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39 votes
Accepted

Person falling from space

Your question is under-specified (you don't give the size or posture of your subject), so I'm assuming an average-sized woman falling in the classic face-down skydiver posture. I'm also modeling this ...
Mark's user avatar
  • 14.7k
15 votes
Accepted

Why can't buoyancy of air be used to support a mega structure as an alternative to a space elevator?

Regardless of the accuracy of your calculations, what you propose isn't useful. Space isn't high, space is fast. Getting above the atmosphere only saves a little bit of energy; you still need to get ...
Mark's user avatar
  • 14.7k
9 votes

Closed Loop Space propulsion

That looks like a fairly standard "I don't understand magnets"-engine, with a side order of "I don't understand conservation of momentum". Don't spend too much time thinking about ...
Mark's user avatar
  • 14.7k
8 votes

Why can't buoyancy of air be used to support a mega structure as an alternative to a space elevator?

Your structure isn't competing with a space elevator, it is competing with other non-rocket spacelaunch ideas of various degrees of implausibility. Your vacuum balloon can't reach to orbit altitudes (...
Starfish Prime's user avatar
6 votes

Why can't buoyancy of air be used to support a mega structure as an alternative to a space elevator?

From a structural point of view, pumping air out is probably not what you want to do, since you are making a vacuum balloon. So if it could be constructed, it would be providing lift to the base, but ...
GremlinWranger's user avatar
6 votes

Calculating and Drawing the orbit of a body in a 2D gravity simulation in python

The easiest initial approach to this is probably to propagate your state forward in time steps, with a time delta small enough to have reasonable accuracy. You can ...
SE - stop firing the good guys's user avatar
4 votes

sun pointing coordinate system design

For a real mission, there would probably be more pointing constraints than just sun-pointing (likely for communication, thermal, or power reasons). However, for your purposes, you could do this: ...
Erin Anne's user avatar
  • 10.8k
4 votes
Accepted

Orbit Determination from Position and Velocity

First, some caveats: Always use the gravitational mass parameter $\mu_\text{body}$ rather than the product $GM_\text{body}$. The gravitational mass parameter $\mu_\text{body}$ conceptually is the ...
David Hammen's user avatar
  • 73.8k
4 votes

Converting Keplerian Orbital Elements into 2D State Vectors in Unity C#

Things wind up changing when you look at hyperbolic orbits instead of elliptical ones when going from cartesian vectors to Keplerian elements, because when you use the elliptical equations some of the ...
notovny's user avatar
  • 5,429
4 votes

Some exercise questions about Tsiolkovsky's Rocket Equation and Thrust Equation

For problem 3.27 not enough information is given. Assuming constant mass flow rate, the burn time is: $$\tau = \frac{R-1}{R} \frac{c}{a_0}$$ where R is mass ratio ($MR$), $c$ is exhaust velocity, $...
W H G's user avatar
  • 696
3 votes

Which notes and/or books on mathematics, physics, 3D geometry preparatory to the study of orbital dynamics?

There was a recent Hacker News on this: https://news.ycombinator.com/item?id=35762483 IMHO if you're only going to get to one of them, Bate, Mueller & White "Fundamentals of Astrodynamics&...
nbodyphysics's user avatar
3 votes

Will this homopolar motor self rotate in a vacuum?

Edit: Maybe Not The classic homopolar motor will spin like any other motor in zero G, with the two halves spinning in opposite directions, due to conservation of momentum, then as it runs flat and ...
GremlinWranger's user avatar
3 votes

Is Electromagnetic Propulsion Like Radiation Pressure propulsion?

tl;dr: Think "antenna" and "beam of photons" rather than "pushing a plate with an electromagnet". If your spacecraft accelerates (in your frame of reference) because of ...
uhoh's user avatar
  • 149k
3 votes

What is missing in the conversion of specific impulse from units of seconds to thrust/mass flow rate?

But I can't figure out why you must introduce g into the equation as it doesn't appear during the dimensional analysis. g is required because the use of specific impulse in seconds comes from using ...
Russell Borogove's user avatar
1 vote

sun pointing coordinate system design

For HETE-2, the onboard ACS computed in body coordinates, and, in effect, rotated the universe to put the Sun where it wanted when not in eclipse. That, of course, does not control rotation about the ...
John Doty's user avatar
  • 2,589
1 vote

sun pointing coordinate system design

To orient the ship to face the sun steadily, try the vector of the ship to the sun, and cross that with the velocity vector of the earth relative to the sun (not the ship relative to earth). ...
cubetronic's user avatar

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