Responsiveness in Low Orbits using Electric Propulsion

Abstract

One promising option for space operational responsiveness is orbital maneuvering. In low orbit, a maneuverable spacecraft can provide valuable benefits such as better coverage properties, increased revisit times, selectable targets, and local over-flight times. Such maneuvers are not common due to the high cost of chemical propulsion. The more recent paradigm of Responsive Space is to rapidly launch a small, inexpensive asset and use it in a short, disposable fashion. This concept relies on drastically reducing the cost of launch, yet it remains the most expensive piece, so additional cost savings can be realized by minimizing the need for launches. Electric propulsion has been considered as an efficient alternative to chemical propulsion. With technological advances, electric propulsion can provide responsiveness in a timely, fuel-efficient manner without requiring repeated launches to satisfy multiple missions. This study shows the control algorithm for a single low-Earth satellite equipped with the proper electric propulsion to overfly any target inside its coverage area in as little as 34 hours for 1.8 percent of its propellant budget. A comprehensive survey to quantify global reach requirements is provided and the optimal time and fuel solutions are explored. The results strongly support that electric propulsion could be a key enabler in responsive operations. Nomenclature A = perturbing acceleration magnitude, km/s 2 a = semi-major axis, km a h = normal acceleration component with respect to orbital plane, km/s 2 a r = radial acceleration component in local-vertical, local-horizontal frame, km/s 2 a θ = acceleration component completing the right-handed coordinate system, km/s 2 e = eccentricity h = angular momentum ĥ = normal component wrt orbital plane of the local-vertical, local-horizontal frame i = inclination, degrees M = mean anomaly, rad m 0 = initial spacecraft mass, kg m  = mass flow rate, kg/s Δm = change in mass due to maneuvering, kg n = mean motion, rad/s p = semi-latus rectum, km r = radius vector, components in km r = magnitude of radius vector, km rˆ = radial component of the local-vertical, local-horizontal frame T = thrust magnitude, N t = time, s t 0 = initial time, s t f = final time, s Δt = change in over-flight time, s u = argument of latitude, degrees V = velocity vector, components in km/s ΔV = velocity change, km/s x = state vector in terms of Classical Orbital Elements x 0 = initial state vector in Classical Orbital Elements γ = angle between Earth-Centered Inertial (ECI) and ECF frames, rad γ g = Greenwich sidereal time, rad θ = out-of-plane thrust angle wrt rˆ-ˆ plane, degrees ˆ = tangential component of the local-vertical, local-horizontal frame λ = latitude, degrees Downloaded by UNIVERSITY OF NEW SOUTH WALES on August 23, 2015 | http://arc.aiaa.org |   = Earth's gravitational parameter, 3.98601 x10 5 km 3 /s 2 ν = true anomaly, rad φ = longitude, degrees ψ = thrust control vector, components in degrees ψ = thrust angle in rˆ-ˆ plane, degrees Ω = right ascension of the a...

Analytical Low-Thrust Satellite Maneuvers for Rapid Ground Target Revisit

“…The acceleration of the electric propulsion system given here is consistent with that used by Co in his previous work. [18][19][20] Table 1 defines the standard orbital parameters used for the analysis.…”

“…For the case of low-thrust propulsion, Co's work in recent years has developed a control algorithm which allows a single satellite to pass over a given target using electric propulsion. [18][19][20] Co uses the difference in time of flyover between the maneuvering satellite and a non-maneuvering reference satellite as a metric, and can solve for this using a single equation. Co's algorithm propagates the initial orbit for a given time and identifies close passes to the target.…”

Constellation design for responsive visiting based on ground track adjustment

“…3 Many studies have focused on fulfilling missions by maneuvering existing low-Earth-orbit (LEO) satellites. [4][5][6][7][8][9][10][11][12][13][14] Slight corrective maneuvers can be employed to alter a ground track pattern into another to satisfy several objectives in the course of the same mission. 4 The effects of an in-plane maneuver on any point of the ground track for near-circular orbits were analyzed, which could be required by responsive surveillance missions, in Zhang et al 5 A low-thrust orbit maneuver was used as an effective means to achieve responsive terrestrial coverage.…”

“…4 The effects of an in-plane maneuver on any point of the ground track for near-circular orbits were analyzed, which could be required by responsive surveillance missions, in Zhang et al 5 A low-thrust orbit maneuver was used as an effective means to achieve responsive terrestrial coverage. [6][7][8][9][10][11] The Lorentz force, a type of propellantless force, was adopted to drive an on-orbit satellite to gradually change its orbit and provide new coverage in Pollock et al 6 In particular, electric propulsion (EP) was used as a means of maneuvering in. [7][8][9][10][11] Adjusting the ground tracks of LEO satellites to arrive over a terrestrial target has been studied extensively in recent years.…”

“…[6][7][8][9][10][11] The Lorentz force, a type of propellantless force, was adopted to drive an on-orbit satellite to gradually change its orbit and provide new coverage in Pollock et al 6 In particular, electric propulsion (EP) was used as a means of maneuvering in. [7][8][9][10][11] Adjusting the ground tracks of LEO satellites to arrive over a terrestrial target has been studied extensively in recent years. [7][8][9][10][11][12][13][14] concluded that continuous thrusting with an EP engine over a period of 7 days will yield a 24 h time-over-target change, which equals global reach.…”