∼900 kg payload mass) to extend beyond the capabilities of Viking-heritage entry, descent, and landing (EDL) technologies, namely blunt-body aeroshells, supersonic disk-gap-band parachutes, and existing TPS materials. This study details a concept for Mars entry, descent, and landing capable of delivering a 20 t payload within 1 km of a target landing site at 0 km MOLA. The concept presented here explores potentially enabling EDL technologies for the continued robotic and eventual human exploration of Mars, moving beyond the Viking-heritage systems relied upon for the past 30 years of Mars exploration. These technologies address the challenges of hypersonic guidance, supersonic deceleration, precision landing, and surface hazard avoidance. Without support for the development of these enabling technologies in the near term, the timeline for the successful advanced exploration of Mars will likely extend indefinitely.

An attempt has been made to analyze impact of Martian atmosphere parameter uncertainties on entry vehicle aerodynamics for hypersonic rarefied conditions with a DSMC code. The code has been validated by comparing Viking vehicle flight data with present computational results. Then, by simulating flows around the Mars Science Laboratory, the impact of errors of free stream parameter uncertainties on aerodynamics is investigated. The validation results show that the present numerical approach can show good agreement with the Viking flight data. The physical and chemical properties of CO2 has strong impact on aerodynamics of Mars entry vehicles, so it is necessary to make proper corrections to the data obtained with air model in hypersonic rarefied conditions, which is consistent with the conclusions drawn in continuum regime. Uncertainties of free stream density and velocity weakly influence aerodynamics and pitching moment. However, aerodynamics appears to be little influenced by free stream temperature, the maximum error of what is below 0.5%. Center of pressure position is not sensitive to free stream parameters.An attempt has been made to analyze impact of Martian atmosphere parameter uncertainties on entry vehicle aerodynamics for hypersonic rarefied conditions with a DSMC code. The code has been validated by comparing Viking vehicle flight data with present computational results. Then, by simulating flows around the Mars Science Laboratory, the impact of errors of free stream parameter uncertainties on aerodynamics is investigated. The validation results show that the present numerical approach can show good agreement with the Viking flight data. The physical and chemical properties of CO2 has strong impact on aerodynamics of Mars entry vehicles, so it is necessary to make proper corrections to the data obtained with air model in hypersonic rarefied conditions, which is consistent with the conclusions drawn in continuum regime. Uncertainties of free stream density and velocity weakly influence aerodynamics and pitching moment. However, aerodynamics appears to be little influenced by free stream temperature, th...

A new composite nonlinear predictive control (NPC) method based on finite-time disturbance observer is proposed for Mars entry drag trajectory tracking. The composite controller uses nonlinear predictive control strategy in a feedback regulation way to obtain desired tracking performance and uses the disturbance estimation based on finite-time disturbance observer (FTDO) to compensate uncertainty in a feedforward way. The proposed guidance law not only compensates the matched disturbance but also the mismatched disturbance. The drag tracking error is also guaranteed to converge to 0 even when the disturbance is time-varying and related with states.