Some Notable Velocities

Last modified: 2010.03.12.Fri. The current version of this document is available at http://www.Thistlehaven.net/J3. Direct comments and/or questions to j3@pobox.com.

Why “Mics” than Machs?

The velocities of interest that gave birth to this diagram – of scramjet engines, of the Shuttle, of asteroids impacting the Earth – were generally expressed as Mach numbers. The trouble with the Mach number, however useful it is in aerodynamics, is that it is not a fixed velocity. Rather, it varies according to the medium in which the velocity is taking place – subject to changes of material, temperature, humidity, pressure, etc. It’s wonderful for expressing aerodynamic points of interest, but a little soft for a diagram like this.

As it turns out, however, a millionth of the speed of light is actually quite close to the Mach values generally used, and is much more constant for expressing a wide range of velocities. Thus the diagram below uses units of one-millionth of the speed of light (or “mics”, as in “millionths of c”).

Some Notable Velocities

Some velocities of special note are highlighted in the diagram below (click the diagram to open a page-sized PDF of the diagram):

References

· Speed of light: exactly 299,792,458 m/sec, or exactly 186,282.397,051,221 mi/sec, or exactly 1,000,000 mics; see http://en.wikipedia.org/wiki/Speed_of_light

· Special relativistic time/length doubled/halved: 866,025 mics or 86.6% of the speed of light; see http://www.cthreepo.com/lab/math1.shtml, http://en.wikipedia.org/wiki/Time_dilation, http://en.wikipedia.org/wiki/Length_contraction

· Supernova shock wave: 360 million mph or 536,819 mics; see Astronomy magazine, 2009.03, p51, Q&A page

· Escape velocity of the Sun: 617.5 km/sec or 2059.8 mics; see http://www.daviddarling.info/encyclopedia/S/Sun.html; also see http://en.wikipedia.org/wiki/Escape_velocity

· Local Cluster toward the Great Attractor: 1,300,000 mph or 1938.5 mics; see Science Illustrated magazine, 2008.03-04, p30

· Sun around galaxy: 220 km/sec or 492,098 mph or 733.8 mics; see http://www.atlasoftheuniverse.com/milkyway.html

· Speed of Andromeda-Milky Way approach: 120 km/sec or 268,432 mph or 400.3 mics; see New Scientist magazine, 2007.05.19, p10, Goodbye Milky Way Hello Andromeda

· Escape velocity of Jupiter: 60 km/sec or 200.1 mics; see http://dml.cmnh.org/1994Aug/msg00157.html

· Escape velocity of Saturn: 35.5 km/sec or 118.4 mics; see http://wiki.answers.com/Q/What%20is%20the%20escape%20velocity%20of%20saturn

· Speed of Earth around Sun: 29.8 km/sec or 66,659 mph or 99.4 mics; see http://www.windows.ucar.edu/tour/link=/kids_space/vel.html

· Speed of New Horizons spacecraft: 52,000 mph or 77.5 mics; per series Known Universe, episode "The Fastest" on National Geographic Channel

· Speed of rings about Saturn: 40,000 mph or 59.6 mics; see Astronomy Magazine DVD episode "Saturn King of the Rings"

· Voyager 1 as it leaves the Solar System: 17.46 km/sec or 58.2 mics; see http://hypertextbook.com/facts/1997/PatricePean.shtml (in turn based on JPL numbers)

· Voyager 2 as it leaves the Solar System: 16.08 km/sec or 53.6 mics; see http://hypertextbook.com/facts/1997/PatricePean.shtml (in turn based on JPL numbers)

· Asteroids entering the atmosphere: 30,440 to 45,660 mph, or 8.4 to 12.6 mi/sec, or about Mach 40 to 60, or 45.4 to 68.1 mics; see New Scientist magazine, 2007.12.22, p10, "It's the little ones"

· Escape velocity of Earth: 24,957 mph or 6.93 mi/sec or 36,604 ft/sec, or 11_180 m/sec, or 37.3 mics; see http://www.math.nus.edu.sg/~bao/teach/ma3264/lect15.ppt

· Space shuttle re-entry at altitude 120 km: Mach 25 or 8.2 km/sec or 29,520 kph or 27.4 mics; see http://en.wikipedia.org/wiki/Space_Shuttle

· Orbital velocity of International Space Station (ISS) at altitude 380 km: 7.68 km/sec or 27,650 km/hr or 17,180 mph or 25.6 mics; see http://en.wikipedia.org/wiki/Space_Shuttle

· Theoretical limit of scramjet engines: Mach 15 or about 14.9 mics; see Popular Science magazine, 2008.01, p37, "The Hypersonic Age is Near" by Michael Belfiore

· Escape velocity of the Moon: 2375 m/sec or about 2.4 km/sec or about 9000 kph or about 5400 mph or 7.9 mics; see http://www.math.nus.edu.sg/~bao/teach/ma3264/lect15.ppt and http://www.johnderbyshire.com/Miscellaneous/singularity.html

· X-1 scramjet engine: Mach 6.5 or about 6.4 mics; per Popular Science magazine, 2008.01, p37, "The Hypersonic Age is Near" by Michael Belfiore

· Escape velocity of Pluto: 1.2 km/sec or 4.0 mics; see http://wiki.answers.com/Q/What%20is%20the%20escape%20velocity%20of%20pluto

· Moon's orbital velocity: 1.023 km/sec or 3.4 mics; see http://en.wikipedia.org/wiki/Orbit_of_the_Moon

· M16 muzzle velocity: 980 m/sec or 3.3 mics; see http://en.wikipedia.org/wiki/M16_rifle

· Speed record of SR-71: 2070.101 mph or about Mach 3.3 or 3.1 mics; see http://www.wvi.com/~sr71webmaster/srrcd~1.htm

· Speed of Concorde: Mach 2.02 or 2140 km/hr or 1330 mph or 1.98 mics; see http://en.wikipedia.org/wiki/Concorde

· Earth rotation at equator: 465.11 m/sec or 1040.4 mph or 1.6 mics; see http://www.answerbag.com/q_view/361596

· Fastest fighter jets: Mach 1.6 or about 1067 mph or 1.2 mics; see Popular Science magazine, 2008.01, p37, "The Hypersonic Age is Near" by Michael Belfiore

· Speed of sound in dry air at sea level at 20degC/68degF: 1125.79 ft/sec or 767.58 mph or 343.14 m/sec or 1235.30 kph or 1.1 mics; see http://en.wikipedia.org/wiki/Speed_of_sound

· Mach 1 as used to report airplane speeds: 516.667 to 658.419 to 667.059 mph, or 831.495 to 1059.406 to 1074.118 kph, or 0.779-0.982-0.995 mics

· Speed of 747: Mach 0.85 or 567 mph or 913 km/hr or 0.845 mics; see http://en.wikipedia.org/wiki/Boeing_747