Brent W. Barbee

Design of spacecraft missions to remove multiple orbital debris objects

The amount of hazardous debris in Earth orbit has been increasing, posing an ever-greater danger to space assets and crewed missions. In January of 2007, a Chinese ASAT test produced approximately 2; 600 pieces of orbital debris. In February of 2009, Iridium 33 collided with an inactive Russian satellite, yielding approximately 1; 300 pieces of debris. These recent disastrous events and the sheer size of the Earth orbiting population make clear the necessity of removing orbital debris. In fact, experts from both NASA and ESA have stated that 10 to 20 pieces of orbital debris need to be removed per year to stabilize the orbital debris environment. However, no spacecraft trajectories have yet been designed for removing multiple debris objects and the size of the debris population makes the design of such trajectories a daunting task. Designing an efficient spacecraft trajectory to rendezvous with each of a large number of orbital debris pieces is akin to the famous Traveling Salesman problem, an NP-complete combinatorial optimization problem in which N cities are to be visited in turn. The goal is to choose the order in which the cities are visited so as to minimize the total path distance traveled. In the case of orbital debris, the pieces of debris to be visited must be selected and ordered such that spacecraft fuel consumption is minimized or at least kept low enough to be feasible. Emergent Space Technologies, Inc. has developed specialized algorithms for designing efficient tour missions for Near-Earth Asteroids that may be applied to the design of efficient spacecraft missions capable of visiting large numbers of orbital debris pieces. The first step is to identify a list of high priority debris targets using the Analytical Graphics, Inc. SOCRATES website and then obtain their state information from Celestrak. The tour trajectory design algorithms will then be used to determine the itinerary of objects and ΔV requirements. These results will shed light on how many debris pieces can be visited for various amounts of propellant, which launch vehicles can accommodate such missions, and how much margin is available for debris removal system payloads.

A Comprehensive Ongoing Survey of the Near-Earth Asteroid Population for Human Mission Accessibility

There are currently 7069 known Near-Earth Asteroids (NEAs) and more are being discovered on a continual basis; it is likely that the total NEA population consists of at least hundreds of thousands of objects. NEAs have orbits that bring them into close proximity with Earth’s orbit, making them both a unique hazard to life on Earth and a unique opportunity for science and exploration. The current presidential administration has proposed that NASA send humans to an asteroid by the mid-2020s as part of the Flexible Path architecture. A study was therefore undertaken to identify NEAs that are accessible for round-trip human missions using a heavy-lift launch architecture. A fully parametrized, highly ecient algorithm was developed to accomplish this, allowing changes in vehicle parameters to be studied and enabling the accessibility analysis to keep pace with the NEA discovery rate, which is increasing as new telescopes, such as Pan-STARRS, become active. To date, the accessibility analysis algorithm has identied 59 accessible

A Guidance and Navigation Strategy for Rendezvous and Proximity Operations with a Noncooperative Spacecraft in Geosynchronous Orbit

The feasibility and benefits of various spacecraft servicing concepts are currently being assessed, and all require that servicer spacecraft perform rendezvous, proximity operations, and capture operations with the spacecraft to be serviced. There are many high-value commercial and military spacecraft located in geosynchronous orbit (GEO) which may be candidates for servicing, but GEO is a regime in which rendezvous and capture operations are not commonplace; further, most GEO spacecraft were not designed to be cooperative rendezvous targets, and some may even be completely nonfunctional and therefore potentially tumbling. In this work we present elements of a guidance and navigation strategy for rendezvous and proximity operations with a noncooperative spacecraft in GEO. Translational Δv is assessed for a passively safe co-elliptic rendezvous approach sequence that is followed by injection into a safety ellipse about a noncooperative tumbling spacecraft and, ultimately, final approach to capture. Covariance analysis is presented for a simulation of range and bearing measurements throughout the rendezvous and proximity operations sequence.

A Lean, Fast Mars Round-trip Mission Architecture: Using Current Technologies for a Human Mission in the 2030s

We present a lean fast-transfer architecture concept for a first human mission to Mars that utilizes current technologies and two pivotal parameters: an end-to-end Mars mission duration of approximately one year, and a deep space habitat of approximately 50 metric tons. These parameters were formulated by a 2012 deep space habitat study conducted at the NASA Johnson Space Center (JSC) that focused on a subset of recognized high- engineering-risk factors that may otherwise limit space travel to destinations such as Mars or near-Earth asteroid (NEA)s. With these constraints, we model and promote Mars mission opportunities in the 2030s enabled by a combination of on-orbit staging, mission element pre-positioning, and unique round-trip trajectories identified by state-of-the-art astrodynamics algorithms.

Real-time, propellant-optimized spacecraft motion planning under Clohessy-Wiltshire-Hill dynamics

This paper presents a sampling-based motion planning algorithm for real-time, propellant-optimized autonomous spacecraft trajectory generation in near-circular orbits. Specifically, this paper leverages recent algorithmic advances in the field of robot motion planning to the problem of impulsively-actuated, propellant-optimized rendezvous and proximity operations under the Clohessy-Wiltshire-Hill (CWH) dynamics model. The approach calls upon a modified version of the Fast Marching Tree (FMT*) algorithm to grow a set of feasible and actively-safe trajectories over a deterministic, low-dispersion set of sample points covering the free state space. Key features of the proposed algorithm include: (i) theoretical guarantees of trajectory safety and performance, (ii) real-time implementability, and (iii) generality, in the sense that a large class of constraints can be handled directly. As a result, the proposed algorithm offers the potential for widespread application, ranging from on-orbit satellite servicing to orbital debris removal and autonomous inspection missions.

