Now, with Virgin Galactic seemingly on the cusp of launching paying passengers onto suborbital trajectories, many people are wondering whether those lucky space tourists will earn their astronaut wings. As of right now, they will, according to U. Is that a problem?
Here, we take a look at the ways space is currently defined, the confusion surrounding the demarcation, and what the future might bring. The laws governing air space and outer space are different; flying a satellite 55 miles above China is just fine if space begins at 50 miles up, but define the edge at 60 miles, and you might find your satellite being treated as an act of military aggression.
Broadly, most experts say that space starts at the point where orbital dynamic forces become more important than aerodynamic forces, or where the atmosphere alone is not enough to support a flying vessel at suborbital speeds. The Federation Aeronautique Internationale FAI , which keeps track of standards and records in astronautics and aeronautics, also defines space as beginning a hundred kilometers up.
It is, after all, a nice round number. But the Federal Aviation Administration, the U. A prodigious maker of lists, McDowell was compiling records for rockets, astronauts, and other space objects, and he went looking for an accepted international boundary that would help him decide which records to include. He pulled publicly available orbital paths for 43, satellites and sorted them based on the lowest points in their orbits called perigee during decommissioning and atmospheric re-entry.
From there, he realized that satellites could orbit the planet numerous times below an altitude of 62 miles, but those dipping beneath 50 miles met a quick and flaming end more often than not. As of now, yes, at least if they make the trip from a U. The FAA and the U. Air Force both agree that flying higher than 50 miles above our planet qualifies a person for the title.
See where active spaceports exist around the world. Some people might argue that getting into orbit is what defines an astronaut. Those are two different things. Here, the atmosphere becomes incredibly thin and starts to give way to the stronger, more violent solar winds of the sun. This way of defining space complicates things a bit, though. At that altitude the International Space Station orbiting between to miles up , the space shuttle which orbited miles up and some of NOAA's polar-orbiting satellites orbiting miles up would not be considered spacecraft!
In , researchers at the University of Calgary designed and launched the Supra-Thermal Ion Imager , an instrument developed to measure the transition between the relatively gentle winds of Earth's atmosphere and the more violent flows of charged particles in space.
According to their data, the edge of space begins at km 73 miles above sea level. Where is space? Until now, a simple nod to the sky may have sufficed, but it seems that with each passing year the final frontier is becoming a little more accessible. In today's world of potential commercial passenger space flights, missions to Mars and unimaginable technological advancements, outer space may be getting closer than we ever thought. With the threat of nuclear war looming, President Eisenhower and his advisers sought to ensure international acceptance of "freedom of space" for the unspoken use of reconnaissance satellites.
His interpretation of space treated it much like the high seas. Outside of national territorial airspace, nations were free to conduct peaceful space operations without concern for international borders. Temperature stops increasing and starts decreasing with altitude. Above 32 mi, air pressure drops below 0.
If you consider this or a lower altitude the space border, note that Yuri Gagarin wasn't the first man in space for you. The first man in space would be American pilot Joseph Walker who reached slightly more than 32 mi in the X on 30 March , a few days before Gagarin's spaceflight.
There it is so low that you can't hear anymore, there is no sound and one is essentially deaf above that altitude. Outside only, since sound would still travel through your spacecraft of course. Also above circa , ft the ionosphere begins. Balloon flight is no longer possible. The highest unmanned balloon reached an altitude of , ft 53 km and the highest manned one flown by Alan Eustace reached about , ft Above , ft you may become weightless in your spaceplane without having to push the yoke.
See this answer for clarification. The orbit didn't change much, it remained pretty stable. It is the mesopause mesosphere-thermosphere border : temperature stops decreasing and starts increasing again. It is defined as where you have to put more effort into rocket-powered flight rather than air buoyancy.
Astrodynamics take over from aerodynamics around that altitude. If you consider the space border here, you must add Pluto, Eris and Triton to celestial bodies that have a considerable atmosphere.
I suppose the Space Shuttle started to glow around that altitude too. I regain rudder control around that altitude.
While circular orbits are impossible at that altitude, an spacecraft in an elliptical orbit can attain a perigee at , ft and remain it quite stable. If you set the space border at this altitude or higher, you must include Io into the list of bodies with considerable atmospheres. Above circa that altitude the atmosphere becomes an exosphere which no longer behaves like gas. The molecules don't collide with each other and are dispersed away from Earth by solar wind, reaching escape velocity.
If you consider this the space border, you must include Callisto into the group of bodies with considerable atmospheres. You would also have to classify only the following flights as spaceflights: Gemini 10, Gemini 11, Apollo 8 and Apollo All other spaceflights wouldn't count as any. Above that altitude there's quite an absolute vacuum. If you consider this the space border, only Apollo 8 and Apollo would you have to count as spaceflights.
As for me, I consider , ft 61 km the space border. The least plausible to me are the one at km and the one at geostationary orbit, due to the reasons written above. Quoting Wikipedia :. But it is not where atmospheric weather phenomena ceases. Weather phenomena typically ceases in the thermosphere which reaches km above the Earth 18 km above equator , but stratospheric weather phenomena does exist, e. Not that any plane would attempt to fly horizontally in the upper mesosphere or above by propulsion and aerodynamic lift only.
Atmospheric composition with altitude 1. Atmospheric composition with altitude 2. As we can deduce from the diagrams, the change in atmospheric composition starts around 90 km 56 mi altitude which is called the turbopause or homopause, and identical with the mesopause; and the change essentially ends around km mi above which hydrogen and helium prevail.
Hence if you're strict you may state the Earth's atmosphere's definite end is at miles, beyond which there is outer space. However, this would mean there were only ten human spaceflights in history: Gemini 11, Apollo 8 and Apollo While this is an honor to America as it's the only nation that would ever have accomplished human spaceflight, textbooks and almost everyone consider Yuri Gagarin the first human in space, and the German V2 missile the first man-made object in space.
Yuri Gagarin's Vostok spacecraft reached an apogee of km mi. The previous altitude record for a human was So if you'd like to stick to the mainstream, the atmosphere-space border should be above 32 miles and no higher than miles.
But if you don't mind about mainstream teaching, you may consider the atmosphere-space boundary at any altitude from 84 km 52 mi to km mi , or perhaps you'd like to define it by entirely different factors. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
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