# Linked Questions

7answers
774 views

### What does it take for a craft to perform a flight simulating weightlessness without having to fly a steep parabola/ellipse?

Alright, I'll try to ask a better question on what I mean so that we figure out how one becomes weightless in a craft without having to fly steep parabolae. Other than flying parabolae or nose-down ...
3answers
11k views

### How fast do Starlink satellites (SpaceX new satellites) rotate around the earth?

I'm specifically interested in knowing how long they take to do a full circle around the earth but don't find any info. Could anyone help me?
3answers
2k views

### Determine orbit type from TLE

I was wondering if, and how, one can tell from the values in a TLE whether an orbit is LEO, MEO, HEO, or GEO. I'd like to do this in code eventually, so any formulas or threshold values would be much ...
2answers
1k views

### Can the Right Ascension and Argument of Perigee of a spacecraft's orbit keep varying by themselves with time?

I came across the orbital data for a low Earth orbit spacecraft and one thing which I am not able to understand is why does its Right Ascension of ascending node and Argument of Perigee keep changing ...
2answers
4k views

### In "spacecraft talk" is nadir just a fancy word for "down"?

Assume the approximation that the Earth is spherically symmetric — without higher order gravitational multipoles, and other effects that might be related to gravity from other bodies or the ...
2answers
479 views

### What is the reason for secondary oscillations in apogee and perigee plots for objects 41332 and 41333?

This answer provides quite interesting plots of apogee and perigee for objects 41332 and 41333. The primary (sine wave -like) oscillations are probably due to perturbations caused by potential ...
2answers
540 views

### Did Tiangong-1 turn the engines on?

The following graph shows the Tiangong-1 radius vector at the perigee, semi-major axis and apogee (scaled to 6371 km just to show an approximate altitude) and its orbit eccentricity: I used the SGP4 ...
2answers
1k views

### Help understanding negative apogee coinciding with exact center of Earth (Mars InSight launch)

Watching the NASA JPL video NASA Launches InSight to Mars (Part 2) after MECO-2, the orbital parameters shown in the video don't make sense to me; specifically the apogee altitude. At this point in ...
2answers
116 views

### How big is an orbit of "X by Y miles"?

While reading the NASA overview of Apollo 11, says: Apollo 11 launched from Cape Kennedy on July 16, 1969, carrying Commander Neil Armstrong, Command Module Pilot Michael Collins and Lunar Module ...
2answers
712 views

### What is the Fischer 1960 Mercury Ellipsoid, and why is it called that?

Don't be distracted by the 1960 Mercury shown below. Reading about Irene Fischer (also here, and mentioned in this answer) and seeing the Fischer 1960 Mercury Ellipsoid turn up in tables of ellipsoid ...
1answer
532 views

### Which satellite constellations are already operational in LEO (Low Earth Orbit)?

I am researching information on active and operational constellations in LEO (Low Earth Orbit) but from what I can see, many missions are still only planned (e.g. OneWeb, Amazon) and the only one ...
1answer
294 views

### Deviation of semi-major axis

If I calculate the semi-major axis of Molniya-1T with $a = \sqrt[3]{\dfrac{GM}{n^2}}$ with $n=3.18683728\text{ }d^{-1}$, I get another apoapsis ($a=19505.7$ km) as noted at Heavens Above: apogee ...
1answer
110 views

### How to read stuffin.space data?

In a comment to this question, @PcMan suggested my stuffin.space for satellite data. Now I am not quite sure of how to interpret the data, take for example the following screenshot: Why is the ...
1answer
105 views

### Mechanics of Sun-Synchronous Orbit & North Korea's KMS-4

QUICK QUESTION: Is North Korea's KMS-4 in a proper Sun-synchronous orbit? https://www.n2yo.com/?s=41332 2016-009A FOLLOW-UP QUESTION: How do I tell? I want to understand the mechanics. RESEARCH:...
1answer
2k views

### Delta-V of Starlink Satellites

The recently launched Starlink satellites are designed to use their HAL Ion thrusters to seek their own independent orbits, evade collisions, and de-orbit at the end of their lives. That's a lot of ...
1answer
121 views

### What are the minimum and maximum calculated, published altitudes of the Kármán line?

I'd like to be able to say, "The Kármán line has been calculated to lie between ___ and ___ km." The "accepted" altitude of the ...
1answer
360 views

### How large would be the seasonal variation of eclipse duration for a spacecraft in LEO?

The question How long will a 500 km altitude satellite spend in Earth - shade per orbit has several answers, and there is some discussion of constraints related to maximum eclipse, due to some issues ...