Theg-forceorgravitational force equivalentis amass-specific force(force per unit mass), expressed inunitsofstandard gravity(symbolgorg0,not to be confused with "g", the symbol forgrams). It is used for sustainedaccelerationsthat cause a perception ofweight.For example, an object at rest on Earth's surface is subject to 1g,equaling the conventional value ofgravitational accelerationon Earth, about9.8m/s2.[1] More transient acceleration, accompanied with significantjerk,is calledshock.[citation needed]
When the g-force is produced by the surface of one object being pushed by the surface of another object, the reaction force to this push produces an equal and opposite force for every unit of each object's mass. The types of forces involved are transmitted through objects by interiormechanical stresses.Gravitational accelerationis one cause of an object'saccelerationin relation tofree fall.[2][3]
The g-force experienced by an object is due to the vector sum of all gravitational and non-gravitational forces acting on an object's freedom to move. In practice, as noted, these are surface-contact forces between objects. Such forces causestressesandstrainson objects, since they must be transmitted from an object surface. Because of these strains, large g-forces may be destructive.
For example, a force of 1gon an object sitting on the Earth's surface is caused by the mechanical force exerted in theupward direction by the ground,keeping the object from going into free fall. The upward contact force from the ground ensures that an object at rest on the Earth's surface is accelerating relative to the free-fall condition. (Free fall is the path that the object would follow when falling freely toward the Earth's center). Stress inside the object is ensured from the fact that the ground contact forces are transmitted only from the point of contact with the ground.
Objects allowed to free-fall in aninertial trajectory,under the influence of gravitation only, feel no g-force – a condition known asweightlessness.Being in free fall in an inertial trajectory is colloquially called "zero-g",which is short for" zero g-force ". Zero g-force conditions would occur inside an elevator falling freely toward the Earth's center (in vacuum), or(to good approximation) inside a spacecraft in Earth orbit.These are examples of coordinate acceleration (a change in velocity) without a sensation of weight.
In the absence of gravitational fields, or in directions at right angles to them, proper and coordinate accelerations are the same, and any coordinate acceleration must be produced by a corresponding g-force acceleration. An example of this is a rocket in free space: when the engines produce simple changes in velocity, those changes cause g-forces on the rocket and the passengers.
Unit and measurement
editTheunit of measureofaccelerationin theInternational System of Units(SI) is m/s2.[4]However, to distinguish acceleration relative to free fall from simple acceleration (rate of change of velocity), the unitgis often used. Onegis the force per unit mass due to gravity at the Earth's surface and is thestandard gravity(symbol:gn), defined as9.80665metres per second squared,[5]or equivalently9.80665newtonsof force per kilogram of mass. Theunit definitiondoes not vary with location—the g-force when standing on theMoonis almost exactly1⁄6that on Earth. The unitgis not one of the SI units, which uses "g" for gram. Also, "g"should not be confused with"G",which is the standard symbol for thegravitational constant.[6]This notation is commonly used in aviation, especially in aerobatic or combat military aviation, to describe the increased forces that must be overcome by pilots in order to remain conscious and notg-LOC(g-induced loss of consciousness).[7]
Measurement of g-force is typically achieved using anaccelerometer(see discussion below in section#Measurement using an accelerometer). In certain cases, g-forces may be measured using suitably calibrated scales.
Acceleration and forces
editThe term g- "force" is technically incorrect as it is a measure ofacceleration,not force. While acceleration is avectorquantity, g-force accelerations ( "g-forces" for short) are often expressed as ascalar,based on the vector magnitude, with positive g-forces pointing downward (indicating upward acceleration), and negative g-forces pointing upward. Thus, a g-force is a vector of acceleration. It is an acceleration that must be produced by a mechanical force, and cannot be produced by simple gravitation. Objects acted upononlyby gravitation experience (or "feel" ) no g-force, and are weightless. g-forces, when multiplied by a mass upon which they act, are associated with a certain type of mechanicalforcein the correct sense of the term "force", and this force producescompressive stressandtensile stress.Such forces result in the operational sensation of weight, but the equation carries a sign change due to the definition of positive weight in the direction downward, so the direction of weight-force is opposite to the direction of g-force acceleration:
- Weight = mass × −g-force
The reason for the minus sign is that the actualforce(i.e., measured weight) on an object produced by a g-force is in the opposite direction to the sign of the g-force, since in physics, weight is not the force that produces the acceleration, but rather the equal-and-opposite reaction force to it. If the direction upward is taken as positive (the normal cartesian convention) thenpositiveg-force (an acceleration vector that points upward) produces a force/weight on any mass, that actsdownward(an example is positive-g acceleration of a rocket launch, producing downward weight). In the same way, anegative-g forceis an acceleration vectordownward(the negative direction on the y axis), and this acceleration downward produces a weight-force in a directionupward(thus pulling a pilot upward out of the seat, and forcing blood toward the head of a normally oriented pilot).
