Samudra Haque

Electric propulsion for small satellites

Propulsion is required for satellite motion in outer space. The displacement of a satellite in space, orbit transfer and its attitude control are the task of space propulsion, which is carried out by rocket engines. Electric propulsion uses electric energy to energize or accelerate the propellant. The electric propulsion, which uses electrical energy to accelerate propellant in the form of plasma, is known as plasma propulsion. Plasma propulsion utilizes the electric energy to first, ionize the propellant and then, deliver energy to the resulting plasma leading to plasma acceleration. Many types of plasma thrusters have been developed over last 50 years. The variety of these devices can be divided into three main categories dependent on the mechanism of acceleration: (i) electrothermal, (ii) electrostatic and (iii) electromagnetic. Recent trends in space exploration associate with the paradigm shift towards small and efficient satellites, or micro- and nano-satellites. A particular example of microthruster considered in this paper is the micro-cathode arc thruster (µCAT). The µCAT is based on vacuum arc discharge. Thrust is produced when the arc discharge erodes some of the cathode at high velocity and is accelerated out the nozzle by a Lorentz force. The thrust amount is controlled by varying the frequency of pulses with demonstrated range to date of 1‐50Hz producing thrust ranging from 1 µN to 0.05mN.

Performance characterization of the micro-Cathode Arc Thruster and propulsion system for space applications

This paper describes a further development and characterization of vacuum arc thruster with external magnetic field. The velocity of ions moving from the micro-Cathode Arc Thrusters ( CAT) cathode spots was measured using a set of grid probes along the path of the plasma plume expansion. The goal was to get the ion drift velocity and determine how much, if any, change of ion drift velocity occurs in the expanded plasma propagation path. It was found the ion drift velocity was increased when magnetic field increased (from 0 up to 200mT). The average ion velocity (cathode material is Ti) increases by factor of 2-3 up to about (3-4) 10 m s 1 with magnetic field strength 200mT applied. Rotation of cathode spot as a result of an applied magnetic field is demonstrated by using Langmuir probes inserted inside the source channel azimuthally. Ion current distribution outside the thruster channel was measured using a set of special assemble of concentric circles plan probe alone the plasma propagation path. It is shown that plasma generated at the cathode spot is guided along the magnetic field line.

Applications of Micro-Cathode Arc Thruster as in-space propulsion subsystem for PhoneSat

The George Washington University (GWU) has developed a scalable, efficient and relatively safe electric propulsion device, for small spacecraft applications, called the Micro-Cathode Arc Thruster (μCAT). The first on-orbit demonstration of this thruster subsystem capability is planned in the second half of 2014, as the primary experiment onboard a US Naval Academy BRICSat-P mission, utilizing a 1.5U CubeSat, for validating the performance and design. From December 2012 to September 2013, NASA Ames Research center (ARC) and GWU worked together to increase the Technology Readiness Level (TRL) of the technology by integrating a complete 3-channel μCAT subsystem with the ARC PhoneSat bus. The main objectives of the collaboration were (1) to build a test bench in which a phone, running the PhoneSat firmware and a custom designed Android App could fire several thrusters in a vacuum chamber at the same time and (2) to design a CAD model of a <;3U model that could incorporate the PhoneSat bus, the thruster avionics and the thrusters themselves. At the conclusion of experimental trials, development of embedded applications, and fabrication of compact versions of legacy (2007-2012) laboratory designs, including testing in a controlled environment, the μCAT system achieved TRL 5 equivalent status. This paper presents how the interfaces of these two systems were developed, as well as the results obtained during the testing phase. The μCAT technology has several desirable properties for applications in Space, such as high specific impulse, low energy consumption, and low input voltage range. In particular, it has a compact and simple concentric design with no moving parts for extremely high reliability that yields extended operational lifetime. In this paper, analytical studies are presented to demonstrate its effectiveness for various CubeSat class spacecraft maneuvers. Analyzing the effects of low-thrust is challenging, as small variations of orbital properties should be accurately computed over a long-time period. We present brief, simplified orbital analysis based on the secular change of orbital elements derived from orbital perturbation theory. It is shown that micro-cathode thruster can be effectively used for several phases of a CubeSat mission, including orbital regularization, and inclination changes.

Broadband communication between earth and mars using linear circular commutating chain

Presents a collection of slides covering the following topics: existing deep space communication challenges; variable orbital geometry; interim investication and analysis work; LC3 heliocentric orbits; LC3 orbits (2010a); Earth SOI issues; spacecraft; 1Gbps Earth-Mars LC3; linear circular commutating chain; and LC3 space mission concept.

Small satellites with micro-propulsion for communications with the Lunar South Pole Aitkens Basin

A lunar sample return mission to the Lunar South-Pole Aitkens Basin (LSPAB) has been highlighted as a high priority objective of the most recent (2011) Decadal Survey for Planetary Science, by the National Research Council. This class of mission, however, faces a dramatic communications limitation, due to the lack of a frequent, or continuous, line-of-sight communications path to Earth-based ground stations. Brunner and others have proposed a communications system utilizing Low Lunar Polar Orbits (LLPO) and Lunar Halo orbits for this purpose. Ely and others have outlined proposals for using several communication satellites to form a relay network using LLPO, taking into account the Lunar masscons that would perturb such orbits. However, any relay network of communication satellites would still have to connect back to a suitable Earth-based ground station (Near Earth Network, or otherwise), or a tracking and data relaying satellite (e.g., TDRS).

Micro-Cathode Arc Thruster for small sattelites attitude control

Summary form only given. A low-mass, low-volume propulsion subsystems based on electrically activated micro-thrusters that utilize chemically-inert solid propellants are beneficial for small satellite attitude control applications. Micro-thrusters are able to deliver small impulse bits of about several μNs to satellites and characterized by simplicity, scalability, low cost, low weight and high reliability. In this work measurements of the key parameters of micro-Cathode Arc Thruster (μCAT) are presented and μCAT performance compared with other commercially available thruster technologies operating at the same power range.