Linked Questions

2 votes
7 answers
1k 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 ...
user avatar
9 votes
4 answers
2k views

Why has Vanguard 1 not decayed significantly since its orbital injection in 1958?

Vanguard 1 became the first satellite to use solar panels as a power source in 1958, when it was launched into an orbit with the following parameters: 654 by 3,969 kilometres (406 mi × 2,466 mi), ...
marked-down's user avatar
  • 8,931
13 votes
3 answers
1k views

Why are Tiangong-1's Apogee and Perigee Graphs Wobbly?

The apogee and perigee graph of the Tiangong-1 space station, about to re-enter and break up Real Soon Now, is depicted in this graph (source: Wikipedia): Why are the graphs wobbly? Is it because the ...
Jens's user avatar
  • 1,706
6 votes
3 answers
4k 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 ...
Mike Weber's user avatar
7 votes
2 answers
1k views

Physical meaning of perigee advance

I'm starting to study orbital perturbations and I can't find any physical explanation about the perigee advance (apsidal precession) when considering Earth oblateness effects. Can someone give a ...
Julio's user avatar
  • 1,772
8 votes
0 answers
3k views

For the mathematical relationship between J2 (km^5/s^2) and dimensionless J2 - which one is derived from the other?

The term $J_2$ seen in discussions of nodal precession of orbits (e.g. sun-synchronous) appears to come in two flavors. For example, in the Wikipedia article Geopotential model it has a value of $1....
uhoh's user avatar
  • 149k
3 votes
2 answers
308 views

Any exact analytical solutions for non-Keplerian orbits; those around non-radially symmetric mass distributions (e.g. J₂≠0)?

Keplerian orbits, those around spherically symmetric mass distributions (Newton's Shell theorem collapses them to a point) have analytical solutions in that you can write $t(\theta)$ as a simple ...
uhoh's user avatar
  • 149k
1 vote
1 answer
264 views

Is the formula for nodal period of a near-Earth satellite given by Wikipedia correct?

Wikipedia has a formula for the nodal period of a near-Earth satellite, taking into account the oblateness of the Earth (J2), and neglecting other effects (https://en.wikipedia.org/wiki/Nodal_period)....
Ng Ph's user avatar
  • 2,724
2 votes
1 answer
257 views

What delta-v per orbit would a spacecraft need to hover next to Saturn's rings?

In order to collect Saturn's ring particles for sample return to Earth, a spacecraft would need to share the orbit of this debris. If it is inclined it will have to pass through the rings twice each ...
LocalFluff's user avatar
4 votes
1 answer
204 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:...
Jon17's user avatar
  • 41
5 votes
1 answer
118 views

What is the simplest way to determine if two or more TLEs describe two or more satellites in lead-follow?

If two more more up to date TLEs have same inclination and the same period they are in the same orbit, but how do I check if they are also following each others path, in a train?
justin's user avatar
  • 53