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302 votes
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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 ...
supinf's user avatar
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132 votes
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How is stacking oranges in 24 dimensions related to receiving and decoding signals from the Voyagers?

All the different data words a transmitter can send and a receiver can detect can be imagined as dots arranged in a large space. Selecting a data encoding for error detection and correction is about ...
asdfex's user avatar
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92 votes

How did people know how to build the first space ship?

This is a very broad question, but I'll take a stab at it. It was understood that gravity pulled the Earth into a spherical shape, with dense solids and liquids below less-dense gases, and it was ...
Russell Borogove's user avatar
81 votes
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How did the Lunar Module dock with the rest of Apollo 11 and what is the "CSM"?

The Apollo spacecraft consists of three major parts: The Command Module (CM), a conical module where the three crew members live during launch from Earth and travel to and from the moon, and which re-...
Russell Borogove's user avatar
74 votes
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What "fuel more powerful than anything the West (had) in stock" put Laika in orbit aboard Sputnik 2?

Laika's magical mystery propellant was kerosene and LOX. Sputnik 2 was launched on the 8K71PS launcher. This was a modified R-7 ICBM, and like all the R-7 derived launchers, its RD-107 and RD-108 ...
Russell Borogove's user avatar
63 votes

How did people know how to build the first space ship?

One important note is that rocketry predates space travel - by a lot. The V-2 rocket christened "MW 18014", the very first suborbital flight, (meaning the rocket flew to space, but didn't go fast ...
Knetic's user avatar
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62 votes
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In this iconic lunar orbit rendezvous photo of John Houbolt, why do arrows #5 and #6 point the "wrong" way?

They are burns, with the direction of the arrow roughly indicating the direction of thrust. Ascent Earth orbit insertion Trans-lunar injection Midcourse correction Lunar orbit insertion Burn to drop ...
Organic Marble's user avatar
59 votes

Why was Venus rather than Mars targeted for the first interplanetary landings?

The reason is delta-v, which is a crucial concept in Spaceflight. It means change in velocity, and is the primary 'currency' that space mission have to expend in order to reach places in the solar ...
Rikki-Tikki-Tavi's user avatar
59 votes
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What is the difference between Cape Canaveral and Kennedy Space Center?

Supplementary answer: Some of the confusion arises because there is also a geographic feature named Cape Canaveral. It's pretty much the green area shown in the other answer, east of the Banana River....
Organic Marble's user avatar
55 votes
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Was "Apollo" an acronym for "America’s Program for Orbiting Lunar and Landing Operations"?

From a pre-launch press release for Apollo 11: Among the many missions conceived at that time was a manned journey to the Moon and back. Dr. Silverstein himself named it "Apollo" after one ...
PearsonArtPhoto's user avatar
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50 votes

How do we know the Apollo Moon landings are real?

As belief in conspiracy theories is associated with the rejection of science, it is likely that this answer will be rejected by many at the outset. If you doubt the reliability of science, perhaps you ...
50 votes
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Can we write with chalk on blackboard in space?

There's no scientific reason against using a chalkboard, zero gravity isn't an impediment as making a mark is dependent on pressure between the chalk and the board. The reasons for not using chalk are ...
GdD's user avatar
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47 votes
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Why did NASA set up a computing facility in Bermuda in the Mercury epoch?

Bermuda was one of the tracking stations for the Mercury program. Bermuda was critical as it had a good view of much of the ascent trajectory. In this image, all of the tracking stations are shown ...
Hobbes's user avatar
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47 votes

Why would such a powerful computer (or a computer at all) be needed to go to the Moon?

Assuming this isn't a troll question and you are serious about wanting to know what computers are used for in spaceflight (prior to 1988), NASA has a great resource for you: Computers in Spaceflight (...
Organic Marble's user avatar
46 votes

What was the first programming language in space?

