No you are not. You are travelling at the speed of the Earth’s rotation (from an outside reference frame of course), not Geosynchronous speed. Geosynchronous orbit means an object takes 24 hours to orbit Earth, matching it’s rotation and appearing stationary with respect to a point on the ground. The speed required to do that at Geosynchronous orbit altitude is far higher. It’s not the same thing as the Earth’s rotational speed.
Please explain the difference.
Look back at my coins on a record analogy. Put a coin near the center of a spinning record and a coin near the edge. Both move the same number of degrees per rotation. But the outer coin has to be moving faster to do that. One rotation at Earth’s surface is 1,670 km/h. One rotation at geosynchronous orbit is 11,000 km/h.
Fair enough. Just falling straight down from the altitude of 400 km would result in a speed at the point that the body would encounter significant atmosphere (250 kft or 7.6 km) so the velocity, which gives a speed of about 2.5 km/sec. By the time it gets down to atmosphere dense enough to generate sufficient drag to actually create a terminal speed (150 kft or about 4.6 km) it will be moving 2.7 km/sec (not accounting for drag). At those speeds in atmosphere, anything that isn’t a solid chunk of metal, profiled like a bullet, more made from a thermally refractory material will rapidly get to melting or combustion temperatures. This doesn’t assure that no part of it will reach the ground but it won’t be anything like intact once it hits the denser part of the atmosphere if it hasn’t already started to break up.
Something that should be understood is that while people often speak of debris reentering the atmosphere as ‘burning up’ or ‘vaporizing’ as if being reduced to component atoms or molecules but that isn’t generally what happens to solid materials. An object entering the atmosphere experiences ionization and ablation in the free molecular region (mesosphere) followed by radiative heating and thermal shock in the upper stratosphere, and then aeroelastic buffeting and aeromechanical shock. All of this creates stresses in the material that generally causes most objects to break up into much smaller fragments and then erode or evaporate down to dust or aerosols long before they reach ground level. Although we build ‘break up models’ that estimate what a launch vehicle or spacecraft debris pattern will look in an effort to accurately estimate the expectation of casualty from a reentry, sometimes objects don’t fragment as expected or break down and make it all the way to the surface.
When you are in the surface you are not in orbit. If the surface of the Earth suddenly became permeable to human beings, you would fall right down through it because you are going way too slow at that altitude to be in a stable orbit. Staying in orbit is the art of falling fast enough that you fall above the horizon, and for the Earth’s mass to match the speed of rotation at the equator you have to be at geostationary orbit (GEO), which is 786 km (22,236 mi) and through the plane of the equator.
Stranger
But what speed relative to the upper atmosphere which is moving at a different rate than the ground is?
So entering at ISS speed that horizontal velocity is significant and it is in it for a long time, the question Stranger answered if I understand enough (not a sure thing).
Entering at geosynchronous speed that horizontal factor relative to the atmosphere at that level? Not so much if I understand your answer.
I’m thinking the Baumgartner example answers the question.
And… there’s my Doh! moment again. The earth is 4000 miles radius, not 4,000 km. So my Space Elevator calculation is off by a factor of 1.6 or so.
A geosync orbit is a very specific thing. It is the orbital altitude where the time it takes to make an orbit around the earth happens to match the Earth’s rotational period - 24 hours. The rocket scientist guys call this “remaining in sync with the Earth’s sidereal day”. At that altitude (around 36,000km) you need to be travelling at around 11,000 kph. Darren_Garrison’s coins at various positions on spinning record analogy is a good way of picturing it.
And one rotation at ground level willl be achieved at the speed of the ground where your chair stands. RitterSport never spoke about orbit, he spoke of speed at ground level. But why am I arguing for him, when you are misunderstanding him?
Yeah, but it takes me one day to travel all 360 degrees as well. I know that I would have to move much, much (much!) faster to orbit the earth at my altitude (a few hundred feet above sea level), but my speed is definitely synchronized with the earth.
I’m not misunderstanding anyone. You are the one that appears to be confused.
Color me confused, too.
Somebody here is not reading what the others write with the necessary attention. I will not insist.
Yes, that is apparent. But it isn’t me.
My cut & paste got truncated; the highlighted passage should read:
… which is 35,786 km (22,236 mi) …
Stranger
Something in a space elevator at any height will be circling the earth once/day. If it’s at Geo orbit, it will feel no gravity, but at LEO, it will feel about 90% of gravity. That’s what I meant by geosynchronous speed – the speed is synchronized with the earth, but the body is not in orbit. That speed will vary with height and latitude.
It’s a fair criticism to say that using the term “geosynchronous speed” is confusing, because it could be interpreted as “the speed needed to stay in orbit,” I suppose.
Okay, I see where the confusion lies with this now. Throughout the thread we have been touching on a very specific, well-defined thing: geosynchronous orbit. That is a specific speed at a specific distance. But in saying “hey, I’m geosynchronous, too” you were doing a play on words by being extremely literal about the word “geosynchronous” meaning you were staying in the same relative spot, apparently with an intent of being funny. But that makes communication harder when everybody else is using the scientific term of art, so of course when you said you were moving at geosynchronous speed, people thought you meant that you were traveling at the speed if an object in geosynchronous orbit.
I didn’t. See five posts prior.
I don’t think we were talking about orbital speeds throughout – the space elevator at LEO height mentioned in the OP isn’t orbital speed, but is rotating once per day.
If you stand near the ground and drop something, not much will happen to it. It may not even break.
If you are near the ground and release an object at orbital velocity, it will be moving hypersonically fast and subject to drag, skin friction, air compression, etc. and get all fucked up.
Yeah, for sure. Seems like a fun thing for What-If – slower than a relativistic baseball, but still ridiculously fast at ground level.
So, part of the question in the OP is “If you stand at LEO (circling the Earth once/day like a space elevator would, rather than every 90 minutes like an object in orbit does) and drop something, do we have to worry about it burning up?”, and the answer seems to be no, not even close.