Melissa L. McGuire

Artificial Gravity Vehicle Design Option for NASA's Human Mars Mission Using "Bimodal" NTR Propulsion

Recent human Mars exploration studies at NASA have focused on a split mission approach involving predeployment of surface and orbital cargo elements followed by piloted missions with long surface stays (-500 days) and “l-way” transit times of -6 to 7 months. In the event an aborted landing or major surface system failure forces an early return to the crew transfer vehicle (CTV), astronauts could spend the entire mission duration (-900 days) in a weightless environment. An artificial gravity CTV design capable of countering the potentially debilitating physiological effects of “zero gravity” is described which uses “bimodal” nuclear thermal rocket (NTR) propulsion. With its high specific impulse (Isp -850-l 000 s), attractive engine thrust-to-weight ratio (-3-i 0) and demonstrated feasibility, the NTR is the most promising propulsion technology for future human exploration missions to the Moon, Mars and near Earth asteroids. Because only a minuscule amount of enriched uranium235 fuel is consumed in a NTR during the primary propulsion maneuvers of a typical Mars mission, engines configured for both propulsive thrust and modest power generation (referred to as “bimodal” operation) provide the basis for a robust, “power-rich” stage enabling a propulsive Mars capture capability for the CTV. A common “bimodal” NTR (BNTR) “core” stage powered by three -15 thousand pounds force (klbf) BNTRs supplies 50 kWe of total electrical power for crew life support and an active refrigeration system enabling long term, “zero-boiloff” liquid hydrogen (LH2) storage. On the piloted CTV, the bimodal NTR core stage is connected to the inflatable -----------------------------------------------------------------------*Ph.D./Nuclear Engineering, Senior Member AIAA ‘*Aerospace Engineer, Member AIAA “TransHab” crew module via an innovative, spinelike “saddle truss” (approximately 22 meters in length) which is open underneath to allow easy jettisoning of the “in-line” LH2 propellant tank following the trans-Mars injection (TMI) burn. The CTV then initiates vehicle rotation at o 4 revolutions per minute (rpm) to provide the TransHab crew with a Mars gravity field (-0.38 g E) during the outbound transit. A higher rotation rate (w 6 rpm) can provide -0.8 gE on the return leg to help reacclimate the crew to Earth’s gravity after their -500 day stay at Mars. In addition to supplying artificial gravity and abundant power for the crew, a Mars architecture using BNTR transfer vehicles also has a lower total launch mass, fewer transportation system elements and simpler mission operations than competing “non-nuclear” chemical and solar electric propulsion (SEP) options. INTRODUCTION AND BACKGROUND Over the last 3 years, NASA’s intercenter Mars Exploration Study Team has been evaluating a split cargo / piloted mission approach for sending humans to Mars in the 2014 timeframe. Payload masses have continued to be refined and updatedl, and a variety of space transportation technology options have been examined*,s. In the FY98 reference mission profile, the crew traveled to Mars under “zero gravity” conditions and landed on its surface in a common transit / habitat module integrated into an aerobraked lander configuration. Two cargo flights preceded the piloted mission and were used to predeploy surface assets and a separate transfer stage for returning the crew to Copyright

In-Space Transportation for NASA's Evolvable Mars Campaign

As the nation embarks on a new and bold journey to Mars, significant work is being done to determine what that mission and those architectural elements will look like. The Evolvable Mars Campaign, or EMC, is being evaluated as a potential approach to getting humans to Mars. Built on the premise of leveraging current technology investments and maximizing element commonality to reduce cost and development schedule, the EMC transportation architecture is focused on developing the elements required to move crew and equipment to Mars as efficiently and effectively as possible both from a performance and a programmatic standpoint. Over the last 18 months the team has been evaluating potential options for those transportation elements. One of the key aspects of the EMC is leveraging investments being made today in missions like the Asteroid Redirect Mission (ARM) mission using derived versions of the Solar Electric Propulsion (SEP) propulsion systems and coupling them with other chemical propulsion elements that maximize commonality across the architecture between both transportation and Mars operations elements. This paper outlines the broad trade space being evaluated including the different technologies being assessed for transportation elements and how those elements are assembled into an architecture. Impacts to potential operational scenarios at Mars are also investigated. Trades are being made on the size and power level of the SEP vehicle for delivering cargo as well as the size of the chemical propulsion systems and various mission aspects including Inspace assembly and sequencing. Maximizing payload delivery to Mars with the SEP vehicle will better support the operational scenarios at Mars by enabling the delivery of landers and habitation elements that are appropriately sized for the mission. The purpose of this investigation is not to find the solution but rather a suite of solutions with potential application to the challenge of sending cargo and crew to Mars. The goal is that, by building an architecture intelligently with all aspects considered, the sustainable Mars program wisely invests limited resources enabling a long-term human Mars exploration program.