If a g-force (acceleration) is vertically upward and is applied by the ground (which is accelerating through space-time) or applied by the floor of an elevator to a standing person, most of the body experiences compressive stress which at any height, if multiplied by the area, is the related mechanical force, which is the product of the g-force and the supported mass (the mass above the level of support, including arms hanging down from above that level). At the same time, the arms themselves experience a tensile stress, which at any height, if multiplied by the area, is again the related mechanical force, which is the product of the g-force and the mass hanging below the point of mechanical support. The mechanical resistive force spreads from points of contact with the floor or supporting structure, and gradually decreases toward zero at the unsupported ends (the top in the case of support from below, such as a seat or the floor, the bottom for a hanging part of the body or object). With compressive force counted as negative tensile force, the rate of change of the tensile force in the direction of the g-force, per unit mass (the change between parts of the object such that the slice of the object between them has unit mass), is equal to the g-force plus the non-gravitational external forces on the slice, if any (counted positive in the direction opposite to the g-force).
For a given g-force the stresses are the same, regardless of whether this g-force is caused by mechanical resistance to gravity, or by a coordinate-acceleration (change in velocity) caused by a mechanical force, or by a combination of these. Hence, for people all mechanical forces feels exactly the same whether they cause coordinate acceleration or not. For objects likewise, the question of whether they can withstand the mechanical g-force without damage is the same for any type of g-force. For example, upward acceleration (e.g., increase of speed when going up or decrease of speed when going down) on Earth feels the same as being stationary on a celestial body with a highersurface gravity.Gravitation acting alone does not produce any g-force; g-force is only produced from mechanical pushes and pulls. For a free body (one that is free to move in space) such g-forces only arise as the "inertial" path that is the natural effect of gravitation, or the natural effect of the inertia of mass, is modified. Such modification may only arise from influences other than gravitation.
Examples of important situations involving g-forces include:
- The g-force acting on a stationary object resting on the Earth's surface is 1g(upwards) and results from the resisting reaction of the Earth's surface bearing upwards equal to an acceleration of 1g,and is equal and opposite to gravity. The number 1 is approximate, depending on location.
- The g-force acting on an object in anyweightlessenvironment such as free-fall in a vacuum is 0g.
- The g-force acting on an object under acceleration can be much greater than 1g,for example, the dragster pictured at top right can exert a horizontal g-force of 5.3 when accelerating.
- The g-force acting on an object under acceleration may be downwards, for example when cresting a sharp hill on a roller coaster.
- If there are no other external forces than gravity, the g-force in arocketis thethrustper unit mass. Its magnitude is equal to thethrust-to-weight ratiotimesg,and to the consumption ofdelta-vper unit time.
- In the case of ashock,e.g., acollision,the g-force can be very large during a short time.
A classic example of negative g-force is in a fully invertedroller coasterwhich is accelerating (changing velocity) toward the ground. In this case, the roller coaster riders are accelerated toward the ground faster than gravity would accelerate them, and are thus pinned upside down in their seats. In this case, the mechanical force exerted by the seat causes the g-force by altering the path of the passenger downward in a way that differs from gravitational acceleration. The difference in downward motion, now faster than gravity would provide, is caused by the push of the seat, and it results in a g-force toward the ground.
All "coordinate accelerations" (or lack of them), are described byNewton's laws of motionas follows:
TheSecond Law of Motion,the law of acceleration, states thatF=ma,meaning that a forceFacting on a body is equal to themassmof the body times its accelerationa.
TheThird Law of Motion,the law of reciprocal actions, states that all forces occur in pairs, and these two forces are equal in magnitude and opposite in direction. Newton's third law of motion means that not only does gravity behave as a force acting downwards on, say, a rock held in your hand but also that the rock exerts a force on the Earth, equal in magnitude and opposite in direction.
