More Effective Human Spaceflight Programs and Their International Security Implications

NASA can more effectively perform its missions by transferring its aeronautic responsibilities to the Federal Aviation Administration and be renamed the National Space Agency. The U.S. must also recognize that space is an emerging arena of international competition and conflict and militarily protect its space assets from China which seeks to use space to restrict the U.S.\u27 ability to defend its strategic interests in regions such as the Western Pacific

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

n/

Analytical theories for spacecraft entry into planetary atmospheres and design of planetary probes

This dissertation deals with the development of analytical theories for spacecraft entry into planetary atmospheres and the design of entry spacecraft or probes for planetary science and human exploration missions. Poincaré’s method of small parameters is used to develop an improved approximate analytical solution for Yaroshevskii’s classical planetary entry equation for the ballistic entry of a spacecraft into planetary atmospheres. From this solution, other important expressions are developed including deceleration, stagnation-point heat rate, and stagnation-point integrated heat load. The accuracy of the solution is assessed via numerical integration of the exact equations of motion. The solution is also compared to the classical solutions of Yaroshevskii and Allen and Eggers. The new second-order analytical solution is more accurate than Yaroshevskii’s fifth-order solution for a range of shallow (-3 deg) to steep (up to -90 deg) entry flight path angles, thereby extending the range of applicability of the solution as compared to the classical Yaroshevskii solution, which is restricted to an entry flight path of approximately -40 deg. Universal planetary entry equations are used to develop a new analytical theory for ballistic entry of spacecraft for moderate to large initial flight path angles. Chapman’s altitude variable is used as the independent variable. Poincaré’s method of small parameters is used to develop an analytical solution for the velocity and the flight path angle. The new solution is used to formulate key expressions for range, time-of-flight, deceleration, and aerodynamic heating parameters (e.g., stagnation-point heat rate, total stagnation-point heat load, and average heat input). The classical approximate solution of Chapman’s entry equation appears as the zero-order term in the new solution. The new solution represents an order of magnitude enhancement in the accuracy compared to existing analytical solutions for moderate to large entry flight path angles. The analytical theory is very accurate for moderate to large entry angles and for any entry speed. A new analytical theory is developed for ballistic entry at circular speed for zero initial flight path angle and for ballistic entry at circular speed for very small to large initial flight path angles. Two separate solutions for zero and non-zero initial flight path angles are needed to avoid a singularity. The classical Yaroshevskii’s solution enters as the zero-order term in the solutions. Using the new solutions, other important expressions are developed such as time-of-flight, range, deceleration, and aerodynamic heating parameters (e.g. average heat input, stagnation-point heat rate, and total stagnation-point heat load). Large-scale human exploration of Mars and in situ exploration of Venus pose great challenges for entry, descent, and landing of spacecraft. The Adaptive Deployable Entry and Placement Technology (ADEPT), a mechanically deployable decelerator, presents an enabling alternative to the traditional rigid aeroshell technology. ADEPT helps in lowering the ballistic coefficient of an entry vehicle and also presents attractive options for lifting and guided entry. Optimal trajectory solutions which minimize peak deceleration and peak heat-flux are computed for four different control strategies. The deployable decelerator for human Mars missions (requiring a landed mass of 40 mt) presents an acceptable entry environment—peak heat-flux of \u3c 80 W/cm2, and peak deceleration of less than 4 G (compared to 200 W/cm2 and 15 G for Mars Science Laboratory respectively). For lifting and guided entry for Venus in situ missions, ADEPT could lead to a two-order-of-magnitude decrease in peak deceleration and to a 50% decrease in peak heat-flux compared to conventional rigid aeroshell technology. There exist a number of attractive trajectory candidates for round-trip human missions to Mars and Venus. However, the speeds the spacecraft will encounter during Earth reentry are unprecedented. NASA’s Stardust entry robotic spacecraft which entered Earth (ballistic entry) at a speed of 12.9 km/s is the fastest reentry achieved by a manmade object to date. The goal is to assess the feasibility of Earth reentry for fast free returns Mars and Venus human missions within human tolerance limits and capabilities of current state-of-art vehicle and thermal protection system technologies

