73

Because shielding against radiation is heavy, and weight is the enemy of getting things into space. CPUs are quite sensitive to radiation, and some types of radiation (cosmic rays) are not only quite good at penetrating most things, as they do, they cause a cascade of secondary radiation. To protect a device form any of this radiation getting through is not ...


46

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 (PDF, 494 Mb) From the introduction: Computers are an integral part of all current spacecraft. Today they are used for guidance and navigation functions such as ...


27

First of all, the ground team could have, and in fact did, do most of the orbital navigation remotely. This report mentions the fact that the on board computer was secondary for Apollo 8, with primary being systems from the ground. The spacecraft did have to do a few things, including making some realtime adjustments during the landing based on the actual ...


26

Your spacecraft would need to be several orders of magnitude larger than the Saturn-Apollo. No human pilot has successfully performed a rendezvous without a computer. Note that rendezvous is bringing two spacecraft close together in orbit, position, and velocity. Docking is the actual physical contact between two spacecraft. The latter can and often is ...


23

“Do I have a very naive concept of space travel?“ - honestly, yes you do. Here is an excerpt from Don Eyles’s wonderful book Sunburst and Luminary: An Apollo Memoir: Guidance would be processed every two seconds, repeatedly correcting and refining the trajectory based on new data from navigation. Into the guidance equation, with each turn of the crank, went ...


14

You actually ask a really good question. And the answer is, we do both, depending on the needs. NASA tends to go for the ultra-reliable, and radiation tolerant components are more reliable, thus it is their preferred way. Many commercial satellites, however, use non-space grade components that are shielded lightly, and with software and hardware built in a ...


12

The restrictions you are quoting only apply to the LGC, the computer in the Lunar Module. The Command Module Computer does not have these restrictions (compare the section about the Coasting Integration Routine you quote with the same passage from the document about the CMC: https://www.ibiblio.org/apollo/Documents/R-577-Colossus2-Martin-5.2.pdf). The CMC ...


11

The onboard computers were primarily provided for Guidance, Navigation, and Control (GNC). The mere act of starting and/or stopping a rocket engine burn is simple enough for humans to do. Figuring out when to start and stop that burn, and where to point the spacecraft during it, are not something humans are going to do unaided in an operational amount of ...


9

Line of sight maneuvers are not precise enough regarding the huge distance from Earth to the Moon. The mid course corrections were impossible without the calculations done by the computer. If course corrections far from the Moon are not precise, much more fuel is needed for corrections close to the moon. Orbital rendezvous maneuvers are much more difficult ...


8

No specific knowledge of Falcon, but a "string" in avionics terminology means a element of a redundant flight control system consisting of a flight computer and a data bus to a set of sensors and effectors. Here's a schematic from the Shuttle showing one flight computer (on the left, labled GPC for General Purpose Computer) interfacing to four ...


7

I don't understand why a computer was needed at all, either on the ground or inside the space craft. As Ben (PearsonArtPhoto) pointed out, computers have always been a part of launching rockets. By no means an optional one. Computers are needed to avoid collisions with the debris around earth, to auto-pilot spacecrafts and to monitor mission data (sensors, ...


7

It's running VxWorks, at least according to Wikipedia, and in fact there is a direct statement to this effect here (PDF link): The M2020 flight software runs on the VxWorks operating system, and is written in C. VxWorks is what pretty much all the US landers have run, and it's still, I think, the obvious choice: it's a very mature, very tested system.


7

The decision to have a complicated computer that controlled many of the spacecraft functions was made in 1961, very early in the Apollo program. From NASA's history, Computers On Board The Apollo Spacecraft: The need for an on-board computer The presence of a computer in the Apollo spacecraft was justified for several reasons. Three were given early in the ...


6

Filo has covered operating systems, so I won't repeat that here (except to reference this answer about New Horizons' OS, which is Nucleus RTOS rather than VxWorks, by way of a change). As for programming languages, there's inevitably a lot of C and C++, though there's a chance that a somewhat restricted subset of the languages is used to improve safety, ...


5

According to the NASA Administrator if the crew had been present, yes. "This anomaly has to do with automation," Bridenstine said. "Nicole [Mann] and Mike [Fincke] are trained specifically to deal with the situation that happened today, where the automation was not working according to plan." Source Presumably this means that an onboard crew could ...


