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Zone36's avatar

If something is going slow enough, can it go through the earth's atmostphere?

Asked by Zone36 (408 points ) December 27th, 2009

When something is burning up in the atmosphere it is mainly due to friction I believe.

So if something were just going very slowly through the earth’s atmosphere would it be able to mostly survive intact. Say like one of those little army men with a big parachute.

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24 Answers

DrMC's avatar

LOL – you were too specific. I was going to say, my car goes slow enough not to catch fire. I think the metoers that are found are an example of things that make it to the ground.

I would bet that even starting from zero velocity at the begining of the gravity well, whatever the mass – you would still heat the surface enough to make plasma (fire)

Could you drop a parachute? – well I’m betting the gravity well goes out much farther than the atmosphere, and but the time you hit the atmosphere, the velocity would still generate plasma. This is pure guess – perhaps a physicist might be able to prove it mathematically.

Ivan's avatar

Walk to your refrigerator and back, tell me if you made it ok. We live in the atmosphere.

DrMC's avatar

Just looked it up – the gravity falls as the inverse square as you move away from earth. The gravity well is much much bigger a distance than the 20–30 mile drop example of the upper atmosphere in the video.

A good physics question. Bowling ball dropped from 1000 mi out. What would it’s velocity be at 30 mile out? – if its better than 10K – probably would produce plasma.

Likely not all stellar junk is cruising at 50k plus, but some examples could be in an orbit with the sun but might have low relative velocity with earth. Betting those are your shooting stars

ETpro's avatar

We must certainly hope so. Otherwise, all the astronauts who have gone outside earth’s atmosphere would either have to stay there or face self immolation on return.

Christian95's avatar

if you meant reentry into the atmosphere than no.Have you heard of something called gravity?.Well that thing is going to attract the body to earth and it will increase his speed until the friction will become big enough to burn it(if he isn’t protected with NASA materials)
If the body is light enough to not be attracted by Earth than he won’t have enough mass to beat the air resistance.

csimme01's avatar

Yes, and it doesn’t have to be moving that slow. On August 16, 1960, Colonel Joseph Kittinger jumped from a helium baloon at an altitude of 102,800 feet (31,300 m) or 19.46 miles (31.3 km). Towing a small drogue chute for initial stabilization, he fell for four minutes and 36 seconds, reaching a maximum speed of 614 mph. He set historical numbers for highest balloon ascent, highest parachute jump, longest drogue-fall (four minutes), and fastest speed by a human being through the atmosphere. He still holds these records today. He was literally a little army man with a big parachute. See Here for more information.

stranger_in_a_strange_land's avatar

Spacecraft reentering the atmosphere are using materials which either absorb the heat and slowly release it later (such as the “tiles” on the space shuttle) or use an ablative material where the heat is carried off by eroded surface material (as with the capsule-type vehicles). In reentry there is a substantial amount of frictional heat created before the atmosphere becomes dense enough for aerodynamic (parachute or wing) braking or maneuvering.

The only way that an object could come through the earths gravity well slowly would be by continuously opposing gravitational force. Not practical due to the large amount of fuel that would be required to accomplish this with a rocket.

csimme01's avatar

Here is a link to a video. There appears to be a few different takes on the speed reached. Some sources state his speed at greater than 700 MPH

ETpro's avatar

@csimme01

I tried an attraction once in Las Vegas that approximates free-falling through the dense part of earth’s atmosphere. The ‘ride’ is basically a giant, vertical wind tunnel. It has a DC-8 aircraft engine to generate an upward airstream moving 200 MPH. You jump out into this airstream assuming a posture like a sky diver and can literally float (or fly) on the upward rushing air. Having felt that, I don’t even want to think about going 700 MPH instead of 200.

daemonelson's avatar

Well, have you ever walked fast enough to spontaneously combust?

stranger_in_a_strange_land's avatar

I was trained as a HALO jumper (jumping ouy of an aircrat at 40.000 feet and free falling to under 2000 ft) as weapons officer with a SF team to delivered the SADM (Special Atomic Demolition Munition) in the late 1970s. A “backpack nuke” hand-delivered to a target inaccessable from the air. Basically a suicide mission if we had been called on to do it.

