Questions tagged [flight-computer]

Questions regarding the computers onboard spacecraft which handle mission-critical data.

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Mariner 9 computing equipment

I am guessing the word CPU can't be used in reference to computers in 1971. So I am wondering what type of electronic equipment were put in place of a regular CPU ...
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3 votes
0 answers
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What programming language will the lunar gateway run on? How much of its code will be inherited from existing ISS components?

What programming language will be used for the main elements of the lunar gateway? Will programmatical components be inherited from the ISS? If so, to what extent?
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9 votes
2 answers
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How were registers in the Apollo Guidance Computer implemented?

I'm having a hard time finding information on the composition of the AGC's registers. Were they also Magnetic Core Memory or something else?
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0 votes
1 answer
273 views

What would have happened if all Apollo computers failed?

Let's assume all available computers in the command module and the lunar module failed and the astronauts were unable to repair them in flight. Would they have been able to return back home safely ...
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24 votes
7 answers
7k views

Why do spacecraft have small RAM? Which spacecraft had the largest memory?

Computers on spacecraft often have small memory, like a few MB. Wouldn't it be nice to put more memory into them? Or is MB-level already enough? Also, which spacecraft has the largest memory?
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29 votes
2 answers
4k views

How did the Apollo guidance computers deal with radiation?

I was wondering how the Apollo guidance computer handled the radiation encountered in space
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13 votes
2 answers
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Did the Curiosity and Perseverance rover brains do the driving from Earth to Mars?

This interesting answer to Why did NASA intentionally crash-land the Curiosity and Perseverance sky cranes on Mars? leads me to wonder if the Curiosity and Perseverance rover computers were in charge ...
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8 votes
1 answer
158 views

Rad-Hard vs Space-Hard computing

Radiation hardened CPUs like RAD750 are radiation hardened for up to 1000 gray. Cool. But, as CPUs have advanced way ahead their mechanical counterparts in miniaturization and fragility, energy ...
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2 votes
2 answers
113 views

Efficiency in Space Capsule Docking Process

I'm watching the first operational Crew Dragon Capsule proceed through the regimented, and VERY careful International Space Station (ISS) docking process, which was turned on after pausing another ...
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1 vote
2 answers
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Magnetometer in space

See, i recently buy a magnetometer to experiment with arduino, i want start building a litle fly computer for a cubesat (this cubesat have an ion engine, so, have thrust). I start reading the Azimuth ...
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12 votes
1 answer
2k views

How did the Apollo Lunar Rover navigation system computer work?

Unlike the more famous Apollo Guidance Computer I can't find any information about the computer used in the manned lunar rover. It seemed to track three values and display them on analog gauges: the ...
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23 votes
7 answers
5k views

Unix Epoch in International Space Station

The International Space Station is in a different gravitational field than us on the Earth's surface. Almost all computers / protocols depend on the Unix epoch being consistent everywhere. The Unix ...
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27 votes
9 answers
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Why would such a powerful computer (or a computer at all) be needed to go to the Moon?

I keep hearing people say things like: Duuuude! It's so insane that we're carrying around phones in our pockets that are a thousand times faster than the computers that took us to the moon! Why do ...
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2 votes
1 answer
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When and when not to use the SDLS protocol?

When should the features provided by the Space Data Link Security Protocol (SDLS) be applied to TM Data Space Link Protocol communications? This is with respect of ensuring protection within the ...
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8 votes
1 answer
4k views

Which operating system is Perseverance running?

A few days ago, I watched Perseverance being launched towards Mars. I know that there is lots of very specific hardware embedded into the rover, so, very likely, there has been software written by ...
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6 votes
1 answer
638 views

What is a "flight string"?

This answer explains what software powers the Falcon 9 launch vehicle. The flight software is written in C/C++ and runs in the x86 environment. For each calculation/decision, the "flight string&...
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4 answers
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Computers for Apollo Mission

Why did NASA invest so much amount of time and money on developing computers for Apollo Missions? Wouldn't the Man on Moon mission have been far easier and faster if the Astronauts drove the ...
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7 votes
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How long do we have contact with a centaur after launch

When centaur separates the payload, we can see a video signal of this happening. The mission of centaur is completed now, but are there still some activities centaur is performing after seperation? ...
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4 votes
1 answer
219 views

How did the automatic sextant on the late-1950's MIT Mars Probe work?

