Questions tagged [astrodynamics]

The study of satellite orbits and space flight dynamics.

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106
votes
13answers
52k views

What are the choices today for orbital mechanics simulation software?

I used to be familiar with the various choices out there for orbital mechanics simulation software. Alas, those days are gone. What are the choices today, preferably sorted by platform? This ...
30
votes
3answers
5k views

Orbiting Earth before heading to Moon

Each of the lunar Apollo missions (Apollo 8-17) entered Earth orbit immediately after launch. Each mission then left Earth after a few orbits by burning the S-IVB engine, and headed off to the Moon. (...
2
votes
0answers
394 views

How to find Near Rectilinear Halo Orbits (NHROs)?

Looking all the good questions and answers in this site referent to CR3BP dynamics, periodic orbits, state transition matrices, etc. I wonder: what algorithm or steps do I have to follow to find the ...
11
votes
3answers
443 views

How is the trajectory of spacecraft transferring between planets monitored?

The doppler effect can give a pretty measure of radial speed relative to Earth, and radio transmissions can narrow down the radial position, but what about everything else? I can imagine several ways, ...
10
votes
1answer
600 views

What are the practical uses of a state transition matrix?

I am studying different dynamical models of relative motion of satellites. In my work, I've always just used a numerical integrator like RK78 to integrate the cartesian system of equations: $\dot{r}=...
16
votes
1answer
740 views

How important is plume impingement in rendezvous operations?

When performing space rendezvous operations close to the target vehicle (0-5 m relative distance), pursuer thruster escape nozzle gases can hit the target if firings are done in the direction of ...
5
votes
1answer
2k views

How to derive the polar form of the equations of motion?

As part of an optimal control problem (see linked problem), I need the polar form of the equations of motion (EOM) defining the orbit of a spacecraft. In e.g. Bryson and Ho (1969) and Vallado (2007) ...
6
votes
1answer
470 views

How to numerically solve an optimal thrust-vectoring problem?

This question is a follow-up to this question and is linked to this question, where if needed more details can be found on the parameters used in the following. For an in-plane non-impulsive orbital ...
6
votes
1answer
132 views

Calculation of V1 (orbital speed) during ascent

I am studying instrumentation of NASA's Orion spacecraft, and there is a readout for V1 (I am assuming this is the "first orbital velocity", for circular orbit), and it seems to be in small decimals. ...
3
votes
2answers
218 views

Spacecraft Horizon Sensors for Lunar orbit

Recall that "traditional" horizon sensors for Earth missions utilize the IR wavelength regime since this can reveal a good contrast between the cold space and the warm Earth-limb edge. If we were to ...
4
votes
1answer
185 views

Is the amount of accurate information in a TLE equal to that of a single state vector?

My question is basically regarding whether there is orbital information "lost" when converting from a Two Line Element set (TLE) to a state vector. Given that the following are true: I have a TLE, ...
2
votes
2answers
196 views

Is a solar free-return trajectory possible?

I'm coining a new phrase: "Dyson circuit". Is it possible, with current solar orbital capabilities (see Parker Solar Probe), to drive artificial satellites in a free-return trajectory around the Sun? ...
2
votes
1answer
106 views

If a spacecraft is orbiting around the Moon, what direction would the nadir axis be?

Nadir for a craft orbiting the Earth would be radially in, is nadir always pointed towards the Earth or is it pointed towards the celestial body that the craft is orbiting?
0
votes
2answers
191 views

How big a nuke would be needed to break Phobos out of orbit?

Phobos Radius: 11.267 km Orbital period: 8 hours Equatorial rotation velocity: 11.0 km/h (6.8 mph) (at longest axis) With an 8 hour orbit around Mars it must be going at a fair clip already which ...