FAS | Nuclear Resources | Space |||| Index | Search |

AB Aerobrake

AFAL Air Force Astronautics Laboratory

ANP Aircraft Nuclear Propulsion

ANRE Advanced Nuclear Rocket Engine

ASE Airborne Support Equipment

atm Atmosphere

BeO Beryllium Oxide

BISO a fuel particle with two carbon coatings made by GA Technologies

C&DH Communications & Data Handling

CPF Cost Per Flight

CTE Coefficient of Thermal Expansion

DDT&E Design, Development, Test & Evaluation

DoD Department of Defense

DOE Department of Energy

ECCV Earth Capture Crew Vehicle

EIS Environmental Impact Statement

ETR Eastern Test Range

EVA Extra-Vehicular Activity

FBR Fixed Bed Reactor

FY Fiscal Year

GEO Geosynchronous Orbit

GN&C Guidance, Navigation & Control

GSE Ground Support Equipment

H2 Molecular Hydrogen

HEI Human Exploration Initiative

HfC Hafnium Carbide

HLLV Heavy Lift Launch Vehicle

HTGR High Temperature Gas Reactor

ILC Initial Launch Capability

IMEO Initial Mass in Earth Orbit

IMLEO Initial Mass in Low Earth Orbit

INEL Idaho National Engineering Laboratory

INSRP Interagency Nuclear Safety Review Panel

IOC Initial Operating Capability

Isp Specific Impulse

IVA Intra-Vehicular Activity

JPL Jet Propulsion Laboratory

JSC Johnson Space Center

kPa kilo Pascal

kWe kilo Watt electric (equivalent to the average electrical power consumption of a single household)

kWt kilo Watt thermal

LANL Los Alamos National Laboratory

LARS Liquid Annular Rocket System

LCC Life Cycle Cost

LEO Low Earth Orbit

LeRC Lewis Research Center

LH2 Liquid Hydrogen

LLNL Lawrence Livermore National Laboratory

LOX Liquid Oxygen

LEV Lunar Excursion Vehicle

LTV Lunar Transfer Vehicle

MDAV Mars Descent/Ascent Vehicle

MEV Mars Excursion Vehicle

MLI Multi Layer Insulation

MMW Multimegatwatt

MMWSS Multimegatwatt Steady State

MPD Magneto Plasma Dynamic

MSFC Marshall Space Flight Center

MPa Mega Pascal

MTV Mars Transfer Vehicle

MWe Mega Watt electric

MWt Mega Watt thermal

NASA National Aeronautics and Space Administration

NDR NERVA Derivative Reactor

NEP Nuclear Electric Propulsion

NEPA National Environmental Protection Act

NEPA Nuclear Energy Propulsion for Aircraft

NERVA Nuclear Engine for Rocket Vehicle Applications

NRC Nuclear Regulatory Commission

NTP Nuclear Thermal Propulsion

NTR Nuclear Thermal Rocket

NTS Nevada Test Site

ORNL Oak Ridge National Laboratory

OTV Orbital Transfer Vehicle

RBR Rotating Bed Reactor

RCS Reaction Control System

SAIC Science Applications International Corp.

SDI Strategic Defense Initiative

SEI Space Exploration Initiative

SNAP Systems for Nuclear Auxiliary Power

SSME Space Shuttle Main Engine

SSF Space Station Freedom

T/W Thrust to Weight ratio

TaC Tantalum Carbide

TRISO a fuel particle with four coatings made by GA Technologies

TRL Technology Readiness Level

TRW Thompson Ramo Woolridge

UC₂ Uranium Carbide

ZrC Zirconium Carbide

Aerobrake: An "air brake" used to slow a spaceship with the upper layers of a planet`s atmosphere to conserve the spaceship's propellants.

Aerocapture: A technique of capturing heliocentric spacecraft into a planetary orbit, using an aerobrake.

Aphelion: Point in solar orbit (planet or spacecraft) furthest from the center of the Sun.

Apogee: Point in an orbit around the Earth furthest from the center of the Earth.

Brayton Engine: Engine utilizing the Brayton cycle, a thermodynamic cycle consisting of two pressure processes interspersed with two constant-entropy processes. Using a single phase gaseous working fluid, this cycle in exemplified by a gas turbine engine.

