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Apollo 11 vs. USB-C Chargers (2020)

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Re: Apollo 11 vs. USB-C Chargers (2020)

#11

Post by GlenTheMachine »

orliesaurus wrote: post #7

54 years ago - wow - was the Apollo 11 Moon Landing Guidance Computer (AGC) chip the best tech had to offer back then?

Yes, given the size, power, and reliability constraints. There were, of course, far more powerful computers around… but not ones you could fit in a spacecraft the size of a Volkswagen Beetle.

The Apollo program consumed something like half of the United States’ entire IC fabrication capacity for a few years.

https://www.bbc.com/future/article/20230516-apollo-how-moon-...

Re: Apollo 11 vs. USB-C Chargers (2020)

#12

Post by vlovich123 »

Is the weight/cost calculus sufficiently improved now that it’s cheaper to shield the processor in it’s entirety rather than trying to rad harden the circuitry itself (much more expensive due to inability to use off the shelf parts & limits the ability to use newer tech)?

If I recall correctly this was one of the areas being explored by the mars drone although not sure if Mars surface radiation concerns are different than what you would use in space.

Re: Apollo 11 vs. USB-C Chargers (2020)

#13

Post by dgacmu »

orliesaurus wrote: post #7

54 years ago - wow - was the Apollo 11 Moon Landing Guidance Computer (AGC) chip the best tech had to offer back then?

Yes when accounting for size. If you wanted something that was the size of a refrigerator, you could buy a data general Nova in 1969: https://en.m.wikipedia.org/wiki/Data_General_Nova

8KB of RAM! But hundreds of pounds vs 70lb for the AGC with fairly comparable capability (richer instructions/registers, lower initial clock rate).

The AGC was quite impressive in terms of perf/weight

Re: Apollo 11 vs. USB-C Chargers (2020)

#14

Post by kristopolous »

GlenTheMachine wrote: post #8
kristopolous wrote: post #2

When we go back to the moon, I wouldn't be surprised if Zilog-Z80s were a major part of the hardware. Well known, well understood, predictable hardware goes a long way. There's a bunch of other considerations in outer space and z80s have proven robust and reliable there. Also I'd expect a bunch of Kermit and Xmodem to be used as well.

They won’t be. We will use RAD750’s, the flight qualified variant of the PowerPC architecture. That’s the standard high end flight processor. https://www.petervis.com/Vintage%20Chips/PowerPC%20750/RAD75... The next generation (at least according to NASA) will be RISC-V variants: https://www.zdnet.com/article/nasa-has-chosen-these-cpus-to-...

The 750 is still based on a 27 year old chip and runs at half its clockspeed. The point was that spaceflight is relatively computationally modest.

Re: Apollo 11 vs. USB-C Chargers (2020)

#15

Post by db48x »

GlenTheMachine wrote: post #11
orliesaurus wrote: post #7

54 years ago - wow - was the Apollo 11 Moon Landing Guidance Computer (AGC) chip the best tech had to offer back then?

Yes, given the size, power, and reliability constraints. There were, of course, far more powerful computers around… but not ones you could fit in a spacecraft the size of a Volkswagen Beetle. The Apollo program consumed something like half of the United States’ entire IC fabrication capacity for a few years. https://www.bbc.com/future/article/20230516-apollo-how-moon-...

The AGC was 2 ft³. I believe the volume was written into the contract for development of the computer, and was simply a verbal guess by the owner of the company during negotiations. On the other hand, they had been designing control systems for aircraft and missiles for over a decade at that point so it was not an entirely uninformed guess.

The amazing thing is that they did manage to make it fit into 2 ft³, even though the integrated circuits it used had not yet been invented when the contract was written.

Re: Apollo 11 vs. USB-C Chargers (2020)

#16

Post by kens »

> Apollo 11 spacecraft contains 4 computers

Analog computers don't get the respect they deserve. There's one more computer, the FCC. The Flight Control Computer is an analog computer in the Saturn V that controlled the rocket gimbals. It's a two-foot cylinder weighing almost 100 pounds.

Re: Apollo 11 vs. USB-C Chargers (2020)

#17

Post by johnwalkr »

kristopolous wrote: post #2

When we go back to the moon, I wouldn't be surprised if Zilog-Z80s were a major part of the hardware. Well known, well understood, predictable hardware goes a long way. There's a bunch of other considerations in outer space and z80s have proven robust and reliable there. Also I'd expect a bunch of Kermit and Xmodem to be used as well.

I work in this space and z80, kermit and xmodem are not part of the solution. Just because this stuff is simple to the user doesn't mean it's the best suited, and there's a whole industry working on this since the Z80 days. You can buy space-qualified microcontroller boards/components with anything from a simple 8 bit microcontroller to a 64-bit, multicore, 1Ghz+ ARM cpu depending on the use case. I'm sure Z80 has been used in space, but in my time in the industry I've never heard of it.

Kermit and xmodem probably aren't what you want to use, they are actually a higher level than what is normally used and would require a big overhead, if they even worked at all with latencies that can reach 5-10s. Search for the keyword "CCSDS" to get hints about data protocols used in space.

Re: Apollo 11 vs. USB-C Chargers (2020)

#18

Post by atleta »

kristopolous wrote: post #2

When we go back to the moon, I wouldn't be surprised if Zilog-Z80s were a major part of the hardware. Well known, well understood, predictable hardware goes a long way. There's a bunch of other considerations in outer space and z80s have proven robust and reliable there. Also I'd expect a bunch of Kermit and Xmodem to be used as well.

It seems it's going to be a new, RISC-V based chip:

[1] https://www.zdnet.com/article/nasa-has-chosen-these-cpus-to-... [2] https://www.nasa.gov/news-release/nasa-awards-next-generatio...

Re: Apollo 11 vs. USB-C Chargers (2020)

#19

Post by thebestmoshe »

vlovich123 wrote: post #12

Is the weight/cost calculus sufficiently improved now that it’s cheaper to shield the processor in it’s entirety rather than trying to rad harden the circuitry itself (much more expensive due to inability to use off the shelf parts & limits the ability to use newer tech)? If I recall correctly this was one of the areas being explored by the mars drone although not sure if Mars surface radiation concerns are different…

Isn’t this basically what SpaceX is doing?

> The flight software is written in C/C++ and runs in the x86 environment. For each calculation/decision, the "flight string" compares the results from both cores. If there is a inconsistency, the string is bad and doesn't send any commands. If both cores return the same response, the string sends the command to the various microcontrollers on the rocket that control things like the engines and grid fins.

https://space.stackexchange.com/a/9446/53026

Re: Apollo 11 vs. USB-C Chargers (2020)

#20

Post by jojobas »

vlovich123 wrote: post #12

Is the weight/cost calculus sufficiently improved now that it’s cheaper to shield the processor in it’s entirety rather than trying to rad harden the circuitry itself (much more expensive due to inability to use off the shelf parts & limits the ability to use newer tech)? If I recall correctly this was one of the areas being explored by the mars drone although not sure if Mars surface radiation concerns are different…

Aren't high energy space particles a pain in a way that the more shielding you have, the more secondary radiation you generate?
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