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SPT-100
The SPT-100 (Russian СПД-100, Stationary Plasma Thruster) is a 1.35 kW Hall-effect thruster built by Fakel in Kaliningrad, Russia, flown for spacecraft station-keeping since 1994.
Sputnik 1 (Спутник-1)
Sputnik 1 (Спутник-1) was the world's first artificial Earth satellite, a 58 cm aluminum sphere the Soviet Union launched on 4 October 1957, opening the Space Age.
Sputnik 2 (Спутник-2)
Sputnik 2, also known as Sputnik II, was the second Soviet artificial satellite, launched on November 3, 1957, carrying the dog Laika, the first animal to orbit Earth.
Sputnik crisis
The Sputnik crisis, also known as the Sputnik shock or Sputnik moment, was American public alarm after the Soviet Union launched Sputnik 1, the first artificial satellite, in 1957.
SSL 1300
SSL 1300, formerly the LS-1300 and FS-1300, is a modular satellite bus for large communications and imaging spacecraft, first flown in 1989 by Ford Aerospace in Palo Alto, California.
SSVP
SSVP, or Sistema Stykovki i Vnutrennego Perekhoda, is the Soviet and Russian probe-and-drogue docking system that has connected Soyuz and Progress spacecraft to space stations since 1971.
Stability of the Lagrange points
The stability of the Lagrange points: triangular points L4 and L5 are stable below Routh's mass-ratio threshold, while collinear L1, L2, and L3 are always unstable.
Stage separation
Stage separation is the flight event in which a spent rocket stage is detached from the launch vehicle so the continuing stage can carry on to orbit.
Staged combustion cycle
The staged combustion cycle is a closed liquid rocket engine cycle in which preburner gas drives the turbopumps and is then burned again in the main chamber.
Stanford torus
The Stanford torus is a wheel-shaped space habitat design from a 1975 NASA study: a rotating ring about 1.8 km across providing Earth-normal gravity for 10,000 residents.
Star Tours
Star Tours is a Star Wars-themed motion simulator ride at Disney parks, created with George Lucas and opened at Disneyland in 1987, reimagined in 2011 as Star Tours: The Adventures Continue.
Star tracker
A star tracker is an optical instrument on a spacecraft that measures its orientation by imaging stars and matching them against an onboard star catalog.
Starbase
Starbase is a city in Cameron County, Texas, at the southern tip of the state near the Mexico border, incorporated in May 2025 around SpaceX's Boca Chica launch site.
Stargazer (aircraft)
Stargazer is a modified Lockheed L-1011 TriStar airliner, built in 1974 for Air Canada and converted in the 1990s, used to air-launch Pegasus rockets on 46 missions through 2026.
Starlab (space station)
Starlab is a planned commercial space station developed by Starlab Space, a joint venture led by Voyager Technologies with Airbus, scheduled to launch in 2029.
Starlink
Starlink, also known as SpaceX Starlink, is a satellite internet constellation operated by SpaceX that delivers broadband from thousands of satellites in low Earth orbit, announced in 2015.
Starship flight test 12
Starship flight test 12, also known as Flight 12 or IFT-12, was SpaceX's twelfth Starship test flight and the first of the Version 3 vehicle, launched in 2026 from Starbase, Texas.
Starship flight test 13
Starship flight test 13, SpaceX's thirteenth Starship launch on July 24, 2026, deployed the first Starlink V3 satellites and achieved the first intact upper-stage splashdown.
Starship flight test 14
Starship flight test 14 was the fourteenth test flight of SpaceX's Starship and its first to reach Earth orbit, launching from Starbase, Texas, in September 2026.
Starship HLS
Starship HLS, also known as the Lunar Starship, is a crewed lunar lander SpaceX is developing for NASA to carry two astronauts to the Moon's surface on Artemis missions.
Starship Propellant Transfer Demonstration
NASA Tipping Point-funded SpaceX demonstration moving cryogenic liquid oxygen between tanks on Starship in orbit, first flown March 14, 2024, transferring about 5 metric tons toward future ship-to-ship refueling.
Start-1
Start-1 (Старт-1) was a Russian four-stage, all-solid-propellant launch vehicle converted from the SS-25 Topol ICBM, which placed small satellites into low Earth orbit from 1993 to 2006.
State space representation (GNSS augmentation)
State space representation (SSR) is a GNSS augmentation method that broadcasts individual error states, such as satellite orbit, clock, and atmospheric delays, separately for receivers to apply, underlying PPP and PPP-RTK.
Station-keeping
Station-keeping is the maintenance of a satellite's assigned orbital position against natural perturbations: geostationary satellites burn propellant to stay within a control box of about ±0.1° in longitude and inclination.
Stennis Space Center
Stennis Space Center is NASA's primary rocket propulsion testing facility in Hancock County, Mississippi, which tested Saturn V and shuttle engines and now tests SLS for Artemis.
Steven D. Dorfman
Steven D. Dorfman is an engineer who spent 42 years at Hughes, rising from manager of NASA's Pioneer Venus program to vice chairman of Hughes Electronics.
Steven J. Battel
Steven J. Battel is an American aerospace engineer specializing in spacecraft high voltage and power electronics, elected to the National Academy of Engineering in 2016.
Stirling radioisotope generator
A Stirling radioisotope generator is a spacecraft power system that converts plutonium-238 decay heat into electricity using a Stirling-cycle engine, about four times more efficient than thermoelectric systems.
Stoke Space
Stoke Space is an American aerospace company founded in 2019 in Kent, Washington by former Blue Origin engineers Andy Lapsa and Tom Feldman, developing the fully reusable Nova rocket.
Strap-on booster
A strap-on booster is a rocket motor attached to the side of a launch vehicle's core stage, burning in parallel to increase liftoff thrust and payload capacity.