Thermal Protection System Requirements for Future Planetary Entry and Aerocapture Missions

Thermal protection systems are a critical component of planetary exploration, enabling probes to enter the atmosphere and perform in-situ measurements. The aero-thermal conditions encountered during entry are destination and vehicle dependent, ranging from relatively benign conditions at Mars and Titan, to extreme conditions at Venus and Jupiter. The thermal protection system is a single-point-of-failure for both entry probe and aerocapture missions, and hence must be qualified using ground tests to ensure mission success. The high density Carbon-Phenolic which was used in the Galileo and the Pioneer Venus missions is no longer available due to the lack of the manufacturing base for its raw materials. To address the need for Venus and outer planet missions, NASA has developed the Heatshield for Extreme Environment Entry Technology (HEEET). The present study uses the Aerocapture Mission Analysis Tool (AMAT) to perform a comparative study of the thermal protection system requirements for various planetary destinations and the applicability of HEEET for future entry and aerocapture missions. The heat rate and stagnation pressure for aerocapture is significantly less compared to probe entry. The large heat loads during aerocapture present a challenge, but HEEET is capable of sustaining large heat loads within a reasonable TPS mass fraction.Comment: 14 pages, 12 figure

Planetary Entry Probe Dataset: Analysis and Rules of Thumb for Future Missions

Since the beginning of robotic interplanetary exploration nearly six decades ago, successful atmospheric entry has been accomplished at Venus, Earth, Mars, Jupiter, and Titan. More entry probe missions are planned to Venus, Titan, and Uranus in the next decade. Atmospheric entry subjects the vehicle to rapid deceleration and aerothermal loads which the vehicle must be designed for, to deliver the robotic instruments inside the atmosphere. The design of planetary probes and their mission architecture is complex, and involves various engineering constraints such as peak deceleration, heating rate, heating load, and communications which must be satisfied within the budget and schedule of cost constrained mission opportunities. Engineering design data from previous entry probe missions serve as a valuable reference for designing future missions. The present study compiles an augmented version of the blue book entry probe dataset, performs a comparative analysis of the entry conditions, and provides engineering rules of thumb for design of future missions. Using the dataset, the present study proposes a new empirical correlation which aims to more accurately predict the thermal protection system mass fraction for high heat load conditions during entry and aerocapture at Uranus and Neptune.Comment: 15 pages, 15 figure

A Low Cost Mars Aerocapture Technology Demonstrator

The ability to launch small secondary payloads to Mars on future science missions present an exciting opportunity for demonstration of advanced technologies for planetary exploration such as aerocapture. Over the years, several aerocapture technology demonstration missions have been proposed but none could be realized, causing the technology to become dormant as it is seen as too risky and expensive to be used on a science mission. The present study proposes a low-cost Mars aerocapture demonstration concept as a secondary payload, and could pave the way for future low-cost small interplanetary orbiter missions. The proposed mission heavily leverages the mission architecture and the flight hardware of the MarCO spacecraft for a low cost mission. The 35 kg technology demonstrator would launch as an ESPA secondary payload on a future Mars mission, and would be deployed from the upper stage soon after primary spacecraft separation. The vehicle then independently cruises to Mars, where it will perform aerocapture and insert a 6U MarCO heritage CubeSat to a 200 x 2000 km orbit. The mission architecture incorporates a number of cost saving approaches, and is estimated to fit within a 30M cost cap, of which 10M is allocated for technology development and risk reduction.Comment: 14 pages, 9 figure

Aerocapture Enabled Fast Uranus Orbiter Missions

At the far reaches of the outer Solar System, the ice giants remain the last class of planets yet to be studied using orbiters. The 2023-2032 Planetary Science Decadal Survey has underscored the importance of the ice giants in understanding the origin, formation, and evolution of our Solar System. The enormous heliocentric distance of Uranus presents considerable mission design challenges, the most important being able to reach Uranus within a reasonable time. The present study presents two examples of aerocapture enabled short flight time, fast trajectories for Uranus orbiter missions, and highlights the enormous benefits provided by aerocapture. The first is an EEJU trajectory with a launch opportunity in July 2031 with a flight time of 8 years. The second is an EJU trajectory with a launch opportunity in June 2034 with a flight time of only 5 years. Using the Falcon Heavy Expendable, the available launch capability is 4950 kg and 1400 kg respectively for the two trajectories. Both trajectories have a high arrival speed of 20 km/s, which provides sufficient corridor width for aerocapture. Compared to propulsive insertion architectures which take 13 to 15 years, the fast trajectories offer significant reduction in the flight time.Comment: 9 pages, 6 figure

Aerocapture: A Historical Review and Bibliometric Data Analysis from 1980 to 2023

Aerocapture is a technique which uses atmospheric drag to decelerate a spacecraft and achieve nearly fuel-free orbit insertion from an interplanetary trajectory. The present study performs a historical review of the field, and a bibliometric data analysis of the literature from 1980 to 2023. The data offers insights into the evolution of the field, current state of research, and pathways for its continued development. The data reveal a pattern in the rise of publications, followed by a period of stagnation, which repeats itself approximately once every decade. Mars is the most studied destination, while Uranus is the least studied. Prior to 2013, NASA centers produced the most publications and are the most cited in the field. However, academic institutions produced the majority of publications in the last decade. The United States continues to be the leading country in terms of publications, followed by China. The Journal of Spacecraft and Rockets is the leading source of publications, both in terms of number and citations. NASA is the leading funding source, followed by the National Natural Science Foundation of China. A proposed low-cost Earth flight demonstration of aerocapture will greatly reduce the risk for future science missions.Comment: 19 pages, 20 figure

