The low-cost and short-lead time of small satellites
has led to their use in science-based missions, earth observation,
and interplanetary missions. Today, they are also key instruments
in orchestrating technological demonstrations for on-orbit
operations (O3) such as inspection and spacecraft servicing with
planned roles in active debris removal and on-orbit assembly.
This paper provides an overview of the robotics and autonomous
systems (RASs) technologies that enable robotic O3 on smallsat
platforms. Major RAS topics such as sensing & perception,
guidance, navigation & control (GN&C) microgravity mobility
and mobile manipulation, and autonomy are discussed from the
perspective of relevant past and planned missions.
This paper examines the rotational motion of a nearly axisymmetric rocket type system with uniform burn of its propellant. The asymmetry comes from a slight difference in the transverse principal moments of inertia of the system, which then results in a set of nonlinear equations of motion even when no external torque is applied to the system. It is often difficult, or even impossible, to generate analytic solutions for such equations; closed form solutions are even more difficult to obtain. In this paper, a perturbation-based approach is employed to linearize the equations of motion and generate analytic solutions. The solutions for the variables of transverse motion are analytic and a closed-form solution to the spin rate is suggested. The solutions are presented in a compact form that permits rapid computation. The approximate solutions are then applied to the torque-free motion of a typical solid rocket system and the results are found to agree with those obtained from the numerical solution of the full non-linear equations of motion of the mass varying system.
Variable mass systems are a classic example of open systems in classical mechanics with rockets being a standard practical example. Due to the changing mass, the angular momentum of these systems is not generally conserved. Here, we show that the angular momentum vector of a free variable mass system is fixed in inertial space and, thus, is a partially conserved quantity. It is well known that such conservation rules allow simpler approaches to solving the equations of motion. This is demonstrated by using a graphical technique to obtain an analytic solution for the second Euler angle that characterizes nutation in spinning bodies.
In classical mechanics, the ?geometry of motion? refers to a development to visualize the motion of freely spinning bodies. In this paper, such an approach of studying the rotational motion of axisymmetric variable mass systems is developed. An analytic solution to the second Euler angle characterizing nutation naturally falls out of this method, without explicitly solving the nonlinear differential equations of motion. This is used to examine the coning motion of a free axisymmetric cylinder subject to three idealized models of mass loss and new insight into their rotational stability is presented. It is seen that the angular speeds for some configurations of these cylinders grow without bounds. In spite of this phenomenon, all configurations explored here are seen to exhibit nutational stability, a desirable property in solid rocket motors.
Space telescopes are our ?eyes in the sky? that enable unprecedented
astronomy missions and also permit Earth
observation integral to science and national security. On
account of the increased spatial resolution, spectral coverage,
and signal-to-noise ratio, there is a constant clamour
for larger aperture telescopes by the science and surveillance
communities. This paper addresses a 25 m modular
telescope operating in the visible wavelengths of the electromagnetic
spectrum; such a telescope located at geostationary
Earth orbit would permit 1 m spatial resolution of
a location on Earth. Specifically, it discusses the requirements
and architectural options for a robotic assembly
system, called Robotic Agent for Space Telescope Assembly
(RASTA). Aspects of a first-order design and initial
laboratory test-bed developments are also presented.