C3: Injection energy; square of the hyperbolic excess velocity in units of (km/s)³.

Cislunar: Of or in the region of space between the Earth and Moon.

Conjunction-Class Trajectory: Round trip trajectory between two planets (e.g. Earth and Mars) requiring minimum fuel expenditure. Conjunction-Class Mars mission generally have flight times slightly greater than 1000 days.

Cryogenic Propellant: Propellant that must be stored at very low temperatures, e.g. liquid hydrogen and liquid oxygen.

Enabling Technology: Key high-leverage technology required for completion of a spacecraft mission.

Enhancing Technology: Technology that could provide additional mission performance or capability, though not required for completion of a spacecraft mission.

Geostationary Earth Orbit: A circular orbit approximately 35,800 km above the Earth's surface in the plane of the equator. An object in such an orbit rotates at the same rate as the planet and therefore appears to be stationary with regard to any point on the Earth's surface. It is a specific type of geosynchronous orbit.

Hypergolic Propellant: A combination of fuel and oxidizer that ignite spontaneously on contact.

Low-Earth Orbit: A circular orbit about Earth with an altitude of approximately 300 to 500 km.

Low-Lunar Orbit: A circular orbit about the Moon with and altitude of approximately 100 km.

Low-Mars Orbit: A circular orbit about Mars with and altitude of approximately 250 to 500 km.

Lunar Excursion Vehicle: Vehicle designed to transport crew, cargo, and propellants between low-lunar orbits and the lunar surface by the year 2000.

Lunar Transfer Vehicle: Vehicle for transportation between low-Earth orbit and the Moon.

Mars Ascent Vehicle: The vehicle is launched from Mars surface to Mars Orbit.

Mars Cargo Vehicle: Logistics sent to Mars for cargo staging.

Mars Decent Vehicle: The vehicle that de-orbits to land on Mars.

Mars Excursion Vehicle: Spacecraft that carries crew to Mars surface to Mars orbit.

Mars Transfer Vehicle: Space craft configuration during flight to Mars.

Nuclear Electric Propulsion: Low-thrust electric propulsion, with electric power provided by a nuclear reactor.

Nuclear Engine for Rocket Vehicle Application: (NERVA), Nuclear thermal rocket program.

Nuclear Safe Orbit: Circular geocentric orbit with 700 km altitude designed to delay atmospheric entry and space craft nuclear reactor disintegration for several hundred years in order to reduce the danger of high-level radiation in the atmosphere.

Nuclear Thermal Rocket: A space propulsion concept technique in which the heat from a nuclear fission reactor is used to raise the temperature of the propellant, which is then expanded through a nozzle to provide thrust. Two types of thermal rockets have been studied; gas core and solid core.

Opposition-Class Trajectory: Round-trip trajectory between to planets (e.g., Earth and Mars) requiring a higher level of fuel expenditure than conjunction class missions. Opposition-class Mars missions generally have flight times around 500 days.

Orbital Maneuvering Vehicle: A device used much like a "harbor tug" in ship operations, with remotely controlled manipulator arms to handle spacecraft and refueling operations with great care.

Perigee: Point in an orbit around the Earth closest to the center of the Earth.

Perihelion: Point in solar orbit (planet or spacecraft) closest to the center of the sun.

Radioisotope Thermoelectric Generator: Self-contained power system in which a radioisotope is used to heat one junction in a circuit containing dissimilar metals, thus generating sustained electricity.

Rankine Engine: Engine utilizing the Rankine cycle, a thermodynamic cycle using a two-phase working fluid, which in the closed cycle variant is condensed in a radiator for reuse. This cycle in exemplified by the steam turbines used to generate electricity at a coal-fired power plant.

Solar Electric Propulsion: Ion drive; solar power; utilized in rocket systems; based on electric power, which can be derived from soar cells.

Specific Impulse: A measurement of engine performance. It is the ratio of the pounds of thrust produced by the engine, minus the drag from the engine, per pounds of fuel flowing through the engine each second.

One of the enduring problems for the space community is properly appreciating both the absolute and relative size of space vehicles. This difficult derives from physical as well as stylistic considerations.

