30

By convention the altitude of a spacecraft is the distance to the center of the Earth minus roughly 6378 kilometers, or some reference radius that is representative of the equatorial radius of the Earth. Spacecraft altitude is not really used as a precise description of a satellite's position, since its only a scalar and it requires a definition, but if you ...


21

We are "in space", in fact everything that exists and has a physical presence is. But what we usually mean by it is to describe "outer space" conditions of near (or hard) vacuum, where atmospheric pressure is already low enough to affect matter differently than under true atmospheric conditions, for example at atmospheric pressure below triple point of water....


19

Altitude drops like that are common when the orbital stage has a high-efficiency, low-thrust engine. It takes a few minutes for the upper stage to bring the craft up to orbital speed. During that period, the craft is indeed starting to fall back towards Earth. The rocket's travel over the curvature of the Earth contributes an effective altitude gain that ...


13

Is there any particular deep areas of Mars in which a person could survive with only an oxygen supply without a pressurized suit? No. Hellas Planitia is the lowest point on Mars, the basin floor is about 7,152 m (23,465 ft) deep and the pressure is 1.16 kPa (0.168 psi). The average surface pressure of Mars is 0.6 kPa (0.087 psi). The highest point, Olympus ...


10

The furthest satellite that I have seen use GPS is the AO-40, an amateur built satellite. In fact, they did a research paper on the subject. The paper states that it was able to achieve a navigation solution at 60,000 km, which is about 1/6th of the way to the moon, and well beyond the belt of Geosynchronous satellites. I'm sure there are other satellites ...


10

The official NASA ISS Familiarization Manual (used in crew training) states on page 1-3: (emphasis mine) All of these IGAs, MOUs, SPIP volumes, and control centers are required to support a vehicle that, at Assembly Complete, is to be the largest man-made object ever to orbit the Earth. The ISS is to have • A pressurized volume of 1200 cubic ...


10

The altitudes are not what I would call ridiculous. Though you seem prone to using unjustified superlatives in your questions. The optimum, i.e. minimum injection velocity sub-orbit was provided by HopDavid in this answer. With some manipulation, you get that the maximum altitude of the optimal trajectory is: $${r\over 2}\left(\sin{\alpha\over 2}+\cos{\...


8

This really depends on your definition of astronaut. The Google definition is: a person who is trained to travel in a spacecraft. I'd suggest that the first person ever trained to travel in a spacecraft never actually flew. Again this depends on your definition of training though I suppose. However I fear this isn't the answer you're looking for. If you'...


8

While this question betrays a serious lack of understanding of physics, it's also a common lack of understanding, so I think it is in a way a good question. We are used to helium balloons floating up into the air, wood floating on the surface of water, and cannon balls sinking to the bottom of the sea. Intuitively, when we think of things "floating" in ...


8

We know that the tough part of getting to space isn't getting there, it's going fast enough to stay there. One of the key reasons is that the rocket is concentrating more on gaining horizontal speed than vertical height. So the rocket will eventually start being pulled down vertically. The atmosphere is such at that altitude that the rocket won't be ...


8

The first formula gives you the altitude at a particular point in the orbit, assuming that the position vector is the satellite's current position relative to the center of the Earth. The second formula is the altitude of the periapsis (lowest point) of an elliptical orbit.


7

To Or how deep would one have to be in Mars not to need a pressurized suit? and starting with @Rob's values and Planetery-Science.org's scale height of about 10.8 km to at least roughly ballpark an answer: altitude (km) pressure (kPa) -7.15 1.16 0. 0.6 25. 0.03 $$P(h) = P_0 \exp\left( -\frac{h-h_0}{h_{...


6

Concurrent with TildalWave's reply I too say 'Karman line'(100 kilometres (62 mi) above the Earth's sea level). Apart from the fact the K-line is legally so recognized an alternative definition of 'in space' is covered in the same Wikipedia article ... any vehicle at this altitude would have to travel faster than orbital velocity in order to derive ...


6

Yes, there have been changes of > 40 km, as shown in this graph. The X axis scale is not showing, but it is from Nov 1998 to July 2008. Reference Edit: I checked to make sure the graph is not just a theoretical math problem. It's not, the same graph appears here.


6

In orbital mechanics, the position of a satellite can be defined using orbital elements (which have some advantages over other coordinate systems, for typical orbits). Orbital elements describe a position in relation to the centre of mass of the Earth or any other body. For example, one of the orbital elements is the semimajor axis, which for a circular ...


