G-jitter references forms of periodic [1] or quasisteady residual acceleration encountered in a spacecraft floating through the micro-gravity confines of space. Such variations slightly change the orientation and magnitude of a body force in a low-gravity testing environment, [2] which can either marginally or gravely affect the result of precision-heavy dependent experiments conducted on board a space station. [3] These accelerations are often the result of routine crew activity and equipment operation and the aerodynamic and aeromechanical forces on the spacecraft itself. [2] Using current theoretical methods and previously collected experimental data, it is impossible to predict the exact behavior of a g-jitter acceleration, but with the aforementioned data, it is possible to notice and account for qualitative trends that hold true for most scenarios pertaining to material science testing on board a space station. [2]
Constant forces that last over 10 minutes while varying periodically in a single frequency can provide a noticeable offset in acceleration readings and deviate a testing environment from "true" micro-gravity. The stronger set of these forces result in non-negligible tidal accelerations and the varying aerodynamic drag of the space station, which fluctuates over the course of an orbit due to the changes in the space station's aspect angle, diurnal cycle, and variable solar activity. [4] In some fringe cases, Euler accelerations must be accounted for as they affect low-pressure physical vapor transport. Coriolis accelerations and solar radiation pressure can be also observed, but are generally negligible in comparison to the effects of other quasi-steady forces. [2]
Generally, if a disturbance can be replicated by a sinusoidal modulation, it is considered to be an oscillatory component of g-jitter. The most noticeable disturbances being routine crew activity and structural vibrations, and can cause a structural resonance throughout a space vehicle. While the average frequency of the structural vibration of a space station is lesser than a Space Shuttle orbiter, the frequency range can still be between the ranges of 0.1 to 1 Hz. [2]
The largest in magnitude are likely to be caused by thruster firings, Shuttle dockings or berthings, and mass translations. Some disruptions can be controlled and timed as to not affect on-site testing, such as thruster firings and Shuttle dockings. The relatively innocuous routinely activities astronauts conduct in a space station ranging from maintenance or moving freely around the station add onto a category of impermanent disturbances that are more spontaneous and unpredictable, which cannot be as easily accounted for. [2]
Due to the rise in the awareness of the implications of g-jitter, accelerometers with capabilities to attune to a hectic low-gravity environment have begun to be incorporated within space vehicles. Past experiments conducted in the Space Shuttle environment have served as a base to correlate g-jitter's effects to testing in material science and numerically model the residual acceleration to help devise specific experiments for a particular environment. [2] Methods for the analysis of acceleration readings are readily available, but the difficult task of shifting through all the raw data can be facilitated by keeping a timeline of the recorded events and correlate them to a respective residual acceleration. [5]
STS-50 was a NASA Space Shuttle mission, the 12th mission of the Columbia orbiter. Columbia landed at Kennedy Space Center for the first time ever due to bad weather at Edwards Air Force Base caused by the remnants of Hurricane Darby.
STS-58 was a NASA mission flown by Space Shuttle Columbia launched from Kennedy Space Center, Florida, on October 18, 1993. The missions was primarily devoted to experiments concerning the physiological effects in space. This was the first in-flight use of the "Portable In-flight Landing Operations Trainer" (PILOT) simulation software. It was also the last time Columbia would land at Edwards Air Force Base, California.
STS-62 was a Space Shuttle program mission flown aboard Space ShuttleColumbia. The primary payloads were the USMP-02 microgravity experiments package and the OAST-2 engineering and technology payload, both in the orbiter's cargo bay. The two-week mission also featured a number of biomedical experiments focusing on the effects of long duration spaceflight. The landing was chronicled by the 1994 Discovery Channel special about the Space Shuttle program and served as the show's opening. A C.F. Martin backpacker guitar was also flown aboard Columbia during the mission.
STS-65 was a Space Shuttle program mission of Columbia launched from Kennedy Space Center, Florida, 8 July 1994. The flight carried a crew of 7 and was commanded by Robert D. Cabana who would go on later to lead the Kennedy Space Center. STS-65 was an international science mission that carried the International Microgravity Laboratory (IML-2) on an 15-day mission. Columbia returned to the Kennedy Space Center on 23 July 1994.
STS-64 was a Space Shuttle Discovery mission that was set to perform multiple experiment packages. STS-64 was launched from Kennedy Space Center, Florida, on 9 September 1994, and landed back on 20 September 1994 at Edwards Air Force Base.
STS-66 was a Space Shuttle program mission that was flown by the Space Shuttle Atlantis. STS-66 launched on November 3, 1994, at 11:59:43.060 am EDT from Launch Pad 39-B at NASA's Kennedy Space Center. Atlantis landed at Edwards Air Force Base on November 14, 1994, at 10:33:45 am EST.
STS-63 was the second mission of the US/Russian Shuttle-Mir Program, which carried out the first rendezvous of the American Space Shuttle with Russia's space station Mir. Known as the 'Near-Mir' mission, the flight used Space Shuttle Discovery, which lifted off from launch pad 39B on February 3, 1995, from Kennedy Space Center, Florida. A night launch and the 20th mission for Discovery, it marked the first time a Space Shuttle mission had a female pilot, Eileen Collins, and the first EVAs for both a UK born astronaut, Michael Foale, and a US astronaut of African heritage, Bernard A. Harris, Jr. It also carried out the successful deployment and retrieval of the Spartan-204 platform, along with the scheduled rendezvous and flyaround of Mir, in preparation for STS-71, the first mission to dock with Mir.
STS-73 was a Space Shuttle program mission, during October–November 1995, on board the Space Shuttle Columbia. The mission was the second mission for the United States Microgravity Laboratory. The crew, who spent 16 days in space, were broken up into 2 teams, the red team and the blue team. The mission also included several Detailed Test Objectives or DTO's.