5

From my experience: Ground operators work with UTC. All events are time tagged with UTC time stamps. This is a bit of a hassle for programmers who have to deal with leap seconds, but makes everything more organized and understandable for people. Onboard computers have onboard clocks, which normally count ticks (or seconds) since last reset. The offset ...


5

Developing software for space applications is quite different from "regular" software development, especially when we're considering human spaceflight. If you want to develop critical software (i.e. software that, in case of a failure, can lead to loss of life, mission, and/or facilities) for ESA, you need to comply with the applicable standards defined by ...


4

Let's have a look on a 1998 paper on real time systems from CMU (Carnegy-Mellon Univeristy). Typical examples of real-time systems include Air Traffic Control Systems, Networked Multimedia Systems, Command Control Systems etc. In a Real-Time System the correctness of the system behavior depends not only on the logical results of the computations, but ...


3

Manual rendezvous was tried first, in Gemini 4. It went badly, because orbital mechanics are very counter-intuitive. As GPO engineer Andre Meyer later remarked, "There is a good explanation for what went wrong with rendezvous." The crew, like everyone else at MSC, "just didn't understand or reason out the orbital mechanics involved. As a ...


3

As just one example consider the Lunar landing. If you think about a vehicle sitting on top of a rocket, with the thrust vector of the rocket passing through the centre of mass of the system for a moment you'll realise that it's not stable: there's nothing making it want to point in any particular direction. But you need it to face in some very particular ...


3

Example 1 : RTEMS, source https://devel.rtems.org/wiki/TBR/Website/Wheres_RTEMS Example 2: VxWorks, source: https://en.wikipedia.org/wiki/VxWorks#Aerospace_and_defense


3

What exactly makes PHP CLI fundamentally unsuitable to power all the math on board a space craft? ... What, exactly, is it about this that is so "crazy"? You seem to be taking the unsuitability of PHP as a given premise here. Why is that? PHP has two major deficiencies that are relevant here. One is that it's not very performant; the reference ...


2

This is something I've been looking into as well. Here's my idea: Use ATMEGA328 (or ATMEGA16A if durable enough) with triple redundancy, using only thru-hole components on protoboard. As mentioned elsewhere here, use leaded solder. The voting circuit for each digital output can be built with 4 logic gates. An error counter and watchdog circuit to reset a ...


2

Throwing some rough and ready math at the question, happy to be corrected by anybody with actual numbers. Hardening increases the radiation level to trigger errors by several orders of magnitude, call it 1000 for this. Dropping the radiation by a factor of 1000 to a 10cm cube would take about half a mm of lead, adding up to something like 250g. Most ...


1

A computer is a "broad term" Calculations are necessary for all factors of momentum, energy, thrust, power, energy management, etc. The point is, NASA had computers on it's early spacecraft. The Gemini missions had a computer as well for ascent, descent, flight and orbital maneuvering. However, NASA realized computational power was premium so they ...


1

It's all hard. Try operating a basic ascent to orbit simulator where YOU control eg just the thrust. See how many attempts it takes you to reach orbit. Decades ago I did this many, many .... times. Even with vast experience, achieving orbit was a pleasant surprise.


1

The Navigation Museum of The Institute of Navigation has an Apollo Sextant on display: (Apollo Sextant (source)) The item description mentions it is fabricated in 1960, just after the Mars Study. In fact, the study is referenced: In 1957 The Lab made a proposal to the U.S. Air Force, for a 150 kg., unmanned probe, which would fly by Mars and take high-...


1

While there are some commercially available thrusters for Cubesats, any kind of thruster on a Cubesat places you very much in experimental territory. (Additionally, any system that includes liquid or gaseous fuel under pressure will make it significantly harder to get a cubesat approved to be launched, since it's against the usual rules and will need a ...


1

One addition to the answer by @supinf: a) The initial DOUBLE in SPT b) overflows for input x (register A) above +0.5 (+90°) and underflows for x below -0.5 (-90°). In this case, A is >+1 or <-1 and the following TS stores the corrected value (effectively add one, if it is below -1, or subtract one, if it is above +1) in TEMK and sets A to the +1 (...


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