ETpro's avatar

@stranger_in_a_strange_land That makes the 200 MPH free fall sound like the decidedly safe part. Glad you were never required to put that skill to use.

csimme01's avatar

@ETpro According to the Video. Even tho he was falling faster than the speed of sound he had no feeling of falling at all.

CyanoticWasp's avatar

When you speak of something “going very slowly” through the Earth’s atmosphere, you’re talking about something with a more or less synchronized speed relative to Earth. So objects that take off from Earth, don’t go through the atmosphere into orbit, and then land again, would qualify. This is up to and including ICBMs (Inter Continental Ballistic Missiles, for those who grew up after the 60s and didn’t hear much about those.)

Most things entering the Earth’s atmosphere from orbit or from outer space don’t so qualify.

Keep in mind that the Earth moves in a giant circle around the Sun. That circle has a radius of 93 million miles (give or take), so the circumference of the circle is over half a billion miles (measured in Earth units). This means that each day the Earth travels 1,600,000 miles along that circle, or approximately 66,700 miles per hour. (Again, to keep this in comprehensible Earth units.)

So if your “little army man with a big parachute” weren’t already “inside” Earth’s atmosphere, but was either in another orbit of its own or somehow “stationary” in space, but in Earth’s path, then what would happen would be a literal “collision” of the orbits. And in that case, that “little army man with the big parachute” would likely not survive the “collision”. Since its speed relative to Earth’s at the time of the “collision” could be at a huge speed differential, then it would probably burn up, just like any meteorite.

What would more than likely happen is that as it approached Earth’s atmosphere it would be affected by and enveloped within Earth’s gravitational field and spun into orbit around this planet on its own, until its orbital speed decreased over time and it dropped into the thinnest atmosphere, slowed down more, and then began free fall.

Don’t forget that at the outer edges of Earth’s atmosphere there is no “air” to make a parachute very useful… just enough to create the friction that causes the burn. In any case, if it entered Earth’s orbit from “outside” the atmosphere, whether from a decaying orbit of its own or as some kind of projectile or “collision”, then it would burn up unless very special measures were taken to protect it.

@DrMC, your postulated 50k mph speeds aren’t so unrealistic after all.

ETpro's avatar

The estimated speed of the asteroid that hit the Yucatan Peninsula 65 million years ago was 400,000 miles an hour. The object was roughly the size of Mount Everest. That impact was so enormous it ended the age of the dinosaurs, causing abrupt, global climate and ecological change that doomed most reptiles and much of the plant life on earth.

DrMC's avatar

The 50K was fetched innaccurately from memery RE science channel about the above nasty meteor. It’s actually a good mathematical puzzle, so ease even a child prodigy could solve it ; )

csimme01's avatar

The minimum speed to achieve low earth orbit is approx 7,900 m/s (28,440.00 km/h; 17,671.80 mph) This is lateral velocity. When an orbiting object returns to earth it enters the atmosphere at slightly less than this speed. This has nothing to do with falling or the pull of gravity.

DrMC's avatar

There is a first year physics question using a second order equation. I remember using it back in the day, haven’t needed it since college (early 1980’s)

for simplicity sake you could make gravity constant at ½ G just to get a rough idea. Plug in the distance, and constant force, calculate the final speed after 1000 km acceleration.

If you were really tricky you could work out changing force too. I’m betting this is in standard use by astronomers, so it’s likely already been cooked up and just needs the numbers plugged in if you can find it.

Very likely anything accelerating that long, will vaporize as it hits the first wisps of atmosphere, unless shielded or massive or both.

Would be cool if you could reenter without massive energy expenditure. I wonder if there were some way to store the energy?

proXXi's avatar

Micrometeorites are floating to earth constantly.

The do not burn in the atmosphere.

jerv's avatar

@stranger_in_a_strange_land Orc-style terminally-guided munitions, eh? I can’t help but have Dr. Strangelove flashbacks thinking about that.

DrMC's avatar

I heard a rumor about iran during the hostage crisis, by someone in the military who “wasn’t there” about a shoulder launched device that “wasn’t there” Too bad about the plane crash.

engineeristerminatorisWOLV's avatar

Yes,It could.The friction is nothing but a resistive force that is a sort of Drag.More you oppose it in air with higher velocity, the more it increases.When things pass through the atmosphere at a controlled velocity,the chances of burning up are rare unless,it’s something flamable on reaction with other gases.

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