Mars entry, descent, and landing trajectories are highly dependent on the vehicle's aerodynamics and the planet's atmospheric properties during the day of flight. A majority of previous Mars entry trajectory and atmosphere reconstruction analyses do not simultaneously estimate the flight trajectory and the uncertainties in the atmospheric and aerodynamics models. Adaptive filtering techniques, when combined with traditional trajectory estimation methods, can improve the knowledge of the aerodynamic coefficients and atmospheric properties, while also estimating the confidence interval for these parameters. Simulated data sets with known truth data are used in this study to show the improvement in state and uncertainty estimation by using adaptive filtering techniques. Such a methodology can then be implemented on existing and future Mars entry data sets to determine the aerodynamic and atmospheric uncertainties and improve engineering design tools.
The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission touched down in Elysium Planitia on 26 November 2018, becoming NASA’s eighth successful entry, descent, and landing (EDL) at Mars. InSight inherited the successful 2008 Phoenix (PHX) EDL system, flying a nonspinning, ballistic trajectory with a 70 deg sphere–cone aeroshell (2.65 m diameter), a disk–gap–band parachute, and pulsed terminal descent and landing engines. InSight and Phoenix exhibited similar behavior, primarily in terms of trim attitude and an uninitiated roll reversal correlated with dynamic pressure, although the behaviors observed for InSight were more severe. For InSight, the initial clockwise roll and nonzero trim angle of attack were significant contributors to a short timeline, larger-than-predicted deceleration loads, and cross-track and up-track errors in landing location. The InSight and Phoenix reconstructions together indicate behavior more characteristic of a single, continuous instability region, suggesting that errors in the trim behavior from hypersonic nonequilibrium aerodynamics predictions along the dynamic pressure pulse may have a more substantial impact on nonspinning, ballistic entry vehicle performance.
The first purpose of this white paper is to summarize the state-of-the-art of engineering instrumentation available for atmospheric Entry, Descent, and Landing (EDL) vehicles.Capabilities of the various types of measurements, along with recent examples from human and robotic EDL missions and technology development programs, significance to planetary science, and current challenges are discussed.Second, this paper provides recommendations for continuing to collect data on future missions with an EDL phase.Although the focus of this paper will be primarily on entry, instrumentation for descent and landing are also recognized to be important areas of future investment.
On August 5th 2012, The Mars Science Laboratory entry vehicle successfully entered Mars atmosphere and landed the Curiosity rover on its surface. A Kalman filter approach has been implemented to reconstruct the entry, descent, and landing trajectory based on all available data. The data sources considered in the Kalman filtering approach include the inertial measurement unit accelerations and angular rates, the terrain descent sensor, the measured landing site, orbit determination solutions for the initial conditions, and a new set of instrumentation for planetary entry reconstruction consisting of forebody pressure sensors, known as the Mars Entry Atmospheric Data System. These pressure measurements are unique for planetary entry, descent, and landing reconstruction as they enable a reconstruction of the freestream atmospheric conditions without any prior assumptions being made on the vehicle aerodynamics. Moreover, the processing of these pressure measurements in the Kalman filter approach enables the identification of atmospheric winds, which has not been accomplished in past planetary entry reconstructions. This separation of atmosphere and aerodynamics allows for aerodynamic model reconciliation and uncertainty quantification, which directly impacts future missions. This paper describes the mathematical formulation of the Kalman filtering approach, a summary of data sources and preprocessing activities, and results of the reconstruction.
A law is designed for simultaneous control of the orientation of an Earth-pointing spacecraft, the energy stored by counter-rotating flywheels, and the angular momentum of the flywheels and control moment gyroscopes used together as all integrated set of actuators for attitude control. General. nonlinear equations of motion are presented in vector-dyadic form, and used to obtain approximate expressions which are then linearized in preparation for design of control laws that include feedback of flywheel kinetic energy error as it means of compensating for damping exerted by rotor bearings. Two flywheel 'steering laws' are developed such that torque commanded by all attitude control law is achieved while energy is stored or discharged at the required rate. Using the International Space Station as an example, numerical simulations are performed to demonstrate control about a torque equilibrium attitude and illustrate the benefits of kinetic energy error feedback.
Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.
Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.
Sounding Rocket One (SR-1), the first flight test of the Adaptable Deployable Entry and Placement Technology (ADEPT), was performed on September 12, 2018. ADEPT is a deployable aeroshell that is stowed for launch and deployed before atmospheric flight to increase the drag area of the spacecraft. The main objectives of the SR-1 flight test were to demonstrate that the ADEPT vehicle deploys exo-atmospherically and to characterize the stability of the vehicle during atmospheric flight. The SR-1 test vehicle was a 0.7-m-diam, 70°-half-angle faceted sphere-cone and was the primary payload on an UP Aerospace Spaceloft launch vehicle from the White Sands Missile Range. ADEPT successfully separated from the spent booster in its stowed configuration, opened above 100 km altitude, and landed in the deployed configuration within White Sands Missile Range. ADEPT was able to reach peak Mach number of 3.1 and was able to show angle-of-attack stability through Mach 0.8, which was the objective of the mission. The aerodynamics and flight mechanics of the vehicle were modeled preflight for performance and range safety predictions. After the flight, the on-board instrumentation was used to reconstruct the flight performance. This paper describes the predictions and postflight reconstruction, and how the predictions compared with the flight data.
On February 18th, 2021, the Mars 2020 entry system successfully delivered the Perseverance rover to the surface of Mars at Jezero Crater. The entry capsule carried instrumentation installed on the heatshield and backshell, named “Mars Entry, Descent, and Landing Instrumentation 2.” The instruments were used to measure the aerodynamic and aerothermodynamic performance of the entry vehicle. Five sensors at two locations (three sensors at one location and two sensors at the second location), including a thermocouple plug, heat flux gauge, and a radiometer, were co-located on the backshell. The sensors were exposed to roughly the same aerodynamic heating but measured these environments in different ways, each with its own set of modeling and measurement error complications. This paper develops a method for blending each of these measurements together in a single algorithm to produce estimates of the aerothermodynamic environments at each backshell location. The approach makes use of the Kalman–Schmidt filter/smoother methodology, where systematic measurement error parameters are modeled as multiplicative states that are estimated by the filter along with the aerothermal states. The results of the sensor fusion approach are expected to be used to inform and improve aerothermal modeling for future Mars entry capsules.
This document describes the trajectory and atmosphere reconstruction of the Mars Exploration Rovers (Spirit and Opportunity) Entry, Descent, and Landing using the New Statistical Trajectory Estimation Program. The approach utilizes a Kalman filter to blend inertial measurement unit data with initial conditions and radar altimetry to obtain the inertial trajectory of the entry vehicle. The nominal aerodynamic database is then used in combination with the sensed accelerations to obtain estimates of the atmosphere-relative state. The reconstructed atmosphere profile is then blended with pre-flight models to construct an estimate of the as-flown atmosphere.