The reason MIT was chosen to develop the Apollo guidance computer was their Instrumentation Lab. They specialised in inertial navigation and had done impressive work on inertial navigation for ...
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7 votes
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How are Spacecraft Event Times (SETs) managed; to what timescales are they linked?

Spacecraft Event Time explains the importance of remembering just how darn slow light is; it takes minutes, hours, and in a few cases almost a day for light to travel one way between humans and their ...
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1 vote
1 answer
259 views

RCS or Reaction Wheel for a 30kg cubesat

I am working on the design of a cubesat, it weighs approximately 30 kg and I am doing the Navigation and Guide Control system. I was wondering if I had some blueprint for some RCS or Reaction Wheels ...
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5 votes
1 answer
141 views

Would astronauts have been able to save the CST-100 mission?

The Boeing CST-100 Starliner failed an unmanned test because the timer on the spacecraft was off by 11 hours. This caused the spacecraft computer to think it was ahead in mission timing by 11 hours, ...
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3 votes
2 answers
449 views

Interplanetary spacecraft flight operating system and programming language

Which programming languages and operating systems are mostly used for interplanetary satellites (such as a mission to the moon)? To my knowledge, I know some LEO CubeSats use C programming language ...
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10 votes
1 answer
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How would the state vector be updated in the Apollo Guidance Computer during coasting to/from the moon if communication with Earth was lost entirely?

This source https://www.hq.nasa.gov/alsj/alsj-average_g.html states that: From time to time, Houston could update the onboard SV using tracking and other available date; [sic] but, generally, it ...
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1 vote
0 answers
138 views

Commercial 3DoF/6DoF trajectory simulation and optimization tool for launch vehicle

Is there any 3DoF/6DoF trajectory simulation and optimization tool for launch vehicles like POST available commercially? If there whether it's how reliable when it comes to using for real-time ...
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48 votes
3 answers
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Why don't we shield existing CPUs from radiation instead of designing new ones?

I've just read this article about space-graded CPUs [1]. I am not a space expert at all but a question was born naturally: why don't we prefer to shield earth-designed CPUs (far less expensive) than ...
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-2 votes
4 answers
259 views

What exactly makes PHP CLI fundamentally unsuitable to power all the math on board a space craft?

Let's say that there is an eccentric multi-trillionare who made his fortune by coding a very popular service in PHP. He knows it very well, and has such a love for it that he makes a rather unorthodox ...
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12 votes
1 answer
2k views

Double redundancy for the Saturn V LVDC computer memory, how were disagreements resolved?

In the Smarter Every Day video How did NASA Steer the Saturn V?- Smarter Every Day 223 Destin is talking with Luke Talley about the memory modules used in the Saturn V LVDC computer. This computer ...
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4 votes
1 answer
189 views

How do small, spin stabilized launchers follow a rhumb line?

This concise answer to What exactly is rhumb-line control in the context of a launch trajectory? explains the concept in the context of the SS-520 nanosatellite launch vehicle (which "doesn't exist"). ...
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6 votes
1 answer
211 views

Why did a phase mismatch between the Apollo 11 LM's RR and AGC generate a large numbers of interrupts?

A critical aspect of the cause of the famous 1202 and 1201 alarms reported by the Apollo Guidance Computer (AGC) during the decent of the Apollo 11 LM is that the rendezvous radar (RR) was using a "...
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13 votes
2 answers
3k views

Did the 1202 error and associated reboot prevent disaster on Apollo 11 landing?

Most accounts of the famous 1202 error reported by the AGC during landing of the Apollo 11 LM characterize the event as result of the successful operation of the AGC, flushing an resetting an ...
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11 votes
1 answer
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Is this really the Saturn V computer only, or are there other systems here as well?

The BBC News article Apollo in 50 Numbers; The Technology shows an image of the Saturn V's computer along with the caption: The Saturn V's computer was probably the largest computer ever blasted ...
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114 votes
6 answers
24k views

What makes Ada the language of choice for the ISS's safety-critical systems?

We have it on good authority that Ada is widely used for "safety critical software" on at least the US side of the International Space Station. Of all the possible languages to choose from, what are ...
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4 votes
2 answers
273 views

What would cause the Shuttle's redundant computers to disagree?

