# Tag Info

Accepted

### How did the Apollo computers evaluate transcendental functions like sine, arctangent, log?

Since the Apollo 11 code is on GitHub, I was able to find the code that looks like an implementation of sine and cosine functions: see here for the command module and here for the lunar lander (it ...
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### Time at 1 g acceleration to travel 100 000 light years

Nonrelativistic solution The variables used will be $x$ for the distance travelled $v$ for velocity $a$ for acceleration ($1~\mathrm{g}$) $t$ for the time $c$ for the speed of light. Non braking ...
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### How did the Apollo computers evaluate transcendental functions like sine, arctangent, log?

You also asked for the logarithm, so let's do this as well. As opposed to the sine and cosine functions, this one is not implemented with a Taylor series-like approach only. The algorithm is based on ...
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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 ...
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### What is the "pendulum rocket fallacy" as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?

The pendulum fallacy is the belief that rockets would be passively stable with engines at the top, with the rocket "hanging" from them. The error lies in expecting gravity to pull the body ...
Accepted

### Who developed the mathematics used to correct the trajectory of Apollo 13?

The authors of the paper are Harold A. Hamer, Katherine G. Johnson, and W. Thomas Blackshear. Of these, the name Katherine Johnson might ring a bell with people, as she was one of the protagonists in ...
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### How complex was the math and physics necessary to place Apollo 11 on the moon?

Was standard Newtonian mechanics sufficient or were relativistic effects included? Relativistic effects didn't have to be modeled; other sources of error would have swamped the effects of relativity,...
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### What is the "pendulum rocket fallacy" as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?

In the inverted pendulum problem: gravity exerts a vertical force on the pendulum, at the center of gravity the support of the pendulum (like the finger under the pencil) exerts a vertical force on ...
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### What is the velocity of the ISS relative to the Earth's surface?

JPL Horizons has trajectory data for the International Space Station, SPKID = -125544 Revised: Nov 23, 2022 Trajectory is TLE-based. Predicts run for 4 weeks into future, but are of low accuracy for ...
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### What is the "specific impulse"?

If you want to understand how the 'seconds' value fits the greater image, there's this rather contrived definition (which nobody uses because it's contrived and mostly useless but evocative enough.) ...
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### Besides retarded gravitation, anything else to worry about when calculating MU69's orbit from scratch?

This is not a complete answer. It is instead an extended comment to the following: I understand I will have to retard the gravity from each source by its particular light-time, as well as correct ...
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