In an airplane, the pilot's seat can be thought of as the hand holding the rock, the pilot as the rock. When flying straight and level at 1g,the pilot is acted upon by the force of gravity. His weight (a downward force) is 725newtons(163lbf). In accordance with Newton's third law, the plane and the seat underneath the pilot provides an equal and opposite force pushing upwards with a force of 725 N. This mechanical force provides the 1.0gupwardproper accelerationon the pilot, even though this velocity in the upward direction does not change (this is similar to the situation of a person standing on the ground, where the ground provides this force and this g-force).
If the pilot were suddenly to pull back on the stick and make his plane accelerate upwards at 9.8 m/s2,the total g‑force on his body is 2g,half of which comes from the seat pushing the pilot to resist gravity, and half from the seat pushing the pilot to cause his upward acceleration—a change in velocity which also is aproper accelerationbecause it also differs from a free fall trajectory. Considered in the frame of reference of the plane his body is now generating a force of 1,450 N (330 lbf) downwards into his seat and the seat is simultaneously pushing upwards with an equal force of 1450 N.
Unopposed acceleration due to mechanical forces, and consequentially g-force, is experienced whenever anyone rides in a vehicle because it always causes a proper acceleration, and (in the absence of gravity) also always a coordinate acceleration (where velocity changes). Whenever the vehicle changes either direction or speed, the occupants feel lateral (side to side) or longitudinal (forward and backwards) forces produced by the mechanical push of their seats.
The expression"1g=9.80665m/s2"means thatfor every second that elapses,velocity changes9.80665metres per second (35.30394km/h). This rate of change in velocity can also be denoted as9.80665(metres per second) per second, or9.80665m/s2.For example: An acceleration of 1gequates to a rate of change in velocity of approximately 35 km/h (22 mph) for each second that elapses. Therefore, if an automobile is capable of braking at 1gand is traveling at 35 km/h, it can brake to a standstill in one second and the driver will experience a deceleration of 1g.The automobile traveling at three times this speed, 105 km/h (65 mph), can brake to a standstill in three seconds.
In the case of an increase in speed from 0 tovwith constant acceleration within a distance ofsthis acceleration isv2/(2s).
Preparing an object for g-tolerance (not getting damaged when subjected to a high g-force) is called g-hardening.[citation needed]This may apply to, e.g., instruments in aprojectileshot by a gun.
Human tolerance
edit
Human tolerances depend on the magnitude of the gravitational force, the length of time it is applied, the direction it acts, the location of application, and the posture of the body.[9][10]: 350
The human body is flexible and deformable, particularly the softer tissues. A hard slap on the face may briefly impose hundreds ofglocally but not produce any real damage; a constant 16gfor a minute, however, may be deadly. Whenvibrationis experienced, relatively low peak g-force levels can be severely damaging if they are at theresonant frequencyof organs or connective tissues.[citation needed]
To some degree, g-tolerance can be trainable, and there is also considerable variation in innate ability between individuals. In addition, some illnesses, particularlycardiovascularproblems, reduce g-tolerance.
Vertical
editAircraft pilots (in particular) sustain g-forces along the axis aligned with the spine. This causes significant variation in blood pressure along the length of the subject's body, which limits the maximum g-forces that can be tolerated.
Positive, or "upward" g-force, drives blood downward to the feet of a seated or standing person (more naturally, the feet and body may be seen as being driven by the upward force of the floor and seat, upward around the blood). Resistance to positive g-force varies. A typical person can handle about 5g0(49 m/s2) (meaning some people might pass out when riding a higher-g roller coaster, which in some cases exceeds this point) beforelosing consciousness,but through the combination of specialg-suitsand efforts to strain muscles—both of which act to force blood back into the brain—modern pilots can typically handle a sustained 9g0(88 m/s2) (seeHigh-G training).
In aircraft particularly, vertical g-forces are often positive (force blood towards the feet and away from the head); this causes problems with the eyes and brain in particular. As positive vertical g-force is progressively increased (such as in acentrifuge) the following symptoms may be experienced:[citation needed]
- Grey-out,where the vision loses hue, easily reversible on levelling out
- Tunnel vision,where peripheral vision is progressively lost
- Blackout, a loss of vision while consciousness is maintained, caused by a lack of blood flow to the head
- G-LOC,a g-force induced loss of consciousness[11]
- Death, if g-forces are not quickly reduced
Resistance to "negative" or "downward" g, which drives blood to the head, is much lower. This limit is typically in the −2 to −3g0(−20 to −29 m/s2) range. This condition is sometimes referred to asred outwhere vision is literally reddened[12]due to the blood-laden lower eyelid being pulled into the field of vision.[13]Negative g-force is generally unpleasant and can cause damage. Blood vessels in the eyes or brain may swell or burst under the increased blood pressure, resulting in degraded sight or even blindness.