The Shuttle had five AP-101 general purpose computers. As discussed in this question, the system was redundant and there was a voting process to eliminate a computer whose results disagreed with the ...
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9 votes
1 answer
284 views

How did Shuttle computers internally represent time?

How was time represented in the five AP-101 general-purpose computers of the Space Shuttle? How many bits? Encoded as a plain binary count? Split into hours, minutes, seconds, subseconds? Binary-...
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5 votes
1 answer
2k views

Has magnetic core memory been used beyond the Moon?

@aml's comment under @OrganicMarble's answer to the question Did the IBM System/4 Pi computer have radiation-hardened versions for Skylab and Shuttle? says: @uhoh- according to wikipedia, the AP-101B ...
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4 votes
1 answer
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Did the IBM System/4 Pi computer have radiation-hardened versions for Skylab and Shuttle?

Wikipedia's article on the IBM System/4 Pi says: The IBM System/4 Pi is a family of avionics computers used, in various versions, on the F-15 Eagle fighter, E-3 Sentry, AWACS, Harpoon Missile, NASA's ...
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23 votes
2 answers
4k views

How did the Apollo guidance computer handle parity bit errors?

The following answers mention the use of parity bits in the Apollo guidance computer: this answer to Bits per core for the different versions of the Apollo guidance computer core rope memory? this ...
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4 votes
1 answer
188 views

How many AGC keystrokes did an Apollo rendezvous take?

My kids have a rather nice picture book about the first moon landing titled “One Giant Leap”. I find it to be a fairly accurate retelling of the events of Apollo 11 in a poetic style. However, one ...
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22 votes
1 answer
5k views

What exactly turned on the light indicating Apollo 8 was starting to fall towards the Moon?

@PearsonArtPhoto's answer links to the page Apollo 8, 21 – 28 December 1968 by Hamish Lindsay at honeysucklecreek.net from where I have quoted below. Question: What exactly turned on the light ...
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6 votes
0 answers
300 views

Why do SD cards perform so much better than SSDs in space?

SD cards and SSDs are based on the same technologies, so why the stark differences in performance? Recently, it was reported that after a year in space, half of the SSD drives on the HPE Spaceborne ...
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6 votes
3 answers
466 views

What are some notable computer systems used in space probes?

I was reading about Cassini and learned that it used a CPU architecture I'd never heard of before, called MIL-STD-1750A. This got me thinking. What are the most common (or otherwise notable) CPU ...
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1 vote
0 answers
57 views

Distributed computational power-sharing and orbital supercomputer

I had an interesting conversation last night with a nanosatellite engineer about how much computational power is required in a nanosatellite constellation and if it's necessary. I had an idea or a ...
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1 vote
2 answers
567 views

How accurate can a satellite's orbit be?

How precise can an artificial satellite be when it comes to following the exact orbit in relation to Earth or hitting the same point above Earth in orbit? Which orbit would be the most stable for this?...
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6 votes
3 answers
1k views

How would the International Space Station be maintained unmanned?

Russia's lunch to the ISS failed and the crew may have to leave it unmanned. How would the ISS run without a crew? Could some one else take it over or squat in it? https://www.npr.org/2018/10/11/...
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8 votes
1 answer
664 views

How does the Apollo LM ascent guidance program P12 actually work?

P12 is the AGC guidance program for normal ascent from the lunar surface to orbit. According to the mission planning documents, after separation and ignition, the ascent stage holds its initial ...
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2 votes
2 answers
279 views

Arcustangent function of the Apollo Computer, atan() or atan2()?

What type of the arcustangent function was used, the one with single argument only or the famous atan2(y, x) or arctan2(y, x) with two arguments x and y? What kind of aproximation was used?
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158 votes
3 answers
24k views

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

Navigation with a sextant or maneuvers using gimbal angles might be two examples of cases where an Apollo computer might need to do trigonometry. Trigonometric functions like sine, arctangent, etc. ...
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11 votes
1 answer
340 views

Problems as a result of clock drift that have occurred in space?

I was reading this question about the clock drift on the Apollo missions and am sure that a drift of 1 second / day on some of the longer missions would likely result in a mission failure due to the ...
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3 votes
2 answers
364 views

Apollo-11 AGC core memory has 5 wires per core (rather than 3 or 4) - why?

Apollo-11 AGC core memory has 5 wires per core (rather than 3 or 4) - why? I am referring to this image in Wikipedia: https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#/media/File:...
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