# Tag Info

112

I believe the discovery was made by orbiting satellite, but I'm not sure which one. That is not the case. Look at the author affiliation for the article to which you linked. The three authors of that paper were from the British Antarctic Survey. These scientists were part of a larger expedition to Antarctica. They pointed a cheap instrument (extremely cheap ...

39

Not much research has been done on this question in recent years, but some researchers are worried enough to research into wooden satellites. The question on the environmental impact of deorbiting satellites burning up in the upper atmosphere was partly addressed in a 1994 report (warning: not peer reviewed) by the Environmental Management of the Space & ...

32

The mass of Earth's atmosphere is 5E+18 kg and the Troposphere alone has 3/4's of that. With an average height of 13 km that makes its volume $4 \pi r^2 h$ or about 6.6E+18 m^3. If we break up one thousand 100 kg satellites into semi-porous PM2.5 particles that works out to be 1.5E-08 micrograms per cubic meter, and we generally worry about tens of ...

26

No, unless your structure is located directly on the equator and your satellite follows a perfectly circular orbit, atmospheric "orbits" aren't possible, even in a vacuum tunnel. Because the Earth is on an axis of ~23 degrees and rotates every day, it is not possible to create an orbit which has no ground track precession except for equatorial ...

25

Short answer: Yes. Mars is not windy enough to properly wave most flags. Long answer: In storm conditions, a flag constructed out of a very light material would be able to properly wave. If we take a standard flag, say 3'x5' that's made of 200g Nylon $\ell= 1.5$ meters $h_f = 0.9$ meters $W = A * 0.2 * g_{Mars}$, $W = 1$ Newton Going off the calculations ...

19

Certainly a reasonable question. A possibly useful mental model is to spin a bucket of water in some form. Initially only the surface layers will spin but each layer transfers motion to the next layer in and eventually the entity of the mass is spinning in a steady state. Similarly with the atmosphere over geologic time scales the atmosphere is spinning with ...

16

In order to achieve "weightlessness", you don't need to achieve a certain speed, you need to achieve a certain acceleration. Earth pulls down at approximately 9.8 m/s^2 which means that any object falling gets faster by 9.8 m/s for every second that it falls. For example, a ball that falls from a tower (disregarding air resistance) and takes three seconds to ...

16

Such a tunnel is not plausible for a number of reasons. 1. Problems with orbits First of all, as other people have said it would only work for equatorial orbits which were either circular (very long tunnel) or had a period which is some rational multiple of the Earth's rotational period. And, again as other people have said, the real Earth is nothing like ...

15

To quickly summarise the answer: Nimbus 7 was the satellite involved - but it wasn't first. The ozone hole did not substantially materialise before the early-1980s - in retrospect the decline was visible, as this graph shows, but the catastrophic drop hadn't happened yet. Nimbus 7 was the first satellite (I think?) to carry an ozone spectrophotometer, which ...

14

The lower atmosphere must rotate with the earth because of friction---at least the very bottom of it. That is true, but only at the very, very bottom of the Earth's atmosphere, perhaps the last few millimeters. There are winds, after all. The trade winds and the prevailing westerlies (along with the discovery of how to beat against the wind) resulted in the ...

13

From the recently published paper Phosphine gas in the cloud decks of Venus. The presence of PH3 implies an atmospheric, surface or subsurface source of phosphorus, or delivery from interplanetary space. The only measured values of atmospheric phosphorus on Venus come from Vega descent probes, which were only sensitive to phosphorus as an element, so its ...

12

The earliest mention of the northern lights that I was able to find is the memories of the Voskhod-1 crew. «Наибольшее впечатление на всех нас произвело полярное сияние, которое нам удалось наблюдать в районе Антарктиды за несколько минут перед выходом из тени. Картина была такая: горизонт, затем тёмное небо, затем верхний слой яркости, подсвеченной луной, ...

11

Entering the atmosphere introduces drag, which could only reduce your energy. That is, reduce your speed relative to the planet. If you hit the atmosphere at 18,000 mph at too shallow an angle you could bounce off, but not with more energy than you had on approach. You'll fall back, but your landing point may then be outside of your control. You may be ...

11

Your premise is incorrect. In no case does "skipping off the atmosphere" leave you going faster than you arrived, engines on or not.

9

It's not so much a matter of speed but one of altitude: where the atmospheric pressure is low enough that there's no air drag so one can longer be weightless without any air limitation. Basically the altitude where there's a low enough air drag so your parabola can be of any size and where you don't necessarily have to immediately fall onto the Earth. This ...