Horizontal
editThe human body is better at surviving g-forces that are perpendicular to the spine. In general when the acceleration is forwards (subject essentially lying on their back, colloquially known as "eyeballs in" ),[14]a much higher tolerance is shown than when the acceleration is backwards (lying on their front, "eyeballs out" ) since blood vessels in the retina appear more sensitive in the latter direction.[citation needed]
Early experiments showed that untrained humans were able to tolerate a range of accelerations depending on the time of exposure. This ranged from as much as20g0for less than 10 seconds, to10g0for 1 minute, and6g0for 10 minutes for both eyeballs in and out.[15]These forces were endured with cognitive facilities intact, as subjects were able to perform simple physical and communication tasks. The tests were determined not to cause long- or short-term harm although tolerance was quite subjective, with only the most motivated non-pilots capable of completing tests.[16]The record for peak experimental horizontal g-force tolerance is held by acceleration pioneerJohn Stapp,in a series of rocket sled deceleration experiments culminating in a late 1954 test in which he was clocked in a little over a second from a land speed of Mach 0.9. He survived a peak "eyeballs-out" acceleration of 46.2 times the acceleration of gravity, and more than25g0for 1.1 seconds, proving that the human body is capable of this. Stapp lived another 45 years to age 89[17]without any ill effects.[18]
The highest recorded g-force experienced by a human who survived was during the2003 IndyCar Seriesfinale at Texas Motor Speedway on 12 October 2003, in the 2003 Chevy 500 when the car driven byKenny Bräckmade wheel-to-wheel contact withTomas Scheckter's car. This immediately resulted in Bräck's car impacting the catch fence that would record a peak of214g0.[19][20]
Short duration shock, impact, and jerk
editImpactandmechanical shockare usually used to describe a high-kinetic-energy,short-term excitation. A shock pulse is often measured by its peak acceleration inɡ0·s and the pulse duration.Vibrationis a periodicoscillationwhich can also be measured inɡ0·s as well as frequency. The dynamics of these phenomena are what distinguish them from the g-forces caused by a relatively longer-term accelerations.[citation needed]
After a free fall from a heightfollowed by deceleration over a distanceduring an impact, the shock on an object is·ɡ0.For example, a stiff and compact object dropped from 1 m that impacts over a distance of 1 mm is subjected to a 1000ɡ0deceleration.[citation needed]
Jerkis the rate of change of acceleration. In SI units, jerk is expressed as m/s3;it can also be expressed instandard gravityper second (ɡ0/s; 1ɡ0/s ≈ 9.81 m/s3).[citation needed]
Other biological responses
editRecent research carried out onextremophilesin Japan involved a variety of bacteria (includingE. colias a non-extremophile control) being subject to conditions of extreme gravity. The bacteria were cultivated while being rotated in anultracentrifugeat high speeds corresponding to 403,627 g.Paracoccus denitrificanswas one of the bacteria that displayed not only survival but also robust cellular growth under these conditions of hyperacceleration, which are usually only to be found in cosmic environments, such as on very massive stars or in the shock waves ofsupernovas.Analysis showed that the small size of prokaryotic cells is essential for successful growth underhypergravity.Notably, two multicellular species, thenematodesPanagrolaimus superbus[21]andCaenorhabditis eleganswere shown to be able to tolerate 400,000 ×gfor 1 hour.[22] The research has implications on the feasibility ofpanspermia.[23][24]
Typical examples
edit| Example | g-force[a] |
|---|---|
| The gyro rotors inGravity Probe Band the free-floating proof masses in the TRIAD I navigation satellite[25] | 0g |
| A ride in theVomit Comet(parabolic flight) | ≈0g |