(I'm interpreting the question as "what programming language was the first spacecraft software written in?", per discussion in comments above.) This will depend on your definitions of "...
Russell Borogove's user avatar
46 votes
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How did sloshing prevent the Apollo Service Module from moving safely away from the Command Module and how was this fixed?

Let's start with the "Statement of Problem" in the anomaly report. ...the service module, upon being jettisoned on a lunar return flight, should have entered the earth's atmosphere, then skipped ...
Russell Borogove's user avatar
46 votes
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What is the story behind specific impulse being expressed in seconds?

It's even simpler than a German-American disagreement. It's use of ambiguous units. The term "specific X" means the amount of X you can get from a unit mass of something. For instance, in batteries, ...
Tom Spilker's user avatar
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46 votes

Did Sputnik 1 tell us more than "beep"? What science was improved by information gained from its orbiting the Earth?

Shot answer: Was Sputnik-1 "only for beep" - no, it wasn't :) It was technical test of R-7 as space launcher and test of spacecraft in orbit (athough very simple spacecraft). Also scientists ...
Heopps's user avatar
  • 9,041
45 votes

What are the most serious injuries that astronauts have suffered while in orbit?

The Mars Society has a good indication of what the most serious medical issues have been in space flight. These include: A number of cases where the gloves leaked in an EVA. (STS-37, Mir Space ...
PearsonArtPhoto's user avatar
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45 votes
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Have there ever been people trapped in a shut down spacecraft?

Seeing as the answer is "no" (As per @DarkDust), I thought I'd add a situation that's similar. There was a short period aboard Mir after the collision with progress where all astronauts were without ...
Magic Octopus Urn's user avatar
44 votes
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When did the concept of "stages" enter rocketry?

The first multistage rocket is much older then one might think. Its from the 14th century CE. Huolongchushui or fire dragon issuing from the water (Chinese: 火龙出水; pinyin: huolóngchushui; literally: ...
Polygnome's user avatar
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44 votes
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Was the "Earthrise" witnessed by Apollo 8 the first available "full" photo of the Earth?

No; the first full views of Earth from high-altitude satellites predate Apollo 8 by at least two years. This web page has a nice progression of pictures of Earth from space from 1959 on. A Soviet ...
Russell Borogove's user avatar
42 votes
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Why were there two cosmonauts shown in the movie "Gagarin"?

As was common for spaceflight, there was a primary crew for the mission (Gagarin) and a backup. Gagarin was the primary crew, and his backup was Gherman Titov (who would fly Vostok 2 four months later)...
Andrew is gone's user avatar
41 votes

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 ...
dlatikay's user avatar
  • 713
41 votes

When was Newton "not good enough" for spaceflight; first use and first absolute requirement for relativistic corrections?

As far as I know, there has not been a space mission that would have been impossible without a theory of relativistic physics. It is true that the relativistic effects are clearly visible in GPS ...
jpa's user avatar
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41 votes
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How did they access the LM to mount the flag package while the Apollo stack was already on the launch pad?

They used the Mobile Service Structure (MSS), which for some reason is rarely shown in Apollo pre-launch photos. The large work platforms at upper right completely surrounded the spacecraft and ...
Organic Marble's user avatar
41 votes
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Gagarin not ejecting from capsule

Initially, the USSR insisted that Gagarin had landed with the spacecraft, because of requirements for FAI certification of spaceflight records: One of the stipulations for spaceflight requires that ...
Russell Borogove's user avatar
40 votes
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What are some of the obsolete technologies that space agencies used in day-to-day work during the 1960s?

Everything has changed in the last 50+ years. Every group working on space exploration had secretaries, lots and lots of secretaries, about one for every four to ten technical employees, plus many ...
David Hammen's user avatar
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38 votes
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Function of the separated, individual solar cells on Telstar 1 and 2? Why were they "special"?

The small separated cells had several functions. Six individual units, the "solar aspect cells", were each oriented and attached as if they were on the sides of a cube to identify the spacecraft's ...
Bob Jacobsen's user avatar
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