R association
R Canis Majoris star
R Coronae Borealis star
R Leonis
R Scuti
"R" series of Russian missiles
R star
rabies
radar
radar astronomy
radar meteor
RADARSAT
radar-visual UFO
radial engine
radial pulsation
radial velocity
radial velocity method
radian
radiant
radiation
radiation belt
radiation pressure
radiation temperature
radiation-bounded nebula
radical
radical axis
radicle
radio astronomy
RADIO ASTRONOMY AND COMMUNICATIONS
radio galaxy
radio interferometer
radio source
radio telescope
radio waves
radioactive series
radioactivity
radiocarbon
radioglyph
radioisotope heater unit (RHU)
radioisotope thermoelectric generator (RTG)
radiolarian
radiometer
radionuclide
radiopanspermia
radioresistant
radiosensitive
radiosonde
radium
radius
radius (arm bone)
radius of gyration
radius vector
radon
Radose
Raduga
radula
RAE (Radiation Astronomy Explorer)
rain outage
rain shadow
rainbow
Raman, Chandrasekhar Venkata (1888–1970)
Raman effect
Raman spectroscope
Ramanujan, Srinivasa Aaiyangar (1887–1920)
ramjet
ramjet, interstellar
Ramo, Simon (1913–)
Ramsay, William (1852–1916)
Ramsden disk
Ramsey theory
random
random drift
random number
random walk
range (math.)
range finder
range safety officer
Ranger
ranging
Rankine scale
ranunculoid
Raoult, François Marie (1830–1901)
Raoult's law
rapid irregular variable
rare earth elements
Rasalhague (Alpha Ophiuchi)
Ra-Shalom (minor planet 2100)
ratchet
ratio
rational number
rationalism
ratite
Rauschenbach, Boris Viktovich (1915–2001)
raven paradox
ray
ray crater
Rayleigh, John William Strutt, Third Baron (1842–1919)
Rayleigh criterion
Rayleigh scattering
Rayleigh-Taylor instability
Raynaud's disease
R-class asteroid
reactance
reactant
reaction control system (RCS)
reaction engine
reaction mass
reaction nozzle
Reaction Research Society (RRS)
reaction wheel
reactionless drive
real analysis
real number
realgar
realism
realm
Reber, Grote (1911–2002)
receptor-mediated endocytosis
recessive
reciprocal
recombinant DNA
recombination
reconnaissance satellite
Recorde, Robert (c.1510–1558)
recovery (of a comet)
recovery (of a spacecraft)
rectangle
rectangular coordinates
rectifier
rectum
recursion
recursive function
recursively enumerable set
red algae
red Centaurs
red dwarf
red giant
red giant tip
red rain of Kerala
Red Rectangle
red shift
Red Spider Nebula (NGC 6537)
Red Square
red supergiant
Redi, Francesco (1626–1697)
redox potential
redox reaction
redox sensor
Redstone
reducing atmosphere
reductio ad absurdum
reduction
reductionism
redundancy
reentrant angle
reentry
Reentry (test program)
reentry corridor
Reentry Flight Demonstrator (RFD)
REENTRY PHYSICS AND TERMINOLOGY
reentry thermal protection
reentry vehicle
reentry window
Rees, Eberhard F. M. (1909–1998)
reflecting binary
reflecting telescope
reflection
reflection nebula
reflector
reflex
reflex angle
reflex arc
reflexible
refracting telescope
refraction
refractive index
refractor
refractory
refugium
regenerated disk
regeneration
regenerative cooling
regimes of flight
regmaglypt
regolith
regression of nodes
regressive burning
regular expression
regular polyhedron
Regulus
relative atomic mass
relative molecular mass
relative permeability
relative sunspot number
relatively prime
relativistic
relativistic beaming
relativistic effects
relativistic quantum field theory
relativity theory
relaxation
Relay
relief
remaining mass
Remek, Vladimir (1948–)
Remote Manipulator System (RMS)
remote sensing
remote sensing satellite
renal
rendezvous
Rendezvous with Rama
renin
renormalization
repdigit
repeater
replicator
representation theory
repressor
reproductive system
rep-tile
reptile
rep-unit
RESEARCH FACILITIES AND ESTABLISHMENTS
resin
resistance, electrical
resistivity
resistojet
resistor
Resnick, Judith A. (1949–1996)
resolution
resolution bandwidth
resolving power
resonance
resonance (orbital)
resorcinol
respiration
respiratory distress syndrome
respiratory system
rest mass
resting potential
restless legs syndrome
restriction enzyme
resultant
resurfacing
Resurs
reticular formation
reticulite
reticulo-endothelial system
Reticulum (constellation)
retina
retinal
retort
retrograde (motion)
retrorocket
retrovirus
Reuleaux polytope
Reuleaux Triangle
reusable launch vehicle (RLV)
Reutersvärd, Oscar (1915-2002)
revolution
REX (Radiation Experiment)
Reynaud, Jean (1806–1863)
Reynolds, James Emerson (1844–1920)
Reynolds number
Rh incompatibility
Rhea
rhenium
rhesus factor
RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager)
Rheticus (1514–1574)
rheumatic fever
rheumatoid arthritis
Rhind papyrus
rhinitis
rhizome
Rho¹ Cancri (55 Cancri)
Rho Cassiopeiae
Rho Coronae Borealis
Rho Ophiuchi Nebula
rhodium
rhodopsin
rhombus
rhyolite
Rhyolite/Aquacade
rib
rib-cage
ribonucleic acid
ribose
ribosomal DNA
ribosomal RNA
ribosome
ribozymes
Riccioli, Giovanni Battista (1598–1671)
rich cluster of galaxies
richest field telescope (RFT)
Richter, H. E.