| Standing onMimas,the smallest and least massive known bodyrounded by its own gravity | 0.006g |
| Standing onCeres,the smallest and least massive known bodycurrentlyinhydrostatic equilibrium | 0.029g |
| Standing onPlutoat average ground level | 0.063g |
| Standing onErisat average ground level | 0.084g |
| Standing onTitanat average ground level | 0.138g |
| Standing onGanymedeat average surface level | 0.146g |
| Standing on theMoonat surface level | 0.1657g |
| 2000Toyota Siennafrom 0 to 100 km/h in 9.2 s[26] | 0.3075–0.314g |
| Standing onMercury | 0.377g |
| Standing onMarsat its equator at mean ground level | 0.378g |
| Standing onVenusat average ground level | 0.905g |
| Standing on Earth at sea level–standard | 1g |
| Saturn VMoon rocket just after launch and the gravity ofNeptunewhere atmospheric pressure is about Earth's | 1.14g |
| Bugatti Veyronfrom 0 to 100 km/h in 2.4 s | 1.55g[b] |
| Gravitronamusement ride | 2.5–3g |
| Gravity ofJupiterat its mid-latitudes and where atmospheric pressure is about Earth's | 2.528g |
| Uninhibited sneeze after sniffing ground pepper[27] | 2.9g |
| Space Shuttle,maximum during launch and reentry | 3g |
| High-groller coasters[10]: 340 | 3.5–12g |
| Hearty greeting slap on upper back[27] | 4.1g |
| Top Fueldrag racingworld record of 4.4 s over 1/4 mile | 4.2g |
| First world war aircraft (ex:Sopwith Camel,Fokker Dr.1,SPAD S.XIII,Nieuport 17,Albatros D.III) in dogfight maneuvering. | 4.5–7g |
| Luge,maximum expected at the Whistler Sliding Centre | 5.2g |
| Formula One car,maximum under heavy braking[28] | 6.3g |
| Tower Of Terror,highest g-force steel rollercoaster | 6.3g |
| Formula One car,peak lateral in turns[29] | 6–6.5g |
| Standard, full aerobatics certifiedglider | +7/−5g |
| Apollo 16on reentry[30] | 7.19g |
| Maximum permitted g-force inSukhoi Su-27plane | 9g |
| Maximum permitted g-force inMikoyan MiG-35plane and maximum permitted g-force turn inRed Bull Air Raceplanes | 10g |
| Flip Flap Railway,highest g-force wooden rollercoaster | 12g |
| Jet Fighter pilot duringejection seatactivation | 15–25g |
| Gravitational acceleration at the surface of theSun | 28g |
| Maximum g-force inTor missile system[31] | 30g |
| Maximum for human on a rocket sled | 46.2g |
| Formula One2021 British Grand PrixMax VerstappenCrash withLewis Hamilton | 51g |
| Formula One2020 Bahrain Grand PrixRomain GrosjeanCrash[32] | 67g |
| Sprint missile | 100g |
| Brief human exposure survived in crash[33] | > 100g |
| IndyCar2003 TexasKenny BräckCrash | 214g |
| Formula One2014 Japanese Grand PrixJules BianchiCrash | 254g |
| Formula One1994 Monaco Grand PrixKarl Wendlinger[34]Crash | ≈360g |
| Coronal mass ejection(Sun)[35] | 480g |
| Formula One1994 San Marino Grand PrixRoland RatzenbergerQualifying Crash | 500g |
| Space gunwith a barrel length of 1 km and amuzzle velocityof 6 km/s, as proposed byQuicklaunch(assuming constant acceleration) | 1,800g |
| Shock capability of mechanical wrist watches[36] | > 5,000g |
| V8Formula One engine,maximum piston acceleration[37] | 8,600g |
| Mantis Shrimp,acceleration of claw during predatory strike[38] | 10,400g |
| Rating of electronics built into military artillery shells[39] | 15,500g |
| Analytical ultracentrifuge spinning at 60,000 rpm, at the bottom of the analysis cell (7.2 cm)[40] | 300,000g |
| Calculated acceleration of the mandibles of the ant speciesMystrium camillae[41] | 607,805g |
| Acceleration of anematocyst:the fastest recorded acceleration from any biological entity.[42] | 5,410,000g |
| Mean acceleration of a proton in theLarge Hadron Collider[43] | 190,000,000g |
| Gravitational acceleration at the surface of a typicalneutron star[44] | 2.0×1011g |
| Acceleration from awakefield plasma accelerator[45] | 8.9×1020g |
Measurement using an accelerometer
edit
Anaccelerometer,in its simplest form, is adampedmass on the end of a spring, with some way of measuring how far the mass has moved on the spring in a particular direction, called an 'axis'.