STS-87 was a Space Shuttle mission launched from Launch Complex 39B of the Kennedy Space Center on 19 November 1997. It was the 88th flight of the Space Shuttle and the 24th flight of Columbia. The mission goals were to conduct experiments using the United States Microgravity Payload (USMP-4), conduct two EVAs, and deploy the SPARTAN-201 experiment. This mission marked the first time an EVA was performed from Columbia. An EVA from Columbia was originally planned for STS-5 in 1982 but was canceled due to spacesuit problems. It also marked the first EVA conducted by a Japanese astronaut, Takao Doi.
STS-95 was a Space Shuttle mission launched from Kennedy Space Center, Florida on 29 October 1998, using the orbiter Discovery. It was the 25th flight of Discovery and the 92nd mission flown since the start of the Space Shuttle program in April 1981. It was a highly publicized mission due to former Project Mercury astronaut and United States Senator John H. Glenn Jr.'s return to space for his second space flight. At age 77, Glenn became the oldest person to go into space, a record that remained unbroken for 23 years until 82-year-old Wally Funk flew on a suborbital flight on Blue Origin NS-16, launching on 20 July 2021, which in turn was broken by William Shatner at age 90 on 13 October 2021. Glenn, however, remains the oldest person to reach Earth orbit. This mission is also noted for inaugurating ATSC HDTV broadcasting in the U.S., with live coast-to-coast coverage of the launch. In another first, Pedro Duque became the first Spaniard in space.
Gravimetry is the measurement of the strength of a gravitational field. Gravimetry may be used when either the magnitude of a gravitational field or the properties of matter responsible for its creation are of interest. The study of gravity changes belongs to geodynamics.
Artificial gravity is the creation of an inertial force that mimics the effects of a gravitational force, usually by rotation. Artificial gravity, or rotational gravity, is thus the appearance of a centrifugal force in a rotating frame of reference, as opposed to the force experienced in linear acceleration, which by the equivalence principle is indistinguishable from gravity. In a more general sense, "artificial gravity" may also refer to the effect of linear acceleration, e.g. by means of a rocket engine.
A reentry capsule is the portion of a space capsule which returns to Earth following a spaceflight. The shape is determined partly by aerodynamics; a capsule is aerodynamically stable falling blunt end first, which allows only the blunt end to require a heat shield for atmospheric entry. A crewed capsule contains the spacecraft's instrument panel, limited storage space, and seats for crew members. Because a capsule shape has little aerodynamic lift, the final descent is via parachute, either coming to rest on land, at sea, or by active capture by an aircraft. In contrast, the development of spaceplane reentry vehicles attempts to provide a more flexible reentry profile.
The Synchronized Position Hold Engage and Reorient Experimental Satellite (SPHERES) are a series of miniaturized satellites developed by MIT's Space Systems Laboratory for NASA and US Military, to be used as a low-risk, extensible test bed for the development of metrology, formation flight, rendezvous, docking and autonomy algorithms that are critical for future space missions that use distributed spacecraft architecture, such as Terrestrial Planet Finder and Orbital Express.
A gravity turn or zero-lift turn is a maneuver used in launching a spacecraft into, or descending from, an orbit around a celestial body such as a planet or a moon. It is a trajectory optimization that uses gravity to steer the vehicle onto its desired trajectory. It offers two main advantages over a trajectory controlled solely through the vehicle's own thrust. First, the thrust is not used to change the spacecraft's direction, so more of it is used to accelerate the vehicle into orbit. Second, and more importantly, during the initial ascent phase the vehicle can maintain low or even zero angle of attack. This minimizes transverse aerodynamic stress on the launch vehicle, allowing for a lighter launch vehicle.
Weightlessness is the complete or near-complete absence of the sensation of weight, i.e., zero apparent weight. It is also termed zero g-force, or zero-g or, incorrectly, zero gravity.
Space neuroscience or astroneuroscience is the scientific study of the central nervous system (CNS) functions during spaceflight. Living systems can integrate the inputs from the senses to navigate in their environment and to coordinate posture, locomotion, and eye movements. Gravity has a fundamental role in controlling these functions. In weightlessness during spaceflight, integrating the sensory inputs and coordinating motor responses is harder to do because gravity is no longer sensed during free-fall. For example, the otolith organs of the vestibular system no longer signal head tilt relative to gravity when standing. However, they can still sense head translation during body motion. Ambiguities and changes in how the gravitational input is processed can lead to potential errors in perception, which affects spatial orientation and mental representation. Dysfunctions of the vestibular system are common during and immediately after spaceflight, such as space motion sickness in orbit and balance disorders after return to Earth.
LISA Pathfinder, formerly Small Missions for Advanced Research in Technology-2 (SMART-2), was an ESA spacecraft that was launched on 3 December 2015 on board Vega flight VV06. The mission tested technologies needed for the Laser Interferometer Space Antenna (LISA), an ESA gravitational wave observatory planned to be launched in 2035. The scientific phase started on 8 March 2016 and lasted almost sixteen months. In April 2016 ESA announced that LISA Pathfinder demonstrated that the LISA mission is feasible.
The Micro-Satellite à traînée Compensée pour l'Observation du Principe d'Equivalence is a 300-kilogram (660 lb) class minisatellite operated by CNES to test the universality of free fall with a precision to the order of 10−15, 100 times more precise than can be achieved on Earth. It was launched on 25 April 2016 alongside Sentinel-1B and other small satellites, and was decommissioned around 18 October 2018 after completion of its science objectives. The final report was published in 2022.
This glossary of aerospace engineering terms pertains specifically to aerospace engineering, its sub-disciplines, and related fields including aviation and aeronautics. For a broad overview of engineering, see glossary of engineering.