AE 323- Quiz 3

Primary Batteries

non-recharable, single-use

Secondary Batteries

Rechargeable, multiple-use

Fuel Cells

Chemical-to electrical energy

• for manned, short-term missions

• hydrogen/oxygen fuel to electricity

• water as byproduct (1 pint/kW*hr

• output=0.8 volts/cell

• specfic power = 275 W/kg (high)

• ex. space shuttle fuel cells produce up to 16kW peak power

Regenerative Fuel Cells

Reversible energy storage

Chemical Dynamic

Thermal-to-electric conversion

Nuclear

Fission-based power

• requires refueling, shielding

• need to manage excess heat

Electrodynamics Tethers

Magnetic field electricity

Radioisotope Thermal Generators (RTG)

Decay heat electricity

• for long-duration deep space

• Seebeck effect electricity

• low power, long life

• super reliable 9used on perseverance, curiosity, apollo, viking, etc)

Thermionic Converters

Heat-to-electricity direct

Thermoelectric Converters

Temperature difference power

Photovoltaic

Solar light electricity

• common in unmanned spacecraft

• metric: power, efficiency

• N/P-material interaction

Solar Dynamic

Sun-heat mechanical power

Flywheel Storage

Kinetic energy reserve

Propulsion-Charged Tether

Orbit-change via electromotive force

Batteries

• early (primary)

• now mainly (secondary)

• metrics: energy, charge cycles

• Oxidation/Reduction operation

Fuel Cell Mechanics

Hydrogen gas enter anode/cathode system

Hydrogen gas losses two electrons (2H+) that travel up the anode to a load(where the electricity is converted)

2H+ travels through an electrolyte towards the Cathode where oxygen gas is being released, the electrons are returned and H2O leaves the system

2H2 + O2 = 2H2O + energy

Why use fuel cells?

• high energy density of H and O (more energy in a smaller space)

• only byproduct is H2O which is harmless and can be used for drinking, cooling, or additional oxygen supply

• consistent power output (independent of environmental factors like the sun)

RTG Mechanics

• starts with Plutonium-238 which decays into Uranium-234 after loosing alpha particles

• this releases energy E=mc²

• exothermic process, high temp difference between decaying material and environment

Seebeck Effect

• two materials, one facing hot and the other facing cold, that have contact with each other

• electrons move from the hot side to the cold side (producing electricity)

• uses conductors or semi-conductors

Thermocouple

device that converts thermal energy into electrical

• two dissimilar conductors that have the Seebeck effect applied to them

• the greater the difference between the hot and cold, the more power generated

RTG Advantages

• power independence from sunlight

• extended operational longevity

• high power efficiency relative to size

• structural reliability and safety

• maintenance-free operation

RTG Disadvantages

• inherent continuous decay and decreasing power output

• need for cooling and shielding

• low conversion efficiency

• high cost of radioisotope materials

Space Situation Awareness

practice of identifying objects in space, either globally, or in same locally defined area, and determining the nature of these objects based on certain established criteria (earth-orbiting or deep space)

SSA Objectives

Object characterization

• photometric: characterizing objects based on how they look

• astrometric: characterizing objects based on how they move

Motion prediction

• Collision avoidance

• Sensor tip-and-cue

LEO

• polar

• sun-synchronous

MEO

GPS

GTO

rocket bodies

SSA History

• Sputnik 1 (1957) is the first

• increase from

  • 17 Jan 2007: Chinese anti-satellite test

  • 17 Feb 2009: Iridium 33 collides with COSMOS 2251

  • 15 Nov 2021: cosmos 1408 satellite was destroyed in a Russian anti-satellite weapon test

Number of rocket launches since the since the start of the space age in 1957 (excluding failures)

6710

Number of satellites these rocket launches have placed into Earth orbit

19160

Number of satellites these rocket launches have placed into Earth orbit still in space

13030

Number of satellites these rocket launches have placed into Earth orbit still functioning

10200

Number of space objects regularly tracked by Space Surveillance Networks and maintained in their catalogue

36440

Estimated number of break-ups, explosions, collisions, or anomalous events resulting in fragmentation

>650

Total mass of all space objects in Earth orbit

>12900 tonnes

Estimations on non-tracked objects

• 40500 space debris object greater than 10 cm

• 1100000 space debris objects from greater than 1 cm to 10 cm

• 130 million space debris objects from greater than 1 mm to 1 cm

Space Catalog

listings of objects and their orbits

• single list is an instantaneous snapshot of the SSA picture

• DoD (USSF) is widely, but not universally accepted version

• Two main challenges:

  • Sensor tasking: directing each sensor where to “look” and take data

  • Data association (or observation assignment): telescope images often capture multiple objects in a frame; correct orbit determination of objects requires them to be properly distinguished

TLEs/3LEs

• two-line element of the JSpOC space catalog (TLE)

• contains info describing an object’s orbit, with some metadata

• an extra line is often included indicating the name of the object (3LE)

• widely accepted

Active Object Tracking

2-way communication between active satellite and its owner

• Telemetry, tracking, and command (TT&C)

• Air Force Satellite Control network (AFSCN)

Passive Object Tracking

1-way sensing of object through electromagnetic means

• primary sensing modes are RF (radars) and optical (telescopes)

• most sensors are terrestrial

• Space Surveillance Network (SSN) is in space

Global vs Local SSA

Used to be only global, recent trend towards local

• fewer sensors, decentralization, less coordination

• fewer objects, less data/throughput/processing, compact

• amenable to space-based observes, onboard/autonomous awareness of object’s in the observer’s vicinity

Local SSA with Optical Data

• uses unit vector from the observer to the RSO (object of focus), and two angles (right ascension and declination)

• can use inertial stare (streak) or orbit-following mode (dot)

5 steps to RSO ID

1. Edge detection on each frame

   • boundary between each set of illuminated pixels and blackness of space 9reduces each image to numerous segmented objects)

   • dependent on pixel intensity (too low—-noise too high——-not all objects will be detected)

2. Centroiding on each frame

   • localizes each illuminated object (x,y coordinates)

3. Image registration (i.e. plate solving) on each frame

   • uses star pattern matching to determine inertial pointing of the camera (RA, DEC coordinates)

4. Star elimination

   • removes all centroids identified as belonging to a star

5. Object association

   • performs linear regression on sets of centroids across the collect 9confirms the existence of the RSO tracklet)

Gives us a local mini-catalog of object in the satellite’s vicinity, autonomously track and monitor nearby objects