Accelerometers are oftencalibratedto measure g-force along one or more axes. If a stationary, single-axis accelerometer is oriented so that its measuring axis is horizontal, its output will be 0g,and it will continue to be 0gif mounted in an automobile traveling at a constant velocity on a level road. When the driver presses on the brake or gas pedal, the accelerometer will register positive or negative acceleration.
If the accelerometer is rotated by 90° so that it is vertical, it will read +1gupwards even though stationary. In that situation, the accelerometer is subject to two forces: thegravitational forceand theground reaction forceof the surface it is resting on. Only the latter force can be measured by the accelerometer, due to mechanical interaction between the accelerometer and the ground. The reading is the acceleration the instrument would have if it were exclusively subject to that force.
A three-axis accelerometer will output zero‑g on all three axes if it is dropped or otherwise put into aballistictrajectory (also known as aninertialtrajectory), so that it experiences "free fall", as do astronauts in orbit (astronauts experience small tidal accelerations called microgravity, which are neglected for the sake of discussion here). Some amusement park rides can provide several seconds at near-zero g. Riding NASA's "Vomit Comet"provides near-zero g-force for about 25 seconds at a time.
See also
editNotes and references
edit- ^Deziel, Chris."How to Convert Newtons to G-Force".sciencing.Archivedfrom the original on 29 January 2023.Retrieved17 January2021.
- ^G ForceArchived25 January 2012 at theWayback Machine.Newton.dep.anl.gov. Retrieved on 14 October 2011.
- ^Sircar, Sabyasachi (12 December 2007).Principles of Medical Physiology.Thieme.ISBN978-1-58890-572-7.Archivedfrom the original on 21 July 2023.Retrieved21 September2020.
- ^"SI Units – Length".NIST.12 April 2010.Archivedfrom the original on 18 December 2022.Retrieved18 December2022.
- ^BIPM:Declaration on the unit of mass and on the definition of weight; conventional value of gnArchived16 October 2021 at theWayback Machine.
- ^Symbol g: ESA: GOCE,Basic Measurement UnitsArchivedFebruary 12, 2012, at theWayback Machine,NASA:Multiple GArchivedDecember 25, 2017, at theWayback Machine,Astronautix:StappArchivedMarch 21, 2009, at theWayback Machine,Honeywell:AccelerometersArchivedFebruary 17, 2009, at theWayback Machine,Sensr LLC:GP1 Programmable AccelerometerArchivedFebruary 1, 2009, at theWayback Machine,Farnell:accelometers[permanent dead link],Delphi:Accident Data Recorder 3 (ADR3) MS0148ArchivedDecember 2, 2008, at theWayback Machine,NASA:Constants and Equations for CalculationsArchivedJanuary 18, 2009, at theWayback Machine,Jet Propulsion Laboratory:A Discussion of Various Measures of AltitudeArchivedFebruary 10, 2009, at theWayback Machine,National Highway Traffic Safety Administration:Recording Automotive Crash Event DataArchivedApril 5, 2010, at theWayback Machine
Symbol G: Lyndon B. Johnson Space Center:ENVIRONMENTAL FACTORS: BIOMEDICAL RESULTS OF APOLLO,Section II, Chapter 5Archived22 November 2008 at theWayback Machine,Honywell:Model JTF, General Purpose Accelerometer - ^"Pulling G's".Go Flight Medicine.5 April 2013.Archivedfrom the original on 12 January 2021.Retrieved24 September2014.
- ^Robert V. Brulle (2008).Engineering the Space Age: A Rocket Scientist Remembers(PDF).Air University Press. p. 135.ISBN978-1-58566-184-8.Archived fromthe original(PDF)on 4 January 2017.Retrieved8 January2020.
- ^Balldin, Ulf I. (2002)."Chapter 33: Acceleration effects on fighter pilots.".In Lounsbury, Dave E. (ed.).Medical conditions of Harsh Environments.Vol. 2. Washington, DC: Office of The Surgeon General, Department of the Army, United States of America.ISBN9780160510717.OCLC49322507.Archived fromthe original(PDF)on 6 August 2013.Retrieved16 September2013.
- ^abGeorge Bibel.Beyond the Black Box: the Forensics of Airplane Crashes.Johns Hopkins University Press, 2008.ISBN0-8018-8631-7.
- ^Burton RR (1988). "G-induced loss of consciousness: definition, history, current status".Aviation, Space, and Environmental Medicine.59(1):2–5.PMID3281645.