Launch Vehicle High-Energy Performance Dataset

The choice of the launch vehicle is an important consideration during the preliminary planning of interplanetary missions. The launch vehicle must be highly reliable, capable of imparting sufficient energy to the spacecraft to inject it on to an Earth-escape trajectory, and must fit within the cost constraints of the mission. Over the recent past, the most commonly used launchers for interplanetary missions include the Atlas V401, Atlas V551, Delta IVH, and Falcon Heavy expendable version. The NASA Launch Vehicle Performance website maintains a tool to help mission planners evaluate various launch vehicles during mission studies. However, there is no comprehensive dataset which can be used to quickly compare the launch performance and launch cost of various options. The present study compiles a dataset of the high energy performance of existing and planned launchers from open-source data and performs a quantitative comparison of the launch performance and the launch cost per kg. The Falcon Heavy expendable offers the lowest cost-per-kg for high-energy launches, with only $0.075M per kg. The Vulcan Centaur offers comparable performance to the Falcon Heavy. The results indicate Falcon Heavy Expendable and the Vulcan Centaur will be the likely choice for several future missions.Comment: 6 pages, 4 figure

Performance Benefit of Aerocapture for the Design Reference Mission Set

Aerocapture is a maneuver which uses aerodynamic drag to slow down a spacecraft in a single pass through the atmosphere. All planetary orbiters to date have used propulsive orbit insertion. Aerocapture is a promising alternative, especially for small satellite missions and missions to the ice giants. The large {\Delta}V requirement makes it practically impossible for small satellites to enter low circular orbits. Aerocapture can enable insertion of low-cost satellites into circular orbits around Mars and Venus. For ice giant missions, aerocapture can enable orbit insertion from fast arrival trajectories which are impractical with propulsive insertion. By utilizing the atmospheric drag to impart the {\Delta}V, aerocapture can offer significant propellant mass and cost savings for a wide range of planetary missions. The present study analyzes the performance benefit offered by aerocapture for a set of design reference missions and their applications to future Solar System exploration from Venus to Neptune. The estimated performance benefit for aerocapture in terms of delivered mass increase are: Venus (92%), Earth (108%), Mars (17%), and Titan (614%), Uranus (35%), and Neptune (43%). At Uranus and Neptune, aerocapture is a mission enabling technology for orbit insertion from fast arrival interplanetary trajectories.Comment: 11 pages, 8 figure

Aerocapture Design Reference Missions for Solar System Exploration: from Venus to Neptune

Aerocapture is the technique of using planetary atmospheres to decelerate a spacecraft in a single pass to achieve nearly fuel-free orbit insertion. Aerocapture has been extensively studied since the 1980s but has never been flown yet. The entry conditions encountered during aerocapture are strongly destination dependent, and performance benefit offered by aerocapture is also destination dependent. Aerocapture is applicable to all atmosphere-bearing destinations with the exception of Jupiter and Saturn, whose extreme entry conditions make aerocapture infeasible. A recent study by the NASA Science Mission Directorate highlighted the need for baseline design reference missions, as a starting point for system level architecture studies. The present study uses the Aerocapture Mission Analysis Tool (AMAT) to compile a list of design reference missions at Venus, Earth, Mars, Titan, Uranus, and Neptune. These reference missions can provide an initial assessment of the feasibility of aerocapture for a proposed mission, and provide intial baseline values for more detailed system studies. The reference mission set provides a quick estimate of the entry conditions, control requirements, and aero-thermal loads for architectural level studies.Comment: 12 pages, 7 figure

Comparison of Lift and Drag Modulation Control for Ice Giant Aerocapture Missions

Aerocapture is an orbit insertion technique which uses atmospheric drag from a single pass to decelerate a spacecraft. Compared to conventional propulsive insertion, aerocapture can impart large velocity changes to the spacecraft with almost no propellant. At the far reaches of the outer Solar System, the ice giants remain the last class of planets to be explored using orbiters. Their enormous heliocentric distance presents significant mission design challenges, particularly the large $\Delta$V required for orbit insertion. This makes aerocapture an attractive method of orbit insertion, but also challenging due to the comparatively large navigation and atmospheric uncertainties. The present study performs a comparison of the lift and drag modulation control and their implications for future missions. Lift modulation provides nearly twice the entry corridor width as drag modulation, and can thus accommodate larger uncertainties. Lift modulation offers continuous control throughout the flight enabling it to adjust the trajectory in response to the actual density profile encountered. Drag modulation offers much more benign aero-thermal conditions compared to lift modulation. With drag modulation, there is no control authority after the drag skirt jettison making the vehicle more susceptible to exit state errors from density variations encountered after the jettison event.Comment: 7 pages, 3 figure

Enabling and Enhancing Science Exploration Across the Solar System: Aerocapture Technology for SmallSat to Flagship Missions

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