9

The ion propulsion was run continuously to compensate for drag immediately. The drag force varied strongly during each orbit (i.e. changing from night to day), typically between 4 and 12 mN on its 1 m² surface. Absolutely not. The drag coefficient was about 10 times higher. The low $c_W$ that can be reached in a dense atmosphere mostly comes from flow ...

8

This would be a tunnel a couple thousand kilometers long, that extends from the surface of the Earth to approximately low earth orbit altitude at both ends, strong enough to keep vacuum inside and the atmosphere out at sea level, such that its openings are in place for a space station in a highly-elliptical geosynchronous orbit comes flying through at about ...

8

The partial pressure of oxygen (ppO2) should be higher than about 0.16 bar and lower than about 0.4 to 0.5 bar for longer exposition of some days up to a week. So breathing pure oxygen for a week is possible when the total pressure is not above 0.4 bar. See also my answer to the question How long were the Apollo astronauts allowed to breathe 100% oxygen at ...

6

In addition to solar radiation/wind, cosmic radiation. Regarding surface conditions (soil) you will need consider: Potential nutients for plants as well as toxins for plants, humans and other animals – see perchlorates on Mars. Abrasiveness of soils and the fineness of soil particles – see the issues for the Apollo moon missions. Any abrasive particles in ...

6

No, it would float lower if anything. To see this think about the forces on the balloon: the acceleration due to gravity is $g$ and I assume this is constant (the planet is large, the balloon isn't getting very far up: this is a good assumption); the density of the gas inside the balloon is $\rho_H$, the density of the atmosphere is $\rho_A$. If the '...

6

High-altitude ballooning is kind of a gray area as far as space exploration goes, because they can't leave the atmosphere, but they do go high enough to experience space-like conditions (e.g. the pressure is blood-boiling low, and it's darn hot on the sunlit side and cold on the shaded side). Balloon experiments measure things that you might normally ...

6

Roughly how much lower was GOCE's drag compared to a typical spacecraft, or to a sphere of the same mass. Did it have a drag coefficient as low as a real Ferrari? GOCE's drag coefficient was higher than that of a typical spacecraft. From Geul, J., E. Mooij, and R. Noomen. "GOCE statistical re-entry predictions." Proceedings of 7th European ...

5

The original spy satellites used film cameras. They were pressurized with a half atmosphere of nitrogen. What’s really interesting is that they didn’t need to be, according to the manufacturer. This predates the Mercury program, so I get the sense this was tacked on to the earliest space program to prepare for “Man in Space” The interior of the spacecraft ...

5

It would move Down! By the definition of the Karman line on wikipedia, the lift force and the "centrifugal force" must be equal to the gravitational force and, therefore, each other. This gives the following equation: $\frac{1}{2}\rho v^2C_LS = \frac{v^2m}{R_e+h}$ Where $\rho$ is density, v is velocity, $C_L$ is lift coefficient, S is wing area, m is ...

5

Tl, dr: With some care, high surface winds can be avoided. They seem to occur only once per fifteen years or so as Titan is in equinox. If we avoid the storms, which would likely be done anyway to simplify landing the craft and taking off again, surface winds will not be a problem at all. From Wikipedia: Surface winds are normally low (<1 meter per ...

5

According to an article by Geoffrey Landis (http://www.geoffreylandis.com/moonair.html), oxygen and nitrogen are removed from the Moon within about 100 days, due to the combined effects of sunlight and the solar wind. However, if the atmosphere is thick enough, then this effect would no longer occur.* In this case, the gases would last for thousands of years....

5

What you are looking for is scale height--the distance required to reduce atmospheric pressure to 1/e of what it was. Mars has a scale height of 11.1km with an atmosphere of 95% CO2. I'll assume it's all CO2. Your perfluorobutane has a density 5.6x as high. Scale height is linear on molecular weight, thus in the crater the scale height is 1.98 km. Thus ...

5

Obviously, @Digger can provide a first-hand crew experience answer, but in general no. Atomic oxygen (commonly called just AO) is a designer's problem that manifests primarily in the restriction of materials that are used on the exterior of the vehicle. This is a much bigger deal on ISS than it was on Shuttle. In general the erosion rate for most ...

5

Let's try to make some quick and dirty estimation for the upper limit in the case of Earth. (And in the end figure out that we have an actual measurement of this...) First, the bending power of the atmospheric lens. It's not uniform as @uhoh mentioned in his answer. But, for rays passing just above surface we can get a accurate number. During sunset ...

4

No, I don't think so. As you say, the pressure is highest in Io's volcanic plumes at 40 nanobar (4 millipa) at most. That's equivalent to the pressure about 115 km (72 mi) above the Earth's sea level. At 120 km / 75 mi the atmospheric drag becomes more significant but it doesn't cause a re-entering craft to glow, so you're wrong unless the craft is going at ...

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