6

Much, much higher specific orbital energy ($\epsilon$) and Dawn's lack of high impulse thrusters. OK, technically Dawn has 12 x off-axis 0.9 N RCS thrusters, but it only launched with 46 kg of hydrazine for them, so it pretty much depends on its three 90 mN ion thrusters alone. See this answer for more detailed explanation of its propulsive systems and ...


6

The driving factor for the ISS altitude is cheaper maintenance, and orbital debris mitigation. There is an optimal altitude for maintenance, which would actually be a bit higher than it is, because the ISS has to actively maintain its altitude by thrusting on a regular basis, while if it was higher that wouldn't be the case. Orbital debris is the primary ...


6

As TidalWave pointed out, no very small satellites have flown with an active propulsion system, so they cannot change their orbit actively. To control their attitude, many employ a Magnetorquer, which is a magnet, that creates an infinitesimal, but sufficient, torque in the earth's magnetic field. They may have small reaction wheel systems, which allow ...


6

The slowest you can have the asteroid enter Earth's atmosphere without active propulsion is LEO orbit velocity. It is indeed possible to have such an object enter the Earth-moon system, do a very close gravity assist flyby of the moon with an approach V∞ equal to the moon's orbit velocity around Earth (~1.02 km/s), and come to a dead stop with respect to ...


5

What you want to search for to get this information is 'launch sequence'. It depends on the rocket and the payload. What happens up to first stage separation is pretty standard, what happens with second stages is more variable. If the rocket has boosters (the thin cylinders that are strapped onto the sides), they will separate between 30 to 60 kilometers ...


5

Is an orbital launch more like a vertical climb or a Hohmann Transfer? This is a false dilemma. Neither is correct. Both of your calculations are wrong. Your vertical climb interpretation ignores that the velocity at the end of the launch needs to be horizontal and about 7.8 km/s. Your Hohmann transfer interpretation ignores that the velocity at the start ...


5

Blimey, that number surprised me since it only ever flew up to about 500 ft! Service ceiling is the maximum altitude (air pressure) at which an aircraft is designed to perform with expected stability that's constrained within its flight envelope: In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft refers to the ...


5

To contradict everyone else, the US Air Force used an altitude of 50 miles when awarding the Astronaut Badge to pilots of the X-15.


5

Earth is approximated as a point-mass when doing this calculation. The oblatness of the planet and different gravity potentials can then be computed using spherical harmonics or "mascon" (short for mass concentration). When designing special orbits, such as those around the Lagrange points, it isn't uncommon to define a new reference frame whose center is ...


5

Indeed it was originally based on radiation dose rates. Hank Garrett told me years ago that it was considered the altitude above which satellites in relatively low-inclination orbits had to take serious radiation hazard reduction measures. But that justification is obsolete, and was tenuous to begin with. Since the particles (especially electron and protons) ...


5

The following graphs show the ISS mean radius vector (or semi-major axis) minus 6371 km (just to show an approximate altitude) and the mean air density at the ISS position calculated with the NRLMSISE-00 atmosphere model updated with the solar and geomagnetic indices: ftp://ftp.agi.com/pub/DynamicEarthData/SpaceWeather-All-v1.2.txt. EDIT: the blue plot ...


4

The U.S. Department of Defense (DOD) 1960 World Geodetic System was produced by Irene Fischer and published in 1960. Today they are commonly known as 1960 Fisher Ellipsoids, as they are called today, is a mapping of the shape of the Earth, published by Irene Fischer in 1960. This was the best unclassified ellipsoid available at the time. As a result, NASA ...


4

Approach 4 (Succesfull approach) At this point in time, I am not able to pursue the analytical approach any further, so I found a satellite (debris) via http://stuffin.space/?intldes=2012-008N that had an orbit similar to the one I am trying to determine, wrote a small excel script that crawls the data from http://www.satview.org/forec.php?sat_id=43273U ...


4

Yes and no. No: The equations that govern the orbit of a satellite don't say anything about weight, so if you launch a heavy satellite and a light one to the same orbit, they'll stay together. Yes: In the equations that govern the launch of a satellite, weight is a variable. When you launch two identical rockets, one with a heavy payload and one with a ...


4

Initial obvious locations are various Lagrange points or lunar orbit. Many people have looked, thought about it, but nothing has been seriously funded for reasons of logistics. Until recently, access to orbit was very expensive, and large scale orbital construction even more so. The Shuttle, the primary launch vehicle for the United States for the last ...


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