High Power MPD Nuclear Electric Propulsion (NEP) for Artificial Gravity HOPE Missions to Callisto

The following paper documents the results of a one‐year multi‐center NASA study on the prospect of sending humans to Jupiter’s moon, Callisto, using an all Nuclear Electric Propulsion (NEP) space transportation system architecture with magnetoplasmadynamic (MPD) thrusters. The fission reactor system utilizes high temperature uranium dioxide (UO2) in tungsten (W) metal matrix “cermet” fuel and electricity is generated using advanced dynamic Brayton power conversion technology. The mission timeframe assumes on‐going human Moon and Mars missions and existing space infrastructure to support launch of cargo and crewed spacecraft to Jupiter in 2041 and 2045, respectively.

Concept designs for NASA's Solar Electric Propulsion Technology Demonstration Mission

Multiple Solar Electric Propulsion Technology Demonstration Mission were developed to assess vehicle performance and estimated mission cost. Concepts ranged from a 10,000 kilogram spacecraft capable of delivering 4000 kilogram of payload to one of the Earth Moon Lagrange points in support of future human-crewed outposts to a 180 kilogram spacecraft capable of performing an asteroid rendezvous mission after launched to a geostationary transfer orbit as a secondary payload. Low-cost and maximum Delta-V capability variants of a spacecraft concept based on utilizing a secondary payload adapter as the primary bus structure were developed as were concepts designed to be co-manifested with another spacecraft on a single launch vehicle. Each of the Solar Electric Propulsion Technology Demonstration Mission concepts developed included an estimated spacecraft cost. These data suggest estimated spacecraft costs of

Combining Solar Electric Propulsion and chemical propulsion for crewed missions to Mars

200 million -

Concurrent Mission and Systems Design at NASA Glenn Research Center: The Origins of the COMPASS Team

300 million if 30 kilowatt-class solar arrays and the corresponding electric propulsion system currently under development are used as the basis for sizing the mission concept regardless of launch vehicle costs. The most affordable mission concept developed based on subscale variants of the advanced solar arrays and electric propulsion technology currently under development by the NASA Space Technology Mission Directorate has an estimated cost of

Use of High-Power Brayton Nuclear Electric Propulsion (NEP) for a 2033 Mars Round-Trip Mission

50M and could provide a Delta-V capability comparable to much larger spacecraft concepts.

“Bimodal” Nuclear Thermal Rocket (BNTR) Propulsion for an Artificial Gravity HOPE Mission to Callisto

This paper documents the results of an investigation of human Mars mission architectures that leverage near-term technology investments and infrastructures resulting from the planned Asteroid Redirect Robotic Mission (ARRM), including high-power Solar Electric Propulsion (SEP) and a human presence in Lunar Distant Retrograde Orbit (LDRO). The architectures investigated use a combination of SEP and chemical propulsion elements. Through this combination of propulsion technologies, these architectures take advantage of the high efficiency SEP propulsion system to deliver cargo, while maintaining the faster trip times afforded by chemical propulsion for crew transport. Evolved configurations of the Asteroid Redirect Vehicle (ARV) are considered for cargo delivery. Sensitivities to SEP system design parameters, including power level and propellant quantity, are presented. For the crew delivery, liquid oxygen and methane stages were designed using engines common to future human Mars landers. Impacts of various Earth departure orbits, Mars loiter orbits, and Earth return strategies are presented. The use of the Space Launch System for delivery of the various architecture elements was also investigated and launch vehicle manifesting, launch scheduling and mission timelines are also discussed. The study results show that viable Mars architecture can be constructed using LDRO and SEP in order to take advantage of investments made in the ARRM mission.

“Bimodal” NTR and LANTR propulsion for human missions to Mars/Phobos

Abstract Established at the NASA Glenn Research Center (GRC) in 2006 to meet the need for rapid mission analysis and multi-disciplinary systems design for in-space and human missions, the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team is a multidisciplinary, concurrent engineering group whose primary purpose is to perform integrated systems analysis, but it is also capable of designing any system that involves one or more of the disciplines present in the team. The authors were involved in the development of the COMPASS team and its design process, and are continuously making refinements and enhancements. The team was unofficially started in the early 2000s as part of the distributed team known as Team JIMO (Jupiter Icy Moons Orbiter) in support of the multi-center collaborative JIMO spacecraft design during Project Prometheus. This paper documents the origins of a concurrent mission and systems design team at GRC and how it evolved into the COMPASS team, including defining the process, gathering the team and tools, building the facility, and performing studies.

Radioisotope Electric Propulsion Centaur Orbiter Spacecraft Design Overview

The Revolutionary Aerospace Systems Concepts (RASC) team, led by the NASA Langley Research Center, is tasked with exploring revolutionary new approaches to enabling NASA to achieve its strategic goals and objectives in future missions. This paper provides the details from the 2004–2005 RASC study of a point‐design that uses a high‐power nuclear electric propulsion (NEP) based space transportation architecture to support a manned mission to Mars. The study assumes a high‐temperature liquid‐metal cooled fission reactor with a Brayton power conversion system to generate the electrical power required by magnetoplasmadynamic (MPD) thrusters. The architecture includes a cargo vehicle with an NEP system providing 5 MW of electrical power and a crewed vehicle with an NEP system with two reactors providing a combined total of 10 MW of electrical power. Both vehicles use a low‐thrust, high‐efficiency (5000 sec specific impulse) MPD system to conduct a spiral‐out of the Earth gravity well, a low‐thrust heliocentric ...