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Project Mercury
Project Mercury, also known as the Mercury program, was the United States' first human spaceflight program, whose six crewed flights from 1961 to 1963 put Americans in space and Earth orbit.
Project Orion (nuclear propulsion)
Project Orion was a United States study from 1958 to 1965 of spacecraft propelled by nuclear explosions detonated behind a pusher plate, canceled by the 1963 nuclear test ban treaty.
Project West Ford
Project West Ford, also known as Project Needles, was a 1961 and 1963 US military experiment that orbited millions of copper needles to reflect radio signals.
Propellant
A propellant is a substance or combination of substances that a rocket expends to produce thrust, including solid, liquid, and hybrid types, monopropellants, and expelled gases.
Propulsive landing
A propulsive landing is one in which a spacecraft or rocket stage fires its own rocket engines against the direction of travel to slow down and touch down.
Protected Tactical SATCOM (PTES)
Protected Tactical SATCOM (PTES), or Protected Tactical Enterprise Service, is a United States Space Force ground system giving tactical warfighters jam-resistant satellite communications in contested environments.
Proton-K
The Proton-K (Протон-К, GRAU 8K82K) was a Soviet, later Russian, heavy-lift carrier rocket built by Khrunichev, flown from 1967 into the 2000s and now retired.
Proton-M (Протон-М)
Proton-M, also known as Протон-М, is an expendable Russian heavy-lift launch vehicle, first flown in 2001 from Baikonur and built by the Khrunichev Space Center.
Proxima (film)
Proxima is a 2019 French-German drama directed by Alice Winocour, starring Eva Green as astronaut Sarah Loreau, a single mother training with ESA for a year-long ISS mission; filmed at real ESA, Star City, and Baikonur facilities; San Sebastián Special Jury Prize winner.
Proximity operations
Proximity operations, usually paired with rendezvous as RPO, are spacecraft maneuvers in which one vehicle flies near another space object to observe, inspect, service, or capture it.
PSLV
The Polar Satellite Launch Vehicle (PSLV) is a four-stage Indian rocket operated by ISRO since 1993, nicknamed the Workhorse of ISRO. In 2017 it launched 104 satellites in one flight.
Psyche (spacecraft)
Psyche is a NASA robotic orbiter launched on October 13, 2023, to study the metal-rich asteroid 16 Psyche, believed to be an exposed planetary core, arriving in 2029.
Pulsed plasma thruster
A pulsed plasma thruster (PPT) is an electric rocket engine that produces tiny pulses of thrust by discharging a capacitor across solid Teflon propellant, used for small-satellite attitude control since 1964.
Pumped fluid loop thermal control
Pumped fluid loop thermal control is an active spacecraft thermal control technique in which a pump circulates fluid to collect heat and reject it at a radiator.
Pushbroom scanner
A pushbroom scanner is an imaging instrument, typically carried by a satellite, that records an image one line at a time using a linear array of detectors.
Qianfan Xingzuo
Qianfan Xingzuo (千帆星座), also known as Spacesail or G60, is a Chinese low Earth orbit broadband megaconstellation operated by Shanghai Spacecom as a competitor to Starlink.
Quasi-Zenith Satellite System (準天頂衛星システム)
The Quasi-Zenith Satellite System (準天頂衛星システム), QZSS, nicknamed Michibiki, is Japan's satellite positioning system, complementing GPS in the Asia-Oceania region; four-satellite service began in 2018, expanding toward seven satellites.
Queqiao
Queqiao (鹊桥, "Magpie Bridge") is a series of Chinese lunar relay communication satellites; the first, launched in 2018, became the first satellite in a halo orbit around Earth-Moon L2, relaying for Chang'e-4.
QUEST
QUEST (QUaternion ESTimator) is a fast closed-form algorithm for spacecraft attitude determination from reference directions, published by Shuster and Oh in 1981 and used in hundreds of space missions.
QuickBird
QuickBird was a commercial Earth-imaging satellite built by Ball Aerospace and operated by DigitalGlobe of Longmont, Colorado, delivering the highest-resolution imagery then commercially available from its launch in 2001 until its retirement in 2015.
R-7
The R-7 (Семёрка, Semyorka) was the world's first intercontinental ballistic missile, developed in the Soviet Union under Sergei Korolev, first flown in 1957 and later launching Sputnik.
R-7 Semyorka
The R-7 Semyorka, also known as the SS-6 Sapwood, was the world's first intercontinental ballistic missile, developed at Sergei Korolev's OKB-1 and first flown successfully in August 1957.
RADARSAT
RADARSAT is a Canadian series of Earth observation satellites carrying synthetic aperture radar, which images day or night and through cloud, spanning RADARSAT-1 in 1995, RADARSAT-2 in 2007, and a three-satellite constellation launched in 2019.
Radiator panel (spacecraft)
A radiator panel is an external spacecraft surface that rejects waste heat by thermal radiation, connected to heat sources through heat pipes, pumped fluid loops, or thermal straps.
Radioisotope heater unit
A radioisotope heater unit (RHU) is a small spacecraft device that warms components through plutonium-238 decay, producing about one watt of heat with no moving parts or electrical power.
Radioisotope thermoelectric generator
A radioisotope thermoelectric generator (RTG) is a spacecraft power source that turns heat from decaying plutonium-238 into electricity with no moving parts, powering missions where sunlight is too faint for solar panels.
Raduga
Raduga, secret designation Gran, was a series of Soviet and Russian military communications satellites, the first operational Soviet satellites in geostationary orbit, launched from 1975.
Rakesh Sharma (राकेश शर्मा)
Rakesh Sharma (राकेश शर्मा) is a retired Indian Air Force officer who became the first Indian citizen in space, flying to the Salyut 7 station aboard Soyuz T-11 in 1984.
Ram accelerator
A ram accelerator is a hypervelocity launch device in which a ramjet-like projectile flies through a tube of combustible gas, reaching velocities above 2.6 km/s.
RAMSES
RAMSES (Rapid Apophis Mission for Space Safety) is a joint ESA–JAXA space mission to rendezvous with the asteroid 99942 Apophis before its harmless close flyby of Earth in April 2029.