Mission Design and Analysis for Suborbital Intercept and Fragmentation of an Asteroid with Very Short Warning Time

impact scenarios. In this paper we explore the lower bound on actionable warning time by investigating the performance of notional upgraded Intercontinental Ballistic Missiles (ICBMs) to carry Nuclear Explosive Device (NED) payloads to intercept and disrupt a hypothetical incoming NEO at high altitudes (generally at least 2500 km above Earth). We conduct this investigation by developing optimal NEO intercept trajectories for a range of cases and comparing their performances. Our results show that suborbital NEO intercepts using Minuteman III or SM-3 IIA launch vehicles could achieve NEO intercept a few minutes prior to when the NEO would strike Earth. We also nd that more powerful versions of the launch vehicles (e.g., total V 9.5{11 km/s) could intercept incoming NEOs several hours prior to when the NEO would strike Earth, if launched at least several days prior to the time of intercept. Finally, we discuss a number of limiting factors and practicalities that aect whether the notional systems we describe could become feasible.

Multi-organization — Multi-discipline effort developing a mitigation concept for planetary defense

There have been significant recent efforts in addressing mitigation approaches to neutralize Potentially Hazardous Asteroids (PHA). One such research effort was performed in 2015 by an integrated, inter-disciplinary team of asteroid scientists, energy deposition modeling scientists, payload engineers, orbital dynamicist engineers, spacecraft discipline engineers, and systems / architecture engineers from NASAs Goddard Space Flight Center (GSFC) and the Department of Energy (DoE) / National Nuclear Security Administration (NNSA) laboratories (Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratories (LLNL) and Sandia National Laboratories). The study team collaborated with GSFCs Integrated Design Centers Mission Design Lab (MDL) which engaged a team of GSFC flight hardware discipline engineers to work with GSFC, LANL, and LLNL Near-Earth Asteroid (NEA)-related subject matter experts during a one-week intensive concept formulation study in an integrated concurrent engineering environment. This team has analyzed the first of several distinct study cases for a multi-year NASA research grant. This Case 1 study references the NEA named Bennu as the notional target due to the availability of a very detailed Design Reference Asteroid (DRA) model for its orbit and physical characteristics (courtesy of the Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer [OSIRIS-REx] mission team). The research involved the formulation and optimization of spacecraft trajectories to intercept Bennu, overall mission and architecture concepts, and high-fidelity modeling of both kinetic impact (spacecraft collision to change a NEAs momentum and orbit) and nuclear detonation effects on Bennu, for purposes of deflecting Bennu.

A Class of Selenocentric Retrograde Orbits With Innovative Applications to Human Lunar Operations

Selenocentric distant retrograde orbits with radii from approx. 12,500 km to approx. 25,000 km are assessed for stability and for suitability as crewed command and control infrastructure locations in support of telerobotic lunar surface operations and interplanetary human transport. Such orbits enable consistent transits to and from Earth at virtually any time if they are coplanar with the Moons geocentric orbit. They possess multiple attributes and applications distinct from NASAs proposed destination orbit for a redirected asteroid about 70,000 km from the Moon.

An architecture for mitigating near earth object's impact to the earth

Near-Earth Objects (NEOs), like species extinction events, present a great threat to our home planet and human kind. The motivation of designing this architectural framework is the current lack of structured architecture for the process of detecting, characterizing and mitigating these NEO threats. Due to the recent establishment of the NASAs Planetary Defense Coordination Office (PDCO), it is critical to link the individual facilities conducting separate research with an objective of forming a clearly defined collaborative system based on data reporting and sharing. The architectural framework is designed for integrating the process of detecting, characterizing and mitigating NEO threats. The goal of designing the architecture is to organize current data and resources into useful information and correlate that information with the goals of the NEO mitigation study. The architectural framework will enable scientists, organizations, and decision makers to locate, identify and resolve semantic confusion, properties, facts, constraints and issues with potentially hazardous asteroids. Our major focus is to design the data and information flow that models the complete process from NEO detection, to designing the mitigation strategies. A secondary focus is to develop a system-of-systems architecture to describe the supporting infrastructure for the framework. The framework is also built with the opportunity to leverage future assets from the broader Planetary Defense (PD) community, and identify/speed up relevant PD research and response.i

Investigations of short warning time response options for hazardous near-Earth objects

This paper describes an assessment of capabilities for two planetary defense techniques: Kinetic Energy Impactors (KEIs) and Nuclear Explosive Devices (NEDs), including both Near Earth Asteroid (NEA) deflection and disruption. These studies will help us understand how energetic systems affect asteroidal (or cometary) bodies, and how to deliver energetic payloads to target objects under short warning time conditions, accounting for real-life constraints including payload integration and spacecraft lifecycle. Techniques for spacecraft trajectory optimization and mission design, scientific knowledge of asteroid and comet characteristics and chemistry, and energetic systems modeling will be combined to produce designs and strategies that will inform effective, reliable responses to short warning time NEA impact scenarios.