# Tag Info

Accepted

### How can we determine the most appropriate central body for orbit propagation?

Several years ago I had an intern investigate this very problem. A good intern task is an interesting but nonessential problem. This qualified as such; he even managed to turn that internship work as ...
• 66k

### Does the speed of ISS slow down at the time of a spacewalk or does it become stationary?

Let's look at Newton's first law: Law I: Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force ...
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### Orbiting Earth before heading to Moon

Going from Earth's surface direct to Moon orbit without stopping in LEO would offer negligible savings -- depending on your assumptions, maybe 20 m/s worth of ∆v (and 2-3 hours worth of consumables).1 ...
• 162k
Accepted

### How to choose the best direction to leave Earth's sphere of influence?

Your intuition is quite correct. The Hohmann transfer orbit is a bi-tangential orbit, so at the point where the spacecraft leaves Earth, it is travelling in parallel to us. In the case of Mars, we ...

### How does a Mars lander reach a chosen landing site?

There are typically five planned trajectory correction maneuvers on the way to Mars, referred to as TCM-1 to TCM-5. (Also there is a slot for an emergency TCM-6 a few hours before entry, but it is not ...
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### What are the choices today for orbital mechanics simulation software?

Orekit is the best space mechanics tool I know. Developed in Java (cross-platform), Orekit is a space dynamics open source library, based on Common Apache Math. Despite the fact it has no ...

### What are the practical uses of a state transition matrix?

From the top of my head I could think of the following practical applications for state transition matrices. Note that the application referred to in the question is captured in point 3. Also, I don't ...
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Accepted

### Conversion of velocity vectors between ICRF frames with different central objects

Assuming Newtonian mechanics are in play, velocities, like displacements, are three dimensional vectors. (There is no reason to go full-bore general relativistic with regard to behaviors in the solar ...
• 66k