Probably no other discipline deals with objects with such a wide range of physical dimensions. The dimensions of all automobiles are denominated in meters, those of essentially all aircraft in tens of meters, while the dimensions of most naval vessels range between one and three hundred meters. But space vehicles range from small automated spacecraft a few meters across through launch vehicles over a hundred meters across to designs for large space structures that may be several kilometers across.

The portrayal of the vast range of the physical dimensions of space vehicles is constrained by the physical dimensions of a piece of paper. As a result, all space vehicles, regardless of their true size, normally are depicted as being about the size of a finger, or at most the size of a hand.

In order to minimize such perceptual distortions, this study has adopted several standard scales at which all systems are portrayed. The smallest scale (Figure 1) is used for

reactors.

Two scales are used in most cases. One, which is five times larger than that used for reactor systems, is employed to depict missiles and uppper stages (Figure 2), while the other, which is four times larger, (Figure 3) depicts launch vehicles. The fourth (Figure 4) is used to portray Lunar and Mars transfer vehicles.

The fact that the base of the Eiffel Tower barely fits into Figure 2, while our familiar delivery truck is barely visible in Figure 4, is evidence of the vast range of scales of space vehicles.

The metric, or International System of Units (SI) is used throughout this study.

Prefixes are added to SI units to indicate decade multiples:

Factor Prefix Symbol

10¹⁸ exa E

10¹⁵ peta P

10¹² tera T

10⁹ giga G

10⁶ mega M

10³ kilo k

10² hecto h

10 deka da

10^-1 deci d

10^-2 centi c

10^-3 milli m

10^-6 micro u

10^-9 nano n

10^-12 pico p

10^-15 femto f

10^-18 atto a

To convert to From Multiply by

ACCELERATION

Meter/second²

Gal (Galileo) 1 x 10^-2

Foot/second² 3.048 x 10^-1

To convert to From Multiply by

AREA

Meter²

Acre 4.046 x 10³

Foot² 9.29 x 10^-2

Hectare 1 x 10⁴

Mile² (Nautical) 3.429 x 10⁶

Mile² (Statute) 2.589 x 10⁶

Yard² 8.361 x 10^-1

ENERGY

Joule ( = newton x meter )

British Thermal Unit 1.055 x 10³

Calorie 4.19

Erg 1 x 10^-7

Kilowatt Hour 3.6 x 10⁶

Ton of TNT equivalent 4.184 x 10⁹

FORCE

Newton ( = kilogram x meter/second² )

Dyne 1 x 10^-5

Pound (thrust) 4.448

Horsepower 3.693 x 10¹

LENGTH

Meter

Angstrom 1 x 10^-10

Astronomical Unit 1.495 x 10¹¹

Earth Equatorial Radius 6.378 x 10⁶

Foot 3.048 x 10^-1

Mile (Nautical) 1.852 x 10³

Mile (Statute) 1.609 x 10³

Yard 9.144 x 10^-1

To convert to From Multiply by

MASS

Kilogram

Atomic Unit (electron) 9.109 x 10^-31

Atomic Mass Unit 1.66 x 10^-27

Pound 4.535 x 10^-1

Ton (metric) 1 x 10³

Ton (short) 9.071 x 10²

POWER

Watt ( = Joule / second )

Foot-pound/second 1.355

Horsepower (550 ftlb/sec) 7.46 x 10²

Solar Luminosity 3.826 x 10²⁶

PRESSURE

Pascal ( = newton / meter² )

Atmosphere 1.013 x 10⁵

Bar 1 x 10⁵

pound/inch² (psi) 6.894 x 10³

Torr 1.333 x 10²

TEMPERATURE

Kelvin

Celsius ^oC t_K = t_C + 273.15

Fahrenheit ^oF t_K = ( t_f + 459.67 ) x (5/9)

Fahrenheit ^oF t_C = ( t_f + 32 ) x (5/9)

To convert to From Multiply by

VELOCITY

meter / second

foot / minute 5.08 x 10^-3

foot / second 3.048 x 10^-1

kilometer / hour 2.777.. x 10^-1

knots 5.144 x 10^-1

miles / hour 4.47 x 10^-1

miles / second 1.609 x 10³

velocity of light 2.997 x 10⁸

VOLUME

meter³

Foot³ 2.831 x 10^-2

Inch³ 1.638 x 10^-5

Liter 1 x 10^-3

Yard³ 7.645 x 10^-1