Ride, Sally Kristen (1951–)
Riedel, Klaus (1901–1944)
Riemann, (Georg Friedrich) Bernhard (1826–1866)
Riemann hypothesis
Riemann integral
Riemann sphere
Riemann surface
Riemann zeta function
Riemannian geometry
rift valley
rift zone
Rigel (Beta Orionis)
Rigel Kentaurus
right
right ascension
rigidity
rille
ring (mathematical)
ring, planetary
ring galaxy
Ring Nebula (M57, NGC 6720)
ringworld
Ringworld
ringworm
Ritchey-Chrétien telescope
Rithmomachia
Ritter, Johann Wilhelm (1776–1810)
river-crossing problems
RME (Relay Mirror Experiment)
RNA (ribonucleic acid)
"RNA world"
Robby the Robot
Robert's Quartet
Robinson, Abraham (1918–1974)
robot
Roche limit
Roche lobe
Rochon prism
rock
rocket
ROCKET ENGINE TYPES
ROCKET ENGINEERS AND SPACE SCIENTISTS
rocket equation
rocket plane
rocket principle
rocket propulsion
Rocket Racing League
rocket sled
Rockplane Kistler
ROCKETRY, HISTORY
ROCKETRY, TERMINOLOGY
ROCKETS, MISSILES, AND LAUNCH VEHICLES
rockoon
Rockot
Rockwell
rod cell
Roddenberry, (Eu)Gene Wesley (1921–1991)
rogue planet
rogue star
Rohini
Rolle's theorem
Rolls-Royce Thrust-measuring Rig ("flying bedstead")
Roman numerals
Romb
Ronchi test
rooks problem
Roosa, Stuart A. (1933–1994)
root (mathematical)
root (plant)
root of unity
rope-around-the-Earth puzzle
Roque de los Muchachos Observatory (ORM)
RORSAT (Radar Ocean Reconnaissance Satellite)
Rosalind
Rosamund's Bower
ROSAT (Roentgen Satellite)
rose curve
Rosen, Milton W. (1915–)
Rosetta
Rosette Nebula (NGC 2237-2239, 2246)
Rosny, J. H. (the Elder) (1856–1940)
Ross, Frank Elmore (1874–1960)
Ross, H(arry) E.
Ross 128
Ross 154
Ross 248
Rosse, Third Earl of (William Parsons) (1800–1867)
Roswell Incident
Roswell Incident, GAO report
Roswell Incident, USAF rport
rotating variable
rotation
rotation curve
rotation period
rotator cuff
Rothrock, Addison M. (1903–1971)
Roton
rotor
roulette
round
round window
rounding
round-off error
round-trip light time (RLT)
roundworm
Rover, Project
Royal Astronomical Society
Royal Greenwich Observatory
RP-1 (rocket propellant 1)
RP-318
r-process
RR Lyrae star
rRNA
RS Canum Venaticorum star
RS Ophiuchi
RTG
rubber
rubble-pile asteroid
rubella
rubidium
Rubik's Cube
Rucker, Rudy (Rudolf von Bitter) (1946–)
Rudolph, Arthur L. (1906–1996)
ruled surface
rumble
Rumford, Benjamin Thompson, Count (1753–1814)
runaway greenhouse effect
runaway star
Ruppelt, Captain Edward J. (1922–1960)
R.U.R. (Rossum's Universal Robots)
Russell, Bertrand Arthur William (1872–1970)
Russell, Henry Norris (1877–1957)
Russell's paradox
Russian launch sites
Russian launch vehicles
Russian manned lunar programs
Russian multiplication
Russian Space Agency (RKA)
Russian Space Research Institute (IKI)
Rutan, Elbert L. "Burt" (1943–)
ruthenium
Rutherford, Ernest (1871–1937)
Rutherford's experiment and atomic model
RV Tauri star
RXTE (Rossi X-ray Timing Explorer)
Ryle, Martin (1918–1984)
Rynin, Nikolai Alexsevitch (1887–1942)
Ryusei