Aerial Platform Design Options for a Life-Finding Mission at Venus

Mounting evidence of chemical disequilibria in the Venusian atmosphere has heightened interest in the search for life within the planet’s cloud decks. Balloon systems are currently considered to be the superior class of aerial platform for extended atmospheric sampling within the clouds, providing the highest ratio of science return to risk. Balloon-based aerial platform designs depend heavily on payload mass and target altitudes. We present options for constant- and variable-altitude balloon systems designed to carry out science operations inside the Venusian cloud decks. The Venus Life Finder (VLF) mission study proposes a series of missions that require extended in situ analysis of Venus cloud material. We provide an overview of a representative mission architecture, as well as gondola designs to accommodate a VLF instrument suite. Current architecture asserts a launch date of 30 July 2026, which would place an orbiter and entry vehicle at Venus as early as November 29 of that same year

Mission Architecture to Characterize Habitability of Venus Cloud Layers via an Aerial Platform

Venus is known for its extreme surface temperature and its sulfuric acid clouds. But the cloud layers on Venus have similar temperature and pressure conditions to those on the surface of Earth and are conjectured to be a possible habitat for microscopic life forms. We propose a mission concept to explore the clouds of Venus for up to 30 days to evaluate habitability and search for signs of life. The baseline mission targets a 2026 launch opportunity. A super-pressure variable float altitude balloon aerobot cycles between the altitudes of 48 and 60 km, i.e., primarily traversing the lower, middle, and part of the upper cloud layers. The instrument suite is carried by a gondola design derived from the Pioneer Venus Large Probe pressure vessel. The aerobot transmits data via an orbiter relay combined with a direct-to-Earth link. The orbiter is captured into a 6-h retrograde orbit with a low, roughly 170-degree, inclination. The total mass of the orbiter and entry probe is estimated to be 640 kg. An alternate concept for a constant float altitude balloon is also discussed as a lower complexity option compared to the variable float altitude version. The proposed mission would complement other planned missions and could help elucidate the limits of habitability and the role of unknown chemistry or possibly life itself in the Venus atmosphere

Venus Life Finder Habitability Mission: Motivation, Science Objectives, and Instrumentation

For over half a century, scientists have contemplated the potential existence of life within the clouds of Venus. Unknown chemistry leaves open the possibility that certain regions of the Venusian atmosphere are habitable. In situ atmospheric measurements with a suite of modern instruments can determine whether the cloud decks possess the characteristics needed to support life as we know it. The key habitability factors are cloud particle droplet acidity and cloud-layer water content. We envision an instrument suite to measure not only the acidity and water content of the droplets (and their variability) but additionally to confirm the presence of metals and other non-volatile elements required for life’s metabolism, verify the existence of organic material, and search for biosignature gases as signs of life. We present an astrobiology-focused mission, science goals, and instruments that can be used on both a large atmospheric probe with a parachute lasting about one hour in the cloud layers (40 to 60 km) or a fixed-altitude balloon operating at about 52 km above the surface. The latter relies on four deployable mini probes to measure habitability conditions in the lower cloud region. The mission doubles as a preparation for sample return by determining whether a subset of cloud particles is non-liquid as well as characterizing the heterogeneity of the cloud particles, thereby informing sample collection and storage methods for a return journey to Earth

Venus Life Finder Missions Motivation and Summary

Finding evidence of extraterrestrial life would be one of the most profound scientific discoveries ever made, advancing humanity into a new epoch of cosmic awareness. The Venus Life Finder (VLF) missions feature a series of three direct atmospheric probes designed to assess the habitability of the Venusian clouds and search for signs of life and life itself. The VLF missions are an astrobiology-focused set of missions, and the first two out of three can be launched quickly and at a relatively low cost. The mission concepts come out of an 18-month study by an MIT-led worldwide consortium