- ^Brown, Robert G (1999).On the edge: Personal flying experiences during the Second World War.GeneralStore PublishingHouse.ISBN978-1-896182-87-2.
- ^DeHart, Roy L. (2002).Fundamentals of Aerospace Medicine: 3rd Edition.Lippincott Williams & Wilkins.
- ^"NASA Physiological Acceleration Systems".20 May 2008. Archived fromthe originalon 20 May 2008.Retrieved25 December2012.
- ^NASA Technical note D-337, Centrifuge Study of Pilot Tolerance to Acceleration and the Effects of Acceleration on Pilot PerformanceArchived17 February 2022 at theWayback Machine,by Brent Y. Creer, Captain Harald A. Smedal, USN (MC), and Rodney C. Wingrove, figure 10
- ^NASA Technical note D-337, Centrifuge Study of Pilot Tolerance to Acceleration and the Effects of Acceleration on Pilot PerformanceArchived17 February 2022 at theWayback Machine,by Brent Y. Creer, Captain Harald A. Smedal, USN (MC), and Rodney C. Vtlfngrove
- ^Fastest Man on Earth – John Paul StappArchived15 December 2017 at theWayback Machine.Ejection Site. Retrieved on 14 October 2011.
- ^Martin, Douglas (16 November 1999)."John Paul Stapp, 89, Is Dead; 'The Fastest Man on Earth'".The New York Times.Archivedfrom the original on 3 September 2023.Retrieved29 October2016.
- ^"New details from horror crash".News.au.16 October 2014.Archivedfrom the original on 1 December 2017.Retrieved30 December2017.
- ^"Q&A: Kenny Brack".Crash.net.13 October 2004.Retrieved30 December2017.
- ^de Souza, T.A.J.; et al. (2017). "Survival potential of the anhydrobiotic nematodePanagrolaimus superbussubmitted to extreme abiotic stresses. ISJ-Invertebrate Survival Journal ".Invertebrate Survival Journal.14(1):85–93.doi:10.25431/1824-307X/isj.v14i1.85-93.
- ^de Souza, T.A.J.; et al. (2018). "Caenorhabditis elegansTolerates Hyperaccelerations up to 400,000 x g. Astrobiology ".Astrobiology.18(7):825–833.doi:10.1089/ast.2017.1802.PMID29746159.S2CID13679378.
- ^Than, Ker (25 April 2011)."Bacteria Grow Under 400,000 Times Earth's Gravity".National Geographic- Daily News.National Geographic Society. Archived fromthe originalon 27 April 2011.Retrieved28 April2011.
- ^Deguchi, Shigeru; Hirokazu Shimoshige; Mikiko Tsudome; Sada-atsu Mukai; Robert W. Corkery; Susumu Ito; Koki Horikoshi (2011)."Microbial growth at hyperaccelerations up to 403,627 ×g".Proceedings of the National Academy of Sciences.108(19):7997–8002.Bibcode:2011PNAS..108.7997D.doi:10.1073/pnas.1018027108.PMC3093466.PMID21518884.
- ^Stanford University:Gravity Probe B, Payload & SpacecraftArchivedOctober 13, 2014, at theWayback Machine,and NASA:Investigation of Drag-Free Control Technology for Earth Science Constellation Missions.The TRIAD 1 satellite was a later, more advanced navigation satellite that was part of the U.S. Navy'sTransit,or NAVSAT system.
- ^"Toyota Sienna 0–60 Times and Quarter Mile".autofiles.Archivedfrom the original on 2 November 2023.Retrieved11 September2023.
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- ^(rpm·π/30)2·0.072/g
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- ^(7 TeV/(20 minutes·c))/proton mass
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- ^(42geV/85 cm)/electron mass
Further reading
edit- Faller, James E. (November–December 2005)."The Measurement of Little g: A Fertile Ground for Precision Measurement Science".Journal of Research of the National Institute of Standards and Technology.110(6):559–581.doi:10.6028/jres.110.082.PMC4846227.PMID27308179.
External links
edit- "How Many Gs Can a Flyer Take?",October 1944,Popular Science—one of the first detailed public articles explaining this subject
- Enduring a human centrifuge at the NASA Ames Research CenteratWired
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- HUMAN CAPABILITIES IN THE PRONE AND SUPINE POSITIONS. AN ANNOTATED BIBLIOGRAPHY